Flavoperidol as a novel therapeutic agent for bladder cancer.

Abstract

357 Background: Bladder cancer (CaB) is the 4th most common cancer among men in the US but receives substantially less research resources than many other cancer types. There has been little change to the management of bladder cancer over the past 25 years. Quantitative high throughput screening (qHTS) of representative cancer lines with oncology drugs may identify new treatments or re-purpose already existing therapies for different disease. We utilized this technique to identify new therapies in three primary bladder lines (RT4, T24, and UMUC3) and their metastatic lines (T24T, SLT3 and FL3 for T24 and LUL-2 for UMUC3). Methods: We screened 8 bladder cancer cell lines (including RT4, T24, and UMUC3) against 1,912 oncology drugs using a 48 hour cell proliferation assay with an ATP−based readout to determine activity and potency of compounds in a dose response manner. One of the candidate drugs inhibitory in all cell lines tested is flavopiridol, a pan CDK inhibitor. We further characterized the mechanism of action and in vivo effects of flavopiridol using various cell based assays and mouse xenograft studies. Results: The initial screen identified 95 compounds active in 8 cell lines. The top 50 compounds were further analyzed for molecular size of >200 g/mol and TPSA<90. This identified mitomycin C and 8 novel compounds. Further testing revealed Flavopiridol to be most consistent with qHTS data having IC50 of 100-300nM in all the cell lines tested. Flavopiridol induces G2/M arrest; however, very little apoptosis was seen suggesting a cytostatic rather than a cytotoxic mechanism of flavopiridol action. Flavopiridol showed dose dependent inhibition of migration, invasion and colony formation in all cell lines tested. Xenograft studies in rapidly growing UMUC-3 cells showed slowing of tumor growth but not complete reduction indicating cytostatic mechanism of flavopiridol. Conclusions: A high throughput drug screen can identify novel compounds in bladder cancer. Flavopiridol seems to be a very effective inhibitor both in vitro and in vivo. Physical properties of Flavopiridol are most suited for intravesical use, which may lead to it being an effective inhibitor of CaB in the bladder at higher doses without any/few systemic toxicities.