RESUMEN
Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is caused by loss of function mutations in fumarate hydratase (FH) and results in an aggressive subtype of renal cell carcinoma with limited treatment options. Loss of FH leads to accumulation of fumarate, an oncometabolite that disrupts multiple cellular processes and drives tumor progression. High levels of fumarate inhibit alpha ketoglutarate-dependent dioxygenases, including the ten eleven translocation (TET) enzymes and can lead to global DNA hypermethylation. Here, we report patterns of hypermethylation in FH-mutant cell lines and tumor samples are associated with silencing of nicotinate phosphoribosyl transferase (NAPRT), a rate-limiting enzyme in the Preiss-Handler pathway of NAD+ biosynthesis in a subset of HLRCC cases. NAPRT is hypermethylated at a CpG island in the promoter in cell line models and patient samples, resulting in loss of NAPRT expression. We find that FH-deficient RCC models with loss of NAPRT expression, as well as other oncometabolite-producing cancer models that silence NAPRT, are extremely sensitive to nicotinamide phosphoribosyl transferase inhibitors (NAMPTis). NAPRT silencing was also associated with synergistic tumor cell killing with poly(ADP)-ribose polymerase inhibitors (PARPis) and NAMPTis, which was associated with effects on PAR-mediated DNA repair. Overall, our findings indicate that NAPRT-silencing can be targeted in oncometabolite-producing cancers and elucidates how oncometabolite associated hypermethylation can impact diverse cellular processes and leads to therapeutically relevant vulnerabilities in cancer cells. Implications: NAPRT is a novel biomarker for targeting NAD+ metabolism in FH-deficient HLRCCs with NAMPTis alone and targeting DNA repair processes with the combination of NAMPTis and PARPis.
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Aberrant DNA repair is a hallmark of cancer, and many tumors display reduced DNA repair capacities that sensitize them to genotoxins. Here, we demonstrate that the differential DNA repair capacities of healthy and transformed tissue may be exploited to obtain highly selective chemotherapies. We show that the novel N3-(2-fluoroethyl)imidazotetrazine "KL-50" is a selective toxin toward tumors that lack the DNA repair protein O6-methylguanine-DNA-methyltransferase (MGMT), which reverses the formation of O6-alkylguanine lesions. We establish that KL-50 generates DNA interstrand cross-links (ICLs) by a multistep process comprising DNA alkylation to generate an O6-(2-fluoroethyl)guanine (O6FEtG) lesion, slow unimolecular displacement of fluoride to form an N1,O6-ethanoguanine (N1,O6EtG) intermediate, and ring-opening by the adjacent cytidine. The slow rate of N1,O6EtG formation allows healthy cells expressing MGMT to reverse the initial O6FEtG lesion before it evolves to N1,O6EtG, thereby suppressing the formation of toxic DNA-MGMT cross-links and reducing the amount of DNA ICLs generated in healthy cells. In contrast, O6-(2-chloroethyl)guanine lesions produced by agents such as lomustine and the N3-(2-chloroethyl)imidazotetrazine mitozolomide rapidly evolve to N1,O6EtG, resulting in the formation of DNA-MGMT cross-links and DNA ICLs in healthy tissue. These studies suggest that careful consideration of the rates of chemical DNA modification and biochemical DNA repair may lead to the identification of other tumor-specific genotoxic agents.
