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

Comparison of Microsatellite Instability With Clinicopathologic Data in Patients With Colon Adenocarcinoma

Background Microsatellite instability (MSI) is a genetic condition caused by errors in DNA repair genes that cause colorectal cancer (CRC). The literature contradicts the frequency of MSI in sporadic CRCs and its effect on prognosis. This study investigated the distribution of clinicopathologic features and the relationship between MSI and survival outcomes. Methodology This is a retrospective study of 101 consecutive cases of CRC and immunohistochemical studies. All cases were retrospectively reviewed and reevaluated by histological grade, lymphovascular invasion, perineural invasion, tumor borders, dirty necrosis, tumor-infiltrating lymphocytes (TILs), Crohn's-like lymphoid reaction, mucinous and medullary differentiation, and tumoral budding from pathological slides. An immunohistochemical study was performed in appropriate blocks for using MLH-1, MSH-2, MSH-6, and PMS-2. We collected the clinical stage, pathological tumor stage, lymph node metastasis, age, sex, tumor diameter, distant metastasis, localization, and survival information from patients' clinical data. Results There was no statistically significant difference between the two groups regarding age, gender, tumor diameter, histological grade, tumor border, dirty necrosis, TILs, N and M stage, perineural and lymphovascular invasion, mucinous differentiation, medullary differentiation, and tumor budding characteristics of the patients. The MSI-H group was more frequently located in the right colon and transverse colon (p < 0.001), and the T stage was higher among them than in the MSI-L group (p = 0.014). Upon multivariate regression analysis, MSI status had no significant effect on survival time. Age and stage N and M were independent prognostic factors for colon cancer prognosis. Conclusions Our study presented the distribution of clinicopathological features and their relationship with MSI for 101 regional CRC patients. MSI status was detected by immunohistochemistry. Identifying MSI in CRCs may help personalize therapy planning. As the distribution of the features may vary from population to population, further investigations are needed on this topic.

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.

Evaluating morphological features for predicting microsatellite instability status in colorectal cancer

Background

Colorectal cancer (CRC) is one of the commonest cancers worldwide, with incidence rates in India being around 4%. It is a heterogeneous disease with multiple established prognostic factors. Ten to fifteen percent originate from microsatellite instability (MSI) pathway, characterized by defect in mismatch repair (MMR) gene. Identification of MMR defective protein is relevant for diagnosis, prognosis, and prediction. Certain clinical and histological features are known to be associated with defective MMR genes. The objectives of this study are to find the prevalence of MSI in CRC to identify features associated with MSI and assess the value of histopathology in predicting MSI.

Methods

We evaluated various clinical and histological parameters for identifying prognostically favorable colon cancers in a tertiary hospital. One hundred fifty colon cancers were evaluated, and MSI status was correlated with clinicopathologic variables.

Results

The prevalence of MSI in CRC was found to be 11.3%. The factors associated with MSI were tumor differentiation, stage, tumor site, tumor size, tumor-infiltrating lymphocytes, Crohn's-like lymphoid reaction, and dirty necrosis. We have defined a "P" score for prediction of MSI using the clinicohistological parameters, which could be used to select patients who are to be tested for MSI.

Conclusion

Assessment of clinical and histopathological features will help in patient stratification and selection of patients for MSI testing. The evaluation is economical, reproducible, and easy to apply.

Immunohistochemical screening for mismatch repair protein deficiency in paediatric high-grade gliomas - institutional experience and review of literature

PURPOSE

Immunohistochemical (IHC) testing for mismatch repair (MMR) deficiency (MMRD) is used as a screening tool to identify microsatellite instability in various cancers (especially colon). This not only identifies hereditary cancer syndromes like Lynch and constitutional mismatch repair deficiency (CMMRD) but also aids in prognostication and prediction of sensitivity to checkpoint inhibitor drugs. There are very few reported studies on MMRD status of pediatric high-grade gliomas (pHGG) and none from the Indian subcontinent. The aim of this study is to evaluate the frequency of MMRD in pHGG and to assess if there is a need for universal screening with immunohistochemistry.

