fk-866 and Glioblastoma

The aggressive primary brain tumor glioblastoma (GBM) is characterized by aberrant metabolism that fuels its malignant phenotype. Diverse genetic subtypes of malignant glioma are sensitive to selective inhibition of the NAD

Topics: Acrylamides; Animals; Autophagy; B7-H1 Antigen; Brain Neoplasms; CD4-Positive T-Lymphocytes; CD8-Positive T-Lymphocytes; Cell Movement; Cyanides; Cytokines; Delayed-Action Preparations; Drug Carriers; Glioblastoma; Guanidines; Humans; Injections, Intralesional; Macrophages; Membrane Proteins; Mice; NAD; Nicotinamide Phosphoribosyltransferase; Piperidines; Polymers; RNA, Messenger; Signal Transduction; Tumor Microenvironment; Up-Regulation

Overcoming temozolomide (TMZ) resistance is a great challenge in glioblastoma (GBM) treatment. Nicotinamide phosphoribosyltransferase (NAMPT) is a rate-limiting enzyme in the biosynthesis of nicotinamide adenine dinucleotide and has a crucial role in cancer cell metabolism. In this study, we investigated whether FK866 and CHS828, two specific NAMPT inhibitors, could sensitize GBM cells to TMZ. Low doses of FK866 and CHS828 (5 nM and 10 nM, resp.) alone did not significantly decrease cell viability in U251-MG and T98 GBM cells. However, they significantly increased the antitumor action of TMZ in these cells. In U251-MG cells, administration of NAMPT inhibitors increased the TMZ (100 

Topics: Acrylamides; Anthracenes; Apoptosis; Caspases; Cell Line, Tumor; Cell Survival; Cytokines; Dacarbazine; Drug Synergism; Gene Expression Regulation, Neoplastic; Glioblastoma; Humans; MAP Kinase Kinase 4; Mitogen-Activated Protein Kinase 8; Nicotinamide Phosphoribosyltransferase; Piperidines; Reactive Oxygen Species; Signal Transduction; Temozolomide; Tocopherols

APO866 is a potent inhibitor of nicotinamide phosphoribosyltransferase (NAMPT), and inhibits nicotinamide adenine dinucleotide (NAD) synthesis. Our previous study showed that APO866 inhibits the proliferation of C6 glioblastoma cells, but failed to induce apoptosis. Since APO866 inhibits cellular metabolism and such metabolic stress is closely related with autophagy, thus we determined whether APO866 can induce autophagy in C6 glioblastoma cells and whether the autophagy induced by APO866 is pro-death or pro-survival. Using LC3 immunofluorescence imaging and transmission electron microscopy detection, we found that APO866 at 1-100 nM induced autophagy in C6 glioblastoma cells. APO866 at 1 nM mainly induced initial autophagic vacuoles. Whereas APO866 at 100 nM induced degrading autophagic vacuoles, as well as induced nuclei malformation and mitochondria swelling. In addition, APO866 concentration-dependently decreased the cell viability of C6 glioblastoma cells, and this effect was attenuated by autophagy inhibitors, including 3-methyladenine and LY294002. APO866 concentration-dependently decreased intracellular NAD level. Interestingly, APO866 at 1 nM slightly decreased intracellular NAD level, but dramatically increased autophagy-positive cells. The dramatical cell viability decreasing required the decreasing of intracellular NAD level to a very low threshold. Thus, our results indicated that APO866 induced pro-death autophagy in C6 glioblastoma cells by decreasing intracellular NAD, and low concentration of APO866 can be used as an autophagy inducer in autophagic-death sensitive glioblastoma.

Topics: Acrylamides; Animals; Autophagy; Cell Death; Cell Line, Tumor; Cell Proliferation; Enzyme Inhibitors; Glioblastoma; NAD; Nicotinamide Phosphoribosyltransferase; Piperidines; Rats; Vacuoles

Nicotinamide phosphoribosyltransferase (NAMPT) is a key enzyme in the salvaging pathway for the synthesis of nicotinamide adenine dinucleotide (NAD) that is involved in cell metabolism and proliferation. NAMPT is normally absent in astrocyte but highly expressed in glioblastoma, suggesting that it may promote cell survival through synthesizing more NAD. In this report, we evaluated the effect of APO866, a potent inhibitor of NAMPT against C6 glioblastoma. We found that APO866 inhibited the growth of C6 glioblastoma cells with IC(50) in nano-molar range. APO866 depleted intracellular NAD, caused marked inhibition of ERK activation and induced G2/M cell-cycle arrest. The effects by APO866 were abrogated by nicotinamide mononucleotide (NMN), the direct product of NAMPT. Administration of U0126, an ERK1/2 inhibitor, inhibited cell growth but displayed no synergistic effect with APO866. Taken together, our results indicated that APO866 is a potent growth inhibitor against glioblastoma through targeting NAMPT.

Topics: Acrylamides; Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; Cell Survival; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Inhibitors; G2 Phase Cell Cycle Checkpoints; Gene Expression Regulation, Neoplastic; Glioblastoma; Humans; Intracellular Space; M Phase Cell Cycle Checkpoints; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; NAD; Nicotinamide Phosphoribosyltransferase; Piperidines; Rats

Glioblastoma multiforme (GBM) is a devastating brain tumor with poor prognosis and low median survival time. Standard treatment includes radiation and chemotherapy with the DNA alkylating agent temozolomide (TMZ). However, a large percentage of tumors are resistant to the cytotoxic effects of the TMZ-induced DNA lesion O(6)-methylguanine due to elevated expression of the repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) or a defect in the mismatch repair (MMR) pathway. Although a majority of the TMZ-induced lesions (N7-methylguanine and N3-methyladenine) are base excision repair (BER) substrates, these DNA lesions are also readily repaired. However, blocking BER can enhance response to TMZ and therefore the BER pathway has emerged as an attractive target for reversing TMZ resistance. Our lab has recently reported that inhibition of BER leads to the accumulation of repair intermediates that induce energy depletion-mediated cell death via hyperactivation of poly(ADP-ribose) polymerase. On the basis of our observation that TMZ-induced cell death via BER inhibition is dependent on the availability of nicotinamide adenine dinucleotide (NAD(+)), we have hypothesized that combined BER and NAD(+) biosynthesis inhibition will increase TMZ efficacy in glioblastoma cell lines greater than BER inhibition alone. Importantly, we find that the combination of BER and NAD(+) biosynthesis inhibition significantly sensitizes glioma cells with elevated expression of MGMT and those deficient in MMR, two genotypes normally associated with TMZ resistance. Dual targeting of these two interacting pathways (DNA repair and NAD(+) biosynthesis) may prove to be an effective treatment combination for patients with resistant and recurrent GBM.

Topics: Acrylamides; Adenosine Triphosphate; Antineoplastic Agents, Alkylating; Cell Line, Tumor; Cell Survival; Dacarbazine; DNA Glycosylases; DNA Repair; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Drug Synergism; Glioblastoma; Humans; Hydroxylamines; Immunoblotting; Methyl Methanesulfonate; NAD; Piperidines; Poly(ADP-ribose) Polymerases; RNA Interference; Temozolomide