Virus Early Antigen Activation Assay Research Articles

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.

Cancer preventive agents 10. Prenylated dehydrozingerone analogs as potent chemopreventive agents

Dehydrozingerone analogs and related compounds were screened as potential antitumor promoters by using the in vitro short-term 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced Epstein–Barr virus early antigen activation assay. Among the 40 synthesized compounds, the prenylated analogs 16 and 34–36 showed the most significant and promising activity (100% inhibition of activation at 1 × 103 mol ratio/TPA, and 82–80%, 37–35%, and 13–11% inhibition at 5 × 102, 1 × 102, and 1 × 10 mol ratio/TPA, respectively) in this screening. Their activity profiles were comparable to those of the reference standard curcumin. While a prenyl moiety conferred potent chemopreventive activity, an extended prenyl unit such as a farnesyl moiety did not improve activity. Because in vitro inhibitory effects in this assay generally correlate well with in vivo inhibitory effects on tumor promotion, our results strongly suggested that prenylated 16 and 34–36 are likely to be promising antitumor promoters.

Chemopreventive activities of etodolac and oxyphenbutazone against mouse skin carcinogenesis

Previous cancer chemoprevention studies have demonstrated that the non-steroidal anti-inflammatory drugs (NSAIDs) can be effective in suppressing the development of various human malignancies. Recently we identified the possible anti-tumor promoting potentials of 14 new NSAIDs in the Epstein–Barr virus early antigen activation assay induced by 12- O-tetradecanoylphorbol-13-acetate (TPA). In this study we report the inhibition of 7,12-dimethylbenz (a) anthracene (DMBA) induced two-stage mouse skin carcinogenesis by etodolac (ETD), one of the most potent NSAIDs identified in our in vitro cancer chemopreventive screening of this group of drugs. Topical administration of ETD at a very low dose of 85 nmol showed a significant decrease in both tumor incidence and burden. This effect is also accompanied by a delay in the tumor latency period. Since ETD showed potent chemopreventive activity in both in vitro and in vivo studies, it warrants prompt consideration for trial in humans as a potential cancer chemopreventive agent. We also investigated oxyphenbutazone (OPB) another commonly used NSAID for its cancer chemopreventive effect on peroxynitrite (PN) induced-TPA promoted skin tumors in the mouse. Following tumor initiation with 390 nmol of PN, the skin tumor promotion with 1.7 nmol of TPA was significantly inhibited by oral administration of 0.0025% OPB. The results demonstrate that OPB is a potent cancer chemopreventive agent in the highly sensitive in vivo mouse test model we used.

Chemopreventive effect of Lawsonia inermis L. powder in the Epstein-Barr virus early antigen activation assay and the mouse skin two-stage carcinogenesis

Chemopreventive effect of Lawsonia inermis L. powder in the Epstein-Barr virus early antigen activation assay and the mouse skin two-stage carcinogenesis

Chemopreventive effect of resveratrol, sesamol, sesame oil and sunflower oil in the epstein–barr virus early antigen activation assay and the mouse skin two-stage carcinogenesis

Resveratrol, sesamol, sesame oil and sunflower oil are known natural dietary components with intrinsic cancer chemopreventive potentials. As a part of our study of dietary constituents as potential cancer chemopreventive agents, we have assessed the anti-cancer potentials of these products in the promotion stage of cancer development employing the in vitro Epstein–Barr virus early antigen activation assay induced by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA). Further, we studied the activities of these compounds in the brine shrimp cytotoxicity assay as well as on the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging bioassay with a view to comparing some of the mechanisms of their anti-cancer activity. Finally, we compared the observed chemoprotective capabilities of the four products in the in vivo 7,12 dimethylbenz(a)anthracene initiated and TPA-promoted mouse skin two-stage carcinogenesis protocols. All the products tested showed a profound inhibitory effect on the Epstein–Barr virus early antigen induction using Raji cells. Comparatively, sesame oil was the most potent followed by sesamol and then resveratrol. Only sesamol and resveratrol showed a remarkable cytotoxic activity in the brine shrimp lethality assays as well as profound free radical scavenging activity in the DPPH bioassay. In both test systems, sesamol exhibited a more remarkable activity than resveratrol while sesame oil and sunflower oil did not exhibit any appreciable activity even at the highest concentrations tested (4000 μ g ml−1 ). In our in vivo assay at a 50-fold molar ratio to TPA, sesamol offered 50% reduction in mouse skin papillomas at 20 weeks after promotion with TPA. Under an identical molar ratio to TPA, resveratrol offered a 60% reduction in the papillomas in mouse at 20 weeks. Thus sesamol seems to be an almost equally potent chemopreventive agent. Sesame oil and sunflower oil offered 20 and 40% protection, respectively, in the mouse skin tumor model. The anti-oxidant capabilities of these compounds could not solely explain the observed anti-cancer characteristics. Resveratrol is present in grapes. Sesamol, a constituent of sesame oil and sunflower oil are regularly consumed dietary natural products. The observed chemopreventive effect of these products particularly warrants more attention since they already exist in the population with no known adverse effects.