Viewing Native American Cervical Cancer Disparities through the Lens of the Vaginal Microbiome

PROJECT CO-LEADERS:

Greg Caporaso PhD, Northern Arizona University

Melissa Herbst-Kralovetz, PhD, University of Arizona Cancer Center

Naomi Lee, PhD, Northern Arizona University

Infection with high-risk types of human papillomavirus (HPV), the most common sexually transmitted infections (STI) worldwide that disproportionately affects women, is the primary cause of cervical intraepithelial neoplasia (CIN) and cervical carcinoma. Why some women infected with HPV clear the infection while others experience persistent HPV infection that progresses to cervical dysplasia and/or carcinoma has not yet been determined. Evidence suggests an association between high-risk (hr) HPV genotypes and altered vaginal microbiota (VMB) composition, indicating that the bacterial species comprising the VMB may contribute to HPV persistence and carcinogenesis. The VMB constitution can positively or negatively affect the host response to HPV infection and the vaginal microenvironment, and as such, may reduce or enhance susceptibility to HPV and cancer. Importantly, the incidence rate of cervical cancer in American Indian/Alaska Native (AI/AN) women is nearly twice as high as that of white women. Recently, compositional differences in the VMB across diverse socioeconomic or ethnic/racial groups were described, although no prior studies have included an AI/AN population. Given that the VMB may not only be associated with HPV persistence and cancer progression but also may differ across racial/ethnic groups, VMB may plausibly be an important link to understanding cervical cancer disparities in AI/AN women.

Our underlying hypothesis is that the VMB functions as a key regulator of mucosal inflammation in the female reproductive tract (FRT) that could affect the development of precancerous lesions and progression to invasive disease. Vaccination is protective against HPV infection. While efforts to increase HPV vaccination in AI/AN have been successful, low rates of cervical cancer screening or failure to be screened likely contribute to cervical cancer rate disparities in AI/AN women. It is clear that the VMB plays a critical role in maintaining mucosal homeostasis. We hypothesize that a shift in the composition of the vaginal microbial community in HPV-positive women leads to the induction of mucosal inflammation in the lower FRT, subsequent promotion of HPV-mediated progression of cervical dysplasia and ultimately invasive cancer. We have assembled an Arizona-based team of translational and clinical researchers to address the role of the VMB and inflammation in cervical cancer pathogenesis in AI/AN women. The primary study site will be at the Native American Community Action (NACA) clinic in Flagstaff, Arizona, that serves 50% AI/AN. Two Specific Aims are proposed:

Aim 1: Develop and implement a culturally sensitive vaginal sample collection protocol for AI/AN women. Training materials for vaginal sample collection will be developed on the basis of in-depth interviews with the NACA medical director and lead nurse practitioner. After training with these materials facilitated by the NACP Outreach Core, NACA clinic staff will analyze vaginal samples from 50 healthy (Pap negative) AI/AN women, 50 healthy (Pap negative) non-AI/AN women, 50 AI/AN women with low-grade cervical dysplasia (LGD), and 50 non-AI/AN women with LGD. A questionnaire will be administered to these participants enabling assessment of associations between the VMB and HPV types with sociodemographic factors, sexual history, knowledge of safe sex practices, and health behaviors.

Aim 2: Correlate the vaginal microbiome composition, host immune activity, HPV genotypes, and Lactobacillus abundances in AI/AN women and non-AI/AN women to better understand the relationship between these factors and cervical dysplasia. Shotgun metagenomics sequencing-based VMB profiles, inflammatory score, HPV genotype, and Lactobacillus abundance data will be generated from the vaginal swabs collected in Aim 1. Associations between these features and cervical epithelial status—normal or dysplastic—will be investigated with biostatistics assistance through the NACP Administrative Core.

Impact: This pilot project will be an important first step towards understanding the role of the VMB community structure in the development of HPV-related cervical dysplasia in an AI/AN disparate population that is at substantially increased risk for cervical cancer. This study will allow us to train new AI/AN students (Education Core) while enabling us to define the optimum protocol for culturally sensitive acquisition of vaginal samples in this underserved population. Although a relatively modest sample size could limit the statistical power of the current proposal, considerable confidence is justified that this pilot study will permit a clear estimate of the likelihood of obtaining definitive answers to questions about the role of the VMB in a future large-scale project of similar design. To that end, this pilot study will provide an invaluable assessment of the extent to which a larger study should be expanded to additional clinic sites.