Significance of HPV Infection and Genic Mutation of APC and K-ras in Patients with Rectal Cancer


Background: Significance of HPV infection and genic mutation of APC and K-ras in rectal cancer has beeninvestigated but not clarified. The objective of our study was to investigate these parameters in patients with rectalcancer to analyze correlations with biological behaviour, to determine relationships among the three, and alsoto demonstrate survival prognosis effects.
Methods: From December 2007 to September 2008, 75 rectal cancercases confirmed by histopathology in the Tumor Hospital of Xinjiang Medical University were enrolled. Thecontrol group consisted of normal rectal mucous membrane taken simultaneously, a least 10 cm distant from thecarcinoma fringe. HPV DNA, the MCR of APC and exon-1 of K-ras were detected by PCR and PCR-SSCP. Allresults were analyzed in relation to clinical pathological material, using chi-square and correlation analysis viaSPSS.13 and Fisher’s Exact Probability via STATA. 9.0. All 75 patients were followed up for survival analysisusing Kaplan-Meier and Log-rank tests.
Results: 55 out of 75 cases demonstrated gene HPV L1 while it wasnotdetected in normal rectal mucosa tissue. HPV infection was correlated with age and lymphatic metastasis(P<0.05) but not other characteristics, such as ethnicity, tumor size, histological type, tumor type, Duke’s stageand infiltration depth. Some 43 cases exhibited APC genic mutation (57.3%) and 34 K-ras genic mutation(45.3%). APC genic mutation was correlated with gender( P<0.05), but not age, histological type, infiltrationdepth, lymphatic metastasis and Duke’s stage. In 55 cases of rectal cancer with HPV infection, there were 31cases with genic mutation of APC (56.4%) and 24 with genic mutation of K-ras (43.6%). For the 20 cases ofrectal cancer with non-HPV infection, the figures were 12 cases (60%) and 10 (50.0%), respectively, with nosignificant relation. Survival analysis showed no statistical significance for K-ras genic mutation, APC genicmutation or HPV infection (P>0.05). However, the survival time of the patients with HPV infection was a littleshorter than in cases without HPV infection.
Conclusions: Our results suggest that HPV infection might be animportant factor to bring about malignant phenotype of rectal cancer and influence prognosis. Genic mutationof APC and K-ras might be common early molecular events of rectal cancer, but without prognostic effects onmedium-term or early stage patients with rectal cancer.