High thymidylate synthase expression in colorectal cancer with microsatellite instability: implications for chemotherapeutic strategies.

Colon cancers displaying microsatellite instability (MSI) are clinically less aggressive. Based on in vitro studies and recent clinical data, cancers displaying MSI do not respond to 5-fluorouracil (5-FU). The reasons why MSI tumors are clinically less aggressive and do not respond to 5-FU-based therapies have not been fully elucidated. PURPOSE: We investigated biomolecular markers in an attempt to explain the different clinical behavior and chemotherapeutic responses of MSI and non-MSI colon cancers. EXPERIMENTAL DESIGN: One hundred ninety-two sporadic colon cancers were tested for MSI with five mononucleotide markers and methylation of the hMLH1 promoter. Slides were stained for thymidylate synthase (TS), p53, MDM2, p21(WAF1/CIP1), beta-catenin, vascular endothelial growth factor, hMLH1, hMSH2, and hMSH6. Tumors were regarded as having wild-type, functional p53 (Fp53) if reduced expression of p53 and positive MDM2 and p21(WAF1/CIP1) expressions were found. RESULTS: Of the cases, 12.5% were MSI-H (at least two markers mutated). Of MSI-H cases, 83.3% were characterized by a complete loss of at least one of the mismatch repair proteins, in particular loss of hMLH1 by promoter hypermethylation. MSI-H colon cancers showed higher expression of TS compared with MSS (no mutated markers)/MSI-L (one mutated marker) colon cancers (66.6% for MSI-H versus 14.8% MSS/MSI-L; P < 0.0001); 20.8% of MSI-H cases showed high expression of the vascular endothelial growth factor, compared with 45.8% MSS/MSI-L colon cancers (P = 0.0005); 45.8% MSI-H cases had Fp53 compared 11.9% MSS/MSI-L cases (P < 0.0001). CONCLUSIONS: About 12% of colon cancers display MSI mostly due to lack of hMLH1 resulting from promoter hypermethylation. These tumors have high expression of TS and retain fully functional p53 system. Thus, these data suggest why sporadic hMLH1-defective colon cancers often do not respond to 5-FU.     

Frequent alterations of the beta-catenin and TCF-4 genes, but not of the APC gene, in colon cancers with high-frequency microsatellite instability

High-frequency microsatellite instability (MSI-H) due to defective DNA mismatch repair (MMR) is a characteristic of the majority of tumors from kindreds with hereditary nonpolyposis colorectal cancer (HNPCC) and a subset of sporadic cancers. To better understand the molecular characteristics of colon cancers with MSI-H, we analyzed these cancers for alterations of genes, such as APC, beta-catenin, and TCF-4 genes, involved in the Wnt signaling pathway. Following the National Cancer Institute (NCI) criteria, 385 unselected colon cancers were classified as follows: 50 (13%) MSI-H tumors, 36 (9%) low-frequency MSI (MSI-L) tumors, and 299 (78%) microsatellite stable (MSS) tumors. The frequency of APC mutations was significantly lower in MSI-H tumors (9 out of 50) than in MSI-L (12 out of 20) and MSS (66 out of 100) tumors (P = 0.0005 and P < 0.0001, respectively). In contrast, the frequency of exon 3 mutations in the beta-catenin gene was higher in MSI-H tumors (10 out of 50) than in MSI-L tumors (0 out of 30; P = 0.0110) and MSS tumors (3 out of 100; P = 0.0010). Frameshift mutations in a (A)9 tract of the TCF-4 gene were detected in 44% (22 out of 50) of MSI-H tumors, but not in any of the 20 MSI-L tumors or 40 MSS tumors. In total, 78% of MSI-H tumors and 84% of the remaining tumors had at least one alteration in APC, beta-catenin, or the TCF-4 genes. Although further analysis is needed to functionally characterize the consequences of each of these alterations on beta-catenin/TCF target gene expression, our results suggest that the activation of the Wnt signaling pathway plays a pivotal role in colon tumorigenesis, irrespective of MSI status.     

