pi103 and Neoplasms

The mammalian target of rapamycin (mTOR), a serine/threonine protein kinase, acts as a "master switch" for cellular anabolic and catabolic processes, regulating the rate of cell growth and proliferation. Dysregulation of the mTOR signaling pathway occurs frequently in a variety of human tumors, and thus, mTOR has emerged as an important target for the design of anticancer agents. mTOR is found in two distinct multiprotein complexes within cells, mTORC1 and mTORC2. These two complexes consist of unique mTOR-interacting proteins and are regulated by different mechanisms. Enormous advances have been made in the development of drugs known as mTOR inhibitors. Rapamycin, the first defined inhibitor of mTOR, showed effectiveness as an anticancer agent in various preclinical models. Rapamycin analogues (rapalogs) with better pharmacologic properties have been developed. However, the clinical success of rapalogs has been limited to a few types of cancer. The discovery that mTORC2 directly phosphorylates Akt, an important survival kinase, adds new insight into the role of mTORC2 in cancer. This novel finding prompted efforts to develop the second generation of mTOR inhibitors that are able to target both mTORC1 and mTORC2. Here, we review the recent advances in the mTOR field and focus specifically on the current development of the second generation of mTOR inhibitors as anticancer agents.

Topics: Antineoplastic Agents; Cell Proliferation; Furans; Humans; Imidazoles; Indoles; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; Morpholines; Multiprotein Complexes; Naphthyridines; Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Purines; Pyridines; Pyrimidines; Quinolines; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

The phosphatidylinositide 3-kinase (PI3K) pathway is very commonly activated in a wide range of human cancers and is a major driving force in oncogenesis. One of the class I lipid kinase members of the PI3K family, p110alpha, is probably the most commonly mutated kinase in the human genome. Alongside genetic, molecular biological, and biochemical studies, chemical inhibitors have been extremely helpful tools in understanding the role of PI3K enzymes in signal transduction and downstream physiological and pathological processes, and also in validating PI3Ks as therapeutic targets. Although they have been valuable in the past, the early and still frequently employed inhibitors, wortmannin and LY294002, have significant limitations as chemical tools. Here, we discuss the case history of the discovery and properties of an increasingly used chemical probe, the pan-class I PI3K and mammalian target of rapamycin (mTOR) inhibitor PI-103 (a pyridofuropyrimidine), and its very recent evolution into the thienopyrimidine drug GDC-0941, which exhibits excellent oral anticancer activity in preclinical models and is now undergoing phase I clinical trials in cancer patients. We also illustrate the impact of structural biology on the design of PI3K inhibitors and on the interpretation of their effects. The challenges and outlook for drugging the PI3 kinome are discussed in the more general context of the role of structural biology and chemical biology in innovative drug discovery.

Topics: Animals; Drug Delivery Systems; Furans; Humans; Indazoles; Models, Molecular; Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Kinase Inhibitors; Pyridines; Pyrimidines; Sulfonamides

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

A series of quinoline derivatives featuring the novelty of introducing intra-molecular hydrogen bonding scaffold (iMHBS) were designed, synthesized and biologically evaluated for their mTOR inhibitory activity, as well as anti-proliferative efficacies against HCT-116, PC-3 and MCF-7 cell lines. As a result, six compounds exhibited significant inhibition against mTOR with IC50 values below 35nM. Compound 15a, the most potent mTOR inhibitor reported herein (IC50=14nM), also displayed the most favorable cellular activities, with the IC50 values of 0.46, 0.61 and 0.24μM against HCT-116, PC-3 and MCF-7, respectively. Besides, several compounds in this series were identified to be selective over class I PI3Ks. Further western blot analysis of 16b, a representative compound in this series, highlighted their advantage in surmounting the S6K/IRS1/PI3K negative feedback loop upon dual inhibition of mTORC1 and mTORC2. In addition to the remarkable activity, 15a demonstrated acceptable stability in simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and liver microsome, thereby being valuable for extensive in vivo investigation.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; Drug Design; HCT116 Cells; Humans; Hydrogen Bonding; MCF-7 Cells; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; Molecular Docking Simulation; Multiprotein Complexes; Neoplasms; Phosphatidylinositol 3-Kinases; Protein Kinase Inhibitors; Quinolines; Signal Transduction; TOR Serine-Threonine Kinases

