Immunohistochemistry versus microsatellite instability testing for screening colorectal cancer patients at risk for hereditary nonpolyposis colorectal cancer syndrome. Part I. The utility of immunohistochemistry

Outcome of chemotherapy with or without targeted agents in metastatic colorectal cancer patients with deficient DNA mismatch repair: A single center, cohort study

AIMS

Metastatic colorectal cancer (mCRC) with deficient DNA mismatch repair (dMMR) is a rare disease accounting only for 4-5% of the whole mCRC and its optimal treatment still remains unclear. We conducted a retrospective study to evaluate the outcome of chemotherapy with or without bevacizumab or cetuximab in this setting.

METHODS

A total of 729 colorectal cancer patients with dMMR status were screened for eligibility. The Kaplan-Meier method, the log-rank test and Cox analysis were utilized for survival analyses.

RESULTS

A total of 43 patients met the inclusion criteria and enrolled in the study. The median overall survival (OS) of entire cohort was 21.7 months. Chemotherapy plus bevacizumab group exhibited a tendency of substantially higher overall response rate (ORR) than chemotherapy alone group (63.6% vs. 23.8%, P = 0.053), whereas the ORR between chemotherapy plus cetuximab group and chemotherapy alone group were similar (28.6% vs. 23.8%, P = 1.000). Compared with chemotherapy alone group, bevacizumab combined group achieved a significantly longer progression-free survival (10.0 months vs. 4.8 months, P = 0.028), whereas cetuximab combined group was not (6.8 months vs. 4.8 months, P = 0.158). Although the median OS seemed to favor bevacizumab combined group, no significant differences were detected between the three arms (33.7, 21.7 and 15.3 months, respectively; P = 0.345). Prognostic analysis showed that primary tumor resection was the positive prognostic factor of OS (hazards ratio: 0.438; P = 0.041).

CONCLUSION

dMMR mCRC seems resistant to chemotherapy and cetuximab. Bevacizumab combined therapy shows a sign of potentially favorable outcome in this subtype.

Clinical Impact of Mismatch Repair Protein Testing on Outcome of Early Staged Colorectal Carcinomas

INTRODUCTION

Colorectal cancer is the third most common cancer in men and second most common in women globally. In the present study, we aimed to analyse the proportion of patients with loss of immunostaining for mismatch repair (MMR) proteins in all newly diagnosed stage II cases of colorectal cancer for the purpose of prognostication, for determination of further chemotherapeutic strategy and for familial screening.

METHOD

From January 2014 to December 2015, 62 consecutive newly diagnosed cases of stage II colorectal cancer were included in the study. Details of each patient related to their demographic profile and tumour profile were recorded. All the cases were grossed and staged according to College of American Pathologist (CAP) guidelines. The expression of MMR proteins (which was earlier validated on normal as well as tumour tissue) in FFPE tumour tissue using IHC for mut L homologue 1 (MLH1), mut S homologue 2 (MSH2), mut S homologue 6 (MSH6) and post-meiotic segregation increased 2 (PMS2) was studied. Information regarding stage, treatment, clinical outcome and overall survival was retrieved when available.

RESULTS

Out of a total of 371 cases, 62 (16.7%) cases were of stage II CRC, out of which 43 (12%) were treatment naive. Among the selected 62 cases, 26 (41.9%) demonstrated loss of MMR proteins and 36 (58.0%) cases had intact nuclear expression. Out of the cases with MMR loss, 38.4% showed loss of MLH1 and PMS2, 30.7% showed loss of MSH2 and MSH6, 26.9% showed isolated loss of PMS2 and 3.8% showed isolated loss of MSH6. Right-sided location (57.6%) was more common than left-sided (19.2%) and transverse colon (23.0%). Majority of the cases were moderately differentiated (65.3%) in morphology. There was no intratumoural infiltrate in most of the cases (53.8%), and only 3.8% cases showed marked intratumoural infiltrate. Also, peritumoural lymphocytic infiltrate was mild to moderate in most of the cases (26.9%) and marked Crohn's-like infiltrate was seen in only 7.6% cases.

CONCLUSION

Our study shows that the routine evaluation of MMR proteins is achievable and essential for the purpose of prognostication, planning of treatment strategies and ascertaining a hereditary basis of CRC. The incidence of MMR protein loss was quite high in our study compared to other studies probably due to a difference in ethnicity. Though a right-sided predominance was supported, none of the typical morphological features of microsatellite instability (MSI) tumours were substantiated by our study, highlighting the lack of importance of histology for predicting MSI, and emphasising the point that MSI testing should be done as a routine procedure in all stage II CRC. A short follow-up was done for all our cases and comparison between the survival of the chemotherapy treated MSI cases versus those which were treatment naïve was performed and revealed that chemotherapy (CT) did not provide additional benefit to survival; MSI tumours in general are a better prognostic category and do not require additional chemotherapy.

Choroidal Mucinous Metastatic Adenocarcinoma from the Colon: A Diagnostic Challenge

An enucleated globe was submitted from an outside hospital to the Ophthalmic Pathology Laboratory for evaluation. There was a minimal amount of accompanying clinical history. Histopathologic examination revealed a mucinous adenocarcinoma of the choroid. The determination of the origin of the tumor proved to be challenging based on the lack of a definitive systemic diagnosis. Initial suspicions that the tumor may represent a breast carcinoma were disproved when immunohistochemical biomarkers for breast carcinoma were negative. Similarly, typical markers of colon adenocarcinoma were not expressed. Positive immunostaining with a newer immunohistochemical marker, SATB2, and defects in DNA mismatch repair helped to confirm that the ocular metastasis was of colonic origin. Further clinical evaluation including imaging studies established that the patient had a primary colonic adenocarcinoma with widespread systemic metastases. The diagnostic utility and biologic significance of these latest immunohistochemical biomarkers for colon cancer are reviewed. Clinicians are encouraged to provide detailed clinical histories with the tissue specimens to enable the discovery of undetected "silent primaries" at the time an ocular metastasis develops and is discovered.

Epidemiological, clinical and molecular characterization of Lynch-like syndrome: A population-based study

Colorectal carcinomas that are mismatch repair (MMR)-deficient in the absence of MLH1 promoter methylation or germline mutations represent Lynch-like syndrome (LLS). Double somatic events inactivating MMR genes are involved in the etiology of LLS tumors. Our purpose was to define the clinical and broader molecular hallmarks of LLS tumors and the population incidence of LLS, which remain poorly characterized. We investigated 762 consecutive colorectal carcinomas operated in Central Finland in 2000-2010. LLS cases were identified by a stepwise protocol based on MMR protein expression, MLH1 methylation and MMR gene mutation status. LLS tumors were profiled for CpG Island Methylator Phenotype (CIMP) and somatic mutations in 578 cancer-relevant genes. Among 107 MMR-deficient tumors, 81 (76%) were attributable to MLH1 promoter methylation and 9 (8%) to germline mutations (Lynch syndrome, LS), leaving 14 LLS cases (13%) (3 remained unclassified). LLS carcinomas were diagnosed at a mean age of 65 years (vs. 44 years in LS, p < 0.001), had a proximal to distal ratio of 1:1, and all were BRAF V600E-negative. Two somatic events in MMR genes were identifiable in 11 tumors (79%). As novel findings, the tumors contained an average of 31 nonsynonymous somatic mutations/Mb and 13/14 were CIMP-positive. In conclusion, we establish the epidemiological, clinical and molecular characteristics of LLS in a population-based study design. Significantly more frequent CIMP-positivity and lower rates of somatic mutations make a distinction to LS. The absence of BRAF V600E mutation separates LLS colorectal carcinomas from MLH1-methylated colorectal carcinomas with CIMP-positive phenotype.

A practical guide to biomarkers for the evaluation of colorectal cancer

Evaluation of microsatellite instability (MSI) of every colorectal cancer (CRC) is important for prognostic and therapeutic purposes, while molecular testing helps identify actionable targeted therapy for patients with metastatic disease. This review will discuss the biomarkers commonly encountered in the clinical evaluation of CRC, and practical issues regarding MSI screening, reporting, interpretation, molecular test indication, and specimen requirements.

Accurate diagnosis of mismatch repair deficiency in colorectal cancer using high-quality DNA samples from cultured stem cells

Mismatch repair (MMR)-deficient or microsatellite instability (MSI) colorectal cancer includes two subtypes; Lynch syndrome and sporadic MSI cancer, both of which generate multiple neoantigens due to unrepaired mutations. Although such patients respond very well to immune checkpoint therapy, their diagnosis can be confused by low quality DNA samples owing to formalin fixation and/or low cancer cell content. Here we prepared high-quality DNA samples from in vitro-cultured cancer spheroids that consisted of the pure cell population. We evaluated their diagnostic power by on-chip electrophoresis, mutational burden assessment, and direct sequencing. Because formalin-fixed paraffin-embedded (FFPE) tissues are widely used as the DNA source, we compared such samples with spheroid DNA. Additionally, we performed immunohistochemistry (IHC) for MMR proteins on spheroids as well as primary tumor sections. Of 111 cases of colorectal cancer patients, we found seven MSI-high cases in which all diagnostic results agreed on spheroid-based assays, whereas the results with the FFPE DNA were less reliable though analyzable. Importantly, there was an MSS case that appeared as MSI by IHC on primary tumor sections. Based on these results, we propose to employ cultured cancer spheroids as the source of both DNA and IHC specimens for more reliable clinical diagnosis.

