title: Homoharringtonine contributes to imatinib sensitivity by blocking the EphB4/RhoA pathway in chronic myeloid leukemia cell lines.
abstract: The purpose was to investigate the role of EphB4 in imatinib (IM) resistance and the mechanism responsible for homoharringtonine (HHT) contributing to imatinib sensitivity for a chronic myeloid leukemia (CML) cell lines. We established cell lines from a patient with CML at the time of first diagnosis and relapsed phase and designated them as NPhA1 and NPhA2, respectively. Stable underexpressing EphB4 cells (NPhA2-sh) were obtained. The activated signal proteins in cells were tested by Western blot. The EphB4 was overexpressed in IM-resistant NPhA2 in comparison with the NPhA1 cell line, but the expression of EphB4 mRNA and protein significantly decreased in knockdown NPhA2-EphB4-sh cells compared with NPhA2 and NPhA1 (P < 0.001) cell lines. NPhA2-EphB4-sh cells were sensitive to IM (IC50 0.93 mg/L), and NPhA2 showed IM resistance (IC50 5.45 mg/L) (P < 0.001). Meanwhile, phospho-Rac1/cdc42 was significantly increased in NPhA2 cells compared to NPhA2-EphB4-sh (P < 0.001). The apoptosis rate reached 58.71 ± 2.39 % with NPhA2 cells incubated with HHT + IM, which was higher than NPhA2 cells incubated with IM alone (P = 0.002). IC50 of NPhA2 cells incubated with IM was 5.45 mg/L. However, co-stimulation with HHT + IM decreased the IC50 of NPhA2 cells from 5.45 to 1.17 mg/L (P < 0.001). Furthermore, HHT blocked the expressions of EphB4/RhoA, but did not down-regulate the phospho-MEK/ERK in NPhA2 cells. The overexpression of EphB4 contributed to IM resistance in CML line cells. EphB4/RhoA may be a new marker of IM resistance. HHT + IM gained more treatment advantages than IM alone by blocking EphB4/RhoA pathways in CML cell lines.
authors.affiliation: Department of Hematology, The Affiliated Hospital of Inner Mongolia Medical University, 1 TongDao Avenue North, Hohhot, 010059, People's Republic of China, huangbintao1979@sina.com.
authors.forename: Bin-Tao
authors.initials: BT
authors.lastname: Huang
authors.forename: Qing-Chun
authors.initials: QC
authors.lastname: Zeng
authors.forename: Wei-Hong
authors.initials: WH
authors.lastname: Zhao
authors.forename: Yan
authors.initials: Y
authors.lastname: Tan
mesh_terms: D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides / Q000008:administration & dosage; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004357:Drug Synergism; D006248:Harringtonines / Q000008:administration & dosage; D000077863:Homoharringtonine; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy*; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy; D010879:Piperazines / Q000008:administration & dosage; D011743:Pyrimidines / Q000008:administration & dosage; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D036224:Receptor, EphB4 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors*
chemical_list: D001549:Benzamides; D006248:Harringtonines; D010879:Piperazines; D011743:Pyrimidines; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000077863:Homoharringtonine; D000068877:Imatinib Mesylate; D036224:Receptor, EphB4; D020742:rhoA GTP-Binding Protein