Microsatellite instability and promoter hypermethylation in colorectal cancer in India

Molecular pathogenesis of microsatellite instability-high early-stage colorectal adenocarcinoma in India

OBJECTIVES

The prevalence of microsatellite instability (MSI) subtype among all colon cancers in India is about 30 %, approximately two times more than that of western population suggesting different molecular pathogeneses.

METHODS

A NanoString analysis-based Pan cancer differential expression (DE) profile was determined in a primary cohort of early-stage CRC (tumor=10, normal=7), and correlated against MSI status. Using RT-PCR, tumor-specific DE genes were validated in another cohort of MSI-high CRC (n=15).

RESULTS

Among the most differentially expressed genes, AXIN2, ETV4, and RNF43 were tumor cell-specific signals, while a set of genes including COL11A1, COMP, INHBA, SPP1, MMP3, TLR2, and others were immune cell-specific signals, that had a differential expression between MSI and MSS groups. When overlapped with The Cancer Genome Atlas (TCGA) studies using the Tumor immune estimation resource tool (TIMER), and protein-protein interaction analysis by STRING.db, these genes were segregated to representative tumor cells and immune cells. On validation, the tumor-specific gene signals were inversely associated with TLR4 expression.

CONCLUSIONS

The differential expression distribution of AXIN2, ETV4, and RNF43 among tumor and immune cells, suggests more than one pathological subset in the MSI-H subgroup of early-stage CRC in the Indian population.

Histopathological Predictors of Microsatellite Instability in Colorectal Cancer-a Tertiary Care Center Experience

Microsatellite instability (MSI) has a therapeutic and prognostic implication in colorectal carcinomas (CRCs). It can be detected either by immunohistochemistry (IHC) or molecular studies. In developing countries, a significant proportion of the patients experience financial constraints limiting the utilization of healthcare facilities. We aimed to identify the possible clinicopathological variables which can be used as predictors of microsatellite instability in such patients. CRC cases received for MSI detection by IHC (for 1 and 1/2 years) were included. A panel of four IHC markers (anti-MLH1, anti-PMS2, anti-MSH2, and anti-MSH6) was used. Confirmation by the molecular study was recommended in all the IHC-proven MSI cases. Various clinicopathological parameters were evaluated as predictors of MSI. Microsatellite instability was detected in 40.6% (30/74) cases with MLH1 and PMS2 dual loss in 27% cases, MSH2 and MSH6 dual loss in 6.8%, loss of all four MMR proteins in 2.7%, and isolated PMS2 loss in 4.1%. MSI-H expression was shown by 36.5% cases with only 4.1% cases showing MSI-L expression. The age cut-off value to differentiate both the study groups (MSI vs MSS) was 63 years with a sensitivity of 47.7% and specificity of 86.7%. ROC curve showed an area under the curve of 0.65 (95% CI, 0.515-0.776; p-value = 0.03). On univariate analysis, age < 63 years, colon site, and absence of nodal metastasis were significantly higher in the MSI group. However, on multivariate analysis, only the age < 63 years was found to be significantly higher in the MSI group. Confirmation was molecular study could only be obtained in 12 cases and was completely concordant with MSI detection by IHC. MSI detection can be performed either by IHC or by molecular study. In this study, no histological parameter appeared to be the independent predictor of MSI status. The age < 63 years might predict the microsatellite instability, yet larger studies are needed for its validation. Thus, we recommend that IHC testing should be performed in all CRC cases.

Pilot Nanostring PanCancer pathway analysis of colon adenocarcinoma in a tertiary healthcare centre in Kerala, India

The prevalence of microsatellite instability and deoxyribonucleic acid mismatch repair deficiency in colorectal adenocarcinoma (CRC) cases is higher in India compared to western populations. No major study on the molecular pathogenesis is currently available in the Indian population. We conducted a pilot study to explore the differences in molecular pathogenesis of microsatellite stable (MSS) and microsatellite unstable CRC from a tertiary care centre in Kerala, South India. Using Nanostring PanCancer panel assay in Stage II colorectal adenocarcinoma, tumour tissues (n = 11) were compared against normal colon tissues (n = 4). Differentially expressed (DE) genes were identified and super-imposed onto colon adenocarcinoma cohort of The Cancer Genome Atlas (TCGA) data (TCGA Colon Adenocarcinoma (TCGA COAD)), from the Genome Expression Profiling Interactive Analysis and Tumor Immune Estimation Resource (TIMER) to compare the gene associations. Significant DE genes were 59 out of 730 (false discovery rate adj. p-value < 0.05), 18 of which had a fold-change |FC(log2)| ≥ 2. On superimposition to TCGA COAD, 33 genes were significant in both TCGA and current study. ETV4 was expressed significantly higher in MSS with no immune cell infiltration. Other significant DE genes with high FC(log2), unique to the study were INHBA, COL1A1, COL11A1, COMP, SFRP4 and SPP1, which were clustered in STRING network analysis and correlated with tumour-infiltrating immune cells in TIMER, suggesting a specific interaction pathway. The preliminary study suggests a distinct pathogenesis of MSS CRC involving ETV4 in the Indian population and warrants further clinically extensive and high-dimensional expression studies.

Prognostic and predictive significance of microsatellite instability in stage II colorectal carcinoma: An 8-year study from a tertiary center in South India

BACKGROUND

Microsatellite instability (MSI) accounts for 15-20% of colorectal cancer (CRC) and is considered to have favorable stage-adjusted prognosis compared to Microsatellite stable (MSS) CRCs. Determination of MSI in stage II CRC is important for management decisions regarding adjuvant chemotherapy administration. The aim of this study was to determine the prognostic and predictive significance of MSI in stage 2 CRC in the Indian scenario.

