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Lou L, Zhang W, Li J, Wang Y. Abnormal MGMT Promoter Methylation in Gastrointestinal Stromal Tumors: Genetic Susceptibility and Association with Clinical Outcome. Cancer Manag Res 2020; 12:9941-9952. [PMID: 33116851 PMCID: PMC7568426 DOI: 10.2147/cmar.s269388] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 09/25/2020] [Indexed: 01/22/2023] Open
Abstract
Purpose KIT/PDGFRA wild-type (WT) gastrointestinal stromal tumors (GISTs) represent a heterogeneous subgroup of GISTs that lack KIT or PDGFRA mutations and possess distinct genetic alterations and primary resistance to imatinib. Succinate dehydrogenase (SDH)-deficient GISTs comprise the largest subpopulation of WT GISTs that are characterized by loss-of-function of SDH. O6-methylguanine-DNA methyltransferase (MGMT) is a specific DNA repair enzyme that has been identified as a predictor of positive treatment response to alkylating agents in a variety of cancers. The aim of this study was to evaluate the expression of MGMT and the prevalence of MGMT promoter methylation in GISTs and to determine the association between MGMT promoter methylation and clinicopathological characteristics and clinical outcomes. Patients and Methods A heterogeneous cohort of 137 primary GISTs that confirmed by immunohistochemistry and KIT/PDGFRA mutation analysis were retrospectively selected and analyzed for MGMT expression and MGMT promoter methylation using immunohistochemical staining and methylation-specific PCR (MSP). A concordance analysis between MGMT promoter methylation and clinicopathological characteristics and prognosis was also performed. Results A total of 44.5% (65/137) of GIST patients displayed loss of MGMT protein expression, and 10.9% (15/137) of these patients exhibited MGMT promoter methylation. However, no significant correlation was observed between the loss of MGMT protein expression and MGMT promoter methylation. WT GISTs possessing an epithelioid or mixed phenotype, particularly those that were SDH-deficient, displayed a markedly higher prevalence of MGMT promoter methylation compared to that in KIT/PDGFRA mutated GISTs. Moreover, MGMT promoter methylation was identified as a potential independent prognostic factor for OS and DFS in patients with GIST. Conclusion MGMT promoter methylation is particularly frequent in SDH-deficient GISTs and in WT GISTs possessing an epithelioid/mixed phenotype, and knowledge of this methylation status may offer a novel potential therapeutic option for WT GISTs.
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Affiliation(s)
- Liping Lou
- Institute of Pathology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Wendi Zhang
- Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Jun Li
- Institute of Pathology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Yu Wang
- Institute of Pathology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
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Ravegnini G, Ricci R. Succinate Dehydrogenase-Deficient Gastrointestinal Stromal Tumors: Small Steps Toward Personalized Medicine? Epigenet Insights 2019; 12:2516865719842534. [PMID: 31020269 PMCID: PMC6463228 DOI: 10.1177/2516865719842534] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Accepted: 03/08/2019] [Indexed: 12/12/2022] Open
Abstract
Various molecular triggers define heterogeneous subsets of gastrointestinal stromal tumors (GISTs), differing in clinical behavior and drug sensitivity. KIT/PDGFRA-wild-type GISTs, including those succinate dehydrogenase (SDH)-deficient, are overall unresponsive to the tyrosine kinase inhibitors commonly used, fostering the development of specific alternative therapeutic strategies. Epigenetic inactivation of O6-methylguanine-DNA methyltransferase (MGMT) through promoter methylation leads to effectiveness of alkylating agents in several human cancers. SDH-deficient GISTs typically feature widespread DNA methylation. However, the actual occurrence of MGMT methylation in these tumors, potentially predisposing them to respond to alkylating drugs, has not been investigated so far. Here we discuss the recent findings concerning the occurrence of MGMT methylation in different GIST subgroups, including SDH-deficient ones, as a premise for a possible reappraisal of alkylating agents specifically targeting these small, otherwise overall chemorefractory, GIST subgroups.
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Affiliation(s)
- Gloria Ravegnini
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Riccardo Ricci
- Department of Pathology, Università Cattolica del Sacro Cuore, Rome, Italy.,UOC di Anatomia Patologica, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Rome, Italy
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3
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Ricci R, Martini M, Ravegnini G, Cenci T, Milione M, Lanza P, Pierconti F, Santini D, Angelini S, Biondi A, Rosa F, Alfieri S, Clemente G, Persiani R, Cassano A, Pantaleo MA, Larocca LM. Preferential MGMT methylation could predispose a subset of KIT/PDGFRA-WT GISTs, including SDH-deficient ones, to respond to alkylating agents. Clin Epigenetics 2019; 11:2. [PMID: 30616628 PMCID: PMC6322231 DOI: 10.1186/s13148-018-0594-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 12/03/2018] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumors (GISTs) constitute a small KIT/PDGFRA-WT GIST subgroup featuring DNA methylation which, although pervasive, appears nevertheless not randomly distributed. Although often indolent, these tumors are mostly chemorefractory in aggressive cases. Promoter methylation-induced O6-methylguanine DNA methyltransferase (MGMT) inactivation improves the efficacy of alkylating agents in gliomas, colorectal cancer and diffuse large B cell lymphoma. MGMT methylation has been found in some GISTs, without determining SDH status. Thirty-six GISTs were enrolled in past sarcoma trials testing alkylating agents, with negative results. Nevertheless, a possible effect on MGMT-methylated GISTs could have escaped detection, since tested GISTs were neither selected by genotype nor investigated for SDH; MGMT was studied in two cases only, revealing baseline activity; these trials were performed prior to the adoption of Choi criteria, the most sensitive for detecting GIST responses to therapy. Under these circumstances, we investigated whether MGMT methylation is preferentially found in SDH-deficient cases (identified by SDHB immunohistochemistry) by analyzing 48 pathogenetically heterogeneous GISTs by methylation-specific PCR, as a premise for possible investigations on the use of alkylating drugs in these tumors. RESULTS Nine GISTs of our series were SDH-deficient, revealing significantly enriched in MGMT-methylated cases (6/9-67%-, vs. 6/39-15%- of SDH-proficient GISTs; p = 0.004). The pathogenetically heterogeneous KIT/PDGFRA-WT GISTs were also significantly MGMT-methylated (11/24-46%-, vs. 1/24-4%- of KIT/PDGFRA-mutant cases, p = 0.002). CONCLUSIONS A subset of KIT/PDGFRA-WT GISTs, including their largest pathogenetically characterized subgroup (i.e., SDH-deficient ones), is preferentially MGMT-methylated. This finding could foster a reappraisal of alkylating agents for treating malignant cases occurring among these overall chemorefractory tumors.