Sporadic colorectal adenocarcinomas with high-frequency microsatellite instability

BACKGROUND: Widespread microsatellite instability (MSI) occurs in nearly 15% of sporadic colorectal cancers. Large bowel carcinomas with high-frequency MSI (MSI-H) (instability at > or = 30% of microsatellite loci) are believed to display distinctive pathologic features and to behave less aggressively than microsatellite-stable (MSS) tumors and carcinomas with low-frequency MSI (MSI-L) (instability at < 30% of microsatellite loci). The aim of the current study was to accurately define the clinicopathologic and biologic features of MSI-H sporadic colorectal carcinomas. METHODS: MSI status was evaluated in 216 large bowel adenocarcinomas using polymerase chain reaction (PCR) and 6 microsatellite markers. Tumors that showed instability with at least two microsatellite markers were classified as MSI-H, whereas the other tumors were classified as MSI-L (instability at one locus) or MSS (no instability). Expression of p53, hMLH1, and hMSH2 gene products was determined by immunohistochemistry, and DNA ploidy pattern was determined by flow cytometry. The prognostic significance of MSI status was assessed by univariate and multivariate survival analyses. RESULTS: The significantly different pathologic features of MSI-H carcinomas were proximal location; large size; mucinous and medullary histotype; poor differentiation; expanding pattern of growth; more frequent Crohn-like conspicuous lymphoid reaction; and low incidence of extramural vein invasion. Most MSI-H tumors were DNA diploid (33 of 40 tumors; 82.5%) and p53 negative (34 of 44 tumors; 77.3%). Conversely, DNA aneuploidy and p53 overexpression were observed in 82.3% (130 of 158 tumors; P < 0.0001) and 54.1% (93 of 172 tumors; P = 0.0002) of MSI-L/MSS tumors, respectively. Loss of hMLH1 or hMSH2 expression was detected in a high fraction of MSI-H carcinomas (86. 0%). Patients with MSI-H tumors showed a better clinical outcome than patients with MSI-L/MSS tumors (P = 0.0017). Furthermore, in multivariate analysis that included conventional clinicopathologic parameters, MSI status, and p53 expression as covariates, MSI status was a significant independent prognostic indicator of disease specific survival. CONCLUSIONS: Assessment of MSI status is an essential step in the genetic characterization of large bowel carcinomas and identifies a subset of tumors with distinct clinical, pathologic, and biologic features.     

Proliferation, apoptosis, and survival in high-level microsatellite instability sporadic colorectal cancer.

Sporadic colorectal cancer (CRC) characterized by high-level DNA microsatellite instability (MSI-H) has a favorable prognosis. The reason for this MSI-H survival advantage is not known. The aim of this study was to correlate proliferation, apoptosis, and prognosis in CRC stratified by MSI status. The proliferative index (PI) was measured by immunohistochemical staining with the Ki-67 antibody in a selected series of 100 sporadic colorectal cancers classified according to the level of MSI as 31 MSI-H, 29 MSI-Low (MSI-L), and 40 microsatellite stable (MSS). The Ki-67 index was significantly higher in MSI-H cancers (P < 0.0001) in which the PI was 90.1 +/- 1.2% (mean +/- SE) compared with 69.5 +/- 3.1% and 69.5 +/- 2.3% in MSI-L and MSS subgroups, respectively. There was a positive linear correlation between the apoptotic index (AI) and PI (r = 0.51; P < 0.001), with MSI-H cancers demonstrating an increased AI:PI ratio indicative of a lower index of cell production. A high PI showed a trend toward predicting improved survival within MSI-H cancers (P = 0.09) but did not predict survival in MSI-L or MSS cancers. The AI was not associated with survival in any MSI subgroup. In conclusion, this is the first study to show that sporadic MSI-H cancers are characterized by a higher AI:PI ratio and increased proliferative activity compared with MSI-L and MSS cancers, and that an elevated PI may confer a survival advantage within the MSI-H subset.     

Thymidylate synthase expression in colon carcinomas with microsatellite instability.

