Nilotinib, an approved leukemia drug, inhibits smoothened signaling in Hedgehog-dependent medulloblastoma.

Dysregulation of the seven-transmembrane (7TM) receptor Smoothened (SMO) and other components of the Hedgehog (Hh) signaling pathway contributes to the development of cancers including basal cell carcinoma (BCC) and medulloblastoma (MB). However, SMO-specific antagonists produced mixed results in clinical trials, marked by limited efficacy and high rate of acquired resistance in tumors. Here we discovered that Nilotinib, an approved inhibitor of several kinases, possesses an anti-Hh activity, at clinically achievable concentrations, due to direct binding to SMO and inhibition of SMO signaling. Nilotinib was more efficacious than the SMO-specific antagonist Vismodegib in inhibiting growth of two Hh-dependent MB cell lines. It also reduced tumor growth in subcutaneous MB mouse xenograft model. These results indicate that in addition to its known activity against several tyrosine-kinase-mediated proliferative pathways, Nilotinib is a direct inhibitor of the Hh pathway. The newly discovered extension of Nilotinib's target profile holds promise for the treatment of Hh-dependent cancers

A PKC-SHP1 signaling axis desensitizes Fcγ receptor signaling by reducing the tyrosine phosphorylation of CBL and regulates FcγR mediated phagocytosis

BackgroundFcγ receptors mediate important biological signals in myeloid cells including the ingestion of microorganisms through a process of phagocytosis. It is well-known that Fcγ receptor (FcγR) crosslinking induces the tyrosine phosphorylation of CBL which is associated with FcγR mediated phagocytosis, however how signaling molecules coordinate to desensitize these receptors is unclear. An investigation of the mechanisms involved in receptor desensitization will provide new insight into potential mechanisms by which signaling molecules may downregulate tyrosine phosphorylation dependent signaling events to terminate important signaling processes.ResultsUsing the U937IF cell line, we observed that FcγR1 crosslinking induces the tyrosine phosphorylation of CBL, which is maximal at 5 min. followed by a kinetic pattern of dephosphorylation. An investigation of the mechanisms involved in receptor desensitization revealed that pretreatment of U937IF or J774 cells with PMA followed by Fcγ receptor crosslinking results in the reduced tyrosine phosphorylation of CBL and the abrogation of downstream signals, such as CBL-CRKL binding, Rac-GTP activation and the phagocytic response. Pretreatment of J774 cells with GF109203X, a PKC inhibitor was observed to block dephosphorylation of CBL and rescued the phagocytic response. We demonstrate that the PKC induced desensitization of FcγR/ phagocytosis is associated with the inactivation of Rac-GTP, which is deactivated in a hematopoietic specific phosphatase SHP1 dependent manner following ITAM stimulation. The effect of PKC on FcγR signaling is augmented by the transfection of catalytically active SHP1 and not by the transfection of catalytic dead SHP1 (C124S).ConclusionsOur results suggest a functional model by which PKC interacts with SHP1 to affect the phosphorylation state of CBL, the activation state of Rac and the negative regulation of ITAM signaling i.e. Fcγ receptor mediated phagocytosis. These findings suggest a mechanism for Fcγ receptor desensitization by which a serine-threonine kinase e.g. PKC downregulates tyrosine phosphorylation dependent signaling events via the reduced tyrosine phosphorylation of the complex adapter protein, CBL

A triple action CDK4/6-PI3K-BET inhibitor with augmented cancer cell cytotoxicity

National Institutes of Health GM125195, GM135671, CA192656, FD00511

Epidermal Growth Factor Receptor and PTEN Modulate Tissue Factor Expression in Glioblastoma through JunD/Activator Protein-1 Transcriptional Activity

