Abstract B06: Characterizing the effects of hypoxia and hydrostatic pressure on the expression of immunotherapeutic targets in prostate cancer cell lines and donor immune cells in culture

Abstract

Abstract Introduction: Cancer immunotherapy has changed the paradigm of cancer treatment by harnessing the immune system to identify and eradicate tumors leading to significant improvements in the objective response and long term survival of patients. However, more than 50% of patients do not respond to the most advanced immunotherapeutics in clinical trials, suggesting that further research is needed to understand the mechanism of action and resistance to immune-modulating agents in patients. The current hypothesis is that the tumor microenvironment can modulate the reprogramming of stromal cells caused by chronic inflammation, leading to a suppressed immune system that is highlighted by T-cell exhaustion and anergy. Hypoxia and high interstitial fluid pressure within tumors are elements that may contribute to gene and protein expression changes in stromal, immune and tumor cells in the microenvironment to inhibit immune function and promote cancer proliferation and metastasis. Methods: We have developed a novel primary cell culture bioreactor to modulate both oxygen level (0.1% to 19%) and hydrostatic pressure levels (26 to 260 mmHg / 0.5 psig to 5 psig) to study the effects on gene and protein expression profiles of prostate cancer cell lines and peripheral blood mononuclear cells (PBMCs) derived from donors. We performed high-resolution immunofluorescence imaging and western blot protein expression analysis of primary immuno-therapy targets CTLA-4, PD-1, and PD-L1. In addition, whole transcriptome sequencing was performed on cells across a range of physiologically-relevant culturing conditions to mimic various tumor microenvironments found within the body. Conclusions: We report that prostate cancer cell lines and PBMCs differentially express immunotherapeutic targets when cultured at physiologically relevant tumor microenvironment conditions, resulting in reduced expression of key targets. Analysis of mRNA-seq data revealed alterations in gene expression profiles of immunotherapeutic and drug-target pathways involving CTLA-4 and AR signaling. In contrast, we observed increased CD47 and CD44 expression at low oxygen and high pressure culturing conditions in cancer cell lines and PBMCs. These data highlight the importance of using physiologically relevant microenvironment conditions that include hypoxia and pressure to identify biomarkers and drug target candidates. Citation Format: Bruce A. Adams, James Lim, Tianna Chow, Susan Bernstein, Charles J. Ryan. Characterizing the effects of hypoxia and hydrostatic pressure on the expression of immunotherapeutic targets in prostate cancer cell lines and donor immune cells in culture. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr B06.