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Gajan A, Sarma A, Kim S, Gurdziel K, Wu GS, Shekhar MP. Analysis of Adaptive Olaparib Resistance Effects on Cisplatin Sensitivity in Triple Negative Breast Cancer Cells. Front Oncol 2021; 11:694793. [PMID: 34367977 PMCID: PMC8339968 DOI: 10.3389/fonc.2021.694793] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 07/05/2021] [Indexed: 12/13/2022] Open
Abstract
Poly-(ADP)-ribose polymerase inhibitors (PARPi) and platinum-based drugs are promising therapies for triple negative breast cancers (TNBC) with BRCA1 or BRCA2 loss. PARPi(s) show better efficacies when combined with platinum-based therapy, however, acquisition of PARPi resistance has been linked with co-resistance to platinum-based drugs. Here, we show that TNBCs with constitutively hyperactivated PARP-1 display greater tolerances for the PARPi olaparib and cisplatin, and respond synergistically to olaparib/cisplatin combinations with increased cytotoxicity. Regardless of BRCA1 and PARP-1 activity status, upon gaining olaparib resistance (OlaR), OlaR MDA-MB-468 (BRCA1 wild-type) and SUM1315 (BRCA1 mutant) TNBC cells retain cisplatin sensitivities of their isogenic parental counterparts. OlaR TNBC cells express decreased levels of PARP-1 and Pol η, a translesion-synthesis polymerase important in platinum-induced interstrand crosslink repair. Although native RAD51 recombinase levels are unaffected, anti-RAD51 immunoreactive low molecular weight sbands are exclusively detected in OlaR cells. Despite normal BRCA1, RAD51 foci formation/recruitment to double-strand breaks are impaired in OlaR MDA-MB-468 cells, suggesting homologous-recombination impairment. RNA-seq and pathway analysis of cisplatin-affected genes revealed enrichment of G2/M cell cycle regulation and DNA repair pathways in parental and OlaR MDA-MB-468 cells whereas parental and OlaR SUM1315 cells showed enrichment of inflammatory stress response pathways associated with TNFR1/2, TWEAK and IL-17 signaling. These data show that TNBC models with wild type versus mutant BRCA1 exhibit differences in CDDP-induced cellular response pathways, however, the CDDP-induced signaling responses remain stable across the isogenic models of OlaR from the same lineage. These data also show that adaptive OlaR does not automatically promote cisplatin resistance, implicating the potential benefit of platinum-based therapy for OlaR TNBCs.
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Affiliation(s)
- Ambikai Gajan
- Karmanos Cancer Institute, Detroit, MI, United States.,Department of Oncology, Wayne State University School of Medicine, Detroit, MI, United States
| | - Ashapurna Sarma
- Karmanos Cancer Institute, Detroit, MI, United States.,Department of Oncology, Wayne State University School of Medicine, Detroit, MI, United States
| | - Seongho Kim
- Karmanos Cancer Institute, Detroit, MI, United States.,Department of Oncology, Wayne State University School of Medicine, Detroit, MI, United States
| | - Katherine Gurdziel
- Genome Sciences Core, Wayne State University, Detroit, MI, United States
| | - Gen Sheng Wu
- Karmanos Cancer Institute, Detroit, MI, United States.,Department of Oncology, Wayne State University School of Medicine, Detroit, MI, United States.,Department of Pathology, Wayne State University School of Medicine, Detroit, MI, United States
| | - Malathy P Shekhar
- Karmanos Cancer Institute, Detroit, MI, United States.,Department of Oncology, Wayne State University School of Medicine, Detroit, MI, United States.,Department of Pathology, Wayne State University School of Medicine, Detroit, MI, United States
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Liu X, Jiang Y, Nowak B, Ichikawa S, Ohtawa M, Matsuda A, Plunkett W. Repair of DNA damage induced by the novel nucleoside analogue CNDAG through homologous recombination. Cancer Chemother Pharmacol 2020; 85:661-672. [PMID: 32072218 DOI: 10.1007/s00280-020-04035-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 01/21/2020] [Indexed: 02/03/2023]
Abstract