Data-Driven Discovery of Immune Contexture Biomarkers

Background: Features characterizing the immune contexture (IC) in the tumor microenvironment can be prognostic and predictive biomarkers. Identifying novel biomarkers can be challenging due to complex interactions between immune and tumor cells and the abundance of possible features. Methods: We describe an approach for the data-driven identification of IC biomarkers. For this purpose, we provide mathematical definitions of different feature classes, based on cell densities, cell-to-cell distances, and spatial heterogeneity thereof. Candidate biomarkers are ranked according to their potential for the predictive stratification of patients. Results: We evaluated the approach on a dataset of colorectal cancer patients with variable amounts of microsatellite instability. The most promising features that can be explored as biomarkers were based on cell-to-cell distances and spatial heterogeneity. Both the tumor and non-tumor compartments yielded features that were potentially predictive for therapy response and point in direction of further exploration. Conclusion: The data-driven approach simplifies the identification of promising IC biomarker candidates. Researchers can take guidance from the described approach to accelerate their biomarker research.

Microsatellite instability test using peptide nucleic acid probe-mediated melting point analysis: a comparison study

Background

Analysis of high microsatellite instability (MSI-H) phenotype in colorectal carcinoma (CRC) is important for evaluating prognosis and choosing a proper adjuvant therapy. Although the conventional MSI analysis methods such as polymerase chain reaction (PCR) fragment analysis and immunohistochemistry (IHC) show high specificity and sensitivity, there are substantial barriers to their use.

Methods

In this study, we analyzed the MSI detection performance of three molecular tests and IHC. For the molecular tests, we included a recently developed peptide nucleic acid probe (PNA)-mediated real-time PCR-based method using five quasi-monomorphic mononucleotide repeat markers (PNA method) and two conventional PCR fragment analysis methods using NCI markers (NCI method) or five quasi-monomorphic mononucleotide repeat markers (MNR method). IHC analysis was performed with four mismatch repair proteins. The performance of each method was validated in 166 CRC patient samples, which consisted of 76 MSI-H and 90 microsatellite stable (MSS) CRCs previously diagnosed by NCI method.

Results

Of the 166 CRCs, 76 MSI-H and 90 MSS CRCs were determined by PNA method. On the other hand, 75 MSI-H and 91 MSS CRCs were commonly determined by IHC and MNR methods. Based on the originally diagnosed MSI status, PNA showed 100% sensitivity and 100% specificity while IHC and MNR showed 98.68% sensitivity and 100% specificity. When we analyzed the maximum sensitivity of MNR and PNA method, which used the same five markers, PNA method could detect alterations in all five mononucleotide repeat markers in samples containing down to 5% MSI-H DNAs, whereas MNR required at least 20% MSI-H DNAs to achieve the same performance.

Conclusions

Based on these findings, we suggest that PNA method can be used as a practical laboratory test for the diagnosis of MSI.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5127-6) contains supplementary material, which is available to authorized users.

Recent Advances in the Clinical Development of Immune Checkpoint Blockade Therapy for Mismatch Repair Proficient (pMMR)/non-MSI-H Metastatic Colorectal Cancer

Metastatic colorectal cancer (mCRC) continues to be associated with a poor prognosis, and there remains a significant unmet need for novel agents and treatment regimens. Major breakthroughs have been made with immune checkpoint blockade therapy in several disease types, including DNA mismatch repair deficient/microsatellite instability-high (MSI-H) tumors. To date, however, immune checkpoint monotherapy has not shown significant clinical activity in the treatment of patients with mismatch repair proficient (pMMR)/non-MSI-H mCRC. The immune resistance mechanisms in pMMR/non-MSI-H mCRC have not yet been clearly elucidated. Significant efforts are currently focused on identifying effective combination immunotherapy regimens for the treatment of patients with pMMR/non-MSI-H mCRC. The combination of atezolizumab with cobimetinib had shown promising clinical activity in an early-phase clinical trial. Unfortunately, the IMblaze 370 (COTEZO) phase III trial of atezolizumab/cobimetinib combination in patients with mCRC failed to show significant improvement in overall survival in patients treated with the atezolizumab/combimetinib combination in comparison with regorafenib alone. This review summarizes the recent major advances in the clinical development of immunotherapy regimens for patients with pMMR/non-MSI-H mCRC.

Validation of a targeted next-generation sequencing approach to detect mismatch repair deficiency in colorectal adenocarcinoma

Mismatch repair protein deficiency is a hallmark of cancers associated with Lynch syndrome and is a biomarker for response to immunotherapy. With the increasing adoption of cancer next-generation sequencing, there has been a movement to develop screening approaches that take advantage of the unique mutational signatures of mismatch repair-deficient tumors. Here, we develop a sequencing-based metric that distinguishes mismatch repair-deficient from mismatch repair-proficient colorectal adenocarcinomas with comparison to immunohistochemical staining. We find that a single criterion of three or more single base pair insertion or deletion mutations per megabase sequenced, occurring in mononucleotide repeat regions of four or more nucleotides, is sufficient to detect mismatch repair deficiency with 96% sensitivity and 100% specificity in a training set of 241 cancers and 96% sensitivity and 99% specificity in a validation set of 436 additional cancers. Using data from the same cohort, we also find that sequencing information from only three genes-ARID1A, KMT2D, and SOX9-is sufficient to detect mismatch repair-deficient colorectal adenocarcinomas with 76% sensitivity and 98% specificity in the validation set. These findings support the notion that targeted next-generation sequencing already being performed for clinical or research purposes can also be used to accurately detect mismatch repair deficiency in colorectal adenocarcinomas.

Evaluation of Long-Term Outcomes of Microsatellite Instability Status in an Asian Cohort of Sporadic Colorectal Cancers

PURPOSE

Microsatellite instability in colorectal cancer (CRC) and its long-term outcomes remains poorly studied in Asians. We investigate the prognostic significance of microsatellite instability in an Asian population and assess its clinical impact in patients who undergo adjuvant chemotherapy.

METHODS

Six hundred fifty-four consecutive CRC patients who underwent surgical resection between January 2010 and December 2012 were recruited. Survival was estimated using the Kaplan-Meier approach. Univariate Cox proportional hazard models were used to estimate the hazard ratios for variables associated with survival. A subgroup analyses was performed for stage III patients who underwent chemotherapy to evaluate the prognostic significance of microsatellite instability in this group.

RESULTS

Five hundred ninety-one (90.4%) patients were microsatellite stable (MSS) while 63 (9.6%) were microsatellite instable (MSI). Three years recurrence-free survival (RFS) and disease-specific survival (DSS) were 83.7 versus 73.7% (p = 0.295) and 87.1 versus 91.2% (p = 0.307) in MSS and MSI tumors, respectively. Among stage III patients who received adjuvant therapy, MSI status was found to be an adverse prognostic factor for RFS (HR 2.74 (95% CI 1.43-5.26), p = 0.002). This remained significant on multivariate analysis (HR 2.38 (95% CI 1.15-4.93), p = 0.018). Adjuvant chemotherapy was associated with survival benefit for patients with MSS tumors (HR 0.35, 95% CI 0.17-0.69, p = 0.002) but not MSI tumors (HR 0.67, 95% CI 0.08-8.15, p = 0.750).

CONCLUSIONS

MSI status is not a prognostic indicator in the general CRC population but appears to be an adverse prognostic indicator for RFS in stage III CRC patients who received adjuvant chemotherapy.

