Project description:The clinical benefit of current mTOR inhibitors is limited, perhaps reflecting their intrinsic pharmacological profiles. Rapamycin analogs selectively inhibit mTORC1, but fail to suppress phosphorylation of the mTORC1 substrate 4EBP1, a translational repressor that is a key driver of oncogenic mTORC1 signaling. mTOR kinase active-site inhibitors fully suppress mTORC1 and phosphorylation of its substrates, but are active against mTORC2 and additional kinases, potentially contributing to tolerability limitations. The prototype bi-steric inhibitor RapaLink-1 exploits the selective mTORC1 interactions of rapamycin and the broad mTOR kinase inhibitory effects of an active-site inhibitor, through covalent linkage of the two pharmacophores to achieve complete mTORC1/2 inhibition. We demonstrate that the anti-proliferative activity of RapaLink-1 is dependent upon mTORC1 and suppression of 4EBP1 phosphorylation. Using a rational design strategy, we tuned the affinities of the rapamycin core and ATP-mimetic moieties to create novel bi-steric inhibitors with enhanced mTORC1 selectivity and potency against 4EBP1 phosphorylation. mTORC1-selective bi-steric compounds produced durable inhibition of 4EBP1 phosphorylation in vitro and in vivo, and drove tumor regressions at well-tolerated doses in xenograft models of breast cancer.
Project description:The PI3K-AKT-mTOR pathway is commonly dysregulated in cancer. Rapalogs exhibit modest clinical benefit likely due to their lack of effects on 4E-BP1. We hypothesized that bi-steric mTORC1-selective inhibitors would have greater potential for clinical benefit than rapalogs in tumors with mTORC1 dysfunction. We assessed this hypothesis in tumor models with high mTORC1 activity both in vitro and in vivo. Bi-steric inhibitors had strong growth inhibition, eliminated phosphorylated 4EBP1, and induced more apoptosis than rapamycin or MLN0128. Multi-omic analysis showed extensive effects of the bi-steric inhibitors in comparison to rapamycin. De novo purine synthesis was markedly and selectively inhibited by bi-sterics through reduction in JUN and its downstream target PRPS1 and appeared to be the cause of apoptosis. Hence, bi-steric mTORC1-selective inhibitors are a novel therapeutic strategy to treat tumors driven by mTORC1 hyperactivation.
Project description:we examined if the activation of the anabolic program mediated by the activation of the mTorc1 complex in the fasted state could suppress the robust catabolic programing and enhanced Pparα transcriptional of mice with a liver specific defect in mitochondrial long chain fatty acid oxidation (Cpt2L-/- mice). We found that the activation of mTorc1 in the fasted state was not sufficient to repress Pparα responsive genes or ketogenesis.
Project description:Pathologic activation of the Toll-like receptor (TLR) pathway underlies various human disorders such as autoimmune diseases, chronic inflammatory diseases and lymphoid malignancies. Current therapy of these diseases relies on immunosuppressive or chemotherapeutic agents, but more effective therapeutics tailored to disease-causing mechanisms are needed. Pivotal to TLR signaling is the IL-1 receptor-associated kinase 4 (IRAK4), which is recruited to TLRs by the adaptor protein MyD88. Recruitment of IRAK kinases to MyD88, triggers the formation of a signaling competent myddosome complex, which underlies the pathogenesis of many immuno-inflammatory disorders, suggesting that IRAK4 inhibitors might be useful in the treatment of these diseases. Gain-of-function MYD88 mutations activate IRAK4 in several mature B cell malignancies, including activated B-cell-like diffuse large B cell lymphoma (ABC DLBCL). Development of selective IRAK4 inhibitors has been confounded by the challenging structure of the IRAK4 catalytic domain. Using structure-based drug design methodologies, we identified potent and selective IRAK4 inhibitors. These small molecules suppress LPS-induced TNFalpha production in vitro and in vivo, and are efficacious in mouse models of collagen-induced arthritis and MyD88-dependent inflammatory gout. Human ABC DLBCL cell lines that harbor the activating, oncogenic MyD88 L265P mutation are killed by IRAK4 inhibitors, both in vitro and in mouse xenograft models. IRAK4 inhibitors synergize with the BTK inhibitor ibrutinib, with the Syk inhibitor PRT062607, and with the Bcl-2 inhibitor ABT-199 in killing ABC DLBCL cells, suggesting new therapeutic strategies for this refractory cancer. Four ABC DLBCL cell lines (OCI-Ly10, TMD8, HBL1 and OCI-Ly3), were treated with either ND-2158 or the structurally related negative control compound ND-1659 for 6, 12, 24 or 36 h in culture. Gene expression profiling was performed using two-color human Agilent 4x44K gene expression arrays comparing signal from control compound-treated (ND-1659) control cells (Cy3), to cells treated with ND-2158 for the indicated times (Cy5).
Project description:The CDK4/6 kinase is dysregulated in melanoma highlighting a potential therapeutic benefit. Indeed, such CDK4/6 inhibitors are being evaluated in trials for melanoma and additional cancers. While beneficial, resistance to therapy is a concern and the molecular mechanisms of such resistance remain undefined. Here, we demonstrate that reactivation of mTORC1 signaling through increased expression of the amino acid transporter, SLC36A1, drives resistance to CDK4/6 inhibitors. Increased expression of SLC36A1 reflects two distinct mechanisms; 1) Rb loss which drives SLC36A1 via reduced suppression of E2f; 2) FXR1 overexpression which promotes SLC36A1 translation and subsequently mTORC1. Finally, we demonstrate that a combination of a CDK4/6 inhibitor with an mTORC1 inhibitor has increased therapeutic efficacy in vivo providing an important avenue for improved therapeutic intervention in aggressive melanoma.
Project description:Using platinum-resistant OVCAR-3 cells treated with the selective mTORC1/2 inhibitor INK128/MLN128, we conducted genome-wide transcription and translation studies and analyzed the effect on cell proliferation, AKT-mTOR signaling and cell survival, to determine whether carboplatin resistance involves selective mRNA translational reprogramming, and whether it is sensitive to mTORC1/2 inhibitio.n