Asunto(s)
Neoplasias Encefálicas , Resistencia a Antineoplásicos , Humanos , Resistencia a Antineoplásicos/efectos de los fármacos , Neoplasias Encefálicas/tratamiento farmacológico , Neoplasias Encefálicas/patología , Antineoplásicos/farmacología , Antineoplásicos/química , Antineoplásicos/síntesis química , Antineoplásicos/uso terapéutico , Línea Celular Tumoral , Reparación del ADN/efectos de los fármacos , O(6)-Metilguanina-ADN Metiltransferasa/metabolismo , O(6)-Metilguanina-ADN Metiltransferasa/antagonistas & inhibidores , Imidazoles/química , Imidazoles/farmacología , Imidazoles/uso terapéuticoRESUMEN
The treatment of primary central nervous system tumors is challenging due to the blood-brain barrier and complex mutational profiles, which is associated with low survival rates. However, recent studies have identified common mutations in gliomas [isocitrate dehydrogenase (IDH)-wild-type and mutant, WHO grades II-IV; with grade IV tumors referred to as glioblastomas (GBM)]. These mutations drive epigenetic changes, leading to promoter methylation at the nicotinic acid phosphoribosyl transferase (NAPRT) gene locus, which encodes an enzyme involved in generating NAD+. Importantly, NAPRT silencing introduces a therapeutic vulnerability to inhibitors targeting another NAD+ biogenesis enzyme, nicotinamide phosphoribosyl transferase (NAMPT), rationalizing a treatment for these malignancies. Multiple systemically administered NAMPT inhibitors (NAMPTi) have been developed and tested in clinical trials, but dose-limiting toxicities-including bone marrow suppression and retinal toxicity-have limited their efficacy. Here, we report a novel approach for the treatment of NAPRT-silenced GBMs using nanoparticle (NP)-encapsulated NAMPTis administered by convection-enhanced delivery (CED). We demonstrate that GMX1778 (a NAMPTi) can be formulated in degradable polymer NPs with retention of potency for NAMPT inhibition and anticancer activity in vitro, plus sustained drug release in vitro and in vivo. Direct injection of these drugs via CED into the brain is associated with reduced retinal toxicity compared with systemic administration. Finally, we show that CED of NP-encapsulated GMX1778 to NAPRT-silenced intracranial GBM xenografts in mice exhibit significant tumor growth delay and extends survival. These data support an approach to treat gliomas harboring defects in NAD+ metabolism using CED of NP-encapsulated NAMPTis to greatly improve the therapeutic index and treatment efficacy for this class of drugs.
Asunto(s)
Glioma , Nanopartículas , Nicotinamida Fosforribosiltransferasa , Nicotinamida Fosforribosiltransferasa/antagonistas & inhibidores , Humanos , Animales , Ratones , Nanopartículas/química , Glioma/tratamiento farmacológico , Glioma/patología , Citocinas/metabolismo , Ensayos Antitumor por Modelo de Xenoinjerto , Línea Celular Tumoral , Neoplasias Encefálicas/tratamiento farmacológico , Neoplasias Encefálicas/patologíaRESUMEN
Loss-of-function mutations in genes encoding the Krebs cycle enzymes Fumarate Hydratase (FH) and Succinate Dehydrogenase (SDH) induce accumulation of fumarate and succinate, respectively and predispose patients to hereditary cancer syndromes including the development of aggressive renal cell carcinoma (RCC). Fumarate and succinate competitively inhibit αKG-dependent dioxygenases, including Lysine-specific demethylase 4A/B (KDM4A/B), leading to suppression of the homologous recombination (HR) DNA repair pathway. In this study, we have developed new syngeneic Fh1- and Sdhb-deficient murine models of RCC, which demonstrate the expected accumulation of fumarate and succinate, alterations in the transcriptomic and methylation profile, and an increase in unresolved DNA double-strand breaks (DSBs). The efficacy of poly ADP-ribose polymerase inhibitors (PARPis) and temozolomide (TMZ), alone and in combination, was evaluated both in vitro and in vivo. Combination treatment with PARPi and TMZ results in marked in vitro cytotoxicity in Fh1- and Sdhb-deficient cells. In vivo, treatment with standard dosing of the PARP inhibitor BGB-290 and low-dose TMZ significantly inhibits tumor growth without a significant increase in toxicity. These findings provide the basis for a novel therapeutic strategy exploiting HR deficiency in FH and SDH-deficient RCC with combined PARP inhibition and low-dose alkylating chemotherapy.
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Carcinoma de Células Renales , Dioxigenasas , Neoplasias Renales , Adenosina Difosfato Ribosa , Animales , Carcinoma de Células Renales/tratamiento farmacológico , Carcinoma de Células Renales/genética , Ciclo del Ácido Cítrico , ADN , Fumarato Hidratasa/genética , Fumaratos , Humanos , Histona Demetilasas con Dominio de Jumonji , Neoplasias Renales/tratamiento farmacológico , Neoplasias Renales/genética , Lisina , Ratones , Poli(ADP-Ribosa) Polimerasa-1 , Inhibidores de Poli(ADP-Ribosa) Polimerasas/farmacología , Succinato Deshidrogenasa/genética , Succinatos , Temozolomida/farmacologíaRESUMEN
Approximately half of glioblastoma and more than two-thirds of grade II and III glioma tumors lack the DNA repair protein O6-methylguanine methyl transferase (MGMT). MGMT-deficient tumors respond initially to the DNA methylation agent temozolomide (TMZ) but frequently acquire resistance through loss of the mismatch repair (MMR) pathway. We report the development of agents that overcome this resistance mechanism by inducing MMR-independent cell killing selectively in MGMT-silenced tumors. These agents deposit a dynamic DNA lesion that can be reversed by MGMT but slowly evolves into an interstrand cross-link in MGMT-deficient settings, resulting in MMR-independent cell death with low toxicity in vitro and in vivo. This discovery may lead to new treatments for gliomas and may represent a new paradigm for designing chemotherapeutics that exploit specific DNA repair defects.
