Downregulation of phospho-tyrosine phosphatases in a macrophage tumor

AbstractWe provide evidence for the downregulation of phospho-tyrosine phosphatases (PTPases) in malignancy. AK-5, a rat macrophage tumor, shows the downregulation of the transcripts of two non-receptor-type PTPases, PTP-1 and PTP-S. Though downregulated fourfold, the genomic organization of PTP-S is unaltered. There is no gross alteration of the PTPase activity in AK-5 as compared to macrophages. Immunoblot analysis reveals no significant change in the total phospho-tyrosine levels in AK-5, but there is a qualitative difference in the pattern between AK-5 and macrophages. Our results lend credence to the conjecture that PTPases also might be involved in malignancy