PURPOSE: Colon cancer cells with high-frequency microsatellite instability (MSI-H) display resistance to 5-fluorouracil (5-FU) that can be reversed by restoring DNA mismatch repair (MMR) proficiency. Given that thymidylate synthase (TS) is inhibited by 5-FU, we studied the relationship between MSI and TS expression, and the prognostic effect of these and other markers (i.e., p53 and 17p allelic imbalance). EXPERIMENTAL DESIGN: Dukes' stage B2 and C colon carcinomas (n = 320) from participants in 5-FU-based adjuvant therapy trials were analyzed for MSI and 17p allelic imbalance. Expression of MMR (hMLH1, hMSH2), TS, and p53 proteins were analyzed by immunohistochemistry. Correlations between markers and associations with overall survival were determined. RESULTS: Of 320 cancers studied, 60 (19%) were MSI-H. TS expression variables were similar in MSI-H and microsatellite stable/low-frequency MSI (MSS/MSI-L) cancers, and unrelated to MMR proteins. MSI-H tumors had lower stage (P = 0.0007), fewer metastatic lymph nodes (P = 0.004), and improved overall survival (P = 0.01). Loss of MMR proteins was also associated with better overall survival (P = 0.006). None of the TS variables were prognostic. Histologic grade (P = 0.0008) and nodal status (P = 0.0002) were associated with overall survival, in contrast to 17p allelic imbalance or p53. Only MSI status or loss of MMR proteins, histologic grade, and tumor stage were independent markers for overall survival. CONCLUSIONS: MSI-H tumors show earlier stage at presentation and better stage-adjusted survival rates. MSI status and TS expression were unrelated and TS was not prognostic, suggesting that TS levels cannot explain therapeutic resistance to 5-FU reported in MSI-H colon cancers.     

Genetic and clinical features of human pancreatic ductal adenocarcinomas with widespread microsatellite instability

The incidences of microsatellite instability (MSI) and underlying DNA mismatch repair (MMR) defects in pancreatic carcinogenesis have not been well established. We analyzed 100 sporadic and 3 hereditary pancreatic ductal adenocarcinomas for MSI, and high-frequency MSI (MSI-H) and low-frequency MSI (MSI-L) tumors were further analyzed for frameshift mutations of possible target genes and for promoter methylation and mutation of DNA MMR genes, including hMLH1, hMSH2, hMSH3, and hMSH6 genes. Among the 100 sporadic tumors, 13 (13%) were MSI-H, 13 (13%) were MSI-L, and 74 (74%) were microsatellite stable (MSS) tumors. All of the three hereditary tumors from hereditary nonpolyposis colorectal cancer (HNPCC) patients were MSI-H. MSI-H tumors were significantly associated with poor differentiation and the presence of wild-type K-RAS and p53 genes. Patients with MSI-H tumors had a significantly longer overall survival time than did those with MSI-L or MSS tumors (P = 0.0057). Frameshift mutations of hMSH3, hMLH3, BRCA-2, TGF-beta type II receptor, and BAX genes were detected in MSI-H tumors. Hypermethylation of the hMLH1 promoter was observed in 6 (46%) of the 13 sporadic MSI-H tumors but not in any of the 3 hereditary MSI-H tumors or 13 MSI-L tumors. All of the 3 HNPCC cases had germ-line hMLH1 mutation accompanied by loss of heterogeneity or other mutation in the tumor. Our results suggest that pancreatic carcinomas with MSI-H represent a distinctive oncogenic pathway because they exhibit peculiar clinical, pathological, and molecular characteristics. Our results also suggest the principal involvement of epigenetic or genetic inactivation of the hMLH1 gene in the pathogenesis of pancreatic carcinoma with MSI-H.     

