Erythropoietin promotes breast tumorigenesis through tumor-initiating cell self-renewal
Bing Zhou, Jeffrey S. Damrauer, Sean T. Bailey, Tanja Hadzic, Youngtae Jeong, Kelly Clark, Cheng Fan, Laura Murphy, Cleo Y. Lee, Melissa A. Troester, C. Ryan Miller, Jian Jin, David Darr, Charles M. Perou, Ross L. Levine, Maximilian Diehn, William Y. Kim
Bing Zhou, Jeffrey S. Damrauer, Sean T. Bailey, Tanja Hadzic, Youngtae Jeong, Kelly Clark, Cheng Fan, Laura Murphy, Cleo Y. Lee, Melissa A. Troester, C. Ryan Miller, Jian Jin, David Darr, Charles M. Perou, Ross L. Levine, Maximilian Diehn, William Y. Kim
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Research Article Oncology

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

Abstract

Erythropoietin (EPO) is a hormone that induces red blood cell production. In its recombinant form, EPO is the one of most prescribed drugs to treat anemia, including that arising in cancer patients. In randomized trials, EPO administration to cancer patients has been associated with decreased survival. Here, we investigated the impact of EPO modulation on tumorigenesis. Using genetically engineered mouse models of breast cancer, we found that EPO promoted tumorigenesis by activating JAK/STAT signaling in breast tumor-initiating cells (TICs) and promoted TIC self renewal. We determined that EPO was induced by hypoxia in breast cancer cell lines, but not in human mammary epithelial cells. Additionally, we demonstrated that high levels of endogenous EPO gene expression correlated with shortened relapse-free survival and that pharmacologic JAK2 inhibition was synergistic with chemotherapy for tumor growth inhibition in vivo. These data define an active role for endogenous EPO in breast cancer progression and breast TIC self-renewal and reveal a potential application of EPO pathway inhibition in breast cancer therapy.

Authors

Bing Zhou, Jeffrey S. Damrauer, Sean T. Bailey, Tanja Hadzic, Youngtae Jeong, Kelly Clark, Cheng Fan, Laura Murphy, Cleo Y. Lee, Melissa A. Troester, C. Ryan Miller, Jian Jin, David Darr, Charles M. Perou, Ross L. Levine, Maximilian Diehn, William Y. Kim

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Figure 4

EPO promotes mammosphere formation, TIC self renewal, and expansion of TICs in vivo.

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EPO promotes mammosphere formation, TIC self renewal, and expansion of T...
(A) Mammosphere formation of FACS-sorted SUM149 cells. 20,000 cells from each subpopulation were plated in triplicate in 6-well plates. PBS or EPO (1 IU/ml) were added every other day, and colonies (≥ 50 μm) were counted on day 5. (B) Representative photos of mammospheres from PBS- or EPO-treated SUM149 cells. Scale bars: 200 mm. (C) Primary mammospheres from SUM149 TICs (CD44+CD24–EpCAM+) were dissociated and serial passaged by replating 20,000 cells for each passage. TICs cultured in PBS showed a significant exhaustion of self-renewal capacity after passage 3. (D) Mammosphere formation of Lin–Thy1+CD24+MMTV-Wnt1 cells cultured with PBS or EPO under 21% O2. Non-Lin–Thy+CD24+ cells did not grow spheres. (E) Representative photos of spheres from Lin-Thy1+CD24+MMTV-Wnt1 cells treated with PBS or EPO. Original magnification, ×1. (F) Schematic of orthotopically implanted MMTV-Wnt1 tumors treated with PBS or EPO (500 IU/kg i.p. twice a week) for 4 weeks then assessed for TIC frequency by flow cytometry and LDA. (G) MMTV-Wnt1 orthotopic tumors were harvested and stained with antibodies specific to Thy1, CD24, a lineage cocktail, and DAPI. There were a significantly higher percentage of Lin–Thy+CD24+ cells in tumors of mice treated with EPO. **P ≤ 0.01; ***P ≤ 0.001.