title: Doxorubicin and octreotide induce a 40 kDa breakdown product of p53 in human hepatoma and tumoral colon cell lines.
abstract: The chemotherapeutic drug doxorubicin and the anti-proliferative long-acting somatostatin analogue octreotide, both used in cancer treatment, have been shown to increase the expression of the p53 tumour suppressor protein. In the present study, we demonstrate by Western-blot analysis that, in addition to the p53 protein, these molecules were able to induce the expression of a shorter protein with an apparent molecular mass of 40 kDa (p40), recognized by antibodies raised against the N-terminus of p53. This induction was present in tumoral and non-tumoral cells and did not depend on the status of the endogenous p53 protein. The p40 protein was significantly induced after 3 h of cell treatment with doxorubicin or octreotide, remained stable until 24 h and was located in the nuclear extract. Using reverse primers corresponding to each exon of the p53 gene, only one transcript was amplified by reverse transcriptase-PCR. This suggested that p40 was issued from a post-translational modification and not from an alternative splicing. This protein was not recognized by the PAb421 antibody, suggesting that it was issued from a cleavage of the p53 C-terminal region (p40deltaC). Furthermore, this cleavage was not dependent on caspase activity. In conclusion, these results support the hypothesis that this post-translational modification plays a significant role in the regulation of multiple p53 signalling pathways. These results also suggest that octreotide, a molecule with different signalling pathways, was able as doxorubicin to generate a p53 breakdown product.
authors.affiliation: Inserm U327, Faculté de Médecine Xavier Bichat, IFR 02, 16 rue Henri Huchard, BP 416, 75870, Paris Cedex 18, France.
authors.forename: Zahia
authors.initials: Z
authors.lastname: Sadji-Ouatas
authors.forename: Malika
authors.initials: M
authors.lastname: Lasfer
authors.forename: Sophie
authors.initials: S
authors.lastname: Julien
authors.forename: Gérard
authors.initials: G
authors.lastname: Feldmann
authors.forename: Florence
authors.initials: F
authors.lastname: Reyl-Desmars
mesh_terms: D006528:Carcinoma, Hepatocellular; D003110:Colonic Neoplasms; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology*; D016158:Genes, p53 / Q000187:drug effects*; D006801:Humans; D008113:Liver Neoplasms; D008970:Molecular Weight; D015282:Octreotide / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000378:metabolism*
chemical_list: D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin; D015282:Octreotide