tgx-221 and Neoplasms

The intracellular PI3K-AKT-mTOR pathway is involved in regulation of numerous important cell processes including cell growth, differentiation, and metabolism. The PI3Kα isoform has received particular attention as a novel molecular target in gene therapy, since this isoform plays critical roles in tumor progression and tumor blood flow and angiogenesis. However, the role of PI3Kα and other class I isoforms, i.e. PI3Kβ, γ, δ, in the regulation of vascular tone and regional blood flow are largely unknown. We used novel isoform-specific PI3K inhibitors and mice deficient in both PI3Kγ and PI3Kδ (Pik3cg(-/-)/Pik3cd(-/-)) to define the putative contribution of PI3K isoform(s) to arterial vasoconstriction. Wire myography was used to measure isometric contractions of isolated murine mesenteric arterial rings. Phenylephrine-dependent contractions were inhibited by the pan PI3K inhibitors wortmannin (100 nM) and LY294002 (10 µM). These vasoconstrictions were also inhibited by the PI3Kα isoform inhibitors A66 (10 µM) and PI-103 (1 µM), but not by the PI3Kβ isoform inhibitor TGX 221 (100 nM). Pik3cg(-/-)/Pik3cd(-/-)-arteries showed normal vasoconstriction. We conclude that PI3Kα is an important downstream element in vasoconstrictor GPCR signaling, which contributes to arterial vasocontraction via α1-adrenergic receptors. Our results highlight a regulatory role of PI3Kα in the cardiovascular system, which widens the spectrum of gene therapy approaches targeting PI3Kα in cancer cells and tumor angiogenesis and regional blood flow.

Topics: Androstadienes; Animals; Chromones; Class I Phosphatidylinositol 3-Kinases; Class Ib Phosphatidylinositol 3-Kinase; Furans; Mesenteric Arteries; Mice; Mice, Knockout; Morpholines; Neoplasms; Neovascularization, Pathologic; Phenylephrine; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Pyridines; Pyrimidines; Pyrimidinones; Receptors, Adrenergic, alpha-1; Signal Transduction; Vasoconstriction; Wortmannin

Compelling molecular biology publications have reported the implication of phosphoinositide kinase PI3Kβ in PTEN-deficient cell line growth and proliferation. These findings supported a scientific rationale for the development of PI3Kβ-specific inhibitors for the treatment of PTEN-deficient cancers. This paper describes the discovery of 2-[2-(2,3-dihydro-indol-1-yl)-2-oxo-ethyl]-6-morpholin-4-yl-3H-pyrimidin-4-one (7) and the optimization of this new series of active and selective pyrimidone indoline amide PI3Kβ inhibitors. 2-[2-(2-Methyl-2,3-dihydro-indol-1-yl)-2-oxo-ethyl]-6-morpholin-4-yl-3H-pyrimidin-4-one (28), identified following a carefully designed methyl scan, displayed improved physicochemical and in vitro pharmacokinetic properties. Structural biology efforts enabled the acquisition of the first X-ray cocrystal structure of p110β with the selective inhibitor compound 28 bound to the ATP site. The nonplanar binding mode described herein is consistent with observed structure-activity relationship for the series. Compound 28 demonstrated significant in vivo activity in a UACC-62 xenograft model in mice, warranting further preclinical investigation. Following successful development, compound 28 entered phase I/Ib clinical trial in patients with advanced cancer.

Topics: Animals; Antineoplastic Agents; Biological Availability; Cell Line, Tumor; Cell Membrane Permeability; Crystallography, X-Ray; Dogs; Drug Screening Assays, Antitumor; Female; Heterografts; Humans; Indoles; Male; Mice; Mice, Inbred BALB C; Mice, SCID; Microsomes, Liver; Molecular Conformation; Molecular Docking Simulation; Neoplasm Transplantation; Neoplasms; Phosphoinositide-3 Kinase Inhibitors; Protein Binding; PTEN Phosphohydrolase; Pyrimidinones; Rats; Rats, Nude; Solubility; Stereoisomerism; Structure-Activity Relationship

Cancer-specific mutations in the iSH2 (inter-SH2) and nSH2 (N-terminal SH2) domains of p85alpha, the regulatory subunit of phosphatidylinositide 3-kinase (PI3K), show gain of function. They induce oncogenic cellular transformation, stimulate cellular proliferation, and enhance PI3K signaling. Quantitative determinations of oncogenic activity reveal large differences between individual mutants of p85alpha. The mutant proteins are still able to bind to the catalytic subunits p110alpha and p110beta. Studies with isoform-specific inhibitors of p110 suggest that expression of p85 mutants in fibroblasts leads exclusively to an activation of p110alpha, and p110alpha is the sole mediator of p85 mutant-induced oncogenic transformation. The characteristics of the p85 mutants are in agreement with the hypothesis that the mutations weaken an inhibitory interaction between p85alpha and p110alpha while preserving the stabilizing interaction between p85alpha iSH2 and the adapter-binding domain of p110alpha.

Topics: Adenine; Amino Acid Sequence; Animals; Base Sequence; Blotting, Western; Catalytic Domain; Cell Line; Cell Proliferation; Cell Transformation, Neoplastic; Cells, Cultured; Chick Embryo; Class I Phosphatidylinositol 3-Kinases; Dioxoles; Fibroblasts; Humans; Immunoprecipitation; Morpholines; Mutation; Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Binding; Protein Subunits; Pyrimidinones; Quinazolines; Thiazolidinediones; Transfection