对头颈鳞状细胞癌 (HNSCC) 肿瘤基因组的全面基因组分析显示，在大多数 HPV 阴性的 HNSCC 病变中，p16INK4A (CDKN2A) 频繁丢失，细胞周期蛋白 D1 (CCND1) 基因频繁扩增。然而，细胞周期蛋白依赖性激酶 4 和 6 (CDK4/6) 抑制剂在临床中显示出有限的效果。 PI3K/mTOR 通路的异常激活在 HNSCC 中非常普遍，最近的临床试验表明 mTOR 抑制剂 (mTORi) 在新辅助和辅助治疗中具有良好的临床疗效，但在晚期 HNSCC 患者中则不然。通过全激酶组 CRISPR/Cas9 筛选，我们确定细胞周期抑制是 mTORi 的合成致死靶点。 mTORi 和 CDK4/6 特异性抑制剂 palbociclib 的组合在体外和体内的 HNSCC 衍生细胞中显示出很强的协同作用。值得注意的是，我们发现 palbociclib 治疗后细胞周期蛋白 E1 (CCNE1) 表达的适应性增加是对该 CDK4/6 抑制剂快速获得耐药性的基础。从机制上讲，mTORi 抑制 eIF4G-CCNE1 mRNA 复合物的形成，从而减少 mRNA 翻译和 CCNE1 蛋白表达。我们的研究结果表明，mTORi 可恢复对哌柏西利的适应性耐药。这通过共同靶向 mTOR 和 CDK4/6 为 HNSCC 提供了一种多模式治疗选择，这反过来又可能阻止帕博西尼耐药的出现。

The comprehensive genomic analysis of the head and neck squamous cell carcinoma (HNSCC) oncogenome revealed the frequent loss of p16INK4A (CDKN2A) and amplification of cyclin D1 (CCND1) genes in most HPV negative HNSCC lesions. However, cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors have shown modest effects in the clinic. The aberrant activation of PI3K/mTOR pathway is highly prevalent in HNSCC, and recent clinical trials have shown promising clinical efficacy of mTOR inhibitors (mTORi) in the neoadjuvant and adjuvant settings but not in advanced HNSCC patients. By a kinome-wide CRISPR/Cas9 screen, we identified cell cycle inhibition as a synthetic lethal target for mTORi. Combination of mTORi and palbociclib, a CDK4/6 specific inhibitor, showed strong synergism in HNSCC-derived cells in vitro and in vivo. Remarkably, we found that adaptive increase in cyclin E1 (CCNE1) expression upon palbociclib treatment underlies the rapid acquired resistance to this CDK4/6 inhibitor. Mechanistically, mTORi inhibits the formation of eIF4G-CCNE1 mRNA complexes, with the consequent reduction in mRNA translation and CCNE1 protein expression. Our findings suggest that mTORi reverts the adaptive resistance to palbociclib. This provides a multimodal therapeutic option for HNSCC by co-targeting mTOR and CDK4/6, which in turn may halt the emergence of palbociclib resistance.