RESUMO
Death receptor agonist therapies have exhibited limited clinical benefit to date. Investigations into why Apo2L/TRAIL and AMG 655 preclinical data were not predictive of clinical response revealed that coadministration of Apo2L/TRAIL with AMG 655 leads to increased antitumor activity in vitro and in vivo. The combination of Apo2L/TRAIL and AMG 655 results in enhanced signaling and can sensitize Apo2L/TRAIL-resistant cells. Structure determination of the Apo2L/TRAIL-DR5-AMG 655 ternary complex illustrates how higher order clustering of DR5 is achieved when both agents are combined. Enhanced agonism generated by combining Apo2L/TRAIL and AMG 655 provides insight into the limited efficacy observed in previous clinical trials and suggests testable hypotheses to reconsider death receptor agonism as a therapeutic strategy.
Assuntos
Anticorpos Monoclonais/farmacologia , Antineoplásicos/farmacologia , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/metabolismo , Ligante Indutor de Apoptose Relacionado a TNF/farmacologia , Animais , Anticorpos Monoclonais/química , Antineoplásicos/química , Linhagem Celular Tumoral , Sobrevivência Celular , Cristalografia por Raios X , Resistencia a Medicamentos Antineoplásicos , Sinergismo Farmacológico , Humanos , Camundongos , Modelos Moleculares , Multimerização Proteica , Estrutura Quaternária de Proteína , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/antagonistas & inibidores , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/química , Transdução de Sinais , Ligante Indutor de Apoptose Relacionado a TNF/química , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
In bone metastases, tumor cells interact with the bone microenvironment to induce osteoclastogenesis, leading to bone destruction and the growth factor release. RANK ligand (RANKL) is essential for osteoclast formation, function, and survival. Tumor cell-mediated osteolysis is thought to occur ultimately via induction of RANKL within the bone stroma, and inhibition of RANKL in models of breast cancer bone metastases blocks tumor-induced osteolysis and reduces skeletal tumor burden. In addition, the skeleton is co-opted by tumor cells and functions as a supportive tumor microenvironment. Inhibition of RANKL, by reducing tumor-induced osteoclastogenesis, may reduce the local release of growth factors and calcium which may potentially enhance the anti-tumor activity of cytotoxic or direct tumor apoptotic agents. Recombinant human Apo2 ligand/ TNF-related apoptosis-inducing ligand (rhApo2L/TRAIL/dulanermin) is a dual pro-apoptotic receptor agonist that preferentially induces apoptosis in cancer cells versus normal cells. We therefore examined RANKL inhibition (using RANK-Fc) in combination with rhApo2L/TRAIL on tumor-induced osteolysis and skeletal tumor burden in a murine intracardiac injection model of MDA-MB-231 breast carcinoma bone metastasis. rhApo2L/TRAIL treatment resulted in a rapid reduction of skeletal tumor burden. Treatment with RANK-Fc prevented osteolytic lesions and reduced skeletal tumor burden. Combining RANK-Fc with rhApo2L/TRAIL was superior to either rhApo2L/TRAIL or RANK-Fc alone at reducing skeletal tumor burden in the bone metastasis model. Our findings show that RANKL inhibition effectively inhibits pathologic osteolysis induced by human breast adenocarcinoma MDA-MB-231 cells in animals with established tumors, and also enhances the ability of rhApo2L/TRAIL to reduce skeletal tumor burden in vivo.
Assuntos
Adenocarcinoma/terapia , Neoplasias Ósseas/terapia , Neoplasias da Mama/terapia , Terapia Genética , Ligante RANK/antagonistas & inibidores , Proteínas Recombinantes de Fusão/uso terapêutico , Proteínas Recombinantes/genética , Ligante Indutor de Apoptose Relacionado a TNF/genética , Adenocarcinoma/genética , Adenocarcinoma/secundário , Animais , Apoptose , Western Blotting , Neoplasias Ósseas/genética , Neoplasias Ósseas/secundário , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Proliferação de Células , Modelos Animais de Doenças , Quimioterapia Combinada , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Camundongos , Camundongos SCID , Osteólise , Carga TumoralRESUMO
Cancer presents a difficult challenge for oncologists, as there are few therapies that specifically target disease cells. Existing treatment strategies rely heavily on physical and chemical agents that nonspecifically affect DNA metabolism. To improve the effectiveness of these treatments, we have identified a new class of protein kinase inhibitor that targets a major DNA repair pathway. A representative of this class, 1-(2-hydroxy-4-morpholin-4-yl-phenyl)-ethanone, inhibits the DNA-dependent protein kinase (DNA-PK) and differs significantly from previously studied DNA-PK inhibitors both structurally and functionally. DNA-PK participates in the cellular response to and repair of chromosomal DNA double-strand breaks (DSBs). These new selective inhibitors recapitulate the phenotype of DNA-PK defective cell lines including those from SCID mice. These compounds directly inhibit the repair of DNA DSBs and consequently enhance the cytotoxicity of physical and chemical agents that induce DSBs but not other DNA lesions. In contrast to previously studied DNA-PK inhibitors, these compounds appear benign, exhibiting no toxic effects in the absence of DSB-inducing treatments. Most importantly, 1-(2-hydroxy-4-morpholin-4-yl-phenyl)-ethanone synergistically enhances radiation-induced tumor control in a mouse-human xenograft assay. These studies validate DNA-PK as a cancer drug target and suggest a new approach for enhancing the effects of existing cancer therapies.
