Characterization of coordinated immediate responses by p16INK4A and p53 pathways in UVB-irradiated human skin cells.
While the precise mechanisms of melanoma development are unknown, recent in vivo studies have revealed that the p16(Ink4a)/Rb pathway is disrupted in melanomagenesis. Here, we characterize the role of p16/Rb in coordinating the early events in UVB-irradiated skin. Foreskins and melanoma cell cultures were irradiated with low and high acute UVB doses and examined for cell-cycle- and apoptosis-associated genes. In melanoma cells, low UVB dose upregulated p16, p53, and p21 expression levels in Malme-3M, and high UVB dose accentuated the expression of p53 and p21(Cip1/Waf1), in particular; however, in SkMel-28 cells only p16 expression was upregulated in response to UV irradiation. In HaCaT cells, high UVB dose caused dramatic increase in p53 expression followed by upregulation of p21(Cip1/Waf1) and Bax, and downregulation of Bcl-2 leading to apoptosis. In HaCaT cells, reinstatement of p16 pathway restored cell-cycle arrest in response to low dose. Foreskin organ culture experiments confirmed our in vitro cell results. These data indicate that the p53 and p16 pathways respond independently to UVB insult. The p16 pathway is favored at low doses and results in cell-cycle arrest; the p53 pathway is more responsive to higher doses and induces apoptosis depending on p53 mutation status.
Abd Elmageed
Zakaria Y
ZY
Department of Pathology, Stanley S Scott Cancer Center, Louisiana State University Health Science Center, New Orleans, Louisiana 70112, USA.
Gaur
Rajiv L
RL
Williams
Mandy
M
Abdraboh
Mohamed E
ME
Rao
Prakash N
PN
Raj
Madhwa H G
MH
Ismail
Fathi M
FM
Ouhtit
Allal
A
D017209:Apoptosis; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002470:Cell Survival; D002478:Cells, Cultured; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000378:metabolism*; D008954:Models, Biological; D012867:Skin / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014466:Ultraviolet Rays
D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53