Hypoxia and necrosis are fundamental features of glioblastoma (GBM) and their emergence is critical for the rapid biological progression of this fatal tumor; yet, underlying mechanisms are poorly understood. We have suggested that vaso-occlusion following intravascular thrombosis could initiate or propagate hypoxia and necrosis in GBM. Tissue factor (TF), the main cellular initiator of coagulation, is overexpressed in GBMs and likely favors a thrombotic microenvironment. Epidermal growth factor receptor (EGFR) amplification and PTEN loss are two common genetic alterations seen in GBM but not in lower-grade astrocytomas that could be responsible for TF up-regulation. The most frequent EGFR mutation in GBM involves deletion of exons 2 to 7, resulting in the expression of a constitutively active receptor, EGFRvIII. Here, we show that overexpression of EGFR or EGFRvIII in human glioma cells causes increased basal TF expression and that stimulation of EGFR by its ligand, EGF, leads to a marked dose-dependent up-regulation of TF. In all cases, increased TF expression led to accelerated plasma coagulation in vitro. EGFR-mediated TF expression depended most strongly on activator protein-1 (AP-1) transcriptional activity and was associated with c-Jun NH2-terminal kinase (JNK) and JunD activation. Restoration of PTEN expression in PTEN-deficient GBM cells diminished EGFR-induced TF expression by inhibiting JunD/AP-1 transcriptional activity. PTEN mediated this effect by antagonizing phosphatidylinositol 3-kinase activity, which in turn attenuated both Akt and JNK activities. These mechanisms are likely at work in vivo, as EGFR expression was highly correlated with TF expression in human high-grade astrocytoma specimens

Heterozygosity for Pten Promotes Tumorigenesis in a Mouse Model of Medulloblastoma

BACKGROUND: Recent publications have described an important role for cross talk between PI-3 kinase and sonic hedgehog signaling pathways in the pathogenesis of medulloblastoma. METHODOLOGY/PRINCIPAL FINDINGS: We crossed mice with constitutive activation of Smoothened, SmoA1, with Pten deficient mice. Both constitutive and conditional Pten deficiency doubled the incidence of mice with symptoms of medulloblastoma and resulted in decreased survival. Analysis revealed a clear separation of gene signatures, with up-regulation of genes in the PI-3 kinase signaling pathway, including downstream activation of angiogenesis in SmoA1+/-; Pten +/- medulloblastomas. Western blotting and immunohistochemistry confirmed reduced or absent Pten, Akt activation, and increased angiogenesis in Pten deficient tumors. Down-regulated genes included genes in the sonic hedgehog pathway and tumor suppressor genes. SmoA1+/-; Pten +/+ medulloblastomas appeared classic in histology with increased proliferation and diffuse staining for apoptosis. In contrast, Pten deficient tumors exhibited extensive nodularity with neuronal differentiation separated by focal areas of intense staining for proliferation and virtually absent apoptosis. Examination of human medulloblastomas revealed low to absent PTEN expression in over half of the tumors. Kaplan-Meier analysis confirmed worse overall survival in patients whose tumor exhibited low to absent PTEN expression. CONCLUSIONS/SIGNIFICANCE: This suggests that PTEN expression is a marker of favorable prognosis and mouse models with activation of PI-3 kinase pathways may be important tools for preclinical evaluation of promising agents for the treatment of medulloblastoma

Combinatorial Approach to Improve Cancer Immunotherapy: Rational Drug Design Strategy to Simultaneously Hit Multiple Targets to Kill Tumor Cells and to Activate the Immune System

Cancer immunotherapy, including immune checkpoint blockade and adoptive CAR T-cell therapy, has clearly established itself as an important modality to treat melanoma and other malignancies. Despite the tremendous clinical success of immunotherapy over other cancer treatments, this approach has shown substantial benefit to only some of the patients while the rest of the patients have not responded due to immune evasion. In recent years, a combination of cancer immunotherapy together with existing anticancer treatments has gained significant attention and has been extensively investigated in preclinical or clinical studies. In this review, we discuss the therapeutic potential of novel regimens combining immune checkpoint inhibitors with therapeutic interventions that (1) increase tumor immunogenicity such as chemotherapy, radiotherapy, and epigenetic therapy; (2) reverse tumor immunosuppression such as TAMs, MDSCs, and Tregs targeted therapy; and (3) reduce tumor burden and increase the immune effector response with rationally designed dual or triple inhibitory chemotypes