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A Mitochondria-K+ Channel Axis Is Suppressed in Cancer & Its Normalization Promotes Apoptosis and Inhibits Cancer Growth

ABSTRACT: The unique metabolic profile of most cancers (aerobic glycolysis) might confer apoptosis-resistance and be therapeutically targeted. Compared to normal cells, several human cancers have high mitochondrial membrane potential and low expression of the K+ channel Kv1.5, both contributing to apoptosis-resistance. Dichloroacetate (DCA), an inhibitor of the mitochondrial pyruvate dehydrogenase kinase (PDK), shifts metabolism from glycolysis to glucose oxidation, decreases mitochondrial membrane potential, increases mitochondrial-H2O2 and activates Kv channels in all cancer, but not normal cells; DCA upregulates Kv1.5 by an NFAT1-dependent mechanism. DCA induces apoptosis, decreases proliferation and tumor growth in vitro and in vivo, without apparent toxicity. Molecular inhibition of PDK2 by siRNA mimics DCA. The mitochondria-NFAT-Kv axis and PDK are important therapeutic targets in cancer; the orally available DCA is a novel selective anticancer agent. Keywords: treatment

ORGANISM(S): Homo sapiens

PROVIDER: GSE6014 | GEO | 2006/10/11

SECONDARY ACCESSION(S): PRJNA97815

REPOSITORIES: GEO

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Project description:The majority of human melanomas bears BRAF mutations and thus is treated with inhibitors of BRAF, such as vemurafenib. While patients with BRAF mutations often demonstrate an initial dramatic response to vemurafenib, relapse is extremely common. Thus, novel agents are needed for the treatment of these aggressive melanomas. Honokiol is a small molecule compound derived from Magnolia grandiflora that has activity against solid tumors and hematopoietic neoplasms. In order to increase the lipophilicity of honokiol, we have synthesized honokiol DCA, the dichloroacetate ester of honokiol. In addition, we synthesized a novel fluorinated honokiol analog, bis-trifluoromethyl-bis-(4-hydroxy-3-allylphenyl) methane (hexafluoro). Both compounds exhibited activity against A375 melanoma in vivo, but honokiol DCA was more active. Gene arrays comparing treated with vehicle control tumors demonstrated induction of the respiratory enzyme succinate dehydrogenase B (SDHB) by treatment, suggesting that our honokiol analogs induce respiration in vivo. We then examined its effect against a pair of melanomas, LM36 and LM36R, in which LM36R differs from LM36 in that LM36R has acquired vemurafenib resistance. Honokiol DCA demonstrated in vivo activity against LM36R (vemurafenib resistant) but not against parental LM36. Honokiol DCA and hexafluoro inhibited the phosphorylation of DRP1, thus stimulating a phenotype suggestive of respiration through mitochondrial normalization. Honokiol DCA may act in vemurafenib resistant melanomas to increase both respiration and reactive oxygen generation, leading to activity against aggressive melanoma in vivo. Tumors from animals treated with control vehicle, honokiol DCA, and hexafluoro were harvested and snapped-frozen in liquid nitrogen until RNA Extraction. RNA extraction was performed according to the Qiagen RNeasy kit. RNA samples were then submitted to Emory Universityâs Intergrated Genomics Core for RNA quality analysis and gene expression assay. Gene expression analysis was performed using an Illumina HumanHT-12 v3 Expression Bead Chip and Gene Expression Module of Illuminaâs GenomeStudio Software package (v2011.1, Illumina).

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A Mitochondria-K+ Channel Axis Is Suppressed in Cancer & Its Normalization Promotes Apoptosis and Inhibits Cancer Growth

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