Effects of recombinant erythropoietin on breast cancer-initiating cells.
BACKGROUND
Cancer anemia causes fatigue and correlates with poor treatment outcome. Erythropoietin has been introduced in an attempt to correct these defects. However, five recent clinical trials reported a negative impact of erythropoietin on survival and/or tumor control, indicating that experimental evaluation of a possible direct effect of erythropoietin on cancer cells is required. Cancer recurrence is thought to rely on the proliferation of cancer initiating cells (CICs). In breast cancer, CICs can be identified by phenotypic markers and their fate is controlled by the Notch pathway.


METHODS
In this study, we investigated the effect of erythropoietin on CICs in breast cancer cell lines. Levels of erythropoietin receptor (EpoR), CD24, CD44, Jagged-1 expression, and activation of Notch-1 were assessed by flow cytometry. Self-renewing capacity of CICs was investigated in sphere formation assays.


RESULTS
EpoR expression was found on the surface of CICs. Recombinant human Epo (rhEpo) increased the numbers of CICs and self-renewing capacity in a Notch-dependent fashion by induction of Jagged-1. Inhibitors of the Notch pathway and PI3-kinase blocked both effects.


CONCLUSIONS
Erythropoietin functionally affects CICs directly. Our observation may explain the negative impact of recombinant Epo on local control and survival of cancer patients with EpoR-positive tumors.
Phillips
Tiffany M
TM
Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, 10833 LeConte Ave, Los Angeles, CA 90095-1714, USA.
Kim
Kwanghee
K
Vlashi
Erina
E
McBride
William H
WH
Pajonk
Frank
F
D000230:Adenocarcinoma / Q000737:chemistry / Q000473:pathology*; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors / Q000502:physiology; D001943:Breast Neoplasms / Q000737:chemistry / Q000473:pathology*; D002448:Cell Adhesion / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D004921:Erythropoietin / Q000009:adverse effects / Q000494:pharmacology*; D005260:Female; D006801:Humans; D018960:Hyaluronan Receptors / Q000096:biosynthesis / Q000235:genetics; D009025:Morpholines / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000819:agonists* / Q000502:physiology; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051881:Receptor, Notch1 / Q000235:genetics / Q000502:physiology; D017467:Receptors, Erythropoietin / Q000819:agonists* / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D011994:Recombinant Proteins; D051918:Sialic Acid Binding Ig-like Lectin 2 / Q000096:biosynthesis / Q000235:genetics; D018874:Spheroids, Cellular / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
D053829:Amyloid Precursor Protein Secretases; D002867:Chromones; D004921:Erythropoietin; D018960:Hyaluronan Receptors; D009025:Morpholines; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051881:Receptor, Notch1; D017467:Receptors, Erythropoietin; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D051918:Sialic Acid Binding Ig-like Lectin 2; C497867:CD22 protein, human; C497483:CD44 protein, human; C497761:NOTCH1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one