Low-level microsatellite instability in most colorectal carcinomas

Twelve to 16% of colorectal cancers (CRCs) display a high degree of microsatellite instability (MSI-H), whereas most are believed to be microsatellite stable (MSS). The existence of a low degree of instability (MSI-L) group has also been proposed. By using the Bethesda panel of microsatellite markers, the microsatellite instability (MSI) status of CRCs can be determined. This set is recommended to distinguish between MSI-H and MSI-L/MSS. No definition for MSI-L has emerged. Most reports on MSI-L rely on the Bethesda panel, using 5-15markers. Tumors with more than 30% MSI are designated as MSI-H, but the lower limit for MSI-L is ambiguous. We hypothesized that if many markers are studied, almost all CRCs would show some MSI. It would be necessary to establish a cutoff level for MSI-L by showing that, above this cutoff level, tumors display molecular and/or clinical features different from those under the cutoff level. To perform this task, we analyzed 90 BAT26 stable CRC samples with 377 markers. MSI at 1-11 loci was observed in 71 (79%) of the 90 cases. K-RAS mutation, loss of heterozygosity, and MLH1 and MGMT hypermethylation analyses were performed, as well as clinical features being scrutinized, to examine possible differences between MSI-L and MSS tumors using all of the possible cutoff levels for MSI-L. Convincing differences between putative MSI-L and MSS groups were not observed. Our results show that the sensitivity of a typically used marker number to detect MSI-L is very low, and they suggest that MSS and MSI-L tumors have a common molecular background.     

Microsatellite instability, prognosis and metastasis in gastric cancers from a low-risk population

We examined 169 cases of gastric adenocarcinoma for microsatellite instability (MSI), using a panel of 8 microsatellite markers. Of these cases, 142 were from the United States, a country of relatively low risk for gastric cancer. Comparing microdissected tumors to normal cells from the same patient, we classified tumors as being microsatellite-stable (MSS) or having a low frequency of MSI (MSI-L, up to 30% of markers different in the tumor) or a high frequency of MSI (MSI-H, 30% or more of markers different). Among our American cases, we identified 26 (18.2%) showing MSI-H and 15 (10.6%) showing MSI-L. Twenty cases were from Korean patients, and they showed no significant differences in proportions of MSI-H and MSI-L from the American cases. MSI-H tumors in the American patients were characterized by elevated frequencies of band shifts in repeat sequences of the BAX (50%), transforming growth factor-beta receptor type II (TGFbetaRII, 68.9%), beta(2)-microglobulin (21.4%) and E2F4 (51.7%) genes. Alterations in E2F4 in MSI-H tumors were always integral multiples of 3 nucleotides lost or gained, which would not cause a frameshift mutation, and within the range of normal polymorphisms for this sequence. North American patients (n = 127) with MSI-H and MSI-L tumors had a longer median survival of 541 days and 587 days, respectively, compared to 265 days for patients with MSS tumors (p = 0.027). This survival difference may result from a significantly greater tendency for metastases in the MSS group (p = 0.031).     

Genetic alterations of sporadic colorectal cancer with microsatellite instability, especially characteristics of primary multiple colorectal cancers

BACKGROUND AND OBJECTIVES: The purpose of this study was to elucidate genetic alterations of sporadic colorectal cancers with Microsatellite instability (MSI). METHODS: One hundred and ten patients with sporadic colorectal cancer were examined. The MSI was assessed using eight microsatellite markers. In addition, mutation analysis was performed for Transforming growth-beta type II receptor (TGF beta R II), bcl-2 associated X protein (BAX), Insulin-like growth factor II receptor (IGF II R), human MutS homolog 3 (hMSH3), human MutS homolog 6 (hMSH6), human MutS homolog 2 (hMSH2), and human MutL homolog 1 (hMLH1) genes. Tumors with three or more positive loci have been determined to be MSI-H (high-frequency MSI), tumors with one or two positive loci were designated as MSI-L (low-frequency MSI) and tumors lacking apparent instability were designated as MSS (microsatellite stable). RESULTS: There were 11 cases with MSI-H (MSI-H group) and 99 cases with MSI-L/MSS (MSI-L/MSS group). The frequency of cases with multiple colorectal cancer in the MSI-H group was significantly higher than that of MSI-L and MSS group (81.8% vs. 34.3%, p = 0.0022). The frequency of cases with multiple cancers increased as the number of locus with microsatellite instability increased. Among 11 tumors with MSI-H, 7 indicated mutation of the TGF beta R II (63.6%), whereas no tumor had a mutation of the TGF beta R II among 20 tumors with MSI-L (p = 0.0001). Regarding the BAX, hMSH3, hMSH6 gene, the same trend was obtained as the TGF beta R II gene (18.2% vs. 0%, p = 0.0487, 36.4% vs. 0%, p = 0.0039, 27.3% vs. 0%, p = 0.0140, respectively). Only two cases indicated a somatic point mutation of the hMSH2 gene. CONCLUSIONS: The multiple occurrence of the colorectal carcinoma may be related to MSI-H as well as the mutation of genes possessing repetitive mononucleotide tracts. Furthermore, we recommend strict follow-up in sporadic colorectal patients that indicate MSI-H.     

