RESUMO
E2F1 is the main pro-apoptotic effector of the pRB-regulated tumor suppressor pathway by promoting the transcription of various pro-apoptotic proteins. We report here that E2F1 partly localizes to mitochondria, where it favors mitochondrial outer membrane permeabilization. E2F1 interacts with BCL-xL independently from its BH3 binding interface and induces a stabilization of BCL-xL at mitochondrial membranes. This prevents efficient control of BCL-xL over its binding partners, in particular over BAK resulting in the induction of cell death. We thus identify a new, non-BH3-binding regulator of BCL-xL localization dynamics that influences its anti-apoptotic activity.
Assuntos
Morte Celular , Fator de Transcrição E2F1/metabolismo , Proteína bcl-X/metabolismo , Apoptose , Linhagem Celular Tumoral , Fator de Transcrição E2F1/química , Espaço Extracelular/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Mitocôndrias/metabolismo , Ligação Proteica , Transporte Proteico , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Transcrição Gênica , Proteína Killer-Antagonista Homóloga a bcl-2/metabolismo , Proteína bcl-X/químicaRESUMO
The seeds of Carapa procera are exploited extensively in West African ethnopharmacy for the treatment of several pathologies, including inflammation. They also are effective as insect antifeedants and as a mosquito repellent. With the aim of identifying bioactive principles, an ethyl acetate extract of the defatted seeds was made and fractionated. Two principle compounds were isolated. One of these, 5,6-dehydro-7-deacetoxy-7-oxogedunin (1), while known from another genus of the Meliaceae, is newly identified from the genus Carapa and its X-ray structure is described for the first time. In addition, 1 displayed strong anti-clonogenic activity at 10 µM. The other compound, mexicanolide (2), is known from this species and showed neither cytotoxicity nor anti-clonogenicity. These differences in efficacy are discussed in relation to known structure-activity relationships of limonoids.
Assuntos
Antineoplásicos Fitogênicos/isolamento & purificação , Limoninas/isolamento & purificação , Meliaceae/química , Extratos Vegetais/isolamento & purificação , Triterpenos/isolamento & purificação , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/farmacologia , Neoplasias da Mama , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Feminino , Humanos , Limoninas/química , Limoninas/farmacologia , Estrutura Molecular , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Sementes/química , Triterpenos/química , Triterpenos/farmacologiaRESUMO
PRMT5 is a widely expressed arginine methyltransferase that regulates processes involved in tumor cell proliferation and survival. In the study described here, we investigated whether PRMT5 provides a target for tumor radiosensitization. Knockdown of PRMT5 using siRNA enhanced the radiosensitivity of a panel of cell lines corresponding to tumor types typically treated with radiotherapy. To extend these studies to an experimental therapeutic setting, the PRMT5 inhibitor LLY-283 was used. Exposure of the tumor cell lines to LLY-283 decreased PRMT5 activity and enhanced their radiosensitivity. This increase in radiosensitivity was accompanied by an inhibition of DNA double-strand break repair as determined by γH2AX foci and neutral comet analyses. For a normal fibroblast cell line, although LLY-283 reduced PRMT5 activity, it had no effect on their radiosensitivity. Transcriptome analysis of U251 cells showed that LLY-283 treatment reduced the expression of genes and altered the mRNA splicing pattern of genes involved in the DNA damage response. Subcutaneous xenografts were then used to evaluate the in vivo response to LLY-283 and radiation. Treatment of mice with LLY-283 decreased tumor PRMT5 activity and significantly enhanced the radiation-induced growth delay. These results suggest that PRMT5 is a tumor selective target for radiosensitization.
Assuntos
Proteína-Arginina N-Metiltransferases , Tolerância a Radiação , Proteína-Arginina N-Metiltransferases/metabolismo , Proteína-Arginina N-Metiltransferases/genética , Proteína-Arginina N-Metiltransferases/antagonistas & inibidores , Animais , Humanos , Tolerância a Radiação/efeitos dos fármacos , Tolerância a Radiação/genética , Linhagem Celular Tumoral , Camundongos , Reparo do DNA , Proliferação de Células/efeitos da radiação , Ensaios Antitumorais Modelo de Xenoenxerto , Quebras de DNA de Cadeia Dupla/efeitos da radiação , Camundongos NusRESUMO
We recently identified a previously unappreciated ability of antimitotics to propagate apoptotic priming across cancer cell populations. The underlying paracrine cytotoxic signal, fueled by undead cells activating the cGAS/STING pathway, is required for in vivo antitumor response and it can be further exploited by delayed, but not synchronous, BCL-xL inhibition.
RESUMO
The imbalance between BCL-2 homologues and pro-death counterparts frequently noted in cancer cells endows them with a cell autonomous survival advantage. To eradicate ectopic cells, inhibitors of these homologues (BH3 mimetics) were developed to trigger, during anticancer treatment, full activation of the canonical mitochondrial apoptotic pathway and related caspases. Despite efficiency in some clinical settings, these compounds do not completely fulfill their initial promise. We herein put forth that a growing body of evidence indicates that mitochondrial integrity, controlled by BCL-2 family proteins, and downstream caspases regulate other cell death modes and influence extracellular signaling by committed cells. Moreover, intercellular communications play a key role in spreading therapeutic response across cancer cell populations and in engaging an immune response. We thus advocate that BH3 mimetics administration would be more efficient in the long term if it did not induce apoptosis in all sensitive cells at the same time, but if it could instead allow (or trigger) death signal production by non-terminally committed dying cell populations. The development of such a trade-off strategy requires to unravel the effects of BH3 mimetics not only on each individual cancer cell but also on homotypic and heterotypic cell interactions in dynamic tumor ecosystems.
Assuntos
Antineoplásicos/farmacologia , Neoplasias/tratamento farmacológico , Proteínas Proto-Oncogênicas c-bcl-2/antagonistas & inibidores , Animais , Antineoplásicos/química , Antineoplásicos/uso terapêutico , Apoptose/efeitos dos fármacos , Descoberta de Drogas , Humanos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Terapia de Alvo Molecular , Neoplasias/metabolismo , Neoplasias/patologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismoRESUMO
A fascinating but uncharacterized action of antimitotic chemotherapy is to collectively prime cancer cells to apoptotic mitochondrial outer membrane permeabilization (MOMP), while impacting only on cycling cell subsets. Here, we show that a proapoptotic secretory phenotype is induced by activation of cGAS/STING in cancer cells that are hit by antimitotic treatment, accumulate micronuclei and maintain mitochondrial integrity despite intrinsic apoptotic pressure. Organotypic cultures of primary human breast tumors and patient-derived xenografts sensitive to paclitaxel exhibit gene expression signatures typical of type I IFN and TNFα exposure. These cytokines induced by cGAS/STING activation trigger NOXA expression in neighboring cells and render them acutely sensitive to BCL-xL inhibition. cGAS/STING-dependent apoptotic effects are required for paclitaxel response in vivo, and they are amplified by sequential, but not synchronous, administration of BH3 mimetics. Thus anti-mitotic agents propagate apoptotic priming across heterogeneously sensitive cancer cells through cytosolic DNA sensing pathway-dependent extracellular signals, exploitable by delayed MOMP targeting.