Phillip Cornel Joseph, Zaman Shadia, Shentu Shujun, Balakrishnan Kumudha, Zhang Jiexin, Baladandayuthapani Veera, Taverna Pietro, Redkar Sanjeev, Wang Michael, Stellrecht Christine Marie, Gandhi Varsha
Departments of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
J Hematol Oncol. 2013 Dec 10;6:92. doi: 10.1186/1756-8722-6-92.
MET is a receptor tyrosine kinase that is activated by the ligand HGF and this pathway promotes cell survival, migration, and motility. In accordance with its oncogenic role, MET is constitutively active, mutated, or over-expressed in many cancers. Corollary to its impact, inhibition of MET kinase activity causes reduction of the downstream signaling and demise of cells. In myeloma, a B-cell plasma malignancy, MET is neither mutated nor over-expressed, however, HGF is increased in plasma or serum obtained from myeloma patients and this was associated with poor prognosis. The small-molecule, amuvatinib, inhibits MET receptor tyrosine kinase. Based on this background, we hypothesized that targeting the HGF/MET signaling pathway is a rational approach to myeloma therapy and that myeloma cells would be sensitive to amuvatinib.
Expression of MET and HGF mRNAs in normal versus malignant plasma cells was compared during disease progression. Cell death and growth as well as MET signaling pathway were assessed in amuvatinib treated primary myeloma cells and cell lines.
There was a progressive increase in the transcript levels of HGF (but not MET) from normal plasma cells to refractory malignant plasma cells. Amuvatinib readily inhibited MET phosphorylation in primary CD138+ cells from myeloma patients and in concordance, increased cell death. A 48-hr amuvatinib treatment in high HGF-expressing myeloma cell line, U266, resulted in growth inhibition. Levels of cytotoxicity were time-dependent; at 24, 48, and 72 h, amuvatinib (25 μM) resulted in 28%, 40%, and 55% cell death. Consistent with these data, there was an amuvatinib-mediated decrease in MET phosphorylation in the cell line. Amuvatinib at concentrations of 5, 10, or 25 μM readily inhibited HGF-dependent MET, AKT, ERK and GSK-3-beta phosphorylation. MET-mediated effects were not observed in myeloma cell line that has low MET and/or HGF expression.
These data suggest that at the cellular level MET/HGF pathway inclines with myeloma disease progression. Amuvatinib, a small molecule MET kinase inhibitor, is effective in inducing growth inhibition and cell death in myeloma cell lines as well as primary malignant plasma cells. These cytostatic and cytotoxic effects were associated with an impact on MET/HGF pathway.
MET是一种受体酪氨酸激酶，可被配体HGF激活，该信号通路促进细胞存活、迁移和运动。鉴于其致癌作用，MET在许多癌症中呈组成性激活、发生突变或过度表达。相应地，抑制MET激酶活性会导致下游信号传导减少和细胞死亡。在骨髓瘤（一种B细胞浆细胞恶性肿瘤）中，MET既未发生突变也未过度表达，然而，骨髓瘤患者血浆或血清中的HGF水平升高，且这与预后不良相关。小分子药物阿幕瓦替尼可抑制MET受体酪氨酸激酶。基于此背景，我们推测靶向HGF/MET信号通路是骨髓瘤治疗的合理方法，且骨髓瘤细胞对阿幕瓦替尼敏感。
在疾病进展过程中，比较正常与恶性浆细胞中MET和HGF mRNA的表达。评估阿幕瓦替尼处理的原发性骨髓瘤细胞和细胞系中的细胞死亡、生长情况以及MET信号通路。
从正常浆细胞到难治性恶性浆细胞，HGF（而非MET）的转录水平逐渐升高。阿幕瓦替尼可轻易抑制骨髓瘤患者原发性CD138 +细胞中的MET磷酸化，相应地，细胞死亡增加。在高表达HGF的骨髓瘤细胞系U266中进行48小时的阿幕瓦替尼处理，导致细胞生长受到抑制。细胞毒性水平呈时间依赖性；在24、48和72小时时，阿幕瓦替尼（25μM）导致28%、40%和55%的细胞死亡。与这些数据一致，该细胞系中阿幕瓦替尼介导的MET磷酸化减少。浓度为5、10或25μM的阿幕瓦替尼可轻易抑制HGF依赖性MET、AKT、ERK和GSK - 3 - beta的磷酸化。在MET和/或HGF表达较低的骨髓瘤细胞系中未观察到MET介导的效应。
这些数据表明，在细胞水平上，MET/HGF通路随骨髓瘤疾病进展而变化。阿幕瓦替尼，一种小分子MET激酶抑制剂，可有效诱导骨髓瘤细胞系以及原发性恶性浆细胞的生长抑制和细胞死亡。这些细胞生长抑制和细胞毒性作用与对MET/HGF通路的影响相关。