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Antineoplásicos Alquilantes , Neoplasias Encefálicas , Metilasas de Modificación del ADN , Enzimas Reparadoras del ADN , Diseño de Fármacos , Resistencia a Antineoplásicos , Glioblastoma , Proteínas Supresoras de Tumor , Antineoplásicos Alquilantes/química , Antineoplásicos Alquilantes/farmacología , Antineoplásicos Alquilantes/uso terapéutico , Neoplasias Encefálicas/tratamiento farmacológico , Neoplasias Encefálicas/genética , Línea Celular Tumoral , Metilación de ADN/genética , Metilasas de Modificación del ADN/genética , Reparación del ADN/genética , Enzimas Reparadoras del ADN/genética , Dacarbazina/farmacología , Dacarbazina/uso terapéutico , Resistencia a Antineoplásicos/genética , Glioblastoma/tratamiento farmacológico , Glioblastoma/genética , Humanos , Temozolomida/farmacología , Temozolomida/uso terapéutico , Proteínas Supresoras de Tumor/genéticaRESUMEN
Exatecan and deruxtecan are antineoplastic camptothecin derivatives in development as tumor-targeted-delivery warheads in various formulations including peptides, liposomes, polyethylene glycol nanoparticles, and antibody-drug conjugates. Here, we report the molecular pharmacology of exatecan compared with the clinically approved topoisomerase I (TOP1) inhibitors and preclinical models for validating biomarkers and the combination of exatecan with ataxia telangiectasia and Rad3-related kinase (ATR) inhibitors. Modeling exatecan binding at the interface of a TOP1 cleavage complex suggests two novel molecular interactions with the flanking DNA base and the TOP1 residue N352, in addition to the three known interactions of camptothecins with the TOP1 residues R364, D533, and N722. Accordingly, exatecan showed much stronger TOP1 trapping, higher DNA damage, and apoptotic cell death than the classical TOP1 inhibitors used clinically. We demonstrate the value of SLFN11 expression and homologous recombination (HR) deficiency (HRD) as predictive biomarkers of response to exatecan. We also show that exatecan kills cancer cells synergistically with the clinical ATR inhibitor ceralasertib (AZD6738). To establish the translational potential of this combination, we tested CBX-12, a clinically developed pH-sensitive peptide-exatecan conjugate that selectively targets cancer cells and is currently in clinical trials. The combination of CBX-12 with ceralasertib significantly suppressed tumor growth in mouse xenografts. Collectively, our results demonstrate the potency of exatecan as a TOP1 inhibitor and its clinical potential in combination with ATR inhibitors, using SLFN11 and HRD as predictive biomarkers.
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ADN-Topoisomerasas de Tipo I , Neoplasias , Inhibidores de Topoisomerasa I , Animales , Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Camptotecina/análogos & derivados , ADN/metabolismo , ADN-Topoisomerasas de Tipo I/metabolismo , Humanos , Ratones , Neoplasias/tratamiento farmacológico , Neoplasias/genética , Proteínas Nucleares/metabolismo , Inhibidores de Proteínas Quinasas/farmacología , Inhibidores de Topoisomerasa I/farmacologíaRESUMEN
The methylation status of the O6-methylguanine methyltransferase (MGMT) gene promoter has been widely accepted as a prognostic biomarker for treatment with the alkylator, temozolomide (TMZ). In the absence of promoter methylation, the MGMT enzyme removes O6-methylguanine (O6-meG) lesions. In the setting of MGMT-promoter methylation (MGMT-), the O6-meG lesion activates the mismatch repair (MMR) pathway which functions to remove the damage. Our group reported that loss of MGMT expression via MGMT promoter silencing modulates activation of ataxia telangiectasia and RAD3 related protein (ATR) in response to TMZ treatment, which is associated with synergistic tumor-cell killing. Whether or not MMR proteins are involved in ATR activation in MGMT-cells upon alkylation damage remains poorly understood. To investigate the function of MMR in ATR activation, we created isogenic cell lines with knockdowns of the individual human MMR proteins MutS homolog 2 (MSH2), MutS homolog 6 (MSH6), MutS homolog 3 (MSH3), MutL homolog 1 (MLH1), and PMS1 homolog 2 (PMS2). Here, we demonstrate that MSH2, MSH6, MLH1 and PMS2, specifically, are involved in the activation of the ATR axis after TMZ exposure, whereas MSH3 is likely not. This study elucidates a potential mechanistic understanding of how the MMR system is involved in ATR activation by TMZ in glioblastoma cells, which is important for targeting MMR-mutated cancers.
