MEK Inhibitor Suppresses Expression of the miR-17-92 Cluster with G1-Phase Arrest in HT-29 Human Colon Cancer Cells and MIA PaCa-2 Pancreatic Cancer Cells.

BACKGROUND: MicroRNAs (miRNAs) are small non-coding RNAs, and the deregulated expression of miRNAs is associated with tumor development. Among these, the miR-17-92 cluster, including six mature miRNAs, is known as an oncogenic miRNA cluster because expression of the miR-17-92 cluster is frequently elevated in a variety of malignant tumors.

MATERIALS AND METHODS: We investigated whether a mitogen-activated protein kinase kinase (MEK) inhibitor, PD0325901, suppresses expression of the miR-17-92 cluster in HT-29 human colon cancer cells and MIA PaCa-2 pancreatic cancer cells.

RESULTS: PD0325901 inhibited cell growth with G1-phase arrest and suppressed expression of the miR-17-92 cluster. Furthermore, phosphatase and tensin homolog (PTEN), which is a target molecule of the miR-17-92 cluster, was up-regulated by PD0325901. The exogenous expression of miR-17 slightly, but significantly reduced G1-phase arrest by PD0325901.

CONCLUSION: These results raise the possibility that a MEK inhibitor causes G1-phase arrest, at least partially, through suppression of the miR-17-92 cluster.