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Introduction Colorectal cancer is a common malignancy that can be cured when detected early, but recurrence among survivors is a persistent risk. A field effect of cancer in the colon has been reported and could have implications for surveillance, but studies to date have been limited. A joint analysis of pooled transcriptomic data from all available bulk RNA-sequencing data sets of healthy, histologically normal tumor-adjacent, and tumor tissues was performed to provide an unbiased assessment of field effect. Methods A novel bulk RNA-sequencing data set from biopsies of nondiseased colon from screening colonoscopy along with published data sets from the Genomic Data Commons and Sequence Read Archive were considered for inclusion. Analyses were limited to samples with a quantified read depth of at least 10 million reads. Transcript abundance was estimated with Salmon, and downstream analysis was performed in R. Results A total of 1,139 samples were analyzed in 3 cohorts. The primary cohort consisted of 834 independent samples from 8 independent data sets, including 462 healthy, 61 tumor-adjacent, and 311 tumor samples. Tumor-adjacent gene expression was found to represent an intermediate state between healthy and tumor expression. Among differentially expressed genes in tumor-adjacent samples, 1,143 were expressed in patterns similar to tumor samples, and these genes were enriched for cancer-associated pathways. Discussion Novel insights into the field effect in colorectal cancer were generated in this mega-analysis of the colorectal transcriptome. Oncogenic features that might help explain metachronous lesions in cancer survivors and could be used for surveillance and risk stratification were identified.

PURPOSE: Colorectal cancers arise via cumulative genetic and molecular changes that cause mucosal instability, premalignant polyps, and malignant transformation. Distinct neoplastic pathways characterized by chromosomal instability, genetic mutation, and epigenetic methylation have been described, but their associated precursor polyps have not. This study analyzes characteristics of precursor polyps occurring within different molecular subtypes of sporadic colorectal cancer. METHODS: Colorectal cancers from a prospectively maintained frozen tissue bank were analyzed for microsatellite stability and promoter methylation, defined by the CpG island methylator phenotype. Patients with tumors meeting the following criteria were included: microsatellite stable and methylator-negative; microsatellite stable and methylator-positive; and microsatellite unstable and methylator-positive. Hereditary cancers were excluded. Patient demographics, colonoscopic and histologic polyp characteristics, operative reports, and pathology reports were reviewed. RESULTS: One hundred seven patients were included: 65, 20, and 22 patients in each group, respectively. The proportion of patients with synchronous polyps and polyp number, size, and location were similar. However, associated polyp histology varied according to tumor classification. Microsatellite stable tumors, regardless of methylator status, had a greater proportion of adenomas than microsatellite unstable tumors, which had an increased proportion of serrated polyps (P = 0.029). CONCLUSIONS: Patients with microsatellite unstable colorectal cancers demonstrate an increased serrated polyp-to-adenoma ratio compared with microsatellite stable cancers regardless of methylator status. Loss of microsatellite stability appears to be a key event in serrated polyp and cancer formation. An increased proportion of serrated polyps to adenomas discovered in patients on colonoscopy should arouse suspicion that cancers arising in these patients are probably microsatellite unstable.

PURPOSE: Colorectal cancers develop through various mechanisms such as chromosomal instability, DNA mismatch repair deficiency (microsatellite instability), and epigenetic DNA promoter methylation (CpG island methylator phenotype). This study evaluated the disparity in neoplastic changes between colon and rectal cancers. METHODS: A clinic-based colorectal frozen tumor bank at a single institution was queried for colon and rectal adenocarcinomas. Tumor DNA was extracted and analyzed for microsatellite instability, methylation, and mutations in the oncogenes KRAS and BRAF. Patient demographics, tumor characteristics, and clinical outcomes were compared. RESULTS: The 268 patients with colon cancer and 89 with rectal cancer were similar in gender, tumor size, stage, and differentiation. Colon cancers had a higher incidence of microsatellite instability (27 percent) and methylator phenotype (28 percent) compared with rectal cancers (7 percent, 3 percent, respectively; P < 0.001). Although KRAS mutation rate was similar, colon cancers had a higher incidence of BRAF mutations (16.7 percent vs. 0 percent; P < 0.001). Microsatellite stable tumors had an increased risk of disease recurrence compared with microsatellite unstable tumors (odds ratio, 3.86). Despite overall differences in outcome between colon and rectal cancers, no significant difference in survival existed when similar molecular phenotypes were compared across anatomic sites. CONCLUSIONS: Although colon cancers are molecularly heterogeneous, rectal cancers arise mostly via a single neoplastic pathway. Genetic and molecular differences influence prognosis more than anatomic location and suggest that oncogenic pathways contribute to survival differences between colon and rectal cancers.

