ABSTRACT
The non-receptor protein tyrosine phosphatase SHP2, encoded by PTPN11, has an important role in signal transduction downstream of growth factor receptor signalling and was the first reported oncogenic tyrosine phosphatase. Activating mutations of SHP2 have been associated with developmental pathologies such as Noonan syndrome and are found in multiple cancer types, including leukaemia, lung and breast cancer and neuroblastoma. SHP2 is ubiquitously expressed and regulates cell survival and proliferation primarily through activation of the RASERK signalling pathway. It is also a key mediator of the programmed cell death 1 (PD-1) and B- and T-lymphocyte attenuator (BTLA) immune checkpoint pathways. Reduction of SHP2 activity suppresses tumour cell growth and is a potential target of cancer therapy. Here we report the discovery of a highly potent (IC50 = 0.071 µM), selective and orally bioavailable small-molecule SHP2 inhibitor, SHP099, that stabilizes SHP2 in an auto-inhibited conformation. SHP099 concurrently binds to the interface of the N-terminal SH2, C-terminal SH2, and protein tyrosine phosphatase domains, thus inhibiting SHP2 activity through an allosteric mechanism. SHP099 suppresses RASERK signalling to inhibit the proliferation of receptor-tyrosine-kinase-driven human cancer cells in vitro and is efficacious in mouse tumour xenograft models. Together, these data demonstrate that pharmacological inhibition of SHP2 is a valid therapeutic approach for the treatment of cancers.
Subject(s)
Neoplasms/drug therapy , Neoplasms/enzymology , Piperidines/pharmacology , Protein Tyrosine Phosphatase, Non-Receptor Type 11/antagonists & inhibitors , Pyrimidines/pharmacology , Receptor Protein-Tyrosine Kinases/metabolism , Allosteric Regulation/drug effects , Animals , Cell Line, Tumor , Cell Proliferation/drug effects , Extracellular Signal-Regulated MAP Kinases/metabolism , Female , Humans , Inhibitory Concentration 50 , MAP Kinase Signaling System/drug effects , Mice , Mice, Nude , Models, Molecular , Neoplasms/pathology , Oncogene Protein p21(ras)/metabolism , Piperidines/chemistry , Piperidines/therapeutic use , Protein Kinase Inhibitors/pharmacology , Protein Stability/drug effects , Protein Structure, Tertiary/drug effects , Protein Tyrosine Phosphatase, Non-Receptor Type 11/chemistry , Protein Tyrosine Phosphatase, Non-Receptor Type 11/genetics , Protein Tyrosine Phosphatase, Non-Receptor Type 11/metabolism , Pyrimidines/chemistry , Pyrimidines/therapeutic use , Reproducibility of Results , Xenograft Model Antitumor AssaysABSTRACT
Aberrant activation of the Hedgehog (Hh) pathway can drive tumorigenesis. To investigate the mechanism by which glioma-associated oncogene family zinc finger-1 (GLI1), a crucial effector of Hh signaling, regulates Hh pathway activation, we searched for GLI1-interacting proteins. We report that the chromatin remodeling protein SNF5 (encoded by SMARCB1, hereafter called SNF5), which is inactivated in human malignant rhabdoid tumors (MRTs), interacts with GLI1. We show that Snf5 localizes to Gli1-regulated promoters and that loss of Snf5 leads to activation of the Hh-Gli pathway. Conversely, re-expression of SNF5 in MRT cells represses GLI1. Consistent with this, we show the presence of a Hh-Gli-activated gene expression profile in primary MRTs and show that GLI1 drives the growth of SNF5-deficient MRT cells in vitro and in vivo. Therefore, our studies reveal that SNF5 is a key mediator of Hh signaling and that aberrant activation of GLI1 is a previously undescribed targetable mechanism contributing to the growth of MRT cells.
Subject(s)
Chromosomal Proteins, Non-Histone/metabolism , DNA-Binding Proteins/metabolism , Gene Expression Regulation, Neoplastic/genetics , Rhabdoid Tumor/genetics , Signal Transduction/genetics , Transcription Factors/metabolism , Animals , Cell Line, Tumor , Chromatin Immunoprecipitation , Chromosomal Proteins, Non-Histone/genetics , DNA Primers/genetics , DNA-Binding Proteins/genetics , Gene Expression Profiling , Humans , Immunoblotting , In Situ Hybridization , Mass Spectrometry , Mice , Microarray Analysis , SMARCB1 Protein , Transcription Factors/genetics , Zinc Finger Protein GLI1ABSTRACT
The malignant brain cancer medulloblastoma is characterized by mutations in Hedgehog (Hh) signaling pathway genes, which lead to constitutive activation of the G protein (heterotrimeric guanosine triphosphate-binding protein)-coupled receptor Smoothened (Smo). The Smo antagonist NVP-LDE225 inhibits Hh signaling and induces tumor regression in animal models of medulloblastoma. However, evidence of resistance was observed during the course of treatment. Molecular analysis of resistant tumors revealed several resistance mechanisms. We noted chromosomal amplification of Gli2, a downstream effector of Hh signaling, and, more rarely, point mutations in Smo that led to reactivated Hh signaling and restored tumor growth. Analysis of pathway gene expression signatures also, unexpectedly, identified up-regulation of phosphatidylinositol 3-kinase (PI3K) signaling in resistant tumors as another potential mechanism of resistance. Probing the relevance of increased PI3K signaling, we demonstrated that addition of the PI3K inhibitor NVP-BKM120 or the dual PI3K-mTOR (mammalian target of rapamycin) inhibitor NVP-BEZ235 to the initial treatment with the Smo antagonist markedly delayed the development of resistance. Our findings may be useful in informing treatment strategies for medulloblastoma.