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Affiliation(s)
- Riccardo Ricci
- Department of Pathology, Università Cattolica del Sacro Cuore, Largo F.Vito 1, 00168, Rome, Italy. .,UOC di Anatomia Patologica, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy.
| | - Maurizio Martini
- Department of Pathology, Università Cattolica del Sacro Cuore, Largo F.Vito 1, 00168, Rome, Italy.,UOC di Anatomia Patologica, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
| | - Gloria Ravegnini
- Department of Pharmacy and Biotechnology, University of Bologna, via Massarenti 9, 40138, Bologna, Italy
| | - Tonia Cenci
- UOC di Anatomia Patologica, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
| | - Massimo Milione
- Department of Pathology and Laboratory Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Via Venezian, 20100, Milan, Italy
| | - Paola Lanza
- UOC di Anatomia Patologica, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
| | - Francesco Pierconti
- Department of Pathology, Università Cattolica del Sacro Cuore, Largo F.Vito 1, 00168, Rome, Italy.,UOC di Anatomia Patologica, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
| | - Donatella Santini
- Pathology Unit, S.Orsola-Malpighi Hospital, University of Bologna, via Massarenti 9, 40138, Bologna, Italy
| | - Sabrina Angelini
- Department of Pharmacy and Biotechnology, University of Bologna, via Massarenti 9, 40138, Bologna, Italy
| | - Alberto Biondi
- UOC di Chirurgia Generale, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
| | - Fausto Rosa
- UOC di Chirurgia Digestiva, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
| | - Sergio Alfieri
- UOC di Chirurgia Digestiva, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy.,Department of Surgery, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168, Rome, Italy
| | - Gennaro Clemente
- Department of Surgery, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168, Rome, Italy.,UOC di Chirurgia Generale ed Epato-Biliare, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
| | - Roberto Persiani
- UOC di Chirurgia Generale, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy.,Department of Surgery, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168, Rome, Italy
| | - Alessandra Cassano
- Department of Internal Medicine, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168, Rome, Italy.,UOC di Oncologia Medica, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
| | - Maria A Pantaleo
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, via Massarenti 9, 40138, Bologna, Italy
| | - Luigi M Larocca
- Department of Pathology, Università Cattolica del Sacro Cuore, Largo F.Vito 1, 00168, Rome, Italy.,UOC di Anatomia Patologica, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
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The specific role of O 6-methylguanine-DNA methyltransferase inhibitors in cancer chemotherapy. Future Med Chem 2018; 10:1971-1996. [PMID: 30001630 DOI: 10.4155/fmc-2018-0069] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The DNA repair protein, O6-methylguanine DNA methyltransferase (MGMT), can confer resistance to guanine O6-alkylating agents. Therefore, inhibition of resistant MGMT protein is a practical approach to increase the anticancer effects of such alkylating agents. Numerous small molecule inhibitors were synthesized and exhibited potential MGMT inhibitory activities. Although they were nontoxic alone, they also inhibited MGMT in normal tissues, thereby enhancing the side effects of chemotherapy. Therefore, strategies for tumor-specific MGMT inhibition have been proposed, including local drug delivery and tumor-activated prodrugs. Over-expression of MGMT in hematopoietic stem cells to protect bone marrow from the toxic effects of chemotherapy is also a feasible selection. The future prospects and challenges of MGMT inhibitors in cancer chemotherapy were also discussed.
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Liu C, Yao S, Li X, Wang F, Jiang Y. iRGD-mediated core-shell nanoparticles loading carmustine and O 6-benzylguanine for glioma therapy. J Drug Target 2016; 25:235-246. [PMID: 27646474 DOI: 10.1080/1061186x.2016.1238091] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
iRGD (internalizing RGD) with high affinity to αν integrins was reported to enhance tumor penetrability by binding to neuropilin-1 (NRP-1). Based on our previous study, chitosan surface-modified poly (lactide-co-glycolides) nanoparticles (PLGA/CS NPs), loaded with carmustine (BCNU) and its sensitizer (O6-benzylguanine, BG) showed stronger anti-tumor effect than free drugs. In present study, PLGA/CS NPs (NPs) with core-shell structure were prepared and modified with iRGD or mPEG. F98, C6 or U87 cell lines with different receptors levels were selected for in vitro and in vivo studies. After administration of iRGD-mediated NPs, including iRGD-modified NPs (iRGD-NPs) and co-administration of iRGD and NPs (iRGD + NPs), their effects on glioma were compared with NPs. iRGD-NPs showed stronger cytotoxicity and cellular uptake than other groups. iRGD-NPs and iRGD + NPs displayed deeper tumor penetration and stronger anti-invasion effect on three dimensional (3D) glioma spheroids than NPs. On F98 glioma-bearing mice model, iRGD-mediated NPs showed enhanced crossing BBB ability and brain tumor accumulation levels. Correspondingly, the median survival time of iRGD + NPs, iRGD-NPs and NPs groups were 58, 49 and 34.5 days, respectively. Present studies supported the iRGD-mediated strategy to improve the efficacy of antitumor drug delivery system. Importantly, co-administration of iRGD may be a greater way over the conjugation of iRGD.
