RNA Interference-Mediated Inhibition of Erythropoietin Receptor Expression Suppresses Tumor Growth and Invasiveness in A2780 Human Ovarian Carcinoma Cells

Abstract

Although recombinant human erythropoietin (rHuEpo) has revolutionized the treatment of anemia, recent clinical trials suggested that rHuEpo use may be associated with decreased survival in cancer patients. Although the expression of erythropoietin (Epo) receptor (EpoR) has been demonstrated in various human cancers, the effect of exogenous Epo on the growth and therapy resistance of EpoR-bearing tumor cells is unclear at present. In the current study, we examined the hypothesis that EpoR may contribute to tumor growth independent of Epo in A2780 human ovarian carcinoma cells. A2780 human ovarian carcinoma cells showed high levels of EpoR expression, but lacked expression of Epo mRNA and biologically active Epo protein under both normoxic and hypoxic conditions. Exogenous Epo did not stimulate EpoR-mediated signaling, proliferation, invasiveness, or resistance to cytotoxic drugs in A2780 cells. In contrast, specific inhibition of EpoR expression using a short hairpin RNA (shRNA) expression plasmid resulted in markedly reduced proliferation and invasiveness in vitro. In addition, inhibition of EpoR expression led to abrogated in vivo ovarian cancer cell growth in a tumor xenograft system and resulted in decreased EpoR signaling. Our findings suggest that EpoR may be constitutively active in some cancer cells in the absence of Epo and provide the first evidence for a potential role of an Epo-independent, EpoR-mediated pathway in the growth of some human cancers.

Erythropoietin-Induced Activation of the JAK2/STAT5, PI3K/Akt, and Ras/ERK Pathways Promotes Malignant Cell Behavior in a Modified Breast Cancer Cell Line

“…However, further studies are needed with more specific antibodies and greater sample numbers to determine the prognostic significance of EpoR expression on tumors. The biological effects of Epo stimulation of tumor cells is still debated with reports of enhanced survival (8,11), proliferation (4,6,(38)(39)(40), resistance to treatment (38,41,42), tumor angiogenesis (43)(44)(45), chemotaxis (46), invasion (47)(48)(49)(50), and migration (40,46,51). Others have reported no discernible effects of Epo (52).…”

RNA Interference for Tumor Therapy

“…Many recent studies have discovered extensive expressions of EPO and EPOR in many malignant tumors, the autocrine/paracrine pathways of which are associated with tumor microangiogenesis, stimulation of tumor cell proliferation and sensitivity to chemotherapy. In addition, Paragh (Paragh et al, 2009) found that EPOR had a function independent of EPO in tumors. It was found that EPOR was highly expressed in ovarian cancer A2780 cell line, but no expression of EPO was observed in normal or hypoxic conditions.…”

“…Use of exogenous EPO to intervene 2780 cells did not alter their biological effect. Paragh (Paragh et al, 2009) transplanted ovarian cancer cells treated with EPORtarget shRNA and those with a negative control vector in mice subcutaneously for 7 weeks, and found that the mean tumor size of the negative control group was 10-fold larger than that of the intervention group. This difference in tumor size is mainly due to decreased cell proliferation in the intervention group.…”

Erythropoietin and Ovarian Cancer – Response

“…Interestingly, other studies have shown EpoR on the same A2780 and SKOV3 cells using a different antibody (2,3). Furthermore, the study of Paragh et al (3) has revealed that specific inhibition of EpoR expression using a short hairpin RNA expression plasmid resulted in markedly reduced proliferation and invasiveness of ovarian cancer cells in vitro and led to abrogated growth of these cells with decreased EpoR signaling in vivo.…”

“…Furthermore, the study of Paragh et al (3) has revealed that specific inhibition of EpoR expression using a short hairpin RNA expression plasmid resulted in markedly reduced proliferation and invasiveness of ovarian cancer cells in vitro and led to abrogated growth of these cells with decreased EpoR signaling in vivo. Analogous results have been shown by one of our groups for human prostate cancer cells, which also express a functional EpoR and exhibit Epo-induced signal transduction and Epo-dependent phenotypic properties (4).…”