PTPN1 (PTP1B) is the founding member of the protein tyrosine phosphatase (PTP) family of proteins, which catalyze the hydrolysis of the phosphate monoesters specifically on tyrosine residues. PTPs are signaling molecules that regulate a variety of cellular processes including cell growth, differentiation, mitotic cycle, and oncogenic transformation. PTPN1 dephosphorylates the EGFR, JAK2 and TYK2 kinases, implicating PTPN1 in cell growth control and cell response to interferon stimulation. PTPN1 has been shown to act as a negative regulator of insulin signaling by dephosphorylating the phosphotryosine residues of insulin receptor kinase. It is also thought to contribute to breast tumorigenesis. Because of this, PTPN1 is a putative therapeutic target for type 2 diabetes and some forms of cancer. References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804; Cancer Res. 67 (6): 2420–4, PMID: 17347513; J. Med. Chem. 53 (6): 2333–44, PMID: 20000419;