JAK2V617F is the most common oncogenic lesion in patients with myeloproliferative neoplasms (MPNs). Despite the ability of JAK2V617F to instigate DNA damage in vitro, MPNs are nevertheless characterized by genomic stability. In this study, we address this paradox by identifying the DNA helicase RECQL5 as a suppressor of genomic instability in MPNs. We report increased RECQL5 expression in JAK2V617F-expressing cells and demonstrate that RECQL5 is required to counteract JAK2V617F-induced replication stress. Moreover, RECQL5 depletion sensitizes JAK2V617F mutant cells to hydroxyurea (HU), a pharmacological inducer of replication stress and the most common treatment for MPNs. Using single-fiber chromosome combing, we show that RECQL5 depletion in JAK2V617F mutant cells impairs replication dynamics following HU treatment, resulting in increased double-stranded breaks and apoptosis. Cumulatively, these findings identify RECQL5 as a critical regulator of genome stability in MPNs and demonstrate that replication stress-associated cytotoxicity can be amplified specifically in JAK2V617F mutant cells through RECQL5-targeted synthetic lethality.

Topics: Animals; Apoptosis; Cell Line, Tumor; Cell Survival; DNA Breaks, Double-Stranded; DNA Replication; Furans; Gene Knock-In Techniques; Genomic Instability; Humans; Hydroxyurea; Janus Kinase 2; Mice; Mice, Inbred C57BL; Mutagenesis, Site-Directed; Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Pyridines; Pyrimidines; RecQ Helicases; RNA Interference; RNA, Small Interfering; Signal Transduction

Autophagy is a highly regulated, energy dependent cellular process where proteins, organelles and cytoplasm are sequestered in autophagosomes and digested to sustain cellular homeostasis. We hypothesized that during autophagy induced in cancer cells by i) starvation through serum and amino acid deprivation or ii) treatment with PI-103, a class I PI3K/mTOR inhibitor, glycolytic metabolism would be affected, reducing flux to lactate, and that this effect may be reversible. We probed metabolism during autophagy in colorectal HT29 and HCT116 Bax knock-out cells using hyperpolarized (13)C-magnetic resonance spectroscopy (MRS) and steady-state (1)H-MRS. 24 hr PI103-treatment or starvation caused significant reduction in the apparent forward rate constant (k(PL)) for pyruvate to lactate exchange compared with controls in HT29 (100 μM PI-103: 82%, p = 0.05) and HCT116 Bax-ko cells (10 μM PI-103: 53%, p = 0.05; 20 μM PI-103: 42%, p<0.0001; starvation: 52%, p<0.001), associated with reduced lactate excretion and intracellular lactate in all cases, and unchanged lactate dehydrogenase (LDH) activity and increased NAD+/NADH ratio following PI103 treatment or decreased LDH activity and unchanged NAD+/NADH ratio following starvation. After 48 hr recovery from PI103 treatment, k(PL) remained below control levels in HT29 cells (74%, p = 0.02), and increased above treated values, but remained below 24 hr vehicle-treated control levels in HCT116 Bax-ko cells (65%, p = 0.004) both were accompanied by sustained reduction in lactate excretion, recovery of NAD+/NADH ratio and intracellular lactate. Following recovery from starvation, k(PL) was significantly higher than 24 hr vehicle-treated controls (140%, p = 0.05), associated with increased LDH activity and total cellular NAD(H). Changes in k(PL) and cellular and excreted lactate provided measureable indicators of the major metabolic processes accompanying starvation- and drug-induced autophagy. The changes are reversible, returning towards and exceeding control values on cellular recovery, which potentially identifies resistance. k(PL) (hyperpolarized (13)C-MRS) and lactate ((1)H-MRS) provide useful biomarkers for the autophagic process, enabling non-invasive monitoring of the Warburg effect.

Topics: Autophagy; bcl-2-Associated X Protein; Carbon Isotopes; Cell Line, Tumor; Furans; Gene Knockdown Techniques; Humans; Isotope Labeling; L-Lactate Dehydrogenase; Lactic Acid; NAD; Neoplasms; Pyridines; Pyrimidines

Most investigations into cancer cell drug response are performed with cells cultured on flat (2D) tissue culture plastic. Emerging research has shown that the presence of a three-dimensional (3D) extracellular matrix (ECM) is critical for normal cell behavior including migration, adhesion, signaling, proliferation and apoptosis. In this study we investigate differences between cancer cell signaling in 2D culture and a 3D ECM, employing real-time, live cell tracking to directly observe U2OS human osteosarcoma and MCF7 human breast cancer cells embedded in type 1 collagen gels. The activation of the important PI3K signaling pathway under these different growth conditions is studied, and the response to inhibition of both PI3K and mTOR with PI103 investigated. Cells grown in 3D gels show reduced proliferation and migration as well as reduced PI3K pathway activation when compared to cells grown in 2D. Our results quantitatively demonstrate that a collagen ECM can protect U2OS cells from PI103. Overall, our data suggests that 3D gels may provide a better medium for investigation of anti-cancer drugs than 2D monolayers, therefore allowing better understanding of cellular response and behavior in native like environments.

