Abstract 2937: The regulation of FGFR signaling by RTK adaptor protein down-regulation through CROX (cluster regulation of RUNX) theory in DNPC
Authors: Sasaski Asami , Yanagida Youhei , Sugiyama Hiroshi , Adachhi Souichi , Kamikubo Yasuhiko 
Published: September 2020

Up-regulation of the FGFR signaling is frequently-encountered in DNPC: AR-, NE- prostatic cancer and contributes to the maintenance of these cancer cells. Even though, the importance of active FGFR signaling was recognized as a biomarker in DNPC, still core oncogenic driver of DNPC remained unknown. We formerly reported the importance of Pan RUNX (RUNX1,2,3) as an oncogenic driver. Here, we added a new evaluation factors to the examination of CRPC patient cohort to categorize potentially existing DNPC clearly. Pan RUNX was up-regulated in DNPC patients. The inhibition of Pan RUNX reduced the proliferation of DNPC cells significantly, suggesting that Pan RUNX is functionally and critically involved in the cell proliferation mechanism of DNPC. The inhibition of Pan RUNX inhibited FGFR signaling dramatically. On the other hand, the inhibition of FGFR decreased the transactivation of Pan RUNX. To resolve this contradiction, we identified candidate genes which are mediating the crosstalk between FGFR signaling and Pan RUNX. In addition to our formerly reported S100A16, we isolated and examined the adaptor protein family responsible for RTK activation, which are transcriptionally regulated by the RUNX family. In addition, from the analysis by using the CRPC patient cohorts, Pan RUNX expression and SOS1 etc. genes levels were significantly higher in DNPC rather than those of the other subtypes. RUNX family regulates the FGFR signaling pathway in DNPC cells through transactivating expression, rendering itself an ideal target in anti-tumor strategy toward this cancer. Mechanistically, ChIP-qPCR assay and luciferase reporter experiments further validated RUNX family interacts with the RUNX binding DNA sequence located in the candidate genes promoter and positively regulates it. Knockdown of Pan RUNX led to the decreased expression of the adaptor genes as well as dephosphorylation of FGFR, subsequently suppressed the proliferation of DNPC cells. These data suggest that RUNX depletion-mediated growth inhibitory effect on DNPC cells depends on FGFR signal inactivation via transcriptional regulation of adaptor protein. To achieve cluster regulations of RUNX(CROX), We screened our library and isolated our original Pan RUNX inhibitor based on gene switch technology; Chlorambucil-conjugated Pyrrole Imidazole Polyamide (Chb-M'), which specifically binds to the common RUNX binding consensus sequence(TGTGGT) and inhibits RUNX target genes including the adaptor protein, consistently led to the deactivation of the FGFR signaling pathway and was effective against DNPC cell lines and was exceptionally well-tolerated in mice and exerted excellent efficacy against xenograft mice models of DNPC. Taken together, our work identified a novel interaction of RUNX family and the FGFR signaling pathway in DNPC, which can potentially be exploited in the management of this malignancy.

Citation Format: Asami Sasaski, Youhei Yanagida, Hiroshi Sugiyama, Souichi Adachhi, Yasuhiko Kamikubo. The regulation of FGFR signaling by RTK adaptor protein down-regulation through CROX (cluster regulation of RUNX) theory in DNPC [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2937.