Inhibition of phorbol ester--induced human epidermal ornithine decarboxylase activity by oral compounds: a possible role in human chemoprevention studies

Final Report on the Safety Assessment of Arachidonic Acid

Arachidonic Acid is an essential, polyunsaturated, fatty acid that is used as a surfactant-cleansing agent and a surfactant-emulsifying agent in cosmetic formulations. Arachidonic Acid is well absorbed from the gastrointestinal tract and the circulatory system; it distributes rapidly into the lipid compartment of the body and is rapidly converted to phospholipid by the liver.

Arachidonic Acid may alter the cutaneous immune response; in one study, the effect was more pronounced at lower test concentrations than at higher. Application of Arachidonic Acid to mouse skin produced edema and inflammation, with high dosages possibly causing ulceration of the skin. Arachidonic Acid has mutagenic potential. In a 24 h single insult patch test, a formulation containing 0.04% Arachidonic Acid was not a skin irritant.

The safety of use of this ingredient in cosmetic products has not been documented and substantiated. It cannot be concluded that Arachidonic Acid is safe for use in cosmetic products until the needed additional safety test data have been obtained and evaluated. If the requested skin absorption data indicate that absorption occurs, immunomodulatory data, carcinogenicity and photocarcinogenicity data, human irritation, sensitization, and photosensitization data may also be required.

Systemic strategies for chemoprevention of skin cancers in transplant recipients

BACKGROUND

Solid organ transplant recipients (OTRs) are a growing population at high risk for cutaneous neoplasms, resulting in significant post-transplant morbidity and mortality. Management of malignant and pre-malignant cutaneous lesions in transplant recipients is challenging, making prevention of such neoplasms paramount. The objectives of the present study are to review and analyze systemic strategies for chemoprevention of malignant and pre-malignant cutaneous neoplasms in OTRs.

METHODS

MEDLINE and PubMed searches were performed to identify studies with original data quantifying the effects of systemic agents on the development of malignant cutaneous neoplasms in patients with solid organ transplants.

RESULTS

We identified nine studies describing 111 transplant recipients that quantified the effects of oral retinoids on cutaneous neoplasms. A majority of the studies found a decrease in the number of malignant and pre-malignant cutaneous lesions in patients treated with systemic retinoids, with several studies noting increased benefit in those patients with multiple previous skin cancers. Multiple studies described a rebound effect, with increased numbers of neoplasms occurring following discontinuation of retinoids. Side effects often limited dosing, but required discontinuation of retinoids in a minority of patients. No studies were identified that adequately quantified the effects of other systemic agents on skin cancer incidence in this population.

CONCLUSIONS

Although systemic retinoids are frequently used for chemoprevention of cutaneous malignancies in OTRs, the data supporting their use are composed largely of small uncontrolled case reports and case series. However, the available data suggest that retinoids have chemopreventative effects in this population. Although optimal dosing and indications for initiation of systemic retinoid therapy are not conclusive from the data, it suggests that retinoids are most effective in patients with multiple previous non-melanoma skin cancers. Side effects and beneficial effects were noted across a wide range of doses, suggesting that retinoids should be initiated at a low dose and increased as tolerated to a minimally effective dose. Further investigation through randomized controlled trials is needed to further clarify the tolerability and efficacy of multiple dosing regimens on the incidence of pre-malignant and malignant lesions in transplant recipients. The therapeutic role of other systemic agents in the transplant population has not been established.

Hypothesis: spermine may be an important epidermal antioxidant

Spermine has been identified as a potent antioxidant and an anti-inflammatory agent. The compound is present in all organisms and all organs. The concentration is exceptionally high in skin, and I propose that spermine constitutes a prime defence against radiation damage. This hypothesis is substantiated by the fact that ornithine decarboxylase (ODC), the rate-controlling enzyme of spermine biosynthesis, is induced by UVB-irradiation and oxidative stress. On the contrary, inhibition of ODC makes cells more sensitive to radiation damage. The antioxidative effect of spermine may be due to metal chelation and/or to prevention of superoxide generation from stimulated neutrophils. This paper reviews the antioxidative and anti-inflammatory effects of spermine, and suggests that spermine is an important antioxidant of epidermis.

Biology of cutaneous squamous cell carcinoma

Nonmelanoma skin cancer is the leading cause of cancer in the United States. Cutaneous squamous cell carcinoma is second only to basal cell carcinoma in prevalence and its incidence is increasing. The biology of squamous cell carcinoma is reviewed under the broad areas of etiology, immunobiology, biochemistry, metastatic potential, and therapy, with emphasis on prevention, diagnosis, and management.