Assessing colorectal cancer mismatch repair status in the modern era: a survey of current practices and re-evaluation of the role of microsatellite instability testing

Results of DNA mismatch repair testing are used to detect Lynch syndrome and have prognostic and therapeutic implications among patients with sporadic colorectal carcinomas. Immunohistochemistry for mismatch repair proteins (MLH1, PMS2, MSH2, MSH6) and PCR for microsatellite instability are two established methods for assessing mismatch repair function. Older literature suggested a discordance rate of approximately 5% between these assays, leading some institutions to perform dual testing on all cases. Although universal mismatch repair testing is now recommended by multiple professional organizations, none provide guidelines regarding preferred assays. We surveyed 96 academic and nonacademic institutions to assess Lynch syndrome screening practices and evaluated discordance rates between immunohistochemistry and PCR among 809 colorectal cancers tested in our own institution. Our survey demonstrated no significant differences between academic and nonacademic practices with respect to testing strategies. Eighty six percent performed universal screening, and usually (76%) employed immunohistochemistry on initial biopsy samples. Only 20% employed PCR; these were mostly academic practices that used both immunohistochemistry and PCR (p < 0.01 compared with the nonacademic groups). Loss of MLH1/PMS2 staining was often (90%) followed by either BRAF mutational analysis or MLH1 methylation assays. Only 24% adhered to WHO recommendations to assign histologic grade based on mismatch repair status. We found only 3 cases (0.4%) with discordant immunohistochemistry and PCR results in our own practice: 1 reflected decreased MSH-6 staining in a neoadjuvantly treated microsatellite stable tumor, 1 MLH1-deficient tumor showed diminished MLH1/PMS2 in the tumor compared with internal control, and 1 case reflected an error in the molecular laboratory. Overall, our results showed extremely low discordance between methods assessing mismatch repair status and would suggest immunohistochemistry as the preferred single screening test. PCR can be reserved for cases that show equivocal immunostaining patterns.

Mismatch repair deficiency assessment by immunohistochemistry: for Lynch syndrome screening and beyond

While mismatch repair (MMR) deficiency has been studied extensively, the assessment of MMR status in colorectal and other cancers remains highly relevant, particularly in light of recent data demonstrating that MMR deficiency is a strong predictor for treatment benefit with immune checkpoint inhibitors across multiple tumor types. In colorectal cancer, there is a growing consensus in support of routine MMR testing for Lynch syndrome screening, to inform prognosis and adjuvant chemotherapy use in early stage disease, and to predict response to immunotherapy in advanced disease. Here, we provide a review of the Ventana MMR Immunohistochemistry Panel, which was recently approved by the US FDA for use in Lynch syndrome screening.

Microsatellite Instability Is Associated With the Presence of Lynch Syndrome Pan-Cancer

PURPOSE

Microsatellite instability (MSI) and/or mismatch repair deficiency (MMR-D) testing has traditionally been performed in patients with colorectal (CRC) and endometrial cancer (EC) to screen for Lynch syndrome (LS)-associated cancer predisposition. The recent success of immunotherapy in high-frequency MSI (MSI-H) and/or MMR-D tumors now supports testing for MSI in all advanced solid tumors. The extent to which LS accounts for MSI-H across heterogeneous tumor types is unknown. Here, we establish the prevalence of LS across solid tumors according to MSI status.

METHODS

MSI status was determined using targeted next-generation sequencing, with tumors classified as MSI-H, MSI-indeterminate, or microsatellite-stable. Matched germline DNA was analyzed for mutations in LS-associated mismatch repair genes ( MLH1, MSH2, MSH6, PMS2, EPCAM). In patients with LS with MSI-H/I tumors, immunohistochemical staining for MMR-D was assessed.

RESULTS

Among 15,045 unique patients (more than 50 cancer types), LS was identified in 16.3% (53 of 326), 1.9% (13 of 699), and 0.3% (37 of 14,020) of patients with MSI-H, MSI-indeterminate, and microsatellite-stable tumors, respectively ( P < .001). Among patients with LS with MSI-H/I tumors, 50% (33 of 66) had tumors other than CRC/EC, including urothelial, prostate, pancreas, adrenocortical, small bowel, sarcoma, mesothelioma, melanoma, gastric, and germ cell tumors. In these patients with non-CRC/EC tumors, 45% (15 of 33) did not meet LS genetic testing criteria on the basis of personal/family history. Immunohistochemical staining of LS-positive MSI-H/I tumors demonstrated MMR-D in 98.2% (56 of 57) of available cases.

CONCLUSION

MSI-H/MMR-D is predictive of LS across a much broader tumor spectrum than currently appreciated. Given implications for cancer surveillance and prevention measures in affected families, these data support germline genetic assessment for LS for patients with an MSI-H/MMR-D tumor, regardless of cancer type or family cancer history.

A novel panel of short mononucleotide repeats linked to informative polymorphisms enabling effective high volume low cost discrimination between mismatch repair deficient and proficient tumours

Somatic mutations in mononucleotide repeats are commonly used to assess the mismatch repair status of tumours. Current tests focus on repeats with a length above 15bp, which tend to be somatically more unstable than shorter ones. These longer repeats also have a substantially higher PCR error rate, and tests that use capillary electrophoresis for fragment size analysis often require expert interpretation. In this communication, we present a panel of 17 short repeats (length 7-12bp) for sequence-based microsatellite instability (MSI) testing. Using a simple scoring procedure that incorporates the allelic distribution of the mutant repeats, and analysis of two cohort of tumours totalling 209 samples, we show that this panel is able to discriminate between MMR proficient and deficient tumours, even when constitutional DNA is not available. In the training cohort, the method achieved 100% concordance with fragment analysis, while in the testing cohort, 4 discordant samples were observed (corresponding to 97% concordance). Of these, 2 showed discrepancies between fragment analysis and immunohistochemistry and one was reclassified after re-testing using fragment analysis. These results indicate that our approach offers the option of a reliable, scalable routine test for MSI.

Microsatellite Instability: A Predictive Biomarker for Cancer Immunotherapy

Immunotherapy has shown promising results in various types of cancers. Checkpoint inhibitor drugs developed for cancer immunotherapy have been approved by the US Food and Drug Administration (FDA) for patients with advanced melanoma, non-small cell lung cancer, renal cell carcinoma, bladder cancers, and refractory Hodgkin lymphoma. In the latest announcement, the FDA has granted accelerated approval to pembrolizumab for pediatric and adult patients with microsatellite instability-high (MSI-H) or mismatch repair-deficient solid tumors. This is the first time the agency has approved a cancer treatment based on a common biomarker rather than organ-based approach. MSI-H, either due to inherited germline mutations of mismatch repair genes or epigenetic inactivation of these genes, is found in a subset of colorectal and noncolorectal carcinomas. It is known that MSI-H causes a build up of somatic mutations in tumor cells and leads to a spectrum of molecular and biological changes including high tumor mutational burden, increased expression of neoantigens and abundant tumor-infiltrating lymphocytes. These changes have been linked to increased sensitivity to checkpoint inhibitor drugs. In this mini review, we provide an update on MSI-related solid tumors with special focus on the predictive role of MSI for checkpoint immunotherapy.

Performance of tumor testing for Lynch syndrome identification in patients with colorectal cancer: A retrospective single-center study

Objective:

To investigate the performance of tumor testing approaches in the identification of Lynch syndrome (LS) in a single-center cohort of people with colorectal cancer (CRC).

Methods:

A retrospective analysis of data stored in a dedicated database was carried out to identify patients with CRC suspected for LS who were referred to Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy, between 1999 and 2014. The sensitivity and specificity of immunohistochemistry (IHC) for mismatch repair (MMR) proteins and microsatellite instability (MSI) analysis (alone or combined) were calculated with respect to the presence of causative MMR germline variants.

Results:

A total of 683 patients with CRC suspected for LS were identified. IHC results of MMR protein analysis and MSI were assessed in 593 and 525 CRCs, respectively, while germline analysis was performed in 418 patients based on the IHC or MSI test result and/or clinical features. Univariate and multivariate analysis revealed a significant correlation of pathogenic MMR germline variants with all clinicopathologic features including Amsterdam criteria, presence of endometrial cancer, CRC site, age at onset, stage, and grade. The highest odds ratio values were observed for IHC and MSI (17.1 and 8.8, respectively). The receiver operating characteristic curve and area under the curve values demonstrated that IHC alone or combined with other clinicopathologic parameters was an excellent test for LS identification.

Conclusions:

This study confirms the effectiveness of tumor testing to identify LS among patients with CRC. Although IHC and MSI analysis were similarly effective, IHC could be a better strategy for LS identification as it is less expensive and more feasible.

Frequency of Defective Mismatch Repair System in a Series of Consecutive Cases of Colorectal Cancer in a National Cancer Center

BACKGROUND

The frequency of colorectal cancer (CRC) with defective mismatch repair (dMMR) is estimated between 5 and 15%. In our population, the frequency of dMMR is unknown. Our objective was to show the frequency of dMMR.

METHODS

Determination of dMMR with immunohistochemistry was performed prospectively for 202 patients who presented consecutively with CRC for the first time at our institution.

RESULTS

The median age was 59 years (IQR 47 to 68), 119 (58.9%) were women, and 43 (21.3%) cases showed dMMR. The only clinicopathological characteristics associated with dMMR were the location in the right colon and the presence of a family history of cancer. In the multivariate analysis, only the presence of the tumor in the right colon was associated with dMMR (OR = 5.823, 95%-C.I. = 2.653-12.784, p < .001).

CONCLUSION

The 21.3% of the cases demonstrated a dMMR and the only clinical-pathological characteristic associated with dMMR was location in the right colon.

