Medical Student Cleveland Clinic Lerner College of Medicine
Introduction: Intravesical installation of BCG has been the gold standard for the management of non-muscle invasive bladder cancer (NMIBC). However, approximately 30-40% of patients experience treatment failure and it remains unclear who will benefit from this therapy. One potential modifiable factor in treatment response may be the urinary microbiome. Therefore, we sought to investigate how the urinary microbiome may differ between BCG responders and non-responders and identify any commensal bacteria that might increase the efficacy of this therapy. Methods: 16S next-generation sequencing (NGS) and shotgun metagenomics were performed on formalin-fixed bladder tumors from patients prior to intravesical BCG therapy for NMIBC. BCG responders was defined as no recurrence two years after induction. Differences in the alpha and beta diversity of the two populations were compared. Subsequently, to validate the NGS data, GFP-tagged BCG was co-cultured with a urothelial carcinoma (UC) cell line (SW780) and candidate bacteria based on the NGS data. A Pearson-Chi Square test was utilized to compare percent internalization. Additionally, fresh tumor samples were collected at the time of transurethral resection of bladder tumor (TURBT) and were cultured in five different media conditions to confirm the viability of the tumor microbiome and quantify the bacterial mass per sample. Results: Forty-seven patients (23 responders, 24 non-responders) were included in the analysis. Overall microbiome composition differed significantly as determined by both NGS (p=0.042) and shotgun metagenomics (p=0.047). Lactobacillus spp were significantly enriched in the BCG responders. Co-culture with increasing concentrations of Lactobacillus crispatus resulted in increased BCG-GFP internalization in UCC (179/1133, 16%) when compared to controls (75/1166, 6%) (p < 0.001). Additionally, from ten fresh tumor samples, four samples produced viable bacteria through culture-based approaches and we calculated tumor bacterial density at 1.25 x 106 colony forming units/gram of tissue. Conclusions: A compositional difference exists in the tumor microbiome of BCG responders and non-responders. Lactobacillus crispatus was associated with a significant increase in the internalization of BCG. Our findings suggest that an association exists between the tumor microbiome and response to BCG, which may offer new strategies to improve intravesical therapy for NMIBC patients. SOURCE OF Funding: Case Comprehensive Cancer Center Summer Medical Student Award
