pki-587 and Pancreatic-Neoplasms

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Bcl-2-Like Protein 11; Benzamides; Carcinoma, Pancreatic Ductal; Cell Line, Tumor; Cell Survival; Diphenylamine; Drug Screening Assays, Antitumor; Humans; MAP Kinase Signaling System; Morpholines; Mutation; Myeloid Cell Leukemia Sequence 1 Protein; Pancreatic Neoplasms; Phosphatidylinositol 3-Kinases; Protein Kinase Inhibitors; Proto-Oncogene Proteins p21(ras); RNA, Small Interfering; TOR Serine-Threonine Kinases; Triazines

Topics: Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Pancreatic Ductal; Cell Growth Processes; Drug Synergism; Heterocyclic Compounds, 3-Ring; Humans; MAP Kinase Kinase Kinases; Morpholines; Pancreatic Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Kinase Inhibitors; Pyridones; Pyrimidinones; Triazines

The characteristic clinical heterogeneity and mostly slow-growing behavior of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) cause problems in finding appropriate treatments. Thus, the current therapy options are not satisfactory. PKI-587 is a highly potent, novel dual inhibitor of PI3K and mTORC1/C2.. We assessed the effects of PKI-587 in different GEP-NEN tumor models, including the poorly differentiated cell line LCC-18, and compared them with those of the established mTORC1 inhibitor everolimus.. We treated BON, QGP-1, KRJ-I, and LCC-18 cell lines with increasing concentrations of the inhibitor PKI-587, and compared the results with those of everolimus and DMSO. We assessed the impact of the treatments on viability (WST-1 assay), on apoptotic processes (caspase 3/7 assay, JC-1), and on cell cycle regulation (flow cytometry). We determined alterations in signaling mediators by phosphor-specific Western blot analysis and conducted multiplexed gene expression analysis (nCounter® technology).. In all cell lines, PKI-587 dose-dependently inhibited proliferation, whereas everolimus was less effective. Treatment with PKI-587 led to cell cycle arrest and induction of apoptosis and successfully suppressed activity of the direct mTORC1 target 4E-BP1, a crucial factor for tumor genesis only partially inhibited by everolimus. Gene expression analyses revealed relevant changes of RAS, MAPK, STAT, and PI3K pathway genes after treatment. Treatment-dependent and cell line-characteristic effects on AKT/Rb/E2F signaling regarding cell cycle control and apoptosis are extensively discussed in this paper.. PI3K/mTOR dual targeting is a promising new therapeutic approach in neuroendocrine tumor disease that should be evaluated in further clinical trials.

Topics: Antineoplastic Agents; Apoptosis; Catalytic Domain; Cell Cycle; Cell Line, Tumor; Cell Survival; Class I Phosphatidylinositol 3-Kinases; Everolimus; Gene Expression Regulation, Neoplastic; Humans; Intestinal Neoplasms; Membrane Potential, Mitochondrial; Mitogen-Activated Protein Kinase Kinases; Monomeric GTP-Binding Proteins; Morpholines; Neuroendocrine Tumors; Pancreatic Neoplasms; STAT Transcription Factors; Stomach Neoplasms; TOR Serine-Threonine Kinases; Triazines

The PI3K/AKT/mTOR pathway, which is aberrantly stimulated in many cancer cells, has emerged as a target for therapy. However, mTORC1/S6K also mediates negative feedback loops that attenuate upstream signaling. Suppression of these feedback loops opposes the growth-suppressive effects of mTOR inhibitors and leads to drug resistance. Here, we demonstrate that treatment of PANC-1 or MiaPaCa-2 pancreatic ductal adenocarcinoma (PDAC) cells with the dual PI3K/mTOR kinase inhibitor (PI3K/TOR-KI) BEZ235 blocked mTORC1/S6K activation (scored by S6 phosphorylation at Ser(240/244)), mTORC1/4E-BP1 (assayed by 4E-BP1 phosphorylation at Thr(37/46)), and mTORC2-mediated AKT phosphorylation at Ser(473), in a concentration-dependent manner. Strikingly, BEZ235 markedly enhanced the MEK/ERK pathway in a dose-dependent manner. Maximal ERK overactivation coincided with complete inhibition of phosphorylation of AKT and 4E-BP1. ERK overactivation was induced by other PI3K/TOR-KIs, including PKI-587 and GDC-0980. The MEK inhibitors U126 or PD0325901 prevented ERK overactivation induced by PI3K/TOR-KIs. The combination of BEZ235 and PD0325901 caused a more pronounced inhibition of cell growth than that produced by each inhibitor individually. Mechanistic studies assessing PI3K activity in single PDAC cells indicate that PI3K/TOR-KIs act through a PI3K-independent pathway. Doses of PI3K/TOR-KIs that enhanced MEK/ERK activation coincided with those that inhibited mTORC2-mediated AKT phosphorylation on Ser(473), suggesting a role of mTORC2. Knockdown of RICTOR via transfection of siRNA markedly attenuated the enhancing effect of BEZ235 on ERK phosphorylation. We propose that dual PI3K/mTOR inhibitors suppress a novel negative feedback loop mediated by mTORC2, thereby leading to enhanced MEK/ERK pathway activity in pancreatic cancer cells.

Topics: Bridged Bicyclo Compounds, Heterocyclic; Carrier Proteins; Cell Line, Tumor; Cell Proliferation; Drug Synergism; ErbB Receptors; Gene Knockdown Techniques; Humans; Imidazoles; MAP Kinase Signaling System; Mechanistic Target of Rapamycin Complex 2; Morpholines; Multiprotein Complexes; Pancreatic Neoplasms; Phosphoinositide-3 Kinase Inhibitors; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Pyrimidines; Quinolines; Rapamycin-Insensitive Companion of mTOR Protein; Receptor, IGF Type 1; Receptor, Insulin; Receptors, Somatomedin; TOR Serine-Threonine Kinases; Triazines