Molecular characteristics of colorectal cancer in a Middle Eastern population in a single institution

BACKGROUND

The few studies of the molecular biology of colorectal cancer (CRC) in Middle Eastern populations have included only small samples of patients.

OBJECTIVE

Evaluate the frequency and prognostic effect of RAS, BRAF, PIK3CA, PTEN, and EGFR somatic mutations as well as mismatch repair (MMR) deficiency in Lebanese Middle Eastern patients.

DESIGN

Retrospective single-center descriptive study.

SETTING

Lebanese Middle Eastern patients in a tertiary medical cen.ter.

METHODS

We included all patients diagnosed with CRC between January 2010 and December 2015, in whom RAS mutational status and the expression of MLH1 and MSH2 proteins were available.

MAIN OUTCOME MEASURES

Genetic mutations detected by direct sequencing while MMR protein expression was evaluated by immunohistochemistry.

SAMPLE SIZE

645 patients.

RESULTS

RAS, BRAF, EGFR, PI3KCA, and PTEN mutation rates were 38.5%,12.9%, 0%, 11.1% and 0% respectively. The MMR deficiency rate was 20.6%. No factor was associated with RAS mutation whereas MMR-deficient tumors were less likely to be metastatic at diagnosis. Among patients with wild-type RAS females fared better than males (median overall survival [OS]=1734 vs 1079 days respectively, P=.015) even after adjustment for confounding factors by Cox regression analy.sis. This finding was not reproduced in the RAS-mutated group. The median OS of patients with MMR-deficient tumors was not reached, while the median OS was 2475 days in patients who had maintained expression of both MLH1 and MSH2.

CONCLUSION

The RAS mutation rate was similar to Western and East Asian countries, but not for the BRAF mutation and MMR deficiency. We also found a prognostic effect for sex in the RAS wild-type group, a finding worthy of further exploration.

LIMITATIONS

Retrospective, single center and small sample size. Expression of MSH6 and PMS2 not analyzed.

CONFLICT OF INTEREST

None.

Advantage of HSP110 (T17) marker inclusion for microsatellite instability (MSI) detection in colorectal cancer patients

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. Microsatellite instability (MSI) is a genetic pathway leading to CRC, associated with particular clinicopathological features, and recently a major biomarker of immunotherapy response. There is little information the frequency MSI among Brazilian CRC patients, and it is still debatable the ideal methodology for MSI screening in countries with limited resources. We proposed to evaluate MSI by molecular and immunohistochemistry (IHC) methods, to compare both methodologies and also to assess the inclusion of a novel microsatellite marker, HSP110 (T17). The molecular MSI evaluation was performed using a PCR-multiplex panel in a total of 1013 CRC patients. Mismatch repair (MMR) proteins (MLH1, MSH2, MSH6 and PMS2) expression were evaluated by IHC. HSP110 (T17) marker was analyzed by fragment analysis. Molecularly, 89.5% of cases were MSI-negative and 10.5% were MSI-positive. The IHC showed that 88.9% of cases exhibited MMR-proficient status, 10.2% were MMR-deficient and 0.9% was inconclusive. Genotyping of the HSP110 (T17) in 106 MSI-positive and 215 MSI-negative cases showed its alteration only among the MSI-positive cases. We observed agreement (0.956, Kappa Test) between both molecular and IHC methodologies, with only eight discordant results, and in this subset of cases the HSP110 (T17) corroborate the molecular findings. This study suggests the use of molecular assays over IHC for MSI analysis and proposes the inclusion HSP110 (T17) marker as a complementary analysis in discordant cases.

Expending Role of Microsatellite Instability in Diagnosis and Treatment of Colorectal Cancers

Background

Colorectal carcinomas with high-frequency microsatellite instability (MSI-H) account for 15% of all colorectal cancers, including 12% of sporadic cases and 3% of cancers associated with Lynch syndrome (also known as hereditary nonpolyposis colorectal cancer syndrome, HNPCC). Lynch syndrome is an autosomal dominant hereditary cancer syndrome, caused by germline mutations in mismatch repair genes, including MLH1, MSH2, MSH6 and PMS2.

Methods

Published articles from peer-reviewed journals were obtained from PubMed, Google Scholar and Clinicaltrials.gov. Based on the recent research data, we provide an update on the MSI testing, along with the evolving role of MSI in diagnosis, prognosis and treatment of colorectal cancers.

Results

Studies have led to significant advances in the molecular pathogenesis and clinicopathological characteristics of MSI-H colorectal cancers. Emerging evidence suggests that colorectal cancers with MSI-H show different outcome and treatment response from those with microsatellite stable (MSS) tumors. Therefore, MSI testing is essential not only in the genetic context, but it may also have important prognostic and predictive value of response to chemotherapy and immunotherapy.

Conclusions

Many experts and professional authorities have recommended a universal MSI testing in all individuals newly diagnosed with colorectal cancers.

The Importance of Distinguishing Sporadic Cancers from Those Related to Cancer Predisposing Germline Mutations

Choosing the optimal therapy for a patient's cancer has long been based on whether the cancer demonstrates a predictive marker of efficacy. The U.S. Food and Drug Administration (FDA) has now approved use of a targeted therapy based solely on tumor molecular markers (pembrolizumab for tumors with deficient mismatch repair [MMR] and high microsatellite instability [MSI]) and approved another therapy based solely on a germline mutation as the predictive marker of benefit (olaparib for BRCA carriers with ovarian or breast cancer) [New Engl J Med 2017;377:1409-1412, N Engl J Med 2012;366:1382-1392, N Eng J Med 2017;377:523-533].Here, a patient is presented with a molecular diagnosis of Lynch syndrome and with breast cancer. Yet the breast cancer showed proficient expression of the same MMR gene found to be mutated in her germline testing. The case underscores the importance of tumor testing for MMR and MSI and of not assuming that the tumor is related to the Lynch syndrome rather than being sporadic. This is particularly true in patients with cancers (e.g., breast cancer) whose association with Lynch syndrome is not well established.The case presented also underscores the importance of considering next-generation sequencing of the tumor when the therapies approved are based on a germline mutation being the predictive marker. For example, the FDA-approved use of the PARP inhibitor olaparib is for ovarian or breast cancers in patients harboring a BRCA germline mutation [N Engl J Med 2012;366:1382-1392, N Eng J Med 2017;377:523-533]. Yet patients with tumors lacking BRCA loss of heterozygosity (LOH) or lacking other evidence of probable loss of normal BRCA gene product expression might be less likely to benefit from PARP inhibitor therapy, because the efficacy of PARP inhibitor therapy in patients with germline BRCA mutations would likely be predicated upon BRCA LOH in their tumors. KEY POINTS: Cancers in patients with germline mutations may be sporadic and unrelated to the germline mutation.Lynch syndrome is due to a germline mutated mismatch repair (MMR) gene. Cancers resulting from the germline MMR gene mutation as the predisposing event would be expected to be MMR deficient (dMMR) and microsatellite instability high (MSI-H). Sporadic cancers in patients with Lynch syndrome would be expected to be MMR proficient or microsatellite stable.Pembrolizumab is only approved for solid tumors demonstrating dMMR/MSI-H. Thus, whether the cancer tissue of origin is clearly associated with Lynch syndrome or not yet clearly established as a Lynch syndrome-related cancer (e.g., breast cancer), establishing the tumor to be dMMR/MSI-H is necessary to predict possible benefit and endorse the use of pembrolizumab.Ovarian cancers that develop in BRCA germline mutation carriers are so often related to the inherited mutated BRCA as the predisposing factor that testing the tumor for the footprint of BRCA-related ovarian cancer (BRCA loss of heterozygosity) is not necessary for use of the PARP inhibitor therapy olaparib. Future studies that include tumor evaluation for normal BRCA expression or surrogates of normal BRCA gene product expression might help determine which patients harboring a germline BRCA mutation are most likely to benefit from PARP inhibitor therapy.

Japanese Society for Cancer of the Colon and Rectum (JSCCR) Guidelines 2016 for the Clinical Practice of Hereditary Colorectal Cancer (Translated Version)

Hereditary colorectal cancer accounts for less than 5% of all colorectal cancer cases. Some of the unique characteristics that are commonly encountered in cases of hereditary colorectal cancer include early age at onset, synchronous/metachronous occurrence of the cancer, and association with multiple cancers in other organs, necessitating different management from sporadic colorectal cancer. While the diagnosis of familial adenomatous polyposis might be easy because usually 100 or more adenomas that develop in the colonic mucosa are in this condition, Lynch syndrome, which is the most commonly associated disease with hereditary colorectal cancer, is often missed in daily medical practice because of its relatively poorly defined clinical characteristics. In addition, the disease concept and diagnostic criteria for Lynch syndrome, which was once called hereditary non-polyposis colorectal cancer, have changed over time with continual research, thereby possibly creating confusion in clinical practice. Under these circumstances, the JSCCR Guideline Committee has developed the "JSCCR Guidelines 2016 for the Clinical Practice of Hereditary Colorectal Cancer (HCRC)," to allow delivery of appropriate medical care in daily practice to patients with familial adenomatous polyposis, Lynch syndrome, or other related diseases. The JSCCR Guidelines 2016 for HCRC were prepared by consensus reached among members of the JSCCR Guideline Committee, based on a careful review of the evidence retrieved from literature searches, and considering the medical health insurance system and actual clinical practice settings in Japan. Herein, we present the English version of the JSCCR Guidelines 2016 for HCRC.

