Colorectal cancer is usually considered a disease of the elderly. However, a small fraction of patients develops colorectal cancer earlier. The aim of our study was to define the frequency of known hereditary colorectal syndromes and to characterise genetic and epigenetic features of early nonhereditary tumors. Thirty-three patients ≤40 years with diagnosis of colorectal cancer and 41 patients with disease at >60 years of age were investigated for MSI, Mismatch Repair proteins expression,KRASandBRAFmutations, hypermethylation, and LINE-1 hypomethylation. Detection of germline mutations was performed in Mismatch Repair,APCandMUTYHgenes. Early onset colorectal cancer showed a high incidence of hereditary forms (18%).KRASmutations were detected in 36% of early nonhereditary tumors. Early onset colorectal cancer disclosed an average number of methylated genes significantly lower when compared to the controls (p=0.02). Finally both of the two groups were highly methylated inESR1,GATA5, andWT1genes and were similar for LINE-1 hypomethylation. The genetic make-up of carcinomas differs from young to elderly patients. Early onset tumors showed more frequently a constitutional defective of Mismatch Repair System and a minor number of methylated genes. Hypermethylation ofESR1,GATA5, andWT1genes suggests possible markers in the earlier diagnosis of colorectal tumorigenesis.
Defective mismatch repair in extracts of colorectal and endometrial cancer cell lines exhibiting microsatellite instability.