PURPOSE We postulate that the deoxyguanosine analogue CNDAG [9-(2-C-cyano-2-deoxy-1-β-D-arabino-pentofuranosyl)guanine] likely causes a single-strand break after incorporation into DNA, similar to the action of its cytosine congener CNDAC, and that subsequent DNA replication across the unrepaired nick would generate a double-strand break. This study aimed at identifying cellular responses and repair mechanisms for CNDAG prodrugs, 2-amino-9-(2-C-cyano-2-deoxy-1-β-D-arabino-pentofuranosyl)-6-methoxy purine (6-OMe) and 9-(2-C-cyano-2-deoxy-1-β-D-arabino-pentofuranosyl)-2,6-diaminopurine (6-NH2). Each compound is a substrate for adenosine deaminase, the action of which generates CNDAG. METHODS Growth inhibition assay, clonogenic survival assay, immunoblotting, and cytogenetic analyses (chromosomal aberrations and sister chromatid exchanges) were used to investigate the impact of CNDAG on cell lines. RESULTS The 6-NH2 derivative was selectively potent in T cell malignant cell lines. Both prodrugs caused increased phosphorylation of ATM and its downstream substrates Chk1, Chk2, SMC1, NBS1, and H2AX, indicating activation of ATM-dependent DNA damage response pathways. In contrast, there was no increase in phosphorylation of DNA-PKcs, which participates in repair of double-strand breaks by non-homologous end-joining. Deficiency in ATM, RAD51D, XRCC3, BRCA2, and XPF, but not DNA-PK or p53, conferred significant clonogenic sensitivity to CNDAG or the prodrugs. Moreover, hamster cells lacking XPF acquired remarkably more chromosomal aberrations after incubation for two cell cycle times with CNDAG 6-NH2, compared to the wild type. Furthermore, CNDAG 6-NH2 induced greater levels of sister chromatid exchanges in wild-type cells exposed for two cycles than those for one cycle, consistent with increased double-strand breaks after a second S phase. CONCLUSION CNDAG-induced double-strand breaks are repaired mainly through homologous recombination.
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Affiliation(s)
- Xiaojun Liu
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, 77054, USA
- School of Health Professions, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Yingjun Jiang
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, 77054, USA
| | - Billie Nowak
- Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Satoshi Ichikawa
- Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Masaki Ohtawa
- Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Akira Matsuda
- Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - William Plunkett
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, 77054, USA.
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Trevino V. Integrative genomic analysis identifies associations of molecular alterations to APOBEC and BRCA1/2 mutational signatures in breast cancer. Mol Genet Genomic Med 2019; 7:e810. [PMID: 31294536 PMCID: PMC6687632 DOI: 10.1002/mgg3.810] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 05/28/2019] [Accepted: 05/31/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The observed mutations in cancer are the result of ~30 mutational processes, which stamp particular mutational signatures (MS). Nevertheless, it is still not clear which genomic alterations correlate to several MS. Here, a method to analyze associations of genomic data with MS is presented and applied to The Cancer Genome Atlas breast cancer data revealing promising associations. METHODS The MS were discretized into clusters whose extremes were statistically associated with mutations, copy number, and gene expression data. RESULTS Known associations for apolipoprotein B editing complex (APOBEC) and for BRCA1 and BRCA2 support the proposal. For BRCA1/2, mutations in ARAP3, three focal deletions, and one amplification were detected. Around 50 mutated genes for the two APOBEC signatures were identified including three kinesins (KIF13A, KIF1B, KIF4A), three ubiquitins (USP45, UBR4, UBR1), and two demethylases (KDM5B, KDM5C) among other genes also connected to DNA damage pathways. The results suggest novel roles for other genes currently not involved in DNA repair. The altered expression program was very high for the BRCA1/2 signature, high for APOBEC signature 13 clearly associated to immune response, and low for APOBEC signature 2. The remaining signatures show scarce associations. CONCLUSION Specific genetic alterations can be associated with particular MS.