Microsatellite Instability Occurs Rarely in Patients with Cholangiocarcinoma: A Retrospective Study from a German Tertiary Care Hospital

Immune-modulating therapy is a promising therapy for patients with cholangiocarcinoma (CCA). Microsatellite instability (MSI) might be a favorable predictor for treatment response, but comprehensive data on the prevalence of MSI in CCA are missing. The aim of the current study was to determine the prevalence of MSI in a German tertiary care hospital. Formalin-fixed paraffin-embedded tissue samples, obtained in the study period from 2007 to 2015 from patients with CCA undergoing surgical resection with curative intention at Johann Wolfgang Goethe University hospital, were examined. All samples were investigated immunohistochemically for the presence of MSI (expression of MLH1, PMS2, MSH2, and MSH6) as well as by pentaplex polymerase chain reaction for five quasimonomorphic mononucleotide repeats (BAT-25, BAT-26, NR-21, NR-22, and NR-24). In total, 102 patients were included, presenting intrahepatic (n = 35, 34.3%), perihilar (n = 42, 41.2%), and distal CCA (n = 25, 24.5%). In the immunohistochemical analysis, no loss of expression of DNA repair enzymes was observed. In the PCR-based analysis, one out of 102 patients was found to be MSI-high and one out of 102 was found to be MSI-low. Thus, MSI seems to appear rarely in CCA in Germany. This should be considered when planning immune-modulating therapy trials for patients with CCA.

A rapidly growing human papillomavirus-positive oral tongue squamous cell carcinoma in a 21-year old female: A case report

Oral tongue squamous cell carcinoma (OTSCC) has a median age at diagnosis of 62 years. The incidence of OTSCC in young adults has been increasing, and the reason is unclear. The present study describes a case, and molecular analysis, of OTSCC in a 21-year-old female. Clinical and pathological information were collected from medical records. Formalin-fixed paraffin-embedded biopsy tissue from the patient was reassessed using standard hematoxylin & eosin staining, and immunohistochemistry was used to assess the expression of cellular p16, MutL homolog (MLH)1, MLH2, MutS homolog 6 (MSH6) and PMS1 homolog 2 (PMS2). The human papilloma virus (HPV) genome was detected by PCR analysis of the extracted DNA. The young age of the patient with OTSCC was unusual. The original pathology report indicated koilocytotic atypia, a cellular abnormality associated with HPV. Although HPV-positive oral cancer tends to occur in 'younger' individuals, 21 years is unusual. The confirmation of biologically active HPV in the tumor was obtained via the observation of strong positive staining for cellular p16. The patient described a maternal family cluster of rare cancer types, thus the possibility that this rapidly growing cancer resulted from HPV infection combined with an underlying genetic mutation causing decreased DNA-mismatch repair was explored. However, MSH1, MSH2, MSH6 and PSM2, proteins that are associated with Lynch Syndrome, were expressed at normal levels. A rapidly growing OTSCC of a 21-year-old female was determined to be HPV-positive. The patient underwent combination chemotherapy and radiation and has experienced long-term survival without recurrence. The reason this tumor grew so quickly in such a young individual remains unknown. These types of cases warrant additional genomic and proteomic studies to improve understanding of this phenomenon.

A novel MLH1 intronic variant in a young Japanese patient with Lynch syndrome

Lynch syndrome, an autosomal dominantly inherited disease, is characterized by an increased risk of developing colorectal cancer. We found a novel germline variant of MLH1 (IVS6+2T>C) that caused Lynch syndrome in a young Japanese patient who had multiple colorectal cancers. Accurate diagnosis will be highly beneficial in clinical practice for surveillance and genetic counseling of patients and their relatives.

Microsatellite instability in prostate cancer by PCR or next-generation sequencing

BACKGROUND

Microsatellite instability (MSI) is now being used as a sole biomarker to guide immunotherapy treatment for men with advanced prostate cancer. Yet current molecular diagnostic tests for MSI have not been evaluated for use in prostate cancer.

METHODS

We evaluated two next-generation sequencing (NGS) MSI-detection methods, MSIplus (18 markers) and MSI by Large Panel NGS (> 60 markers), and compared the performance of each NGS method to the most widely used 5-marker MSI-PCR detection system. All methods were evaluated by comparison to targeted whole gene sequencing of DNA mismatch-repair genes, and immunohistochemistry for mismatch repair genes, where available.

RESULTS

In a set of 91 prostate tumors with known mismatch repair status (29-deficient and 62-intact mismatch-repair) MSIplus had a sensitivity of 96.6% (28/29) and a specificity of 100% (62/62), MSI by Large Panel NGS had a sensitivity of 93.1% (27/29) and a specificity of 98.4% (61/62), and MSI-PCR had a sensitivity of 72.4% (21/29) and a specificity of 100% (62/62).

CONCLUSIONS

We found that the widely used 5-marker MSI-PCR panel has inferior sensitivity when applied to prostate cancer and that NGS testing with an expanded panel of markers performs well. In addition, NGS methods offer advantages over MSI-PCR, including no requirement for matched non-tumor tissue and an automated analysis pipeline with quantitative interpretation of MSI-status.

Precise characterization of KRAS4b proteoforms in human colorectal cells and tumors reveals mutation/modification cross-talk

Mutations of the KRAS gene are found in human cancers with high frequency and result in the constitutive activation of its protein products. This leads to aberrant regulation of downstream pathways, promoting cell survival, proliferation, and tumorigenesis that drive cancer progression and negatively affect treatment outcomes. Here, we describe a workflow that can detect and quantify mutation-specific consequences of KRAS biochemistry, namely linked changes in posttranslational modifications (PTMs). We combined immunoaffinity enrichment with detection by top-down mass spectrometry to discover and quantify proteoforms with or without the Gly13Asp mutation (G13D) specifically in the KRAS4b isoform. The workflow was applied first to isogenic KRAS colorectal cancer (CRC) cell lines and then to patient CRC tumors with matching KRAS genotypes. In two cellular models, a direct link between the knockout of the mutant G13D allele and the complete nitrosylation of cysteine 118 of the remaining WT KRAS4b was observed. Analysis of tumor samples quantified the percentage of mutant KRAS4b actually present in cancer tissue and identified major differences in the levels of C-terminal carboxymethylation, a modification critical for membrane association. These data from CRC cells and human tumors suggest mechanisms of posttranslational regulation that are highly context-dependent and which lead to preferential production of specific KRAS4b proteoforms.

DNA mismatch repair in cancer

Microsatellite instability (MSI) refers to the hypermutator phenotype secondary to frequent polymorphism in short repetitive DNA sequences and single nucleotide substitution, as consequence of DNA mismatch repair (MMR) deficiency. MSI secondary to germline mutation in DNA MMR proteins is the molecular fingerprint of Lynch syndrome (LS), while epigenetic inactivation of these genes is more commonly found in sporadic MSI tumors. MSI occurs at different frequencies across malignancies, although original methods to assess MSI or MMR deficiency have been developed mostly in LS related cancers. Here we will discuss the current methods to detect MSI/MMR deficiency with a focus of new tools which are emerging as highly sensitive detector for MSI across multiple tumor types. Due to high frequencies of non-synonymous mutations, the presence of frameshift-mutated neoantigens, which can trigger a more robust and long-lasting immune response and strong TIL infiltration with tumor eradication, MSI has emerged as an important predictor of sensitivity for immunotherapy-based strategies, as showed by the recent FDA's first histology agnostic-accelerated approval to immune checkpoint inhibitors for refractory, adult and pediatric, MMR deficient (dMMR) or MSI high (MSI-H) tumors. Moreover, it is known that MSI status may predict cancer response/resistance to certain chemotherapies. Here we will describe the complex interplay between the genetic and clinical-pathological features of MSI/dMMR tumors and the cancer immunotherapy, with a focus on the predictive and prognostic role of MMR status for immune checkpoint inhibitors (ICIs) and providing some suggestions on how to conceive better predictive markers for immunotherapy in the next future.

Accurate Pan-Cancer Molecular Diagnosis of Microsatellite Instability by Single-Molecule Molecular Inversion Probe Capture and High-Throughput Sequencing

BACKGROUND

Microsatellite instability (MSI) is an emerging actionable phenotype in oncology that informs tumor response to immune checkpoint pathway immunotherapy. However, there remains a need for MSI diagnostics that are low cost, highly accurate, and generalizable across cancer types. We developed a method for targeted high-throughput sequencing of numerous microsatellite loci with pan-cancer informativity for MSI using single-molecule molecular inversion probes (smMIPs).

