Sodium thiophosphate (or sodium monothiophosphate) a biochemical reagent, a specific inhibitor of protein tyrosine phosphatase and a competitive inhibitor of alkaline phosphatase. Thiophosphate was effective in inducing apoptosis in some leukemia cell lines including CEM and K562 and a lymphoma cell line, Raji. In addition, monothiophosphate entered intracellular nucleotide pools and served as an effective precursor for the phosphorylation of nuclear proteins in vivo.