Low microsatellite instability is associated with poor prognosis in stage C colon cancer.

PURPOSE: The significance of low microsatellite instability (MSI-L) in colorectal cancer is poorly understood. No clear biologic distinction has been found between MSI-L and microsatellite stable (MSS) colorectal cancer, and these two phenotypes are usually combined when analyzed against the well-defined high MSI (MSI-H) phenotype. Evidence is emerging that an O(6)-methylguanine DNA methyltransferase (MGMT) gene defect is associated with MSI-L. Therefore, to further define this phenotype, we undertook a detailed analysis of the prognostic significance of MSI-L and loss of MGMT expression in colon cancer. PATIENTS AND METHODS: The study cohort was 183 patients with clinicopathologic stage C colon cancer who had not received adjuvant therapy. We analyzed MSI status, MGMT, and mismatch repair protein expression, as well as MGMT and p16 promoter hypermethylation. RESULTS: We showed that MSI-L defines a group of patients with poorer survival (P = .026) than MSS patients, and that MSI-L was an independent prognostic indicator (P = .005) in stage C colon cancer. Loss of MGMT protein expression was associated with the MSI-L phenotype but was not a prognostic factor for overall survival in colon cancer. p16 methylation was significantly less frequent in MSI-L than in MSI-H and MSS tumors and was not associated with survival. CONCLUSION: MSI-L characterizes a distinct subgroup of stage C colon cancer patients, including the MSI-L subset of proximal colon cancer, who have a poorer outcome. Neither the MGMT defect nor p16 methylation are likely to contribute to the worse prognosis of the MSI-L phenotype.     

Frequent Bax frameshift mutations in gastric cancer with high but not low microsatellite instability

Widespread microsatellite instability (MSI) due to the defective DNA mismatch repair underlies the pathogenesis of the majority of hereditary non-polyposis colorectal cancer and a subset of various sporadic malignant tumors. Using 5 microsatellite markers and the criteria of MSI proposed by the National Cancer Institute (NCI) workshop, we analyzed 205 gastric adenocarcinomas for MSI. Based on the number of markers showing instability per tumor, the tumors were divided into three groups; those with two or more of the five markers displaying instability (high MSI, MSI-H), those with one of five markers displaying instability (low MSI, MSI-L), and those with no instability (microsatellite stable, MSS). Among 205 tumors, 30 (15%) were MSI-H, 15 (7%) were MSI-L, and 160 (78%) were MSS. All of the 30 MSI-H tumors demonstrated instability at BAT26, a sensitive marker for the widespread MSI, while none of the 15 MSI-L tumors did. MSI-H tumors were significantly associated with distal location and well or moderate differentiation, but MSI-L tumors were indistinguishable from MSS tumors. Bax frameshift mutations were detected in 60% of the 30 MSI-H tumors, while not in any of the 15 MSI-L tumors. These results suggest that microsatellite analysis using the criteria proposed by the NCI workshop may be appropriate for gastric cancers because it unveils real differences in genotype and phenotype.     

Immunohistochemistry versus microsatellite instability testing in phenotyping colorectal tumors.

