largazole and Colonic-Neoplasms

Combined phylogenetic and HPLC-MS-based natural products dereplication methods aimed at identifying cyanobacterial collections containing the potent cytotoxins largazole, dolastatin 10, and symplostatin 1 were developed. The profiling of the phylogeny, chemical space, and antiproliferative activity of cyanobacterial collections served to streamline the prioritization of samples for the discovery of new secondary metabolites. The dereplication methods highlighted the biosynthetic potential and combinatorial pharmacology employed by marine cyanobacteria. We found that largazole was always coproduced with dolastatin 10 or with symplostatin 1 and consequently tested combinations of these agents against colon cancer cells. Combinatorial regimens of largazole and dolastatin 10 aimed at curbing the growth of HCT116 cancer cells showed cooperative activity.

Topics: Biological Products; Chromatography, High Pressure Liquid; Colonic Neoplasms; Cyanobacteria; Cytotoxins; Depsipeptides; HCT116 Cells; Humans; Marine Biology; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Phylogeny; Thiazoles

Extensive evidence suggests that dysregulation of histone lysine acetylation is intimately linked with the development of cancer in epigenetic level. Histone acetylation on lysine is regulated mainly by the "pencil"--Histone acetyltransferases (HATs) and the "eraser"--Histone deacetylases HDACs. Dramatic elevation of global histone deacetylation is considered as a biomarker for cancer. Therefore, current antitumor drug design often targets HDACs, inhibiting overexpressed HDAC in tumor cells with natural or synthesized small molecules like largazole. Recently, a novel largazole derivative (largazole-7) was designed and prepared by replacement of Val 1 with tyrosine, and this modification increases selectivity toward human cancer cells over normal cells more than 100-fold. However, it is unclear about the dynamic level of histone acetylation under the treatment of this drug. It is also unclear whether the other modifications are also affected by largazole-7 treatment. Therefore, a global mapping of modifications on the histone proteins of cancer cell line treated by this drug may be of great benefit to elucidating its molecular mechanisms and exploring its potent as an antitumor drug. To realize the goal, we combined stable isotope labeling by amino acids in cell culture (SILAC) and high resolution MS for comprehensive identification and quantitative analysis of histone lysine acetylation and other modifications of Human Colon Cancer Cells (HCT-116) with and without treatment of largazole-7. In this analysis, we identified 68 histone PTMs in 38 sites on core histones, including lysine acetylation, methylation and butyrylation, a novel lysine modification. Further quantitative analysis not only discovered the global increased acetylated lysines, but also observed the changes of abundance of lysine methylation and butyrylation under stimulation of the drug. To our knowledge, it is the first report that regulation of largazole-7 against lysine butyrylation. Our study expands the catalog of histone marks in cancer, and provides an approach for understanding the known and new epigenetic marks under treatment of drugs.

Topics: Acetylation; Antineoplastic Agents; Colonic Neoplasms; Depsipeptides; Epigenesis, Genetic; HCT116 Cells; Histone Deacetylase Inhibitors; Histone Deacetylases; Histones; Humans; Isotope Labeling; Thiazoles

Histone deacetylases (HDACs) are validated targets for anticancer therapy as attested by the approval of suberoylanilide hydroxamic acid (SAHA) and romidepsin (FK228) for treating cutaneous T cell lymphoma. We recently described the bioassay-guided isolation, structure determination, synthesis, and target identification of largazole, a marine-derived antiproliferative natural product that is a prodrug that releases a potent HDAC inhibitor, largazole thiol. Here, we characterize the anticancer activity of largazole by using in vitro and in vivo cancer models. Screening against the National Cancer Institute's 60 cell lines revealed that largazole is particularly active against several colon cancer cell types. Consequently, we tested largazole, along with several synthetic analogs, for HDAC inhibition in human HCT116 colon cancer cells. Enzyme inhibition strongly correlated with the growth inhibitory effects, and differential activity of largazole analogs was rationalized by molecular docking to an HDAC1 homology model. Comparative genomewide transcript profiling revealed a close overlap of genes that are regulated by largazole, FK228, and SAHA. Several of these genes can be related to largazole's ability to induce cell cycle arrest and apoptosis. Stability studies suggested reasonable bioavailability of the active species, largazole thiol. We established that largazole inhibits HDACs in tumor tissue in vivo by using a human HCT116 xenograft mouse model. Largazole strongly stimulated histone hyperacetylation in the tumor, showed efficacy in inhibiting tumor growth, and induced apoptosis in the tumor. This effect probably is mediated by the modulation of levels of cell cycle regulators, antagonism of the AKT pathway through insulin receptor substrate 1 down-regulation, and reduction of epidermal growth factor receptor levels.

Topics: Animals; Antineoplastic Agents; Apoptosis; Cell Cycle; Cell Line, Tumor; Cell Survival; Chromatography, High Pressure Liquid; Colonic Neoplasms; Depsipeptides; Down-Regulation; Drug Stability; Female; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Histone Deacetylase Inhibitors; Histone Deacetylases; Humans; Immunohistochemistry; Mass Spectrometry; Mice; Mice, Nude; Molecular Structure; Oligonucleotide Array Sequence Analysis; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; Thiazoles; Xenograft Model Antitumor Assays