高三尖杉酯碱增强慢性粒细胞白血病细胞对于伊马替尼敏感性的研究*

目的: 研究高三尖杉酯碱（HHT）增强慢性粒细胞白血病（CML）细胞对伊马替尼（IM）敏感性的机制。 方法: 采集1例CML患者骨髓血标本，经体外筛选、克隆建立人白血病细胞株NPHA1（初治）和NPHA2（复发）。RNA干扰NPHA2细胞的EphB4蛋白表达，建立NPHA2-EphB4-sh细胞株。 结果: 与NPHA1细胞相比，耐IM的NPHA2细胞中EphB4过表达；在NPHA2-EphB4-sh细胞中，EphB4表达显著低于NPHA1细胞和NPHA2细胞（P<0.001）。NPHA2细胞对IM有明显耐药性（IC₅₀=5.45 mg/L），但NPHA2-EphB4-sh对IM敏感性增加（IC₅₀=0.93 mg/L，P<0.001）。HHT与IM共处理后，NPHA2细胞对IM的IC50值降至1.17 mg/L（P<0.001）。蛋白磷酸化测定表明HHT抑制了EphB4/RhoA通路表达。 结论: EphB4/RhoA是一个新的IM耐药途径。HHT通过抑制EphB4/RhoA途径，使IM治疗获得优势。 

Homoharringtonine contributes to imatinib sensitivity in chronic myeloid leukemia cell lines

Objective: To investigate the mechanism responsible for homoharringtonine (HHT), which contributes to imatinib(IM) sensitivity in the chronic myeloid leukemia (CML) cell line. Methods: We established cell lines from a patient with CML at thetime of first diagnosis and relapse phase, and designated the cell lines as NPHA1 and NPHA2, respectively. Stable underexpressedEphB4 cells (NPHA2-EphB4-sh) were obtained. Leukemia cell lines were incubated with HHT. The activated signal proteins in cellswere tested by Western blot. Results: EphB4 was overexpressed in IM-resistant NPHA2 compared with the NPHA1 cell line. However, the expression of EphB4 mRNA and protein were significantly decreased in knockdown NPHA2-EphB4-sh cells compared with theNPHA2 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). However, co-stimulation with HHT+IM decreased IC50 of NPHA2 cells to 1.17 mg/L (P＜0.001). Meanwhile, phospho-Rac1/cdc42 was significantly increased in NPHA2 cells compared with NPHA2-EphB4-sh (P<0.001).HHT blocked the expression of EphB4/RhoA. Conclusion: The overexpression of EphB4 contributed to IM resistance in CML linecells. EphB4/RhoA may be a new marker of IM resistance. HHT with IM yielded more treatment advantages than IM alone by blockingEphB4/RhoA pathways.