BACKGROUND Chitinase 3 like 1 protein (Chi3L1) is expressed in several cancers, and a few evidences suggest that the secreted Chi3L1 contributes to tumor development. However, the molecular mechanisms of intracellular Chi3L1 are unknown in the lung tumor development. METHODS In the present study, we generated Chi3L1 knockout mice (Chi3L1KO(-/-)) using CRISPR/Cas9 system to investigate the role of Chi3L1 on lung tumorigenesis. RESULTS We established lung metastasis induced by i.v. injections of B16F10 in Chi3L1KO(-/-). The lung tumor nodules were significantly reduced in Chi3L1KO(-/-) and protein levels of p53, p21, BAX, and cleaved-caspase 3 were significantly increased in Chi3L1KO(-/-), while protein levels of cyclin E1, CDK2, and phsphorylation of STAT3 were decreased in Chi3L1KO(-/-). Allograft mice inoculated with B16F10 also suppressed tumor growth and increased p53 and its target proteins including p21 and BAX. In addition, knockdown of Chi3L1 in lung cancer cells inhibited lung cancer cell growth and upregulated p53 expression with p21 and BAX, and a decrease in phosphorylation of STAT3. Furthermore, we found that intracellular Chi3L1 physically interacted and colocalized with p53 to inhibit its protein stability and transcriptional activity for target genes related with cell cycle arrest and apoptosis. In lung tumor patient, we clinically found that Chi3L1 expression was upregulated with a decrease in p53 expression, as well as we validated that intracellular Chi3L1 was colocalized, reversely expressed, and physically interacted with p53, which results in suppression of the expression and function of p53 in lung tumor patient. CONCLUSIONS Our studies suggest that intracellular Chi3L1 plays a critical role in the lung tumorigenesis by regulating its novel target protein, p53 in both an in vitro and in vivo system.

中文翻译：

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几丁质酶3像1一样抑制p53的稳定性和活性，从而促进肺肿瘤发生。

背景技术几丁质酶3样1蛋白（Chi3L1）在几种癌症中表达，一些证据表明分泌的Chi3L1有助于肿瘤的发展。然而，细胞内Chi3L1的分子机制尚不清楚在肺肿瘤的发展。方法在本研究中，我们使用CRISPR / Cas9系统产生了Chi3L1基因敲除小鼠（Chi3L1KO（-/-）），以研究Chi3L1在肺肿瘤发生中的作用。结果我们建立了在Chi3L1KO（-/-）中静脉注射B16F10诱导的肺转移。Chi3L1KO（-/-）中的肺肿瘤结节显着减少，Chi3L1KO（-/-）中p53，p21，BAX和Caspase 3的蛋白水平显着增加，而cyclin E1，CDK2和Chi3L1KO（-/-）中的STAT3磷酸化降低。接种了B16F10的同种异体移植小鼠也抑制了肿瘤生长，并增加了p53及其靶蛋白（包括p21和BAX）。此外，Chi3L1在肺癌细胞中的抑制可抑制肺癌细胞的生长，并通过p21和BAX上调p53表达，并降低STAT3的磷酸化。此外，我们发现细胞内Chi3L1与p53物理相互作用并共定位，以抑制其蛋白稳定性和针对与细胞周期停滞和凋亡相关的靶基因的转录活性。在肺肿瘤患者中，我们临床发现Chi3L1表达上调而p53表达降低，并且我们验证了细胞内Chi3L1与p53共定位，反向表达并发生物理相互作用，从而抑制了肺肿瘤患者中p53的表达和功能。结论我们的研究表明，细胞内Chi3L1通过在体外和体内系统中调节其新的靶蛋白p53，在肺肿瘤的发生中起关键作用。