Background: Lung cancer is one of the most common carcinomas worldwide. Cigarette smoking is considered as the leading cause of lung cancer. The aberrant expression of several YTH family proteins has been reported to be closely associated with several cancers. This study aims to evaluate the expression profile and function of YTHDC2, an RNA m6 A methylation reader protein, by in vitro and animal experiments and bioinformatics analysis.
Methods: The expression of YTHDC2 gene and protein was analyzed by the GEPIA online tool and Gene Expression Omnibus (GEO) database, as well as immunohistochemistry of tissue arrays. The YTHDC2 expression in cigarette smoke-exposed cells was examined by RT-qPCR and western blot assays. The TCGA datasets and proteomic analysis of YTHDC2 knockdown cells were used to predict the clinical significance and biological function of YTHDC2. Functional assays, including wound healing, transwell migration, cell cycle and cell proliferation, were used to determine the biological role of YTHDC2 in lung cancer. The xenograft animal model further validated the tumor suppressor effect of YTHDC2 in vivo. The copy number variation of YTHDC2 was analyzed by TCGA datasets and TaqMan copy number assay.
Results: YTHDC2 was significantly low-expressed in lung cancer and cigarette smoke-exposed cells. Notably, decreased YTHDC2 was found highly associated with smoking history, pathological stage, invasion depth, and lymph node metastasis, as well as poor outcomes. The YTHDC2 related genes and proteins were enriched in several cancer-related pathways, and several tumor suppressor genes were found positively correlated with YTHDC2. The in vivo and in vitro study revealed that overexpression of YTHDC2 inhibited the proliferation and migration ability of lung cancer cells, as well as the tumor growth in nude mice. Besides, a significant positive correlation between the copy number and expression level of YTHDC2 was found in lung cancer.
Conclusions: Our results indicated that the smoking-related down-regulation of YTHDC2 was associated with enhanced proliferation and migration of lung cancer cells and appeared to be regulated by DNA copy number variation. Importantly, YTHDC2 may serve as a tumor suppressor gene and a favorable prognostic indicator in lung cancer patients.