PURPOSE: To compare microsatellite instability (MSI) testing with immunohistochemical (IHC) detection of hMLH1 and hMSH2 in colorectal cancer. PATIENTS AND METHODS: Colorectal cancers from 1,144 patients were assessed for DNA mismatch repair deficiency by two methods: MSI testing and IHC detection of hMLH1 and hMSH2 gene products. High-frequency MSI (MSI-H) was defined as more than 30% instability of at least five markers; low-level MSI (MSI-L) was defined as 1% to 29% of loci unstable. RESULTS: Of 1,144 tumors tested, 818 showed intact expression of hMLH1 and hMSH2. Of these, 680 were microsatellite stable (MSS), 27 were MSI-H, and 111 were MSI-L. In all, 228 tumors showed absence of hMLH1 expression and 98 showed absence of hMSH2 expression: all were MSI-H. CONCLUSION: IHC in colorectal tumors for protein products hMLH1 and hMSH2 provides a rapid, cost-effective, sensitive (92.3%), and extremely specific (100%) method for screening for DNA mismatch repair defects. The predictive value of normal IHC for an MSS/MSI-L phenotype was 96.7%, and the predictive value of abnormal IHC was 100% for an MSI-H phenotype. Testing strategies must take into account acceptability of missing some cases of MSI-H tumors if only IHC is performed.     

Mucin core protein expression in colorectal cancers with high levels of microsatellite instability indicates a novel pathway of morphogenesis.

Particular mucinous phenotypes have been associated with serrated epithelial polyps of the colon. These polyps also show a high frequency of DNA instability. The aim of this study was to examine the expression of mucins in colorectal cancers that arise through the suppressor and mutator pathways. The immunohistochemical distribution of the human apomucins MUC1, MUC2, MUC4, and MUC5AC was determined in 93 sporadic colorectal cancers classified previously (J. R. Jass et al., J. Clin. Pathol., 52: 455-460, 1999) according to levels of DNA microsatellite instability (MSI) as 22 MSI-high (MSI-H), 24 MSI-low (MSI-L), and 47 MS stable (MSS). MUC2 expression was observed in 19 (86%) MSI-H, 10 (42%) MSI-L, and 15 (32%) MSS cancers (P = 0.0001); and MUC5AC expression was observed in 17 (77%) MSI-H, 8 (33%) MSI-L, and 13 (28%) MSS cancers (P = 0.0003). There was no association between MUC1 or MUC4 expression and MSI status. The mucinous phenotype described in serrated polyps (MUC2+/MUC5AC+) was seen in 15 (68%) of 22 MSI-H and only 10 (14%) of 71 MSI-L/MSS cancers (P < 0.0001). Increased expression of the secretory mucins MUC2 and MUC5AC was observed in sporadic MSI-H cancers. Identical mucin changes and DNA MSI occurred in serrated polyps of the colorectum, which suggests that these lesions may represent precursors of MSI-H cancers.     

Biological features of sporadic colorectal carcinoma with high-frequency microsatellite instability: special reference to tumor proliferation and apoptosis

Background We evaluated the relationship between biological behavior and microsatellite instability (MSI) status, with or without p53 status, in sporadic colorectal carcinoma.Methods MSI was analyzed with regard to biological features such as cellular proliferation and apoptotic cell death, in addition to clinicopathological features, in 87 patients with sporadic colorectal carcinoma.Results Fourteen (16.1%) of 87 tumors showed instability at two or more of the five loci examined (high-frequency MSI [MSI-H]). Four demonstrated instability at one locus (low-frequency MSI [MSI-L]), and 69 showed no instability (microsatellite-stable [MSS]). The MSI-H tumors tended to be located in the proximal colon and more often were mucinous carcinoma. The MSI-H tumors also tended to be in patients with multiple colorectal carcinomas and to demonstrate, rarely, an infiltrating growth pattern or venous invasion. The incidence of p53 protein overexpression in the MSI-H tumors was significantly lower than that in the MSI-L/MSS tumors (21% vs 54%). There was no significant difference in the proliferating-cell nuclear antigen (PCNA) labeling index (PI) or apoptotic index (AI) between the MSI-H and MSI-L/MSS tumors. The AI in the MSI-H tumors with p53 overexpression was significantly lower than that in the MSI-H tumors without p53 overexpression, and was also significantly lower than that in the MSI-L/MSS tumors with p53 overexpression. In the MSI-H tumors with p53 overexpression, no expression of BAX protein was found, and there was high expression of bcl-2 protein, resulting in a low BAX/bcl-2 ratio.Conclusion In sporadic colorectal carcinoma, an MSI-H tumor with p53 protein overexpression may display aggressive biological features.     