METHODS

Paraffin blocks of consecutive cases of pHGG (< 18 years) were retrieved from 2 centres, and IHC with four MMR antibodies - MLH1, PMS2, MSH2 and MSH6 - was performed using tissue microarray-based technique.

RESULTS

Three out of nine cases (33%) studied showed loss of staining. One case had loss of MSH2 and MSH6 confirmed by gene sequencing. Eight of the cases were glioblastoma. One case of IDH1-mutated anaplastic astrocytoma showed loss of MLH1 and PMS2 staining. Isolated PMS2 loss was noted in 1 case, where the non-tumour cells also showed loss of staining, indicative CMMRD syndrome. This patient had prior colon cancer with isolated PMS2 loss and responded to check-point inhibitor therapy with nivolumab.

CONCLUSION

Our study shows that the frequency of MMRD to be about one-third of pHGG. Universal IHC screening for MMRD in all pHGGs may benefit early diagnosis and play a role in therapeutic decisions. A larger multi-institutional study will help better assess the prevalence and treatment implications in MMRD tumours.

Co-inhibitor expression on tumor infiltrating and splenic lymphocytes after dual checkpoint inhibition in a microsatellite stable model of colorectal cancer

Checkpoint inhibitors have demonstrated clinical impact in colorectal cancer with deficient mismatch repair and high microsatellite instability. However, the majority of patients have disease with stable microsatellites that responds poorly to immunotherapies. Combinations of checkpoint inhibitors are under investigation as a way of increasing immunogenicity and promoting a robust anti-tumor immune response. The purpose of this study is to quantify the immune responses induced by mono and dual checkpoint inhibition in a mismatch repair proficient model of colorectal cancer (CRC). Tumor growth rates were monitored over time and compared between groups. We utilized fluorescence-activated cell sorting to analyze CD8⁺ and CD4⁺ T cells after treatment with either single PD-1 inhibition or dual PD-1 and CTLA-4 inhibition. Additionally, we sought to quantify the expression of co-inhibitory surface molecules PD-1, LAG3, and TIM3. Dual checkpoint inhibition was associated with a significantly slower growth rate as compared to either mono PD-1 inhibition or control (p < 0.05). Neither monotherapy nor dual checkpoint inhibition significantly affected the tumoral infiltration of lymphocytes. After treatment with dual inhibitors, infiltrating CD8⁺ T cells demonstrated significantly less expression of PD-1 (1700 vs. 2545 and 2462; p < 0.05) and LAG3 (446.2 vs. 694.4 and 707; p < 0.05) along with significantly more expression of TIM3 (12,611 vs. 2961 and 4259; p < 0.05) versus the control and anti-PD-1 groups. These results suggest that dual therapy with anti-CTLA-4 and anti-PD-1 antibodies significantly inhibits growth of microsatellite stable CRC by suppressing immunosuppressive checkpoints. Upregulation of TIM3 represents a potential escape mechanism and a target for future combination immunotherapies in CRC.

Mismatch repair deficiency occurs very rarely in seminomas

Background

Dense tumor-associated lymphocyte infiltration is linked to mismatch repair (MMR) deficiency in colorectal and endometrial cancer. MMR deficiency is of high clinical importance as MMR deficient cancers tend to react favorably to treatment with immune checkpoint inhibitors. Strong lymphocytic infiltration is a morphological hallmark of seminomas. We thus asked whether seminomas may exhibit MMR deficiency at relevant frequency.

Methods

To screen for tumors with MMR deficiency, protein expression of MLH1, PMS2, MSH2, and MSH6 was analyzed by immunohistochemistry (IHC) on a tissue microarray (TMA) containing 574 seminomas.

