HPV is an oncogenic virus that is essential to the development of cervical cancer and is strongly associated with several other anogenital malignancies. HPV promotes oncogenesis via viral proteins E6 and E7. These interfere with tumor suppressor proteins p53 and pRb and induce telomerase, thereby immortalizing cells. Thus, HPV-related tumors infrequently contain p53 mutations. HPV DNA is present in tumor tissue of HPV- related cancers, and carcinogenesis via HPV occurs through persistent infection with """"""""high-risk"""""""" (types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73, 82) strains of HPV. Since colorectal cancer originates in epithelial cells, and the anal canal, a site known to be associated with HPV-related malignancies, leads directly into the rectum and colon, several studies have examined colorectal neoplastic tissue for HPV DNA. Although recent case-control studies were small, with the largest study having just 72 cases, all have found positive associations between HPV and colorectal neoplasia. These studies suggest a possible association between HPV and colorectal cancer. However, further investigation is needed to validate these findings and explore the nature of this association. Since multiple pathways involving host genetics and environmental factors play roles in colorectal cancer carcinogenesis, it is likely that any association between HPV and colorectal cancer will be confined to specific subsets of colorectal cancer. Therefore, we propose to conduct a case-case comparison study of localized colorectal cancer cases to determine the association between high-risk HPV infection and tumor characteristics including: p53 mutation status, microsatellite-instability (MSI) status, and tumor location (proximal colon, distal colon and rectum). In addition, among cases of localized colorectal cancer, we will determine the association between colorectal HPV infection and personal characteristics, including: gender, age and smoking status. The proposed study will include 554 incident cases of localized colorectal cancer ages 20-74 occurring between January 1998 and June 2002 from the population-based Seattle Colorectal Cancer Family Registry (Seattle CCFR). We limited our sample to localized cases, because localized cases are often treated via surgery rather than radiation which could alter tumor DNA resulting in misclassification of p53 mutation status. For each case, investigators collected tumor tissue samples, pathology data, and data from a standardized telephone interview assessing known and suspect colorectal cancer risk factors. DNA from tumor samples was previously extracted, stored, and characterized for MSI status. We will test these DNA samples for HPV-specific DNA using polymerase chain reaction (PCR)-based methods and conduct HPV genotyping of all HPV positive samples. In addition, we will conduct DNA sequencing of tumor DNA to detect p53 mutations in exons 5-9 of the TP53 gene, where >90% of p53 mutations in cancerous cells occur. Logistic and polytomous regression analyses will be used to control for potential confounding variables and estimate odds ratios and 95% confidence intervals.
Project Narrative Colorectal cancer is the second leading cause of cancer death for both sexes in the United States, and in 2006 there were 148,610 new diagnoses of, and 55,170 deaths from, colorectal cancer. This study will be the first to evaluate the association between human papillomavirus (HPV) and subsets of colorectal cancer in a large, well-characterized, population-based cancer registry. With the recent licensure of an effective vaccine against HPV, it is important to characterize the total burden of disease associated with this virus.
| Burnett-Hartman, Andrea N; Feng, Qinghua; Popov, Viorica et al. (2013) Human papillomavirus DNA is rarely detected in colorectal carcinomas and not associated with microsatellite instability: the Seattle colon cancer family registry. Cancer Epidemiol Biomarkers Prev 22:317-9 |
