Assessing Cellular Target Engagement by SHP2 (PTPN11) Phosphatase Inhibitors

The Src-homology 2 (SH2) domain-containing phosphatase 2 (SHP2), encoded by the PTPN11 proto-oncogene, is a key mediator of receptor tyrosine kinase (RTK)-driven cell signaling, promoting cell survival and proliferation. In addition, SHP2 is recruited by immune check point receptors to inhibit B and T cell activation. Aberrant SHP2 function has been implicated in the development, progression, and metastasis of many cancers. Indeed, small molecule SHP2 inhibitors have recently entered clinical trials for the treatment of solid tumors with Ras/Raf/ERK pathway activation, including tumors with some oncogenic Ras mutations. However, the current class of SHP2 inhibitors is not effective against the SHP2 oncogenic variants that occur frequently in leukemias, and the development of specific small molecules that target oncogenic SHP2 is the subject of current research. A common problem with most drug discovery campaigns involving cytosolic proteins like SHP2 is that the primary assays that drive chemical discovery are often in vitro assays that do not report the cellular target engagement of candidate compounds. To provide a platform for measuring cellular target engagement, we developed both wild-type and mutant SHP2 cellular thermal shift assays. These assays reliably detect target engagement of SHP2 inhibitors in cells. Here, we provide a comprehensive protocol of this assay, which provides a valuable tool for the assessment and characterization of SHP2 inhibitors.