Germline mutation and protein expression analysis of mismatch repair genes MSH6 and PMS2 in Malaysian Lynch syndrome patients

Molecular approach to genetic and epigenetic pathogenesis of early-onset colorectal cancer

Colorectal cancer (CRC) is the third most frequent cancer type and the incidence of this disease is increasing gradually per year in individuals younger than 50 years old. The current knowledge is that early-onset CRC (EOCRC) cases are heterogeneous population that includes both hereditary and sporadic forms of the CRC. Although EOCRC cases have some distinguishing clinical and pathological features than elder age CRC, the molecular mechanism underlying the EOCRC is poorly clarified. Given the significance of CRC in the world of medicine, the present review will focus on the recent knowledge in the molecular basis of genetic and epigenetic mechanism of the hereditary forms of EOCRC, which includes Lynch syndrome, Familial CRC type X, Familial adenomatous polyposis, MutYH-associated polyposis, Juvenile polyposis syndrome, Peutz-Jeghers Syndrome and sporadic forms of EOCRC. Recent findings about molecular genetics and epigenetic basis of EOCRC gave rise to new alternative therapy protocols. Although exact diagnosis of these cases still remains complicated, the present review paves way for better predictions and contributes to more accurate diagnostic and therapeutic strategies into clinical approach.

Polymorphisms of cell cycle regulator genes CCND1 G870A and TP53 C215G: Association with colorectal cancer susceptibility risk in a Malaysian population

Colorectal cancer (CRC) occurs as a more common sporadic form and a less common familial form. Our earlier analysis of germline mutations of mismatch repair genes confirmed only 32% of familial CRC cases as Lynch syndrome cases. It was hypothesized that the remaining familial aggregation may be 'polygenic' due to single nucleotide polymorphisms (SNPs) of low penetrance genes involved in cancer predisposition pathways, such as cell cycle regulation and apoptosis pathways. The current case-control study involving 104 CRC patients (52 sporadic and 52 familial) and 104 normal healthy controls investigated the contribution of the SNPs cyclin D1 (CCND1) G870A and tumor protein p53 (TP53) C215G in modulating familial and sporadic CRC susceptibility risk. DNA was extracted from peripheral blood and the polymorphisms were genotyped by employing a polymerase chain reaction-restriction fragment length polymorphism method. The association between these polymorphisms and CRC susceptibility risk was calculated using a binary logistic regression analysis and deriving odds ratios (ORs). The A/A variant genotype of CCND1 and G/G variant genotype of TP53 exhibited a significantly greater association with the risk of sporadic CRC [CCND1: OR, 3.471; 95% confidence interval (CI), 1.443-8.350; P=0.005. TP53: OR, 2.829; CI, 1.119-7.152; P=0.026] as well as familial CRC susceptibility (CCND1: OR, 3.086; CI, 1.270-7.497; P=0.019. TP53: OR, 3.048; CI, 1.147-8.097; P=0.030). The results suggest a potential role of the SNPs CCND1 G870A and TP53 C215G in the modulation of sporadic and familial CRC susceptibility risk.