Human Papillomavirus DNA and Oncogene Alterations in Colorectal Tumors

The aim of the present study is to determine the presence and molecular integrity of high-risk HPV types in colorectal adenocarcinomas and to assess whether viral DNA is related to common proto-oncogene alterations, such as k- ras mutations and c- myc gene amplification, in colorectal cancer. Seventy-five colorectal adenocarcinomas were screened for HPV infection using nested-PCR (MY09/11-GP5+/6+). HPV typing was performed by type-specific PCR for HPV 16 and HPV 18 DNA. Unidentified samples were subsequently sequenced to determine the viral genotype. The physical status of HPV was determined by a nested PCR approach for type-specific E2 sequences. C- myc amplification was assessed by co-amplification with β- globin as control locus, and mutation in k- ras codons 12 and 13 by ARMS-PCR. Overall, HPV was detected in thirty-three colorectal specimens (44%). HPV 16 was the prevalent type (16/75), followed by HPV 18 (15/75), HPV 31 (1/75) and HPV 66 (1/75). E2 disruption was detected in 56.3% of HPV 16 and in 40% of HPV 18 positive tumors. C- myc amplification was detected in 29.4% of cases, while k- ras mutations in 30.7%. There was no significant trend for HPV infection in tumors harboring either k- ras or c- myc alterations. This study demonstrates HPV DNA and viral integration in colorectal tumors, suggesting a potential role of this virus in colorectal carcinogenesis. There was no concurrence, however, of k- ras and c- myc activation with viral infection.