Microsatellite Instability and Life Style Factors in Sporadic Colorectal Cancer

Background: Colorectal cancer (CRC) in Egypt is a relatively high young onset disease. As a form of heterogeneous cancer, there is interplay between genetic and environmental factors. We aimed at probing the association of life style factors and Microsatellite Instability (MSI) status that could provide more insights on carcinogenic process of CRC. Methods: One hundred incident sporadic CRC patients were involved. Information on risk factors of CRC was obtained and microsatellite instability status was predicted through evaluation of MMR protein expression via immunohistochemistry (IHC). Results: Median age was 47.50 years, females represented 54.0% and 36% of patients were Microsatellite Instability High (MSI-H). Most patients with right sided colon cancer (78.3%) were MSI-H while mostly stable or low MSS/MSI-L for left-sided colon and rectum (78.6%, 74.3% respectively, p<0.001). Patients with low physical activity had higher risk of MSS/MSI-L than those with moderate or high activity p =0.026. Patients with BMI greater than 30 Kg/m2 had higher MSS/MSI-L (75.5%) than those with BMI between 25-30 Kg/m2 (60.6%) and those with normal BMI     

Morphological and molecular heterogeneity within nonmicrosatellite instability-high colorectal cancer

Colorectal cancer (CRC) has traditionally been classified into two groups: microsatellite stable/low-level instability (MSS/MSI-L) and high-level MSI (MSI-H) groups on the basis of multiple molecular and clinicopathologic criteria. Using methylated in tumor (MINT) markers 1, 2, 12, and 31, we stratified 77 primary CRCs into three groups: MINT++ (>2), MINT+ (1-2), and MINT- (0 markers methylated). The MSS/MSI-L/MINT++ group was indistinguishable from the MSI-H/MINT++ group with respect to methylation of p16(INK4a), p14(ARF), and RIZ1, and multiple morphological features. The only significant difference between MSI-H and non-MSI-H MINT++ cancers was the higher frequency of K-ras mutation (P < 0.004) and lower frequency of hMLH1 methylation (P < 0.001) in the latter. These data demonstrate that the separation of CRC into two nonoverlapping groups (MSI-H versus MSS/MSI-L) is a misleading oversimplification.     

Genetic classification of ovarian carcinoma based on microsatellite analysis: relationship to clinicopathological features and patient survival

Ovarian carcinomas can progress through two pathways of genomic instability: chromosomal instability (CIN) and microsatellite instability (MSI). However, it is unknown whether these two mechanisms could be distinguished from each other in the molecular characteristics in ovarian carcinomas. We hypothesized that these two pathways are not always independent in ovarian carcinomas. We classified 51 ovarian carcinomas based on their MSI and CIN status using microsatellite analysis and assessed whether these carcinogenic pathways affect the clinicopathological features and patient survival. Of the 51 cases, 77.4% of the tumors were microsatellite stable (MSS), 5.9% were MSI-Low (MSI-L) whilst, 16.7% were MSI-High (MSI-H). Overall, 56.8% of the tumors had at least one loss of heterozygosity (LOH) event, i.e., 56.8% CIN. Notably, we identified a significant degree of overlap between the MSI and CIN pathways. Of the 34 tumors with LOH events (CIN), 5 (14.7%) were MSI-H. In addition, of the 7 tumors that were MSI-H, 5 (71.4%) had one or more LOH events (CIN). We also identified a group of 29.4% of all tumors that did not demonstrate any evidence of either of the two pathways of genomic instability as they were MSS/MSI-L with no evidence of LOH events (CIN negative). Furthermore, patients with CIN with MSS/MSI-L have a significantly shorter overall survival compared to those in other genetic categories (P=0.019). Cox regression analysis revealed that tumors with CIN with MSS/MSI-L exhibit a poor prognostic outcome after adjustment for FIGO stage and grade. These findings suggest that some ovarian carcinomas have a significant degree of overlap between the two pathways of genomic instability and that the genetic classification using microsatellite markers may represent a potential new biomarker of risk prediction in ovarian carcinoma.