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Friday 15 August 2008

RAPID ROUNDUP: Moisturisers increase skin cancer risk in UV-radiation treated mice – Experts respond

New research to be published in the Journal of Investigative Dermatology, implicates several common moisturising creams in increasing the development of skin cancer in mice that have been exposed to UV-radiation.

Although mouse skin is quite different from human skin, the researchers used a hairless mouse model for sunlight-induced non-melanoma skin cancer in humans .
They exposed the mice to UV radiation to mimic exposure to the sun and then, after stopping UV treatment, they applied four different brands of moisturisers to the animals.  Mice treated with each of the four brands had an increased rate of tumor formation. The team honed in on several ingredients that they believed might enhance tumour formation in the skin.  A new moisturiser prepared without these ingredients did not have the same effect of increasing the rate of skin cancer in the UV-exposed mice. Though the research may initially appear alarming, the authors indicate that the significance of these findings has not been established in humans.

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A/Prof Graham Mann is an Associate Professor in Medicine at the University of Sydney. He is an expert in the genetic and environmental causes of skin cancer.

"This is a highly artificial system where hairless mice were exposed to enough UV radiation to give at least 80% of them some form of skin cancer or pre-cancer within four months. Treating the mice with moisturisers that contain known irritants like sodium lauryl sulphate or mineral oil may have increased the rate or number of these tumours, though the proportion of mice with tumours was about the same.

Importantly, a moisturiser (their Custom Blend) that didn't contain SLS or mineral oil had no tumour enhancing effect. So the study does not cast a cloud over moisturisers in general.

It is very hard to relate this study to humans and sun-induced skin cancer. It raises the possibility that some components of some moisturising creams might have a negative effect when the skin has already been strongly primed to develop tumours by UV exposure."

Mr Gavin Greenoak is the Managing and Scientific Director of the Australian Photobiology Testing Facility (APTF) at the University of Sydney.

“This quote came to mind in reading this paper – ‘when science is not a celebration of detail, then expect the devil elsewhere.’ The authors state that “the significance of these findings has not been established in humans.” This does not mean I think that we need to be careful about applying moisturisers to our pet hairless mice after their romp in the sun. They also say that “the research could help to explain the incidence of some types of skin cancer in patients.”

The potential for alarmism is high, and therefore this paper invites the highest level of scrutiny, which it does not, in my view, sufficiently bear to warrant publication. 

In this study using a hairless mouse (deficient in DNA Excision Repair, important for skin cancer, and proficient in humans), there is no description of the condition of the skin following UVB irradiation to which product was applied; the UVB lamps emitted extraterrestrial wavelengths lower than those reaching the earth and highly pathogenic; the use of UVB+* alone is highly artefactual with respect to its effects in comparison with the sunlight spectrum as a whole (< 0.2%);  there is no time-line for when irradiation was ceased and product application began; there is no control with product alone without UVB+ irradiation; there is no attempt, in view of the effects, at comparative analysis of the products used or declaration of the basis for their “Custom” product; the amount of product applied is equivalent to approximately four times the amount of sunscreen commonly used to prevent sunburn; the seventeen week period of treatment and observation was insufficient to properly determine the “promoting” effect with respect to skin cancers “initiated” by UVB+ and their latency; and these hairless mice carry a sub-clinical skin inflammatory response to degenerated hair follicles.

The acknowledged need for more research is an understatement bordering on irresponsibility.”

* Photobiologists usually refer to UVB as that which is terrestrially contingent (290 – 320 nm).  Physicists often refer to UVB as wavelengths from 280 – 315 nm.  I have used the term UVB+ because it is defined in this paper unconventionally (280 – 320 nm).

Professor Rod Sinclair is Director of the Department of Dermatology at St Vincent's Hospital in Melbourne

“Skin cancer is the most common cancer in Australia.  Skin cancer rates are expected to increase by around 50% by 2020 due to a combination of population ageing and the popularity of outdoor activities.

Life time sun exposure is the main risk factor for skin cancer.  The impact of the sun is greatest on those amongst us with fair skin, fair hair and blue eyes.  However ever as Claire Oliver demonstrated, no one is immune. 

This study suggests that daily use of moisturisers is an additional risk factor for skin cancer development in mice, however I doubt this is significant in humans.  Moisturiser use is much greater among women, however skin cancers, and in particular the type of skin cancers studies in this research seem to be more common among men.”

Associate Professor Michael Kimlin is Program Leader in the Australian Sun and Health Research Laboratory and a Senior Research Fellow at Queensland University of Technology.

"This paper provides an interesting and controversial hypothesis for the formation of skin cancers. We need to heed and acknowledge this work and progress quickly into understanding if these results are applicable to humans through the conducting of trials in humans to see if the results can be replicated."

Professor Ian Olver, is CEO of The Cancer Council Australia

“In the experiments, the researchers irradiated mice with ultraviolet light, which makes them prone to developing skin cancers.  They wanted to study whether the application of caffeine would inhibit the development of skin cancer, but because they were going to apply the caffeine in a moisturizing cream, they decided to test the moisturising cream on its own first.  In these mice that were exposed to ultraviolet radiation, subsequent application of four commercially available creams increased the rate of skin cancers. The application of a custom-blended cream made by the researchers did not increase the rate of tumours.  Previous research had shown that when Vaseline cream was applied prior to radiation, it inhibited the rate of tumours forming.  However, lanolin-based creams enhanced that rate. 

“The relevance of this study to humans is that the model replicates what happens when a person is heavily exposed to sunlight when they are young, and later develops skin cancers.  However, whether the findings in hairless mice are relevant to the human situation is unknown.  These results would indicate the need for further studies.”