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Background & Aims: Lynch Syndrome, a hereditary disorder characterized by germline mutations in mismatch repair (MMR) genes, is a major contributor to colorectal cancers. It has also been identified in endometrial cancer. Despite the established role of MMR deficiency in tumorigenesis, the specific genomic alterations driving Lynch syndrome-associated endometrial cancer, and their overlap with colorectal cancer, remain incompletely understood. This study aims to fill this gap by performing a detailed comparative analysis of germline and somatic mutations in endometrial cancer within the context of Lynch syndrome. Methods: We conducted whole exome sequencing on matched germline and somatic DNA from 13 patients diagnosed with Lynch syndrome-associated endometrial cancer. High-depth sequencing was performed, followed by rigorous bioinformatics analysis to identify and annotate variants, focusing on their potential pathogenicity and relevance to both endometrial and colorectal cancer. Results: Our analysis revealed 1,118 germline and 14,051 somatic variants, with 493 variants common to both. Recurrent pathogenic mutations in MLH1, MSH2, and MSH6 were confirmed, highlighting their critical role in Lynch syndrome. Notably, frequent somatic mutations in the PIK3CA and PTEN genes were identified, implicating the PI3K/AKT/mTOR pathway as a key oncogenic driver in these cancers. Additionally, novel somatic mutations in genes related to the extracellular matrix such as FBN1 and SPARC were uncovered, suggesting a possible unique role in endometrial tumor progression. Conclusions: This study provides new insights into the molecular basis of Lynch syndrome-associated endometrial cancer, emphasizing the overlap in oncogenic pathways with colorectal cancer. The discovery of shared and unique genetic mutations highlights the importance of developing combined treatment strategies and suggests that targeting these specific mutations could improve therapy for patients with Lynch syndromeassociated cancers. [ABSTRACT FROM AUTHOR]

Lynch syndrome, a hereditary cancer susceptibility syndrome, arises from pathogenic mutations in mismatch repair genes. This syndrome is strongly linked to colorectal and endometrial cancers, as well as an elevated risk for other cancers such as gastric, ovarian, renal pelvis/ureter, and prostate. Notably, Lynch syndrome is rarely associated with cholangiocarcinoma (CCA). In this case study, we present a unique instance of Lynch syndrome-related CCA resulting from a singular MSH6 mutation. Notably, our findings reveal discrepancies between immunohistochemistry (IHC) and microsatellite stability results compared to genetic testing outcomes. This discrepancy underscores the limitations of solely relying on IHC analysis and microsatellite stability testing for the detection of hereditary tumors, emphasizing the crucial role of genetic testing in such cases. This insight enhances our comprehension of the mechanisms involved in cancer development and underscores the significance of thorough analysis integrating immunohistochemistry and genetic testing for diagnosing Lynch syndrome-related cancers. [ABSTRACT FROM AUTHOR]

5-aminosalicylic acid (5-ASA) is a first-line treatment for maintaining colitis remission. It is a highly effective, safe, and well-tolerated drug with anti-inflammatory and chemo-preventive properties. While patients with primary sclerosing cholangitis (PSC) with concomitant ulcerative colitis are treated with 5-ASA, the molecular mechanisms underlying the drug's chemo-preventive effects are not entirely understood. We previously reported that bile acids and lipopolysaccharide-induced miR-155 expression was associated with downregulating mismatch repair (MMR) proteins in CACO-2 cell lines. Therefore, in this investigation, a set of in vitro functional studies was performed to show the possible mechanisms behind the epigenetic relationship between miR-155 and 5-ASA's prevention of high microsatellite instability (MSI-H). In transient transfection with miR-155Mimic, which behaves like endogenous miRNA, we confirmed the relationships between miR-155 and its target MMR in three human intestinal epithelial cell lines: CACO-2, NCM460D and HT-29. We have shown, for the first time, that 5-ASA modulates MLH1, MSH2, MSH6 in miR-155 transfected cells. These findings underline that chemoprotective 5-ASA therapy can effectively attenuate the expression of miR-155 and potentially prevent a development of MSI-H in a subset of colorectal cancers associated with PSC. Key Points: miR-155 may be a key regulator of tumorigenesis in the ascending colon of patients with PSC. 5-ASA therapy can effectively attenuate the expression of miR-155 involved in the pathogenesis of high microsatellite instability. [ABSTRACT FROM AUTHOR]

Background: Up to 70% of suspected Lynch syndrome patients harboring MMR deficient tumors lack identifiable germline pathogenic variants in MMR genes, being referred to as Lynch‐like syndrome (LLS). Previous studies have reported biallelic somatic MMR inactivation in a variable range of LLS‐associated tumors. Moreover, translating tumor testing results into patient management remains controversial. Our aim is to assess the challenges associated with the implementation of tumoral MMR gene testing in routine workflows. Methods: Here, we present the clinical characterization of 229 LLS patients. MMR gene testing was performed in 39 available tumors, and results were analyzed using two variant allele frequency (VAF) thresholds (≥5% and ≥10%). Results and Discussion: More biallelic somatic events were identified at VAF ≥ 5% than ≥10% (35.9% vs. 25.6%), although the rate of nonconcordant results regarding immunohistochemical pattern increased (30.8% vs. 20.5%). Interpretation difficulties question the current utility of the identification of MMR somatic hits in the diagnostic algorithm of suspected LS cases. [ABSTRACT FROM AUTHOR]

Abstract Background Up to 70% of suspected Lynch syndrome patients harboring MMR deficient tumors lack identifiable germline pathogenic variants in MMR genes, being referred to as Lynch‐like syndrome (LLS). Previous studies have reported biallelic somatic MMR inactivation in a variable range of LLS‐associated tumors. Moreover, translating tumor testing results into patient management remains controversial. Our aim is to assess the challenges associated with the implementation of tumoral MMR gene testing in routine workflows. Methods Here, we present the clinical characterization of 229 LLS patients. MMR gene testing was performed in 39 available tumors, and results were analyzed using two variant allele frequency (VAF) thresholds (≥5% and ≥10%). Results and Discussion More biallelic somatic events were identified at VAF ≥ 5% than ≥10% (35.9% vs. 25.6%), although the rate of nonconcordant results regarding immunohistochemical pattern increased (30.8% vs. 20.5%). Interpretation difficulties question the current utility of the identification of MMR somatic hits in the diagnostic algorithm of suspected LS cases.

Abstract Background The DNA in each cell in our body is constantly in danger of becoming damaged. Most DNA damage gets repaired straight away via many different proteins encoded by DNA—repair genes. MSH3 and MSH6 are pivotal DNA repair genes maintaining human genome integrity. Dysregulated expression of such genes has its implications resulting in developing of adverse reactions in cancer breast patients receiving taxanes. Cancer chemotherapy with some of taxane class of agents are associated with significant neurotoxicity, arthralgias and myalgias that may offset the therapeutic benefits of taxane use. Our aim is to identify gene expression pattern of MSH3 and MSH6 DNA mismatch repair genes in female breast cancer patients who develop adverse reactions to taxane-based therapy. One hundred and five patients with histologically proven breast cancer who received paclitaxel (PTX) as a single agent or combination therapy have been enrolled along with a group of 50 females with benign breast lesions serving as controls.Gene expression studies of mismatch repair genes (MMR) genes; MSH3 and MSH6; have been performed by real-time PCR. Patients were divided into groups according to the determined type/grade of PTX-based toxicity and fold changes of both genes were estimated. Results In the present work both MMR genes showed significantly lower expression in all the studied patients compared to benign cases as a control group. Toxicity findings were encountered in 75.2% of the studied patient cohort. The most common observed type of toxicity was peripheral neuropathy (PN), 58.1% of the studied patients. Both MSH3 and MSH6 genes were significantly down-regulated in the presence of high grade PN toxicity ≥ 2 (p = 0.034 and 0.01); diarrhea toxicity (p = 0.02 and 0.008); dyspnea (p = 0.01 and 0.016) respectively and bone pain (p = 0.024 for MSH6 only). Conclusion Dysregulated expression of MMR GENES [MSH3and MSH6] can be implicated in paclitaxel—induced toxicity experienced by some cancer breast patients.

