肿瘤干细胞生物学（赵旭东）知识库

Lung cancer is the most frequent cancer type and the leading cause of tumor-associated deaths worldwide.TP53 is an important tumor suppressor gene and is frequently inactivated in lung cancer. E3 ligases targetingp53, such as MDM2, are involved in the development of lung cancer. The E3 ligase HUWE1, which targets manytumor-associated proteins including p53, has been reported to be highly expressed in lung cancer; however, itsrole in lung tumorigenesis is unclear.

Methods: The expression of HUWE1 and p53 in lung cancer cells was modulated and the phenotypes wereassessed by performing soft agar colony forming assays, cell cycle analysis, BrdU incorporation assays, andxenograft tumor growth assays. The effect on tumorigenesis in genetically-engineered mice was also analyzed.The mechanism through which HUWE1 sustained lung cancer cell malignancy was confirmed by westernblotting. HUWE1 expression in clinical lung cancer was identified by immunohistochemistry and validated byanalyzing lung adenocarcinoma and lung squamous carcinoma samples from the Cancer Genome Atlas (TCGA)database. Finally, we assessed the association between HUWE1 expression and patient outcome using onlinesurvival analysis software including survival information from the caBIG, GEO, and TCGA database.

Results: Inactivation of HUWE1 in a human lung cancer cell line inhibited proliferation, colony-formingcapacity, and tumorigenicity. Mechanistically, this phenotype was driven by increased p53, which was due toattenuated proteasomal degradation by HUWE1. Up-regulation of p53 inhibited cancer cell malignancy, mainlythrough the induction of p21 expression and the down-regulation of HIF1α. Huwe1 deletion completelyabolished the development of EGFRVIII-induced lung cancer in Huwe1 conditional knockout mice.Furthermore, survival analysis of lung cancer patients showed that increased HUWE1 expression is significantlyassociated with worse prognosis.

Conclusion: Our data suggest that HUWE1 plays a critical role in lung cancer and that the HUWE1-p53 axismight be a potential target for lung cancer therapy.