Shiva Kazerounian

Abstract 5576: BPM 31510, a clinical stage candidate demonstrates potent anti-tumor effect in an immune-competent syngeneic pancreatic cancer model

BPM 31510, a clinical stage nanodispersion of ubidecarenone, demonstrates anti-tumor effects by eliciting an anti-Warburg metabolic switch in cancer. Previous studies in an immune compromised PaCa2 xenograft model has unequivocally demonstrated significant efficacy of BPM 31510 on tumor volume and survival. The fundamental property of BPM 31510 to influence mitochondrial bioenergetics and the recognized interplay between T cell metabolism and maturation prompted investigation into the effects of BPM 31510 on T lymphocyte functions in eliciting anti-cancer effects. In this study BPM 31510 selectively influenced activation and maturation of T cells in murine peripheral blood mononuclear cells (PBMCs). Moreover, in addition to determining changes in the CD3+ population, changes in surface expression of PD-1 and CTLA4 along with the IFN-γ secretion were examined. Murine cancer cell lines exposed to BPM 31510 were associated with variable sensitivity with highly metabolic tumor types being most sensitive. Next, the anti-cancer activity of BPM 31510 in an in vivo immunocompetent syngeneic Pan02 rodent model was investigated. Murine Pan02 pancreatic cancer cells were implanted subcutaneously into C57BL/6 mice. Tumors with mean volume of 80 mm3 were treated twice a day with vehicle control or BPM 31510 at 25, 50, 100 mg/kg, administered intraperitoneal. Tumor volumes were measured every 4 days. At day 21 post treatment, tumors were harvested and analyzed for the level of infiltrating immune cells by immunofluorescent staining with CD8+ for T cells and F4/80 for tumor macrophages. These results demonstrate a dose-dependent reduction in tumor volume following 21 days of BPM 31510 treatment. In summary, BPM 31510 exerts potent anti-tumor effects through its dual function of modulating tumor cell metabolism and potentially influencing immune check-point to improve overall survival outcomes. Citation Format: Shiva Kazerounian, Aishwarya Sarma, Nidhi Gaur, Maria D. Nastke, Tulin Dadali, Anne R. Diers, Stephane Gesta, Vivek K. Vishnudas, Rangaprasad Sarangarajan, Niven R. Narain. BPM 31510, a clinical stage candidate demonstrates potent anti-tumor effect in an immune-competent syngeneic pancreatic cancer model [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 5576. doi:10.1158/1538-7445.AM2017-5576

PI-25Interruption of homologous desensitization in cGMP signaling restores colon cancer cytostasis by bacterial enterotoxins

Bacterial diarrheagenic heat‐stable enterotoxins (STs) induce colon cancer cell cytostasis by targeting guanylyl cyclase C (GCC) signaling. Although the molecular pathway involving cGMP‐dependent influx of Ca2+ through cyclic nucleotide‐gated (CNG) channels has been elucidated, the long‐term kinetics of the antineoplastic effects of these toxins remain undefined.

Mitogenic CA2+ entry through ICRAC channels reciprocally regulates the tumor suppressor guanylyl cyclase C (GCC)

Guanylyl cyclase C (GCC) through cyclic GMP (cGMP) inhibits colorectal cancer cell proliferation, serving as a tumor suppressor in intestine. Conversely, Ca2+ entry through calcium release‐activated calcium (Icrac) channels promotes colorectal cancer growth. The present study explored the functional relationship between mitogenic signaling by Ca2+ entry through Icrac channels and antiproliferative signaling by GCC in T84 human colon carcinoma cells. The E. coli heat‐stable enterotoxin ST, a specific GCC ligand, induced intracellular accumulation of cGMP, Ca2+ entry through CNG channels and inhibition of human colorectal cancer cell proliferation. In contrast, influx of extracellular Ca2+ through Icrac channels, induced by thapsigargin, UTP or carbachol, inhibited GCC‐dependent cGMP accumulation. Chelating intracellular Ca2+, removing extracellular Ca2+, or specifically blocking Icrac channels with the antagonist 2‐APB reversed this inhibition. Moreover, 2‐APB blocked Ca2+‐dependent cell proliferation and amplified the anti‐proliferative effects of ST. These data suggest that an imbalance of pro‐ and anti‐mitogenic signals mediated by Ca2+ may contribute to mechanisms underlying colorectal carcinogenesis. In addition, they suggest that the combination of GCC agonists and Icrac channel inhibitors represents a novel paradigm for cGMP‐directed therapy for colorectal tumors.

Soluble guanylyl cyclase is an ATP sensor coupling nitric oxide signaling to cell metabolism

Defending cellular integrity against disturbances in intracellular concentrations of ATP ([ATP]i) is predicated upon coordinating the selection of substrates and their flux through metabolic pathways (metabolic signaling), ATP transfer from sites of production to utilization (energetic signaling), and the regulation of processes consuming energy (cell signaling). Nitric oxide (NO) and its receptor soluble guanylyl cyclase (sGC) are key mediators of cellular energetics and can regulate ATP supply and demand. However, mechanisms coordinating NO/sGC and energetic signaling remain undefined. Here, we demonstrate that sGC is a nucleotide sensor whose responsiveness to NO is regulated by intracellular ATP ([ATP]i). ATP inhibits purified sGC with a Ki predicting >60% inhibition of NO signaling in cells maintaining physiological [ATP]i. ATP inhibits sGC by interacting with an allosteric site that prefers ATP>GTP. Moreover, in RFL‐6 cells, alterations in [ATP]i are coupled to NO/sGC signaling. Indeed, oligomycin, an inhibitor of mitochondrial ATP synthase, reduced [ATP]i 48%, from 1.25 nmol to 0.65 nmol of ATP/mg protein, but increased [cGMP]i 45%, from 42 to 61 pmol/mg protein. Thus, [ATP]i serves as a “gain control” for NO signaling by sGC. At physiological [ATP]i, NO signaling by sGC is repressed, while insults that reduce [ATP]i, such as ischemia, de‐repress sGC and amplify responses to NO.