Fibulin-1 is down-regulated through promoter hypermethylation and suppresses renal cell carcinoma progression

Purpose: Renal cell carcinoma is one of the most common cancers worldwide but the molecular mechanisms that underlie it are not fully understood. Fibulin-1, a multi-functional extracellular matrix protein, is involved in many types of cancer but its function in renal cell carcinoma is unclear. We investigated fibulin-1 expression and function in renal cell carcinoma. Materials and Methods: We performed real-time polymerase chain reaction, Western blot analysis and immunohistochemistry to determine fibulin-1 expression in renal cell carcinoma cells and patient tissues. Methylation specific polymerase chain reaction and quantitative sequencing were done to examine the methylation status of the FBLN1 gene promoter. Eukaryotic expression plasmid and a lentiviral vector were used to over express fibulin-1 in ACHN and 786-O renal cell carcinoma cells to investigate its function in vitro and in vivo. Results: Fibulin-1 was significantly down-regulated in renal cell carcinoma cell lines and patient tissues. Dysregulation was associated with renal cell carcinoma progression. The FBLN1 gene promoter region was hypermethylated and its methylation status correlated with fibulin-1 expression. Fibulin-1 over expression led dramatically to decreased cell growth, enhanced tumor cell apoptosis, decreased cell motility and angiogenesis in cultured renal cell carcinoma cells and in xenograft tumors in nude mice. Conclusions: Fibulin-1 is down-regulated in renal cell carcinoma through promoter hypermethylation. It functions as a tumor suppressor and angiogenesis inhibitor in renal cell carcinoma.