Topics: Apoptosis; Blotting, Western; Cell Adhesion; Cell Culture Techniques; Cell Line, Tumor; Cell Movement; Cell Proliferation; Collagen Type I; Extracellular Matrix; Furans; Gels; Humans; MCF-7 Cells; Microscopy, Confocal; Microscopy, Video; Neoplasms; Phosphatidylinositol 3-Kinases; Pyridines; Pyrimidines; Signal Transduction; TOR Serine-Threonine Kinases

Although Akt is known as a survival kinase, inhibitors of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway do not always induce substantial apoptosis. We show that silencing Akt1 alone, or any combination of Akt isoforms, can suppress the growth of tumors established from phosphatase and tensin homologue-null human cancer cells. Although these findings indicate that Akt is essential for tumor maintenance, most tumors eventually rebound. Akt knockdown or inactivation with small molecule inhibitors did not induce significant apoptosis but rather markedly increased autophagy. Further treatment with the lysosomotropic agent chloroquine caused accumulation of abnormal autophagolysosomes and reactive oxygen species, leading to accelerated cell death in vitro and complete tumor remission in vivo. Cell death was also promoted when Akt inhibition was combined with the vacuolar H(+)-adenosine triphosphatase inhibitor bafilomycin A1 or with cathepsin inhibition. These results suggest that blocking lysosomal degradation can be detrimental to cancer cell survival when autophagy is activated, providing rationale for a new therapeutic approach to enhancing the anticancer efficacy of PI3K-Akt pathway inhibition.

Topics: Animals; Apoptosis; Autophagy; Autophagy-Related Protein 7; Benzylamines; Cell Cycle; Cell Line, Tumor; Chloroquine; Drug Interactions; Female; Furans; Humans; Lysosomes; Macrolides; Mice; Mice, Nude; Mitochondria; Mutation; Neoplasms; Phosphoinositide-3 Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Proton-Translocating ATPases; PTEN Phosphohydrolase; Pyridines; Pyrimidines; Quinoxalines; Reactive Oxygen Species; RNA Interference; RNA, Small Interfering; Ubiquitin-Activating Enzymes; Xenograft Model Antitumor Assays

Extensive evidence implicates activation of the lipid phosphatidylinositide 3-kinase (PI3K) pathway in the genesis and progression of various human cancers. PI3K inhibitors thus have considerable potential as molecular cancer therapeutics. Here, we detail the pharmacologic properties of a prototype of a new series of inhibitors of class I PI3K. PI103 is a potent inhibitor with low IC50 values against recombinant PI3K isoforms p110alpha (2 nmol/L), p110beta (3 nmol/L), p110delta (3 nmol/L), and p110gamma (15 nmol/L). PI103 also inhibited TORC1 by 83.9% at 0.5 micromol/L and exhibited an IC50 of 14 nmol/L against DNA-PK. A high degree of selectivity for the PI3K family was shown by the lack of activity of PI103 in a panel of 70 protein kinases. PI103 potently inhibited proliferation and invasion of a wide variety of human cancer cells in vitro and showed biomarker modulation consistent with inhibition of PI3K signaling. PI103 was extensively metabolized, but distributed rapidly to tissues and tumors. This resulted in tumor growth delay in eight different human cancer xenograft models with various PI3K pathway abnormalities. Decreased phosphorylation of AKT was observed in U87MG gliomas, consistent with drug levels achieved. We also showed inhibition of invasion in orthotopic breast and ovarian cancer xenograft models and obtained evidence that PI103 has antiangiogenic potential. Despite its rapid in vivo metabolism, PI103 is a valuable tool compound for exploring the biological function of class I PI3K and importantly represents a lead for further optimization of this novel class of targeted molecular cancer therapeutic.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Movement; Endothelial Cells; Enzyme Inhibitors; Female; Flow Cytometry; Furans; Humans; Immunoblotting; Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Proto-Oncogene Proteins c-akt; Pyridines; Pyrimidines; Xenograft Model Antitumor Assays