Insulin‐like growth factor binding protein‐related protein 1 (IGFBP‐rP1) has potential tumour‐suppressive activity in human lung cancer

Abstract

The expression of insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) is decreased in various tumours, but the role of IGFBP-rP1 in lung cancer is not yet clear. In this study, IGFBP-rP1 expression in lung cancer cell lines was evaluated and reduced expression of IGFBP-rP1 was found. In tissue microarrays containing 138 primary tumours and 20 normal lung tissues analysed by immunohistochemistry, 58 tumours (42%) exhibited no expression of IGFBP-rP1, while all 20 normal lung tissues showed high expression. In squamous cell lung cancer, low expression of IGFBP-rP1 was significantly linked to high-grade tumours. Treatment with 5-aza-2'-deoxycytidine restored the expression of IGFBP-rP1 in three of four lung cancer cell lines. Sequencing of PCR products of sodium bisulphite-treated genomic DNA from the three lung cancer cell lines revealed a heterogeneous methylation pattern in the region of exon 1 and intron 1. Stable transfection of IGFBP-rP1 full-length cDNA into the H2170 lung cancer cell line led to increased expression of IGFBP-rP1 protein. IGFBP-rP1-positive transfectants exhibited remarkably reduced colony-forming ability in soft agar, suppression of tumour growth rate in nude mice, and increased apoptotic cell number as well as activated caspase-3 expression level. The data suggest that IGFBP-rP1 is a tumour suppressor inactivated by DNA methylation in human lung cancer.

Glioblastoma-secreted factors induce IGFBP7 and angiogenesis by modulating Smad-2-dependent TGF-β signaling

“…In contrast to colon (Lin et al, 2007) and lung (Chen et al, 2007) IGFBP7-negative cancer cell lines in which sites þ 490 to þ 610 of the 5 0 CpG island of IGFBP7 gene were all methylated, neither these sites ( þ 490 to þ 610) nor promoter regions of IGFBP7 were highly methylated in either control or U87MG-CM-treated HBEC. These results suggest that IGFBP7 gene regulation by DNA methylation is likely different between cancer cells and endothelial cells, and that DNA demethylation was not involved in regulating IGFBP7 gene induction in HBEC.…”

“…Compelling literature evidence indicates that hypermethylation of CpG islands of IGFBP7 is responsible for downregulation of IGFBP7 in tumor cells contributing to tumor progression (Komatsu et al, 2000;Chen et al, 2007;Lin et al, 2007). In contrast to colon (Lin et al, 2007) and lung (Chen et al, 2007) IGFBP7-negative cancer cell lines in which sites þ 490 to þ 610 of the 5 0 CpG island of IGFBP7 gene were all methylated, neither these sites ( þ 490 to þ 610) nor promoter regions of IGFBP7 were highly methylated in either control or U87MG-CM-treated HBEC.…”

“…IGFBP7 gene methylation in HBEC is not affected by glioblastoma-conditioned media To investigate whether IGFBP7 induction in HBEC treated with U87MG-CM was the result of DNA demethylation, the methylation status of IGFBP7 gene in HBEC treated with either Dulbecco's modified Eagle's medium (DMEM; control) or U87MG-CM was analysed (as described in Supplementary Materials and Methods; Miller et al, 1998;Deb-Rinker et al, 2005) using primer sets (Supplementary Table 1) designed to amplify cytosine-phosphate-guanine (CpG) sites present in the promoter region (primer sets A and B) or exon 1 and exon 1/intron 1 (primer sets C and D, respectively) of IGFBP7 gene (Chen et al, 2007). The methylation status of DMEM-and U87MG-CM-treated HBEC in the exon 1 region ( þ 73 to þ 472; primer pair IGFBP7-C) of IGFBP7 spanning 45 CpG sites could not be determined, possibly due to the high density of CpG islands present in this region resulting in unspecific PCR products.…”

IGFBP7: an oncosuppressor gene in thyroid carcinogenesis

“…IGFBP7 has also IGF/ insulin-independent actions. A large body of evidence suggests that IGFBP7 functions as an oncosuppressor gene in human prostate, breast, lung and colorectal cancer, as it regulates cell proliferation, cell adhesion, cellular senescence and angiogenesis (Akaogi et al, 1996;Sprenger et al, 1999;Wilson et al, 2002;Burger et al, 2005;Ruan et al, 2006;Chen et al, 2007;Sato et al, 2007). IGFBP7 is silenced by promoter hypermethylation in several neoplastic tissues, including colorectal and gastric cancers (Kanemitsu et al, 2000;Ahmed et al, 2003;Lin et al, 2007).…”

Insulin-Like-Growth Factor-Binding-Protein 7: An Antagonist to Breast Cancer

“…Expression of IGFBP7 in lung cancer cell lines using RT-PCR revealed decreased expression of IGFBP7 compared to controls, and 42 out of 90 patients with primary lung tumors exhibited negative staining of IGFBP7 by immunohistochemical analysis [118]. There was a significant correlation between DNA methylation of exon/intron 1 region and IGFBP7 downregulation.…”