ABSTRACT
HGF/c-MET is frequently associated with tumor metastasis in many cancers, including uveal melanoma (UM). PHA665752, a selective c-MET inhibitor, exhibits anticancer activity through inhibiting cell motility in some cancers. In this study, we investigated the effects of PHA665752 on UM cell lines M17 and SP6.5. Our data show that HGF stimulated the motility of UM cells, and induced the activation of both c-MET and PI3K/AKT, but not ERK1/2. Moreover, consistent with the amount of c-MET within the nucleus, PHA665752 significantly inhibited HGF-promoted cell motility and suppressed the phosphorylation of c-MET and PI3K/AKT, but not ERK1/2 induced by HGF. Additionally, the effects of PHA665752 on both the inhibition of HGF-induced cell motility and the suppression of active AKT are similar to those of PI3K inhibitor LY294002. In xenograft models, PHA665752 significantly inhibited tumor growth in nude mice and similarly suppressed the phosphorylation of c-MET and PI3K/AKT. Our current findings, combined with previous results, demonstrate that PHA665752 inhibits HGF-induced motility via the inhibition of PI3K/AKT. This study suggests that targeting HGF/c-MET could be a promising therapeutic strategy for UM by preventing cell motility.
Subject(s)
Indoles/pharmacology , Melanoma/pathology , Phosphatidylinositol 3-Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction , Sulfones/pharmacology , Uveal Neoplasms/pathology , Animals , Cell Line, Tumor , Cell Movement , Hepatocyte Growth Factor/pharmacology , Humans , Melanoma/drug therapy , Mice , Mice, Nude , Neoplasm Invasiveness , Uveal Neoplasms/drug therapy , Xenograft Model Antitumor AssaysABSTRACT
Promoter CpG methylation of tumour suppressor genes (TSGs) is an epigenetic biomarker for TSG identification and molecular diagnosis. We screened genome wide for novel methylated genes through methylation subtraction of a genetic demethylation model of colon cancer (double knockout of DNMT1 and DNMT3B in HCT116) and identified DLEC1 (Deleted in lung and oesophageal cancer 1), a major 3p22.3 TSG, as one of the methylated targets. We further found that DLEC1 was downregulated or silenced in most colorectal and gastric cell lines due to promoter methylation, whereas broadly expressed in normal tissues including colon and stomach, and unmethylated in expressing cell lines and immortalised normal colon epithelial cells. DLEC1 expression was reactivated through pharmacologic or genetic demethylation, indicating a DNMT1/DNMT3B-mediated methylation silencing. Aberrant methylation was further detected in primary colorectal (10 out of 34, 29%) and gastric tumours (30 out of 89, 34%), but seldom in paired normal colon (0 out of 17) and gastric (1 out of 20, 5%) samples. No correlation between DLEC1 methylation and clinical parameters of gastric cancers was found. Ectopic expression of DLEC1 in silenced HCT116 and MKN45 cells strongly inhibited their clonogenicity. Thus, DLEC1 is a functional tumour suppressor, being frequently silenced by epigenetic mechanism in gastrointestinal tumours.