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Affiliation(s)
- Victor Trevino
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo Leon, México
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4
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SAHA and cisplatin sensitize gastric cancer cells to doxorubicin by induction of DNA damage, apoptosis and perturbation of AMPK-mTOR signalling. Exp Cell Res 2018; 370:283-291. [PMID: 29959912 DOI: 10.1016/j.yexcr.2018.06.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 06/21/2018] [Accepted: 06/26/2018] [Indexed: 12/23/2022]
Abstract
Chemotherapy remains the most prescribed anti-cancer therapy, despite patients suffering severe side effects and frequently developing chemoresistance. These complications can be partially overcome by combining different chemotherapeutic agents that target multiple biological pathways. However, selecting efficacious drug combinations remains challenging. We previously used fission yeast Schizosaccharomycespombe as a surrogate model to predict drug combinations, and showed that suberoylanilide hydroxamic acid (SAHA) and cisplatin can sensitise gastric adenocarcinoma cells toward the cytotoxic effects of doxorubicin. Yet, how this combination undermines cell viability is unknown. Here, we show that SAHA and doxorubicin markedly enhance the cleavage of two apoptosis markers, caspase 3 and poly-ADP ribose polymerase (PARP-1), and increase the phosphorylation of γH2AX, a marker of DNA damage. Further, we found a prominent reduction in Ser485 phosphorylation of AMP-dependent protein kinase (AMPK), and reductions in its target mTOR and downstream ribosomal protein S6 phosphorylation. We show that SAHA contributes most of the effect, as confirmed using another histone deacetylase inhibitor, trichostatin A. Overall, our results show that the combination of SAHA and doxorubicin can induce apoptosis in gastric adenocarcinoma in a synthetically lethal manner, and that fission yeast offers an efficient tool for identifying potent drug combinations against human cancer cells.
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5
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Rodriguez E, Chevalier J, El Ghoul H, Voldum-Clausen K, Mundy J, Petersen M. DNA damage as a consequence of NLR activation. PLoS Genet 2018; 14:e1007235. [PMID: 29462140 PMCID: PMC5834200 DOI: 10.1371/journal.pgen.1007235] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 03/02/2018] [Accepted: 01/31/2018] [Indexed: 01/20/2023] Open
Abstract
DNA damage observed during plant immune responses is reported to be an intrinsic component of plant immunity. However, other immune responses may suppress DNA damage to maintain host genome integrity. Here, we show that immunity-related DNA damage can be abrogated by preventing cell death triggered by Nucleotide-binding, Leucine-rich-repeat immune Receptors (NLRs). SNI1 (suppressor of npr1-1, inducible 1), a subunit of the structural maintenance of chromosome (SMC) 5/6 complex, was reported to be a negative regulator of systemic acquired resistance (SAR) and to be necessary for controlling DNA damage. We find that cell death and DNA damage in sni1 loss-of-function mutants are prevented by mutations in the NLR signaling component EDS1. Similar to sni1, elevated DNA damage is seen in other autoimmune mutants with cell death lesions, including camta3, pub13 and vad1, but not in dnd1, an autoimmune mutant with no visible cell death. We find that as in sni1, DNA damage in camta3 is EDS1-dependent, but that it is also NLR-dependent. Using the NLR RPM1 as a model, we also show that extensive DNA damage is observed when an NLR is directly triggered by effectors. We also find that the expression of DNA damage repair (DDR) genes in mutants with cell death lesions is down regulated, suggesting that degraded DNA that accumulates during cell death is a result of cellular dismantling and is not sensed as damaged DNA that calls for repair. Our observations also indicate that SNI1 is not directly involved in SAR or DNA damage accumulation.
