Identification of dual mTORC1 and mTORC2 inhibitors in melanoma cells: Prodigiosin vs. obatoclax

Abstract

The PI3K/AKT/mTOR signaling pathway regulates cell proliferation, survival and angiogenesis. The mammalian target of rapamycin (mTOR) is a protein kinase ubiquitously expressed within cells that regulates cell growth and survival by integrating nutrient and hormonal signals. mTOR exists in two complexes, mTORC1 and mTORC2. Hyperactivation of the mTOR protein has been linked to development of cancer, raising mTOR as an attractive target for cancer therapy. Prodigiosin (PG) and Obatoclax (OBX), two members of the prodiginines family, are small molecules with anticancer properties which are currently under clinical trials. In the present paper, we demonstrate that mTOR is a molecular target of both prodiginines in melanoma, a highly drug-resistant cancer model. The inhibition of mTORC1 and mTORC2 complexes by PG or OBX resulted in a loss of AKT phosphorylation at S473, preventing its full activation, with no significant effect on T308. The strongest activity inhibition (89%) was induced by PG on mTORC2. Binding assays using Surface Plasmon Resonance (SPR) provide kinetic and affinity data of the interaction of these small molecules with mTOR. In addition, in silico modelling produced a detailed atomic description of the binding modes. These results provide new data to understand the mechanism of action of these molecules, and provide new structural data that will allow the development of more specific mTOR inhibitors for cancer treatment.3

BH3 Mimetics: Status of the Field and New Developments

“…The one reported that inhibition of the AKT/mTOR pathway is an additional off-target effect of obatoclax (43). The other has indicated that this compound can directly activate BAX (44), supporting the data of Gavathiotis and colleagues with the SAHB derived from BIM capable of binding and activating BAX (38,39).…”

Combined targeting of MEK and PI3K/mTOR effector pathways is necessary to effectively inhibit NRAS mutant melanoma in vitro and in vivo

“…This is in agreement with findings from other groups and might be explained by the recruitment of additional prosurvival downstream effector pathways by mutant NRAS such as the PI3K/mTOR pathway (29,30,32,33). Indeed, previous studies found that binding of RAS to PI3Kp100α is required for RAS-driven tumorigenesis and that mTOR 2 is essential for transformation as well as for the vitality of melanoma cells (32,34). However, targeting the PI3K/mTOR pathway in isolation only moderately reduced cell viability with PI3K/mTOR 1,2 inhibitors being the most potent.…”

Computational Prediction of HIV-1 Resistance to Protease Inhibitors

“…To this aim we have used PELE, an atomic-resolution sampling algorithm combining a stochastic Monte Carlo procedure with protein structure prediction techniques, which is specially suited for induced-fit docking problems. 41,42 Since most of the mutant structures have not been crystallized, one of the main questions is how to generate an all atom model for each sequence. Since we were comparing the binding energies to the NL4-3 reference sequence, one simple strategy would have been to use its structure as a template (in Modeller, 50, 51 I-TASSER, 52 etc.).…”

“…40 PELE has recently shown to provide competitive advantages with respect to state of the art induced fit commercial software and to reproduce the conformational sampling obtained in microsecond molecular dynamics (MD) trajectories. 41,42 A total of 12 independent MC trajectories were produced for each inhibitor and mutant sequence. Trajectories were interrupted after 12h of CPU, providing approximately a total of 6000 Monte Carlo steps and ~2000 accepted minima.…”