RESUMO
The oncogenic transcription factor signal transducer and activator of transcription 3 (STAT3) is frequently activated inappropriately in a wide range of hematological and solid cancers, but clinically available therapies targeting STAT3 are lacking. Using a computational strategy to identify compounds opposing the gene expression signature of STAT3, we discovered atovaquone (Mepron), an antimicrobial approved by the US Food and Drug Administration, to be a potent STAT3 inhibitor. We show that, at drug concentrations routinely achieved clinically in human plasma, atovaquone inhibits STAT3 phosphorylation, the expression of STAT3 target genes, and the viability of STAT3-dependent hematological cancer cells. These effects were also observed with atovaquone treatment of primary blasts isolated from patients with acute myelogenous leukemia or acute lymphocytic leukemia. Atovaquone is not a kinase inhibitor but instead rapidly and specifically downregulates cell-surface expression of glycoprotein 130, which is required for STAT3 activation in multiple contexts. The administration of oral atovaquone to mice inhibited tumor growth and prolonged survival in a murine model of multiple myeloma. Finally, in patients with acute myelogenous leukemia treated with hematopoietic stem cell transplantation, extended use of atovaquone for Pneumocystis prophylaxis was associated with improved relapse-free survival. These findings establish atovaquone as a novel, clinically accessible STAT3 inhibitor with evidence of anticancer efficacy in both animal models and humans.
Assuntos
Antineoplásicos/farmacologia , Atovaquona/farmacologia , Descoberta de Drogas , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Fator de Transcrição STAT3/antagonistas & inibidores , Animais , Antineoplásicos/uso terapêutico , Apoptose/efeitos dos fármacos , Apoptose/genética , Atovaquona/química , Atovaquona/uso terapêutico , Linhagem Celular Tumoral , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Receptor gp130 de Citocina/metabolismo , Modelos Animais de Doenças , Regulação para Baixo/efeitos dos fármacos , Humanos , Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patologia , Camundongos , Fosforilação/efeitos dos fármacos , Fosfotirosina/metabolismo , Fator de Transcrição STAT3/metabolismo , Resultado do TratamentoAssuntos
Antineoplásicos/uso terapêutico , Leucemia Linfocítica Crônica de Células B/tratamento farmacológico , Proteínas de Neoplasias/antagonistas & inibidores , Pirimetamina/uso terapêutico , Fator de Transcrição STAT3/antagonistas & inibidores , Adulto , Idoso , Idoso de 80 Anos ou mais , Antineoplásicos/administração & dosagem , Linfócitos B/efeitos dos fármacos , Linfócitos B/metabolismo , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Reposicionamento de Medicamentos , Ensaios de Seleção de Medicamentos Antitumorais , Feminino , Perfilação da Expressão Gênica , Regulação Leucêmica da Expressão Gênica/efeitos dos fármacos , Humanos , Masculino , Pessoa de Meia-Idade , Proteínas de Neoplasias/biossíntese , Proteínas de Neoplasias/genética , Intervalo Livre de Progressão , Pirimetamina/administração & dosagem , Pirimetamina/farmacologiaRESUMO
BACKGROUND: The circulating tumor cell (CTC) field is rapidly advancing with the advent of continuously improving technologies for enriching these rare neoplastic cells from blood. CTC enumeration provides prognostic information, and CTC characterization has the potential to provide more useful information for the clinical decision-making process in this era of personalized medicine and targeted therapeutics. Proof-of-principle studies have shown that CTC samples can be characterized with a variety of techniques in the research laboratory environment. The goal of the current study was to validate routine cytologic techniques and immunohistochemical markers in CTC samples in a clinical cytology laboratory, using inducible phosphorylated signal transducer and activator of transcription 3 (pSTAT3) as a clinically important example and Ki-67 as a positive control. METHODS: Whole blood from noncancer patients was spiked with breast cancer cell lines with constitutive or inducible pSTAT3 expression and underwent CTC processing in the CellSearch system. The resulting CTC samples were subjected to various cytologic/immunocytochemical techniques and were compared with non-CTC-processed cultured cell controls. RESULTS: CTC-processed samples showed a morphology comparable to that of controls in cytospin, ThinPrep, and cell block preparations. Immunocytochemistry for Ki-67 and pSTAT3 provided biological information from CTC samples, showing uniform Ki-67 staining across all samples, pSTAT3 positivity in the constitutive and induced cells, and an absence of pSTAT3 expression in the noninduced cells, as expected. CONCLUSIONS: CTC samples can be processed in the cytology laboratory with routine methods. CTC morphologic and immunophenotypic analysis can be easily integrated into the existing clinical workflow, moving the field closer to a true peripheral blood liquid biopsy for cancer patients.
Assuntos
Biomarcadores Tumorais/análise , Citodiagnóstico/métodos , Técnicas Citológicas/métodos , Células Neoplásicas Circulantes , Fator de Transcrição STAT3/análise , Humanos , Imuno-HistoquímicaRESUMO
Interleukin-6 (IL-6)-mediated activation of signal transducer and activator of transcription 3 (STAT3) is a mechanism by which chronic inflammation can contribute to cancer and is a common oncogenic event. We discovered a pathway, the loss of which is associated with persistent STAT3 activation in human cancer. We found that the gene encoding the tumor suppressor microRNA miR-146b is a direct STAT3 target gene, and its expression was increased in normal breast epithelial cells but decreased in tumor cells. Methylation of the miR-146b promoter, which inhibited STAT3-mediated induction of expression, was increased in primary breast cancers. Moreover, we found that miR-146b inhibited nuclear factor κB (NF-κB)-dependent production of IL-6, subsequent STAT3 activation, and IL-6/STAT3-driven migration and invasion in breast cancer cells, thereby establishing a negative feedback loop. In addition, higher expression of miR-146b was positively correlated with patient survival in breast cancer subtypes with increased IL6 expression and STAT3 phosphorylation. Our results identify an epigenetic mechanism of crosstalk between STAT3 and NF-κB relevant to constitutive STAT3 activation in malignancy and the role of inflammation in oncogenesis.