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

Abstract

PurposeAccumulating literature has suggested that hZIP1 and HIF-1α play vital roles in the tumor process of clear cell renal cell carcinoma (ccRCC). However, the functional roles of hZIP1 and HIF-1α in ccRCC remain largely unknown.MethodsHIF-1α protein level was evaluated by a western blot in ccRCC tissues and cell lines. ccRCC cell lines were transfected with HIF-1α-siRNA to downregulate the expression level of HIF-1α. 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-1α 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-1α knockdown. The effect on NF‐kB pathway was detected after hZIP1 overexpression.ResultsHIF-1α was markedly downregulated in ccRCC tissues compared with normal areas. But HIF-1α presented almost no expression in HK-2 and ACHN cells. Immunofluorescence indicated HIF-1α and PDK1 expression in both the cytoplasm and nucleus in ccRCC cells. Downregulation of HIF-1α suppressed ccRCC cell proliferation, migration, and invasion and resulted in smaller implanted tumors in nude mice. Furthermore, hZIP1 knockdown elevated HIF-1α protein levels and PDK1 protein levels in ccRCC cells. Interestingly, a sharp downregulated expression of HIF-1α 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.ConclusionOur work has vital implications that hZIP1 suppresses ccRCC progression by inhibiting NF-kB/HIF-1α pathway.

FBXO30 functions as a tumor suppressor and an E3 ubiquitin ligase for hZIP1‑mediated HIF‑1α degradation in renal cell carcinoma

“…In conclusion, FBXO30 may be a novel E3 ubiquitin ligase for HIF-1α that is involved in ccRCC progression. We also verified the findings of our previous study that hZIP1 inhibits HIF-1α protein expression ( 28 ). In addition, hZIP1 may be upstream of FBXO30, promoting the downregulation of HIF-1α via FBXO30.…”

“…ccRCC is a solid tumor characterized by hypoxia, which is possibly caused by long-term elevated oxygen consumption and decreased oxygen diffusion due to the irregular distribution of the vasculature system in tumors ( 33 - 35 ). However, our previous studies confirmed that even without oxygen content changes in the tumor extracellular microenvironment, HIF-1α, which is supposed to be degraded via pVHL-mediated ubiquitination, remained highly expressed in cultured ccRCC cell lines under normoxia ( 8 , 28 ). Consistently, previous studies have suggested that pVHL is frequently mutated and inactivated during the development of ccRCC ( 19 , 33 ).…”

“…HIF-1α is thought to enhance the invasiveness of ccRCC cells by promoting glycolysis and preventing tumor cells from undergoing apoptosis ( 36 - 38 ). Based on our previous results, HIF-1α has also been reported to act as an oncogene in ccRCC ( 28 ). In the present study, FBXO30 reduced the upregulation of HIF-1α protein expression in ccRCC cells under normoxia without affecting its mRNA levels, which could be due to post-translational regulation.…”

“…Zn 2+ is an important microelement that is involved in multiple metabolic processes, such as sugar and lipid metabolism ( 26 ). Our previous studies indicated that hZIP1 was downregulated in ccRCC tissues and that it inhibited tumor progression by downregulating HIF-1α ( 27 , 28 ). However, the specific mechanism through which hZIP1 decreases HIF-1α and the role of Zn 2+ remain unknown.…”

Establishment of a new prognostic risk model of MAPK pathway-related molecules in kidney renal clear cell carcinoma based on genomes and transcriptomes analysis

“…The present study demonstrated that NFKB1 mRNA was highly expressed in ccRCC. A related study confirmed that the expression of HIF-1a decreased dramatically in ccRCC cells due to the reduced movement of NF-kB1 to the nucleus, which also inhibited the progression of ccRCC (28). The above results also confirm that the decreased expression of NFKB1 in ccRCC may be associated with the inhibition of tumor progression.…”