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Affiliation(s)
- Chang Liu
- a Key Laboratory of Smart Drug Delivery, Ministry of Education and PLA, Department of pharmaceutics , School of Pharmacy, Fudan University , Shanghai , China
| | - Sen Yao
- a Key Laboratory of Smart Drug Delivery, Ministry of Education and PLA, Department of pharmaceutics , School of Pharmacy, Fudan University , Shanghai , China
| | - Xuqian Li
- a Key Laboratory of Smart Drug Delivery, Ministry of Education and PLA, Department of pharmaceutics , School of Pharmacy, Fudan University , Shanghai , China
| | - Feng Wang
- a Key Laboratory of Smart Drug Delivery, Ministry of Education and PLA, Department of pharmaceutics , School of Pharmacy, Fudan University , Shanghai , China
| | - Yanyan Jiang
- a Key Laboratory of Smart Drug Delivery, Ministry of Education and PLA, Department of pharmaceutics , School of Pharmacy, Fudan University , Shanghai , China
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Abstract
BACKGROUND Predictive assays for cancer treatment are not new technology, but they have failed to meet the criteria necessary for standardized use in clinical decision-making. METHODS The authors summarize the use of predictive assays and the challenges and values associated with these assays in the clinical setting. RESULTS Predictive assays commercially available in the clinical setting are not standardized, have significant obstacles to overcome, and cannot be relied upon by health care professionals due to the limited value these assays provide to the decision-making process for the treatment of patients. CONCLUSIONS A method that more closely recapitulates the human tumor microenvironment and accurately predicts response with high reproducibility would be beneficial to patient outcomes and quality of life.
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Affiliation(s)
- Jenny M Kreahling
- Department of Anatomic Pathology, Moffitt Cancer Center, Tampa, FL 33612, USA.
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7
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Sukumari-Ramesh S, Prasad N, Alleyne CH, Vender JR, Dhandapani KM. Overexpression of Nrf2 attenuates Carmustine-induced cytotoxicity in U87MG human glioma cells. BMC Cancer 2015; 15:118. [PMID: 25851054 PMCID: PMC4365816 DOI: 10.1186/s12885-015-1134-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 02/24/2015] [Indexed: 01/07/2023] Open
Abstract
Background Malignant glioma is one of the most devastating tumors in adults with poor patient prognosis. Notably, glioma often exhibits resistance to conventional chemotherapeutic approaches, complicating patient treatments. However, the molecular mediators involved in tumor chemoresistance remain poorly defined, creating a barrier to the successful management of glioma. In the present study, we hypothesized that the antioxidant transcription factor, Nrf2 (nuclear factor erythroid-derived 2 like 2), attenuates glioma cytotoxicity to Carmustine (BCNU), a widely used chemotherapeutic agent known to modulate cellular oxidative balance. Methods To test the hypothesis, we employed human malignant glioma cell line, U87MG and overexpression of Nrf2 in glioma cells was achieved using both pharmacological and genetic approaches. Results Notably, induction of Nrf2 was associated with increased expression of heme oxygenase-1 (HO-1), a stress inducible enzyme involved in anti-oxidant defense. In addition, over expression of Nrf2 in U87MG cells significantly attenuated the cytotoxicity of Carmustine as evidenced by both cellular viability assay and flow cytometry analysis. Consistent with this, antioxidants such as glutathione and N-acetyl cysteine significantly reduced Carmustine mediated glioma cytotoxicity. Conclusions Taken together, these data strongly implicate an unexplored role of Nrf2 in glioma resistance to Carmustine and raise the possible use of Nrf2 inhibitors as adjunct to Carmustine for the treatment of malignant glioma. Electronic supplementary material The online version of this article (doi:10.1186/s12885-015-1134-z) contains supplementary material, which is available to authorized users.
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8
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Canello T, Ovadia H, Refael M, Zrihan D, Siegal T, Lavon I. Antineoplastic effect of decoy oligonucleotide derived from MGMT enhancer. PLoS One 2014; 9:e113854. [PMID: 25460932 PMCID: PMC4252043 DOI: 10.1371/journal.pone.0113854] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 10/31/2014] [Indexed: 12/13/2022] Open
Abstract
Silencing of O(6)-methylguanine-DNA-methyltransferase (MGMT) in tumors, mainly through promoter methylation, correlates with a better therapeutic response and with increased survival. Therefore, it is conceivable to consider MGMT as a potential therapeutic target for the treatment of cancers. Our previous results demonstrated the pivotal role of NF-kappaB in MGMT expression, mediated mainly through p65/NF-kappaB homodimers. Here we show that the non-canonical NF-KappaB motif (MGMT-kappaB1) within MGMT enhancer is probably the major inducer of MGMT expression following NF-kappaB activation. Thus, in an attempt to attenuate the transcription activity of MGMT in tumors we designed locked nucleic acids (LNA) modified decoy oligonucleotides corresponding to the specific sequence of MGMT-kappaB1 (MGMT-kB1-LODN). Following confirmation of the ability of MGMT-kB1-LODN to interfere with the binding of p65/NF-kappaB to the NF-KappaB motif within MGMT enhancer, the efficacy of the decoy was studied in-vitro and in-vivo. The results of these experiments show that the decoy MGMT-kB1-LODN have a substantial antineoplastic effect when used either in combination with temozolomide or as monotherapy. Our results suggest that MGMT-kB1-LODN may provide a novel strategy for cancer therapy.
