Abstract 3339: Modulating TAK1 expression through the inhibition of GSK3 impairs YAP/TAZ oncogenic functions in pancreatic cancer

Abstract

Abstract Background: Resistance to chemotherapeutic drugs poses one of the greatest challenges in pancreatic cancer (PC) treatment. TGFβ-activated kinase 1 (TAK1) has been demonstrated to drive chemoresistance in PC through the phosphorylation-dependent activation of the NF-κB transcription factor. The transcriptional regulators Yes Associated Protein (YAP) and transcriptional coactivator with a PDZ binding domain (TAZ) are central determinants of malignancy and have been identified as a critical oncogenic effectors of KRAS in PC. We hypothesized that TAK1 could drive PC aggressiveness by sustaining YAP and TAZ oncogenic activities. Methods: TAK1 expression was silenced by shRNA in AsPC1, Panc1, and MDA-Panc28 cell lines. GSK3 was targeted by using the small molecule inhibitor LY2090314. The expression of TAK1, YAP/TAZ and their target genes in PC cell lines was studied by both Western blot and qPCR. Cell migration was assessed by transwell assays, and stemness by both spheroid formation and percentage of cancer stem cells (CSC). SRB assays were used to assess the in vitro chemopotentiation of nab-paclitaxel, gemcitabine, oxaliplatin, and SN-38. In vivo activity of LY2090314 alone or in combination with nab-paclitaxel was evaluated in an orthotopic nude mouse model with luciferase-expressing AsPC1 tumors. Expression of YAP/TAZ target genes in tumor samples was measured by both qPCR and IHC. Results: knockdown of TAK1 resulted in inhibition of K48-linked ubiquitination and proteasomal degradation of YAP and TAZ, which was independent on TAK1 kinase activity. Significant reduction of proliferation, migration and chemoresistance of shTAK1 PC cell lines was also observed. Treatment with LY2090314 induced silencing of TAK1, as well as a remarkable reduction of the expression of both YAP and TAZ and their targets. In combination, the GSK3 inhibitor strongly potentiated the cytotoxic activities of chemotherapeutic agents in all three PC cell lines. In nude mice, i.p. admnistration of LY2090314 plus nab-paclitaxel significantly reduced tumor burden. Conclusions: Our study identified GSK3 and TAK1 as major modulators of YAP and TAZ stability and oncogenic activities, thus indicating that inhibition of TAK1 expression by modulating GSK3 activity could represent a valid approach to revert in vivo the intrinsic chemoresistance of PC. Citation Format: Raffaela Santoro, Marco Zanotto, Geny Piro, Carmine Carbone, Giampaolo Tortora, Davide Melisi. Modulating TAK1 expression through the inhibition of GSK3 impairs YAP/TAZ oncogenic functions in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3339.