Abstract 5082: The selective bromodomain inhibitor, INCB054329 targets both cancer cells and the tumor microenvironment in the KC inflammatory preclinical model of ductal pancreatic cancer

Pancreatic cancer is expected to become the second most deadly cancer by 2030, with few effective therapeutic options available to improve patient survival. The Kras gene is mutated in over 90% of pancreatic cancers, but the Kras protein is considered to be an undruggable target. p-Erk is a downstream effector of Kras and has been shown to be essential for the progression and maintenance of pancreatic cancer. The LSL-KrasG12D/+; Pdx-1-Cre (KC) mouse model is used to study pancreatic cancer, especially cancer progression, after stimulation with an inflammatory agent, such as caerulein or LPS. Bromodomain inhibitors are a new generation of drugs that target BET (bromodomain and extra-terminal) proteins, impairing their ability to bind to acetylated lysines and therefore interfering with transcriptional initiation and elongation. BET proteins regulate several genes responsible for cell growth, apoptosis and inflammation. INCB54329 is a novel, orally bioavailable BET inhibitor that is currently being investigated in Phase 1 clinical trials.INCB054329 inhibits cell growth in murine pancreatic cancer cells harboring Kras mutations, derived from a KrasG12D/+; Trp53R172H/+; Pdx-1-Cre (KPC) mouse with an IC50 values less than 100 nM. Moreover, INCB054329 reduces the levels of p-ERK 1/2 in these cells lines. When KC mice are injected with LPS to induce inflammation and pancreatitis, p-Stat3 protein levels are significantly increased, but this pro-survival protein is reduced by more than 50%, in mice that were pre-treated with INCB054329. Tumor cells can use epigenetic modulation to evade immune recognition and to shape the TME (tumor microenvironment) toward an immunosuppressive phenotype. Since epigenetic modulation is a mechanism used by tumors to regulate the TME, using small molecules as epigenetic modulators to activate immune recognition is a therapeutically desirable approach. Within the TME, several cytokines and chemokines play crucial roles, recruiting and regulating inflammatory cells [macrophages, T cells and Myeloid derived suppressor cells]. KC mice stimulated with LPS have higher levels of CCL2 (1947 ± 591 ng/mL) and IL-6 (2459 ± 577 pg/mL) than unstimulated mice; these increased levels of inflammatory cytokines and the subsequent immune cell infiltration can be modulated by treatment with INCB054329, with INCB054329 demonstrating >50% inhibition of both cytokines (IL-6: 1063 ± 502 pg/mL; CCL2: 713 ± 134 ng/mL). These data suggest that INCB054329 has a dual activity, targeting cancer cells and modulating the TME; both activities may prove beneficial for the treatment of pancreatic cancer. Moreover, this work suggests that additional mechanisms may underlie the beneficial effects of bromodomain inhibitors. Citation Format: Ana Sofia Leal, Karen T. Liby, Phillip Liu, Bruce Ruggeri. The selective bromodomain inhibitor, INCB054329 targets both cancer cells and the tumor microenvironment in the KC inflammatory preclinical model of ductal pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5082. doi:10.1158/1538-7445.AM2017-5082