hZIP1 Inhibits Progression of Clear Cell Renal Cell Carcinoma by Suppressing NF-kB/HIF-1α Pathway

Purpose: Accumulating literature has suggested that hZIP1 and HIF-1 alpha play vital roles in the tumor process of clear cell renal cell carcinoma (ccRCC). However, the functional roles of hZIP1 and HIF-1 alpha in ccRCC remain largely unknown. Methods: HIF-1 alpha protein level was evaluated by a western blot in ccRCC tissues and cell lines. ccRCC cell lines were transfected with HIF-1 alpha-siRNA to downregulate the expression level of HIF-1 alpha. Then the proliferative, migratory and invasive abilities of ccRCC cells in vitro were detected by real-time cell analysis (RTCA) assay, wound healing assay and transwell assay, respectively. The role of HIF-1 alpha in vivo was explored by tumor implantation in nude mice. Then the effect on glycolysis-related proteins was performed by western blot after hZIP1 knockdown (overexpression) or HIF-1 alpha knockdown. The effect on NF-kB pathway was detected after hZIP1 overexpression. Results: HIF-1 alpha was markedly downregulated in ccRCC tissues compared with normal areas. But HIF-1 alpha presented almost no expression in HK-2 and ACHN cells. Immunofluorescence indicated HIF-1 alpha and PDK1 expression in both the cytoplasm and nucleus in ccRCC cells. Downregulation of HIF-1 alpha suppressed ccRCC cell proliferation, migration, and invasion and resulted in smaller implanted tumors in nude mice. Furthermore, hZIP1 knockdown elevated HIF-1 alpha protein levels and PDK1 protein levels in ccRCC cells. Interestingly, a sharp downregulated expression of HIF-1 alpha was observed after hZIP1 overexpression in OSRC-2 and 786-O cells, which resulted from a downtrend of NF-kB1 moving into the cell nucleus. Conclusion: Our work has vital implications that hZIP1 suppresses ccRCC progression by inhibiting NF-kB/HIF-1 alpha pathway.

Automated summary

The study reveals that HIF-1α is downregulated in ccRCC, inhibiting cell proliferation, migration, and invasion, which has important biological implications.