Purpose: Role and timing of frameshift mutations during carcinogenesis in hereditary nonpolyposis colorectal cancer have not been examined. This study was designed to clarify the relationship between frameshift mutations and clinicopathologic features in colorectal cancer from patients with hereditary nonpolyposis colorectal cancer.
Methods: Thirty-one colorectal cancers from patients with hereditary nonpolyposis colorectal cancer at different clinicopathologic stages were analyzed for frameshift mutation in 18 genes.
Results: The frameshift mutations of the ACVR2 and PTHLH genes were found to have an extremely high frequency (94-100 percent) in all pathologic stages, and mutation of the MARCKS gene also was high (94 percent) in Dukes B and C cancers. These frequencies were higher than the frequency of TGFbetaRII gene inactivation (64-88 percent). Mutations of the hMSH3, TCF4, CASP5, RIZ, RAD50, and MBD4 genes were comparatively frequent (>35 percent) in all stages. Frequencies of inactivation of the MARCKS, BAX, IGFIIR, and PTEN genes were significantly higher in Dukes B and C cancers than in Dukes A cancer (P < 0.05). The number of accumulated frameshift mutations was larger in Dukes B and C cancers (9.4) than in Dukes A cancer (6.8) (P = 0.003).
Conclusions: The present data suggest that the disruption of the transforming growth factor-beta super-family signaling pathway by the alteration of the ACVR2 and/or TGFbetaRII genes and the disruption of antiproliferative function by the PTHLH gene alteration contribute to the development of early colorectal cancer. Moreover, the further accumulation of alterations in the MARCKS, BAX, IGFIIR, and PTEN genes seem to be associated with progression from early to advanced colorectal cancer from patients with hereditary nonpolyposis colorectal cancer.