Etnyre Deven, Stone Amanda L, Fong Jason T, Jacobs Ryan J, Uppada Srijayaprakash B, Botting Gregory M, Rajanna Supriya, Moravec David N, Shambannagari Manohar R, Crees Zachary, Girard Jennifer, Bertram Ceyda, Puri Neelu
Department of Biomedical Sciences; University of Illinois College of Medicine; Rockford, IL USA.
Cancer Biol Ther. 2014 Sep;15(9):1129-41. doi: 10.4161/cbt.29451. Epub 2014 Jun 11.
Numerous tyrosine kinase inhibitors (TKIs) targeting c-Met are currently in clinical trials for several cancers. Their efficacy is limited due to the development of resistance. The present study aims to elucidate this mechanism of c-Met TKI resistance by investigating key mTOR and Wnt signaling proteins in melanoma cell lines resistant to SU11274, a c-Met TKI. Xenografts from RU melanoma cells treated with c-Met TKIs SU11274 and JNJ38877605 showed a 7- and 6-fold reduction in tumor size, respectively. Resistant cells displayed upregulation of phosphorylated c-Met, mTOR, p70S6Kinase, 4E-BP1, ERK, LRP6, and active β-catenin. In addition, GATA-6, a Wnt signaling regulator, was upregulated, and Axin, a negative regulator of the Wnt pathway, was downregulated in resistant cells. Modulation of these mTOR and Wnt pathway proteins was also prevented by combination treatment with SU11274, everolimus, an mTOR inhibitor, and XAV939, a Wnt inhibitor. Treatment with everolimus, resulted in 56% growth inhibition, and a triple combination of SU11274, everolimus and XAV939, resulted in 95% growth inhibition in RU cells. The V600E BRAF mutation was found to be positive only in MU cells. Combination treatment with a c-Met TKI and a BRAF inhibitor displayed a synergistic effect in reducing MU cell viability. These studies indicate activation of mTOR and Wnt signaling pathways in c-Met TKI resistant melanoma cells and suggest that concurrent targeting of c-Met, mTOR, and Wnt pathways and BRAF may improve efficacy over traditional TKI monotherapy in melanoma patients.
目前，多种靶向c-Met的酪氨酸激酶抑制剂（TKIs）正处于针对多种癌症的临床试验阶段。由于耐药性的产生，它们的疗效受到限制。本研究旨在通过调查对c-Met TKI SU11274耐药的黑色素瘤细胞系中的关键mTOR和Wnt信号蛋白，阐明c-Met TKI耐药的机制。用c-Met TKIs SU11274和JNJ38877605处理的RU黑色素瘤细胞异种移植瘤的肿瘤大小分别缩小了7倍和6倍。耐药细胞显示磷酸化c-Met、mTOR、p70S6激酶、4E-BP1、ERK、LRP6和活性β-连环蛋白上调。此外，Wnt信号调节因子GATA-6在耐药细胞中上调，而Wnt途径的负调节因子Axin下调。SU11274与mTOR抑制剂依维莫司和Wnt抑制剂XAV939联合治疗也可防止这些mTOR和Wnt途径蛋白的调节。依维莫司治疗导致RU细胞生长抑制56%，SU11274、依维莫司和XAV939三联组合导致RU细胞生长抑制95%。发现V600E BRAF突变仅在MU细胞中呈阳性。c-Met TKI与BRAF抑制剂联合治疗在降低MU细胞活力方面显示出协同作用。这些研究表明mTOR和Wnt信号通路在c-Met TKI耐药的黑色素瘤细胞中被激活，并表明同时靶向c-Met、mTOR和Wnt途径以及BRAF可能比传统的TKI单药治疗更能提高黑色素瘤患者的疗效。