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Affiliation(s)
- Tamar Canello
- Leslie and Michael Gaffin Center for Neuro-Oncology and Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Haim Ovadia
- Leslie and Michael Gaffin Center for Neuro-Oncology and Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Miri Refael
- Leslie and Michael Gaffin Center for Neuro-Oncology and Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Daniel Zrihan
- Leslie and Michael Gaffin Center for Neuro-Oncology and Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Tali Siegal
- Leslie and Michael Gaffin Center for Neuro-Oncology and Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Iris Lavon
- Leslie and Michael Gaffin Center for Neuro-Oncology and Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew University Medical Center, Jerusalem, Israel
- * E-mail:
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Julsing JR, Peters GJ. Methylation of DNA repair genes and the efficacy of DNA targeted anticancer treatment. ACTA ACUST UNITED AC 2014. [DOI: 10.7243/2052-6199-2-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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10
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Qian L, Zheng J, Wang K, Tang Y, Zhang X, Zhang H, Huang F, Pei Y, Jiang Y. Cationic core-shell nanoparticles with carmustine contained within O⁶-benzylguanine shell for glioma therapy. Biomaterials 2013; 34:8968-78. [PMID: 23953782 DOI: 10.1016/j.biomaterials.2013.07.097] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 07/28/2013] [Indexed: 12/18/2022]
Abstract
The application of carmustine (BCNU) for glioma treatment is limited due to its poor selectivity for tumor and tumor resistance caused by O⁶-methylguanine-DNA-methyl transferase (MGMT). To improve the efficacy of BCNU, we constructed chitosan surface-modified poly (lactide-co-glycolides) nanoparticles (PLGA/CS NPs) for targeting glioma, loading BCNU along with O⁶-benzylguanine (BG), which could directly deplete MGMT. With core-shell structure, PLGA/CS NPs in the diameter around 177 nm showed positive zeta potential. In vitro plasma stability of BCNU in NPs was improved compared with free BCNU. The cellular uptake of NPs increased with surface modification of CS and decreasing particle size. The cytotoxicity of BCNU against glioblastoma cells was enhanced after being encapsulated into NPs; furthermore, with the co-encapsulation of BCNU and BG into NPs, BCNU + BG PLGA/CS NPs showed the strongest inhibiting ability. Compared to free drugs, PLGA/CS NPs could prolong circulation time and enhance accumulation in tumor and brain. Among all treatment groups, F98 glioma-bearing rats treated with BCNU + BG PLGA/CS NPs showed the longest survival time and the smallest tumor size. The studies suggested that the co-encapsulation of BCNU and BG into PLGA/CS NPs could remarkably enhance the efficacy of BCNU, accompanied with greater convenience for therapy.
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Affiliation(s)
- Lili Qian
- Key Laboratory of Smart Drug Delivery, Ministry of Education, Department of Pharmaceutics, School of Pharmacy, Fudan University, Lane 826, Zhang Heng Road, Shanghai 201203, PR China
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Tawbi HA, Beumer JH, Tarhini AA, Moschos S, Buch SC, Egorin MJ, Lin Y, Christner S, Kirkwood JM. Safety and efficacy of decitabine in combination with temozolomide in metastatic melanoma: a phase I/II study and pharmacokinetic analysis. Ann Oncol 2012; 24:1112-9. [PMID: 23172636 DOI: 10.1093/annonc/mds591] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Temozolomide (TMZ) is widely used for chemotherapy of metastatic melanoma. We hypothesized that epigenetic modulators will reverse chemotherapy resistance, and in this article, we report studies that sought to determine the recommended phase 2 dose (RP2D), safety, and efficacy of decitabine (DAC) combined with TMZ. PATIENTS AND METHODS In phase I, DAC was given at two dose levels: 0.075 and 0.15 mg/kg intravenously daily × 5 days/week for 2 weeks, TMZ orally 75 mg/m(2) qd for weeks 2-5 of a 6-week cycle. The phase II portion used a two-stage Simon design with a primary end point of objective response rate (ORR). RESULTS The RP2D is DAC 0.15 mg/kg and TMZ 75 mg/m(2). The phase II portion enrolled 35 patients, 88% had M1c disease; 42% had history of brain metastases. The best responses were 2 complete response (CR), 4 partial response (PR), 14 stable disease (SD), and 13 progressive disease (PD); 18% ORR and 61% clinical benefit rate (CR + PR + SD). The median overall survival (OS) was 12.4 months; the 1-year OS rate was 56%. Grade 3/4 neutropenia was common but lasted >7 days in six patients. CONCLUSIONS The combination of DAC and TMZ is safe, leads to 18% ORR and 12.4-month median OS, suggesting possible superiority over the historical 1-year OS rate, and warrants further evaluation in a randomized setting.
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Affiliation(s)
- H A Tawbi
- Department of Medicine/Division of Hematology/Oncology, School of Medicine, University of Pittsburgh, Pittsburgh 15232, USA.