METHODS

We designed a smMIP panel targeting 111 loci highly informative for MSI across cancers. We developed an analytical framework taking advantage of smMIP-mediated error correction to specifically and sensitively detect instability events without the need for typing matched normal material.

RESULTS

Using synthetic DNA mixtures, smMIPs were sensitive to at least 1% MSI-positive cells and were highly consistent across replicates. The fraction of identified unstable microsatellites discriminated tumors exhibiting MSI from those lacking MSI with high accuracy across colorectal (100% diagnostic sensitivity and specificity), prostate (100% diagnostic sensitivity and specificity), and endometrial cancers (95.8% diagnostic sensitivity and 100% specificity). MSI-PCR, the current standard-of-care molecular diagnostic for MSI, proved equally robust for colorectal tumors but evidenced multiple false-negative results in prostate (81.8% diagnostic sensitivity and 100% specificity) and endometrial (75.0% diagnostic sensitivity and 100% specificity) tumors.

CONCLUSIONS

smMIP capture provides an accurate, diagnostically sensitive, and economical means to diagnose MSI across cancer types without reliance on patient-matched normal material. The assay is readily scalable to large numbers of clinical samples, enables automated and quantitative analysis of microsatellite instability, and is readily standardized across clinical laboratories.

Immunohistochemical null-phenotype for mismatch repair proteins in colonic carcinoma associated with concurrent MLH1 hypermethylation and MSH2 somatic mutations

Microsatellite instability, a well-established driver pathway in colorectal carcinogenesis, can develop in both sporadic and hereditary conditions via different molecular alterations in the DNA mismatch repair (MMR) genes. MMR protein immunohistochemistry (IHC) is currently widely used for the detection of MMR deficiency in solid tumors. The IHC test, however, can show varied staining patterns, posing challenges in the interpretation of the staining results in some cases. Here we report a case of an 80-year-old female with a colonic adenocarcinoma that exhibited an unusual "null" IHC staining pattern with complete loss of all four MMR proteins (MLH1, MSH2, MSH6, and PMS2). This led to subsequent MLH1 methylation testing and next generation sequencing which demonstrated that the loss of all MMR proteins was associated with concurrent promoter hypermethylation of MLH1 and double somatic truncating mutations in MSH2. These molecular findings, in conjunction with the patient's age being 80 years and the fact that the patient had no personal or family cancer history, indicated that the MMR deficiency was highly likely sporadic in nature. Thus, the stringent Lynch syndrome type surveillance programs were not recommended to the patient and her family members. This case illustrates a rare but important scenario where a null IHC phenotype signifies complex underlying molecular alternations that bear clinical management implications, highlighting the need for recognition and awareness of such unusual IHC staining patterns.

Precision medicine becomes reality-tumor type-agnostic therapy

Precision medicine just witnessed two breakthroughs in oncology in 2017. Pembrolizumab (Keytruda), Merck’s anti-programmed cell death-1 (PD-1) monoclonal antibody (mAb), received accelerated approval in May 2017 by the US Food and Drug Administration for the treatment of adult and pediatric patients with unresectable or metastatic solid tumors that have been identified as having microsatellite instability-high (MSI-H) or deficient DNA mismatch repair (dMMR). Shortly after, nivolumab (Opdivo), Bristol-Myers Squibb’s anti-PD-1 mAb, gained an accelerated approval in August 2017 for adult and pediatric patients with MSI-H or dMMR metastatic colorectal cancer that has progressed after standard chemotherapy. These regulatory approvals marked an important milestone that a cancer treatment may be approved based on a common biomarker rather than the anatomic location in the body where the tumor originated, and therefore established a precedent for tumor type-agnostic therapy. In the 2017 American Society for Clinical Oncology annual meeting, larotrectinib (LOXO-101), Loxooncology’s oral, potent, and selective inhibitor of tropomyosin receptor kinases (TRK), demonstrated unprecedented efficacy on unresectable or metastatic solid tumors with neurotrophic tropomyosin receptor kinase (NTRK)-fusion proteins in adult and pediatric patients. Both the anti-PD-1 mAbs and the TRK-targeting therapies share some basic features: (a) biomarker-based, well-defined rare patient population; (b) exceptionally high clinical efficacy, e.g., near 40% overall response rate (ORR) for pembrolizumab across 15 tumor types with MSI-H/dMMR and 75% ORR for larotrectinib across more than 12 tumor types with NTRK-fusion proteins; (c) durable responses lasting at least 6 months with complete responses observed; and (d) parallel development in adult and pediatric populations. With increasing accessibility to genetic analysis tools such as next-generation sequencing, tumor type-agnostic therapy has become a reality, both during clinical development and in clinical practice. Adjustments in our approaches to developing new anti-cancer drugs and to adopting these new cancer treatments in clinical practice need to occur in order to prepare ourselves for the new era of precision medicine.

Evaluating Mismatch Repair Deficiency in Pancreatic Adenocarcinoma: Challenges and Recommendations

Purpose: Immune checkpoint inhibition has been shown to generate profound and durable responses in mismatch repair deficient (MMR-D) solid tumors and has elicited interest in detection tools and strategies to guide therapeutic decision-making. Herein we address questions on the appropriate screening, detection methods, patient selection, and initiation of therapy for MMR-D pancreatic ductal adenocarcinoma (PDAC) and assess the utility of next-generation sequencing (NGS) in providing additional prognostic and predictive information for MMR-D PDAC.Experimental Design: Archival and prospectively acquired samples and matched normal DNA from N = 833 PDAC cases were analyzed using a hybridization capture-based, NGS assay designed to perform targeted deep sequencing of all exons and selected introns of 341 to 468 cancer-associated genes. A computational program using NGS data derived the MSI status from the tumor-normal paired genome sequencing data. Available germline testing, IHC, and microsatellite instability (MSI) PCR results were reviewed to assess and confirm MMR-D and MSI status.Results: MMR-D in PDAC is a rare event among PDAC patients (7/833), occurring at a frequency of 0.8%. Loss of MMR protein expression by IHC, high mutational load, and elevated MSIsensor scores were correlated with MMR-D PDAC. All 7 MMR-D PDAC patients in the study were found to have Lynch syndrome. Four (57%) of the MMR-D patients treated with immune checkpoint blockade had treatment benefit (1 complete response, 2 partial responses, 1 stable disease).Conclusions: An integrated approach of germline testing and somatic analyses of tumor tissues in advanced PDAC using NGS may help guide future development of immune and molecularly directed therapies in PDAC patients. Clin Cancer Res; 24(6); 1326-36. ©2018 AACR.

Biomarkers in Urachal Cancer and Adenocarcinomas in the Bladder: A Comprehensive Review Supplemented by Own Data

Urachal cancer (UrC) is a rare but aggressive cancer. Due to overlapping histomorphology, discrimination of urachal from primary bladder adenocarcinomas (PBAC) and adenocarcinomas secondarily involving the bladder (particularly colorectal adenocarcinomas, CRC) can be challenging. Therefore, we aimed to give an overview of helpful (immunohistochemical) biomarkers and clinicopathological factors in addition to survival analyses and included institutional data from 12 urachal adenocarcinomas. A PubMed search yielded 319 suitable studies since 1930 in the English literature with 1984 cases of UrC including 1834 adenocarcinomas (92%) and 150 nonadenocarcinomas (8%). UrC was more common in men (63%), showed a median age at diagnosis of 50.8 years and a median tumor size of 6.0 cm. No associations were noted for overall survival and progression-free survival (PFS) and clinicopathological factors beside a favorable PFS in male patients (p = 0.047). The immunohistochemical markers found to be potentially helpful in the differential diagnostic situation are AMACR and CK34βE12 (UrC versus CRC and PBAC), CK7, β-Catenin and CD15 (UrC and PBAC versus CRC), and CEA and GATA3 (UrC and CRC versus PBAC). Serum markers like CEA, CA19-9 and CA125 might additionally be useful in the follow-up and monitoring of UrC.