Background: Subjects having Lynch syndrome do not show any distinct features apart from increased evidence of adenocarcinomas. As Lynch syndrome lacks any distinguished phenotypic feature, its diagnosis is challenging. Aims: The present study aimed to reveal the clinical presentation of Lynch syndrome and to assess if there is a successive decrease in the age of presentation with the generations. The study also aimed to assess if MLH1 mutation acts as a founder mutation for Lynch syndrome and if genetic alteration constitutes the clinical presentation of the disease. Materials and Methods: The Study included 12 families (40 subjects) having colorectal cancer under the age of 50 years or at least two relatives (first/second degree) who had a history of colorectal cancer at any age The TaqMan SNP genotyping assay was done in all the subjects and controls to assess the missense mutation in gees (MSH1, MLH2, MSH6, and PSM 2). The collected data were statistically analyzed. Results: Only 1 individual among the controls was carrying MLH1 mutation. Concerning the haplotype analysis, in the selected 12 families a region of genes in a range of 1-3 Mb was characterized with crossovers present. A shared haplotype was observed between upstream as well as downstream haplotypes in the assessed families. This sharing of haplotype implied that in different families compared, there are mutation events different from the recombination, occurring in the markers of these families. The NREM model was applied along with the COX-R model and these models showed that there was a constant decrease in the consecutive generation regarding the mean age of first-time cancer diagnosis. This decrease in the present study was shown to be by 2.2 years in consecutive generations in the whole study cohort. Conclusion: The results of the present study conclude that the clinical presentation of Lynch syndrome depends on the gene mutated, environmental factors, and personal factors (age and gender). Although the Lynch syndrome incidence is lower globally, with the recent advances in diagnostic criteria and surveillance, more cases with different clinical pictures are identified recently. There was also seen a decrease in the age of detection of the first cancer in Lynch syndrome in successive generations. [ABSTRACT FROM AUTHOR]

Background: The DNA in each cell in our body is constantly in danger of becoming damaged. Most DNA damage gets repaired straight away via many different proteins encoded by DNA—repair genes. MSH3 and MSH6 are pivotal DNA repair genes maintaining human genome integrity. Dysregulated expression of such genes has its implications resulting in developing of adverse reactions in cancer breast patients receiving taxanes. Cancer chemotherapy with some of taxane class of agents are associated with significant neurotoxicity, arthralgias and myalgias that may offset the therapeutic benefits of taxane use. Our aim is to identify gene expression pattern of MSH3 and MSH6 DNA mismatch repair genes in female breast cancer patients who develop adverse reactions to taxane-based therapy. One hundred and five patients with histologically proven breast cancer who received paclitaxel (PTX) as a single agent or combination therapy have been enrolled along with a group of 50 females with benign breast lesions serving as controls.Gene expression studies of mismatch repair genes (MMR) genes; MSH3 and MSH6; have been performed by real-time PCR. Patients were divided into groups according to the determined type/grade of PTX-based toxicity and fold changes of both genes were estimated. Results: In the present work both MMR genes showed significantly lower expression in all the studied patients compared to benign cases as a control group. Toxicity findings were encountered in 75.2% of the studied patient cohort. The most common observed type of toxicity was peripheral neuropathy (PN), 58.1% of the studied patients. Both MSH3 and MSH6 genes were significantly down-regulated in the presence of high grade PN toxicity ≥ 2 (p = 0.034 and 0.01); diarrhea toxicity (p = 0.02 and 0.008); dyspnea (p = 0.01 and 0.016) respectively and bone pain (p = 0.024 for MSH6 only). Conclusion: Dysregulated expression of MMR GENES [MSH3and MSH6] can be implicated in paclitaxel—induced toxicity experienced by some cancer breast patients. [ABSTRACT FROM AUTHOR]

Introduction In Lynch syndrome, urothelial cancer is the third most common cancer, following colorectal and endometrial cancers. Little is known, however, about the efficacy of immune checkpoint inhibitors in the treatment of metastatic urothelial cancer in Lynch syndrome. Case presentation A 49‐year‐old patient with metastatic urothelial cancer underwent pembrolizumab therapy after platinum‐containing chemotherapy. The efficacy of the pembrolizumab therapy was good. Her lung and bone metastatic lesions disappeared in imaging studies and her back pain decreased dramatically. Pathogenic mutations of MSH2 and BRCA2 were found in the DNA extracted from her tumor, and subsequent genetic analysis confirmed the germline pathogenic variant of MSH2. As such, this case was genetically diagnosed as Lynch syndrome. Conclusion We report metastatic urothelial cancer in a patient with Lynch syndrome who demonstrated a radiological complete response to pembrolizumab therapy. Accurate genetic diagnosis can provide useful information to both the patient and their relatives.

The risks of development of colorectal and endometrial cancers in individuals with Lynch syndrome (LS) are well known and have been widely studied. In recent years, the potential association of other malignancies, including prostate cancer, with LS has been considered. Decision-making regarding screening for prostate cancer in the generalized population can be complicated; accounting for the possibility of a higher risk of cancer conferred by a potential genetic predisposition confounds the creation of salient guidelines even further. Although tissue-agnostic treatment approvals have been granted to several immune checkpoint inhibitors (ICIs) for their use in the treatment of subsets of patients whose tumors exhibit high levels of microsatellite instability or high tumor mutational burden, a paucity of data exists regarding the use of ICIs in the first line treatment of patients with locally advanced prostate cancer harboring these features. A significant reduction in tumor volume in response to the combination of immune checkpoint inhibition and androgen deprivation therapy is described in this report of a male with Muir-Torre syndrome who was found to have locally advanced adenocarcinoma of the prostate. While anecdotal, the anti-tumor activity of this combination of therapy is notable and calls attention to the importance of considering further investigation of the use of immune checkpoint blockade as a primary therapeutic option in patients with localized prostate cancer. [ABSTRACT FROM AUTHOR]

Introduction: The purpose of this research was to explore the correlation between Gleason score and pattern and the expression of the MLH1, MSH2, MDC1, TP53BP1 proteins in prostate cancer (PC). Prostate cancer development is related to errors in DNA, among others double-strand breaks (DSB) and changes in the base sequence of the DNA. These errors should be repaired through mismatch (MMR) or DSB repair proteins such as MSH2, MLH1, MDC1 and TP53BP1. Material and methods: A total of 500 prostate cancer specimens were recruited in this study. From among all gathered specimens the 52 most suitable cases were selected. The expression of examined proteins was detected by immunohistochemistry, and its correlation with the Gleason score and pattern were further analyzed through standard statistical algorithms. Results: The results show a significant correlation between Gleason pattern and the nuclear expression of the MSH2 protein and the cytoplasmic expression of the MLH1 protein. Gleason score significantly correlates with the nuclear and the cytoplasmic expression of the MSH2 protein and the cytoplasmic expression of the MDC1 protein. There is no correlation between the nuclear or cytoplasmic expression of the TP53BP1 protein and Gleason pattern or score. Conclusions: Our study suggests that the aberration in the MMR repair mechanism may be significantly more important regarding the grading among PC cells in comparison to the impact of alterations in the DSB repair mechanism. The lack of correlation between expression of the TP53BP1 protein and Gleason pattern and Gleason score suggests that the radiation resistance of PC is independent of alterations connected with TP53BP1. [ABSTRACT FROM AUTHOR]

