Objectives: A large number of genetic and epigenetic alterations have been found in gastric cancer, but there is remarkably little consensus on the value of individual biomarker in diagnosis and prognosis of this cancer. This study was designed to illustrate the value of PIK3CA amplification in combination with promoter methylation of RASSF1A and PAX6 genes in early diagnosis and prognosis of gastric cancer.
Design and methods: Using real-time quantitative PCR, quantitative methylation-specific PCR (Q-MSP), and methylation-specific PCR (MSP) assays, we examined PIK3CA amplification and promoter methylation of RASSF1A and PAX6 genes in a cohort of gastric cancers, and explored the association of various (epi)genotypes with clinical outcomes of gastric cancer patients.
Results: We demonstrated that PIK3CA gene was specifically amplified in gastric cancers, but not in normal gastric tissues. Moreover, frequent methylation of RASSF1A and PAX6 was also found in gastric cancers. Given the patients harboring diverse (epi)genotypes, we thus investigated the effect of various (epi)genotypes on poor prognosis in gastric cancer. The data showed that concomitant PIK3CA amplification and RASSF1A or PAX6 methylation were closely associated with poor clinical outcomes, particularly survival, as compared to other (epi)genotypes in gastric cancer.
Conclusions: We found frequent PIK3CA amplification and promoter methylation of RASSF1A and PAX6 genes in gastric cancers, and demonstrated that concomitant PIK3CA amplification and promoter methylation in any one of these two genes were significantly associated with worse survival in gastric cancer. Collectively, such (epi)genotypes may be strong and independent poor prognostic factors for gastric cancer patients.