title: PJ34, a poly(ADP-ribose) polymerase (PARP) inhibitor, reverses melphalan-resistance and inhibits repair of DNA double-strand breaks by targeting the FA/BRCA pathway in multidrug resistant multiple myeloma cell line RPMI8226/R.
abstract: There is still no ideal treatment for multidrug resistant multiple myeloma, looking for drugs which can reverse chemotherapy resistance and enhance curative effects of chemotherapy drugs becomes a problem that needs to be solved urgently. Poly(ADP-ribose) polymerase inhibitors appear to be an important tool for medical therapy of several malignancies. In the present study, we investigated the potential of the PARP-1 inhibitor PJ34, in vitro, to further enhance the efﬁcacy of the traditional chemotherapy drug melphalan in the multidrug-resistant multiple myeloma cell line RPMI8226/R. The effects of different concentrations of PJ34 and melphalan on cell proliferation were determined by the CCK-8 assay. The expressions of FA/BRCA pathway-related factors were detected by western blotting and RT-PCR. The percentage of cell apoptosis was measured with flow cytometry. DNA double-strand break (DSB) repair was quantiﬁed by γH2AX immunoﬂuorescence. In addition, DNA damage repair at the level of the individual cell was determined by comet assay. Co-administration of PJ34 and melphalan had synergistic inhibitory effects on the proliferation of RPMI8226/R cells, suggesting more powerful antitumor activities. The apoptosis percentage also was increased more obviously by the treatment of melphalan plus PJ34. The activation of FA/BRCA pathway was inhibited by downregulation of related factors including FANCD2, BRCA2 and Rad51. PJ34 significantly increased the ratio of γH2AX-positive cells and the number of foci/cells. The comet tail rate of cells, tail length, tail moment and Olive tail moment all increased after PJ34 treatment in RPMI8226/R cells. These results indicate that PJ34 combined treatment with melphalan produces synergistic effects and reverses multidrug resistance of RPMI8226/R cells effectively. PJ34 cannot induce DNA damage directly, but it may increase the DNA damage induced by melphalan through inhibiting DNA damage repair. The suppression of FA/BRCA pathway may be the mechanism. Therefore, we suggest that PARP inhibitors may deserve future investigations as tools for medical treatment of multidrug resistant multiple myeloma.
authors.affiliation: Department of Hematology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei 430071, P.R. China.
authors.forename: Ting
authors.initials: T
authors.lastname: Xiong
authors.affiliation: Department of Hematology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei 430071, P.R. China.
authors.forename: Heng
authors.initials: H
authors.lastname: Wei
authors.affiliation: Department of Hematology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei 430071, P.R. China.
authors.forename: Xiaoqiong
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Hematology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei 430071, P.R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Xiao
mesh_terms: D019313:BRCA1 Protein / Q000378:metabolism; D024682:BRCA2 Protein / Q000378:metabolism; D045744:Cell Line, Tumor; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D004260:DNA Repair / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004357:Drug Synergism; D052217:Fanconi Anemia Complementation Group A Protein / Q000378:metabolism; D006801:Humans; D008558:Melphalan / Q000627:therapeutic use*; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010616:Phenanthrenes / Q000494:pharmacology*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D019313:BRCA1 Protein; D024682:BRCA2 Protein; C498471:FANCA protein, human; D052217:Fanconi Anemia Complementation Group A Protein; C434926:N-(oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide hydrochloride; D010616:Phenanthrenes; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D008558:Melphalan