Thorough preclinical target validation is essential for the success of drug discovery efforts. In this study, we combined chemical and genetic perturbants, including the development of a novel selective maternal embryonic leucine zipper kinase (MELK) inhibitor HTH-01-091, CRISPR/Cas9-mediated MELK knockout, a novel chemical-induced protein degradation strategy, RNA interference and CRISPR interference to validate MELK as a therapeutic target in basal-like breast cancers (BBC). In common culture conditions, we found that small molecule inhibition, genetic deletion, or acute depletion of MELK did not significantly affect cellular growth. This discrepancy to previous findings illuminated selectivity issues of the widely used MELK inhibitor OTSSP167, and potential off-target effects of MELK-targeting short hairpins. The different genetic and chemical tools developed here allow for the identification and validation of any causal roles MELK may play in cancer biology, which will be required to guide future MELK drug discovery efforts. Furthermore, our study provides a general framework for preclinical target validation.

中文翻译：

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MELK对于基底样乳腺癌细胞的增殖不是必需的

彻底的临床前靶标验证对于药物发现工作的成功至关重要。在这项研究中，我们结合了化学和遗传干扰因素，包括开发一种新型选择性母体胚胎亮氨酸拉链激酶 (MELK) 抑制剂 HTH-01-091、CRISPR/Cas9 介导的 MELK 敲除、一种新型化学诱导蛋白质降解策略、 RNA 干扰和 CRISPR 干扰验证 MELK 作为基底样乳腺癌 (BBC) 的治疗靶点。在常见的培养条件下，我们发现 MELK 的小分子抑制、基因缺失或急性消耗不会显着影响细胞生长。这种与先前发现的差异说明了广泛使用的 MELK 抑制剂 OTSSP167 的选择性问题，以及靶向 MELK 的短发夹的潜在脱靶效应。这里开发的不同遗传和化学工具允许识别和验证 MELK 在癌症生物学中可能发挥的任何因果作用，这将需要指导未来的 MELK 药物发现工作。此外，我们的研究为临床前目标验证提供了一个通用框架。