Background: Carcinoma of the esophagus has a high case fatality ratio and is now the 6th most common cause of cancer deaths in the world. We previously conducted a study to profile the expression of miRNAs in esophageal adenocarcinoma (EAC) pre and post induction therapy. Of the miRNAs differentially expressed post induction chemoradiation, miR-145, a known tumor suppressor miRNA, was upregulated 8-fold following induction therapy, however, its expression was associated with shorter disease-free survival. This unexpected result was explored in this current study.
Methods: In order to study the role of miR-145 in EAC, miRNA-145 was overexpressed in 3 EAC cell lines (OE33, FLO-1, SK-GT-4) and one ESCC cell line (KYSE-410). After validation of the expression of miR-145, hallmarks of cancer such as cell proliferation, resistance to chemotherapy drugs or anoikis, and cell invasion were analyzed.
Results: There were no differences in cell proliferation and 5 FU resistance between miR145 cell lines and the control cell lines. miR-145 expression also had no effect on cisplatin resistance in two of three cell lines (OE33 and FLO-1), but miR-145 appeared to protect SK-GT-4 cells against cisplatin treatment. However, there was a significant difference in cell invasion, cell adhesion and resistance to anoikis. All three EAC miR-145 cell lines invaded more than their respective controls. Similarly, OE33 and SK-GT-4 miR-145 cell lines were able to survive longer in a suspension state.
Discussion: While expression of miR-145 in ESCC stopped proliferation and invasion, expression of miR-145 in EAC cells enhanced invasion and anoikis resistance. Although more work is required to understand how miR-145 conveys these effects, expression of miR-145 appears to promote EAC progression by enhancing invasion and protection against anoikis, which could in turn facilitate distant metastasis.