Synchronous colorectal carcinoma is having more than 1 primary carcinoma detected in a single patient at the same time or within 6 months of tumor diagnosis. Metachronous colorectal carcinoma is the presence of more than 1 primary carcinoma detected consecutively in a single person after a set time interval. Patients with Lynch syndrome and Muir-Torre syndrome (a subset of Lynch syndrome) inherit a germline mutation in 1 of the mismatch repair (MMR) genes. Patients with synchronous colorectal carcinoma have a higher proportion of MMR-mutated cancers than patients with solitary colorectal carcinoma. Most studies in the literature indicate that patients with synchronous colorectal cancers typically have only 2 carcinomas. However, there have been reports of a single patient having up to 6 synchronous carcinomas in the large intestine. This report discusses a patient with 9 simultaneous colorectal cancers at the initial diagnosis, along with a history of bladder cancer, sebaceous adenoma, and duodenal adenoma, associated with a germline mutS homolog 2 (MSH2) mutation. Additionally, the report explores various aspects of having synchronous colorectal cancers. More studies are needed to clarify the clinicopathologic and molecular landscape of these rare tumors and identify the best management and treatment strategies for these patients. [ABSTRACT FROM AUTHOR]

The risks of development of colorectal and endometrial cancers in individuals with Lynch syndrome (LS) are well known and have been widely studied. In recent years, the potential association of other malignancies, including prostate cancer, with LS has been considered. Decision-making regarding screening for prostate cancer in the generalized population can be complicated; accounting for the possibility of a higher risk of cancer conferred by a potential genetic predisposition confounds the creation of salient guidelines even further. Although tissue-agnostic treatment approvals have been granted to several immune checkpoint inhibitors (ICIs) for their use in the treatment of subsets of patients whose tumors exhibit high levels of microsatellite instability or high tumor mutational burden, a paucity of data exists regarding the use of ICIs in the first line treatment of patients with locally advanced prostate cancer harboring these features. A significant reduction in tumor volume in response to the combination of immune checkpoint inhibition and androgen deprivation therapy is described in this report of a male with Muir-Torre syndrome who was found to have locally advanced adenocarcinoma of the prostate. While anecdotal, the anti-tumor activity of this combination of therapy is notable and calls attention to the importance of considering further investigation of the use of immune checkpoint blockade as a primary therapeutic option in patients with localized prostate cancer.

Synchronous colorectal carcinoma is having more than 1 primary carcinoma detected in a single patient at the same time or within 6 months of tumor diagnosis. Metachronous colorectal carcinoma is the presence of more than 1 primary carcinoma detected consecutively in a single person after a set time interval. Patients with Lynch syndrome and Muir-Torre syndrome (a subset of Lynch syndrome) inherit a germline mutation in 1 of the mismatch repair (MMR) genes. Patients with synchronous colorectal carcinoma have a higher proportion of MMR-mutated cancers than patients with solitary colorectal carcinoma. Most studies in the literature indicate that patients with synchronous colorectal cancers typically have only 2 carcinomas. However, there have been reports of a single patient having up to 6 synchronous carcinomas in the large intestine. This report discusses a patient with 9 simultaneous colorectal cancers at the initial diagnosis, along with a history of bladder cancer, sebaceous adenoma, and duodenal adenoma, associated with a germline mutS homolog 2 ( MSH2 ) mutation. Additionally, the report explores various aspects of having synchronous colorectal cancers. More studies are needed to clarify the clinicopathologic and molecular landscape of these rare tumors and identify the best management and treatment strategies for these patients., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Introduction: About 5% of endometrial cancers (ECs) are attributed to an inherited predisposition, for which Lynch syndrome (LS) accounts for the majority of cases. Women with LS have a 40–60% predicted lifetime risk of developing EC, in addition to a 40–80% lifetime risk of developing colorectal cancer and other cancers. In this population, the lifetime risk of developing ovarian cancer (OC) is 10–12%. Object: to compare the histopathological features of LS-associated EC and OC with sporadic cancers in order to evaluate whether there are differences in terms of age at diagnosis, site of occurrence in the uterus, histological type, stage at diagnosis, and tumor grading. Materials and methods: we compared data obtained from 96 patients with LS-associated gynecological cancers (82 with EC and 14 with OC) to a control group (CG) of 209 patients who developed sporadic EC, and a CG of 187 patients with sporadic OC. Results: The mean age at diagnosis of LS-associated EC and OC was much lower than in the control groups. In both groups with EC, the endometrioid histotype was the most frequently occurring histotype. However, among LS women there was a significantly higher incidence of clear cell tumors (11% versus 2.4% in the CG, p = 0.0001). Similar to the sporadic cancer cases, most of the LS-associated ECs presented at an early stage (89% of cases at FIGO I-II stage). In the LS group, the tumor frequently involved only the inner half of the endometrium (77% of cases, p < 0.01). In the LS group, 7.3% of ECs were localized to the lower uterine segment (LUS), whereas no cancer developed in the LUS in the CG. No serous OCs were diagnosed in the LS group (versus 45.5% in the CG, p = 0.0009). Most of the LS-associated OCs presented at an early stage (85% of cases at FIGO I-II stages, p < 0.01). Conclusion: LS-associated EC and OC seem to have peculiar features, occurring at a younger age and at an earlier stage. In LS, EC less frequently involves the outer half of the endometrium, with a more frequent occurrence in the LUS. The presence of clear cell EC was more frequently observed, whereas in OC, the predominant histotype was endometrioid. [ABSTRACT FROM AUTHOR]

Around 15–30% of colorectal cancers (CRC) develop from sessile serrated lesions (SSLs). After many years of indolent growth, SSLs can develop dysplasia and rapidly progress to CRC through events that are only partially understood. We studied molecular events at the very early stages of progression of SSLs via the MLH1‐proficient and deficient pathways to CRC. We collected a cohort of rare SSLs with a small focus (<10 mm) of dysplasia or cancer from the pathology archives of three hospitals. Whole‐exome sequencing was performed on DNA from nonprogressed and progressed components of each SSL. Putative somatic driver mutations were identified in known cancer genes that were differentially mutated in the progressed component. All analyses were stratified by MLH1 proficiency. Forty‐five lesions with a focus dysplasia or cancer were included, of which 22 (49%) were MLH1‐deficient. Lesions had a median diameter of 10 mm (interquartile range [IQR] 8–15), while the progressed component had a median diameter of 3.5 mm (IQR 1.75–4.75). Tumor mutational burden (TMB) was high in MLH1‐deficient lesions (23.9 mutations per MB) as compared to MLH1‐proficient lesions (6.3 mutations per MB). We identified 34 recurrently mutated genes in MLH1‐deficient lesions. Most prominently, ACVR2A and RNF43 were affected in 18/22 lesions, with mutations clustered in three hotspots. Most lesions with RNF43 mutations had concurrent mutations in ZNRF3. In MLH1‐proficient lesions APC (10/23 lesions) and TP53 (6/23 lesions) were recurrently mutated. Our results show that the mutational burden is exceptionally high even in the earliest MLH1‐deficient lesions. We demonstrate that hotspot mutations in ACVR2A and in the RNF43/ZNRF3 complex are extremely common in the early progression of SSLs along the MLH1‐deficient serrated pathway, while APC and TP53 mutations are early events in the the MLH1‐proficient pathway. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Abstract Background Lynch syndrome is caused by germline mutations in the mismatch repair genes and is characterised by a familial accumulation of colorectal and other cancers. Earlier identification of Lynch syndrome patients enables surveillance and might reduce the risk of cancer. It is important to explore whether today’s clinical care discovers patients with Lynch syndrome suitable for surveillance in time. This study aimed to describe what led to a diagnosis of Lynch syndrome in the cohort referred to the Hereditary Gastrointestinal Cancer Unit, Karolinska University Hospital, Solna, Sweden for gastrointestinal surveillance. Methods This was a descriptive study. Data from 1975 to 2018 were collected and compiled as a database. Age at diagnosis was calculated from the date when a pathogenic MMR gene mutation was confirmed, from the period June 1994–September 2018. Data were collected from patient protocols prospectively during patient consultations and medical records retrospectively. Criteria for inclusion were registration at the outpatient clinic and a confirmed mismatch repair gene mutation. Results A total of 305 patients were eligible for inclusion. Three major reasons for diagnosis were identified: 1. Predictive testing of a previously known mutation in the family (62%, mean age 37), 2. A family history of Lynch associated tumours (9%, mean age 37), 3. A diagnosis of cancer (29%, mean age 51). The proportion diagnosed due to cancer has not changed over time. Conclusion A high proportion of patients (29%) were identified with Lynch syndrome after they had been diagnosed with an associated cancer, which suggests that there is significant room for improvement in the diagnosis of patients with Lynch syndrome before cancer develops.

