Differential effects of 5-aminolaevulinic acid photodynamic therapy and psoralen + ultraviolet A therapy on p53 phosphorylation in normal human skin in vivo.
BACKGROUND
Phosphorylation of the tumour suppressor p53 by the CK2/FACT pathway plays a central role in suppressing ultraviolet (UV)-induced skin cancer in animal models. Although p53 protein stabilization is induced after solar-simulated irradiation of human skin in vivo, p53 phosphorylation has not been defined.


OBJECTIVE
To investigate the effects of clinically effective treatments for skin diseases including psoralen + UVA (PUVA) and photodynamic therapy (PDT) on p53 phosphorylation to determine whether the tumour-suppressing p53 kinase pathways are activated upon use of these therapies.


METHODS
We used antibodies to the ATM/ATR and CK2/FACT phosphorylation sites on p53.


RESULTS
We found that p53 activation was induced selectively by PUVA treatment, while 8-oxo-7,8-dihydroguanine DNA damage was induced selectively by 5-aminolaevulinic acid (ALA)-PDT treatment. Importantly, PUVA treatment resulted in p53 kinase activation, as defined by p53 modification at AT (serine-15) and CK2/FACT (serine-392) sites within the proliferative compartment.


CONCLUSIONS
These data demonstrate that PUVA provokes accumulation and phosphorylation of p53 by AT and CK2/FACT within critical proliferative focal points (as determined by p63 colocalization studies) where DNA damage may lead to tumorigenesis. PDT is mechanistically distinct in that there is a lower level of induction of p53 expression with no evidence of AT- or CK2/FACT-mediated phosphorylation. This suggests that the type of DNA damage created by the reactive oxygen species generated by ALA-PDT does not induce the p53 pathway classically required for the repair of DNA photoadducts induced by UV.
Finlan
L E
LE
University of Edinburgh, Divisin of Oncology, Cancer Research UK Cell Signalling Unit, South Crewe Road, Edinburgh EH4 2XU, UK. lefinlan@yahoo.co.uk
Kernohan
N M
NM
Thomson
G
G
Beattie
P E
PE
Hupp
T R
TR
Ibbotson
S H
SH
D000622:Aminolevulinic Acid / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004249:DNA Damage; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000528:radiation effects; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects; D011701:PUVA Therapy; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D010778:Photochemotherapy; D012867:Skin / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53; D000622:Aminolevulinic Acid