Abstract 4074: Heat shock protein 90 inhibitors alter pancreatic stellate cell cytokine production and enhances the efficacy of immune checkpoint blockade in pancreatic cancer
Authors: Zaidi Mohammad , Zhang Yuchen , Ware Michael B. , Farren Matthew R. , Komar Hannah , Olson Brian , Nagaraju Ganji P. , Akce Mehmet , Alese Olatunji , Maithel Shishir , Sarmiento Juan , Shaib Walid , Wu Christina , El-Rayes Bassel , Lesinski Gregory B. 
Published: August 2019

Abstract
Pancreatic ductal adenocarcinoma (PDAC) has a prominent fibrotic stroma, which is a result of interactions between tumor, immune and pancreatic stellate cells (PSC). Prior work from our laboratory has defined a role for stroma-derived cytokines such as IL-6 as a significant barrier restraining immunity against PDAC. Our group is pursuing novel approaches to target pathways in the tumor microenvironment (TME), in an effort to improve access of effector immune cells to PDAC and response to immunotherapy. Heat shock protein-90 (Hsp90), is a chaperone protein and a versatile target in pancreatic cancer. Hsp90 regulates a diverse array of cellular processes of relevance to both the tumor and the immune system. However, to date the role of Hsp90 in PSC has not been explored in detail. We hypothesize that targeting Hsp90 can modulate the TME, through its ability to target inflammatory signaling and cytokine production by PSC and enhance the efficacy of immunotherapy. Treatment of immortalized and primary patient PSC with the Hsp90 inhibitor XL888 led to decreased IL-6 at the transcript and protein level in vitro. XL888 directly limited PSC growth, and reduced expression of alpha-SMA, Jak/STAT and MAPK signaling intermediates as determined via immunoblot. Combined therapy with XL888 and anti-PD-1 was efficacious in C57BL/6 mice bearing syngeneic subcutaneous (Panc02) or orthotopic (KPC-Luc) tumors, as compared to treatment with either agent alone. The treatment was well-tolerated, with no difference in body weight observed in either model. Laboratory studies are assessing immune and stromal biomarkers to define the impact on PSC, cytokines and T-cell biomarkers in the TME. Finally, we have completed the dose escalation phase of a Phase Ib/II clinical trial of XL888 (Hsp90i) and pembrolizumab (anti-PD-1) at our institution. Expansion cohorts of patients with metastatic pancreatic cancer (n=16) or colorectal cancer (n=16) are now accruing, with paired biopsy and peripheral blood samples to address the impact of Hsp90 inhibition on anti-PD-1 mediated T cell proliferation, cytokine production, and PSC-derived cytokine signatures.
Citation Format: Mohammad Zaidi, Yuchen Zhang, Michael B. Ware, Matthew R. Farren, Hannah Komar, Brian Olson, Ganji P. Nagaraju, Mehmet Akce, Olatunji Alese, Shishir Maithel, Juan Sarmiento, Walid Shaib, Christina Wu, Bassel El-Rayes, Gregory B. Lesinski. Heat shock protein 90 inhibitors alter pancreatic stellate cell cytokine production and enhances the efficacy of immune checkpoint blockade in 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 4074.