Abstract Background The most frequently identified strong cancer predisposition mutations for colorectal cancer (CRC) are those in the mismatch repair (MMR) genes in Lynch syndrome. Laboratory diagnostics include testing tumors for immunohistochemical staining (IHC) of the Lynch syndrome-associated DNA MMR proteins and/or for microsatellite instability (MSI) followed by sequencing or other techniques, such as denaturing high performance liquid chromatography (DHPLC), to identify the mutation. Methods In an ongoing project focusing on finding Mendelian cancer syndromes we applied whole-exome/whole-genome sequencing (WES/WGS) to 19 CRC families. Results Three families were identified with a pathogenic/likely pathogenic germline variant in a MMR gene that had previously tested negative in DHPLC gene variant screening. All families had a history of CRC in several family members across multiple generations. Tumor analysis showed loss of the MMR protein IHC staining corresponding to the mutated genes, as well as MSI. In family A, a structural variant, a duplication of exons 4 to 13, was identified in MLH1. The duplication was predicted to lead to a frameshift at amino acid 520 and a premature stop codon at amino acid 539. In family B, a 1 base pair deletion was found in MLH1, resulting in a frameshift and a stop codon at amino acid 491. In family C, we identified a splice site variant in MSH2, which was predicted to lead loss of a splice donor site. Conclusions We identified altogether three pathogenic/likely pathogenic variants in the MMR genes in three of the 19 sequenced families. The MLH1 variants, a duplication of exons 4 to 13 and a frameshift variant, were novel, based on the InSiGHT and ClinVar databases; the MSH2 splice site variant was reported by a single submitter in ClinVar. As a variant class, duplications have rarely been reported in the MMR gene literature, particularly those covering several exons.

Lynch syndrome (LS) is an inherited genetic condition associated with increased predisposition to colorectal cancer (CRC) and other tumors and is caused by germline mutations in Mismatch Repair (MMR) or EPCAM genes. The identification of LS carriers is currently based on germline testing of subjects with MMR-deficient (dMMR) tumors or fulfilling clinical criteria, but the most efficient strategies to select patients who should be offered genetic testing are yet not well defined. In order to assess the most suitable selection mode to identify LS-related CRC patients, we retrospectively collected and analyzed all clinical and molecular information of 854 CRC patients, recruited from 2013 to 2021 at the University Hospital Policlinico "P. Giaccone" of Palermo (Italy), 100 of which were selected based on revised Bethesda guidelines, Amsterdam criteria II, or tissue MMR deficiency, and genetically tested for germline variants in LS-susceptibility genes. Our study showed that 32 out of 100 CRC patients harbored germline likely pathogenic/pathogenic variants in MMR genes. The analysis of tissue microsatellite instability (MSI) status according to the revised Bethesda guidelines has been to be the best selection approach. However, using different selection approaches as complementary strategies is useful to identify LS carriers, reducing underdiagnosis of this syndrome. [ABSTRACT FROM AUTHOR]

Lynch syndrome (LS) is an inherited genetic condition associated with increased predisposition to colorectal cancer (CRC) and other tumors and is caused by germline mutations in Mismatch Repair (MMR) or EPCAM genes. The identification of LS carriers is currently based on germline testing of subjects with MMR-deficient (dMMR) tumors or fulfilling clinical criteria, but the most efficient strategies to select patients who should be offered genetic testing are yet not well defined. In order to assess the most suitable selection mode to identify LS-related CRC patients, we retrospectively collected and analyzed all clinical and molecular information of 854 CRC patients, recruited from 2013 to 2021 at the University Hospital Policlinico “P. Giaccone” of Palermo (Italy), 100 of which were selected based on revised Bethesda guidelines, Amsterdam criteria II, or tissue MMR deficiency, and genetically tested for germline variants in LS-susceptibility genes. Our study showed that 32 out of 100 CRC patients harbored germline likely pathogenic/pathogenic variants in MMR genes. The analysis of tissue microsatellite instability (MSI) status according to the revised Bethesda guidelines has been to be the best selection approach. However, using different selection approaches as complementary strategies is useful to identify LS carriers, reducing underdiagnosis of this syndrome.

Lynch syndrome, a hereditary cancer susceptibility syndrome, arises from pathogenic mutations in mismatch repair genes. This syndrome is strongly linked to colorectal and endometrial cancers, as well as an elevated risk for other cancers such as gastric, ovarian, renal pelvis/ureter, and prostate. Notably, Lynch syndrome is rarely associated with cholangiocarcinoma (CCA). In this case study, we present a unique instance of Lynch syndrome-related CCA resulting from a singular MSH6 mutation. Notably, our findings reveal discrepancies between immunohistochemistry (IHC) and microsatellite stability results compared to genetic testing outcomes. This discrepancy underscores the limitations of solely relying on IHC analysis and microsatellite stability testing for the detection of hereditary tumors, emphasizing the crucial role of genetic testing in such cases. This insight enhances our comprehension of the mechanisms involved in cancer development and underscores the significance of thorough analysis integrating immunohistochemistry and genetic testing for diagnosing Lynch syndrome-related cancers., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhang, Ma, Li, Chen, Song and Wang.)

Familial non-medullary thyroid cancer (FNMTC) is a form of endocrine malignancy exhibiting an autosomal dominant mode of inheritance with largely unknown germline molecular mechanism. Hereditary nonpolyposis colorectal cancer syndrome (HNPCC) is another hereditary autosomal dominant cancer syndrome which, if proven to be caused by germline mutations in mismatch repair genes (MMR)—MLHL, MSH2, MSH6, PMS2, and EPCAM—is called Lynch syndrome (LS). LS results in hereditary predisposition to a number of cancers, especially colorectal and endometrial cancers. Tumors in LS are characterized by microsatellite instability (MSI) and/or loss of MMR protein expression in immunohistochemistry (IHC). MSI is a rare event in thyroid cancer (TC), although it is known to occur in up to 2.5% of sporadic follicular TC cases. There are limited data on the role of germline MMR variants FNMTC. The goal of this study was to analyze the potential clinical and molecular association between HNPCC and FNMTC. We performed a cohort study analyzing the demographic, clinical, and pathologic data of 43 kindreds encompassing 383 participants (104 affected, 279 unaffected), aged 43.5 [7-99] years with FNMTC, and performed high-throughput whole-exome sequencing (WES) of peripheral blood DNA samples of selected 168 participants (54 affected by FNMTC and 114 unaffected). Total affected by thyroid cancer members per family ranged between 2 and 9 patients. FNMTC was more prevalent in women (68.3%) and characterized by a median tumor size of 1.0 [0.2-5.0] cm, multifocal growth in 44%, and gross extrathyroidal extension in 11.3%. Central neck lymph node metastases were found in 40.3% of patients at presentation, 12.9% presented with lateral neck lymph node metastases, and none had distant metastases. Family history screening revealed one Caucasian family meeting the clinical criteria for FNMTC and HNPCC, with five members affected by FNMTC and at least eight individuals reportedly unaffected by HNPCC-associated tumors. In addition, two family members were affected by melanoma. Genome Analysis Tool Kit (GATK) pipeline was used in variant analysis. Among 168 sequenced participants, a heterozygous missense variant in the MSH2 gene (rs373226409; c.2120G>A; p.Cys707Tyr) was detected exclusively in FNMTC- HNPCC- kindred. In this family, the sequencing was performed in one member affected by FNMTC, HPNCC-associated tumors and melanoma, one member affected solely by HNPCC-associated tumor, and one member with FNMTC only, as well as seven unaffected family members. The variant was present in all three affected adults, and in two unaffected children of the affected member, under the age of 18 years, and was absent in non-affected adults. This variant is predicted to be damaging/pathogenic in 17/20 in-silico models. However, immunostaining performed on the thyroid tumor tissue of two affected by FNMTC family members revealed intact nuclear expression of MSH2, and microsatellite stable status in both tumors that were tested. Although the MSH2 p.Cys707Tyr variant is rare with a minor allele frequency (MAF) of 0.00006 in Caucasians; it is more common in the South Asian population at 0.003 MAF. Therefore, the MSH2 variant observed in this family is unlikely to be an etiologic factor of thyroid cancer and a common genetic association between FNMTC and HNPCC has not yet been identified. This is the first report known to us on the co-occurrence of FNMTC and HNPCC. The co-occurrence of FNMTC and HNPCC-associated tumors is a rare event and although presented in a single family in our large FNMTC cohort, a common genetic background between the two comorbidities could not be established.

