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Background: It remains presently unclear whether disease progression in colorectal carcinoma (CRC), from early, to invasive and metastatic forms, is associated to a gradual increase in genetic instability and to a scheme of sequentially occurring Copy Number Alterations (CNAs)., Methods: In this work we set to determine the existence of such links between CRC progression and genetic instability and searched for associations with patient outcome. To this aim we analyzed a set of 162 Chromosomal Instable (CIN) CRCs comprising 131 primary carcinomas evenly distributed through stage 1 to 4, 31 metastases and 14 adenomas by array-CGH. CNA profiles were established according to disease stage and compared. We, also, asked whether the level of genomic instability was correlated to disease outcome in stage 2 and 3 CRCs. Two metrics of chromosomal instability were used; (i) Global Genomic Index (GGI), corresponding to the fraction of the genome involved in CNA, (ii) number of breakpoints (nbBP)., Results: Stage 1, 2, 3 and 4 tumors did not differ significantly at the level of their CNA profiles precluding the conventional definition of a progression scheme based on increasing levels of genetic instability. Combining GGI and nbBP,we classified genomic profiles into 5 groups presenting distinct patterns of chromosomal instability and defined two risk classes of tumors, showing strong differences in outcome and hazard risk (RFS: p = 0.012, HR = 3; OS: p < 0.001, HR = 9.7). While tumors of the high risk group were characterized by frequent fractional CNAs, low risk tumors presented predominantly whole chromosomal arm CNAs. Searching for CNAs correlating with negative outcome we found that losses at 16p13.3 and 19q13.3 observed in 10% (7/72) of stage 2-3 tumors showed strong association with early relapse (p < 0.001) and death (p < 0.007, p < 0.016). Both events showed frequent co-occurrence (p < 1x10-8) and could, therefore, mark for stage 2-3 CRC susceptible to negative outcome., Conclusions: Our data show that CRC disease progression from stage 1 to stage 4 is not paralleled by increased levels of genetic instability. However, they suggest that stage 2-3 CRC with elevated genetic instability and particularly profiles with fractional CNA represent a subset of aggressive tumors.

KRAS mutations are the most common oncogenic event in colorectal cancer (CRC) progression and their occurrence is associated with lack of response to anti epidermal growth factor receptor (EGFR) targeted therapies. Using preclinical models and patients' samples we recently reported that the emergence of KRAS mutations but also KRAS amplification is associated with acquired resistance to the EGFR inhibitors cetuximab or panitumumab. We reasoned that KRAS amplification may also be responsible for primary resistance to these agents. Furthermore, while the prevalence of KRAS mutations has been well established in CRC, little is known about the frequency of KRAS amplification in large CRC series. We performed a screening of 1,039 CRC samples to assess the prevalence of KRAS amplification in this tumor type and further evaluated the role of this genetic alteration on the sensitivity to anti EGFR therapies. We detected KRAS amplification in 7/1,039 (0.67%) and 1/102 evaluable CRC specimens and cell lines, respectively. KRAS amplification was mutually exclusive with KRAS mutations. Tumors or cell lines harboring this genetic lesion are not responsive to anti-EGFR inhibitors. Although KRAS amplification is an infrequent event in CRC, it might be responsible for precluding response to anti-EGFR treatment in a small proportion of patients., (Copyright © 2013 UICC.)

Hereditary non polyposis colorectal cancer or Lynch syndrome is due to germline mutation of one the DNA mismatch repair genes. This mutation is associated with an unstable phenotype in tumor DNA characterized by new microsatellite alleles that are absent in matching normal DNA. Besides the Bethesda reference panel, a new panel of 5 mononucleotide microsatellites (BAT25, BAT26, NR21, NR24, NR27) has been proposed, which is more sensitive and faster to use in a multiplex PCR assay. In tumor cells, immunohistochemistry detects the loss of expression of either MLH1, MSH2, MSH6 or PMS2 protein, corresponding to the mutated gene. Immunohistochemistry guides germline analysis, except for MLH1 extinction which may correspond to either MLH1 germline mutation or methylation of MLH1 promoter resulting in inactivation. The latter is mostly due to aging and is often associated to the V600E BRAF gene mutation in tumor DNA. Combination of these 3 somatic analyses should reduce indications of germline mutation analysis in Lynch syndrome.

Several genes have been involved in drug resistance but none are currently used in the drug decision process. To address this problem, mRNA levels were measured for the 5-fluorouracil metabolism-related genes, thymidylate synthase, thymidine phosphorylase and dihydropyrimidine dehydrogenase in tumor samples of 40 patients with synchronous metastatic colon cancer by quantitative RT-PCR. Drug response and overall survival were also obtained for each patient. A logistic regression model was defined to calculate a response predicting score (RPS) with gene expression levels. This RPS split responders from nonresponders as, at the best statistical threshold (0.35), the area of receiver operating characteristic (ROC) curve established with this method was 0.82 and sensitivity and specificity were respectively 100% and 65.4%. Furthermore patients with scores above 0.35 tended to have better overall survival than those with a score less than 0.35 (p = 0.09).

