Abstract 3918: Synergistic targeting of fibroblast growth factor receptor and AKT pathways significantly inhibits prostate cancer progression

The fibroblast growth factor (FGF) and AKT pathways are important stimuli to prostate cancer (PCa) development and progression. FGF and AKT pathways are becoming increasingly attractive as targets for PCa therapeutic intervention. Dual-targeting of FGF receptor (FGFR) and AKT signaling might be highly efficacious in the treatment of PCa. In this study, we evaluated the combined treatment effect of FGFR inhibitor AZD4547 and AKT inhibitor AZD5363 on PCa progression in vitro. Proliferation assay shows that AZD4547 weakly inhibits PCa cell proliferation, while AZD5363 demonstrates strong proliferation inhibition effect. The combined treatment of AZD4547 and AZD5363 further inhibits cell proliferation compared to AZD4547 monotreatment. Both AZD4547 and AZD5363 inhibit cell anchorage-independent growth and invasion, and combined treatment synergistically decrease cell soft agar colony formation ability and invasiveness. Molecular mechanisms of the dual targeting of FGFR and AKT were explored by immunoprecipitation (IP) and western blot (WB). IP on 22RV1 cells shows that FGFR4 phosporylation was inhibited by AZD4547 but not AZD5363, while was strongly decreased in the combined treatment. WB demonstrats that in VCaP and LNCaP cells PLCγ phosphorylation was significantly inhibited by AZD4547, slightly decreases by AZD5363, and strongly inhibited by combined treatment. FGFR2α phosphorylation was remarkably inhibited by AZD4547 in VCaP and 22RV1 cells, slightly decreased by AZD5363 in VCaP cells, but was strongly increased by AZD5363 in 22RV1 cells. Combined treatment of both cell lines shows remarkable inhibition of FRS2α phosphorylation. Erk1/2 and MEK phosphorylation was dramatically decreases by AZD4547, while was not inhibited, or to some extent, increased by AZD5363. Notably, the combined treatment synergistically inhibited MAPK signaling in PCa cells. AKT phosphorylation was dramatically enhanced by AZD5363 as an inactive hyperphosphorylated form. It was inhibited by AZD4547, but was still highly enhanced in combined treatment because that the stimulation effect of AZD5363 was too strong to be attenuated. Both AZD4547 and AZD5363 suppress STAT3 phosphorylation in LNCaP and 22RV1 cells, and the combined treatment shows synergistic inhibition of STAT3 activation. STAT1 phosphorylation was inhibited by AZD5363 and combined treatment but not by AZD4547 alone. WB also demonstrate that AZD5363 strongly inhibit phosphorylation of AKT substrate and downstream proteins PRAS40, GSK3β and S6, which are not, or slightly decreased by AZD4547, but are remarkably inhibited by the combined treatment. This study provides a preclinical proof of concept that combination of a FGFR inhibitor with an AKT inhibitor has profound potential to treat prostate cancer. Citation Format: Shu Feng, Michael Ittmann. Synergistic targeting of fibroblast growth factor receptor and AKT pathways significantly inhibits prostate cancer progression. [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 3918. doi:10.1158/1538-7445.AM2015-3918