Recent discoveries in the molecular genetics of Lynch syndrome

Oncology Informatics for Lynch Syndrome Research and Care: A Literature Review

PURPOSE

This study aims to review and evaluate available informatics platforms for research and management purposes of Lynch syndrome (LS) to identify gaps and needs for future development.

METHODS

LS informatics tools were identified through literature search in four publication databases (1 and Scopus). First, the LS and functional elements of every informatics tools for LS were introduced. Then, current existing LS informatics tools were reviewed and explained.

RESULTS

A detailed review of implemented studies shows that many types of informatics platforms are available for LS management (ie, prediction model, clinical decision support system, database website, and other tools for research and management purposes of LS). Moreover, several dimensions of existing LS informatics tools were discussed and features and positive findings were reported.

CONCLUSION

Reviewing the literature reveals that several LS informatics tools were focused on gene-specific estimate, cancer risk prediction, identifying/screening patients, supporting personalized care of individuals with LS, and storing mismatch repair mutations information. Nevertheless, these platforms do not fully cover the care and research purposes. For instance, future developments of LS tools require more attention to dynamic knowledgebase, extra-colonic lynch–related cancers on the basis of precision medicine, variants of unknown significance, and support from diagnosis to surveillance for patient follow-up. Insights and recommendations provided in this study could help researchers and developers to meet the existing challenges in future developments.

Lynch Syndrome: Its Impact on Urothelial Carcinoma

Lynch syndrome, known as hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomal-dominant familial cancer syndrome with an increased risk for urothelial cancer (UC). Mismatch repair (MMR) deficiency, due to pathogenic variants in MLH1, MSH2, MSH6, and PMS2, and microsatellite instability, are known for development of Lynch syndrome (LS) associated carcinogenesis. UC is the third most common cancer type in LS-associated tumors. The diversity of germline variants in the affected MMR genes and their following subsequent function loss might be responsible for the variation in cancer risk, suggesting an increased risk of developing UC in MSH2 mutation carriers. In this review, we will focus on LS-associated UC of the upper urinary tract (UUT) and bladder, their germline profiles, and outcomes compared to sporadic UC, the impact of genetic testing, as well as urological follow-up strategies in LS. In addition, we present a case of metastatic LS-associated UC of the UUT and bladder, achieving complete response during checkpoint inhibition since more than 2 years.

Colorectal carcinoma with double somatic mismatch repair gene inactivation: clinical and pathological characteristics and response to immune checkpoint blockade

Double somatic mismatch-repair-gene mutation/alteration is a recently recognized molecular mechanism that underlies microsatellite instability-high in some colorectal carcinomas. It remains to be determined whether and how microsatellite instability-high tumors with this molecular defect differ from their counterparts caused by other mechanisms, specifically, Lynch syndrome-associated and MLH1-promoter hypermethylated. In this study, we evaluated the clinical and pathological characteristics of a series of 15 double somatic mutation/alteration-associated microsatellite instability-high colorectal carcinomas identified from our genetics service and 68 such cases reported in the literature. We observed that these cases presented at an age similar to MLH1-promoter hypermethylated (n = 20) and microsatellite-stable (n = 39) cases but older than Lynch syndrome-associated cases (n = 20, p < 0.05). While these tumors simulated other microsatellite instability-high tumors in their prevalent right-sided location, they appeared to differ in TNM stages at presentation (73% stage III/IV versus 25% stage III/IV in other microsatellite instability-high tumors, p = 0.04). Histologically, 40% of them had a dominant solid growth pattern. Inter-tumoral heterogeneity was a striking feature, spanning the spectrum from medullary type (with a tumor-infiltrating-lymphocyte/high-power-field count as high as 59) to conventional-type with only few tumor-infiltrating-lymphocytes (1/high-power-filed). As a group, these tumors seemed less likely to show robustly high lymphocytic infiltration than other microsatellite instability-high tumors (only 20% had ≥10 tumor-infiltrating-lymphocytes/high-power-filed, whereas this rate in Lynch syndrome-associated and MLH1-promoter hypermethylated tumors was 60% and 75%, respectively). Three double somatic mutation/alteration-associated tumors were treated with a PD1/PD-L1 checkpoint inhibitor. While all three had an elevated tumor-mutation-burden (>47 mut/megabase), only one had tumor-infiltrating-lymphocytes >10/high-power-field, yet all three exhibited measurable response. In summary, microsatellite instability-high colorectal carcinomas caused by double somatic mismatch-repair-gene mutation/alteration may have varied clinical and pathological characteristics, and some may have relatively low tumor-infiltrating-lymphocytes; response to immune checkpoint inhibitors can be achieved in this group even when the lymphocytic infiltration is not abundant.

