Metallopanstimulin-1 (MPS-1) is a multifunctional ribosomal protein. MPS-1 is a 10 kD zinc finger protein (ZFP) that is present in all tissues and expressed in increased quantities in a wide variety of proliferating tissues and malignancies. The ribosome is a ribonucleoprotein complex of ribosomal RNAs (rRNA) and proteins (r-protein). Conventionally, r-proteins are thought to be responsible for new protein synthesis, but emerging evidence has shown activity exists beyond this. Some extra-ribosomal functions of r-proteins have been observed in close relation to cancer pathology. MPS-1 is over-expressed in the serum and tissue of dozens of malignancies. However, it is unknown whether the enhanced expression of MPS-1 is the cause or result of tumor development and progression. Our preliminary observations show increased MPS-1 decreases paxillin. Recently, paxillin was found to have an important role in regulating both normal and tumor cell proliferation. Elevation of MPS-1 in HNSCC samples and its structure/function as a ribosomal ZFP have led us to conclude that MPS-1 might be a subject of interest for malignant tumor therapy. Our data reveal that enhanced expression of MPS-1 protein can strongly suppress tumor cell proliferation. MPS-1 and significantly inhibits tumor growth both in vitro and in vivo in 3 distinct malignant cell lines. We have concluded that over-expression of MPS-1 might be used therapeutically in the treatment of some malignancies.