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Apisarnthanarax N, Wood GS, Stevens SR, Carlson S, Chan DV, Liu L, Szabo SK, Fu P, Gilliam AC, Gerson SL, Remick SC, Cooper KD. Phase I clinical trial of O6-benzylguanine and topical carmustine in the treatment of cutaneous T-cell lymphoma, mycosis fungoides type. ACTA ACUST UNITED AC 2012; 148:613-20. [PMID: 22250189 DOI: 10.1001/archdermatol.2011.2797] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVES To evaluate the toxic effects and maximum tolerated dose of topical carmustine [1,3-bis(2-chloroethyl)-1-nitrosourea] following intravenous O6-benzylguanine in the treatment of cutaneous T-cell lymphoma (CTCL), and to determine pharmacodynamics of O6-alkylguanine DNA alkyltransferase activity in treated CTCL lesions. DESIGN Open-label, dose-escalation, phase I trial. SETTING Dermatology outpatient clinic and clinical research unit at a university teaching hospital. PATIENTS A total of 21 adult patients (11 male, 10 female)with early-stage (IA-IIA) refractory CTCL, mycosis fungoides type, treated with topical carmustine following intravenous O6-benzylguanine. INTERVENTION Treatment once every 2 weeks with 120 mg/m(2) intravenous O6-benzylguanine followed 1 hour later by whole-body, low-dose topical carmustine starting at 10 mg, with 10-mg incremental dose-escalation in 3 patient cohorts. Cutaneous T-cell lymphoma lesional skin biopsy specimens were taken at baseline and 6 hours, 24 hours, and 1 week after the first O6-benzylguanine infusion for analysis of O6-alkylguanine-DNA alkyltransferase activity. MAIN OUTCOME MEASURES Clinical response measured by physical examination and severity-weighted assessment tool measurements, safety data acquired by review of adverse events at study visits, and O6-alkylguanine-DNA alkyltransferase activity in treated lesion skin biopsy specimens. RESULTS A minimal toxic effect was observed through the 40-mg carmustine dose level with 76% of adverse events being grade 1 based on the National Cancer Institute Common Terminology Criteria for Adverse Events. Mean baseline O6-alkylguanine-DNA alkyltransferase activity in CTCL lesions was 3 times greater than in normal controls and was diminished by a median of 100% at 6 and 24 hours following O6-benzylguanine with recovery at 1 week. Clinical disease reduction correlated positively with O6-alkylguanine-DNA alkyltransferase activity at 168 hours (P=.02) and inversely with area under the curve of O6-alkylguanine-DNA alkyltransferase over 1 week (P=.01). Twelve partial responses and 4 complete responses were observed (overall response, 76% [95% CI, 0.55-0.89]). Five patients discontinued therapy owing to adverse events with a possible, probable, or definite relationship to the study drug. CONCLUSION O6-benzylguanine significantly depletes O6-alkylguanine-DNA alkyltransferase in CTCL lesions and in combination with topical carmustine is well tolerated and shows meaningful clinical responses in CTCL at markedly reduced total carmustine treatment doses.
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Bujko M, Kowalewska M, Danska-Bidzinska A, Bakula-Zalewska E, Siedecki JA, Bidzinski M. The promoter methylation and expression of the O6-methylguanine-DNA methyltransferase gene in uterine sarcoma and carcinosarcoma. Oncol Lett 2012; 4:551-555. [PMID: 22970054 DOI: 10.3892/ol.2012.771] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 06/08/2012] [Indexed: 11/05/2022] Open
Abstract
O6-methylguanine-DNA methyltransferase (MGMT) gene promoter hypermethylation is observed in a number of solid tumors and is correlated with the silencing of MGMT expression. In glioblastoma patients treated with the alkylating agent temozolomide, MGMT gene methylation status was shown to have predictive value in terms of prolonged overall survival. Recently, temozolomide has demonstrated promising activity in the treatment of soft tissue sarcomas, including those of the uterus. The tissue specimens involving tumor samples and normal uterine fragments were obtained from nine patients with smooth muscle uterine sarcoma, 11 with stromal uterine sarcoma and 17 with mixed uterine tumors. MGMT gene promoter methylation was analyzed by combined bisulfite restriction analysis (COBRA) while its expression levels were assessed using the real-time reverse transcription polymerase chain reaction (qRT-PCR). MGMT promoter methylation was observed in 27% of all tumor samples analyzed. When stratified by the disease type, 55.5% (5/9) of smooth muscle sarcomas, 23.5% (4/17) of mixed uterine tumor tissues and 9% (1/11) of stromal sarcomas showed MGMT methylation. The MGMT promoter methylation was associated with lower levels of gene expression in tumors when compared with those with an unmethylated promoter (P=0.0232) or normal tissues (P=0.0141). To conclude, MGMT promoter methylation and downregulation of gene expression is observed in a fraction of carcinosarcomas and non-epithelial malignant tumors of corpus uteri. The assessment of MGMT promoter methylation status may potentially identify patients who would benefit from temozolomide treatment.
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Affiliation(s)
- Mateusz Bujko
- Department of Molecular Biology, Maria Sklodowska-Curie Memorial Cancer Centre and Institute of Oncology, 02-781 Warsaw, Poland
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14
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Reed D, Altiok S. Metastatic soft tissue sarcoma chemotherapy: an opportunity for personalized medicine. Cancer Control 2011; 18:188-95. [PMID: 21666581 DOI: 10.1177/107327481101800306] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Soft tissue sarcoma (STS) includes biologically and histologically diverse mesenchymal tumors that are relatively chemotherapy-resistant compared with other sarcoma subtypes. METHODS The authors discuss the clinical challenges frequently encountered by medical oncologists and review the literature for predictive strategies to systematically approach chemotherapy decision making. RESULTS There are no clinically validated predictive tests for chemotherapeutic response or resistance in STS. Clinical features including histology, stage, and patient age are currently used to guide therapy decisions in STS. CONCLUSIONS A method to predict response or resistance to chemotherapy, utilizing both targeted and conventional agents, would be beneficial in reducing toxicity and improving response rates for patients with STS and also in designing clinical trials for this disease.
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Affiliation(s)
- Damon Reed
- Department of Sarcoma at The H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL 33612, USA.
