The Tumor-Suppressive Function ofUNC5Dand Its Repressed Expression in Renal Cell Carcinoma

Abstract

Purpose: As a newly added member of the UNC5H receptors, the function of UNC5D/H4 in tumorigenesis remains poorly defined. The aim of this study was to examine the expression of UNC5D in primary renal cell carcinomas (RCC), analyze the mechanisms responsible for its downregulation in RCC, and assess its functional relevance to tumor growth and migration.Experimental Design: Forty-four paired primary RCCs and corresponding adjacent noncancerous tissues were collected. The mRNA and protein expression level of UNC5D was assessed by reverse transcriptase-PCR, real-time PCR, or immunohistochemistry. Epigenetic alterations in UNC5D promoter and LOH in the UNC5D locus were also analyzed. Ectopic expression of UNC5D in renal cancer cells with silenced expression of UNC5D was used for analysis of the biologic functions of UNC5D.Results: UNC5D expression was attenuated in multiple carcinoma cell lines including renal cancer cells. Similar reduction was also observed in primary RCC tissues as compared with paired adjacent noncancerous tissues. Methylation-specific PCR showed hypermethylation in UNC5D promoter in a significant proportion (18 of 44) of tumor tissue (40.9%). LOH of UNC5D was observed in 13 of 44 patients with RCCs (29.5%). Restoration of UNC5D expression in renal cancer cells significantly inhibited cell proliferation, anchorage-dependent and -independent growth, as well as migration and invasion, whereas knockdown of UNC5D promoted cell growth. Furthermore, ectopic expression of UNC5D induced G 2 -M cell-cycle arrest.Conclusions: UNC5D is a functional tumor suppressor that is frequently downregulated in RCCs due to promoter hypermethylation and LOH.

Overexpression of UNC5B in bladder cancer cells inhibits proliferation and reduces the volume of transplantation tumors in nude mice

“…The two cell lines resulted in the formation of tumors of different sizes on the back of mice and lethality at 32 days to 47 days after injection. UNC5D overexpression has been suggested to inhibit cell multiplication, migration and invasion in renal cancer cells by inducing cell cycle arrest at G2/M phase [12]. These data indicated that UNC5D may act as a tumor suppressor and are consistent with our findings in bladder cancer cells.…”

UNC5D, suppressed by promoter hypermethylation, inhibits cell metastasis by activating death‐associated protein kinase 1 in prostate cancer

“…Epigenetic changes are common features of PCa, and play key roles in the initiation and progression of cancer . As for UNC5D , hypermethylation alterations at the promoter region are one of the main causes for its repression in a variety of tumors, and are the same in PCa cells according to our study. However, there are seldom reports on the methylation status of UNC5D in metastatic tumors.…”

“…Adenoviruses expressing UNC5D , UNC5D‐∆DD (UNC5D without the death domain), or MOCK were packaged by the Vector Gene Technology Company (Beijing, China). Prostate cancer cell lines were infected with 20 MOI of the adenoviral vector.…”

“…Like other members of this family, UNC5D has also been characterized as a tumor suppressor gene in several cancers, such as neuroblastoma, renal cell carcinoma, and bladder cancer . UNC5D has been observed with high expression in the human prostate tissue, but underexpressed in the castration‐resistant stage of prostate cancer . However, little is known about the role and underlying mechanism of UNC5D in prostate cancer pathogenesis and progression.…”

“…10,12,13 UNC5D/H4 is the most recently identified member of UNC5 family. 14 Like other members of this family, UNC5D has also been characterized as a tumor suppressor gene in several cancers, such as neuroblastoma, 15,16 renal cell carcinoma, 17 and bladder cancer. 18…”