Recombinant Human Erythropoietin in Combination with Chemotherapy Increases Breast Cancer Metastasis in Preclinical Mouse Models

Abstract

Purpose: Erythropoiesis-stimulating agents (ESA) are used clinically for treating cancer-related anemia. Recent clinical trials have reported increased adverse events and reduced survival in ESA-treated breast cancer patients receiving chemotherapy, potentially related to erythropoietin (EPO)-induced cancer progression. However, minimal preclinical data are available about the impact of EPO on metastatic cell behavior and/or the metastatic process, and this was the goal of our study.Experimental Design: Breast cancer cell lines were treated with recombinant human EPO (rHuEPO) and screened for expression of EPO receptors (EPOR). MDA-MB-231 and MDA-MB-435 cell lines were used for functional assays in vitro (two-dimensional/three-dimensional growth and survival) and in vivo (tumorigenicity and metastasis), in the presence or absence of EPO and/or cytotoxic agents.Results: A large variation in EPOR expression across cell lines was observed. In vitro, rHuEPO had a protective effect on radiation-treated MDA-MB-435 cells (P < 0.05); however, rHuEPO treatment alone or combined with chemotherapy or hypoxia did not influence cell survival. In vivo, rHuEPO increased lung metastases in immunocompromised mice injected with MDA-MB-231 or MDA-MB-435 cells and treated with chemotherapy relative to mice treated with chemotherapy alone (P < 0.05).Conclusions: The lack of an in vitro effect of rHuEPO highlights the importance of in vivo studies to delineate the effects of EPO on the metastatic process. These studies may begin to uncover the underlying functional explanation for the observed EPO-related adverse events and decreased survival in ESA-treated metastatic breast cancer patients undergoing chemotherapy.

Erythropoietin Activates Cell Survival Pathways in Breast Cancer Stem–like Cells to Protect Them from Chemotherapy

“…We have shown for the first time that EPO can bind and stimulate BCSCs, resulting in increased tumor growth and chemoresistance. These results confirm and expand previous observations by Hedley and colleagues on xenografts obtained with breast cancer cell lines (10). In patients with breast cancer, EPO-mediated BCSC stimulation may not result in immediate effects on tumor growth or response to chemotherapy, as BCSCs represent a minority of cells, but may favor subsequent tumor relapse.…”

“…Recent in vivo studies, however, provided important clues on tumors' response to EPO. Specifically, EPO was shown to antagonize the effect of trastuzumab on breast cancer xenografts and to decrease the effect of chemotherapy in a mouse model of metastatic breast cancer (9,10). Such studies suggest a direct influence of EPO on breast tumors and highlight the importance of reliable in vivo models to elucidate the interactions between EPO and tumor cells.…”

Erythropoietin and Cancer: The Unintended Consequences of Anemia Correction

“…In vitro , EPO had a protective effect on radiation-treated MDA-MB-435 cells; however, EPO treatment alone or combined with chemotherapy or hypoxia did not influence cell survival. In vivo , EPO increased lung metastases in immunocompromised mice injected with MDA-MB-231 or MDA-MB-435 cells and treated with chemotherapy relative to mice treated with chemotherapy alone (90). …”

Erythropoietin promotes breast tumorigenesis through tumor-initiating cell self-renewal

“…A number of preclinical studies have examined the role of EPO with a wide range of in vitro findings (6)(7)(8)(22)(23)(24)(25)(26)(27). In contrast, in various in vivo xenograft tumor models, exogenous EPO does not significantly promote tumor growth or result in resistance to therapy (6-8, 22, 23) with the exception of Lewis lung carcinoma xenografts and carcinogen-induced fibrosarcomas (28).…”