mezerein and Neoplasms

Phytochemical investigation of whole plants of Euphorbia pilosa led to the isolation and identification of two new daphnane-diterpenoid glucosides, euphopilosides A and B (1 and 2, resp.), and a new ent-abietane, euphopilolide (3), together with eight known compounds. Compounds 1 and 2 are the first daphnane-type diterpenoid glycosides. Their structures were elucidated by a combination of 1D- and 2D-NMR, and MS analyses, and acid hydrolysis. Compounds 1-9 were evaluated for their in vitro cytotoxicities against five human tumor cell lines, HL-60, SMMC-7721, A-549, MCF-7, and SW-480. Compound 7 showed moderate inhibitory activity against all five cell lines.

Topics: Antineoplastic Agents, Phytogenic; Cell Line, Tumor; Diterpenes; Euphorbia; Glucosides; Humans; Neoplasms

Abnormalities in cellular differentiation are frequent occurrences in human cancers. Treatment of human melanoma cells with recombinant fibroblast interferon (IFN-beta) and the protein kinase C activator mezerein (MEZ) results in an irreversible loss in growth potential, suppression of tumorigenic properties and induction of terminal cell differentiation. Subtraction hybridization identified melanoma differentiation associated gene-7 (mda-7), as a gene induced during these physiological changes in human melanoma cells. Ectopic expression of mda-7 by means of a replication defective adenovirus results in growth suppression and induction of apoptosis in a broad spectrum of additional cancers, including melanoma, glioblastoma multiforme, osteosarcoma and carcinomas of the breast, cervix, colon, lung, nasopharynx and prostate. In contrast, no apparent harmful effects occur when mda-7 is expressed in normal epithelial or fibroblast cells. Human clones of mda-7 were isolated and its organization resolved in terms of intron/exon structure and chromosomal localization. Hu-mda-7 encompasses seven exons and six introns and encodes a protein with a predicted size of 23.8 kDa, consisting of 206 amino acids. Hu-mda-7 mRNA is stably expressed in the thymus, spleen and peripheral blood leukocytes. De novo mda-7 mRNA expression is also detected in human melanocytes and expression is inducible in cells of melanocyte/melanoma lineage and in certain normal and cancer cell types following treatment with a combination of IFN-beta plus MEZ. Mda-7 expression is also induced during megakaryocyte differentiation induced in human hematopoietic cells by treatment with TPA (12-O-tetradecanoyl phorbol-13-acetate). In contrast, de novo expression of mda-7 is not detected nor is it inducible by IFN-beta+MEZ in a spectrum of additional normal and cancer cells. No correlation was observed between induction of mda-7 mRNA expression and growth suppression following treatment with IFN-beta+MEZ and induction of endogenous mda-7 mRNA by combination treatment did not result in significant intracellular MDA-7 protein. Radiation hybrid mapping assigned the mda-7 gene to human chromosome 1q, at 1q 32.2 to 1q41, an area containing a cluster of genes associated with the IL-10 family of cytokines. Mda-7 represents a differentiation, growth and apoptosis associated gene with potential utility for the gene-based therapy of diverse human cancers.

Topics: Antigens, Neoplasm; Apoptosis; Base Sequence; Carcinoma; Cell Differentiation; Cell Division; Chromosomes, Human, Pair 1; Cloning, Molecular; Dimethyl Sulfoxide; Diterpenes; Female; Gene Expression Regulation, Neoplastic; Genes; Genes, Tumor Suppressor; Glioblastoma; Growth Substances; HL-60 Cells; Humans; Interferon Type I; Interleukins; K562 Cells; Male; Melanocytes; Melanoma; Molecular Sequence Data; Molecular Weight; Neoplasm Proteins; Neoplasms; Organ Specificity; Osteosarcoma; Recombinant Fusion Proteins; Recombinant Proteins; RNA, Messenger; RNA, Neoplasm; Terpenes; Tetradecanoylphorbol Acetate; Transfection; Tumor Cells, Cultured

The effect of topical application of PGE on induction of ODC in mouse epidermis was measured. When direct induction of ODC by TPA was blocked by also applying indomethacin, maximum ODC activity occurred only when PGE was applied simultaneously with TPA 4 1/2 hr before killing of the mice. If either TPA or PGE was applied at other times, ODC activity decreased substantially. Induction of ODC by mezerein was blocked by indomethacin but restored by PGE, as was observed with TPA, but induction by ethyl phenylpropiolate was not affected by indomethacin or PGE. DMBA did not cause a consistent increase in ODC activity, nor was its inductive action affected by indomethacin or PGE. However, another weak inducer, acetic acid, exhibited elevated ODC activity when PGE was also applied. Inhibition by topical retinoic acid of ODC induction by TPA was partially overcome in a dose-response fashion by PGE. The results indicate that at least 2 events, elevation of PGE and another independent event, are required for induction of ODC activity. It appears that TPA causes at least 4 independent events essential for tumor promotion. A model for the events in the 2-stage tumor promotion model is proposed.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Alprostadil; Animals; Diterpenes; Enzyme Induction; Female; Indomethacin; Mice; Mice, Inbred Strains; Models, Biological; Neoplasms; Ornithine Decarboxylase; Phorbols; Terpenes; Tetradecanoylphorbol Acetate; Tretinoin

The present study was undertaken to determine the effect of the potent tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA) on gamma radiation-induced DNA repair in resting (Go) lymphocytes. Mezerein, a non-promoter but a co-mitogen in lymphocytes, was used as a control agent. It was previously proposed that a possible mechanism for the action of tumor promoters was through the inhibition of DNA repair processes. Our results indicate that TPA does not inhibit DNA repair following gamma irradiation of Go lymphocytes. These data support the hypothesis that the tumor promoting ability of TPA is not a result of impaired repair of potentially mutagenic lesions in DNA.

Topics: Animals; Cattle; Cells, Cultured; Centrifugation, Density Gradient; Dimethyl Sulfoxide; Diterpenes; DNA; DNA Repair; Gamma Rays; Interphase; Lymphocytes; Neoplasms; Phorbol Esters; Phorbols; Terpenes; Tetradecanoylphorbol Acetate