Abstract B68: Erythropoietin stimulates ovarian tumor growth via EphB4.

Abstract

Abstract Background: Recombinant human erythropoietin (rhEpo) has been widely used to treat anemia in cancer patients, concerns about its adverse effects on patient survival have emerged. However the lack of correlation between expression of the canonical EpoR and rhEpo's effects on cancer cells prompted us to consider the existence of an alternative Epo receptor. Methods: We analyzed the membrane-bound portion of the proteome for candidate receptors possessing structural, regulatory, and functional features consistent with Epo binding and tumorigenic signaling. To examine the potential for EphB4 binding to Epo, we generated EpoR-/- MEFs from EpoR-/- mice. We injected A2780-shControl and-shEpoR cells, shEphB4 or -shEpoR/shEphB4 cells in nude mice to study rhEpo induced tumor progression. We also assessed potential effects of tumoral EpoR or EphB4 expression on the effects of ESA treatment in patients with ovarian (N = 175) or breast (N = 88) cancer. Results: Through systems-based approaches we identified EphB4 as an alternate Epo receptor. MST experiments with fluorophore labeled rhEpo demonstrated binding to EpoR with an apparent dissociation constant (KD,app) of 28.0 ± 14.0 nM and EphB4 with a KD,app value of 880.6 ± 128.6 nM. EphB4 and EphrinB2 bound with a KD,app value of 140.5 ± 28.3 nM. We showed that [I125]rhEpo can bind to these cells EpoR-/- MEFs cells. EphB4 triggered the downstream signaling via STAT3 and promoted rhEpo-induced tumor growth and progression. rhEpo stimulated in vivo growth of A2780-shControl (p<0.01) and-shEpoR cells (p<0.01), but not -shEphB4 or -shEpoR/shEphB4 cells. In human ovarian and breast cancer samples, expression of EphB4 rather than the canonical EpoR correlated with decreased disease-specific survival in rhEpo-treated patients. Conclusion: In this study, we identified a new mechanism that EphB4 as a critical mediator of erythropoietin signaling, which induced tumor progression in ovarian cancer patients. Altogether our study provides a novel and clinically significant dimension to the biology of erythropoietin, which was not appreciated before. Citation Format: Sunila Pradeep, Jie Huang, Edna Mora, Sherry Y. Wu, Chun Li, Gabriel Lopez-Berestein, David Jackson, Anil Sood. Erythropoietin stimulates ovarian tumor growth via EphB4. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B68.