Ras-targeted therapy represents a 'holy grail' in oncology. Based on our model prediction, Spiclomazine freezing the intermediate conformation of activated Ras is central to cancer therapeutics. We show here that Spiclomazine leads to an effective suppression in Ras-mediated signaling through abrogating the KRas-GTP level in the KRas-driven pancreatic cancer. The Ras-mediated signaling inhibition leads to dramatically reduced survivals of five KRas-driven pancreatic cancer cell lines with IC50 ranging 19.7~74.2 μM after 48 hours of treatment. However, no significant changes have been observed for normal cell lines. It is worth mentioning that the mutant KRas-driven cancer cells are more sensitive towards Spiclomazine than the wild-type KRas cancer cells. Subsequent cellular thermal shift and RNA interference assays show that Spiclomazine efficiently binds with and stabilizes KRas to a certain extent within the cells. This validates the effect of target engagement on drug efficacy. Furthermore, Spiclomazine arrests cell cycle at G2 phase in the cancer cells, without obvious cell-cycle arrest in the normal cells. This further demonstrates its selectively biological response to cancer cells involved in Ras-GTP-mediated target engagement. Spiclomazine completely inhibits the growth of MIA PaCa-2 tumors on renal capsule xenograft models in BALB/c mice administered 68 mg kg-1 for 2 weeks via intra-peritoneal route. Immunohistochemical analyses reveal the reduced c-Raf and p-ERK and the increase in TUNEL staining. These observations further confirm the in vitro findings. Taken together, Spiclomazine is a selective inhibitor for mutant KRas-driven pancreatic cancer.

中文翻译：

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Spiclomazine在突变型KRas驱动的胰腺癌中显示出优先的抗肿瘤活性。

靶向Ras的疗法代表了肿瘤学上的“圣杯”。根据我们的模型预测，Spiclomazine冻结激活的Ras的中间构象对于癌症治疗至关重要。我们在这里显示Spiclomazine通过废除KRas驱动的胰腺癌中的KRas-GTP水平，导致有效抑制Ras介导的信号传导。Ras介导的信号传导抑制作用导致48个治疗后5个由KRas驱动的胰腺癌细胞株的存活率大大降低，IC50范围为19.7〜74.2μM。但是，对于正常细胞系，没有观察到明显的变化。值得一提的是，突变型KRas驱动的癌细胞对Spiclomazine的敏感性比野生型KRas癌细胞高。随后的细胞热迁移和RNA干扰分析表明，Spiclomazine在细胞内有效结合KRas并将其稳定到一定程度。这验证了靶标参与对药物功效的影响。此外，Spiclomazine使癌细胞的G2期细胞周期停滞，而在正常细胞中没有明显的细胞周期停滞。这进一步证明了其对参与Ras-GTP介导的靶标参与的癌细胞的选择性生物学反应。在通过腹膜内途径施用68 mg kg-1 2周的BALB / c小鼠的肾囊异种移植模型中，Spiclomazine完全抑制MIA PaCa-2肿瘤的生长。免疫组织化学分析显示c-Raf和p-ERK减少，TUNEL染色增加。这些观察结果进一步证实了体外发现。在一起