TPA induced inhibition

Classical examples of anti-inflammatory Asteraceae are Arnica montana and Calendula officinalis, both used in European medicine to treat bruises and contusions. There is an expanding body of evidences to suggest that Asteraceae could be a useful source of anti-inflammatories, such as sesquiterpene lactones and/or triterpene alcohols, the latter being known to inhibit 12-O-tetra-decanoylphorbol-13-acetate (TPA)-induced inflammation in mice as efficiently as commercial indomethacine by possible inhibition of phospholipase A2 (10). 

Phosphorylation of H3 is not limited to mitosis and also occurs in G1 phase of the cell cycle. Activation of the Ras-Raf-MEK-ERK signal transduction pathway and/or of the p38 stress kinase pathway when cells are treated with epidermal growth factor (EGF), 12-G-tetradecanoylphorbol-13-acetate (TPA), anesomycin, okadiac acid, and stresses such as UV irradiation induces the rapid phosphorylation of H3 at Ser-10 and/or Ser-28 [68-72] (Figs. 5 and 6). Inhibition of the MEK1,2 activity with PD98059 prevents the activation of ERK and TPA-induced H3... 

The control of cell numbers is regulated by cell proliferation, differentiation and apoptosis. Increased proliferation and/or decreased apoptosis result in neoplasia. In addition to inhibition of proliferation or induction of differentiation, the modulation of apoptosis can be employed for treatment for cancer. Several anticancer agents in use are potent inducers of apoptosis (Dive and Hickman, 1991 Fisher, 1994). Tumor promotion may result in decreased apoptosis. Because PKC activation by TPA induces carcinogenesis, it seems that PKC may be involved in apoptosis. There are many reports on the effects of PKC on apoptosis. However, the results are very controversial. Here an overview of these data is presented. 

Overexpression of PKC in U937 histiocytic lymphoma cells increased expression of PKCa and p isoforms. In response to TPA, parental U937 cells displayed growth arrest and differentiated into a monocyte/macrophage-like cell line, while PKC overexpressing cells underwent death. The abUity of GF109203X to inhibit TPA-induced cell death suggested that activation of a conventional isoform was necessary to induce apoptosis (de Vente et al., 1995). Activation of PKC enhanced and down-modulation of PKC activity reduced apoptosis of neuronal cells (Mailhos et al., 1994). Ceramide, an activator of PKC is an inducer of apoptosis (Muller et al, 1995 Hannun, 1998, Obeid et al., 1993). 

Epstein-Barr virus early antigen induction. Methanol extract of the dried leaf, in cell culture at a concentration of 1 pg/mL, was inactive. The assay was designed for tumor-promoting activity . Two diastere-oisomers of 2,7,1 l-cembratriene-4,6-diol (a- and 3-CBT) from the neutral fractions of cigarette smoke condensate, in Raji cells, produced potent inhibitory effects on the induction of Epstein-Barr virus (EBV)-EA by 12-0-tetradecanoylphorbol-13-acetate (TPA). The doses of a- and P-CBT required for 50% inhibition of EBV-EA induction by TPA were 7.7 and 6.7 mg/mL, respectively. Application of a- and P-CBT to mouse skin before treatment with TPA, inhibited TPA-induced ornithine decarboxylase activity in a dose-dependent manner. Application of 16.5 pM/mouse of a- and p-CBT resulted... 

Aburatubolactam A (91) and C (92) were isolated from the culture broth of Streptomyces sp recovered from a mollusk. X-ray diffraction studies established the structure of aburatubolactam A which was reported to inhibit TPA-induced superoxide anion generation by human neutrophils [149]. Aburatubolactam C appears to be cytotoxic for various proliferating tumor cells of human and murine origin (0.3-5.8 ig/ml) via apoptotic DNA fragmentation [150,151]. 

Sarcophytols A (46) and B (47) are simple cembranoids isolated from the Okinawan soft coral S. glaucum and have been reported to possess potent inhibitory activities against various classes of tumor promoters.70 71 Sarcophytol A (46) mediated dose-dependent diminution of 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced transformation of JB6 cells.72 When evaluated for potential to inhibit TPA-induced JB6 cell transformation, several of the sarcophine metabolites (48 to 58) mediated inhibitory responses greater than sarcophytol A (46) or sarcophine (45), most notably 7a-hydroxy-y8(19) deepoxysarcophine (50), which was comparable to 13-cz s-retinoic acid. These studies provide a basis for further development of novel furanocembranoids as anticancer agents. 

Skin 1 Inhibition of 7,12-dimethylbenz[a Janthracene (DMBA 2)/TPA induced skin tumors (Topical application) [8,3739-42]... 

Skin 11 Inhibition of DMBA/TPA induced skin tumors (Oral application) [43]... 

For the highly inhibitive compounds in the TPA-induced inflammatory assay, we evaluated their antitumor-promoting activity by a standard initiation-promotion protocol [Fig. (3)] [37,40]. Initiation was achieved by a single application of 50 pg of DMBA (2), a well known tumor initiator, to the skin of backs of 8-week-old female ICR mice. From one week after initiation, 1 pg of TPA (1) was applied twice a week until week 20. The test compound (2.0 or 0.2 pM) dissolved in acetone-dimethyl sulfoxide (DMSO) (9 1, 100 pi) was applied 30 min before each TPA treatment. Groups of 15 mice were used. The number of tumors was counted weekly. 

Induction of epidermal ODC is a characteristic biochemical alteration elicited by TPA and may be representative of the effects of phorbol esters with strong tumor promoting activity [81]. A single application of TPA (5 pg) resulted in a substantial and transient increase of epidermal ODC activity in mice with a peak at about 4 h after TPA treatment, and the induction was potently inhibited by treatment (5 pM) of the mouse skin with sitosterol (33, 65% inhibition) and three lupane type triterpenoids betulin (255 79%), betulinic acid (257 89%), and lupeol (264,96%) [30]. The inhibitory effect on TPA-induced ODC activity was further reported for ursolic acid (210 45% inhibition at 2.0 pM/5nM of TPA) [31]. 

Huang et al. [70] have evaluated the effects of chlorogenic acids on tumor promotion in an animal study using CD-I mice. Chlorogenic, caffeic and ferulic acids inhibit the induction of ornithine decarboxylase by 12-O-tetradecanoylphorbol-13-acetate (TPA). TPA-mediated DNA synthesis has been weakly inhibited, but TPA-induced skin tumor promotion has been markedly inhibited by these compounds. 

Studies have also demonstrated curcumin s therapeutic properties in vivo. In 6-week-old mice, the administration of a 2% curcumin diet via oral gavage resulted in a 53% reduction in lymphomas and leukemias. When topically applied prior to the administration of TPA in mice, curcumin down-regulated TPA-induced NF-kB and AP-1. It was also showed that oral administration of curcumin (50-200 mg/kg) inhibits the development of leukemia (HL 60) cell-induced xenografts in nude mice [Anand et al., 2008]. 

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