Ascorbate up-regulates MLH1 (Mut L homologue-1) and p73: implications for the cellular response to DNA damage.
We have found previously that ascorbic acid (vitamin C), as well as acting as a radical scavenger, may modulate the expression of several genes [i.e. fra-1, glutathione S-transferase Pi (GSTpi) and Mut L homologue-1 (MLH1)] in human keratinocytes. In the present paper, we demonstrate that MLH1, as well as its downstream target p73, can be positively modulated by this antioxidant vitamin, indeed, up-regulation of the two mRNAs was observed after just 2 h, and increased further up to 16 h of treatment. Modulation of MLH1 and p73 gene expression improves cellular susceptibility to apoptosis triggered by the DNA-damaging agent cisplatin. Indeed, in ascorbate-supplemented cells, increased cisplatin-induced apoptosis was seen, involving activation of the MLH1/c-Abl/p73 signalling cascade. Our results were further confirmed by studies performed on genetically defined mutants, i.e. mouse embryo fibroblasts derived from knock-out animals for c-Abl or p53, as well as human colon carcinoma cell lines deficient in MLH1. The increased sensitivity to cisplatin observed in ascorbate-loaded cells appeared to be dependent exclusively on MLH1 and c-Abl expression, and independent of p53. These data suggest a potential mechanism accounting for the anti-carcinogenic and anti-cancer activities of vitamin C.
Catani
M Valeria
MV
Biochemistry Laboratory, IDI-IRCCS, c/o Department of Experimental Medicine & Biochemical Sciences, University of Rome Tor Vergata, Via Tor Vergata 135, 00133 Rome, Italy.
Costanzo
Antonio
A
Savini
Isabella
I
Levrero
Massimo
M
de Laurenzi
Vincenzo
V
Wang
Jean Y J
JY
Melino
Gerry
G
Avigliano
Luciana
L
D000251:Adenosine Triphosphatases; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002945:Cisplatin / Q000494:pharmacology; D004249:DNA Damage; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D016147:Genes, Tumor Suppressor; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D000070956:MutL Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation / Q000187:drug effects*
D001426:Bacterial Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D009687:Nuclear Proteins; C000606460:TP73 protein, human; C000606368:Trp73 protein, mouse; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D001205:Ascorbic Acid; D002945:Cisplatin