Restoration of wild-type conformation and activity of a temperature-sensitive mutant of p53 (p53(V272M)) by the cytoprotective aminothiol WR1065 in the esophageal cancer cell line TE-1.
ABSTRACT The aminothiol WR1065, the active metabolite of the cytoprotector amifostine, exerts its antimutagenic effects through free-radical scavenging and other unknown mechanisms. In an earlier report, we showed that WR1065 activates wild-type p53 in MCF-7 cells, leading to p53-dependent arrest in the G(1) phase of the cell cycle. To determine whether WR1065 activates p53 by modulating protein conformation, we analyzed its effects on p53 conformation and activity in the esophageal cancer cell line TE-1. This cell line contains a mutation in codon 272 of p53 (p53(V272M), with methionine instead of a valine), conferring temperature-sensitive properties to the p53 protein. At the nonpermissive temperature (37 degrees C), p53(V272M) adopts the mutant p53 conformation (nonreactive with the antibody PAb1620), does not bind specifically to DNA, and is not activated in response to DNA-damaging treatment. However, treatment with 0.5-4 mM WR1065 partially restored wild-type conformation at 37 degrees C, stimulated DNA binding activity, and increased the expression of p53 target genes WAF-1, GADD45, and MDM2, leading to cell-cycle arrest in G(1). These results suggest that WR1065 activates p53 through a mechanism distinct from DNA-damage signaling, which involves modulation of p53 protein conformation.
- SourceAvailable from: aacrjournals.org[show abstract] [hide abstract]
ABSTRACT: Through an in vivo and in vitro analysis of the absorption kinetics of S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721) in the normal tissues and solid tumors of mice, rats, and rabbits, it has been demonstrated that normal tissues actively concentrate WR-2721 against a concentration gradient, whereas solid tumors passively absorb it, or, if active concentration of WR-2721 is present in tumors, it operates at a far reduced rate relative to normal tissues. These observations can account for the ability of WR-2721 to selectively protect normal tissues against both radiation and alkylating agent injury.Cancer Research 06/1980; 40(5):1519-24. · 8.65 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Many p53 mutants found in human cancer have an altered ability to bind DNA and transactivate gene expression. Re-expression of functional p53 in cells in which the endogenous TP53 gene is inactivated has been demonstrated to restore a non-tumorigenic phenotype. Pharmacological modulation of p53 mutant conformation may therefore represent a mechanism to reactivate p53 function and consequently improve response to radio- and chemotherapy. We have recently reported that the radio- and chemoprotector Amifostine (WR2721, Ethyol) activates wild-type p53 in cultured mammalian cells. In the present study, we have used a yeast functional assay to investigate the effect of WR2721 on the transcriptional activity of p53. WR2721 restored this activity in a temperature-sensitive mutant V272M (valine to methionine at codon 272) expressed at the non-permissive temperature and it also partially restored the transcriptional activity of several other conformationally flexible p53 mutants. The results indicate that the yeast functional assay may be used to identify compounds that modulate p53 activity, with potential therapeutic implications.Oncogene 07/2001; 20(27):3533-40. · 7.36 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: More than 70 cell lines were established from esophageal cancer, including 15 TE-series cell lines established by the authors. This article reviews molecular and cellular features of esophageal cancer cells from studies using these cell lines as well as primary tumors. The subjects reviewed include primary cultures of normal epithelium of the esophagus and of esophageal tumors, their growth and differentiation properties, chromosomal aberrations, protein kinase C, growth factors and their receptors, oncogenes, and tumor-suppressor genes. Lesions of genetic loci in esophageal cancer include the absence of mutations in ras genes in primary tumors, amplification and overexpression of the c-erbB gene, co-amplification of hst-1 and int-2 genes, mutations, and allelic loss of tumor suppressor genes, p53, Rb, APC, and MCC. Future clinical improvement will be achieved on the basis of the understanding of molecular and cellular features of esophageal cancer cells.Journal of Cancer Research and Clinical Oncology 02/1993; 119(8):441-9. · 2.91 Impact Factor