Prevalence and spectrum of MLH1, MSH2, and MSH6 pathogenic germline variants in Pakistani colorectal cancer patients

Prevalence and genetic spectrum associated with hereditary colorectal cancer syndromes, the need to improve cancer risk awareness, and family cascade testing in Vietnam

In Vietnam, colorectal cancer is one of the top diagnosed cancers, with 5-10% originating from inherited mutations. This study aims to define the mutation spectrum associated with hereditary colorectal cancer syndromes (HCCS) in Vietnam, evaluate the influence of genetic testing on carriers' awareness, and also investigate the barriers in familial testing. Genetic test reports were collected to identify HCCS cases, then cases underwent a survey investigating self-risk and familial-risk awareness, proactive cancer screening, and familial testing barriers. Participant characteristics, mutation prevalence, and results from the survey were descriptively analyzed and reported. Of all genetic test results, 3% (49/1632) were identified with mutations related to HCCS. Over 77% of them belonged to Lynch syndrome. PMS2 appeared to be the gene with the highest mutation frequency, while MLH1 was the lowest. 44% of cases further undertook cancer screening tests, and 48% of cases' families had uptake genetic testing. The biggest barrier of familial members for not taking genetic test was psychological reasons (fear, not being interested, or not feeling necessary). This study provided new evidence for HCCS mutation spectrum in Vietnamese population and the success in promoting cascade test in high-risk family members through financial and technical support. Also, study has suggested the needs of an innovative genetic testing process focusing on the quality of pre-and post-test consultancy, an increase in follow-ups, and the change in policy for permission of contacting relatives directly to improve the rate of cascade testing and proactive cancer screening.

Systemic Diseases and Gastrointestinal Cancer Risk

Importance

Gastrointestinal (GI) cancers are the second leading cause of cancer-related deaths worldwide.

Observations

The global challenges GI cancers pose are high, especially in middle- and low-income countries. Patients with these cancers present with symptoms of poor appetite, weight loss, heartburn, abdominal pain, fatigue and anaemia. Several risk factors contribute to GI cancers, including age, gender, obesity, pathogenic infections, smoking cigarettes, alcohol consumption and dietary habits. Most of these cancers are sporadic. However, some patients are at high risk due to a family history of GI cancers. Systemic diseases affect multiple organs, and their chronic occurrence elicits inflammatory responses at various sites. These diseases also contribute to GI cancers.

Conclusion and Relevance

In this review, we discuss that untreated systemic diseases, including diabetes, hepatitis, acquired immune deficiency syndrome, ulcers and hypertension, can potentially lead to GI cancers if they remain untreated for a longer period. Systemic diseases initiate oxidative stress, inflammatory pathways and genetic manipulations, which altogether confer risks to GI cancers. Here, we describe the association between systemic diseases and their underlying mechanisms leading to GI cancers.

Assessment of pathogenic variation in gynecologic cancer genes in a national cohort

Population-based estimates of pathogenic variation burden in gynecologic cancer predisposition genes are a prerequisite for the development of effective precision public health strategies. This study aims to reveal the burden of pathogenic variants in a comprehensive set of clinically relevant breast, ovarian, and endometrial cancer genes in a large population-based study. We performed a rigorous manual classification procedure to identify pathogenic variants in a panel of 17 gynecologic cancer predisposition genes in a cohort of 7091 individuals, representing 0.35% of the general population. The population burden of pathogenic variants in hereditary gynecologic cancer-related genes in our study was 2.14%. Pathogenic variants in genes ATM, BRCA1, and CDH1 are significantly enriched and the burden of pathogenic variants in CHEK2 is decreased in our population compared to the control population. We have identified a high burden of pathogenic variants in several gynecologic cancer-related genes in the Slovenian population, most importantly in the BRCA1 gene.

Prevalence and Genotype-Phenotype Correlation of Lynch Syndrome in a Selected High-Risk Cohort from Qatar’s Population

Lynch syndrome (LS) is the most common cause of hereditary colorectal cancers (CRC) and is associated with an increased risk for ovarian and endometrial cancers. There is lack of knowledge on the epidemiology of LS in the non-Caucasian populations especially in Qatar. The aim of this retrospective study is to explore the prevalence of LS in a selected high-risk cohort in the State of Qatar in addition to investigating the frequency and genotype-phenotype correlation associated with mismatch repair genes pathogenic variants. Retrospective review of medical records of 31 individuals with LS, 20 affected with colorectal cancer and 11 unaffected with family history of cancers, referred from January 2017 until August 2020. The prevalence of LS among affected and unaffected patients is 22% (20/92) and 2.2% respectively. Among affected individuals, MLH1 and MSH2 genes were highly frequent while for unaffected individuals, a recurrent PMS2 pathogenic variant was reported in several related individuals suggesting a tribal effect. This study highlights the epidemiology of LS in high-risk cohort in Qatar which helps to provide recommendations on genetic testing, and personalize surveillance and management programs

