Identification of novel VHL targets that are associated with the development of renal cell carcinoma

Abstract

von Hippel-Lindau (VHL) disease is a dominantly inherited family cancer syndrome characterized by the development of retinal and central nervous system haemangioblastomas, renal cell carcinoma (RCC) and phaeochromocytoma. Specific germline VHL mutations may predispose to haemangioblastomas, RCC and phaeochromocytoma to a varying extent. Although dysregulation of the hypoxia-inducible transcription factor-2 and JunB have been linked to the development of RCC and phaeochromocytoma, respectively, the precise basis for genotype-phenotype correlations in VHL disease have not been defined. To gain insights into the pathogenesis of RCC in VHL disease we compared gene expression microarray profiles in a RCC cell line expressing a Type 1 or Type 2B mutant pVHL (RCC-associated) to those of a Type 2A or 2C mutant (not associated with RCC). We identified 19 differentially expressed novel VHL target genes linked to RCC development. Eight targets were studied in detail by quantitative real-time polymerase chain reaction (three downregulated and five upregulated by wild-type VHL) and for six genes the effect of VHL inactivation was mimicked by hypoxia (but hypoxicinduction of smooth muscle alpha-actin 2 was specific for a RCC cell line). The potential role of four RCCassociated VHL target genes was assessed in vitro. NB thymosin beta (TMSNB) and proteinase-activated receptor 2 (PAR2) (both downregulated by wt pVHL) increased cell growth and motility in a RCC cell line, but aldehyde dehydrogenase (ALDH)1 and ALDH7 had no effect. These findings implicate TMSNB and PAR2 candidate oncogenes in the pathogenesis of VHL-associated RCC.

Renal cell carcinoma

“…Gene expression also separated chromophobe RCC from oncocytoma [44] and characterized molecular classes within papillary RCC [45]. Expression array studies have also been used to discover novel VHL target genes in cell lines [46, 47] and identify molecular pathways deregulated in RCC [48]. Differences in tumor sets, array platforms, analysis of data sets and the extent of validation, typically immunohistochemical analysis of several genes, should be noted.…”

The TRC8 Ubiquitin Ligase Is Sterol Regulated and Interacts with Lipid and Protein Biosynthetic Pathways

“…In fission yeast, SREBP activation occurs in response to hypoxia (32), although a similar response has not been described in mammalian cells. However, INSIG-2 is hypoxia regulated (33). Given the apparent disruption of lipid homeostatis in clear-cell RCC, this raises the question of whether other regulatory components of the SREBP pathway might be affected in the disease process.…”

Differential regulation of human thymosin beta 15 isoforms by transforming growth factor beta 1

“…Thymosin beta 15 affects cell colony growth, transformation and cell migration (Bao et al, 1996; Abdulrahman et al, 2007; Dhaese et al, 2007) and a key regulator of cell growth in the tumor microenvironment is transforming growth factor beta 1 (TGFB1). We therefore examined thymosin beta 15 expression in response to TGFB1 treatment.…”

“…The human TMSB15A isoform has previously been established as a functional protein. TMSB15A expression increases mouse fibroblast migration (Dhaese et al, 2007), increases human tumor cell colony formation and anchorage-independent growth, and is required for colony formation (Abdulrahman et al, 2007). To determine whether TMSB15B protein is expressed and functional, we used RNA interference followed by a cell migration assay.…”

“…Increasing thymosin beta 15 level may confer advantage to tumor cells by increasing motility, transformation and colony formation (Bao et al, 1996; Abdulrahman et al, 2007; Dhaese et al, 2007). We note that several human cancer cell lines expressed both TMSB15A and TMSB15B isoforms.…”