wye-125132 and Neoplasms

While cancer cell mitochondria mediate actions of many successful chemotherapeutics, little is known about mitochondrial response in mTOR-targeted anticancer therapy. We have studied mitochondrial dynamics in relation to growth suppression employing an allosteric inhibitor rapalog, a highly selective mTOR kinase inhibitor (mTOR-KI) and mTOR-ShRNA. Global targeting of mTOR increased mitochondrial membrane potential (mΔψ) and inhibited mitochondrial permeability transition pore (mPTP). Importantly, these mTOR-KI-provoked anti-survival and pro-survival effects were differentially manifested in diverse cancer cells according to intrinsic susceptibility to mTOR-targeting. The most-sensitive cells including those possessing hyperactive PI3K/AKT/mTOR and/or growth factor-dependence (LNCap, MDA361 and MG63) all displayed a dramatic increase in mΔψ, whereas the mΔψ increase was not evident in majority of resistant cancer cells. Upon mTOR-KI treatment, the resistant cells including those harboring K-Ras- or B-Raf mutation (MDA231, HT29 and HCT116) all displayed a markedly reduced mPTP opening, which paralleled a sustained AKT-hexokinase 2 (HK2) survival signaling and persistent phosphorylation (inactivation) of GSK3β. Further studies demonstrated that the mTOR-KI-provoked mPTP closure in resistant cells was mediated through an enhanced binding of HK2 to the mitochondrial voltage-dependent anion channel (VDAC), a molecular mechanism known to promote mPTP closure and cell survival. Detaching HK2 from VDAC by an HK2-displacing peptide or methyl jasmonate specifically blocked the mTOR-KI-provoked mPTP closure and potentiated growth suppression in resistant cells. Thus, mTOR-inhibition can exert complex and differential perturbation to mitochondrial dynamics in cancer cells, which likely influence therapeutic outcome of mTOR-targeted therapy.

Topics: Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Humans; Membrane Potential, Mitochondrial; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Neoplasms; Phenylurea Compounds; Phosphatidylinositol 3-Kinases; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Pyrazoles; TOR Serine-Threonine Kinases; Tumor Cells, Cultured; Voltage-Dependent Anion Channel 1

The mammalian target of rapamycin (mTOR) is a major component of the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway that is dysregulated in 50% of all human malignancies. Rapamycin and its analogues (rapalogs) partially inhibit mTOR through allosteric binding to mTOR complex 1 (mTORC1) but not mTOR complex 2 (mTORC2), an emerging player in cancer. Here, we report WYE-125132 (WYE-132), a highly potent, ATP-competitive, and specific mTOR kinase inhibitor (IC(50): 0.19 +/- 0.07 nmol/L; >5,000-fold selective versus PI3Ks). WYE-132 inhibited mTORC1 and mTORC2 in diverse cancer models in vitro and in vivo. Importantly, consistent with genetic ablation of mTORC2, WYE-132 targeted P-AKT(S473) and AKT function without significantly reducing the steady-state level of the PI3K/PDK1 activity biomarker P-AKT(T308), highlighting a prominent and direct regulation of AKT by mTORC2 in cancer cells. Compared with the rapalog temsirolimus/CCI-779, WYE-132 elicited a substantially stronger inhibition of cancer cell growth and survival, protein synthesis, cell size, bioenergetic metabolism, and adaptation to hypoxia. Oral administration of WYE-132 to tumor-bearing mice showed potent single-agent antitumor activity against MDA361 breast, U87MG glioma, A549 and H1975 lung, as well as A498 and 786-O renal tumors. An optimal dose of WYE-132 achieved a substantial regression of MDA361 and A549 large tumors and caused complete regression of A498 large tumors when coadministered with bevacizumab. Our results further validate mTOR as a critical driver for tumor growth, establish WYE-132 as a potent and profound anticancer agent, and provide a strong rationale for clinical development of specific mTOR kinase inhibitors as new cancer therapy.

Topics: Animals; Apoptosis; Cell Cycle; Cell Growth Processes; Cell Hypoxia; Female; Humans; Intracellular Signaling Peptides and Proteins; Mechanistic Target of Rapamycin Complex 1; Mice; Multiprotein Complexes; Neoplasms; Phenylurea Compounds; Phosphatidylinositol 3-Kinases; Protein Serine-Threonine Kinases; Proteins; Proto-Oncogene Proteins c-akt; Pyrazoles; Sirolimus; TOR Serine-Threonine Kinases; Transcription Factors