Colorectal Cancer in North-Eastern Iran: a retrospective, comparative study of early-onset and late-onset cases based on data from the Iranian hereditary colorectal cancer registry

BACKGROUND

The incidence rate of colorectal cancer (CRC) is increasing among patients below 50 years of age. The reason for this is unclear, but could have to do with the fact that indicative variables, such as tumour location, gender preference and genetic preponderance have not been followed up in a consistent mann er. The current study was primarily conducted to improve the hereditary CRC screening programme by assessing the demographic and clinicopathological characteristics of early-onset CRC compared to late-onset CRC in northeast Iran.

METHODS

This retrospective study, carried out over a three-year follow-up period (2014-2017), included 562 consecutive CRCs diagnosed in three Mashhad city hospital laboratories in north-eastern Iran. We applied comparative analysis of pathological and hereditary features together with information on the presence of mismatch repair (MMR) gene deficiency with respect to recovery versus mortality. Patients with mutations resulting in absence of the MMR gene MLH1 protein product and normal BRAF status were considered to be at high risk of Lynch syndrome (LS). Analyses using R studio software were performed on early-onset CRC (n = 222) and late-onset CRC (n = 340), corresponding to patients ≤50 years of age and patients > 50 years.

RESULTS

From an age-of-onset point of view, the distribution between the genders differed with females showing a higher proportion of early-onset CRC than men (56% vs. 44%), while the late-onset CRC disparity was less pronounced (48% vs. 52%). The mean age of all participants was 55.6 ± 14.8 years, with 40.3 ± 7.3 years for early-onset CRC and 65.1 ± 9.3 years for late-onset CRC. With respect to anatomical tumour location (distal, rectal and proximal), the frequencies were 61, 28 and 11%, respectively, but the variation did not reach statistical significance. However, there was a dramatic difference with regard to the history of CRC in second-degree relatives between two age categories, with much higher numbers of family-related CRCs in the early-onset group. Expression of the MLH1 and PMS2 genes were significantly different between recovered and deceased, while this finding was not observed with regard to the MSH6 and the MSH2 genes. Mortality was significantly higher in those at high risk of LS.

CONCLUSION

The variation of demographic, pathological and genetic characteristics between early-onset and late-onset CRC emphasizes the need for a well-defined algorithm to identify high-risk patients.

Co-Occurrence of Familial Non-Medullary Thyroid Cancer (FNMTC) and Hereditary Non-Polyposis Colorectal Cancer (HNPCC) Associated Tumors-A Cohort Study

