IGFBP-6經由調控EGR-1的表現在鼻咽癌細胞中扮演抑癌基因的角色

Abstract

Nasopharyngeal carcinoma (NPC) is prevalent in southeastern Asia, particularly southern China, Singapore and Taiwan. The aim of this study was to identify the pivotal genes that may be altered during NPC progression. Using cDNA microarray analysis, we compared the expression of 18 genes between NPC and normal nasomucosal cells. Q-RT-PCR analysis found the expression of IBFBP-6 in NPC cell lines and immunolocalization of IGFBP-6 in NPC to be very weak. To explore the effects of IGFBP-6 on NPC tumour growth, we constructed inducible plasmids containing full length of IGFBP-6 c-DNA (pBIG2i-IGFBP-6) and established pBIG2i-IGFBP-6 transfected NPC stable cell lines (NPC-TW01-pBIG2i-IGFBP-6). We then performed functional analysis of the IGFBP-6 in cell lines in vitro and in vivo. Overexpression of IGFBP-6 significantly suppressed the proliferation, invasion, and metastatic activity of NPC cells and increased their apoptosis. We found EGR-1, caspase-1 and TSP-1 genes to be markedly upregulated when NPC-pBIG2i-IGFBP-6 was treated with doxycycline. Knocking down EGR-1 with EGR-1 siRNA resulted in a decrease in expression of caspase-1, TSP-1 and EGR-1, but not the expression of IGFBP-6. However, in knockdown cells the unchanged expression of IGFBP-6 did not inhibit the migration of NPC cells. Chromatin immunoprecipitation and luciferase reporter assay experiments showed that IGFBP-6 bound the EGR-1 promoter regions and activated EGR-1 promoter. We conclude that IGFBP-6 can regulate the progression of NPC by regulating the expression of EGR-1. These results suggest that IGFBP-6 could be used as a new target in NPC therapy.