Oncogenes and tumor suppressor genes in photocarcinogenesis

Orthogonal Array composite design to study and optimize antioxidant combinations in the prevention of UVB-induced HSF damage

Excessive exposure to ultraviolet (UV) B radiation may lead to skin damage, photosensitivity, or even tumorigenesis via induction of oxidative stress. Naturally derived antioxidants could play significant roles in cancer therapy due to their multi-targeted actions and lack of substantial toxicity. Drug combinations target at diverse pathway of cells and make cells export meticulous biological outcomes through the multifaceted signaling network. The UVB protective effects of combinations of naturally derived antioxidants- curcumin, resveratrol, proanthocyanidins, baicalein, and beta-nicotinamide adenine dinucleotide (NADH) were investigated. An oxidative cell damage model was established to study the ultraviolet irradiation system. An orthogonal array composite design (OACD) was employed in the optimization of antioxidants combinations. Combination of resveratrol (0.1μM) and baicalein in medium concentration (0.2μM), with NADH in high concentration (0.8μM) was found to be the most efficacious combination among all the 30 runs performed using OACD. The findings suggested that UVB exposure-inflicted cell apoptosis can be significantly reduced by naturally-derived antioxidant combinations. These results provide an insight into the discovery of synergistic antioxidant combinations in skin cancer, using orthogonal array composite design (OACD). The results also have practical implications in the understanding of drug mechanisms in skin cancer, which can assist clinical practice by recommending better drug combinations.

Indoor Tanning, Skin Cancer and the Young Female Patient: A Review of the Literature

Young, non-Hispanic white females represent the population most likely to use indoor tanning facilities. This population may be at increased risk of skin cancer as recent meta-analyses support a strong association between cutaneous malignancy and indoor tanning. Public perception of the purported health benefits of indoor tanning may be partially to blame for the popularity of tanning salons as a desire to prepare skin prior to sun exposure is among the most commonly cited motivations for indoor tanning. Improving education and counseling to address misconceptions regarding tanning safety will require the participation of healthcare providers for both physical and psychological screenings as well as for information dissemination. This review presents the association between tanning bed use and skin cancer, biological effects of UV radiation exposure, UV burden associated with tanning devices, public perception of tanning, demographic and psychological profile of indoor tanners, and current legislation regulating tanning bed use.

Effect of phlorotannins isolated from Ecklonia cava on melanogenesis and their protective effect against photo-oxidative stress induced by UV-B radiation

In the present study, three kinds of phlorotannins, marine algal polyphenol, were isolated from a brown alga Ecklonia cava, and their inhibitory effect on melanogenesis as well as the protective effect against photo-oxidative stress induced by UV-B radiation was investigated. The effect on melanogenesis was evaluated via the inhibitory effects of tyrosinase and melanin synthesis. Among the phlorotannins, dieckol showed higher effect than that of the other phlorotannins in the both assays; especially the value of dieckol in the tyrosinase inhibition assay was relatively higher than that of a commercial tyrosinase inhibitor (kojic acid). The UV-B protection effect was evaluated via DCFH-DA, MTT, comet assays, and morphological changes in fibroblast. Intracellular ROS induced by UV-B radiation was reduced by the addition of phlorotannins and cell viability was dose-dependently increased. Moreover, dieckol demonstrated strong protective properties against UV-B radiation-induced DNA damage via damaged tail intensity and morphological changes in fibroblast. Hence, these results indicated that dieckol isolated from E. cava has potential whitening effects and prominent protective effects on UV-B radiation-induced cell damages, which might be used in pharmaceutical and cosmeceutical industries.

Photochemoprevention of UVB-induced skin carcinogenesis in SKH-1 mice by brown algae polyphenols

Chronic exposure of the skin to ultraviolet B (UVB) radiation induces oxidative stress, which plays a crucial role in the induction of skin cancer. In this study, the effect of dietary feeding and topical application of brown algae polyphenols on UVB radiation-induced skin carcinogenesis in SKH-1 mice was investigated. SKH-1 hairless mice were randomly divided into 9 groups, including control, UVB control and treatment groups. They were treated orally (0.1% and 0.5% with AIN-76 diet, w/w) and topically (3 and 6 mg/0.2 ml of vehicle) with brown algae polyphenols and irradiated with UVB for 26 weeks. Dietary feeding (0.1% and 0.5%) of brown algae polyphenols significantly reduced tumor multiplicity (45% and 56%) and tumor volume (54% and 65%), and topical administration (3 and 6 mg) significantly decreased tumor multiplicity (60% and 46%) and tumor volume (66% and 57%), respectively, per tumor-bearing mouse. Dietary feeding and topical administration of the polyphenols also inhibited tumor incidence by 6% and 21%, respectively, but the results were not significant. Dietary and topical administration of the polyphenols markedly inhibited cyclooxygenase-2 activity and cell proliferation. These observations show that brown algae polyphenols have an antiphotocarcinogenic effect which may be associated with the prevention of UVB-induced oxidative stress, inflammation, and cell proliferation in the skin.

Mice defective in the mismatch repair gene Msh2 show increased predisposition to UVB radiation-induced skin cancer

Mice defective in the mismatch repair (MMR) gene Msh2 manifest an enhanced predisposition to skin cancer associated with exposure to UVB radiation. This predisposition is further heightened if the mice are additionally defective for the nucleotide excision repair gene Xpc. To test the hypothesis that the predisposition of Msh2 mutant mice to skin cancer reflects a mutator phenotype associated with increased proliferation of skin cells following exposure to UV radiation, Msh2 mutant mice were exposed to the tumor promoter TPA. Such mice showed a robust proliferative response in the skin, but did not manifest evidence of dysplasia or neoplasia. We conclude that the predisposition of Msh2 mice to UVB radiation-induced skin cancer reflects an interaction between the processes of mismatch repair and some other excision repair mode, the exact nature of which remains to be established.

A novel immediate early response gene, IEX-1, is induced by ultraviolet radiation in human keratinocytes

Skin cancer is the most common human malignancy and is strongly associated with exposure to ultraviolet radiation (UVR). Several mechanisms including an increase in immediate early gene activation have been postulated to be involved in UVR-mediated carcinogenesis. We show that in a dose-dependent manner, UVR induces the expression of messenger RNA of a novel immediate early response gene, IEX-1, in human keratinocytes. Human keratinocytes and mouse fibroblasts transfected with an expression plasmid for IEX-1 grow at a faster rate than keratinocytes transfected with a similar plasmid that does not contain the IEX-1 sequence. IEX-1 protein is localized predominantly in the nucleus of keratinocytes by fluorescent antibody methods and by examination of the location of a green fluorescence IEX-1 fusion protein. Epidermal growth factor (EGF), a major mitogen of keratinocytes, and a tumor-promoting phorbol ester increase IEX-1 mRNA expression. IEX-1 may play a role in keratinocyte proliferation especially following UVR.