Association of Bacterial Composition and Diversity in the Cervical Tumor Microbiome with HPV Genotype in a Large, International Patient Cohort

PURPOSE/OBJECTIVE(S)

Tumor bacterial composition is strongly associated with response to cancer therapy, and is impacted by environment, including geography. Human papillomavirus (HPV) genotypic diversity composition and load are dynamic during pelvic radiation (RT) and correlate with differential responses to RT in cervical cancer patients. In this multi-institutional, collaborative study, we aimed to explore associations between bacterial composition, HPV serotypes, and geographical distribution in an international patient population.

MATERIALS/METHODS

Cervical swabs were collected from 287 patients diagnosed with cervical cancer/ dysplasia in four locations: Houston, USA (TX; N = 94), Ethiopia (ETH; N = 85), Puerto Rico (PR; N = 71), and Botswana (BOT; N = 37). Swabs were collected prior to treatment and were subjected to 16S V4 rRNA gene sequencing and HPV genotyping. We compared HPV types and geography via Chi-squared test. We analyzed bacterial composition, alpha diversity (ANOVA), and beta diversity (principal coordinates analysis [PCoA] with PERMANOVA) for HPV type and geography. We used Linear Discriminant Effect Size (LEfSe) analysis to distinguish taxa associated with HPV types.

RESULTS

Overall, the global bacterial composition for patients with cancer or dysplasia did not significantly vary by location. However, the proportion of patients with each HPV type varied by location (p<0.01); HPV16 was most frequent in TX (54%), BOT (70%) and ETH (61%), while HPV18 was most frequent in PR (62%). The proportion of patients with HPV low-risk/negative tumors was highest in ETH (25%) compared to other sites (2% - 14%). Patients with HPV 16 had significantly higher bacterial alpha diversity across locations (all p<0.01). The bacterial composition also differed by HPV type across locations (p = 0.01). On LEfSe, bacterial genera enriched in HPV 16 samples were Bacteroides, Clostridium, and Prevotella. Non-HPV16 tumors were enriched in species of Lactobacillus and Gardnerella and HPV 18 and high-risk type tumors were enriched in Escherichia.

CONCLUSION

In thislarge, international cohort of cervical cancer and dysplasia patients, bacterial composition was more closely associated with cervical HPV genotype than with geography. This finding has implications for the development of biomarkers and interventions aimed at improving chemotherapy and radiation response through manipulation of the microbiome.