Purpose: Colorectal adenocarcinoma before the age of 40 is uncommon, and its prognosis is controversial, with many studies reporting a worse prognosis than in older patients and others showing no difference. The current study compared two groups of patients who had surgical resection for colorectal adenocarcinoma., Methods: The case group was composed of 34 patients younger than 40 (34 +/- 4) years. Detailed pathologic prognosis factors, tumor cell proliferation measured by proliferating cell nuclear antigen, survival, family history, and predisposing conditions were analyzed. Results were compared with a control group constituted of 34 patients older than 65 (75 +/- 6) years matched by gender, cancer site, and Dukes stage., Results: Tumor differentiation, presence of vascular and perineural neoplastic invasion, tumor growth pattern, tumor cell proliferation measured by proliferating cell nuclear antigen count, and survival according to the Kaplan-Meier method were not significantly different between younger and older patients. The only difference between the two groups was a higher prevalence of family history and predisposing conditions for colorectal cancer in younger patients (23 vs. 3 percent; P = 0.03)., Conclusion: This case-control study documents that pathologic features and prognosis of colorectal adenocarcinoma are comparable in patients younger than 40 years compared with older patients for identical stages. The higher prevalence of positive family history in younger patients suggests a different genetic background compared with older patients.

Several somatic genetic alterations have been described in colorectal carcinoma (CRC). Recurrent chromosomal deletions have suggested the presence of tumor suppressor genes (TSG) specifically involved in colorectal carcinogenesis. For one of them, two non-overlapping regions have been proposed on the short arm of chromosome 8, encompassing the LPL and NEFL genes. The short arm of chromosome 8 has been extensively studied in colorectal cancer and in other cancer types. Both regions have been reported as candidate loci for a TSG. In order to delineate a reliable region of deletional overlap on chromosome arm 8p in CRC, a series of 365 CRC samples was selected for the absence of microsatellite instability (RER, replication error); tumor and normal matched DNAs were studied for 54 microsatellite polymorphisms distributed on 8p using multiplex-PCR amplification. After purification of tumor nuclei by flow cytometry based on either the abnormal DNA index or the presence of a high expression of cytokeratin, complete allelic losses on 8p were observed in 48% of cases. Measurement of the DNA index showed that 88% of RER tumors were hyperploid. Complete allelic losses of only part of the short arm were observed on 26 occasions. These data allowed us to define a 1 cM interval of common deletion, flanked by the loci D8S1771 and NEFL, where a putative TSG may be localized.

Recurrent allelic losses on chromosome 22q have been reported in colorectal cancer, distal to the NF2 gene, suggesting that another tumor suppressor gene might be involved. We report here the typing of 256 sporadic colorectal tumors and 18 colonic cancer cell lines using a set of chromosome 22 polymorphisms, ranging from 20 to 45. A panel of somatic cell hybrids, that allows to distinguish 11 bins in the 22q13 region, was used to localize 19 of the 45 selected markers and the putative tumor suppressor gene BZRP. Allelic-loss was observed in 43% of tumors. The minimal region of deletion that could be determined, telomeric to locus D22S270, refines significantly the position of the gene. The localization of the BZRP gene in this region led to a systematic screening for somatic point mutation. Direct sequencing of its coding sequence in 36 tumors hemizygous for chromosome 22 allowed the identification of three polymorphisms but failed to detect somatic mutation.

MLH1 and MSH2 protein immunohistochemistry is useful for detection of hereditary non-polyposis colorectal cancer in young patients Aims: Hereditary non-polyposis colorectal cancer is related to germline mutations of DNA mismatch repair genes MLH1 and MSH2 , which result in microsatellite instability and loss of protein expression of the corresponding mutated gene in the tumour tissue. Methods and results: MLH1 and MSH2 protein expression was studied by immunohistochemistry in paraffin-embedded surgical samples of 100 colorectal adenocarcinomas occurring before 50 years of age. Absence of tumour cell nuclear staining with positive internal control (normal mucosa, lymphoid follicles) was considered negative. Loss of MLH1 or MSH2 expression was found in 20 cases with microsatellite instability in 15 cases. Twelve of these patients had a family history of colorectal cancer. Compared with MLH1- and MSH2-positive cases, MLH1- or MSH2-deficient colorectal adenocarcinomas were significantly associated on multivariate analysis with a younger age (38 vs. 43 years, P; 0.0224), a larger tumour size (60 ± 6 vs. 46 ± 2 mm, P =0.0291), an expanding margin (85% vs. 51%, P =0.0159), a higher number of tumour-infiltrating lymphocytes assessed by CD3 immunostaining (202 ± 48 vs. 33 ± 4 CD3+ lymphocytes/10 high-power fields, P =0.0039), and a grade 2 Crohn's like lymphoid reaction (70% vs. 9%, P =0.0037). The two groups were not different for tumour site, differentiation, pTNM stage, vascular and perineural invasion, peripheral adenomatous residue, and 5-year survival rates. Conclusions: MLH1- or MSH2-deficient colorectal carcinomas of young patients exhibit pathological and molecular features similar to hereditary non-polyposis colorectal cancer. This suggests that MLH1 and MSH2 immunohistochemistry is valuable for detecting hereditary non-polyposis colorectal cancer in young patients. [ABSTRACT FROM AUTHOR]