Cancer Res:ROCK抑制剂RKI-1447或抵抗乳腺癌

Rho相关激酶ROCK1和ROCK2肿瘤细胞迁移和侵袭的关键，这表明它们可能是有用的治疗靶点。在这项研究中，研究者发现一个强有力的ROCK1和ROCK2的小分子抑制剂RKI-1447。

RKI-1447/ROCK1复合物晶体结构显示，RKI-1447是一个I型激酶抑制剂，通过铰链区和DFG结构域的相互作用与ATP结合位点相结合。 在人类癌细胞中，RKI-1447抑制ROCK底物MLC-2和 MYPT-1的磷酸化，但在高达10μM的药物浓度下，不影响AKT，MEK和S6激酶的磷酸化水平的。

RKI-1447高度选择性抑制LPA刺激引发的，ROCK介导的细胞骨架重新组织（肌动蛋白应力纤维的形成），但并不影响分别发生于PDGF及血管缓激肽刺激后的，PAK介导的板状伪足和丝状伪足形成。 RKI-1447抑制乳腺癌细胞迁移，侵袭和不依赖于锚定的肿瘤生长。 相反，类似物RKI-1313，在体外实验中对ROCK底物的磷酸化水平，肿瘤细胞迁移，入侵或不依赖于锚定的生长影响都不大。最后RKI-1447可高度有效抑制乳腺肿瘤在转基因小鼠模型中的生长。

总之，本研究结果证实，作为强有力的和有选择性的ROCK抑制剂，RKI-1447可发挥显著的抗侵袭和抗肿瘤活性，并为进一步的临床验证打下了基础。

doi:10.1016/j.cell.2011.10.017
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RKI-1447 is a potent inhibitor of the Rho-associated ROCK kinases with anti-invasive and anti-tumor activities in breast cancer

Ronil A. Patel1,Kara D. Forinash1,Roberta Pireddu2,Ying Sun1,Nan Sun1,Mathew P. Martin1,Ernst Schonbrunn1,Nicholas J. Lawrence1, andSaid M. Sebti3,*

The Rho-associated kinases ROCK1 and ROCK2 are critical for cancer cell migration and invasion, suggesting they may be useful therapeutic targets. In this study, we describe the discovery and development of RKI-1447, a potent small molecule inhibitor of ROCK1 and ROCK2. Crystal structures of the RKI-1447/ROCK1 complex revealed that RKI-1447 is a Type I kinase inhibitor that binds the ATP binding site through interactions with the hinge region and the DFG motif. RKI-1447 suppressed phosphorylation of the ROCK substrates MLC-2 and MYPT-1 in human cancer cells, but had no effect on the phosphorylation levels of the AKT, MEK and S6 kinase at concentrations as high as10 μM. RKI-1447 was also highly selective at inhibiting ROCK-mediated cytoskeleton re-organization (actin stress fiber formation) following LPA stimulation, but does not affect PAK-meditated lamellipodia and filopodia formation following PDGF and Bradykinin stimulation, respectively. RKI-1447 inhibited migration, invasion and anchorage-independent tumor growth of breast cancer cells. In contrast, RKI-1313, a much weaker analog in vitro, had little effect on the phosphorylation levels of ROCK substrates, migration, invasion or anchorage-independent growth. Lastly RKI-1447 was highly effective at inhibiting the outgrowth of mammary tumors in a transgenic mouse model. In summary, our findings establish RKI-1447 as a potent and selective ROCK inhibitor with significant anti-invasive and anti-tumor activities and offer a preclinical proof-of-concept that justify further examination of RKI-1447 suitability as a potential clinical candidate.