Familial non-medullary thyroid cancer (FNMTC) is a form of endocrine malignancy exhibiting an autosomal dominant mode of inheritance with largely unknown germline molecular mechanism. Hereditary nonpolyposis colorectal cancer syndrome (HNPCC) is another hereditary autosomal dominant cancer syndrome which, if proven to be caused by germline mutations in mismatch repair genes (MMR)— MLHL , MSH2 , MSH6 , PMS2 , and EPCAM —is called Lynch syndrome (LS). LS results in hereditary predisposition to a number of cancers, especially colorectal and endometrial cancers. Tumors in LS are characterized by microsatellite instability (MSI) and/or loss of MMR protein expression in immunohistochemistry (IHC). MSI is a rare event in thyroid cancer (TC), although it is known to occur in up to 2.5% of sporadic follicular TC cases. There are limited data on the role of germline MMR variants FNMTC. The goal of this study was to analyze the potential clinical and molecular association between HNPCC and FNMTC. We performed a cohort study analyzing the demographic, clinical, and pathologic data of 43 kindreds encompassing 383 participants (104 affected, 279 unaffected), aged 43.5 [7-99] years with FNMTC, and performed high-throughput whole-exome sequencing (WES) of peripheral blood DNA samples of selected 168 participants (54 affected by FNMTC and 114 unaffected). Total affected by thyroid cancer members per family ranged between 2 and 9 patients. FNMTC was more prevalent in women (68.3%) and characterized by a median tumor size of 1.0 [0.2-5.0] cm, multifocal growth in 44%, and gross extrathyroidal extension in 11.3%. Central neck lymph node metastases were found in 40.3% of patients at presentation, 12.9% presented with lateral neck lymph node metastases, and none had distant metastases. Family history screening revealed one Caucasian family meeting the clinical criteria for FNMTC and HNPCC, with five members affected by FNMTC and at least eight individuals reportedly unaffected by HNPCC-associated tumors. In addition, two family members were affected by melanoma. Genome Analysis Tool Kit (GATK) pipeline was used in variant analysis. Among 168 sequenced participants, a heterozygous missense variant in the MSH2 gene (rs373226409; c.2120G>A; p.Cys707Tyr) was detected exclusively in FNMTC- HNPCC- kindred. In this family, the sequencing was performed in one member affected by FNMTC, HPNCC-associated tumors and melanoma, one member affected solely by HNPCC-associated tumor, and one member with FNMTC only, as well as seven unaffected family members. The variant was present in all three affected adults, and in two unaffected children of the affected member, under the age of 18 years, and was absent in non-affected adults. This variant is predicted to be damaging/pathogenic in 17/20 in-silico models. However, immunostaining performed on the thyroid tumor tissue of two affected by FNMTC family members revealed intact nuclear expression of MSH2 , and microsatellite stable status in both tumors that were tested. Although the MSH2 p.Cys707Tyr variant is rare with a minor allele frequency (MAF) of 0.00006 in Caucasians; it is more common in the South Asian population at 0.003 MAF. Therefore, the MSH2 variant observed in this family is unlikely to be an etiologic factor of thyroid cancer and a common genetic association between FNMTC and HNPCC has not yet been identified. This is the first report known to us on the co-occurrence of FNMTC and HNPCC. The co-occurrence of FNMTC and HNPCC-associated tumors is a rare event and although presented in a single family in our large FNMTC cohort, a common genetic background between the two comorbidities could not be established. [ABSTRACT FROM AUTHOR]

Introduction The purpose of this research was to explore the correlation between Gleason score and pattern and the expression of the MLH1, MSH2, MDC1, TP53BP1 proteins in prostate cancer (PC). Prostate cancer development is related to errors in DNA, among others double-strand breaks (DSB) and changes in the base sequence of the DNA. These errors should be repaired through mismatch (MMR) or DSB repair proteins such as MSH2, MLH1, MDC1 and TP53BP1. Material and methods A total of 500 prostate cancer specimens were recruited in this study. From among all gathered specimens the 52 most suitable cases were selected. The expression of examined proteins was detected by immunohistochemistry, and its correlation with the Gleason score and pattern were further analyzed through standard statistical algorithms. Results The results show a significant correlation between Gleason pattern and the nuclear expression of the MSH2 protein and the cytoplasmic expression of the MLH1 protein. Gleason score significantly correlates with the nuclear and the cytoplasmic expression of the MSH2 protein and the cyto­plasmic expression of the MDC1 protein. There is no correlation between the nuclear or cytoplasmic expression of the TP53BP1 protein and Gleason pattern or score. Conclusions Our study suggests that the aberration in the MMR repair mechanism may be significantly more important regarding the grading among PC cells in comparison to the impact of alterations in the DSB repair mechanism. The lack of correlation between expression of the TP53BP1 protein and Gleason pattern and Gleason score suggests that the radiation resistance of PC is independent of alterations connected with TP53BP1.

Abstract Immunohistochemistry (IHC) for mismatch repair (MMR) proteins is used to identify MMR status: being diffusely positive (intact/retained nuclear staining) or showing loss of nuclear tumour staining (MMR protein deficient). Four colonic adenocarcinomas and a gastric adenocarcinoma with associated dysplasia that displayed heterogenous IHC staining patterns in at least one of the four MMR proteins were characterised by next‐generation sequencing (NGS). In order to examine a potential molecular mechanism for these staining patterns, the respective areas were macrodissected, analysed for microsatellite instability (MSI) and investigated by NGS and multiplex ligation‐dependent probe amplification (MLPA) analysis of MLH1, MSH2, MSH6 and PMS2 genes, including MLH1 methylation analysis. One colonic adenocarcinoma showed heterogenous MSH6 IHC staining and molecular analysis demonstrated increasing allelic burden of two MSH6 frameshift variants (c.3261delC and c.3261dupC) in areas with MSH6 protein loss compared to areas where MSH6 was retained. Two colonic adenocarcinomas with heterogenous MLH1 staining showed no differences in sequence variants. In one of these cases, however, MLH1 was hypermethylated in the area of MLH1 loss. Another colon carcinoma with heterogenous PMS2 staining (but with retained MSH6) showed both MSH6 c.3261dupC and 3260_3261dupCC where PMS2 protein was lost and only c.3261dupC where PMS2 was retained. The gastric carcinoma showed complete loss of MSH6 in dysplastic foci, while the underlying invasive carcinoma showed retention of MSH6. Both these areas, however, were MSI‐high and showed the same MSH6 variant: c.3261delC. The gastric dysplasia additionally showed MSH6 c.3261dupC. In four of the five cases where MMR protein was lost, these areas were MSI‐high. Heterogenous MMR IHC (focal and/or zonal within the same tumour or between invasive and dysplastic preinvasive areas) is not always due to artefact and is invariably related to MSI‐high status in the areas of loss. An interesting aspect to this study is the presence of MSH6 somatic mutations irrespective of whether MSH6 IHC staining was intact or lost.

