Grant: CIHR-ICR / Cancer Research Society Partnership - Res. Gr. Cancer Prev.

Background: Persistent infection with human papillomavirus (HPV), the most common sexually transmitted infection, causes over 90% of anal cancers and 73% of oropharyngeal cancers. These cancers are rising in Canada, and continue to disproportionately affect gay, bisexual, and other men who have sex with men (GBM), especially those living with HIV, who face a 90 times higher anal cancer risk compared to HIV-negative men. HIV co-infection hinders HPV infection clearance, increasing likelihood to cancer progression. Men are also at higher risk for oropharyngeal cancer compared to women, due to more prevalent risk factors. While the progression from oral HPV infection to oropharyngeal cancer remains poorly understood, the progression from anal HPV infection to anal cancer shares similarities with cervical cancer. It begins with persistent HPV infection, i.e., one that fails to clear after 6-12 months, followed by activation of oncogenic proteins like E6 and E7, which stimulate abnormal cell proliferation, leading to the development of precancerous lesions and eventually invasive cancer. Two viral biomarkers —quantitative viral load and E6/E7 mRNA expression—are important in understanding this mechanism of progression. Quantitative viral load, which measures the amount of HPV DNA, serves as a marker of HPV persistence which is a necessary precursor to progression. The increased expression of viral E6/E7 oncoproteins, shown by higher mRNA levels, signals uncontrolled cellular growth, characteristic of precancerous conditions. While these biomarkers have been shown to correlate with cervical cancer development, their implications for anal cancer and oropharyngeal cancer in men, especially GBM, are not well documented. Moreover, although HPV vaccine effectiveness against these biomarkers has been studied in women, similar research in men is scarce. There are targeted HPV vaccine programs for GBM in Canada, and clinical trials demonstrate vaccine efficacy over 60% for incident/persistent infection among young GBM. However, real-world vaccine effectiveness data are limited for older, sexually active GBM, and for adults living with HIV. We propose to fill these gaps by leveraging a stored collection of biological specimens from Canadian GBM to test for novel viral biomarkers of infections that would be more likely to progress to cancer. This will allow for estimation of vaccine effectiveness against infections with high quantitative viral loads and E6/E7 mRNA expression. Objectives: 1) To measure the viral load and E6/E7 mRNA expression of oncogenic anal and oral HPV types; 2) To identify patient characteristics associated with high anal and oral HPV viral load and E6/E7 mRNA expression; 3) To estimate HPV vaccine effectiveness against anal and oral HPV viral load and E6/E7 mRNA expression. Methods: We propose to conduct further laboratory testing for HPV biomarkers among anal and oral specimens already collected as part of the Engage Cohort Study. We have a longitudinal collection of specimens from 1,914 Canadian GBM (17% living with HIV) aged 16-80 years, who were recruited using respondent-driven sampling from Vancouver, Toronto, and Montreal. GBM provided anal swabs and oral rinses for yearly HPV genotyping for up to five years (2017-2024). They completed questionnaires every 6 months, including self-reported HPV vaccination status. We are seeking funding to conduct further laboratory testing for quantitative viral load and E6/E7 mRNA expression of the specimens that were positive for oncogenic HPV genotypes (37%) using quantitative real-time polymerase chain reaction.