Repair of U-V induced DNA damage is of key importance to UV-induced skin ca
rcinogenesis. Specific signal transduction pathways that regulate cell cycl
ing, differentiation and apoptosis are found to be corrupted in skin cancer
s, e.g., the epidermal growth-stimulating Hedgehog pathway in basal cell ca
rcinomas (BCCs). Mutations in genes coding for proteins in these pathways l
ead to persistent disturbances that are passed along to daughter cells, e.g
., mutations in the gene for the Patched (PTCH) protein in the Hedgehog pat
hway. Thus far only the point mutations in the P53 gene from squamous cell
carcinomas and BCCs, and in PTCH gene from BCC of xeroderma pigmentosum (XP
) patients appear to be unambiguously attributable to solar UV radiation. S
olar UVB radiation is most effective in causing these point mutations. Othe
r forms of UV-induced genetic changes (e.g., deletions) may, however, contr
ibute to skin carcinogenesis with different wavelength dependencies. (C) 20
01 Elsevier Science B.V. All rights reserved.