Phenotypic and genotypic heterogeneity of Lynch syndrome: a complex diagnostic challenge

Lynch syndrome is the hereditary disorder that most frequently predisposes to colorectal cancer as well as predisposing to a number of extracolonic cancers, most prominently endometrial cancer. It is caused by germline mutations in the mismatch repair genes. Both its phenotype and genotype show marked heterogeneity. This review gives a historical overview of the syndrome, its heterogeneity, its genomic landscape, and its implications for complex diagnosis, genetic counseling and putative implications for immunotherapy.

A potpourri of pathogenetic pathways in endometrial carcinoma with a focus on Lynch Syndrome

Endometrial carcinoma is the most frequently occurring female genital tract malignancy in developed nations, with a rising annual incidence. Endometrioid endometrial carcinoma (EEC), the most common histological variant, differs in morphologic and molecular characteristics from serous carcinomas but morphological distinction of high-grade EECs from serous carcinomas may prove difficult. Thus, molecular categorization of tumors may allow for better tumor classification with greater insight into the underlying biology of endometrial carcinomas with new therapeutic options. Microsatellite instability (MSI) is a commonly occurring molecular aberration in EECs and has been identified in most Lynch Syndrome (LS) associated tumors. This tumor syndrome predisposes afflicted individuals to a myriad of tumors including endometrial carcinoma. Herein, the molecular signature of endometrial tumors as well as LS, and its clinical manifestations are reviewed. Understanding of the pathogenetic pathways allows for greater comprehension of occurrences at a molecular level which are then appreciated at a cellular and tissue level, by the histopathologist. The molecular classification of endometrial tumors allows for further targeted therapeutic options for affected patients. Screening tests for patients with suspected LS enables surveillance of other tumors in the affected patient and her family with the potential to decrease morbidity and mortality. It is envisioned that this overview will allow for enhanced comprehension of genetic pathways by practicing pathologists, oncologists, gynecologists and other members of the multidisciplinary team, all of whom are involved in the management of the patient with an endometrial malignancy.

Genetics, diagnosis and treatment of Lynch syndrome: Old lessons and current challenges

Lynch syndrome (LS) is an autosomal dominant genetic disorder associated with germline mutations in DNA mismatch repair (MMR) genes. The carriers of pathogenic mutations in these genes have an increased risk of developing a colorectal cancer and/or LS-associated cancer. The LS-associated cancer types include carcinomas of the endometrium, small intestine, stomach, pancreas and biliary tract, ovary, brain, upper urinary tract and skin. The criteria for the clinical diagnosis of LS and the procedures of the genetic testing for identification of pathogenetic mutations carriers in MMR genes have long been known. A crucial point in the mutation detection analysis is the correct definition of the pathogenecity associated with MMR genetic variants, especially in order to include the mutation carriers in the endoscopy surveillance programs more suited to them. Therefore, this may help to improve the LS-associated cancer prevention programs. In the present review, we also report the recent discoveries in molecular genetics of LS, such as the new roles of MMR protein and immune response of MMR repair deficiency in colorectal cancer. Finally, we discuss the main therapeutic approaches, including immunotherapy, which represent a valid alternative to traditional therapeutic methods and extend the life expectancy of patients that have already developed LS-associated colorectal cancer.

