Ribonucleotide reductase (RNR) is the key enzyme that catalyzes the production of deoxyribonucleotides (dNTPs) for DNA replication and it is also essential for cancer cell proliferation. As the RNR inhibitor, Gemcitabine is widely used in cancer therapies, however, resistance limits its therapeutic efficacy and curative potential. Here, we identified that mTORC2 is a main driver of gemcitabine resistance in non-small cell lung cancers (NSCLC). Pharmacological or genetic inhibition of mTORC2 greatly enhanced gemcitabine induced cytotoxicity and DNA damage. Mechanistically, mTORC2 directly interacted and phosphorylated RNR large subunit RRM1 at Ser 631. Ser631 phosphorylation of RRM1 enhanced its interaction with small subunit RRM2 to maintain sufficient RNR enzymatic activity for efficient DNA replication. Targeting mTORC2 retarded DNA replication fork progression and improved therapeutic efficacy of gemcitabine in NSCLC xenograft model in vivo. Thus, these results identified a mechanism through mTORC2 regulating RNR activity and DNA replication, conferring gemcitabine resistance to cancer cells.

核糖核苷酸还原酶 (RNR) 是催化 DNA 复制产生脱氧核糖核苷酸 (dNTP) 的关键酶，它也是癌细胞增殖所必需的。作为 RNR 抑制剂，吉西他滨广泛用于癌症治疗，但耐药性限制了其治疗效果和治疗潜力。在这里，我们发现 mTORC2 是非小细胞肺癌 (NSCLC) 中吉西他滨耐药的主要驱动因素。mTORC2 的药理学或遗传抑制极大地增强了吉西他滨诱导的细胞毒性和 DNA 损伤。从机制上讲，mTORC2 在 Ser 631 处直接与 RNR 大亚基 RRM1 相互作用并磷酸化。RRM1 的 Ser631 磷酸化增强了其与小亚基 RRM2 的相互作用，以保持足够的 RNR 酶活性以进行有效的 DNA 复制。在体内。因此，这些结果确定了通过 mTORC2 调节 RNR 活性和 DNA 复制的机制，从而赋予癌细胞对吉西他滨的抗性。