Overexpression of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) in human cutaneous malignant melanoma.
p21(WAF1/CIP1) (p21) is an inhibitor of cyclin-dependent kinases recently identified as the downstream effector of wild-type p53-mediated cell cycle arrest. The gene coding for p21 may function as a negative regulator of melanoma growth, progression, and metastasis. Using immunohistochemistry and Western blotting, we investigated the expression of p21 in human melanocytic proliferations. Immunohistochemical staining was performed on 13 common acquired nevi, 12 dysplastic nevi, 23 primary malignant melanomas, and 12 metastatic melanomas. Common acquired nevi showed minimal p21 staining (1.8+/-0.3%, mean+/-SEM). The percentage of positive nuclei was slightly elevated in dysplastic nevi (8.9+/-1.7%). Both primary malignant melanoma (29+/-3%) and metastatic melanoma (33+/-5%) demonstrated a significantly increased number of p21-positive nuclei compared to benign lesions (p<0.001). p21 was strongly expressed even in actively proliferating lesions as confirmed by MIB-1 labelling, and although the majority of p21-positive cells likely represent a non-proliferating population, staining was occasionally observed in cells undergoing mitosis, suggesting abnormal function of this cell cycle inhibitor in malignant melanoma. Overexpression of p21 in metastatic melanoma compared to common acquired nevi was confirmed by Western blot analysis of human tumor samples. These findings suggest that increased p21 expression relative to benign nevi is not sufficient to control melanoma growth in vivo.
Trotter
M J
MJ
Department of Pathology, Vancouver Hospital and Health Sciences Centre, University of British Columbia, Canada.
Tang
L
L
Tron
V A
VA
D015153:Blotting, Western; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D009362:Neoplasm Metastasis; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D018844:Cyclin-Dependent Kinases