Involvement of p16 and PTCH in pathogenesis of melanoma and basal cell carcinoma

The involvement of two tumor suppressors p16 and Ptch in pathogenesis of cutaneous melanomas and basal cell carcinomas (BCCs) was studied through expression of Ptch and p16 and genetic alterations in 9p21 region (p16) and in 9q22.3 region (PTCH) of chromosome 9. Immunohistochemical analyses of paraffin-embedded tissues with Ptch and p16 antibodies, typing for 9q22-q31 and 9p21 region with polymorphic markers and p16 and Ptch mutation detection was done. Higher expression of p16 and Ptch in melanoma and BCC of the skin was frequently detected in studied cases. However, allelic loss of PTCH region occurs more frequently in BCCs than loss of heterozygosity of p16 region. Both types of tumors, BCCs and melanomas, suggest involvement of Hh-Gli signaling pathway, but using different mechanisms.