A number of currently available cancer drugs may kill tumor cells by activating SHP-1, leading to inhibition of STAT3 and cell death by apoptosis.8 Conversely, immunotherapies have focused on ablation of SHP-1 to counter its inhibitory action on cytotoxic T cells.9 The clinically available active-site SHP-1 inhibitor sodium stibogluconate, which also targets the related phosphatase SHP-2, is currently being investigated as a potential cancer therapeutic.10 A number of other small molecule protein tyrosine phosphatase inhibitors are being investigated as cancer therapeutics. Here, STAT3 is linked to cancer.