Epithelial splicing regulatory protein 1 and 2 paralogues correlate with splice signatures and favorable outcome in human colorectal cancer

ESRPs are master splice regulators implicated in alternative mRNA splicing programs important for epithelial-mesenchymal transition (EMT) and tumor progression. ESRP1 was identified in some tumors as good or worse predictor of outcome, but in colorectal cancer (CRC) the prognostic value of ESRPs and relation with mesenchymal splice variants is not clear. Here, we studied 68 CRC cases, compared tissue expression of ESRPs with clinical data and with EMT gene splice patterns of conditional CRC cells with deficient ESRP1 expression.Around 72% of patients showed global decreased transcript expression of both ESRPs in tumor as compared to matched non-neoplastic colorectal epithelium. Reduction of ESRP1 in tumor cells was evaluated by immunohistochemistry, associated with microsatellite stability and switch to mesenchymal splice signatures of FGFRs, CD44, ENAH and CTNND1(p120-catenin). Expression of ESRPs was significantly associated with favorable overall survival (log-rank test, P=0.0186 and 0.0408), better than prognostic stratification by tumor staging; and for ESRP1 confirmed with second TCGA cohort (log-rank test, P=0.0435). Prognostic value is independent of the pathological stage and microsatellite instability (ESRP1: HR=0.36, 95%CI 0.15-0.91, P=0.032; ESRP2: HR=0.23, 95%CI 0.08-0.65, P=0.006).Our study supports the role of ESRP1 as tumor suppressor and strongly suggests that ESRPs are candidate markers for early detection, diagnosis, and prognosis of CRC.

Microsatellite instability and protein expression of MLH1 and MSH2 genes in young Mexican patients less than 50 years of age diagnosed with colorectal cancer

Diagnosis of colorectal cancer in patients under 45 years old should alert us to possible hereditary forms of this neoplasia. Most cases of hereditary colorectal cancer correspond to Lynch syndrome which is caused by mutations in DNA mismatch repair genes, particularly MLH1 and MSH2. The dysfunction is associated with microsatellite instability which occurs in 95% cases of this syndrome and in 15% of sporadic colorectal cancer. In sporadic colon tumors, downregulation of MLH1 is observed in cases with the BRAF V600E variant, which induces hypermetylation of the MLH1 promoter. Mutation screening for hereditary cancer has impacted the diagnosis, genetic counseling, and early tumor detection in families affected by hereditary colorectal cancer syndromes but mutation screening technologies are seldom available in public health care centers in developing countries. This study aimed to describe immunohistochemistry and microsatellite instability abnormalities in tumor samples archived in a public hospital in Mexico. Paraffin-embedded samples of patients with colorectal cancer, diagnosed at under 50 years old, were studied to analyze correlations among clinical variables, MLH1 and MSH2 protein expression (immunohistochemistry), microsatellite instability (fluorescent PCR-based assay), and BRAF V600E variant (real time PCR). Forty-seven tumor specimens from patients with TNM stage II and above were analyzed. Tumors were mainly located in the proximal colon segment and displayed histologic intestinal variety and infiltration to serosa. Twenty samples showed decreased expression of mismatch repair proteins and 10 of these presented microsatellite instability (7 high and 3 low instability patterns, respectively). There were no instances of BRAF V600E mutation found. Altered MLH1 or MSH2 expression was found in 42.5% of the samples and microsatellite instability was observed in 21.3% of the tumors. These results suggested that about a fifth of the patients were candidates for family assessment and genetic counseling.

Comparison of microsatellite status detection methods in colorectal carcinoma

There are two commonly accepted methods for detecting microsatellite status. One is to detect amplified microsatellite loci by polymerase chain reaction (PCR) and the other is to detect mismatch repair gene (MMR) protein expression by immunohistochemistry (IHC). PCR detection is considered to be accurate in clinical operations while IHC is widely used due to ease of operation and lesser expense. In order to compare IHC with PCR in detecting microsatellite status in colorectal carcinoma, a total of 569 samples of colorectal carcinoma resection were collected in the Department of Pathology, Nanjing Drum Tower Hospital, between June 2014 and June 2017. In all samples, IHC and PCR was used to detect microsatellite status and the consistency of results between the two methods was compared. We found that 48 cases of microsatellite instability (MSI) were detected by PCR including 37 cases of microsatellite instability high (MSI-H), 11 cases of microsatellite instability low (MSI-L), and 521 cases of MSS. MSI accounted for 8.44% of all cases and MSI-H accounted for 6.50%. IHC results of the 569 patients showed that 69 cases were deficient mismatch repair (dMMR) and 500 cases were proficient mismatch repair (pMMR). dMMR accounted for 12.13% of all cases. Loss expression of PMS2 protein was the most common while MSH6 was rare. The coincidence rate of the two methods for detecting microsatellite states was 91.92%. IHC and the PCR method had high consistency in microsatellite status. Compared with PCR, the IHC method is more economical and more convenient for clinical operations. When the 4 repair proteins were without deficiency detected by IHC, it could be diagnosed as MSS/MSI-L and further PCR was not necessary. When any repair protein was found to be deficient, PCR detection was needed to determine whether MSI existed. Our conclusion will save a lot of time and costs in clinical work.

Microsatellite instability in stage II colorectal cancer: An Indian perspective

INTRODUCTION

Around 80% of colorectal carcinoma are associated with chromosomal instability (CIN) while rest of 20 % are euploid, possessing defect in mis match repair system (MMR) quintessential for surveillance and correction of errors in introduced into microsatellites.

MATERIALS AND METHODS

We analyse all stage II CRC for MSI who presented at MDTC at Army hospital (research and refrral) new delhi during last 2 years (Jan 14 to Dec 2015).

RESULTS

We found that 22.2% patients out of 45 patients with stageII CRC being MSI-. high. We also noticed all suchcases were associated with loss of expression of PMS2 & MLH1, that was in contrast other studies where loss of MLH1 and MSH@, MSH6 were seen more commonly.

CONCLUSION

MSI occurs in a significant proportion of colorectal cancers in young (<50 years old) patients. Young age at colorectal cancer diagnosis, proximal tumor location, family history of colorectal cancer were independent predictors of MSI status in our patients. In a proportion of these young patients with MSI tumors, loss of expression of proteins by 2 MMR genes PMS2 and hMLH1 has been identified.

Nivolumab in the treatment of microsatellite instability high metastatic colorectal cancer

Nivolumab is a PD-1 inhibitor approved for the use in treatment of multiple tumor types (such as melanoma, non-small-cell lung cancer, renal cell carcinoma, urothelial cancer and Hodgkin's lymphoma). In July 2017, the US FDA granted accelerated approval of this agent for the treatment of metastatic colorectal cancer patients whose tumor harbors deficient mismatch repair, or microsatellite-instability high and have progressed on conventional chemotherapy. In this review, we will discuss the use, efficacy, and safety of this agent in microsatellite-instability high metastatic colorectal cancer.

Clinical Aspects of Microsatellite Instability Testing in Colorectal Cancer

Microsatellite instability (MSI) is a molecular hallmark for some colorectal cancers (CRCs) in which short tandem repeats are prone to mutations along with DNA sequences. It is due to DNA-mismatch-repair system deficiency because of a germline/somatic mutation in mismatch-repair (MMR) genes. The germline mutations lead to Lynch syndrome (LS) while epigenetic gene silencing results in sporadic CRC tumors. We discuss in our paper the most important clinical aspects of MSI testing in CRCs. We reviewed the most reliable relevant studies and clinical trials according to their high-quality methods, particularly within two recent decades. MSI testing is used to classify CRC tumors as MSI-high (MSI-H), MSI-low, and microsatellite stable tumors. MSI-H or MMR deficient tumors have shown the best prognosis among all CRCs, so MSI testing is considered as a good prognostic marker. Moreover, it is used to identify LS among familial CRC patients. There is a diagnostic mutation in BRAF gene (V600E) by which sporadic CRCs could be distinguished from LS associated CRCs, due to its concordance with sporadic CRCs not LS. Although, some previous studies had demonstrated a predictive role for MSI testing in chemotherapy process, emerging some controversial findings in recent studies has not convinced many authors to recommend it as a routine examination to evaluate therapeutic response. Though emerging new molecular findings have opened novel windows to develop clinical management of CRC, MSI testing has remained as an excellent prognostic and diagnostic tool for CRC tumors.

Deficient mismatch repair and RAS mutation in colorectal carcinoma patients: a retrospective study in Eastern China

Objectives

To investigate the frequency and prognostic role of deficient mismatch repair (dMMR) and RAS mutation in Chinese patients with colorectal carcinoma.

Methods

Clinical and pathological information from 813 patients were reviewed and recorded. Expression of mismatch repair proteins was tested by immunohistochemistry. Mutation analyses for RAS gene were performed by real-time polymerase chain reaction. Correlations of mismatch repair status and RAS mutation status with clinicopathological characteristics and disease survival were determined.

Results

The overall percentage of dMMR was 15.18% (121/797). The proportion of dMMR was higher in patients <50 years old (p < 0.001) and in the right side of the colon (p < 0.001). Deficient mismatch repair was also associated with mucinous production (p < 0.001), poor differentiation (p < 0.001), early tumor stage (p < 0.05) and bowel wall invasion (p < 0.05). The overall RAS mutation rate was 45.88%, including 42.56% (346/813) KRAS mutation and 3.69% (30/813) NRAS mutation (including three patients with mutations in both). KRAS mutation was significantly associated with mucinous production (p < 0.05), tumor stage (p < 0.05) and was higher in non-smokers (p < 0.05) and patients with a family history of colorectal carcinoma (p < 0.05). Overall, 44.63% (54/121) dMMR tumors harbored KRAS mutation, however, dMMR tumors were less likely to have NRAS mutation. Moreover, dMMR, KRAS and NRAS mutation were not prognostic factors for stage I–III colorectal carcinoma.