No Difference in Colorectal Cancer Incidence or Stage at Detection by Colonoscopy Among 3 Countries With Different Lynch Syndrome Surveillance Policies

BACKGROUND & AIMS

Patients with Lynch syndrome are at high risk for developing colorectal cancer (CRC). Regular colonoscopic surveillance is recommended, but there is no international consensus on the appropriate interval. We investigated whether shorter intervals are associated with lower CRC incidence and detection at earlier stages by comparing the surveillance policies in Germany, which evaluates patients by colonoscopy annually, in the Netherlands (patients evaluated at 1-2-year intervals), and Finland (patients evaluated at 2-3-year intervals).

METHODS

We collected data from 16,327 colonoscopic examinations (conducted from 1984 through 2015) of 2747 patients with Lynch syndrome (pathogenic variants in the MLH1, MSH2, or MSH6 genes) from the German HNPCC Consortium, the Dutch Lynch Syndrome Registry, and the Finnish Lynch Syndrome Registry. Our analysis included 23,309 person-years of cumulative observation time. Time from the index colonoscopy to incident CRC or adenoma was analyzed using the Kaplan-Meier method; groups were compared using the log-rank test. We performed multivariable Cox regression analyses to identify factors associated with CRC risk (diagnosis of CRC before the index colonoscopy, sex, mutation, age, and presence of adenoma at the index colonoscopy).

RESULTS

The 10-year cumulative CRC incidence ranged from 4.1% to 18.4% in patients with low- and high-risk profiles, respectively, and varied with age, sex, mutation, and prior detection of CRC or adenoma. Observed colonoscopy intervals were largely in accordance with the country-specific recommendations. We found no significant differences in cumulative CRC incidence or CRC stage at detection among countries. There was no significant association between CRC stage and time since last colonoscopy.

CONCLUSIONS

We did not find a significant reduction in CRC incidence or stage of detection in Germany (annual colonoscopic surveillance) than in countries with longer surveillance intervals (the Netherlands, with 1-2-year intervals, and Finland, with 2-3-year intervals). Overall, we did not find a significant association of the interval with CRC risk, although age, sex, mutation, and prior neoplasia were used to individually modify colonoscopy intervals. Studies are needed to develop and validate risk-adapted surveillance strategies and to identify patients who benefit from shorter surveillance intervals.

Molecular subtype classification of urothelial carcinoma in Lynch syndrome

Lynch syndrome confers an increased risk for urothelial carcinoma (UC). Molecular subtypes may be relevant to prognosis and therapeutic possibilities, but have to date not been defined in Lynch syndrome‐associated urothelial cancer. We aimed to provide a molecular description of Lynch syndrome‐associated UC. Thus, Lynch syndrome‐associated UCs of the upper urinary tract and the urinary bladder were identified in the Danish hereditary nonpolyposis colorectal cancer (HNPCC) register and were transcriptionally and immunohistochemically profiled and further related to data from 307 sporadic urothelial carcinomas. Whole‐genome mRNA expression profiles of 41 tumors and immunohistochemical stainings against FGFR3, KRT5, CCNB1, RB1, and CDKN2A (p16) of 37 tumors from patients with Lynch syndrome were generated. Pathological data, microsatellite instability, anatomic location, and overall survival data were analyzed and compared with sporadic bladder cancer. The 41 Lynch syndrome‐associated UC developed at a mean age of 61 years with 59% women. mRNA expression profiling and immunostaining classified the majority of the Lynch syndrome‐associated UC as urothelial‐like tumors with only 20% being genomically unstable, basal/SCC‐like, or other subtypes. The subtypes were associated with stage, grade, and microsatellite instability. Comparison to larger datasets revealed that Lynch syndrome‐associated UC shares molecular similarities with sporadic UC. In conclusion, transcriptomic and immunohistochemical profiling identifies a predominance of the urothelial‐like molecular subtype in Lynch syndrome and reveals that the molecular subtypes of sporadic bladder cancer are relevant also within this hereditary, mismatch‐repair defective subset.

Metachronous colorectal cancer risk in Lynch syndrome patients-should the endoscopic surveillance be more intensive?

