Neural epidermal growth factor-like like (NELL) 1 and 2 constitute a family of multimeric and multimodular extracellular glycoproteins. Although the osteogenic effects of NELL1 and functions of NELL2 in neural development have been reported, their expression and functions in cancer are largely unknown. In this study, we examined expression of NELL1 and NELL2 in renal cell carcinoma (RCC) using clinical specimens and cell lines. We show that, whereas NELL1 and NELL2 proteins are strongly expressed in renal tubules in non-cancerous areas of RCC specimens, their expression is significantly downregulated in cancerous areas. Silencing ofNELL1 andNELL2mRNA expression was also detected in RCC cell lines. Analysis ofNELL1/2 promoter methylation status indicated that the CpG islands in theNELL1 andNELL2 genes are hypermethylated in RCC cell lines. NELL1 and NELL2 bind to RCC cells, suggesting that these cells express a receptor for NELL1 and NELL2 that can transduce signals. Furthermore, we found that both NELL1 and NELL2 inhibit RCC cell migration, and NELL1 further inhibits RCC cell adhesion. These results suggest that silencing of NELL gene expression by promoter hypermethylation plays roles in RCC progression by affecting cancer cell behavior.
We found that the down-regulation of NELL1 and NELL2 in renal cell carcinoma (RCC) is in part due to the hypermethylation of CpG islands in their putative promoter regions. Furthermore, we found that NELL1 suppresses and NELL2 partially suppresses RCC cell migration, and NELL1 further inhibits RCC cell adhesion.