Asunto(s)
Glioblastoma , Antineoplásicos Alquilantes/farmacología , Antineoplásicos Alquilantes/uso terapéutico , Proteínas de la Ataxia Telangiectasia Mutada/genética , Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Reparación de la Incompatibilidad de ADN/genética , Metilasas de Modificación del ADN/genética , Metilasas de Modificación del ADN/metabolismo , Enzimas Reparadoras del ADN/genética , Enzimas Reparadoras del ADN/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Glioblastoma/tratamiento farmacológico , Glioblastoma/genética , Humanos , Metiltransferasas/metabolismo , Endonucleasa PMS2 de Reparación del Emparejamiento Incorrecto/genética , Homólogo 1 de la Proteína MutL/genética , Homólogo 1 de la Proteína MutL/metabolismo , Proteína 2 Homóloga a MutS/genética , Temozolomida/farmacología , Temozolomida/uso terapéutico , Proteínas Supresoras de Tumor/metabolismoRESUMEN
Treatment options for patients with relapsed/refractory acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) are scarce. Recurring mutations, such as mutations in isocitrate dehydrogenase-1 and -2 (IDH1/2) are found in subsets of AML and MDS, are therapeutically targeted by mutant enzyme-specific small molecule inhibitors (IDHmi). IDH mutations induce diverse metabolic and epigenetic changes that drive malignant transformation. IDHmi alone are not curative and resistance commonly develops, underscoring the importance of alternate therapeutic options. We were first to report that IDH1/2 mutations induce a homologous recombination (HR) defect, which confers sensitivity to poly (ADP)-ribose polymerase inhibitors (PARPi). Here, we show that the PARPi olaparib is effective against primary patient-derived IDH1/2-mutant AML/ MDS xeno-grafts (PDXs). Olaparib efficiently reduced overall engraftment and leukemia-initiating cell frequency as evident in serial transplantation assays in IDH1/2-mutant but not -wildtype AML/MDS PDXs. Importantly, we show that olaparib is effective in both IDHmi-naïve and -resistant AML PDXs, critical given the high relapse and refractoriness rates to IDHmi. Our pre-clinical studies provide a strong rationale for the translation of PARP inhibition to patients with IDH1/2-mutant AML/ MDS, providing an additional line of therapy for patients who do not respond to or relapse after targeted mutant IDH inhibition.
Asunto(s)
Leucemia Mieloide Aguda , Síndromes Mielodisplásicos , Inhibidores Enzimáticos/farmacología , Humanos , Isocitrato Deshidrogenasa/genética , Isocitrato Deshidrogenasa/metabolismo , Leucemia Mieloide Aguda/tratamiento farmacológico , Leucemia Mieloide Aguda/genética , Mutación , Síndromes Mielodisplásicos/tratamiento farmacológico , Síndromes Mielodisplásicos/genética , Inhibidores de Poli(ADP-Ribosa) Polimerasas/farmacología , Inhibidores de Poli(ADP-Ribosa) Polimerasas/uso terapéutico , RecurrenciaRESUMEN
[This corrects the article DOI: 10.1093/narcan/zcab021.].
RESUMEN
Topoisomerase inhibitors are potent DNA damaging agents which are widely used in oncology, and they demonstrate robust synergistic tumor cell killing in combination with DNA repair inhibitors, including poly(ADP)-ribose polymerase (PARP) inhibitors. However, their use has been severely limited by the inability to achieve a favorable therapeutic index due to severe systemic toxicities. Antibody-drug conjugates address this issue via antigen-dependent targeting and delivery of their payloads, but this approach requires specific antigens and yet still suffers from off-target toxicities. There is a high unmet need for a more universal tumor targeting technology to broaden the application of cytotoxic payloads. Acidification of the extracellular milieu arises from metabolic adaptions associated with the Warburg effect in cancer. Here we report the development of a pH-sensitive peptide-drug conjugate to deliver the topoisomerase inhibitor, exatecan, selectively to tumors in an antigen-independent manner. Using this approach, we demonstrate potent in vivo cytotoxicity, complete suppression of tumor growth across multiple human tumor models, and synergistic interactions with a PARP inhibitor. These data highlight the identification of a peptide-topoisomerase inhibitor conjugate for cancer therapy that provides a high therapeutic index, and is applicable to all types of human solid tumors in an antigen-independent manner.