Background: Lynch syndrome is caused by germline mutations in the mismatch repair genes and is characterised by a familial accumulation of colorectal and other cancers. Earlier identification of Lynch syndrome patients enables surveillance and might reduce the risk of cancer. It is important to explore whether today's clinical care discovers patients with Lynch syndrome suitable for surveillance in time. This study aimed to describe what led to a diagnosis of Lynch syndrome in the cohort referred to the Hereditary Gastrointestinal Cancer Unit, Karolinska University Hospital, Solna, Sweden for gastrointestinal surveillance. Methods: This was a descriptive study. Data from 1975 to 2018 were collected and compiled as a database. Age at diagnosis was calculated from the date when a pathogenic MMR gene mutation was confirmed, from the period June 1994–September 2018. Data were collected from patient protocols prospectively during patient consultations and medical records retrospectively. Criteria for inclusion were registration at the outpatient clinic and a confirmed mismatch repair gene mutation. Results: A total of 305 patients were eligible for inclusion. Three major reasons for diagnosis were identified: 1. Predictive testing of a previously known mutation in the family (62%, mean age 37), 2. A family history of Lynch associated tumours (9%, mean age 37), 3. A diagnosis of cancer (29%, mean age 51). The proportion diagnosed due to cancer has not changed over time. Conclusion: A high proportion of patients (29%) were identified with Lynch syndrome after they had been diagnosed with an associated cancer, which suggests that there is significant room for improvement in the diagnosis of patients with Lynch syndrome before cancer develops. [ABSTRACT FROM AUTHOR]

Background: The most frequently identified strong cancer predisposition mutations for colorectal cancer (CRC) are those in the mismatch repair (MMR) genes in Lynch syndrome. Laboratory diagnostics include testing tumors for immunohistochemical staining (IHC) of the Lynch syndrome-associated DNA MMR proteins and/or for microsatellite instability (MSI) followed by sequencing or other techniques, such as denaturing high performance liquid chromatography (DHPLC), to identify the mutation. Methods: In an ongoing project focusing on finding Mendelian cancer syndromes we applied whole-exome/whole-genome sequencing (WES/WGS) to 19 CRC families. Results: Three families were identified with a pathogenic/likely pathogenic germline variant in a MMR gene that had previously tested negative in DHPLC gene variant screening. All families had a history of CRC in several family members across multiple generations. Tumor analysis showed loss of the MMR protein IHC staining corresponding to the mutated genes, as well as MSI. In family A, a structural variant, a duplication of exons 4 to 13, was identified in MLH1. The duplication was predicted to lead to a frameshift at amino acid 520 and a premature stop codon at amino acid 539. In family B, a 1 base pair deletion was found in MLH1, resulting in a frameshift and a stop codon at amino acid 491. In family C, we identified a splice site variant in MSH2, which was predicted to lead loss of a splice donor site. Conclusions: We identified altogether three pathogenic/likely pathogenic variants in the MMR genes in three of the 19 sequenced families. The MLH1 variants, a duplication of exons 4 to 13 and a frameshift variant, were novel, based on the InSiGHT and ClinVar databases; the MSH2 splice site variant was reported by a single submitter in ClinVar. As a variant class, duplications have rarely been reported in the MMR gene literature, particularly those covering several exons. [ABSTRACT FROM AUTHOR]

Functional assays that assess mRNA splicing can be used in interpretation of the clinical significance of sequence variants, including the Lynch syndrome-associated mismatch repair (MMR) genes. The purpose of this study was to investigate the contribution of splicing assay data to the classification of MMR gene sequence variants. We assayed mRNA splicing for 24 sequence variants in MLH1, MSH2, and MSH6, including 12 missense variants that were also assessed using a cell-free in vitro MMR activity (CIMRA) assay. Multifactorial likelihood analysis was conducted for each variant, combining CIMRA outputs and clinical data where available. We collated these results with existing public data to provide a dataset of splicing assay results for a total of 671 MMR gene sequence variants (328 missense/in-frame indel), and published and unpublished repair activity measurements for 154 of these variants. There were 241 variants for which a splicing aberration was detected: 92 complete impact, 33 incomplete impact, and 116 where it was not possible to determine complete versus incomplete splicing impact. Splicing results mostly aided in the interpretation of intronic (72%) and silent (92%) variants and were the least useful for missense substitutions/in-frame indels (10%). MMR protein functional activity assays were more useful in the analysis of these exonic variants but by design they were not able to detect clinically important splicing aberrations identified by parallel mRNA assays. The development of high throughput assays that can quantitatively assess impact on mRNA transcript expression and protein function in parallel will streamline classification of MMR gene sequence variants.

Lynch syndrome (LS) is a hereditary cancer predisposition syndrome primarily defined by increased risk for colorectal and uterine cancers. Individuals with germline pathogenic variants in the mismatch repair (MMR) genes (MLH1, MSH2/EPCAM, MSH6, and PMS2) are diagnosed with LS and recommended high‐risk screening protocols to increase prevention and early detection of LS‐related cancers. Tumor testing can help identify those at high risk for LS, but sometimes creates uncertainty with discordant screening and germline results, or unexplained mismatch repair deficiency (UMMRD). Somatic testing for MMR genes may help resolve UMMRD, potentially clarifying LS status and modifying cancer surveillance. However, guidelines for such testing are currently limited. This survey of cancer genetic counselors (GCs) aimed to examine current versus preferred ordering practices and interpretation of somatic MMR testing results in LS evaluation. Two hundred eligible GCs practicing in the United States and Canada were recruited from the National Society of Genetic Counselors. Participants answered questions regarding ordering practices, barriers to somatic MMR testing, theoretical scenarios, and desire for further guidelines. Statistical analysis was performed using chi‐square, Fisher's exact, and Wilcoxon rank‐sum tests, while themes were identified from free‐text responses. Most respondents did not include somatic MMR testing in the LS work‐up, despite three‐quarters reporting they were 'somewhat comfortable' or 'extremely comfortable' with interpreting these results. Approximately half of participants indicated interest in ordering concurrent somatic MMR and germline testing for each of the four theoretical scenarios. Over three‐quarters of individuals reported barriers to ordering somatic MMR testing, with cost and coordinating tissue samples most commonly cited. The frequently reported laboratory‐ and insurance‐related barriers may contribute to the gap between preferred and current ordering practices for somatic MMR testing. Nearly all respondents endorsed additional guidelines for this testing, which could reduce barriers and inform screening recommendations for patients with UMMRD and their family members. [ABSTRACT FROM AUTHOR]

Germline pathogenic variants in the DNA mismatch repair genes (MMR): MLH1, MSH2, MSH6, and PMS2, are causative of Lynch syndrome (LS). However, many of the variants mapping outside the invariant splice site positions (IVS ± 1, IVS ± 2) are classified as variants of unknown significance (VUS). Three such variants (MLH1 c.588+5G>C, c.588+5G>T and c.677+5G>A) were identified in 8 unrelated LS families from Argentina, Brazil and Chile. Herein, we collected clinical information on these families and performed segregation analysis and RNA splicing studies to assess the implication of these VUS in LS etiology. Pedigrees showed a clear pattern of variant co-segregation with colorectal cancer and/or other LS-associated malignancies. Tumors presented deficient expression of MLH1-PMS2 proteins in 7/7 of the LS families, and MSI-high status in 3/3 cases. Moreover, RNA analyses revealed that c.588+5G>C and c.588+5G>T induce skipping of exon 7 whereas c.677+5G>A causes skipping of exon 8. In sum, we report that the combined clinical findings in the families and the molecular studies provided the evidences needed to demonstrate that the three MLH1 variants are causative of LS and to classify c.588+5G>C and c.677+5G>A as class 5 (pathogenic), and c.588+5G>T as class 4 (likely-pathogenic). Our findings underline the importance of performing clinical and family analyses, as well as RNA splicing assays in order to determine the clinical significance of intronic variants, and contribute to the genetic counseling and clinical management of patients and their relatives. [ABSTRACT FROM AUTHOR]