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Affiliation(s)
- Eleazar Rodriguez
- Department of Biology, University of Copenhagen. Copenhagen, Denmark
| | | | - Hassan El Ghoul
- Department of Biology, University of Copenhagen. Copenhagen, Denmark
| | | | - John Mundy
- Department of Biology, University of Copenhagen. Copenhagen, Denmark
| | - Morten Petersen
- Department of Biology, University of Copenhagen. Copenhagen, Denmark
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6
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Shuhendler AJ, Ye D, Brewer KD, Bazalova-Carter M, Lee KH, Kempen P, Dane Wittrup K, Graves EE, Rutt B, Rao J. Molecular Magnetic Resonance Imaging of Tumor Response to Therapy. Sci Rep 2015; 5:14759. [PMID: 26440059 PMCID: PMC4594000 DOI: 10.1038/srep14759] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 09/02/2015] [Indexed: 11/09/2022] Open
Abstract
Personalized cancer medicine requires measurement of therapeutic efficacy as early as possible, which is optimally achieved by three-dimensional imaging given the heterogeneity of cancer. Magnetic resonance imaging (MRI) can obtain images of both anatomy and cellular responses, if acquired with a molecular imaging contrast agent. The poor sensitivity of MRI has limited the development of activatable molecular MR contrast agents. To overcome this limitation of molecular MRI, a novel implementation of our caspase-3-sensitive nanoaggregation MRI (C-SNAM) contrast agent is reported. C-SNAM is triggered to self-assemble into nanoparticles in apoptotic tumor cells, and effectively amplifies molecular level changes through nanoaggregation, enhancing tissue retention and spin-lattice relaxivity. At one-tenth the current clinical dose of contrast agent, and following a single imaging session, C-SNAM MRI accurately measured the response of tumors to either metronomic chemotherapy or radiation therapy, where the degree of signal enhancement is prognostic of long-term therapeutic efficacy. Importantly, C-SNAM is inert to immune activation, permitting radiation therapy monitoring.
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Affiliation(s)
- Adam J Shuhendler
- Molecular Imaging Program at Stanford, Stanford, California 94305, USA.,Departments of Radiology, Stanford, California 94305, USA
| | - Deju Ye
- Molecular Imaging Program at Stanford, Stanford, California 94305, USA.,Departments of Radiology, Stanford, California 94305, USA
| | - Kimberly D Brewer
- Molecular Imaging Program at Stanford, Stanford, California 94305, USA.,Departments of Radiology, Stanford, California 94305, USA
| | - Magdalena Bazalova-Carter
- Molecular Imaging Program at Stanford, Stanford, California 94305, USA.,Radiation Oncology, Stanford, California 94305, USA
| | - Kyung-Hyun Lee
- Molecular Imaging Program at Stanford, Stanford, California 94305, USA.,Departments of Radiology, Stanford, California 94305, USA
| | - Paul Kempen
- Materials Science and Engineering, Stanford University, Stanford, California 94305, USA
| | - K Dane Wittrup
- Department of Chemical Engineering, Department of Biological Engineering, and Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
| | - Edward E Graves
- Molecular Imaging Program at Stanford, Stanford, California 94305, USA.,Radiation Oncology, Stanford, California 94305, USA
| | - Brian Rutt
- Molecular Imaging Program at Stanford, Stanford, California 94305, USA.,Departments of Radiology, Stanford, California 94305, USA
| | - Jianghong Rao
- Molecular Imaging Program at Stanford, Stanford, California 94305, USA.,Departments of Radiology, Stanford, California 94305, USA
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Guha G, Lu W, Li S, Liang X, Kulesz-Martin MF, Mahmud T, Indra AK, Ganguli-Indra G. Novel Pactamycin Analogs Induce p53 Dependent Cell-Cycle Arrest at S-Phase in Human Head and Neck Squamous Cell Carcinoma (HNSCC) Cells. PLoS One 2015; 10:e0125322. [PMID: 25938491 PMCID: PMC4418703 DOI: 10.1371/journal.pone.0125322] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 03/16/2015] [Indexed: 01/01/2023] Open
Abstract
