title: RITA (Reactivating p53 and Inducing Tumor Apoptosis) is efficient against TP53abnormal myeloma cells independently of the p53 pathway.
abstract: BACKGROUND
  The aim of this study was to evaluate the efficacy of the p53-reactivating drugs RITA and nutlin3a in killing myeloma cells.
  
  
  METHODS
  A large cohort of myeloma cell lines (n = 32) and primary cells (n = 21) was used for this study. This cohort contained cell lines with various TP53 statuses and primary cells with various incidences of deletion of chromosome 17. Apoptosis was evaluated using flow cytometry with Apo2.7 staining of the cell lines or via the loss of the myeloma-specific marker CD138 in primary cells. Apoptosis was further confirmed by the appearance of a subG1 peak and the activation of caspases 3 and 9. Activation of the p53 pathway was monitored using immunoblotting via the expression of the p53 target genes p21, Noxa, Bax and DR5. The involvement of p53 was further studied in 4 different p53-silenced cell lines.
  
  
  RESULTS
  Both drugs induced the apoptosis of myeloma cells. The apoptosis that was induced by RITA was not related to the TP53 status of the cell lines or the del17p status of the primary samples (p = 0.52 and p = 0.80, respectively), and RITA did not commonly increase the expression level of p53 or p53 targets (Noxa, p21, Bax or DR5) in sensitive cells. Moreover, silencing of p53 in two TP53(mutated) cell lines failed to inhibit apoptosis that was induced by RITA, which confirmed that RITA-induced apoptosis in myeloma cells was p53 independent. In contrast, apoptosis induced by nutlin3a was directly linked to the TP53 status of the cell lines and primary samples (p < 0.001 and p = 0.034, respectively) and nutlin3a increased the level of p53 and p53 targets in a p53-dependent manner. Finally, we showed that a nutlin3a-induced DR5 increase (≥ 1.2-fold increase) was a specific and sensitive marker (p < 0.001) for a weak incidence of 17p deletion within the samples (≤ 19%).
  
  
  CONCLUSIONS
  These data show that RITA, in contrast to nutlin3a, effectively induced apoptosis in a subset of MM cells independently of p53. The findings and could be of interest for patients with a 17p deletion, who are resistant to current therapies.
authors.forename: Sylvanie
authors.initials: S
authors.lastname: Surget
authors.forename: Géraldine
authors.initials: G
authors.lastname: Descamps
authors.forename: Carole
authors.initials: C
authors.lastname: Brosseau
authors.forename: Vincent
authors.initials: V
authors.lastname: Normant
authors.forename: Sophie
authors.initials: S
authors.lastname: Maïga
authors.forename: Patricia
authors.initials: P
authors.lastname: Gomez-Bougie
authors.forename: Nadège
authors.initials: N
authors.lastname: Gouy-Colin
authors.forename: Catherine
authors.initials: C
authors.lastname: Godon
authors.forename: Marie C
authors.initials: MC
authors.lastname: Béné
authors.forename: Philippe
authors.initials: P
authors.lastname: Moreau
authors.forename: Steven
authors.initials: S
authors.lastname: Le Gouill
authors.forename: Martine
authors.initials: M
authors.lastname: Amiot
authors.affiliation: CRCNA, INSERM, UMR 892, Nantes F-44000, France. catherine.pellat-deceunynck@inserm.fr.
authors.forename: Catherine
authors.initials: C
authors.lastname: Pellat-Deceunynck
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020868:Gene Silencing; D006801:Humans; D020128:Inhibitory Concentration 50; D008928:Mitochondria / Q000378:metabolism; D009101:Multiple Myeloma / Q000235:genetics* / Q000378:metabolism*; D021381:Protein Transport; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D015533:Transcriptional Activation / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein