Abstract 3818: BGJ398, a pan-FGFR inhibitor, overcomes paclitaxel resistance in urothelial carcinoma with FGFR1 overexpression

Abstract

Abstract Introduction: Paclitaxel (PTX) is commonly used to treat urothelial carcinoma (UC) after platinum-based chemotherapy has failed. However, single-agent taxane therapy is not sufficient to inhibit tumor progression and drug resistance in advanced UC. Epithelial-to-mesenchymal transition (EMT) induced by fibroblast growth factor receptor (FGFR)1 signaling has been proposed as a mechanism of PTX resistance, but it is unclear whether this can be overcome by FGFR1 inhibition. The present study investigated whether FGFR1 overexpression contributes to PTX resistance and whether FGFR inhibition can enhance PTX efficacy in UC. Materials and Methods: UC cell lines: UMUC-14, RT4, T24, J82, HTB5 and HTB9 cells were used. Cells were treated with various concentration of PTX (0 to 20 nM) and BGJ398 (0 to 6 μM). The half-maximal inhibitory concentrations (IC50) were measured by the CellTiter-Glo assay. Cell cycle was analyzed after propidium iodide (PI) staining via flow cytometry. Changes in cell cycle, apoptosis and EMT-associated protein levels were assessed by Western Blot analysis. The migratory and colony formative property were analyzed by wound healing assay and colony forming assay, respectively. RNA interference was performed to assess the dependence of PTX sensitivity on pro-apoptotic proteins. Results: We showed that mesenchymal-type T24 and J82 cell lines were highly resistant to PTX (0 to 20 nM) or BGJ398 (0 to 6 μM) monotherapy compared to FGFR3-positive epithelial-type (i.e., RT4 and UMUC-14) UC cell lines. We further found that PTX (10 nM) combined with BGJ398 (6 μM) caused synergistic effects on sub G1 accumulation and apoptosis compared to PTX or BGJ398 monotherapy in T24 and J82 cells, which were accompanied by downregulation of cyclin D1 protein and upregulation of gamma-histone 2A family member X, cleaved caspase-9 and cleaved poly (ADP-ribose) polymerase (PARP). Additionally, 10 nM of PTX combined with 6 μM of BGJ398 synergistically suppressed mesenchymal-type UC cell migration and colony formation via downregulation of EMT-associated factors including snail, slug and ZEB1. FGFR1 knockdown enhanced the antitumor effect of PTX (10 nM) by upregulation of apoptosis-associated markers, cleaved caspase-9 and PARP. Conclusions: We investigated the mechanism of resistance to PTX in UC mediated by FGFR1 and found that combined treatment with BGJ398 can enhance the efficacy of PTX in UC cell lines with mesenchymal features. Our results demonstrate that combination with FGFR1-targeted therapy improves the antitumor efficacy of standard cytotoxic chemotherapy, which is a strategy that warrants further investigation in clinical trials in selected UC patients with FGFR1 overexpression. Citation Format: Haram Ryu, Se Hyun Kim, Chan-Young Ock, Koung Jin Suh, Ji Yun Lee, Ji-Won Kim, Jin Won Kim, Jeong-Ok Lee, Yu Jung Kim, Keun-Wook Lee, Soo-Mee Bang, Jee Hyun Kim, Jong Seok Lee, Joong Bae Ahn, Kui-Jin Kim, Sun Young Rha. BGJ398, a pan-FGFR inhibitor, overcomes paclitaxel resistance in urothelial carcinoma with FGFR1 overexpression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3818.