Pactamycin, although putatively touted as a potent antitumor agent, has never been used as an anticancer drug due to its high cytotoxicity. In this study, we characterized the effects of two novel biosynthetically engineered analogs of pactamycin, de-6MSA-7-demethyl-7-deoxypactamycin (TM-025) and 7-demethyl-7-deoxypactamycin (TM-026), in head and neck squamous cell carcinoma (HNSCC) cell lines SCC25 and SCC104. Both TM-025 and TM-026 exert growth inhibitory effects on HNSCC cells by inhibiting cell proliferation. Interestingly, unlike their parent compound pactamycin, the analogs do not inhibit synthesis of nascent protein in a cell-based assay. Furthermore, they do not induce apoptosis or autophagy in a dose- or a time-dependent manner, but induce mild senescence in the tested cell lines. Cell cycle analysis demonstrated that both analogs significantly induce cell cycle arrest of the HNSCC cells at S-phase resulting in reduced accumulation of G2/M-phase cells. The pactamycin analogs induce expression of cell cycle regulatory proteins including master regulator p53, its downstream target p21Cip1/WAF1, p27kip21, p19, cyclin E, total and phospho Cdc2 (Tyr15) and Cdc25C. Besides, the analogs mildly reduce cyclin D1 expression without affecting expression of cyclin B, Cdk2 and Cdk4. Specific inhibition of p53 by pifithrin-α reduces the percentage of cells accumulated in S-phase, suggesting contribution of p53 to S-phase increase. Altogether, our results demonstrate that Pactamycin analogs TM-025 and TM-026 induce senescence and inhibit proliferation of HNSCC cells via accumulation in S-phase through possible contribution of p53. The two PCT analogs can be widely used as research tools for cell cycle inhibition studies in proliferating cancer cells with specific mechanisms of action.
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Affiliation(s)
- Gunjan Guha
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
| | - Wanli Lu
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
- Molecular and Cell Biology Program, Oregon State University, Corvallis, Oregon, United States of America
| | - Shan Li
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
| | - Xiaobo Liang
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
| | - Molly F. Kulesz-Martin
- Department of Dermatology, Oregon Health and Science University, Portland, Oregon, United States of America
| | - Taifo Mahmud
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
- Molecular and Cell Biology Program, Oregon State University, Corvallis, Oregon, United States of America
| | - Arup Kumar Indra
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
- Molecular and Cell Biology Program, Oregon State University, Corvallis, Oregon, United States of America
- Department of Dermatology, Oregon Health and Science University, Portland, Oregon, United States of America
- Environmental Health Science Center, Oregon State University, Corvallis, Oregon, United States of America
- * E-mail: (GGI); (AKI)
| | - Gitali Ganguli-Indra
- Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon, United States of America
- Molecular and Cell Biology Program, Oregon State University, Corvallis, Oregon, United States of America
- * E-mail: (GGI); (AKI)
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Bougen NM, Steiner M, Pertziger M, Banerjee A, Brunet-Dunand SE, Zhu T, Lobie PE, Perry JK. Autocrine human GH promotes radioresistance in mammary and endometrial carcinoma cells. Endocr Relat Cancer 2012; 19:625-44. [PMID: 22807498 DOI: 10.1530/erc-12-0042] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Although recent advances in breast cancer treatment regimes have improved patient prognosis, resistance to breast cancer therapies, such as radiotherapy, is still a major clinical challenge. In the current study, we have investigated the role of autocrine human GH (hGH) in resistance to ionising radiation (IR)-based therapy. Cell viability and total cell number assays demonstrated that autocrine hGH promoted cell regrowth in the mammary carcinoma cell lines, MDA-MB-435S and T47D, and the endometrial carcinoma cell line, RL95-2, following treatment with IR. In addition, autocrine hGH enhanced MDA-MB-435S and T47D cell clonogenic survival following radiation exposure. The enhanced clonogenic survival afforded by autocrine hGH was mediated by JAK2 and Src kinases. Investigation into the DNA repair capacity demonstrated that autocrine hGH reduced IR-induced DNA damage in MDA-MB-435S and T47D cells. Functional antagonism of hGH increased RL95-2 sensitivity to IR in cell viability and total cell number assays, reduced clonogenic survival and enhanced the induction of DNA damage. Thus, autocrine hGH reduced sensitivity to treatment with IR in mammary and endometrial carcinoma cell lines in vitro, while functional antagonism of hGH sensitised endometrial carcinoma cells to IR. Functional antagonism of hGH, used in conjunction with radiotherapy, may therefore enhance treatment efficacy and improve the prognosis of patients with breast and endometrial cancer.
