Related Experiment Videos
Sunscreen lotions prevent ultraviolet radiation-induced suppression of antitumor immune responses
1Department of Research and Development, Schering-Plough HealthCare Products, Memphis, TN 38151, USA. LEE.ROBERTS@SPCORP.COM
Abstract:
Exposure to subcarcinogenic doses of ultraviolet (UV) radiation suppresses tumor immunity, thus permitting the emergence and growth of highly immunogenic skin cancers in mice. Sunscreens prevent UV carcinogenesis; however, there are conflicting reports regarding their ability to block UV-induced tumor immune suppression. In this study we critically evaluated the effects of UV spectrum and dose on the tumor immune protective capacity of 4 marketed sunscreen lotions with labeled sun protection factors (SPF) 8-45. Effective tumor immune suppression doses (TISD), i.e., the lowest dose tested to induce outgrowth of transplanted nonmelanoma skin tumors in 100% of UV-exposed C3H mice, were established for 3 different UV sources. TISD were significantly lower for unfiltered (FS) and Kodacel-filtered (KFS) UVB-type FS20 sunlamps compared with a filtered xenon arc lamp solar simulator. Sunscreen tumor immune protection levels matched those predicted by their labeled SPF when sunscreen-protected mice were exposed to a fixed TISD of solar simulator UV radiation. SPF 30 and 45 sunscreens also blocked activation of tumor antigen-specific suppressor T-lymphocytes in mice exposed to solar simulator UV radiation. In comparison, sunscreens with SPF > or = 15 provided partial to complete protection, as measured by tumor incidence, for mice exposed to UV radiation from KFS. All sunscreens tested reduced tumor growth rates in KFS UV-exposed mice. None of the sunscreens tested provided measurable tumor immune protection for mice exposed to FS UV radiation. Thus, sunscreen lotions provide an extent of tumor immune protection consistent with their labeled SPF when appropriate testing conditions are employed.
Insights
Sunscreen effectiveness in blocking UV radiation-induced immune suppression varies by UV source and dose. Sunscreens protect against tumor growth when tested under specific conditions, aligning with their labeled Sun Protection Factor (SPF).
Area of Science:
- Immunology
- Photobiology
- Dermatology
Background:
- Ultraviolet (UV) radiation exposure can suppress the immune system, promoting skin cancer development.
- Sunscreens are known to prevent UV carcinogenesis, but their efficacy in blocking UV-induced immune suppression is debated.
- Understanding the impact of UV spectrum and dose on sunscreen's immune protective capacity is crucial.
Purpose of the Study:
- To evaluate how different UV spectra and doses affect the immune protective capacity of sunscreens.
- To determine the relationship between labeled Sun Protection Factor (SPF) and actual tumor immune protection.
- To assess the ability of sunscreens to block UV-induced activation of tumor antigen-specific suppressor T-lymphocytes.
Main Methods:
- Four marketed sunscreen lotions with SPF 8-45 were tested.
- Effective tumor immune suppression doses (TISD) were established for three different UV sources (unfiltered FS, Kodacel-filtered KFS, and solar simulator).
- Tumor incidence, tumor growth rates, and T-lymphocyte activation were measured in UV-exposed mice with and without sunscreen application.
Main Results:
- TISD varied significantly depending on the UV source, being lower for UVB-type sunlamps compared to a solar simulator.
- Sunscreen's tumor immune protection correlated with its labeled SPF when tested under solar simulator conditions.
- SPF 30 and 45 sunscreens blocked suppressor T-lymphocyte activation under solar simulator UV exposure.
- Protection levels varied with UV source; sunscreens offered partial to complete protection against KFS UV but no measurable protection against FS UV.
- All tested sunscreens reduced tumor growth rates in KFS UV-exposed mice.
Conclusions:
- Sunscreen lotions offer tumor immune protection that is consistent with their labeled SPF, but only under specific testing conditions and UV spectra.
- The UV spectrum and dose are critical factors determining sunscreen efficacy in preventing UV-induced immune suppression and subsequent tumor development.
- Further research is needed to optimize sunscreen formulations and testing protocols to ensure comprehensive protection against UV-induced immune suppression.