Enhanced expression of Ki-67, topoisomerase IIalpha, PCNA, p53 and p21WAF1/Cip1 reflecting proliferation and repair activity in UV-irradiated melanocytic nevi.
To investigate the effect of ultraviolet (UV) irradiation on the expression of cell cycle-associated proteins, melanocytic nevi from healthy volunteers were partially covered, irradiated with a defined UV dose, and excised 1 week thereafter. The irradiated and the protected parts were examined separately by conventional microscopy and immunohistochemistry using the antibodies Ki-S11 (Ki-67), Ki-S7 (topoisomerase IIalpha), PC10 (proliferating cell nuclear antigen [PCNA]), DO-7 (p53), 6B6 (p21WAF1/Cip1), and the melanocytic marker HMB-45. DNA nick-end labeling was used as a marker of apoptosis. Irradiation resulted in morphological changes and increased HMB-45 reactivity. Proliferation, as assessed by Ki-67 and topoisomerase IIalpha expression, was also clearly enhanced in the UV-exposed areas. This was confirmed by the appearance of occasional mitotic figures. PCNA expression levels markedly exceeded those of the proliferation markers and did not correlate with the latter in most cases. p21 immunolabeling indices were also consistently augmented after UV exposure; hence it is likely that growth-inhibitory mechanisms partly compensate for the proliferative impulse, and the disproportional rise in PCNA expression probably reflects DNA repair activity. Enhanced p53 immunostaining in four cases suggests that the induction of p21 after irradiation may be p53 mediated, whereas no concomitant apoptotic events were observed. We conclude that UV light can stimulate the proliferative activity of melanocytes in melanocytic nevi, but that simultaneously cell cycle inhibitors are activated to permit DNA repair.
Rudolph
P
P
Department of Pathology and the Lymph Node Registry, German Society of Pathology, at the University of Kiel.
Tronnier
M
M
Menzel
R
R
Möller
M
M
Parwaresch
R
R
D000328:Adult; D000951:Antigens, Neoplasm; D017209:Apoptosis / Q000528:radiation effects; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002455:Cell Division / Q000528:radiation effects; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004260:DNA Repair; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004273:DNA, Neoplasm / Q000378:metabolism*; D004268:DNA-Binding Proteins; D006801:Humans; D020287:In Situ Nick-End Labeling; D007527:Isoenzymes / Q000378:metabolism; D015603:Keratinocytes / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D019394:Ki-67 Antigen / Q000378:metabolism; D008544:Melanocytes / Q000528:radiation effects*; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D009508:Nevus, Pigmented / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D019394:Ki-67 Antigen; D018809:Proliferating Cell Nuclear Antigen; D016159:Tumor Suppressor Protein p53; D004250:DNA Topoisomerases, Type II