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Alpha Thalassemia/Mental Retardation Syndrome X-Linked (ATRX) is mutated frequently in gliomas and represents a potential target for cancer therapies. ATRX is known to function as a histone chaperone that helps incorporate histone variant, H3.3, into the genome. Studies have implicated ATRX in key DNA damage response (DDR) pathways but a distinct role in DNA repair has yet to be fully elucidated. To further investigate the function of ATRX in the DDR, we created isogenic wild-type (WT) and ATRX knockout (KO) model cell lines using CRISPR-based gene targeting. These studies revealed that loss of ATRX confers sensitivity to poly(ADP)-ribose polymerase (PARP) inhibitors, which was linked to an increase in replication stress, as detected by increased activation of the ataxia telangiectasia and Rad3-related (ATR) signaling axis. ATRX mutations frequently co-occur with mutations in isocitrate dehydrogenase-1 and -2 (IDH1/2), and the latter mutations also induce HR defects and PARP inhibitor sensitivity. We found that the magnitude of PARP inhibitor sensitivity was equal in the context of each mutation alone, although no further sensitization was observed in combination, suggesting an epistatic interaction. Finally, we observed enhanced synergistic tumor cell killing in ATRX KO cells with ATR and PARP inhibition, which is commonly seen in HR-defective cells. Taken together, these data reveal that ATRX may be used as a molecular marker for DDR defects and PARP inhibitor sensitivity, independent of IDH1/2 mutations. These data highlight the important role of common glioma-associated mutations in the regulation of DDR, and novel avenues for molecularly guided therapeutic intervention.
RESUMEN
Mutations in the isocitrate dehydrogenase-1 and -2 (IDH1/2) genes were first identified in glioma and acute myeloid leukemia (AML), and subsequently found in multiple other tumor types. These neomorphic mutations convert the normal product of enzyme, α-ketoglutarate (αKG), to the oncometabolite 2-hydroxyglutarate (2HG). Our group recently demonstrated that 2HG suppresses the high-fidelity homologous recombination (HR) DNA repair pathway, resulting in a state referred to as 'BRCAness', which confers exquisite sensitivity to poly(ADP-ribose) polymerase (PARP) inhibitors. In this study, we sought to elucidate sensitivity of IDH1/2-mutant cells to DNA damage response (DDR) inhibitors and, whether combination therapies could enhance described synthetic lethal interactions. Here, we report that ATR (ataxia telangiectasia and Rad3-related protein kinase) inhibitors are active against IDH1/2-mutant cells, and that this activity is further potentiated in combination with PARP inhibitors. We demonstrate this interaction across multiple cell line models with engineered and endogenous IDH1/2 mutations, with robust anti-tumor activity in vitro and in vivo. Mechanistically, we found ATR and PARP inhibitor treatment induces premature mitotic entry, which is significantly elevated in the setting of IDH1/2-mutations. These data highlight the potential efficacy of targeting HR defects in IDH1/2-mutant cancers and support the development of this combination in future clinical trials.
RESUMEN
Glioblastoma (GBM) is the most common primary malignant tumor of the central nervous system with a dismal prognosis. Locoregional failure is common despite high doses of radiation therapy, which has prompted great interest in developing novel strategies to radiosensitize these cancers. Our group previously identified a calcium channel blocker (CCB), mibefradil, as a potential GBM radiosensitizer. We discovered that mibefradil selectively inhibits a key DNA repair pathway, alternative non-homologous end joining. We then initiated a phase I clinical trial that revealed promising initial efficacy of mibefradil, but further development was hampered by dose-limiting toxicities, including CCB-related cardiotoxicity, off-target hERG channel and cytochrome P450 enzymes (CYPs) interactions. Here, we show that mibefradil inhibits DNA repair independent of its CCB activity, and report a series of mibefradil analogues which lack CCB activity and demonstrate reduced hERG and CYP activity while retaining potency as DNA repair inhibitors. We present in vivo pharmacokinetic studies of the top analogues with evidence of brain penetration. We also report a targeted siRNA-based screen which suggests a possible role for mTOR and Akt in DNA repair inhibition by this class of drugs. Taken together, these data reveal a new class of mibefradil-based DNA repair inhibitors which can be further advanced into pre-clinical testing and eventually clinical trials, as potential GBM radiosensitizers.
