Variant profiling of colorectal adenomas from three patients of two families with MSH3-related adenomatous polyposis

Compound heterozygous MSH3 germline variants and associated tumor somatic DNA mismatch repair dysfunction

We describe here an individual from a fourth family with germline compound heterozygous MSH3 germline variants and its observed biological consequences. The patient was initially diagnosed with invasive moderately-differentiated adenocarcinoma of the colon at the age of 43. Germline multigene panel testing revealed a pathogenic variant MSH3 c.2436-1 G > A and a variant of (initial) uncertain significance MSH3 c.3265 A > T (p.Lys1089*). Germline genetic testing of family members confirm the variants are in trans with the c.2436-1 G > A variant of paternal and the c.3265 A > T variant of maternal origin. Tumor DNA exhibits low levels of microsatellite instability and elevated microsatellite alterations at selected tetranucleotide repeats (EMAST). Tissue immunohistochemical staining for MSH3 demonstrated variant MSH3 protein is present in the cytoplasm and cell membrane but not in the nucleus of normal and tumor epithelial cells. Furthermore, variant MSH3 is accompanied by loss of nuclear MSH6 and a reduced level of nuclear MSH2 in some tumor cells, suggesting that the variant MSH3 protein may inhibit binding of MSH6 to MSH2.

Unraveling the Role of Molecular Profiling in Predicting Treatment Response in Stage III Colorectal Cancer Patients: Insights from the IDEA International Study

BACKGROUND

This study aimed to investigate the molecular profiles of 237 stage III CRC patients from the international IDEA study. It also sought to correlate these profiles with Toll-like and vitamin D receptor polymorphisms, clinicopathological and epidemiological characteristics, and patient outcomes.

METHODS

Whole Exome Sequencing and PCR-RFLP on surgical specimens and blood samples, respectively, were performed to identify molecular profiling and the presence of Toll-like and vitamin D polymorphisms. Bioinformatic analysis revealed mutational status.

RESULTS

Among the enrolled patients, 63.7% were male, 66.7% had left-sided tumors, and 55.7% received CAPOX as adjuvant chemotherapy. Whole exome sequencing identified 59 mutated genes in 11 different signaling pathways from the Kyoto Encyclopedia of Genes and Genomes (KEGG) CRC panel. On average, patients had 8 mutated genes (range, 2-21 genes). Mutations in ARAF and MAPK10 emerged as independent prognostic factors for reduced DFS (p = 0.027 and p < 0.001, respectively), while RAC3 and RHOA genes emerged as independent prognostic factors for reduced OS (p = 0.029 and p = 0.006, respectively). Right-sided tumors were also identified as independent prognostic factors for reduced DFS (p = 0.019) and OS (p = 0.043). Additionally, patients with tumors in the transverse colon had mutations in genes related to apoptosis, PIK3-Akt, Wnt, and MAPK signaling pathways.

CONCLUSIONS

Molecular characterization of tumor cells can enhance our understanding of the disease course. Mutations may serve as promising prognostic biomarkers, offering improved treatment options. Confirming these findings will require larger patient cohorts and international collaborations to establish correlations between molecular profiling, clinicopathological and epidemiological characteristics and clinical outcomes.

Patterns of Somatic Variants in Colorectal Adenoma and Carcinoma Tissue and Matched Plasma Samples from the Hungarian Oncogenome Program

Analysis of circulating cell-free DNA (cfDNA) of colorectal adenoma (AD) and cancer (CRC) patients provides a minimally invasive approach that is able to explore genetic alterations. It is unknown whether there are specific genetic variants that could explain the high prevalence of CRC in Hungary. Whole-exome sequencing (WES) was performed on colon tissues (27 AD, 51 CRC) and matched cfDNAs (17 AD, 33 CRC); furthermore, targeted panel sequencing was performed on a subset of cfDNA samples. The most frequently mutated genes were APC, KRAS, and FBN3 in AD, while APC, TP53, TTN, and KRAS were the most frequently mutated in CRC tissue. Variants in KRAS codons 12 (AD: 8/27, CRC: 11/51 (0.216)) and 13 (CRC: 3/51 (0.06)) were the most frequent in our sample set, with G12V (5/27) dominance in ADs and G12D (5/51 (0.098)) in CRCs. In terms of the cfDNA WES results, tumor somatic variants were found in 6/33 of CRC cases. Panel sequencing revealed somatic variants in 8 out of the 12 enrolled patients, identifying 12/20 tumor somatic variants falling on its targeted regions, while WES recovered only 20% in the respective regions in cfDNA of the same patients. In liquid biopsy analyses, WES is less efficient compared to the targeted panel sequencing with a higher coverage depth that can hold a relevant clinical potential to be applied in everyday practice in the future.

A large family with MSH3-related polyposis

Biallelic MSH3 germline variants are a rare cause of adenomatous polyposis as yet reported in two small families only. We describe the phenotype of a third family, the largest thus far, with adenomatous polyposis related to compound heterozygous MSH3 pathogenic variants. The index patient was a 55-years old male diagnosed with rectal cancer and adenomatous polyposis (cumulatively 52 polyps), with a family history of colorectal polyposis with unknown cause. Next-generation sequencing and copy number variation analysis of a panel of genes associated with colorectal cancer and polyposis revealed compound heterozygous germline pathogenic variants in the MSH3 gene. Nine out of 11 siblings were genotyped. Three siblings carried the same compound heterozygous MSH3 variants. Colonoscopy screening showed predominantly right-sided adenomatous polyposis in all compound heterozygous siblings, with a cumulative number of adenomas ranging from 18 to 54 in an average of four colonoscopies, and age at first adenoma detection ranging from 46 to 59. Microsatellite analysis demonstrated alterations at selected tetranucleotide repeats (EMAST) in DNA retrieved from the rectal adenocarcinoma, colorectal adenomas as well as of normal colonic mucosa. Gastro-duodenoscopy did not reveal adenomas in any of the four patients. Extra-intestinal findings included a ductal adenocarcinoma in ectopic breast tissue in one female sibling at the age of 46, and liver cysts in three affected siblings. None of the three heterozygous or wild type siblings who previously underwent colonoscopy had adenomatous polyposis. We conclude that biallelic variants in MSH3 are a rare cause of attenuated adenomatous polyposis with an onset in middle age.