Functional assays that assess mRNA splicing can be used in interpretation of the clinical significance of sequence variants, including the Lynch syndrome-associated mismatch repair (MMR) genes. The purpose of this study was to investigate the contribution of splicing assay data to the classification of MMR gene sequence variants. We assayed mRNA splicing for 24 sequence variants in MLH1 , MSH2 , and MSH6 , including 12 missense variants that were also assessed using a cell-free in vitro MMR activity (CIMRA) assay. Multifactorial likelihood analysis was conducted for each variant, combining CIMRA outputs and clinical data where available. We collated these results with existing public data to provide a dataset of splicing assay results for a total of 671 MMR gene sequence variants (328 missense/in-frame indel), and published and unpublished repair activity measurements for 154 of these variants. There were 241 variants for which a splicing aberration was detected: 92 complete impact, 33 incomplete impact, and 116 where it was not possible to determine complete versus incomplete splicing impact. Splicing results mostly aided in the interpretation of intronic (72%) and silent (92%) variants and were the least useful for missense substitutions/in-frame indels (10%). MMR protein functional activity assays were more useful in the analysis of these exonic variants but by design they were not able to detect clinically important splicing aberrations identified by parallel mRNA assays. The development of high throughput assays that can quantitatively assess impact on mRNA transcript expression and protein function in parallel will streamline classification of MMR gene sequence variants. [ABSTRACT FROM AUTHOR]

Individuals who carry pathogenic mutations in DNA mismatch repair (MMR) genes have high risks of cancer, and small studies have suggested that these risks depend on the sex of the parent from whom the mutation was inherited. We have conducted the first large study of such a parent-of-origin effect (POE). Our study was based on all MMR gene mutation carriers and their relatives in the Colon Cancer Family Registry, comprising 18,226 people. The POE was estimated as a hazard ratio (HR) using a segregation analysis approach that adjusted for ascertainment. HR = 1 corresponds to no POE and HR > 1 corresponds to higher risks for maternal mutations. For all MMR genes combined, the estimated POE HRs were 1.02 (95% confidence interval (CI) 0.75–1.39, p = 0.9) for male colorectal cancer, 1.12 (95% CI 0.81–1.54, p = 0.5) for female colorectal cancer and 0.84 (95% CI 0.52–1.36, p = 0.5) for endometrial cancer. Separate results for each MMR gene were similar. Therefore, despite being well-powered, our study did not find any evidence that cancer risks for MMR gene mutation carriers depend on the parent-of-origin of the mutation. Based on current evidence, we do not recommend that POEs be incorporated into the clinical guidelines or advice for such carriers. [ABSTRACT FROM AUTHOR]

Lynch syndrome is inherited in an autosomal dominant mode. Lynch syndrome is caused by impairment of one or more of the various genes (most frequently MLH1 and MSH2) involved in mismatch repair. In this study, whole genome comparative genomic hybridization array (array CGH) based genomic analysis was performed on twelve Saudi Lynch syndrome patients. A total of 124 chromosomal alterations (structural loss) were identified at mean log2 ratio cut off value of ±0.25. We also found structural loss in 2p21-p16.3, 3p23-p14.2, 7p22.1 and 1p34.1-p33 regions. These findings were subsequently validated by real time quantitative PCR showing downregulation of MSH2, MSH6, EPCAM, MLH1, PMS2 and MUTYH genes. These findings shall help in establishing database for alterations in mismatch repair genes underlying Lynch syndrome in Saudi population as well as to determine the incidence ratio of these disorders. Guided counselling will subsequently lead to the prevention and eradication of Lynch Syndrome in the local population. [ABSTRACT FROM AUTHOR]

Lynch Syndrome is an autosomal dominant cancer predisposition syndrome caused by germline pathogenic variants or epimutation in one of the DNA mismatch repair genes. De novo pathogenic variants in mismatch repair genes have been described as a rare event in Lynch Syndrome (1-5%), although the prevalence of de novo pathogenic variants in Lynch Syndrome is probably underestimated. The de novo pathogenic variant was identified in a 26-year-old woman diagnosed with an adenocarcinoma of the caecum with mismatch repair protein deficiency at immunohistochemistry and a synchronous neuroendocrine tumor of the appendix with normal expression of mismatch repair proteins. DNA testing revealed deletion of exon 6 of the MLH1 gene. It appeared to be a de novo event, as the deletion was not detected in the patient's parents. The presence of a mosaicism in the patient was excluded and haplotype analysis demonstrated the paternal origin of the chromosome harboring the deletion. The de novo deletion probably originated either from a very early postzygotic or a single prezygotic mutational event, or from a gonadal mosaicism. In conclusion, the identification of de novo pathogenic variants is crucial to allow proper genetic counseling and appropriate management of the patient's family., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Introduction: Metastatic colorectal cancer (CRC) remains a dilemma for cancer researchers with an increasing incidence in the younger patient population. Until the last decade, limited therapeutic options were available for metastatic CRC patients leading to relatively poor clinical outcomes. Areas covered: With advances in genome sequencing technology and reductions in the cost of next-generation sequencing, molecular profiling has become more accessible for cancer researchers and clinical investigators, which has furthered our understanding of the molecular behavior of CRC. This progress has recently translated into significant advances in molecular-based therapeutics and led to the development of new target-specific agents in metastatic CRC patients. In this review article, we extensively elaborate on genomic alterations seen in CRC patients including, but not limited to, EGFR, MMR, BRAF, HER2, NTRKs, FGFR, BRCA1/2, PALB2, POLE, and POLD1 genes, all of which are potentially actionable by either an FDA-approved agent or in a clinical trial setting. Expert opinion: We strongly recommend molecular profiling in metastatic CRC patients during the early course of their disease, as this may provide therapeutic and prognostic information that can guide clinicians to practice precision medicine. Patients with potentially actionable genes should be considered for targeting agents based on molecular alterations. [ABSTRACT FROM AUTHOR]

We evaluated microsatellite instability (MSI) in selected mismatch repair (MMR) and tumor suppressor (TS) genes with a view to exploring genetic changes associated with the occurrence of gastric cancer (GC). Moreover, expression of MSI positive genes was measured to get insights into molecular events operating in the tumor microenvironment. We anticipated discovering new molecular targets with potential as molecular biomarkers of gastric cancer. Of the 13 genes screened, we observed 15% to 52.5% MSI at eight microsatellite loci located in 3′ UTR and coding regions of six genes (TGFBR2 , PDCD4 , MLH3 , DLC1 , MSH6 , and MSH3). The union probability of different combinations of unstable microsatellite loci unveiled a set of four MSI markers from TGFBR2 , PDCD4 , MLH3 , and MSH3 genes that allows detection of up to 85% incidences of GC. Significant downregulation of MLH3 , PDCD4 , TGFBR2 , and DLC1 genes was observed in tumor tissues. Protein structure analyses of two unexplored targets, MSH3 (TG 4) and MSH6 (A 7), with MSI in the coding region, exhibited the loss of essential domains in the encoded aberrant protein hampering its function in the MMR machinery. The molecular markers thus identified could potentially be used as MSI biomarkers for the diagnosis of gastric tumorigenesis after further validation. • Microsatellite instability (MSI) was studied in 26 motifs in 7 MMR and 6 TS genes associated with gastric cancer (GC). • Microsatellite markers showing potential as GC biomarkers were identified. • Four of the six MSI positive genes showed significant down regulation in GC. • Microsatellite instability was corroborated with the structural variations in the encoded proteins. [ABSTRACT FROM AUTHOR]

