USP11属于半胱氨酸蛋白酶，是去泛素化酶中泛素特异性蛋白酶家族成员。在前期探索性研究中，我们发现USP11在非小细胞肺癌（NSCLC）临床样本中低表达，并通过影响细胞周期，抑制NSCLC细胞的增殖。为了探寻USP11抑制NSCLC增殖的分子机制，我们通过GST Pull-down发现USP11与细胞周期素依赖性激酶抑制子p21在体外相互作用，其对NSCLC细胞内p21蛋白水平的影响，促使我们推测USP11很可能在NSCLC细胞内与p21相互作用，通过去泛素化并稳定p21，直接逆转p21的泛素化过程，导致细胞周期的停滞，从而抑制NSCLC细胞的增殖。本项目对上述科学假说的证明，将有助于揭示细胞内p21的去泛素化过程，进一步拓宽我们对细胞周期调控理论的认识，明确USP11在NSCLC中的分子功能，为防治NSCLC提供新的靶标和切入点。

USP11 as a cysteine protease is a member of the ubiquitin-specific protease family. Our preliminary data show that USP11 is expressed at low levels in the clinical tissues of non-small cell lung cancer (NSCLC), and inhibits the proliferation of NSCLC cells by affecting cell cycle progression. To explore the potential molecular mechanism of USP11 in NSCLC, we found that USP11 directly interacts with p21 in vitro by GST pull-down. Considerating that the effect of USP11 on p21 protein level in NSCLC cells, it prompt us to propose a hypothesis that USP11 may deubiquitinate and stabilize p21 by interaction, which causes cell cycle arrest and inhibits the proliferation of NSCLC. This program may offer beneficial information to understand the deubiquitinating process of p21 in cell cycle progression and shed light on the molecular function of USP11 in NSCLC, which will contribute to the prevention and treatment of NSCLC.