RESUMEN
Pediatric high-grade gliomas are among the deadliest of childhood cancers due to limited knowledge of early driving events in their gliomagenesis and the lack of effective therapies available. In this study, we investigate the oncogenic role of PPM1D, a protein phosphatase often found truncated in pediatric gliomas such as DIPG, and uncover a synthetic lethal interaction between PPM1D mutations and nicotinamide phosphoribosyltransferase (NAMPT) inhibition. Specifically, we show that mutant PPM1D drives hypermethylation of CpG islands throughout the genome and promotes epigenetic silencing of nicotinic acid phosphoribosyltransferase (NAPRT), a key gene involved in NAD biosynthesis. Notably, PPM1D mutant cells are shown to be sensitive to NAMPT inhibitors in vitro and in vivo, within both engineered isogenic astrocytes and primary patient-derived model systems, suggesting the possible application of NAMPT inhibitors for the treatment of pediatric gliomas. Overall, our results reveal a promising approach for the targeting of PPM1D mutant tumors, and define a critical link between oncogenic driver mutations and NAD metabolism, which can be exploited for tumor-specific cell killing.
Asunto(s)
Antineoplásicos/farmacología , Neoplasias del Tronco Encefálico/genética , Glioma Pontino Intrínseco Difuso/genética , Nicotinamida Fosforribosiltransferasa/genética , Proteína Fosfatasa 2C/genética , Animales , Antineoplásicos/uso terapéutico , Neoplasias del Tronco Encefálico/tratamiento farmacológico , Neoplasias del Tronco Encefálico/patología , Línea Celular Tumoral , Niño , Citocinas/antagonistas & inhibidores , Metilación de ADN , Glioma Pontino Intrínseco Difuso/tratamiento farmacológico , Glioma Pontino Intrínseco Difuso/patología , Represión Epigenética , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Ratones , Nicotinamida Fosforribosiltransferasa/antagonistas & inhibidores , Nicotinamida Fosforribosiltransferasa/metabolismo , Puente/citología , Puente/patología , Cultivo Primario de Células , Proteína Fosfatasa 2C/metabolismo , Mutaciones Letales Sintéticas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
O6-methylguanine-DNA methyltransferase (MGMT) is an enzyme that removes alkyl groups at the O6-position of guanine in DNA. MGMT expression is reduced or absent in many tumor types derived from a diverse range of tissues, most notably in glioma. Low MGMT expression confers significant sensitivity to DNA alkylating agents such as temozolomide, providing a natural therapeutic index over normal tissue. In this study, we sought to identify novel approaches that could maximally exploit the therapeutic index between tumor cells and normal tissues based on MGMT expression, as a means to enhance selective tumor cell killing. Temozolomide, unlike other alkylators, activated the ataxia telangiectasia and Rad3-related (ATR)-checkpoint kinase 1 (Chk1) axis in a manner that was highly dependent on MGMT status. Temozolomide induced growth delay, DNA double-strand breaks, and G2-M cell-cycle arrest, which led to ATR-dependent phosphorylation of Chk1; this effect was dependent on reduced MGMT expression. Treatment of MGMT-deficient cells with temozolomide increased sensitivity to ATR inhibitors both in vitro and in vivo across numerous tumor cell types. Taken together, this study reveals a novel approach for selectively targeting MGMT-deficient cells with ATR inhibitors and temozolomide. As ATR inhibitors are currently being tested in clinical trials, and temozolomide is a commonly used chemotherapeutic, this approach is clinically actionable. Furthermore, this interaction potently exploits a DNA-repair defect found in many cancers. SIGNIFICANCE: Monofunctional alkylating agents sensitize MGMT-deficient tumor cells to ATR inhibitors.