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15
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Tawbi HA, Villaruz L, Tarhini A, Moschos S, Sulecki M, Viverette F, Shipe-Spotloe J, Radkowski R, Kirkwood JM. Inhibition of DNA repair with MGMT pseudosubstrates: phase I study of lomeguatrib in combination with dacarbazine in patients with advanced melanoma and other solid tumours. Br J Cancer 2011; 105:773-7. [PMID: 21811257 PMCID: PMC3171007 DOI: 10.1038/bjc.2011.285] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Background: The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) reverses the O6-methylguanine (O6-meG) lesion induced by dacarbazine. Depletion of MGMT can be achieved using O6-meG pseudosubstrates. Herein, we report the first phase I experience of the novel O6-meG pseudosubstrate lomeguatrib, combined with dacarbazine. Methods: This is a phase I dose-escalation study to determine the maximum tolerated dose and recommended phase II dose (RP2D) of lomeguatrib combined with a single dose of dacarbazine on a 21-day schedule. Results: The vast majority of the 41 patients enrolled had metastatic melanoma (36/41) and most had no previous chemotherapy (30/41). The most frequent non-hematological adverse events (AEs) were nausea (52%), and fatigue (42%). The most frequent AEs of grade 3–4 severity were neutropaenia (42%), leukopaenia (17%), and thrombocytopaenia (12%). Only 1 patient had a partial response and 10 patients had stable disease. Conclusion: The RP2D of lomeguatrib was 40 mg orally twice daily for 10 days combined with 400 mg m−2 of dacarbazine IV on day 2. Oral administration of lomeguatrib substantially increases the haematological toxicity of dacarbazine consistent with experience with other O6-meG pseudosubstrates.
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Affiliation(s)
- H A Tawbi
- Melanoma and Skin Cancer Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA.
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16
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Penel N, Van Glabbeke M, Marreaud S, Ouali M, Blay J, Hohenberger P. Testing new regimens in patients with advanced soft tissue sarcoma: analysis of publications from the last 10 years. Ann Oncol 2011; 22:1266-1272. [DOI: 10.1093/annonc/mdq608] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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17
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Abstract
Many cytotoxic agents used in cancer treatment exert their effects through their ability to directly or indirectly damage DNA and thus resulting in cell death. Major types of DNA damage induced by anticancer treatment include strand breaks (double or single strand), crosslinks (inter-strand, intra-strand, DNA-protein crosslinks), and interference with nucleotide metabolism and DNA synthesis. On the other hand, cancer cells activate various DNA repair pathways and repair DNA damages induced by cytotoxic drugs. The purpose of the current review is to present the major types of DNA damage induced by cytotoxic agents, DNA repair pathways, and their role as predictive agents, as well as evaluate the future perspectives of the novel DNA repair pathways inhibitors in cancer therapeutics.
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Affiliation(s)
- Athanasios G Pallis
- Department of Medical Oncology, University General Hospital of Heraklion, Heraklion, Greece
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Kaina B, Margison GP, Christmann M. Targeting O⁶-methylguanine-DNA methyltransferase with specific inhibitors as a strategy in cancer therapy. Cell Mol Life Sci 2010; 67:3663-81. [PMID: 20717836 PMCID: PMC11115711 DOI: 10.1007/s00018-010-0491-7] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 07/28/2010] [Indexed: 11/29/2022]
Abstract
O (6)-methylguanine-DNA methyltransferase (MGMT) repairs the cancer chemotherapy-relevant DNA adducts, O (6)-methylguanine and O (6)-chloroethylguanine, induced by methylating and chloroethylating anticancer drugs, respectively. These adducts are cytotoxic, and given the overwhelming evidence that MGMT is a key factor in resistance, strategies for inactivating MGMT have been pursued. A number of drugs have been shown to inactivate MGMT in cells, human tumour models and cancer patients, and O (6)-benzylguanine and O (6)-[4-bromothenyl]guanine have been used in clinical trials. While these agents show no side effects per se, they also inactivate MGMT in normal tissues and hence exacerbate the toxic side effects of the alkylating drugs, requiring dose reduction. This might explain why, in any of the reported trials, the outcome has not been improved by their inclusion. It is, however, anticipated that, with the availability of tumour targeting strategies and hematopoetic stem cell protection, MGMT inactivators hold promise for enhancing the effectiveness of alkylating agent chemotherapy.
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Affiliation(s)
- Bernd Kaina
- Institute of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, 55131, Mainz, Germany.
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19
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Zhu Y, Hu J, Hu Y, Liu W. Targeting DNA repair pathways: a novel approach to reduce cancer therapeutic resistance. Cancer Treat Rev 2009; 35:590-6. [PMID: 19635647 DOI: 10.1016/j.ctrv.2009.06.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 06/16/2009] [Accepted: 06/22/2009] [Indexed: 01/04/2023]
Abstract
Increased chemo-resistance and radio-resistance of cancer cells is a major obstacle in the treatment and management of malignant cancers. An important mechanism that underlies the development of such therapeutic resistance is that cancer cells recognize DNA lesions induced by DNA-damaging agents and by ionizing radiation, and repair these lesions by activating various DNA repair pathways. Therefore, Use of pharmacological agents that can inhibit certain DNA repair pathways in cancer cells has the potential for enhancing the targeted cytotoxicity of anticancer treatments and reversing the associated therapeutic resistance associated with DNA repair; such agents, offering a promising opportunity to achieve better therapeutic efficacy. Here we review the major DNA repair pathways and discuss recent advances in the development of novel inhibitors of DNA repair pathways; many of these agents are under preclinical/clinical investigation.
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Affiliation(s)
- Yongjian Zhu
- Department of Neurosurgery, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China.
