Chemoprevention of skin cancer: effect of Lawsonia inermis L. (Henna) leaf powder and its pigment artifact, lawsone in the Epstein- Barr virus early antigen activation assay and in two-stage mouse skin carcinogenesis models.

In continuation of our studies with chemoprevention potential of plant-derived naphthoquinone derivatives, leaf powder of the medicinal plant Lawsonia inermis L, commonly known as 'henna', was evaluated by its inhibition of the Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Lawsone (2-hydroxy- 1,4-naphthoquinone), the reddish orange pigment artifact formed during the extraction or preparation of the dye from henna leaves and believed to be the active component, was also assessed in this in vitro assay. Both showed a profound inhibition (>88%) of EBV-EA activation. In the in vivo two-stage mouse skin carcinogenesis study using UV-B radiation for initiation and TPA for tumor promotion, oral feeding of henna (0.0025%) in drinking water ad libitum decreased tumor incidence by 66% and multiplicity by 40% when compared to the positive control at 10 weeks of treatment. Similarly, in the above mouse model, orally fed lawsone (0.0025%) decreased tumor incidence by 72% and multiplicity by 50%. The tumor inhibitory trend continued throughout the 20-week test period. Similar antitumor activities were observed when henna (0.5 mg/ml) was applied topically on the back skin in the UV-B initiated, TPA promoted and peroxynitrite initiated, TPA promoted mouse skin carcinogenesis models. Topically applied lawsone (0.015 mg/ml) also exhibited similar protection against tumor formation in the 7,12-dimtehylbenz(a)anthracene induced and TPA promoted skin cancer in mice. Also, there was a delay of 1 to 2 weeks in tumor appearance in both henna and lawsone treated groups compared to control in all three test models. This study ascertains the skin cancer chemopreventive activity of henna leaf powder and lawsone when administered by either oral (through drinking water) or topical (by application on the back skin) routes. Further, it emphasizes the need for the evaluation of these henna-derived green chemopreventive candidates in combination with currently used sunscreen agents for complementary anticancer potential against UV-induced skin carcinogenesis.

Salvianolic acid B inhibits growth of head and neck squamous cell carcinoma in vitro and in vivo via cyclooxygenase-2 and apoptotic pathways.

Overexpression of cyclooxygenase-2 (COX-2) in oral mucosa has been associated with increased risk of head and neck squamous cell carcinoma (HNSCC). Celecoxib is a nonsteroidal anti-inflammatory drug, which inhibits COX-2 but not COX-1. This selective COX-2 inhibitor holds promise as a cancer preventive agent. Concerns about cardiotoxicity of celecoxib, limits its use in long-term chemoprevention and therapy. Salvianolic acid B (Sal-B) is a leading bioactive component of Salvia miltiorrhiza Bge, which is used for treating neoplastic and chronic inflammatory diseases in China. The purpose of this study was to investigate the mechanisms by which Sal-B inhibits HNSCC growth. Sal-B was isolated from S. miltiorrhiza Bge by solvent extraction followed by 2 chromatographic steps. Pharmacological activity of Sal-B was assessed in HNSCC and other cell lines by estimating COX-2 expression, cell viability and caspase-dependent apoptosis. Sal-B inhibited growth of HNSCC JHU-022 and JHU-013 cells with IC(50) of 18 and 50 microM, respectively. Nude mice with HNSCC solid tumor xenografts were treated with Sal-B (80 mg/kg/day) or celecoxib (5 mg/kg/day) for 25 days to investigate in vivo effects of the COX-2 inhibitors. Tumor volumes in Sal-B treated group were significantly lower than those in celecoxib treated or untreated control groups (p < 0.05). Sal-B inhibited COX-2 expression in cultured HNSCC cells and in HNSCC cells isolated from tumor xenografts. Sal-B also caused dose-dependent inhibition of prostaglandin E(2) synthesis, either with or without lipopolysaccharide stimulation. Taken together, Sal-B shows promise as a COX-2 targeted anticancer agent for HNSCC prevention and treatment.

Chemoprevention of DMBA-induced UV-B promoted, NOR-1-induced TPA promoted skin carcinogenesis, and DEN-induced phenobarbital promoted liver tumors in mice by extract of beetroot.

Our previous studies identified the extract of Beta vulgaris (beetroot), commercially also known as betanin, as a potent cancer chemopreventive agent in both in vitro Epstein-Barr early antigen activation assay and in an in vivo two-stage mouse lung and skin carcinogenesis. To explore this issue further, we have now investigated its cancer chemopreventive potentials in three different chemical carcinogen initiation-promotion experimental tumor models in mice. Following tumor initiation with 390 nmol of 7,12-dimethylbenz(a)anthracene (DMBA) in 100 microl of acetone, the mouse skin tumor promotion with 3430 J/m(2) of ultraviolet light-B (UV-B) as well as splenomegaly was significantly inhibited by oral administration of 0.0025% betanin. At the same dose, betanin also afforded significant protection in the mouse skin cancer model following the topical application of 390 nmol of (+/-)-(E)-4-methyl-2-[(E)-hydroxyamino]-5-nitro-6-methoxy-3-hexanamide (NOR-1) in 100 microl of acetone and promoted by topical administration of 1.7 nmol of 12-O-tetradecanoylphorbol-13-acetate (TPA). In the two-stage model of hepatocarcinogenesis in mice with N-nitrosodiethylamine (DEN, 30 mg/kg) as the initiator and phenobarbital as the promoter, oral administration of 0.0025% betanin also showed a very significant inhibition of both the incidence and multiplicity of the liver tumors. These findings along with our initial reports suggest that betanin which is a regularly consumed natural product colorant is an effective cancer chemopreventive agent in mice. The most interesting observation is that the cancer chemopreventive effect was exhibited at a very low dose used in the study and thus indicating that beetroot warrants more attention for possible human applications in the control of malignancy.

Inhibitory effect of herbal remedies on 12-O-tetradecanoylphorbol-13-acetate-promoted Epstein-Barr virus early antigen activation.

For the past several years we have been evaluating natural products as potential cancer chemopreventive agents in a short term in vitro assay involving Epstein--Barr virus early antigen (EBV-EA) activation in Raji cells promoted by phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA). Because of the current interest in the use of herbal remedies, we considered examining them for their cancer chemopreventive activities, using their extracts with a view to uncovering such benefits (if any) these remedies might possess. Thirty-six extracts of 32 herbs belonging to 27 families in use as herbal remedies including those of gingko, black cohosh, echinacea, kava-kava, saw palmetto, turmeric, angelica, wild yam, cat's claw, passion flower, muira puama, feverfew, blueberry, chasteberry, licorice, nettle, golden seal, pygeum, ginger, valerian and hops were prepared and evaluated. Turmeric at a concentration of 10 microg x ml (-1)exhibited the most potent anti-EBV-EA activity, which is ten times more than passionflower, that is next in the order of activity. At the concentration level of 100 microg ml (-1), several of the herbal remedies tested inhibited the EBV-EA in Raji cells exposed to the tumor promoter TPA (32 pM) by more than 90%. We also report for the first time the activities of 16 new medicinal plants as potential cancer chemopreventive agents. Since inhibitors of EBV-EA promoted by TPA in vitro have been shown to be effective anti-tumor promoting agents in laboratory animal models, our results indicate new and potential applications of these herbal remedies as cancer chemopreventive agents since they are already in clinical use in the human population.