Abstract 6162: Histone deacetylase inhibitor modulates T cell recruitment to metastatic pancreatic neuroendocrine tumors by CCR5 regulation

Abstract Pancreatic neuroendocrine tumors (PNETS) represent the second most common pancreatic neoplasm with surgical resection serving as the mainstay of treatment for localized PNETs (lPNETs) > 2 cm in size; however, therapeutic options for managing metastatic PNETs (mPNETs) remain limited. Recently, immunotherapy with checkpoint inhibitors has emerged as effective therapy across a range of malignancies but has shown limited efficacy in PNET patients partly due to what has been reported as a “cold” tumor microenvironment (TME). Here, we aimed to characterize the TME among both localized and mPNETs and identify mechanisms to increase tumor immunogenicity and T cell recruitment among these patients. We analyzed tumor-infiltrating and peripheral T cells from patients with lPNETs and mPNETs by flow cytometry and found higher expression of CD69+ (activation), CCR5+ (recruitment), and PD1+ (exhaustion) in T cells isolated from TME compared to peripheral blood. Further, we identified a more profound degree of CD3+ and CD8+ T cell infiltration among mPNETs compared to lPNETs by immunohistochemistry analysis, suggesting that mPNETs are at least moderately enriched with activated T cells. RNA-sequencing performed on 22 sporadic, well-differentiated primary PNETs revealed distinct transcriptional signatures dependent upon metastatic potential. These divergent transcriptomes were analyzed by an L1000 computational algorithm, which classifies landmark gene signatures perturbed by drug treatments. We identified the histone deacetylase inhibitor vorinostat as the drug most likely to perturb the PNET gene signature. A KEGG pathway analysis revealed that these vorinostat-target genes were commonly involved in both Th1, Th2, and Th17 cell differentiation and in the NF-κB pathway. Vorinostat treatment of patient-derived mPNET resulted in increased T cell migration towards metastatic tumors across a semi-permeable membrane; cotreatment with a competitive CCR5 antagonist abrogated this effect. In addition, vorinostat treatment of BON-1 and QGP-1, two PNET cell lines, elevated both NF-κB activity and CCR5 expression, with induction reduced following inhibition of NF-κB nuclear localization. Our study demonstrates that T cell recruitment toward mPNET tissue is dependent upon CCR5 expression. These results reveal that PNET TME is regulatable by vorinostat and opens an avenue of potential sensitization to immune checkpoint blockade among patients with PNETs. Citation Format: Jacques A. Greenberg, Jessica N. Limberg, Akanksha Verma, David Kim, Maureen D. Moore, Timothy M. Ullmann, Jessica W. Thiesmeyer, Zachary Loewenstein, Kevin J. Chen, Caitlin E. Egan, Dessislava I. Stefanova, Rohan Bareja, Rasa Zarnegar, Brendan M. Finnerty, Theresa Scognamiglio, Olivier Elemento, Thomas J. Fahey, Irene M. Min. Histone deacetylase inhibitor modulates T cell recruitment to metastatic pancreatic neuroendocrine tumors by CCR5 regulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6162.