Presentation Authors: Yanqing Gong*, Yifan Li, BEIJING, China, People's Republic of, Xianghui Ning, HENAN, China, People's Republic of, Xuesong Li, Kan Gong, Liqun Zhou, BEIJING, China, People's Republic of
Introduction: Metastasis is the primary cause of death in renal cell carcinoma (RCC). Loss of cell-to-cell adhesion, including tight junctions (TJs) is the initial step in the process of metastasis. Claudin-7 (CLDN7) is a major component of TJs. However, the clinical significance and its regulation of kidney tumorigenesis remain poorly understood.
Methods: Total 120 fresh ccRCC specimen and 144 primary RCC and adjacent non-malignant renal paraffin specimen were obtained from Peking University First Hospital. Expression of CLDN7 in ccRCC were determined by bioinformatic data mining, qRT-PCR, Western blot and immunostaining. The clinical significance of CLDN7 expression and promoter methylation status was analyzed in ccRCC patients. The methylation specific-PCR, bisulfite genomic sequencing and demethylation analysis of CLDN7 were performed in ccRCC. Biological functions of lentivirus-mediated CLDN7 overexpression on ccRCC cells proliferation, migration and invasion were investigated. Mice experiments were performed to confirm effects of CLDN7 on tumor growth and metastasis in vivo. Molecular mechanism of CLDN7 function was investigated by gene-set enrichment analysis (GSEA) and high-throughput cDNA sequencing (RNA-Seq) and confirmed by qRT-PCR, western blot and immunostaining in vitro and in vivo.
Results: CLDN7 was frequently downregulated via hypermethylation of its promoter in ccRCC. CLDN7 can help predict aggressive tumor status and poor prognosis in ccRCC patients. Hypermethylation of CLDN7 promoter was related to advanced ccRCC and poor prognosis. Moreover, overexpression of CLDN7 induced cell apoptosis, suppressed proliferation, migration and invasion abilities of ccRCC cells both in vitro and in vivo. In addition, GSEA and RNA-Seq results showed high expression of CLDN7 had negative effect in cancer-associated signaling pathways and (epithelial-mesenchymal transition) EMT-related pathways, and results were validated by qRT-PCR, Western blot and immunostaining.
Conclusions: We have demonstrated a previously undescribed role of CLDN7 as a ccRCC suppressor and suggest that loss of CLDN7 potentiates EMT and tumor progression. CLDN7 may serve as a functional tumor suppressor in tumor progression and a potential biomarker and target in patients with ccRCC.