Correlation of long interspersed element-1 open reading frame 1 and c-Met proto-oncogene protein expression in ovarian cancer

Background: Hypomethylation of long interspersed nuclear element-1 (LINE-1) is closely related to certain cancers and concerns with aggressive tumor behavior. Previously, we reported LINE-1 open reading frame-1 (ORF1) protein level was significantly up-regulated in ovarian cancers compared with normal ovary. Hypomethylation of local LINE-1 sequence has been reported to reactivate MET proto-oncogene in colon cancers and hepatocellular carcinoma. However, the relationship between LINE-1 and c-MET expressions in ovarian cancer is not yet studied. Method: Here, we analyzed the expression patterns of LINE-1 ORF1 and c-Met protein in ovarian cancer tissue microarrays containing 208 surgical specimens including normal ovary and malignant ovarian cancers. Results: The expressions of both LINE-1 ORF1 and c-Met protein were significantly increased in ovarian cancers and peaked in early stage of tumor. Other clinical data including age and tumor types were not significantly related with both proteins. Co-relationship between LINE-1 ORF1 and c-Met protein was significant (p = 0.03) but several patients show different expression patterns. Conclusions: These results propose that LINE-1 ORF1 significantly activates c-Met but not in all cases, suggesting other factors may be involved simultaneously.