title: Erythropoietin receptor expression and its relationship with trastuzumab response and resistance in HER2-positive breast cancer cells.
abstract: Resistance to trastuzumab is a major issue in the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Several potential resistance mechanisms have been investigated, but the results are controversial and no conclusion has been reached. Erythropoietin receptor (EPOR) may function in cell growth, and expressed in various cancer cells. Because the downstream signaling pathways for EPOR and HER2 partially overlapped, we hypothesized that EPOR may play a role in the inhibition effect of trastuzumab and resistance to trastuzumab. Here, we detected the expression of EPOR mRNA and protein in HER2-positive breast cancer cell lines and tissues. EPOR expressed in SKBR3, MDA-MB-453, and UACC-812 cell lines, but not in BT474. Of the 55 HER2-positive cancer tissues, EPOR was positive in 42 samples and highly expressed (H-score ≥ 25) in 24 by immunohistochemistry. The difference between EPOR expression and Ki67 index was significant (P = 0.033), and EPOR expression also positively correlated with higher pathological stage (Spearman correlation coefficient = 0.359; P = 0.007). Exogenous EPO antagonized trastuzumab-induced inhibition of cell proliferation in HER2/EPOR dual-positive breast cancer cells. We then exposed SKBR3 cells to trastuzumab for 4 months to obtain trastuzumab-resistant SKBR3 cell line, which demonstrated higher phosphorylated EPOR level, higher EPO expression and more extracellular secretion than non-resistant parental SKBR3 cells. Downregulation EPOR expression using short hairpin RNA resensitized trastuzumab-resistant cells to this drug, and SKBR3 cells with EPOR downregulation demonstrated attenuated trastuzumab resistance after the same resistance induction. EPOR downregulation plus trastuzumab produced a synergetic action in the inhibition of cell proliferation and invasion in SKBR3 and MDA-MB-453 cell lines. Therefore, EPOR expression may be involved in tumor progression and proliferation in HER2-positive breast cancer. EPO/EPOR contributes to the mechanism of trastuzumab resistance in SKBR3 cell lines, and EPOR downregulation can reverse the resistance to trastuzumab and increase the inhibition effect of this drug.
authors.affiliation: Peking University First Hospital Breast Disease Centre, Xishiku Street 8#, Xicheng District, Beijing, China.
authors.forename: Chi
authors.initials: C
authors.lastname: Zhang
authors.forename: Xuening
authors.initials: X
authors.lastname: Duan
authors.forename: Ling
authors.initials: L
authors.lastname: Xu
authors.forename: Jingming
authors.initials: J
authors.lastname: Ye
authors.forename: Jianxin
authors.initials: J
authors.lastname: Zhao
authors.forename: Yinhua
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001483:Base Sequence; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004921:Erythropoietin / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008875:Middle Aged; D008969:Molecular Sequence Data; D034741:RNA, Small Interfering / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D017467:Receptors, Erythropoietin / Q000235:genetics* / Q000378:metabolism; D000068878:Trastuzumab; D014407:Tumor Cells, Cultured
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D004921:Erythropoietin; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases; D017467:Receptors, Erythropoietin; D000068878:Trastuzumab; C508053:ERBB2 protein, human