Abstract 4047: NF-kB inhibitor DMAPT enhances cisplatin efficacy and reduces its toxicity in a carcinogen-induced model of muscle-invasive bladder cancer

BACKGROUND: Nuclear factor kappaB (NF-κB) blocks apoptosis and promotes chemoresistance to drugs like cisplatin (CDDP). However, the clinical use of NF-κB inhibitors is restricted to hematological malignancies and the benefit of NF-κB inhibition in solid tumors has yet to be realized. The novel agent dimethylaminoparthenolide (DMAPT) blocks NF-κB in bladder cancer cell lines and can overcome chemoresistance as part of a combination therapy. METHODS AND RESULTS: We tested DMAPT9s ability to enhance CDDP9s efficacy against muscle-invasive bladder cancer. In vitro, 2.5 µM DMAPT was shown to up-regulate death receptor 4 and 5 expression and induce poly (ADP-ribose) polymerase (PARP) cleavage in UMUC-3 cells. Both 2.5 µM DMAPT and 2.5 µM CDDP reduced UMUC-3 cell viability as single agents, and their effect was enhanced when combined. We next tested CDDP (4.0 mg/kg/week i.p) and DMAPT (100.0 mg/kg/day oral) in combination and as single agents for 6 weeks in an immune-competent mouse model of muscle-invasive (T2) bladder cancer induced by the tobacco-related agent N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN). Procedures followed the 2010/63/EU animal welfare directive. One DMAPT-treated and 1 CDDP-treated mouse died during the experiments. The cohorts were: negative control (no BBN exposure, n=15), positive control (BBN but no therapy, n=19), BBN and DMAPT-treated (n=17), BBN and CDDP-treated (n=18) and BBN and the combination of CDDP plus DMAPT (n=19). Negative control, positive control, DMAPT, CDDP and combination-treated mice showed 0.0%, 42.1%, 35.3%, 11.1% and 0.0% bladder cancer incidence, respectively. T2 (muscle-invasive) lesions were present in positive controls (15.8%), DMAPT (17.6%) and CDDP (5.6%), but not in the combination group (0.0%). High-grade urothelial dysplasia, a pre-malignant lesion, was observed at rates of: 57.9% (positive controls), 29.4% (DMAPT), 16.6% (CDDP) and 0.0% (combination). CDDP induced renal tubular necrosis and interstitial nephritis seen on HE 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4047. doi:10.1158/1538-7445.AM2017-4047