ABSTRACT
BACKGROUND: The function of the p53 protein is known to regulate cell proliferation by inhibiting cells entering S phase, so DNA damaged cell proliferation is inhibited by apoptosis. p21 is a cyclin dependent kinase inhibitor induced by wild type p53, not mutant p53. Thus p21 is thought to mediate the signal of p53 induced by DNA damaged agents to arrest the cell cycle in G1 phase. p53 and p21 are expressed in many malignant tumors, and its role in oncogenesis, tumor progression and prognosis are important. OBJECTIVE: The purpose of this study was to analyze immunohistochemical expression of mutant p53 and p21 protein in melanocytic lesions. METHOD: 11 cases of intradermal nevus, 7 cases of junctional nevus and 6 cases of malignant melanoma were immunohistochemically stained with p53 and p21 monoclonal antibodies. RESULTS: 1. In intradermal nevus, the p53 was negative in 100% and the p21 was negative in 98%. These findings suggest that the composing cells of intradermal nevus is completely mature cell. 2. The positive rates of p53 and p21 in junctional nevus were 43% and 43%, respectively. The positive rates of p53 and p21 in malignant melanoma were 82% and 67%, respectively. CONCLUSION: If the expression of p21 is induced by p53 independent pathway, the cell cycle can be arrested in G1 phase, so the tumor cell proliferation is inhibited. But if the expressed p21 is mutated as p53, it means that the natural function of p21 disappears. More research is necessary about the nature of p21 which is expressed with mutant p53.