Familial non-medullary thyroid cancer (FNMTC) is a form of endocrine malignancy exhibiting an autosomal dominant mode of inheritance with largely unknown germline molecular mechanism. Hereditary nonpolyposis colorectal cancer syndrome (HNPCC) is another hereditary autosomal dominant cancer syndrome which, if proven to be caused by germline mutations in mismatch repair genes (MMR)-MLHL, MSH2, MSH6, PMS2, and EPCAM-is called Lynch syndrome (LS). LS results in hereditary predisposition to a number of cancers, especially colorectal and endometrial cancers. Tumors in LS are characterized by microsatellite instability (MSI) and/or loss of MMR protein expression in immunohistochemistry (IHC). MSI is a rare event in thyroid cancer (TC), although it is known to occur in up to 2.5% of sporadic follicular TC cases. There are limited data on the role of germline MMR variants FNMTC. The goal of this study was to analyze the potential clinical and molecular association between HNPCC and FNMTC. We performed a cohort study analyzing the demographic, clinical, and pathologic data of 43 kindreds encompassing 383 participants (104 affected, 279 unaffected), aged 43.5 [7-99] years with FNMTC, and performed high-throughput whole-exome sequencing (WES) of peripheral blood DNA samples of selected 168 participants (54 affected by FNMTC and 114 unaffected). Total affected by thyroid cancer members per family ranged between 2 and 9 patients. FNMTC was more prevalent in women (68.3%) and characterized by a median tumor size of 1.0 [0.2-5.0] cm, multifocal growth in 44%, and gross extrathyroidal extension in 11.3%. Central neck lymph node metastases were found in 40.3% of patients at presentation, 12.9% presented with lateral neck lymph node metastases, and none had distant metastases. Family history screening revealed one Caucasian family meeting the clinical criteria for FNMTC and HNPCC, with five members affected by FNMTC and at least eight individuals reportedly unaffected by HNPCC-associated tumors. In addition, two family members were affected by melanoma. Genome Analysis Tool Kit (GATK) pipeline was used in variant analysis. Among 168 sequenced participants, a heterozygous missense variant in the MSH2 gene (rs373226409; c.2120G>A; p.Cys707Tyr) was detected exclusively in FNMTC- HNPCC- kindred. In this family, the sequencing was performed in one member affected by FNMTC, HPNCC-associated tumors and melanoma, one member affected solely by HNPCC-associated tumor, and one member with FNMTC only, as well as seven unaffected family members. The variant was present in all three affected adults, and in two unaffected children of the affected member, under the age of 18 years, and was absent in non-affected adults. This variant is predicted to be damaging/pathogenic in 17/20 in-silico models. However, immunostaining performed on the thyroid tumor tissue of two affected by FNMTC family members revealed intact nuclear expression of MSH2, and microsatellite stable status in both tumors that were tested. Although the MSH2 p.Cys707Tyr variant is rare with a minor allele frequency (MAF) of 0.00006 in Caucasians; it is more common in the South Asian population at 0.003 MAF. Therefore, the MSH2 variant observed in this family is unlikely to be an etiologic factor of thyroid cancer and a common genetic association between FNMTC and HNPCC has not yet been identified. This is the first report known to us on the co-occurrence of FNMTC and HNPCC. The co-occurrence of FNMTC and HNPCC-associated tumors is a rare event and although presented in a single family in our large FNMTC cohort, a common genetic background between the two comorbidities could not be established.

Overview on population screening for carriers with germline mutations in mismatch repair (MMR) genes in China

DNA mismatch repair (MMR) genes play an important role in maintaining genome stability. Germline mutations in MMR genes disrupt the mismatch repair function and cause genome instability. Carriers with MMR germline mutations are more likely to have MMR deficiency and microsatellite instability (MSI) than non-carriers and are prone to develop colorectal cancer (CRC) and extracolorectal malignancies, known as Lynch syndrome (LS). MMR gene testing for suspected mutation carriers is a reliable method to identify the mutation types and to discover mutation carriers. Given that carriers of MMR germline mutations have a higher risk of LS-related cancers (LS-RC) and a younger age at onset than non-carriers, early surveillance and regular screening of relevant organs of carriers are very important for early detection of related cancers. This review mainly focuses on the general status of MMR carriers, the approaches for early detection and screening, and the surveillance of MMR mutation carriers in China. Population screening of MMR germline mutation carriers in China will be helpful for early detection, early diagnosis and treatment of MMR mutation carriers, which may improve the 5-year survival, and reduce mortality and incidence rate in the long term.

Correlation of MSH2 exonic deletions and protein downregulation with breast cancer biomarkers and outcome in Pakistani women/patients

Mismatch repair (MMR) pathway is one of the underlying mechanisms of predisposition to breast cancer (BC). The present study explored the association of MSH2 exonic deletions, respective survival analysis, protein structure prediction, transcription profiling, and expression analysis with BC risk. Genotyping analysis of 493 BC cases and 387 controls confirmed the association of two MSH2 exonic deletions, i.e., exon 3 (OR:6.4, CI = 3.4-12.1) and 9 (OR:7.8, CI = 4.1-14.8) with BC risk. In order to confirm the phenotypic-genotypic relationship, we have performed MSH2 transcriptomic (p < 0.05) and protein expression analysis (OR:30, CI = 4-230) which further confirmed its downregulation/loss in BC biopsy samples highlighting potential role in the onset of breast carcinogenesis. Additionally, we have presented that MSH2 mutations can alter the expression profile of other BC associated biomarkers like ER, PR, CK-7, GATA-3, and E-cadherin. Subsequently, the effect of exonic deletions on secondary structure of protein has shown missing of beta and alpha helices in their protein products via in-silico analysis. However, loss of exon 3 results in the altered core protein structure leading to dysfunction protein, possible cause of BC development. No association of MSH2 exonic deletions with survival statistics was observed conceivably due to the shorter follow-up time. Thus, our results at genetic, transcriptomic, and proteomic levels confirmed the downregulated MSH2, emphasizing its potential contribution in MMR mechanisms for breast tumorigenesis. In conclusion, MSH2 deficiency may cause breast cancer development and progression.