Conclusions

This study confirms that the status of molecular markers involving mismatch repair status and RAS mutation reflects the specific clinicopathological characteristics of colorectal carcinoma.

Correlation of immunohistochemical mismatch repair protein status between colorectal carcinoma endoscopic biopsy and resection specimens

Background

Microsatellite instability is reflective of a deficient mismatch repair system (dMMR), which may be due to either sporadic or germline mutations in the relevant mismatch repair (MMR) gene. MMR status is frequently determined by immunohistochemistry (IHC) for mismatch repair proteins (MMRPs) on colorectal cancer (CRC) resection specimens. However, IHC testing performed on endoscopic biopsy may be as reliable as that performed on surgical resections.

Aim

We aimed to evaluate the reliability of MMR IHC staining on preoperative CRC endoscopic biopsies compared with matched-surgical resection specimens.

Methods

A retrospective search of our institution’s histopathology electronic database was performed. Patients with CRC who had MMR IHC performed on both their preoperative endoscopic biopsy and subsequent resection from January 2010 to January 2016 were included. Concordance of MMR staining between biopsy and resection specimens was assessed.

Results

From 2000 to 2016, 53 patients had MMR IHC performed on both their preoperative colorectal endoscopic biopsy and resection specimens; 10 patients (18.87%) demonstrated loss of ≥1 MMRP on their initial endoscopic tumour biopsy. The remainder (81.13%) showed preservation of staining for all MMRPs. There was complete agreement in MMR IHC status between the preoperative endoscopic biopsies and corresponding resection specimens in all cases (κ=1.000, P<0.000) with a sensitivity of 100% (95% CI 69.15 to 100) and specificity of 100% (95% CI 91.78 to 100) for detection of dMMR.

Conclusion

Endoscopic biopsies are a suitable source of tissue for MMR IHC analysis. This may provide a number of advantages to both patients and clinicians in the management of CRC.

Microsatellite instability in colorectal cancer

Colorectal cancer (CRC) is a heterogeneous disease that is caused by the interaction of genetic and environmental factors. Although it is one of the most common cancers worldwide, CRC would be one of the most curable cancers if it is detected in the early stages. Molecular changes that occur in colorectal cancer may be categorized into three main groups: 1) Chromosomal Instability (CIN), 2) Microsatellite Instability (MSI), and 3) CpG Island Methylator phenotype (CIMP). Microsatellites, also known as Short Tandem Repeats (STRs) are small (1-6 base pairs) repeating stretches of DNA scattered throughout the entire genome and account for approximately 3 % of the human genome. Due to their repeated structure, microsatellites are prone to high mutation rate. Microsatellite instability (MSI) is a unique molecular alteration and hyper-mutable phenotype, which is the result of a defective DNA mismatch repair (MMR) system, and can be defined as the presence of alternate sized repetitive DNA sequences which are not present in the corresponding germ line DNA. The presence of MSI is found in sporadic colon, gastric, sporadic endometrial and the majority of other cancers. Approximately, 15-20 % of colorectal cancers display MSI. Determination of MSI status in CRC has prognostic and therapeutic implications. As well, detecting MSI is used diagnostically for tumor detection and classification. For these reasons, microsatellite instability analysis is becoming more and more important in colorectal cancer patients. The objective of this review is to provide the comprehensive summary of the update knowledge of colorectal cancer classification and diagnostic features of microsatellite instability.

Topographic, histological and molecular study of aberrant crypt foci identified in human colon in different clinical groups

Background/Aims

Aberrant crypt foci (ACF) are early microscopic lesions of the colonic mucosa, which can be detected by magnified chromoendoscopy. Herein, we have investigated whether ACF identified in different clinical groups can be differentiated based on their characteristics.

Methods

Macroscopically unremarkable mucosal flaps were collected from 270 fresh colectomies and divided into 3 clinical groups: colorectal carcinoma (group A), disease controls having known pre-neoplastic potential (group Bc), and disease controls without risk of carcinoma development (group Bn). Topographic and histologic analysis, immunohistochemistry, and molecular studies (high-resolution melt curve analysis, real-time polymerase chain reaction, and Sanger sequencing) were conducted for certain neoplasia-associated markers.

Results

ACF were seen in 107 cases, out of which 72 were left colonic ACF and 35 right colonic ACF (67.2% vs. 32.7%, P=0.02). The overall density of left colonic ACF was 0.97/cm, which was greater than the right colonic ACF density of 0.81/cm. Hypercrinia was present in 41 out of 72 left colonic ACF and in 14 out of 35 right colonic ACF (P=0.01). Immunohistochemical expression of p53 was also greater in left colonic ACF than in right colonic ACF (60.5% vs. 38.2%, P=0.03). However, ACF identified among the 3 clinical groups did not show any distinguishing topographic, histological, or genetic changes.

Conclusions

Left colonic ACF appear to be high-risk based on their morphological and prototypic tumor marker signature. ACF identified in different clinical groups do not show significant genotypic or topographic differences. Further detailed genetic studies are required to elucidate them further.

Microsatellite Instability in Stage II and III Colorectal Cancer: Patterns and Profile

Introduction: Around 80% of colorectal carcinoma are associated with chromosomal instability while rest of 20% are euploid, possessing defect in mismatch repair system (MMR) quintessential for surveillance and correction of errors introduced into microsatellites. The microsatellite instability (MSI) phenotype has three major clinical applications: prognosis of colorectal cancer (CRC), prediction of response to 5 fluorouracil, and irinotecan, and genetic assessment of Lynch syndrome. Materials and Methods: We analyzed all Stage II and Stage III colorectal cancer (CRC) for MSI, who presented at Army Hospital, Research and Referral, New Delhi, from January 2014 to December 2016. Although patients of Stage II CRC were taken throughout the study period, Stage III CRC was included in last 1½ years to compare the prevalence of MSI in these two subsets of patients. Results: 26.2% of Stage II and 11.3% of Stage III patients were found to be MSI-high (MSI-H) (P = 0.04). Nineteen (86%) of 22 MSI-H patients were below 30 years of age (P = 0.01). Of 22 MSI-H patients, 18 had right-sided tumors (P = 0.03) and only three patients had rectal tumors. Most common pattern of MSI-H tumors was loss of expression of MLH1 and PMS2, seen in 15 of 16 (88%) of Stage II and three of 6 (50%) of Stage III CRC (P = 0.04). Conclusion: We conclude higher prevalence of MSI-H tumors in Stage II, as compared to Stage III CRC, which was demonstrated slightly higher in our study compared to published literature. MSI-H tumors tend to occur with high frequency in younger population, with right-sided colonic tumors, histopathology characterized by mucinous subtype with high prevalence of tumor infiltrating lymphocytes. Loss of expression of two MMR proteins, namely, PMS2 and MLH1 has been identified in most of MSI-H patients of our study, of which 86% were <30 years of age. This is in contrast to observation in previous studies where loss of PMS2 and MLH1 proteins was observed in older (>70 years) patients with MSI-H tumors, and in younger patients, MSI-H status was associated with loss of MLH1, MSH2, and MSH6.

Gynaecological neoplasms in common familial syndromes (Lynch and HBOC)

Recognising hereditary predisposition in a cancer patient has implications both for the patient and the patient's kindred. For the latter, cascade germline testing can reassure those not-at-risk family members while carriers can be enrolled in cancer screening and prevention programs that are medically effective and economically sustainable for health care systems. Furthermore, in many of these syndromes, ramifications of molecular phenotypes are increasing, and it is now emerging that, in addition, they convey prognostic and predictive information. Although cancer predisposition syndromes are rare, these molecular phenotypes also occur as somatic events in sporadic cancer settings. The information obtained from these molecular phenotypes, regardless of germline or somatic origin, is being incorporated into clinical management in view of their manifold significance. Thus, increasingly, bespoke management of cancer patients involves testing for both germline and somatic mutations in tumours. Lynch syndrome and BRCA-1 and BRCA-2-associated hereditary breast and ovarian cancer are hereditary cancer syndromes frequently involving the gynaecological tract but tumours associated with similar molecular alterations may also occur sporadically. Thus, the molecular phenotype of mismatch repair deficiency, microsatellite instability or hypermutator phenotype may be attributable to germline or somatic events. Similarly, homologous recombination deficiency or 'BRCAness' in ovarian cancers may be syndromic or sporadic. While hereditary syndromes are well recognised, the prognostic and predictive implications of these molecular phenotypes have only recently been elucidated and these aspects will finally ensure that molecular screening may become standard of care. Thus, nowadays pathologists are asked to designate the molecular phenotype of these cancers and then determine whether it is due to hereditary or sporadic causes.