Abstract 354: BBI-608 modulates stemness, angiogenesis and enhances the efficacy of chemoradiotherapy in pre-clinical models of pancreatic cancer

Abstract

Abstract Background: The transcription factor signal transducer and activator of transcription 3 (STAT-3) is constitutively activated in pancreatic ductal adenocarcinoma (PDAC) and signaling via this pathway regulates a diverse set of cellular processes including stemness, angiogenesis and sensitization to chemo or radiotherapy. Given the potential for BBI608 to elicit effects on multiple oncogenic cellular pathways including STAT-3, we hypothesized that BBI608 can sensitize pancreatic cell lines to the effects of 5FU and ionizing radiation. Methods: The combined effects of BBI-608 and chemoradiotherapy (5-FU + IR) were evaluated in human (MIA PaCa-2, PANC-1) and murine (PANC-02) PDAC cell lines using a clonogenic assay. Effects on the expression of cell surface markers associated with stemness (EGFR, CD24, and CD44) in MIA PaCa-2 cell lines in vitroand in vivo were examined by flow cytometry. Modulation of pSTAT3 and VEGF, key pro-angiogenic factors, were studied via Western blot. Using media from MIA PaCa-2 and PANC-1 cell lines following treatment, egg CAM assays were also performed to evaluate the effects of the tested drugs on angiogenesis (quantification was performed by AngioQuant software). The MIA PaCa-2 cell line was tested for activity to BBI-608, 5-FU + IR, alone and in combination, using an in vivo tumor xenograft model. Results: The combination of BBI-608 and chemoradiotherapy significantly (p<0.001) decreased colony formation, stemness and angiogenesis in PDAC cell lines as compared to chemoradiotherapy alone. BBI-608 and chemoradiotherapy also decreased pSTAT-3 and VEGF expression. Flow cytometric analysis revealed that combined treatment of MIA PaCa-2 cell lines with BBI-608 and chemoradiotherapy significantly (p<0.001) reduced the expression of stemness markers (EGFR, CD44 and CD24) in vitro and in vivo. In animal models (MIA PaCa-2), BBI-608 potentiated the effects of chemoradiotherapy, as measured by tumor volume. There was no evidence of systemic toxicity or loss of body weight in any of the treatment groups, indicating the combination was well-tolerated. Matrigel plug implantation results revealed that BBI-608 and chemoradiotherapy significantly (p<0.0001) decreased blood vessel formation as compared to chemoradiotherapy alone, with similar results seen in the egg CAM assay. Conclusion: These observations provide preclinical proof-of-principle that combinatorial BBI-608 and chemoradiotherapy could be a promising therapeutic strategy for PDAC. Citation Format: Ganji Purnachandra Nagaraju, Matthew R. Farren, Sneha Govardhanagiri, Shipra Reddy Bethi, Batoul Farran, Gregory B. Lesinski, Bassel F. El-Rayes. BBI-608 modulates stemness, angiogenesis and enhances the efficacy of chemoradiotherapy in pre-clinical models of pancreatic cancer [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 354.