The role of DNA MMR genes in prostate cancer (PrCa) is controversial, as genetic alterations leading to microsatellite instability are incompletely defined in these tumors. ERG rearrangements and PTEN loss are concomitant events in PrCa. The aim of this study has been to analyze the immunohistochemical (IHC) expression of MSH2, MSH6, MLH1, PMS2, ERG, and PTEN and their potential association with the grade group (GG) grading system (WHO 2016) and PSA recurrence in a series of 200 PrCa (PSMAR-Biobank, Barcelona, Spain). MSH2, MLH1, PMS2, and PTEN losses were documented in 8%, 5%, 2%, and 36.5%, respectively. ERG expression was found in 48%. MSH6 showed an increase of expression with respect to basal levels in 42.1% of the cases. A statistical association between MSH6 overexpression and GG5 was found (p = 0.0281). ERG-wild-type cases were associated with single MSH2 loss (p = 0.024), and MSH2 and/or MLH1 loss (p = 0.019). The percentage of cases with PTEN loss was 20.5% (8/39) in GG1, 37.6% (53/141) of clustered GG2 to 4, and 60% (12/20) of GG5 (chi-square test, p = 0.01). Thus, PTEN expression loss was statistically more frequent in the upper-grade tumors. PMS2 loss was an infrequent event, but it was statistically associated with shorter time to PSA recurrence (p = 0.011). These results suggest the existence of an alternative non-ERG pathway associated with MSH2 or MLH1 expression loss. MSH6 overexpression could be a marker of aggressiveness in PrCa. The IHC assessment of DNA MMR proteins, ERG and PTEN, could identify different altered PrCa pathways, which could aid patient stratification. [ABSTRACT FROM AUTHOR]

Immunohistochemistry (IHC) for mismatch repair (MMR) proteins is used to identify MMR status: being diffusely positive (intact/retained nuclear staining) or showing loss of nuclear tumour staining (MMR protein deficient). Four colonic adenocarcinomas and a gastric adenocarcinoma with associated dysplasia that displayed heterogenous IHC staining patterns in at least one of the four MMR proteins were characterised by next‐generation sequencing (NGS). In order to examine a potential molecular mechanism for these staining patterns, the respective areas were macrodissected, analysed for microsatellite instability (MSI) and investigated by NGS and multiplex ligation‐dependent probe amplification (MLPA) analysis of MLH1, MSH2, MSH6 and PMS2 genes, including MLH1 methylation analysis. One colonic adenocarcinoma showed heterogenous MSH6 IHC staining and molecular analysis demonstrated increasing allelic burden of two MSH6 frameshift variants (c.3261delC and c.3261dupC) in areas with MSH6 protein loss compared to areas where MSH6 was retained. Two colonic adenocarcinomas with heterogenous MLH1 staining showed no differences in sequence variants. In one of these cases, however, MLH1 was hypermethylated in the area of MLH1 loss. Another colon carcinoma with heterogenous PMS2 staining (but with retained MSH6) showed both MSH6 c.3261dupC and 3260_3261dupCC where PMS2 protein was lost and only c.3261dupC where PMS2 was retained. The gastric carcinoma showed complete loss of MSH6 in dysplastic foci, while the underlying invasive carcinoma showed retention of MSH6. Both these areas, however, were MSI‐high and showed the same MSH6 variant: c.3261delC. The gastric dysplasia additionally showed MSH6 c.3261dupC. In four of the five cases where MMR protein was lost, these areas were MSI‐high. Heterogenous MMR IHC (focal and/or zonal within the same tumour or between invasive and dysplastic preinvasive areas) is not always due to artefact and is invariably related to MSI‐high status in the areas of loss. An interesting aspect to this study is the presence of MSH6 somatic mutations irrespective of whether MSH6 IHC staining was intact or lost. [ABSTRACT FROM AUTHOR]

Lynch syndrome (LS) is an autosomal dominant genetic disorder associated with germline mutations in DNA mismatch repair (MMR) genes. The carriers of pathogenic mutations in these genes have an increased risk of developing a colorectal cancer and/or LS-associated cancer. The LS-associated cancer types include carcinomas of the endometrium, small intestine, stomach, pancreas and biliary tract, ovary, brain, upper urinary tract and skin. The criteria for the clinical diagnosis of LS and the procedures of the genetic testing for identification of pathogenetic mutations carriers in MMR genes have long been known. A crucial point in the mutation detection analysis is the correct definition of the pathogenecity associated with MMR genetic variants, especially in order to include the mutation carriers in the endoscopy surveillance programs more suited to them. Therefore, this may help to improve the LS-associated cancer prevention programs. In the present review, we also report the recent discoveries in molecular genetics of LS, such as the new roles of MMR protein and immune response of MMR repair deficiency in colorectal cancer. Finally, we discuss the main therapeutic approaches, including immunotherapy, which represent a valid alternative to traditional therapeutic methods and extend the life expectancy of patients that have already developed LS-associated colorectal cancer. [ABSTRACT FROM AUTHOR]

Background: Poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors such as veliparib are potent sensitizing agents and have been safely combined with DNA-damaging agents such as temozolomide. The sensitizing effects of PARP inhibitors are magnified when cells harbor DNA repair defects.Methods: A single-arm, open-label, phase 2 study was performed to investigate the disease control rate (DCR) after 2 cycles of veliparib plus temozolomide in patients with metastatic colorectal cancer (mCRC) refractory to all standard therapies. Fifty patients received temozolomide (150 mg/m2 /d) on days 1 to 5 and veliparib (40 mg twice daily) on days 1 to 7 of each 28-day cycle. Another 5 patients with mismatch repair-deficient (dMMR) tumors were also enrolled. Twenty additional patients were then treated with temozolomide at 200 mg/m2 /d. Archived tumor specimens were used for immunohistochemistry to assess mismatch repair, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), and O(6)-methylguanine-DNA methyltransferase (MGMT) protein expression levels.Results: The combination was well tolerated, although some patients required dose reductions for myelosuppression. The primary endpoint was successfully met with a DCR of 24% and 2 confirmed partial responses. The median progression-free survival was 1.8 months, and the median overall survival was 6.6 months. PTEN protein expression and MGMT protein expression were not predictors of DCR. There was also a suggestion of worse outcomes for patients with dMMR tumors.Conclusions: In this heavily pretreated mCRC population, a combination of veliparib and temozolomide was well tolerated with temozolomide doses up to 200 mg/m2 /d, and it was clinically active. PARP inhibitor-based therapy merits further exploration in patients with mCRC. Cancer 2018;124:2337-46. © 2018 American Cancer Society. [ABSTRACT FROM AUTHOR]

Purpose: A positive resection margin (RM+) is acknowledged as a poor prognostic factor after gastrectomy. Microsatellite instability (MSI-H) gastric cancer has been identified as a subgroup of gastric cancer that may be associated with an improved prognosis. The aim of the study was an analysis of MSI status on patients with margin involvement after gastrectomy and examination of the association between MSI, margin status, and survival outcomes.Methods: From a large prospectively annotated surgical database we collected clinicopathological and survival data on patients who had undergone a potentially curative resection for gastric cancer. MSI status was assessed using a standard 5-marker quasi-monomorphic mononucleotide repeat panel. Patients who were R+ and either microsatellite stable (MSS) or MSI-H were identified and clinicopathological characteristics and disease specific survival was compared.Results: Three hundred and eighty-six patients were identified; 102 (26.4%) cancers were MSI-H. The proportion of R+ resections was not significantly different in MSS and MSI-H groups. For MSS patients 3-, 5-, and 10-year disease-specific survival rates were 9.1%, 0%, and 0%, respectively; for patients with MSI-H R+ tumors these were 38.5%, 30.8%, and 15.4%, respectively. In Cox analysis MSI-H, female gender, and T ≥3 were significantly associated with survival.Conclusions: Patients with MSI-H gastric cancer may have long-term survival despite R+ margin status. The molecular division of gastric cancer may be an important step in identifying possible tailored surgical treatments corresponding to clinical and pathological factors. [ABSTRACT FROM AUTHOR]