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A novel hypoxia-selective epigenetic agent RRx-001 triggers apoptosis and overcomes drug resistance in multiple myeloma cells.

ABSTRACT: The hypoxic bone marrow (BM) microenvironment confers growth/survival and drug resistance in multiple myeloma (MM) cells. Novel therapies targeting the MM cell in its hypoxic BM milieu may overcome drug resistance. Recent studies led to the development of a novel molecule RRx-001 with hypoxia-selective epigenetic and nitric oxide-donating properties. Here, we demonstrate that RRx-001 decreases the viability of MM cell lines and primary patient cells, as well as overcomes drug resistance. RRx-001 inhibits MM cell growth in the presence of BM stromal cells. RRx-001-induced apoptosis is associated with: (i) activation of caspases; (ii) release of ROS and nitrogen species; (iii) induction of DNA damage via ATM/?-H2AX; and (iv) decrease in DNA methyltransferase (DNMT) and global methylation. RNA interference study shows a predominant role of DNMT1 in MM cell survival versus DNMT3a or DNMT3b. The deubiquitylating enzyme USP7 stimulates DNMT1 activity, and conversely, USP7-siRNA reduced DNMT1 activity and decreased MM cell viability. RRx-001 plus USP7 inhibitor P5091 triggered synergistic anti-MM activity. MM xenograft studies show that RRx-001 is well tolerated, inhibits tumor growth and enhances survival. Combining RRx-001 with pomalidomide, bortezomib or SAHA induces synergistic anti-MM activity. Our results provide the rationale for translation of RRx-001, either alone or in combination, to clinical evaluation in MM.

SUBMITTER: Das DS

PROVIDER: S-EPMC5093055 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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A novel hypoxia-selective epigenetic agent RRx-001 triggers apoptosis and overcomes drug resistance in multiple myeloma cells.

Das D Sharma DS Ray A A Das A A Song Y Y Tian Z Z Oronsky B B Richardson P P Scicinski J J Chauhan D D Anderson K C KC

Leukemia 20160427 11

The hypoxic bone marrow (BM) microenvironment confers growth/survival and drug resistance in multiple myeloma (MM) cells. Novel therapies targeting the MM cell in its hypoxic BM milieu may overcome drug resistance. Recent studies led to the development of a novel molecule RRx-001 with hypoxia-selective epigenetic and nitric oxide-donating properties. Here, we demonstrate that RRx-001 decreases the viability of MM cell lines and primary patient cells, as well as overcomes drug resistance. RRx-001 ...[more]

PMID: 27118403

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Project description:BackgroundRRx-001, a dinitroazetidine derivative, is a novel anticancer agent currently in phase II clinical trials. It mediates immunomodulatory effects either directly through polarization of tumor associated macrophages or indirectly through vascular normalization and increased T-lymphocyte infiltration. With multiple additional mechanisms of action including upregulation of oxidative stress, depletion of GSH and NADPH, anti-angiogenesis and epigenetic modulation, RRx-001 is being studied as a radio- and chemo-sensitizer to resensitize tumors to prior therapy and to prime tumors to respond to radiation, chemotherapy and immunotherapy in combination therapy studies. Here, we identified another mechanism, viral mimicry, which refers to the "unsilencing" of epigenetically repressed viral genes present in the tumor that provokes an immune response and may contribute to the anticancer activity of RRx-001.ResultsRRx-001 inhibited the growth of colon cancer cells (HCT 116) and decreased levels of the DNA methyltransferases DNMT1 and DNMT3a in a time and dose-dependent manner. Treatment of HCT 116 cells with 0.5 μM RRx-001 for 24 h significantly increased transcripts of interferon (IFN)-responsive genes and this induction was sustained for up to 4 weeks after transient exposure to RRx-001. ELISA assays showed that RRx-001 increased secretion of type I and III IFNs by HCT 116 cells, and these IFNs were confirmed to be bioactive. Transcription of endogenous retrovirus ERV-Fc2 and LTRs from the ERV-L family (MLT2B4 and MLT1C49) was induced by RRx-001. The induction of ERV-Fc2-env was through demethylation of ERV-Fc2 LTR as determined by methylation-specific polymerase chain reaction and combined bisulfite restriction analysis. Immunofluorescence staining with J2 antibody confirmed induction of double-stranded RNA.ConclusionsTransient exposure of HCT 116 cells to low-dose RRx-001 induced transcription of silenced retroviral genes present in the cancer cell DNA with subsequent synthesis of IFN in response to this "pseudo-pathogenic" stimulus, mimicking an antiviral defense. RRx-001-mediated IFN induction may have the potential to improve the efficacy of immunotherapies as well as radiotherapy, standard chemotherapies and molecularly targeted agents when used in combination. The striking safety profile of RRx-001 in comparison to other more toxic epigenetic and immunomodulatory agents such as azacitidine makes it a leading candidate for such clinical applications.

Project description:RRx-001 (also known as ABDNAZ, 1-bromoacetyl-3,3-dinitroazetidine) is a novel aerospace-derived compound currently under investigation in several ongoing Phase II studies. In a Phase I trial, it demonstrated anti-cancer activity and evidence of resensitization to formerly effective therapies in heavily pre-treated patients with relapsed/refractory solid tumors. With a pharmacologically unprecedented dinitroazetidine scaffold, RRx-001 generates reactive oxygen and nitrogen species (ROS and RNS) and nitric oxide (NO), elicits changes in intracellular redox status, modulates tumor blood flow, hypoxia and vascular function and triggers apoptosis in cancer cells. Here, the effect of RRx-001 on the epigenome of SCC VII cancer cells was investigated. RRx-001 at 0.5 and 2 μM significantly decreased global DNA methylation, i.e., 5-methylcytosine levels, in SCC VII cells determined by analysis with an enzyme-linked immunosorbent assay (ELISA). Consistently, 0.5-5 μM RRx-001 significantly decreased Dnmt1 and Dnmt3a protein expression determined using Western blot in a dose- and time-dependent manner. In addition, global methylation profiling identified differentially methylated genes in SCC VII cells treated with 0.5, 2, and 5 μM RRx-001 compared to control cells. Twenty-three target sites were hypomethylated and 22 hypermethylated by >10% in the presence of at least two different concentrations of RRx-001. Moreover, RRx-001 at 2 μM significantly increased global acetylated histone H3 and H4 levels in SCC VII cells after 24 hour treatment determined by a fluorometric assay, suggesting that RRx-001 regulates global acetylation in cancer cells. These results demonstrate that, in contrast to the traditional “one drug one target” paradigm, RRx-001 has multi(epi)target features, which contribute to its anti-cancer activity and may rationalize the resensitization to previously effective therapies observed in clinical trials and serve as a unifying mechanism for its anticancer activity.

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A novel hypoxia-selective epigenetic agent RRx-001 triggers apoptosis and overcomes drug resistance in multiple myeloma cells.

Publications

A novel hypoxia-selective epigenetic agent RRx-001 triggers apoptosis and overcomes drug resistance in multiple myeloma cells.

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