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20
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Inactivation of O6-methylguanine-DNA methyltransferase in soft tissue sarcomas: association with K-ras mutations. Hum Pathol 2009; 40:934-41. [PMID: 19356788 DOI: 10.1016/j.humpath.2009.01.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 01/05/2009] [Accepted: 01/09/2009] [Indexed: 11/22/2022]
Abstract
The DNA-repair protein O(6)-methylguanine-DNA methyltransferase removes alkyl adducts from the O(6)-position of guanine. The adducts can mispair with T during DNA replication, resulting in a G-to-A mutation. Epigenetic inactivation of O(6)-methylguanine-DNA methyltransferase has been found in human neoplasia and is considered one of the implicated factors in chemoresistance. Sixty-two patients with soft tissue sarcomas were analyzed with regard to the status of O(6)-methylguanine-DNA methyltransferase protein expression status using immunohistochemistry and promoter hypermethylation of the MGMT gene using methylation-specific PCR. G-to-A transitions in codons 12 and 13 of the K-ras oncogene were investigated using PCR and direct automated sequencing analysis. A loss of O(6)-methylguanine-DNA methyltransferase expression was noted in 20 (32.3%) cases of 62 total soft tissue sarcomas. The MGMT promoter hypermethylation rate was 33.9% (21/62 cases). Of the 54 sarcomas evaluated, K-ras mutations were found in only 2 (3.7%) cases. Loss of O(6)-methylguanine-DNA methyltransferase expression and MGMT promoter hypermethylation showed a significant association with high American Joint Committee on Cancer stage, high French Federation of Cancer Centers grade, and aggressive behavior. On multivariate analysis, these were not an independently significant prognostic factors. However, when the group receiving chemotherapy was analyzed (n = 27), loss of O(6)-methylguanine-DNA methyltransferase expression was correlated with worse survival on multivariate analysis (P = .024). MGMT promoter hypermethylation status had a strong correlation with loss of O(6)-methylguanine-DNA methyltransferase expression (P = .000). Our results suggest that MGMT promoter hypermethylation and loss of O(6)-methylguanine-DNA methyltransferase expression tend to be associated with poor prognosis and that the loss of O(6)-methylguanine-DNA methyltransferase protein expression frequently occurs via MGMT promoter hypermethylation. However, MGMT promoter hypermethylation was not significantly associated with point mutations of K-ras at codons 12 and 13 in sarcomas.
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Plummer R, Jones C, Middleton M, Wilson R, Evans J, Olsen A, Curtin N, Boddy A, McHugh P, Newell D, Harris A, Johnson P, Steinfeldt H, Dewji R, Wang D, Robson L, Calvert H. Phase I study of the poly(ADP-ribose) polymerase inhibitor, AG014699, in combination with temozolomide in patients with advanced solid tumors. Clin Cancer Res 2008; 14:7917-23. [PMID: 19047122 PMCID: PMC2652879 DOI: 10.1158/1078-0432.ccr-08-1223] [Citation(s) in RCA: 274] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE One mechanism of tumor resistance to cytotoxic therapy is repair of damaged DNA. Poly(ADP-ribose) polymerase (PARP)-1 is a nuclear enzyme involved in base excision repair, one of the five major repair pathways. PARP inhibitors are emerging as a new class of agents that can potentiate chemotherapy and radiotherapy. The article reports safety, efficacy, pharmacokinetic, and pharmacodynamic results of the first-in-class trial of a PARP inhibitor, AG014699, combined with temozolomide in adults with advanced malignancy. EXPERIMENTAL DESIGN Initially, patients with solid tumors received escalating doses of AG014699 with 100 mg/m2/d temozolomide x 5 every 28 days to establish the PARP inhibitory dose (PID). Subsequently, AG014699 dose was fixed at PID and temozolomide escalated to maximum tolerated dose or 200 mg/m2 in metastatic melanoma patients whose tumors were biopsied. AG014699 and temozolomide pharmacokinetics, PARP activity, DNA strand single-strand breaks, response, and toxicity were evaluated. RESULTS Thirty-three patients were enrolled. PARP inhibition was seen at all doses; PID was 12 mg/m2 based on 74% to 97% inhibition of peripheral blood lymphocyte PARP activity. Recommended doses were 12 mg/m2 AG014699 and 200 mg/m2 temozolomide. Mean tumor PARP inhibition at 5 h was 92% (range, 46-97%). No toxicity attributable to AG014699 alone was observed. AG014699 showed linear pharmacokinetics with no interaction with temozolomide. All patients treated at PID showed increases in DNA single-strand breaks and encouraging evidence of activity was seen. CONCLUSIONS The combination of AG014699 and temozolomide is well tolerated, pharmacodynamic assessments showing proof of principle of the mode of action of this new class of agents.
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Affiliation(s)
- Ruth Plummer
- Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom.
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22
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Mellor HR, Callaghan R. Resistance to chemotherapy in cancer: a complex and integrated cellular response. Pharmacology 2008; 81:275-300. [PMID: 18259091 DOI: 10.1159/000115967] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Accepted: 09/10/2007] [Indexed: 12/30/2022]
Abstract
Inherent and acquired resistance pathways account for the high rate of failure in cancer chemotherapy. The mechanisms or pathways mediating resistance may be classified as pharmacokinetic (i.e. alter intratumour drug exposue) or pharmacodynamic (i.e. failure to elicit cytotoxicity). More often than not, the resistant phenotype is characterised by alterations in multiple pathways. Consequently, the pathways may act synergistically or generate a broad spectrum of resistance to anticancer drugs. There has been a great deal of systematic characterisation of drug resistance in vitro. However, translating this greater understanding into clinical efficacy has rarely been achieved. This review explores the phenomenon of drug resistance in cancer and highlights the gap between in vitro and in vivo observations. This gap presents a major obstacle in overcoming drug resistance and restoring sensitivity to chemotherapy.