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Affiliation(s)
- Nicola M Bougen
- The Liggins Institute, University of Auckland, Auckland, New Zealand
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Shinozaki K, Hosokawa Y, Hazawa M, Kashiwakura I, Okumura K, Kaku T, Nakayama E. Ascorbic acid enhances radiation-induced apoptosis in an HL60 human leukemia cell line. JOURNAL OF RADIATION RESEARCH 2011; 52:229-237. [PMID: 21343676 DOI: 10.1269/jrr.10089] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This study was conducted to examine the utility of the combined use of ascorbic acid (AsA) and radiation in clinical applications. We investigated cell survival, DNA fragmentation, and caspase activation after X-ray irradiation and AsA treatment of human leukemia HL60 cells. The number of living cells decreased after combined X-ray irradiation and AsA treatment (2 Gy + 5 mM) in comparison with that after X-ray irradiation (2 Gy) or AsA treatment (5 mM) alone. DNA fragmentation was more in the cells subjected to combined X-ray irradiation and AsA treatment than in those subjected to X-ray irradiation alone. Caspase-3, caspase-8, and caspase-9 were highly activated following combined X-ray irradiation and AsA treatment, but caspase-8 activity was not markedly increased after X-ray irradiation alone. Bax levels in the mitochondrial membrane fractions were increased after AsA treatment alone and after combined X-ray irradiation and AsA treatment. However, there was no apparent increase in the Bax levels after X-ray irradiation treatment alone. Thus, this study confirmed that supplementing X-ray irradiation with AsA treatment results in increased apoptosis in HL60 cells. With regard to the apoptosis-inducing factors, we hypothesized that Bax and caspase-8 were activated after combined X-ray irradiation and AsA treatment compared with either treatment alone.
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Affiliation(s)
- Koji Shinozaki
- Division of Oral and Maxillofacial Radiology, Department of Human Biology and Pathophysiology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
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Brown ET, Holt JT. Rad51 overexpression rescues radiation resistance in BRCA2-defective cancer cells. Mol Carcinog 2009; 48:105-9. [PMID: 18618591 DOI: 10.1002/mc.20463] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Breast cancers with BRCA2 mutations exhibit DNA repair defects and are particularly sensitive to radiation. BRCA2 interacts with Rad51 in a complex manner involving internal BRC and C-terminal TR2 domains which play a key role in homologous recombination. BRCA2 expression also modulates Rad51 protein levels such that Rad51 protein is relatively decreased in BRCA2-defective cancer cells. This is mediated in part through BRCA2's capacity to protect Rad51 from caspase-3 proteolytic degradation. In order to distinguish between functional and expression related roles for BRCA2 we studied the results of Rad51 overexpression in mouse and human cells with inactivating BRCA2 mutations. The results show that overexpression of wild-type Rad51 partially rescues BRCA2 deficiency but that overexpression of a caspase-3 resistant Rad51 completely complements the BRCA2 defect in radiation responsiveness. These results indicate that Rad51 can compensate for some aspects of a BRCA2 gene defect and suggest that Rad51 expression levels may be an important modifier of the BRCA2 defective genotype.
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Affiliation(s)
- Erika T Brown
- Department of Pathology, University of Colorado Health Sciences Center, RC-1 South Tower, 12801 East 17th Avenue, Aurora, Colorado 80010-7163, USA
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