PURPOSE

Regular follow-up for patients with Lynch syndrome (LS) is vital due to the increased risk of colorectal (50-80%), endometrial (40-60%), and other cancers. However, there is an ongoing debate concerning the best interval between colonoscopies. Currently, no specific endoscopic follow-up has been decided for LS patients who already have an index colorectal cancer (CRC). The aim of this study was to evaluate the risk of metachronous cancers (MC) after primary CRC in a LS population and to determinate if endoscopic surveillance should be more intensive.

METHODS

A prospective cohort of patients with a confirmed diagnosis of hereditary CRC since 2009 was included. Patients with LS and a primary CRC were the cohort of choice.

RESULTS

One hundred twenty-one patients were included with a median age of 44 years(16-70). At least one MC occurred in 39 patients (32.2%), with a median interval of 67 months (6-300) from index cancer. Fifteen (38.5%) developed two or more MCs during follow-up, with a median number of two (2-6) tumors occurring. Metachronous CRC were diagnosed after a median interval of 24 (6-57) months since last colonoscopy and were more commonly seen in MSH2 mutation carriers (58 vs. 35%, p = 0.001). After a median follow-up of 52.9 (3-72) months, no cancer-related deaths were recorded.

CONCLUSION

Patients with LS have an increased risk of MC, especially CRCs. With a median time period of 24 months between colonoscopy and metachronous CRC, the interval between surveillance colonoscopies following primary CRC should not exceed 18 months, especially in patients with MSH2 mutation.

Successful immune checkpoint blockade in a patient with advanced stage microsatellite-unstable biliary tract cancer

Cancers acquire multiple somatic mutations that can lead to the generation of immunogenic mutation-induced neoantigens. These neoantigens can be recognized by the host's immune system. However, continuous stimulation of immune cells against tumor antigens can lead to immune cell exhaustion, which allows uncontrolled outgrowth of tumor cells. Recently, immune checkpoint inhibitors have emerged as a novel approach to overcome immune cell exhaustion and reactivate antitumor immune responses. In particular, antibodies blocking the exhaustion-mediating programmed death receptor (PD-1)/programmed death receptor ligand (PD-L1) pathway have shown clinical efficacy. The effects were particularly pronounced in tumors with DNA mismatch repair (MMR) deficiency and a high mutational load, which typically occur in the colon and endometrium. Here, we report on a 24-yr-old woman diagnosed with extrahepatic cholangiocarcinoma who showed strong and durable response to the immune checkpoint inhibitor pembrolizumab, although treatment was initiated at an advanced stage of disease. The patient's tumor displayed DNA MMR deficiency and microsatellite instability (MSI) but lacked other features commonly discussed as predictors of response toward checkpoint blockade, such as PD-L1 expression or dense infiltration with cytotoxic T cells. Notably, high levels of HLA class I and II antigen expression were detected in the tumor, suggesting a potential causal relation between functionality of the tumor's antigen presentation machinery and the success of immune checkpoint blockade. We suggest determining MSI status in combination with HLA class I and II antigen expression in tumors potentially eligible for immune checkpoint blockade even in the absence of conventional markers predictive for anti-PD-1/PD-L1 therapy and in entities not commonly linked to the MSI phenotype. Further studies are required to determine the value of these markers for predicting the success of immune checkpoint blockade.

Hereditary or sporadic polyposis syndromes

Polyposis syndromes are encountered in endoscopy practice, and are considered rare entities, accounting for ≤1% of colorectal cancer. Polyposis can occur within inherited syndromes or as "sporadic" cases of unknown etiology. Their proper characterization is relevant for patient management, and should nowadays drive appropriate genetic tests which have a key role in clinical practice for driving surveillance and colorectal cancer prevention, enlarged to relatives. Polyposis classification is based upon polyp number and histology, familial and personal history. This review will explore the polyposis nosology and their genetic determinants in the emerging scenario of Next Generation Sequencing which allow testing multiples genes in parallel. This capability will likely continue to increase the range of polyposis predisposing genes, contributing to define new clinical entities.