Abstract 1856: Preclinical effects of dual AKT/MAPK inhibition in PTEN-deficient prostate cancer

Abstract

Abstract Targeting signal molecules with single agent monotherapy is met with limited or transient clinical benefits. Therefore, establishing effective rational combinatorial treatment strategies provides a better option for achieving improved clinical outcomes. The AKT/PI3K and MAPK signaling pathways have been identified as key compensatory signal transduction pathways in prostate cancer. We have used genetically engineered mouse models of prostate cancer to show the treatment efficacy of monotherapy with the AKT inhibitor AZD5363 and the MAP/ERK kinase (MEK) inhibitor selumetinib (AZD6244, ARRY142886). We hypothesized that a rational combinatorial approach utilizing both of these inhibitors would improve treatment efficacy compared to single agent monotherapy. To test this hypothesis, we evaluated the treatment effects of AZD5363 and selumetinib in preclinical models of prostate cancer. In vitro experiments were carried out using a panel of human prostate cancer cell lines, and mouse prostate cancer cell lines, derived from PTEN-deficient castration-naïve prostate cancer (CNPC) and castration-resistant prostate cancer (CRPC). Treatments with AZD5363 and selumetinib demonstrated a synergistic combination effect in both human and mouse prostate cancer cell lines. We evaluated the antitumor effects in vivo by comparing the effects of AZD5363 and selumetinib alone or in combination in PTEN-deficient mice. Our studies show that combination therapy of AZD5363/selumetinib was well-tolerated by the mice and demonstrated significantly improved inhibition of tumor growth compared to single agent therapy. In the CNPC model, mice showed 16.7, 10.0 and 24.9% reductions in tumor burden after treatments with AZD5363, selumetinib and AZD5363/selumetinib, respectively (P<0.001). In the CRPC model, mice showed 15.8, 3.8 and 27.0% reductions in tumor burden after treatments with AZD5363, selumetinib and AZD5363/selumetinib, respectively (P<0.001). Target validation studies confirmed the inhibition of downstream targets. Overall, our findings suggest a potential role for targeting the PI3K/AKT and MAPK signaling pathways with AZD5363 and selumetinib for treatment of PTEN-deficient prostate cancer. Citation Format: Marco A. De Velasco, Yutaka Yamamoto, Yurie Kura, Emiko Fukushima, Naomi Ando, Barry Davies, Yuji Hatanaka, Takashi Oki, Nobutaka Shimizu, Masahiro Nozawa, Kazuhiro Yoshikawa, Kazuhiro Yoshimura, Kazuto Nishio, Hirotsugu Uemura. Preclinical effects of dual AKT/MAPK inhibition in PTEN-deficient prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1856. doi:10.1158/1538-7445.AM2015-1856