Knockdown of PKR expression by RNAi reduces pulmonary metastatic potential of B16-F10 melanoma cells in mice: possible role of NF-kappaB.

It was suggested that PKR may act as a tumor suppressor. However, the results are still controversial. Here, we investigate the effect of PKR-specific short hairpin RNA (shRNA) expressing plasmids on pulmonary metastatic potential of B16-F10 melanoma cells in mice. Levels of both PKR mRNA and PKR protein were only significantly reduced in tumor cells transfected with plasmid-based PKR-specific shRNA. Injection of tumor cells transfected with PKR-specific shRNA expressing plasmid resulted in inhibition (85%) of metastatic nodules compared with control. Our results suggest that this effect is mediated by the transcription factor NF-kappaB. This study does not support the concept of PKR as a tumor suppressor.