MATERIALS AND METHODS

A total of 195 patients who underwent curative surgery for stage II CRC from 2010 to 2017 were included. MSI testing by immunohistochemistry (DNA MisMatch Repair proteins) was performed in all. Various clinicopathological factors and disease-free survival and overall survival were assessed between MSI and MSS groups. The effect of treatment in terms of survival benefits with adjuvant therapy in the MSI group was also assessed.

RESULTS

27.1% of the CRCs' showed MSI. Younger age (<50 years), family history of cancer, synchronous/metachronous malignancies, proximal (right sided) location, poor morphological tumour differentiation, mucin production, and presence of peritumoral (Crohn's-like) lymphocytic response showed statistically significant association with MSI. Majority (56%) of our patients showed combined loss of MLH1 and PMS2. Overall, survival among the MSI patients was significantly higher (76.6 ± 4.149 months) than the MSS patients (65.05 ± 3.555)P= 0.04. MSI patients did not show any differences in survival with or without treatment.

CONCLUSION

This study highlights the distinct clinicopathological features of MSI-related CRC and the relevance of MSI testing of stage II CRC for management decisions and prognostication.

Prevalence estimation of microsatellite instability in colorectal cancers using tissue microarray based methods - A tertiary care center experience

Aim

Microsatellite instability (MSI) pathway is known to be implicated in carcinogenesis of 15% colorectal carcinomas (CRC), including 2%-3% of cases of Lynch syndrome, as per western literature. MSI status has important prognostic and therapeutic implications. The prevalence of MSI in Indian CRC patients is unknown. We aimed to determine the prevalence by studying 231 consecutive unselected cases of CRC.

Methods

Tissue microarrays using duplicate cores per case for 141 cases, and whole tissue sections for 90 cases, were used. Immunohistochemistry with four mismatch repair (MMR) markers - MLH1, MSH2, MSH6, and PMS2 was performed. Molecular analysis for MSI status was performed in 18 randomly selected cases. Correlation with various clinical and histopathological features was done using univariate and multivariate analysis.

Results

Loss of MMR immunohistochemical (IHC) was seen in 53/231 cases, i.e. 22.94% (95% confidence interval 17.52%-28.36%). MLH1-PMS2 dual loss comprised 13.9%, MSH2-MSH6 7.4%, and isolated PMS2 loss in 1.73% of cases. Univariate analysis showed significant association with age (<60 years), right-sided tumor location, histologic type, high grade, the presence of severe intratumoral lymphocytic (ITL) and peri-tumoral lymphocytic response, and N0 nodal stage. On multivariate analysis, independent variables were age < 60 years, right-sided location, and severe ITL. Molecular testing for MSI corroborated with the IHC results.

Conclusion

The study results show a slightly higher prevalence of MSI-H phenotype, compared to Western literature, stressing the need for more widespread testing for better clinical management and identification of possible hereditary colon cancer syndrome.

Relationship Between Human mutL Homolog 1 (hMLH1) Hypermethylation and Colorectal Cancer: A Meta-Analysis

Background

Hypermethylation of CpG islands in gene promoter regions is an important mechanism of gene inactivation in cancers. Promoter hypermethylation of human mutL homolog 1 (hMLH1) has been implicated in a subset of colorectal cancers that show microsatellite instability (MSI), while the connection of the epigenetic inactivation of hMLH1 in colorectal cancers remains unknown. The aim of this study was to evaluate the relationship between the promoter hypermethylation of hMLH1 and colorectal cancers by performing a meta-analysis.

Material/Methods

Eligible studies were identified through searching PubMed, Cochrane Library, Web of Science, and Google Scholar databases. R Software including meta packages was used to calculate the pooled and odds ratios (ORs) with corresponding confidence intervals (CIs). Funnel plots were also performed to evaluate publication bias.

Results

This meta-analysis obtained 45 articles, including 4096 colorectal cancer patients, and identified a significant association between hMLH1 hypermethylation and colorectal cancer risk using the fixed-effects model (OR=8.3820; 95% CI, 6.9202~10.1527; z=21.7431; P<0.0001) and random effects model pooled (OR=10.0963; 95% CI, 6.1919~16.4626; z=9.2688; P<0.0001). The significant relationship was found in subgroup analyses.

Conclusions

The results of this meta-analysis show a significant association between hMLH1 hypermethylation and colorectal cancer risk.

ZNRF3 is downregulated in papillary thyroid carcinoma and suppresses the proliferation and invasion of papillary thyroid cancer cells

Zinc and ring finger 3 (ZNRF3) is a transmembrane E3 ubiquitin ligase that has emerged as an important regulator of cancer development; however, its cancer-related function remains controversial. Here, we investigated the possible role of ZNRF3 in thyroid carcinoma (TC). We found that ZNRF3 is downregulated in papillary thyroid carcinoma (PTC) compared to normal thyroid tissues and inversely correlated with the degree of cell differentiation. Overexpression of ZNRF3 significantly suppressed cell malignant behaviors, including cell proliferation, migration, and invasion in vitro, as well as tumor growth in vivo. Consistent with recent studies showing that ZNRF3 is involved in the Wnt/β-catenin pathway, ZNRF3 overexpression negatively regulated β-catenin activation, modulating PTC cell behaviors. Clinical specimens revealed a significant inverse correlation between ZNRF3 and β-catenin mRNA levels. Taken together, these results provide insight into a potential tumor suppressor role of ZNRF3 in PTC progression, and may have potential clinical relevance for the prognosis and treatment of PTC.