Novel germline MSH2 mutation in lynch syndrome patient surviving multiple cancers

Interventions to support patients with sharing genetic test results with at-risk relatives: a synthesis without meta-analysis (SWiM)

Whilst the finding of heritable susceptibility to disease was once relatively rare, mainstreaming of genetic testing has resulted in a steady increase. Patients are often encouraged to share their genetic test results with relevant relatives, but relatives may not receive this information, leaving them without knowledge of their own risk. Therefore, strategies to help communicate such information are important. This review aimed to explore the efficacy of existing interventions to improve the sharing of genetic test results. A synthesis without meta-analysis design was used. A systematic search of Medline, CINAHL, PsychINFO, and AMED was conducted, and five studies were identified worldwide. Data were extracted for each study regarding study aim, participant characteristics, condition, intervention details, comparison, study duration, outcome measures, theory and behaviour change techniques used. Limited efficacy and application of theory was found. Knowledge, motivation and self-efficacy were not increased in any intervention. No gender differences in communication behaviour were encountered in interventions that recruited men and women. Two studies reported an evaluation of acceptability, which showed that the interventions were well received by patients and health professionals. No study reported the involvement of the target population in any phase of intervention development. Given the lack of health psychology-informed interventions in this area of clinical genetics, we recommend genetic health professionals, health psychologists and patients collaborate on all stages of future interventions that involve the cascading of genetic health information within families. We also provide guidance regarding use of theory and intervention elements for future intervention development.

Whole-genome sequencing identified novel mutations in a Chinese family with lynch syndrome

Background

Lynch syndrome (LS) is caused by a germline mutation in one of the mismatch repair genes (MLH1, MSH2, MSH6, and PMS2) or in the EPCAM gene. The definition of Lynch syndrome is based on clinical, pathological, and genetic findings. Therefore, the identification of susceptibility genes is essential for accurate risk assessment and tailored screening programs in LS monitoring.

Patients and methods

In this study, LS was diagnosed clinically in a Chinese family using Amsterdam II criteria. To further explore the molecular characteristics of this LS family, we performed whole genome sequencing (WGS) to 16 members in this family and summarized the unique mutational profiles within this family. We also used Sanger sequencing technology and immunohistochemistry (IHC) to verify some of the mutations identified in the WGS analysis.

Results

We showed that mutations in mismatch repair (MMR) related genes, as well as pathways including DNA replication, base excision repair, nucleotide excision repair, and homologous recombination were enhanced in this family. Two specific variants, MSH2 (p.S860X) and FSHR (p.I265V) were identified in all five members with LS phenotypes in this family. The MSH2 (p.S860X) variant is the first reported variant in a Chinese LS family. This mutation would result in a truncated protein. Theoretically, these patients might benefit from PD-1 (Programmed death 1) immune checkpoint blockade therapy. The patients who received nivolumab in combination with docetaxel treatments are currently in good health.

Conclusion

Our findings extend the mutation spectrum of genes associated with LS in MLH2 and FSHR, which is essential for future screening and genetic diagnosis of LS.

Colon Tumors in Enterotoxigenic Bacteroides fragilis (ETBF)-Colonized Mice Do Not Display a Unique Mutational Signature but Instead Possess Host-Dependent Alterations in the APC Gene

Enterotoxigenic Bacteroides fragilis (ETBF) is consistently found at higher frequency in individuals with sporadic and hereditary colorectal cancer (CRC) and induces tumorigenesis in several mouse models of CRC. However, whether specific mutations induced by ETBF lead to colon tumor formation has not been investigated. To determine if ETBF-induced mutations impact the Apc gene, and other tumor suppressors or proto-oncogenes, we performed whole-exome sequencing and whole-genome sequencing on tumors isolated after ETBF and sham colonization of Apcmin/+ and Apcmin/+Msh2fl/flVC mice, as well as whole-genome sequencing of organoids cocultured with ETBF. Our results indicate that ETBF-induced tumor formation results from loss of heterozygosity (LOH) of Apc, unless the mismatch repair system is disrupted, in which case, tumor formation results from new acquisition of protein-truncating mutations in Apc. In contrast to polyketide synthase-positive Escherichia coli (pks+ E. coli), ETBF does not produce a unique mutational signature; instead, ETBF-induced tumors arise from errors in DNA mismatch repair and homologous recombination DNA damage repair, established pathways of tumor formation in the colon, and the same genetic mechanism accounting for sham tumors in these mouse models. Our analysis informs how this procarcinogenic bacterium may promote tumor formation in individuals with inherited predispositions to CRC, such as Lynch syndrome or familial adenomatous polyposis (FAP). IMPORTANCE Many studies have shown that microbiome composition in both the mucosa and the stool differs in individuals with sporadic and hereditary colorectal cancer (CRC). Both human and mouse models have established a strong association between particular microbes and colon tumor induction. However, the genetic mechanisms underlying putative microbe-induced colon tumor formation are not well established. In this paper, we applied whole-exome sequencing and whole-genome sequencing to investigate the impact of ETBF-induced genetic changes on tumor formation. Additionally, we performed whole-genome sequencing of human colon organoids exposed to ETBF to validate the mutational patterns seen in our mouse models and begin to understand their relevance in human colon epithelial cells. The results of this study highlight the importance of ETBF colonization in the development of sporadic CRC and in individuals with hereditary tumor conditions, such as Lynch syndrome and familial adenomatous polyposis (FAP).