Results

In total, 536 cases were evaluable resulting in 481 seminomas with unequivocally intact MMR protein expression. In 55 cancers, one or several IHC stains were equivocal and lacked detectable MMR protein in both tumor and stromal cells. Large section IHC analysis of all 55 equivocal cases demonstrated substantial staining issues due to improper fixation in 54 cases and identified one tumor with clear-cut MLH1 and PMS2 protein loss. This seminoma showed homogeneous loss of MLH1 and PMS2 in the entire tumor mass whereas minor adjacent foci of associated germ cell neoplasia in situ (GCNIS) were MMR intact. Polymerase chain reaction (PCR) analysis using the 5 microsatellite loci of the “Bethesda Panel” revealed instability in 1 of 4 interpretable loci (“MSI-low”) and additional instability of the complex tetra-penta repeat locus MYCL1 in this tumor.

Conclusions

In summary, one single seminoma with MMR deficiency, characterized by protein loss of MLH1 and PMS2, was identified among 536 interpretable seminomas (0.19%). MMR deficiency is not a relevant determinant of lymphocyte influx in seminoma.

Identification of colorectal cancers with defective DNA damage repair by immunohistochemical profiling of mismatch repair proteins, CDX2 and BRCA1

Colorectal cancer (CRC) is a complex disease as shown by consensus classification. The present study attempted to identify subtypes with known prognostic markers for better clinical management. A total of 72 CRC tumors were examined for the expression of mismatch repair (MMR) proteins, along with caudal-type homeobox protein 2 (CDX2) and BRCA1, by immunohistochemistry. Tumors were assigned based on the presence or loss of MMR proteins as proficient or deficient. Correlations were examined with CDX2 and BRCA1 along with clinico-pathological features. Expressional pattern of microRNAs (miRs/miRNAs), such as miR-183-96-182, known to be associated with defective DNA damage repair were evaluated by reverse transcription-quantitative PCR. A total of 22% of the CRC tumors were assigned as deficient in mismatch repair. 71% of the tumors expressed CDX2 while only 21% had nuclear expression of BRCA1. Loss of CDX2 protein was higher in the deficient subtype compared with the proficient subtype. A total of 14% of the tumors had dual loss of MMR and BRCA1 proteins and showed aggressive clinical features in addition to elevated expression of DNA damage repair microRNAs. The present study shows the presence of a small proportion of colorectal tumors with dual loss of key proteins involved in DNA damage repair which may be amenable to specific therapy. The implication of the present observations warrants investigation in a larger patient cohort with prognostic information.

Response to Immunotherapy in Combination With Mitotane in Patients With Metastatic Adrenocortical Cancer

Adrenocortical carcinoma (ACC) is a rare orphan disease with a dismal prognosis. Surgery remains the first-line treatment, but most patients eventually develop metastatic disease. Mitotane is often used with chemotherapy with modest success. Little information is available concerning the efficacy of immunotherapy in combination with mitotane. We conducted a retrospective review of our initial six patients with metastatic ACC, for whom mitotane alone or with chemotherapy failed, and who were subsequently treated with a combination of pembrolizumab and mitotane, between July 2016 and March 2019. Imaging was analyzed per Response Evaluation Criteria in Solid Tumours 1.1 criteria. Two patients had a partial response and four patients had stable disease (8 to 19 months). One patient had grade 3 hepatitis and pembrolizumab was discontinued after 8 months. She died with disease progression 16 months after initiating pembrolizumab. One patient developed brain metastasis after 19 months of treatment and was transitioned to hospice. One patient had focal pneumonitis after 18 months of treatment, and pembrolizumab was discontinued. Three remaining patients continue pembrolizumab plus mitotane at the time of this writing. The current standard of care for ACC is a combination of etoposide, doxorubicin, cisplatin, and mitotane with an overall survival of 14.8 months. All six patients lived for at least 16 months after starting pembrolizumab added to mitotane therapy. The therapy appeared to be effective in both microsatellite instability-high and microsatellite stable tumors, suggesting some synergistic effect with mitotane. Combined immunotherapy and mitotane should be considered in future clinical trials in patients with ACC.