Basal cell carcinoma (BCC) is the most common skin cancer in the Western wo
rld. Ultraviolet (UV) exposure, race, age, gender, and decreased DNA repair
capacity are known risk factors for the development of BCC, Of these, UVB
irradiation from sunlight is the most significant risk factor. The incidenc
e of sporadic BCC increases in individuals older than age 55, with the grea
test incidence reported in individuals who are older than 70, and is rare i
n individuals who are younger than 30., In this study, we analyzed 24 BCC s
amples from individuals who had BCC diagnosed by the age of 30. Fifteen sin
gle-stranded conformation polymorphism variants in the PTCH gene were ident
ified in 13 BCC samples. Sequence analysis of these single-stranded conform
ation polymorphism variants revealed 13 single nucleotide changes, one AT i
nsertion, and one 15-bp deletion. Most of these nucleotide changes (nine of
15) were predicted to result in truncated PTCH proteins. Fifteen p53 mutat
ions were also found in 11 of the 24 BCC samples. Thirty-three percent (fiv
e of 15) and 60% (nine of 15) of the nucleotide changes in the PTCH and p53
genes, respectively, were UV-specific C-->T and CC-->TT nucleotide changes
. Our data demonstrate that the p53 and PTCH genes are both implicated in t
he development of early-onset BCC. The identification of UV-specific nucleo
tide changes in both tumor suppressor genes suggests that UV exposure is an
important risk factor in early onset of BCC.