A Pan-Cancer Analysis on the Systematic Correlation of MutS Homolog 2 (MSH2) to a Malignant Tumor

MutS homolog 2 (MSH2) is a crucial participant in human DNA repair, and lots of the studies functionally associated with it were begun with hereditary nonpolyposis colorectal cancer (HNPCC). MSH2 has also been reported to take part in the progresses of various tumors' formation. With the help of GTEx, CCLE, and TCGA pan-cancer databases, the analysis of MSH2 gene distribution in both tumor tissues and normal control tissues was carried out. Kaplan-Meyer survival plots and COX regression analysis were conducted for the assessment into the MSH2's impact on tumor patients' clinical prognosis. In an investigation to the association of MSH2 expression with immune infiltration level of various tumors and a similar study on tumor immune neoantigens, microsatellite instability was subsequently taken. It was found that high expression of MSH2 is prevalent in most cancers. MSH2's efficacy on clinical prognosis as well as immune infiltration in tumor patients revealed a fact that expression of MSH2 in prostate adenocarcinoma (PRAD), brain lower-grade glioma (LGG), breast-invasive carcinoma (BRCA), and head and neck squamous cell carcinoma (HNSC) posed a significant correlation with the immune cell infiltration level of patients. Likewise as above, MSH2's expression comes in a similar trend with tumor immune neoantigens and microsatellite instability. MSH2's expression in the majority of tumors is a direct factor to the activation of tumor-associated pathways as well as immune-associated pathways. MSH2's early screening or even therapeutic target role for sarcoma (SARC) diagnosis is contributing to the efficiency of early screening and overall survival in SARC patients.

Novel Genetic Markers for Early Detection of Elevated Breast Cancer Risk in Women

This study suggests that two newly discovered variants in the MSH2 gene, which codes for a DNA mismatch repair (MMR) protein, can be associated with a high risk of breast cancer. While variants in the MSH2 gene are known to be linked with an elevated cancer risk, the MSH2 gene is not a part of the standard kit for testing patients for elevated breast cancer risk. Here we used the results of genetic testing of women diagnosed with breast cancer, but who did not have variants in BRCA1 and BRCA2 genes. Instead, the test identified four variants with unknown significance (VUS) in the MSH2 gene. Here, we carried in silico analysis to develop a classifier that can distinguish pathogenic from benign mutations in MSH2 genes taken from ClinVar. The classifier was then used to classify VUS in MSH2 genes, and two of them, p.Ala272Val and p.Met592Val, were predicted to be pathogenic mutations. These two mutations were found in women with breast cancer who did not have mutations in BRCA1 and BRCA2 genes, and thus they are suggested to be considered as new bio-markers for the early detection of elevated breast cancer risk. However, before this is done, an in vitro validation of mutation pathogenicity is needed and, moreover, the presence of these mutations should be demonstrated in a higher number of patients or in families with breast cancer history.

Whole-exome sequencing identified a novel mutation of MLH1 in an extended family with lynch syndrome

Hereditary nonpolyposis colorectal cancer or Lynch syndrome is autosomal dominant cancer predisposition syndrome characterized by early onset of colorectal cancer and neoplasia in other organs. This condition typically caused by germline mutations in the mismatch repair genes MLH1, MSH2, MSH6, and PMS2. To date, a considerable number of MLH1 gene mutations have been found to be associated with Lynch syndrome. We were aimed at identifying a genetic mutation in an extended Iranian family affected by Lynch syndrome-related cancers. Here, we applied whole-exome sequencing to identifying mutation in the proband. Furthermore, we applied Sanger sequencing to validate the candidate variant. We found a heterozygous novel single nucleotide deletion (c.206delG) in the exon two of the MLH1 gene in the proband. Also, Sanger sequencing analysis showed that this mutation has segregated in all affected family members. The mutation (c.206delG:p.R69fs) may create a premature stop codon followed by the formation of a truncated (p.R69fs) Mlh1 protein. Our findings expand the mutational spectra of MLH1 gene related Lynch syndrome which is vital for screening and genetic diagnosis of the disease.

Combined analysis of three Lynch syndrome cohorts confirms the modifying effects of 8q23.3 and 11q23.1 in MLH1 mutation carriers

Two colorectal cancer (CRC) susceptibility loci have been found to be significantly associated with an increased risk of CRC in Dutch Lynch syndrome (LS) patients. Recently, in a combined study of Australian and Polish LS patients, only MLH1 mutation carriers were found to be at increased risk of disease. A combined analysis of the three data-sets was performed to better define this association. This cohort-study includes three sample populations combined totaling 1,352 individuals from 424 families with a molecular diagnosis of LS. Seven SNPs, from six different CRC susceptibility loci, were genotyped by both research groups and the data analyzed collectively. We identified associations at two of the six CRC susceptibility loci in MLH1 mutation carriers from the combined LS cohort: 11q23.1 (rs3802842, HR = 2.68, p ≤ 0.0001) increasing risk of CRC, and rs3802842 in a pair-wise combination with 8q23.3 (rs16892766) affecting age of diagnosis of CRC (log-rank test; p ≤ 0.0001). A significant difference in the age of diagnosis of CRC of 28 years was observed in individuals carrying three risk alleles compared to those with 0 risk alleles for the pair-wise SNP combination. A trend (due to significance threshold of p ≤ 0.0010) was observed in MLH1 mutation carriers towards an increased risk of CRC for the pair-wise combination (p = 0.002). This study confirms the role of modifier loci in LS. We consider that LS patients with MLH1 mutations would greatly benefit from additional genotyping of SNPs rs3802842 and rs16892766 for personalized risk assessment and a tailored surveillance program.