Asunto(s)
Antineoplásicos Alquilantes/farmacología , Proteínas de la Ataxia Telangiectasia Mutada/antagonistas & inhibidores , Metilasas de Modificación del ADN/metabolismo , Enzimas Reparadoras del ADN/metabolismo , Isoxazoles/farmacología , Pirazinas/farmacología , Temozolomida/farmacología , Proteínas Supresoras de Tumor/metabolismo , Animales , Antineoplásicos Alquilantes/administración & dosificación , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Puntos de Control del Ciclo Celular/efectos de los fármacos , Línea Celular Tumoral , Quinasa 1 Reguladora del Ciclo Celular (Checkpoint 1)/metabolismo , Roturas del ADN de Doble Cadena/efectos de los fármacos , Daño del ADN , Sinergismo Farmacológico , Femenino , Humanos , Isoxazoles/administración & dosificación , Ratones Desnudos , Pirazinas/administración & dosificación , Temozolomida/administración & dosificación , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The hereditary cancer syndromes hereditary leiomyomatosis and renal cell cancer (HLRCC) and succinate dehydrogenase-related hereditary paraganglioma and pheochromocytoma (SDH PGL/PCC) are linked to germline loss-of-function mutations in genes encoding the Krebs cycle enzymes fumarate hydratase and succinate dehydrogenase, thus leading to elevated levels of fumarate and succinate, respectively1-3. Here, we report that fumarate and succinate both suppress the homologous recombination (HR) DNA-repair pathway required for the resolution of DNA double-strand breaks (DSBs) and for the maintenance of genomic integrity, thus rendering tumor cells vulnerable to synthetic-lethal targeting with poly(ADP)-ribose polymerase (PARP) inhibitors. These results identify HLRCC and SDH PGL/PCC as familial DNA-repair deficiency syndromes, providing a mechanistic basis to explain their cancer predisposition and suggesting a potentially therapeutic approach for advanced HLRCC and SDH PGL/PCC, both of which are incurable when metastatic.
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Ciclo del Ácido Cítrico/genética , Síndromes Neoplásicos Hereditarios/genética , Reparación del ADN por Recombinación , Neoplasias de las Glándulas Suprarrenales/genética , Línea Celular , Línea Celular Tumoral , Ciclo del Ácido Cítrico/efectos de los fármacos , Roturas del ADN de Doble Cadena , Fumaratos/farmacología , Mutación de Línea Germinal , Células HEK293 , Humanos , Leiomiomatosis/genética , Feocromocitoma/genética , Neoplasias Cutáneas/genética , Ácido Succínico/farmacología , Neoplasias Uterinas/genéticaRESUMEN
Intracranial delivery of therapeutic agents is limited by penetration beyond the blood-brain barrier (BBB) and rapid metabolism of the drugs that are delivered. Convection-enhanced delivery (CED) of drug-loaded nanoparticles (NPs) provides for local administration, control of distribution, and sustained drug release. While some investigators have shown that repeated CED procedures are possible, longer periods of sustained release could eliminate the need for repeated infusions, which would enhance safety and translatability of the approach. Here, we demonstrate that nanoparticles formed from poly(ethylene glycol)-poly(ω-pentadecalactone-co-p-dioxanone) block copolymers [PEG-poly(PDL-co-DO)] are highly efficient nanocarriers that provide long-term release: small nanoparticles (less than 100â¯nm in diameter) continuously released a radiosensitizer (VE822) over a period of several weeks in vitro, provided widespread intracranial drug distribution during CED, and yielded significant drug retention within the brain for over 1 week. One advantage of PEG-poly(PDL-co-DO) nanoparticles is that hydrophobicity can be tuned by adjusting the ratio of hydrophobic PDL to hydrophilic DO monomers, thus making it possible to achieve a wide range of drug release rates and drug distribution profiles. When administered by CED to rats with intracranial RG2 tumors, and combined with a 5-day course of fractionated radiation therapy, VE822-loaded PEG-poly(PDL-co-DO) NPs significantly prolonged survival when compared to free VE822. Thus, PEG-poly(PDL-co-DO) NPs represent a new type of versatile nanocarrier system with potential for sustained intracranial delivery of therapeutic agents to treat brain tumors.
Asunto(s)
Materiales Biocompatibles/química , Neoplasias Encefálicas/tratamiento farmacológico , Sistemas de Liberación de Medicamentos , Nanopartículas/química , Poliésteres/química , Polietilenglicoles/química , Animales , Neoplasias Encefálicas/patología , Convección , Liberación de Fármacos , Hidrodinámica , Isoxazoles/farmacología , Masculino , Nanopartículas/ultraestructura , Poliésteres/síntesis química , Polietilenglicoles/síntesis química , Pirazinas/farmacología , Fármacos Sensibilizantes a Radiaciones/farmacología , Ratas Endogámicas F344 , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
DNA double-strand break (DSB) repair by homologous recombination (HR) is initiated by CtIP/MRN-mediated DNA end resection to maintain genome integrity. SAMHD1 is a dNTP triphosphohydrolase, which restricts HIV-1 infection, and mutations are associated with Aicardi-Goutières syndrome and cancer. We show that SAMHD1 has a dNTPase-independent function in promoting DNA end resection to facilitate DSB repair by HR. SAMHD1 deficiency or Vpx-mediated degradation causes hypersensitivity to DSB-inducing agents, and SAMHD1 is recruited to DSBs. SAMHD1 complexes with CtIP via a conserved C-terminal domain and recruits CtIP to DSBs to facilitate end resection and HR. Significantly, a cancer-associated mutant with impaired CtIP interaction, but not dNTPase-inactive SAMHD1, fails to rescue the end resection impairment of SAMHD1 depletion. Our findings define a dNTPase-independent function for SAMHD1 in HR-mediated DSB repair by facilitating CtIP accrual to promote DNA end resection, providing insight into how SAMHD1 promotes genome integrity.
