Effects of oxygen on the antigenic landscape of prostate cancer cells

Tangeng Ma,Mohamed Hassan,Marcelo J Sakiyama,Mary Christine Charlesworth,Xinchun Zhou,Benjamin J Madden,Gaylord J Knutson,Christian R Gomez,Stanimir Vuk-Pavlović,Abdelouahid El Khattouti,Claire A Schreiber

doi:10.1186/s13104-015-1633-7

Abstract

BackgroundUse of allogeneic cancer cells-based immunotherapy for treatment of established prostate cancer (PCa) has only been marginally effective. One reason for failure could stem from the mismatch of antigenic signatures of vaccine cells and cancer in situ. Hence, it is possible that vaccine cells expressed antigens differently than tumor cells in situ. We hypothesized that cells grown in vitro at low oxygen tension (pO2) provide a better antigen match to tumors in situ and could reveal a more relevant antigenic landscape than cells grown in atmospheric pO2.MethodsWe tested this hypothesis by comparing PCa cells propagated at pO2 = 2 kPa and 20 kPa. To identify potential tumor-associated antigens (TAAs), we prepared PCa cell lysates, resolved them by two-dimensional electrophoresis and immunoblotting using spontaneous antibodies from plasma derived from PCa patients and control subjects. Antibody-labeled spots were analyzed by MALDI-TOF mass spectrometry and validated by ELISA. We selected hypoxia-regulated HSP70 and hnRNP L and hypoxia-independent HSP60 and determined the frequency of plasma samples reacting with these molecules.ResultsFrequency of HSP60-reactive plasma was low in healthy controls [1.3 % (1/76)], while it was elevated in PCa patients [13.0 % (7/54); p < 0.05]. These data suggest a humoral immune response to HSP60 in PCa. Levels of autoantibodies to HSP70 did not differ from healthy controls [3.7 % (2/54)] in PCa patients [5.3 % (2/38)]. Similarly, hnRNP L autoantibodies did no differ between healthy controls [6.1 % (3/49)] and PCa patients [5.3 % (2/38)].ConclusionsOverall our results suggest the value of hypoxia as a modifier of the cellular and antigenic landscape of PCa cells. By modifying the immune reactivity of PCa cells in culture, manipulation of pO2 can be proposed as a new avenue for improving diagnosis, prognosis and immunotherapy for PCa.

Highlights

Use of allogeneic cancer cells-based immunotherapy for treatment of established prostate cancer (PCa) has only been marginally effective
To most solid tumors, PCa tissues are characterized by low oxygen tension–hypoxia–that in PCa is a marker of poor clinical prognosis [4]
PCa cells differ in sensitivity to hypoxia To explore the effect of pO2 on cell viability of PCa cells, we exposed them to pO2 = 20 kPa or 2 kPa

Summary

Introduction

Use of allogeneic cancer cells-based immunotherapy for treatment of established prostate cancer (PCa) has only been marginally effective. One reason for failure could stem from the mismatch of antigenic signatures of vaccine cells and cancer in situ. It is possible that vaccine cells expressed antigens differently than tumor cells in situ. We hypothesized that cells grown in vitro at low oxygen tension (pO2) provide a better antigen match to tumors in situ and could reveal a more relevant antigenic landscape than cells grown in atmospheric pO2. Methods: We tested this hypothesis by comparing PCa cells propagated at pO2 = 2 kPa and 20 kPa. To identify potential tumor-associated antigens (TAAs), we prepared PCa cell lysates, resolved them by two-dimensional electro‐ phoresis and immunoblotting using spontaneous antibodies from plasma derived from PCa patients and control sub‐ jects. Hypoxia is associated with increased chromosomal instability, gene amplification, down-regulation of DNA damage repair pathways, and altered sensitivity to DNA damaging agents [8, 9] contributing to cancer phenotype.

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