Body size has been hypothesized to affect the risk of prostate cancer (PCa). However, previous studies have provided conflicting results, in that some show positive associations, whereas others indicate inverse associations or null findings. To further understand this we examined the effects of weight, height, body mass index and lean body mass (LBM) on PCa risk and aggressiveness in a sibling based case-control study.A total of 439 cases were recruited at major medical institutions in Cleveland, Ohio and Detroit, Michigan, and 479 unaffected brothers were recruited as controls. Conditional logistic regression with robust variance estimation was used to evaluate the association between body size and PCa.Higher LBM was inversely associated with PCa, especially in men with more aggressive disease or a later age at onset. Comparing those above and below the 25th percentile showed an OR of 0.49 (95% CI 0.28 to 0.84) and 0.28 (95% CI 0.14, 0.56), respectively. Similar inverse patterns were observed for weight. No noteworthy associations were observed between PCa and height or body mass index.These observations suggest that PCa may be affected by LBM.

Several types of genetic aberrations including microsatellite instability (MSI), allelic imbalance (AI), and chromosomal trisomies have been reported in low-grade (LG) mucosa-associated lymphoid tissue (MALT)-type gastric lymphomas. Presence of such genetic alterations could be a discriminator between de novo large cell lymphoma and high-grade (HG) MALT-type lymphoma. We investigated 17 primary gastric large B-cell lymphomas with and without features of MALT-type lymphoma for MSI, AI, and presence of trisomy of chromosomes 3, 12, and 18. We studied resection specimens from 17 primary gastric extranodal diffuse large B-cell lymphomas. Cases classified as HG MALT-type lymphoma, based on either the presence of LG MALT-type lymphoma component in the background (L/H MALT) or large cell lymphoepithelial lesions (HG MALT), and diffuse large B-cell lymphoma (DLBCL-NOS) when no features of MALT were present. MSI was analyzed using fluorescently labeled polymerase chain reaction primers (D3S11, D6S262, D3S1261, D3S1262, D3S1265). Paired tumor and normal DNA samples were amplified, and PCR products were analyzed on a DNA sequencer (ABI PRISM 373XL) with GeneScan (Applied Biosystems, Foster City, CA). MSI was defined as a gain of a novel-length allele compared with the corresponding normal tissue. AI was assessed at locus 3q27 (D3S1262 and D3S1265). The cases were analyzed for the presence of trisomy of chromosomes 3, 12, and 18 using interphase fluorescence in situ hybridization. MSI was detected in 4 out of 15 (27%) cases from which DNA was amplifiable with all primers and all MALT-type lymphomas. In two cases (13%), MSI was present at two loci sufficient to be classified as high-frequency MSI (MSI-H); this was seen exclusively in HG MALT lymphomas (P = 0.04). In the remaining two cases, MSI was detected at a single locus (low-frequency MSI). Allelic imbalance at the locus D3S1262 was detected in 4 out of 17 (24%) cases. It occurred more commonly in stage IE lymphomas when compared with higher stages (P = 0.03), regardless of lymphoma subtype. Trisomy 12 was detected in 3 out of 17 cases (18%) exclusively in stage IE lymphomas (P = 0.08). MSI was uncommon and was found exclusively in MALT-type lymphomas. MSI-H was even less common but occurred in HG MALT lymphomas only. Allelic imbalance at 3q27 (D3S1262) and trisomy 12 were found more commonly in low-stage disease. The latter two findings are in concordance with the recent suggestion that the published variation in gain of chromosomal material in high-grade gastric lymphomas may be related to stage rather than to the subtype of lymphoma. Because of the relatively low frequency of MSI in the high-grade B-cell lymphomas of the stomach, this feature cannot be used to reliably discriminate between the histologic types of extranodal diffuse large B-cell lymphoma.

Borderline epithelial ovarian tumors (BEOTs) possess clinical and pathologic features intermediate between cystadenomas and cystadenocarcinomas. Although the clinical and pathologic characteristics of BEOTs are well described, the molecular aspects are poorly understood. Three regions of loss of heterozygosity (often referred to as allelic imbalance [AI] when identified by polymerase chain reaction) on chromosome 17p13, one of which includes the p53 gene, have been implicated in the development of ovarian and breast cancers. To provide evidence that genes in these regions also may be involved in the development of BEOTs, we undertook a detailed analysis of AI at all three loci in BEOTs from 21 patients. Seventeen of the BEOTs were serous and four were mucinous. Five of 21 tumors (24%) had AI at one or more loci. Four tumors had AI using the D17S695 marker, two of which showed AI only at this locus. In addition, three tumors exhibited AI at the D17S654 locus, one of which showed AI only at this locus. These data suggest that there may be two tumor suppressor genes distal to p53 involved in the development of at least a subset of BEOTs. Peritoneal implants from a subset of serous BEOTs also were evaluated for AI and were found to be concordant with the primary tumor in all cases. Their genetic similarity is consistent with the implantation theory of peritoneal spread of serous BEOTs in these cases.