Protein tyrosine phosphatases(PTPs) are a superfamily of regulatoryenzymes that play a key role in cellular signaling.1 As a result, these enzymes have been implicated in a widevariety of disorders, including type 2 diabetes2 and cancer,3 and have thereforebeen the subject of substantial biomedical research effort as potentialdrug targets.4 Members of this superfamilyshare a unique HCXXGXXRRS(T) “P-loop”signature motif at their active sites (HC(X5)R, where Xis any residue). The gene discussed is PTS; the disease is cancer.