Lynch syndrome accounts for 3-5% of colorectal cancers and is due to a germline mutation in one of the mismatch repair genes MLH1, MSH2, MSH6, and PMS2.
Mutations in the adenomatous polyposis coli (APC) gene initiate the majority of both sporadic and hereditary colorectal cancers (CRC) and around 30% of these mutations are nonsense mutations.
Current clinical guidelines recommend mutation analysis for select codons in KRAS and NRAS exons 2, 3, and 4 and BRAF V600E to guide therapy selection and prognostic stratification in advanced colorectal cancer.
Immunohistochemistry (IHC) for DNA mismatch repair proteins MLH1, PMS2, MSH2, and MSH6 is used for microsatellite instability (MSI) screening in colorectal carcinoma (CRC) and endometrial carcinoma (EC).
Defects in MMR genes are known to be crucial for familial form of colorectal cancer but our findings suggest that specific genetic variations in MLH1 are important also in the individual predisposition to sporadic colon cancer.
Colorectal cancer (CRC) development is characterized by the stepwise accumulation of mutations over time, of which mutations in the tumor suppressor APC are often very early to occur.
In Denmark, the national HNPCC register has been granted an exception to send unsolicited letters with information on hereditary colorectal cancer and an invitation to genetic counseling to members of families with familial and hereditary colorectal cancer.
In this retrospective study for quality assessment of a next-generation sequencing assay, we examined BRAF, KRAS, and NRAS genes within the mitogen-activated protein kinase (MAPK) pathway and the PIK3CA gene within the phosphatidylinositol 3-kinase (mTOR) pathway in 744 CRC specimens submitted to our clinical diagnostics laboratory.
IMPLICATIONS: The tumor-suppressive function of APC, the most frequently mutated gene in colorectal cancer, is mainly attributed to its role in β-catenin/Wnt signaling.
We have used SW48 and LIM1215 human colon cancer cell lines, quadruple wild-type for KRAS, NRAS, BRAF and PI3KCA genes, and their HER2-amplified (LIM1215-HER2 and SW48-HER2) derived cells to perform in vitro and in vivo studies in order to identify novel therapeutic strategies in HER2 gene amplified human colorectal cancer.
Of the 363 patients in the initial cohort, 11(3.0%) harbored oncogenic fusions and were all mismatch repair-deficient colorectal carcinomas with hypermethylated MLH1 and wild-type BRAF and KRAS, comprising 55% (11/20) of this subgroup.
Mutational status for KRAS, NRAS, and BRAF genes should be performed on all colorectal carcinoma (CRC) specimens in order to guide targeted therapy selection for metastatic disease.
We compared the development of (advanced) adenomas and CRC among patients with pathogenic variants in the DNA mismatch repair genes MLH1 (n=55), MSH2 (n=44), MSH6 (n=143), or PMS2 (n=22) over 1836 years of follow-up (median follow-up of 6 years per patient).
Colorectal cancers (CRCs) initiate through distinct mutations, including in APC pathway components leading to tubular adenomas (TAs); in BRAF, with epigenetic silencing of CDX2, leading to serrated adenomas (SAs); and in the DNA mismatch repair machinery driving microsatellite instability (MSI).
The three pathogenic variants included two colorectal cancers with MLH1 loss and high MSI and one endometrial cancer with MSH6 loss and microsatellite stability.