title: RITA enhances chemosensivity of pre-B ALL cells to doxorubicin by inducing p53-dependent apoptosis.
abstract: The use of low-molecular-weight, non-peptidic molecules that disrupt the interaction between the p53 tumor suppressor and its negative regulator MDM2 has provided a promising alternative for the treatment of different types of cancer. Here, we used small-molecule reactivation of p53 and induction of tumor cell apoptosis (RITA) to sensitize leukemic NALM-6 cells to doxorubicin by upregulating p53 protein. RITA alone effectively inhibited NALM-6 cells viability in dose-dependent manner as measured by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay and induced apoptosis as evaluated by flow cytometry, whereas RITA in combination with doxorubicin enhanced NALM-6 cells to doxorubicin-sensitivity and promoted doxorubicin induced apoptosis. Levels of p53 protein and its proapoptotic target genes, quantified by western blot and real-time PCR respectively, showed that expression of p53 was significantly increased after RITA treatment. Using p53 inhibitors PFT-alpha and PFT-mu it was shown that p53-mediated apoptosis induced by RITA can be regulated by both p53-transcription-dependent and -independent pathways. Moreover, RITA-induced apoptosis was accompanied by the activation of caspase-3 and PARP cleavage. Therefore, exploiting synergistic effects between RITA and chemotherapeutics might be an effective clinical strategy for leukemia chemotherapy.
authors.affiliation: Department of Hematology, Faculty of Allied Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Kazemi
authors.forename: Majid
authors.initials: M
authors.lastname: Safa
authors.forename: Atefeh
authors.initials: A
authors.lastname: Shahbazi
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004268:DNA-Binding Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000008:administration & dosage / Q000494:pharmacology*; D004357:Drug Synergism; D006801:Humans; D009363:Neoplasm Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C403666:ZNF331 protein, human; D004317:Doxorubicin; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2