PI3KCA mutations in advanced urothelial carcinoma: A potential therapeutic target?

Abstract

4582 Background: PI3KCA is frequently mutated in human cancer; however, information is scarce regarding its relevance in urothelial carcinoma (UC). We determined the prevalence of mutation and impact on clinical outcome of PI3KCA uniformly-treated patients with metastatic UC. Impact of PI3K and dual PI3K/mTOR inhibition was tested in vitro in UC cell lines with either H1047R or E545K mutation. Methods: 141 samples from invasive UC were scanned for mutations. Of those, complete clinical data was available from 85 cases treated with platinum-based combination chemotherapy for advanced or metastatic disease. DNA was extracted from FFPE material. Mutation status was determined by iPLEX sequencing and confirmed with hME sequencing. Overall survival (OS) was measured from beginning of treatment for metastatic disease to time of death or censored on the last known alive date. Cox proportional hazard model was used to assess the associations of PI3K mutational status and OS. Growth inhibitory effects of a specific PI3K inhibitor and a dual PI3K/mTOR inhibitor (both from Selleck) on UC cell lines with or without mutations were tested using MTT assays. Results: Mutations in the PI3KCA gene were observed in 14 (10%; 95% CI 6-16%) specimens. E545K was detected in all 14 specimens, though one specimen contained mutation at both E545K and H1047R. Among patients with clinical data, there was no statistically significant association between PI3KCA mutational status and OS (HR for having PI3KCA=0.49, 95% CI [0.15, 1.57], p-value 0.22). Preliminary in vitro experiments showed that cell growth was more potently inhibited with dual PI3K/mTOR inhibitors than with PI3K inhibitors. Conclusions: Mutations in the PI3KCA gene were detected in 10% of invasive UC and did not correlate with OS in patients with metastatic UC treated with platinum-based chemotherapy. PI3K inhibition in vitro impacts UC cell growth, though dual PI3K/mTOR inhibitors may have more significant effects than PI3K inhibition alone.