Identification of molecular biomarkers of cisplatin-based chemosensitivity in patients undergoing neoadjuvant chemotherapy for muscle-invasive bladder cancer

374 Background: Although survival benefit of cisplatin-based neoadjuvant chemotherapy for muscle-invasive bladder cancer (MIBC) has been demonstrated, a significant proportion of patients do not respond. Identification of chemoresponsive cohorts would avoid morbidity and delayed surgical intervention in patients unlikely to derive benefit. We evaluate the role of miRNA and mRNA expression profiles in initial TURBT specimens of patients who receive neoadjuvant chemotherapy prior to undergoing radical cystectomy. Differences in expression patterns between complete responders (pT0) and nonresponders (pT2 ≤ ) at time of cystectomy may help stratify patients being considered for neoadjuvant chemotherapy. Methods: FFPE tissue was isolated from initial TURBT specimens of patients with clinically localized MIBC treated with cisplatin-based neoadjuvant chemotherapy. Tissue from 9 patients with T2 ≤ disease was compared with specimen from 10 pT0 patients at time of cystectomy specimen. Differential expression of 754 miRNAs and mRNA was analyzed utilizing real time quantitative polymerase chain reaction. miRNA expression profiles were compared between complete responder and nonresponder groups. mRNA in tumor specimen was sequenced from both groups with 76 base pair paired-end reads using NextSeq technology. KEGG Pathway analyses helped identify differential gene expression between complete responders and nonresponders. Results: Significant upregulation of miRNA 1203, miRNA 1304, and miRNA 580 was observed nonresponders versus complete responders. KEGG pathway analysis revealed significant upregulation of the hsa03430 pathway, implicated in DNA mismatch repair, the hsa03420 pathway, implicated in nucleotide excision repair, and the hsa03410 pathway, involved in base excision repair, among pT0 patients. Conclusions: Differential miRNA and mRNA expression within the initial tumor specimen of patients with complete pathologic regression versus progression indicates a possible role in determining-neoadjuvant chemo-sensitivity.