Michelle H Townsend1, Claudia M Tellez Freitas2, Dallas Larsen3, Stephen R Piccolo4, K Scott Weber5, Richard A Robison5, Kim L O'Neill5. 1. Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, USA. Electronic address: mpassey8@gmail.com. 2. Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, USA; College of Dental Medicine, Roseman University of Health Science, South Jordan, UT, USA. 3. Department of Biology, Brigham Young University, Provo, UT, USA. 4. Department of Biology, Brigham Young University, Provo, UT, USA; Department of Biomedical Informatics, University of Utah, Salt Lake City, UT, USA. 5. Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, USA.
Abstract
INTRODUCTION: The purpose of this study was to examine the effects of elevated Hypoxanthine Guanine Phosphoribosyltransferase (HPRT) on the immune response in the tumor microenvironment. METHODOLOGY: HPRT expression was evaluated in cancer patients and correlated with cytokine expression, survival, and immune cell infiltration. An HPRT knockdown cell line was created to evaluate HPRT impact on purine expression and subsequent purine treatment was administered to immune cells to determine their influence on cell activation. RESULTS: HPRT expression was negatively correlated with the general expression of both pro-inflammatory and anti-inflammatory cytokines. Additionally, HPRT expression was also negatively correlated with the infiltration of immune cell subsets: B-cells, CD4 + T cells, macrophages, neutrophils, and dendritic cells (p < 0.001) and CD8 + T-cells (p < 0.01). When HPRT was knocked down in a Raji cell line, the levels of adenosine were reduced significantly compared to the wild type. When examining the level of Ca2+ influx of Raji compared to the HPRT Raji knockdown cell, there was a significant decrease in calcium influx in the knockdown cells when compared to the wild type cells. This demonstrates that HPRT had a significant impact on overall cell activation and the ability of the cells to properly influx calcium needed for their activation. CONCLUSIONS: We conclude that purine levels significantly reduce immune cell activation in cancer and the upregulation of HPRT in malignant tissue is a contributing factors to the immunosuppressive microenvironment.
INTRODUCTION: The purpose of this study was to examine the effects of elevated Hypoxanthine Guanine Phosphoribosyltransferase (HPRT) on the immune response in the tumor microenvironment. METHODOLOGY:HPRT expression was evaluated in cancerpatients and correlated with cytokine expression, survival, and immune cell infiltration. An HPRT knockdown cell line was created to evaluate HPRT impact on purine expression and subsequent purine treatment was administered to immune cells to determine their influence on cell activation. RESULTS:HPRT expression was negatively correlated with the general expression of both pro-inflammatory and anti-inflammatory cytokines. Additionally, HPRT expression was also negatively correlated with the infiltration of immune cell subsets: B-cells, CD4 + T cells, macrophages, neutrophils, and dendritic cells (p < 0.001) and CD8 + T-cells (p < 0.01). When HPRT was knocked down in a Raji cell line, the levels of adenosine were reduced significantly compared to the wild type. When examining the level of Ca2+ influx of Raji compared to the HPRT Raji knockdown cell, there was a significant decrease in calcium influx in the knockdown cells when compared to the wild type cells. This demonstrates that HPRT had a significant impact on overall cell activation and the ability of the cells to properly influx calcium needed for their activation. CONCLUSIONS: We conclude that purine levels significantly reduce immune cell activation in cancer and the upregulation of HPRT in malignant tissue is a contributing factors to the immunosuppressive microenvironment.