Abstract
Metallopanstimulin‐1 (MPS‐1) is a multifunctional ribosomal protein RPS27 that contains a zinc finger domain of the C~4~ type. MPS‐1 has been found to be increased in the sera of a number of different cancers, including head and neck squamous cell carcinoma (HNSCC). However, little is known about the effect of a high‐level MPS‐1 in regulating cancer cell behavior. In this study, we overexpressed MPS‐1 protein in the HNSCC cell line UMSCC‐1. We found MPS‐1 distributes not only in the cytosol, but also in the nuclei. In addition, MPS‐1 is secreted into the culture medium. In vitro and in vivo experiments show that growth of UMSCC‐1 cells transfected with MPS‐1 is dramatically inhibited. Moreover, we also found that with overexpressing MPS‐1, UMSCC‐1 cells were arrested on G0/G1 phase, cell proliferation rate was reduced, and tumor angiogenesis was impaired. Further gene array analysis, immunohistochemistry staining and Western blotting reveal that MPS‐1 reduces paxillin mRNA and protein levels in UMSCC‐1 cells both in vitro and in vivo. Together, these data indicate that when MPS‐1 is overexpressed, it has an extraribosomal function as a strong inhibitor of HNSCC tumor cell growth, which may be exerted by reduced paxillin gene expression.