Rapid inhibition of MAPK signaling and anti-proliferation effect via JAK/STAT signaling by interferon-α in hepatocellular carcinoma cell lines

The potential anti-proliferation effect of interferon-alpha (IFN-α) against hepatocellular carcinoma (HCC) and its growth inhibitory mechanisms remain unclear. We examined four human HCC cell lines and every cell line had the anti-proliferative effect of IFN-α. The PLC/PRF/5 cell line, which expressed the IFN receptor most abundantly, responded most effectively to IFN-α stimulation. Here, we delineate the anti-proliferative effect of IFN-α via the MAPK pathway in human HCC cell lines. IFN-α retarded G1/S transition with no evidence of apoptosis and inhibited cell proliferation. IFN-α diminished the phosphorylation of both extracellular signal-regulated kinase (ERK) and mitogen-activated ERK-regulating kinase (MEK), but not Raf, within 5 min. Knockdown of signal transducers of activation and transcription1 (STAT1) or Janus kinase1 (JAK1) suppressed the reduction of phosphorylation both of ERK and MEK and diminished the growth inhibition by IFN-α. These results suggest that IFN-α induces anti-proliferative signaling via the JAK/STAT pathway downstream of IFN-α receptors and may reduce the growth stimulation signaling by cross-talk with the MEK/ERK pathway without IFN-α-induced transcription.