On the role of tyrosine phosphatases as negative regulators of STAT signaling in breast cancers: new findings and future perspectives.

The increasing importance of signal transducer and activator of transcription 3 (STAT3) expression in human cancers has led several laboratories to examine in detail the expression of one of its major negative regulators in oncogenesis--the T-cell protein tyrosine phosphatase, nonreceptor type 2 (PTPN2). A recent paper by Shields and colleagues points to the associate depletion of PTPN2 in STAT3-positive breast cancers. We examine these findings and reflect on the mechanism of action of PTPN2 and the consequences of its modulation for STAT3 downstream signaling.