Sunlight and skin cancer: Another link revealed
- Laboratory of Molecular Carcinogenesis, National Cancer Institute, Building 37, Room 3E24, Bethesda, MD 20892
Here comes the sun, Here comes the sun, and I say, “It’s alright.” —George Harrison
Skin cancer is the most common neoplasm in Caucasians in the United States with a lifetime risk nearly equal to that of all other cancers combined (1). More than 800,000 people are expected to develop nonmelanoma skin cancer [basal cell carcinoma (BCC) or squamous cell carcinoma (SCC)] this year in the United States (2). Sun exposure is the major environmental agent implicated in induction of nonmelanoma skin cancer (3). While sun exposure begins early in life, the average patient with nonmelanoma skin cancer is about 60 years old (1) (Fig. 1). The article by Jonason et al. (4) in a previous issue of the Proceedings provides a new insight into the link between sun exposure and nonmelanoma skin cancer and furnishes information about events occurring between the time of initial sun exposure and subsequent skin cancer years later.
Age of onset of skin cancers in normal and xeroderma pigmentosum (XP) skin cancer patients. The cumulative percentage of patients with BCCs or SCCs of the skin is plotted versus the age at diagnosis. The curve for the normal population is based on 29,757 skin cancers surveyed by the National Cancer Institute (1). The curve for the xeroderma pigmentosum patients is based on 63 skin cancers reported to the Xeroderma Pigmentosum Registry (unpublished data).
The multistage theory of carcinogenesis is based on experimental studies in rodents and has been proposed as a general model for environmental carcinogenesis (5) (Fig. 2). In the first stage—initiation—a carcinogen mutates a target gene. Initiation is followed by promotion, a process in visibly normal skin in which the single damaged cell expands to form a clone of damaged cells. These changes progress, leading to precancerous clinically abnormal skin and then to cancer. …
