methods are provided for ascertaining and measuring rptp - κ activity in response to insults such as uv irradiation and with respect to administration of a treatment and / or composition . attenuation of egfr activity by rptp - κ affects aspects of photoaging , including damage to the skin , suppression of the immune system , dna damage , and connective tissue degradation . intervention with respect to the effects of photoaging can include protection of rptp - κ from oxidation . the methods can be used for discovery of anti - aging treatments , adjuncts , or other preventative treatments , such as sunscreens .