Asunto(s)
Reparación del ADN por Unión de Extremidades , Recombinación Homóloga , Proteína 1 que Contiene Dominios SAM y HD/genética , Roturas del ADN de Doble Cadena , Células HCT116 , Células HEK293 , Células HeLa , Humanos , Células MCF-7 , Proteína 1 que Contiene Dominios SAM y HD/deficiencia , Proteína 1 que Contiene Dominios SAM y HD/metabolismo , TransfecciónRESUMEN
High-grade gliomas, such as glioblastoma (GBM) and diffuse intrinsic pontine glioma (DIPG), are characterized by an aggressive phenotype with nearly universal local disease progression despite multimodal treatment, which typically includes chemotherapy, radiotherapy, and possibly surgery. Radiosensitizers that have improved the effects of radiotherapy for extracranial tumors have been ineffective for the treatment of GBM and DIPG, in part due to poor blood-brain barrier penetration and rapid intracranial clearance of small molecules. Here, we demonstrate that nanoparticles can provide sustained drug release and minimal toxicity. When administered locally, these nanoparticles conferred radiosensitization in vitro and improved survival in rats with intracranial gliomas when delivered concurrently with a 5-day course of fractionated radiotherapy. Compared with previous work using locally delivered radiosensitizers and cranial radiation, our approach, based on the rational selection of agents and a clinically relevant radiation dosing schedule, produces the strongest synergistic effects between chemo- and radiotherapy approaches to the treatment of high-grade gliomas. Mol Cancer Ther; 16(8); 1456-69. ©2017 AACR.
Asunto(s)
Neoplasias del Tronco Encefálico/tratamiento farmacológico , Reparación del ADN , Glioma/tratamiento farmacológico , Fármacos Sensibilizantes a Radiaciones/uso terapéutico , Animales , Neoplasias del Tronco Encefálico/patología , Línea Celular Tumoral , Convección , ADN/metabolismo , Reparación del ADN/efectos de los fármacos , Sistemas de Liberación de Medicamentos , Endocitosis/efectos de los fármacos , Glioma/patología , Humanos , Masculino , Nanopartículas/química , Nanopartículas/ultraestructura , Poliésteres/química , Polietilenglicoles/química , Fármacos Sensibilizantes a Radiaciones/farmacología , Ratas Endogámicas F344 , Distribución Tisular/efectos de los fármacosRESUMEN
2-Hydroxyglutarate (2HG) exists as two enantiomers, (R)-2HG and (S)-2HG, and both are implicated in tumor progression via their inhibitory effects on α-ketoglutarate (αKG)-dependent dioxygenases. The former is an oncometabolite that is induced by the neomorphic activity conferred by isocitrate dehydrogenase 1 (IDH1) and IDH2 mutations, whereas the latter is produced under pathologic processes such as hypoxia. We report that IDH1/2 mutations induce a homologous recombination (HR) defect that renders tumor cells exquisitely sensitive to poly(adenosine 5'-diphosphate-ribose) polymerase (PARP) inhibitors. This "BRCAness" phenotype of IDH mutant cells can be completely reversed by treatment with small-molecule inhibitors of the mutant IDH1 enzyme, and conversely, it can be entirely recapitulated by treatment with either of the 2HG enantiomers in cells with intact IDH1/2 proteins. We demonstrate mutant IDH1-dependent PARP inhibitor sensitivity in a range of clinically relevant models, including primary patient-derived glioma cells in culture and genetically matched tumor xenografts in vivo. These findings provide the basis for a possible therapeutic strategy exploiting the biological consequences of mutant IDH, rather than attempting to block 2HG production, by targeting the 2HG-dependent HR deficiency with PARP inhibition. Furthermore, our results uncover an unexpected link between oncometabolites, altered DNA repair, and genetic instability.