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Affiliation(s)
- Howard R Mellor
- Growth Factor Group, Weatherall Institute of Molecular Medicine, Oxford, UK
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24
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Khan O, Middleton MR. The therapeutic potential ofO6-alkylguanine DNA alkyltransferase inhibitors. Expert Opin Investig Drugs 2007; 16:1573-84. [DOI: 10.1517/13543784.16.10.1573] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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25
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Milsom MD, Williams DA. Live and let die: in vivo selection of gene-modified hematopoietic stem cells via MGMT-mediated chemoprotection. DNA Repair (Amst) 2007; 6:1210-21. [PMID: 17482893 PMCID: PMC2064866 DOI: 10.1016/j.dnarep.2007.03.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Gene transfer into hematopoietic stem cells (HSC) provides a potential means of correcting monogenic defects and altering drug sensitivity of normal bone marrow to cytotoxic agents. These applications have significant therapeutic potential but the translation of successful murine studies into human therapies has been hindered by low gene transfer in large animals (including humans), and recent serious side effects in a human immunodeficiency trial related to insertional mutagenesis. The latter trial, along with other subsequent trials, while bringing into focus the potential risks of integrating vector systems, also clearly demonstrate the potential usefulness of in vivo selection as it relates to inefficient stem cell transduction. Developing from initial studies by our group and other investigators in which drug resistance was utilized to demonstrate the feasibility of using gene transfer to effect protection from myelotoxicity of chemotherapeutic agents, expression of mutant forms of O(6)-methyguanine-DNA-methytransferase (MGMT) coupled with the simultaneous use of pharmacologic inhibitors and chemotherapeutic agents has been shown to provide a powerful method to select HSC in vivo. While stem and progenitor cell protection and resulting selection in vivo has potential applications for the treatment of selected cancers (allowing dose escalation) and for correction of monogenic disease (allowing an iatrogenic survival advantage of transduced cells in vivo), such an in vivo selection may have untoward effects on stem cell behavior. These deleterious effects may include stem cell exhaustion; lineage skewing; accumulation of genotoxic lesions; and clonal dominance driven towards a pro-leukemic phenotype. Knowledge of the likelihood of such deleterious events occurring as well as their potential implications will be critical to future clinical applications and may also enhance our understanding of both normal stem cell behavior and the evolution of hematopoietic malignancies.
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Affiliation(s)
- Michael D Milsom
- Cincinnati Children's Research Foundation, Cincinnati Children's Hospital Medical Center, Division of Experimental Hematology, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
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26
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Tubbs JL, Pegg AE, Tainer JA. DNA binding, nucleotide flipping, and the helix-turn-helix motif in base repair by O6-alkylguanine-DNA alkyltransferase and its implications for cancer chemotherapy. DNA Repair (Amst) 2007; 6:1100-15. [PMID: 17485252 PMCID: PMC1993358 DOI: 10.1016/j.dnarep.2007.03.011] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
O(6)-Alkylguanine-DNA alkyltransferase (AGT) is a crucial target both for the prevention of cancer and for chemotherapy, since it repairs mutagenic lesions in DNA, and it limits the effectiveness of alkylating chemotherapies. AGT catalyzes the unique, single-step, direct damage reversal repair of O(6)-alkylguanines by selectively transferring the O(6)-alkyl adduct to an internal cysteine residue. Recent crystal structures of human AGT alone and in complex with substrate DNA reveal a two-domain alpha/beta fold and a bound zinc ion. AGT uses its helix-turn-helix motif to bind substrate DNA via the minor groove. The alkylated guanine is then flipped out from the base stack into the AGT active site for repair by covalent transfer of the alkyl adduct to Cys145. An asparagine hinge (Asn137) couples the helix-turn-helix DNA binding and active site motifs. An arginine finger (Arg128) stabilizes the extrahelical DNA conformation. With this newly improved structural understanding of AGT and its interactions with biologically relevant substrates, we can now begin to unravel the role it plays in preserving genetic integrity and discover how it promotes resistance to anticancer therapies.
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Affiliation(s)
- Julie L. Tubbs
- The Scripps Research Institute, The Skaggs Institute for Chemical Biology and Department of Molecular Biology, 10550 North Torrey Pines Road, MB4, La Jolla, CA 92037
| | - Anthony E. Pegg
- Department of Cellular and Molecular Physiology, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - John A. Tainer
- The Scripps Research Institute, The Skaggs Institute for Chemical Biology and Department of Molecular Biology, 10550 North Torrey Pines Road, MB4, La Jolla, CA 92037
- Life Sciences Division, Department of Molecular Biology, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- *To whom correspondence should be addressed: Tel: +1-858-784-8119; fax: +1-858-784-2289;
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Rabik CA, Njoku MC, Dolan ME. Inactivation of O6-alkylguanine DNA alkyltransferase as a means to enhance chemotherapy. Cancer Treat Rev 2006; 32:261-76. [PMID: 16698182 DOI: 10.1016/j.ctrv.2006.03.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 03/14/2006] [Accepted: 03/15/2006] [Indexed: 10/24/2022]
Abstract
DNA adducts at the O6-position of guanine are a result of the carcinogenic, mutagenic and cytotoxic actions of methylating and chloroethylating agents. The presence of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT) renders cells resistant to the biological effects induced by agents that attack at this position. O6-Benzylguanine (O6-BG) is a low molecular weight substrate of AGT and therefore, results in sensitizing cells and tumors to alkylating agent-induced cytotoxicity and antitumor activity. Presently, chemotherapy regimens of O6-BG in combination with BCNU, temozolomide and Gliadel are in clinical development. Other ongoing clinical trials include expression of mutant AGT proteins that confer resistance to O6-BG in bone marrow stem cells, in an effort to reduce the potential enhanced toxicity and mutagenicity of alkylating agents in the bone marrow. O6-BG has also been found to enhance the cytotoxicity of agents that do not form adducts at the O6-position of DNA, including platinating agents. O6-BG's mechanism of action with these agents is not fully understood; however, it is independent of AGT activity or AGT inactivation. A better understanding of the effects of this agent will contribute to its clinical usefulness and the design of better analogs to further improve cancer chemotherapy.
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Affiliation(s)
- Cara A Rabik
- Department of Medicine, Committee on Cancer Biology, Committee on Clinical Pharmacology and Pharmacogenomics, University of Chicago, Chicago, IL 60637, USA
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