RESUMO
Tumor cells gain a survival/growth advantage by adapting their metabolism to respond to environmental stress, a process known as metabolic transformation. The best-known aspect of metabolic transformation is the Warburg effect, whereby cancer cells up-regulate glycolysis under aerobic conditions. However, other mechanisms mediating metabolic transformation remain undefined. Here we report that carnitine palmitoyltransferase 1C (CPT1C), a brain-specific metabolic enzyme, may participate in metabolic transformation. CPT1C expression correlates inversely with mammalian target of rapamycin (mTOR) pathway activation, contributes to rapamycin resistance in murine primary tumors, and is frequently up-regulated in human lung tumors. Tumor cells constitutively expressing CPT1C show increased fatty acid (FA) oxidation, ATP production, and resistance to glucose deprivation or hypoxia. Conversely, cancer cells lacking CPT1C produce less ATP and are more sensitive to metabolic stress. CPT1C depletion via siRNA suppresses xenograft tumor growth and metformin responsiveness in vivo. CPT1C can be induced by hypoxia or glucose deprivation and is regulated by AMPKα. Cpt1c-deficient murine embryonic stem (ES) cells show sensitivity to hypoxia and glucose deprivation and altered FA homeostasis. Our results indicate that cells can use a novel mechanism involving CPT1C and FA metabolism to protect against metabolic stress. CPT1C may thus be a new therapeutic target for the treatment of hypoxic tumors.
Assuntos
Carnitina O-Palmitoiltransferase/metabolismo , Estresse Fisiológico/fisiologia , Proteínas Quinases Ativadas por AMP/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Apoptose/fisiologia , Carnitina O-Palmitoiltransferase/deficiência , Carnitina O-Palmitoiltransferase/genética , Linhagem Celular Tumoral , Proliferação de Células , Sobrevivência Celular/genética , Células Cultivadas , Resistencia a Medicamentos Antineoplásicos/genética , Células-Tronco Embrionárias/enzimologia , Regulação Neoplásica da Expressão Gênica , Células HCT116 , Humanos , Hipóxia/patologia , Neoplasias Pulmonares/enzimologia , Neoplasias Pulmonares/patologia , Camundongos , RNA Mensageiro/metabolismo , Reprodutibilidade dos Testes , Estresse Fisiológico/genética , Serina-Treonina Quinases TOR/metabolismo , Transplante Heterólogo , Regulação para CimaRESUMO
The vascular endothelial growth factor (VEGF) signaling pathway appears to be the dominant pathway involved in tumor angiogenesis, providing a rationale for targeting the VEGF receptors (VEGFR-1, -2, and -3) in the treatment of cancers. In particular, VEGF signaling is thought to be important in renal cell carcinoma (RCC) because of the deregulation of the pathway through nearly uniform loss of the von Hippel Lindau protein. The tyrosine kinase inhibitors (TKIs) sorafenib, sunitinib, and pazopanib are approved by the US Food and Drug Administration for the treatment of advanced RCC; however, these multitargeted agents inhibit a wide range of kinase targets in addition to the VEGFRs, resulting in a range of adverse effects unrelated to efficient VEGF blockade. This article reviews recent advances in the development of the second-generation VEGFR TKIs, including the more selective VEGFR TKIs tivozanib and axitinib, and focuses on the potential benefits of novel inhibitors with improved potency and selectivity.
Assuntos
Inibidores de Proteínas Quinases/farmacologia , Inibidores de Proteínas Quinases/uso terapêutico , Receptores de Fatores de Crescimento do Endotélio Vascular/antagonistas & inibidores , Antineoplásicos/efeitos adversos , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Carcinoma de Células Renais/tratamento farmacológico , Carcinoma de Células Renais/enzimologia , Humanos , Neoplasias Renais/tratamento farmacológico , Neoplasias Renais/enzimologia , Inibidores de Proteínas Quinases/efeitos adversos , Receptores de Fatores de Crescimento do Endotélio Vascular/metabolismoRESUMO
To recapitulate the stochastic nature of human cancer development, we have devised a strategy for generating mouse tumor models that involves stepwise genetic manipulation of embryonic stem (ES) cells and chimera generation. Tumors in the chimeric animals develop from engineered cells in the context of normal tissue. Adenocarcinomas arising in an allelic series of lung cancer models containing HER2 (also known as ERBB2), KRAS or EGFR oncogenes exhibit features of advanced malignancies. Treatment of EGFR(L858R) and KRAS(G12V) chimeric models with an EGFR inhibitor resulted in near complete tumor regression and no response to the treatment, respectively, accurately reflecting previous clinical observations. Transcriptome and immunohistochemical analyses reveal that PI3K pathway activation is unique to ERBB family tumors whereas KRAS-driven tumors show activation of the JNK/SAP pathway, suggesting points of therapeutic intervention for this difficult-to-treat tumor category.
Assuntos
Adenocarcinoma/metabolismo , Quimera/metabolismo , Receptores ErbB/metabolismo , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patologia , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Transdução de Sinais , Adenocarcinoma/patologia , Animais , Modelos Animais de Doenças , Células-Tronco Embrionárias/efeitos dos fármacos , Células-Tronco Embrionárias/metabolismo , Camundongos , Camundongos Transgênicos , Mutação/genética , Fenótipo , Piperazinas/farmacologia , Quinazolinas/farmacologia , Insuficiência Respiratória/metabolismo , Insuficiência Respiratória/patologia , Transdução de Sinais/efeitos dos fármacosRESUMO
Notch pathway signaling plays a fundamental role in normal biological processes and is frequently deregulated in many cancers. Although several hypotheses regarding cancer subpopulations most likely to respond to therapies targeting the Notch pathway have been proposed, clinical utility of these predictive markers has not been shown. To understand the molecular basis of gamma-secretase inhibitor (GSI) sensitivity in breast cancer, we undertook an unbiased, de novo responder identification study using a novel genetically engineered in vivo breast cancer model. We show that tumors arising from this model are heterogeneous on the levels of gene expression, histopathology, growth rate, expression of Notch pathway markers, and response to GSI treatment. In addition, GSI treatment of this model was associated with inhibition of Hes1 and proliferation markers, indicating that GSI treatment inhibits Notch signaling. We then identified a pretreatment gene expression signature comprising 768 genes that is significantly associated with in vivo GSI efficacy across 99 tumor lines. Pathway analysis showed that the GSI responder signature is enriched for Notch pathway components and inflammation/immune-related genes. These data show the power of this novel in vivo model system for the discovery of biomarkers predictive of response to targeted therapies, and provide a basis for the identification of human breast cancers most likely to be sensitive to GSI treatment.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Óxidos S-Cíclicos/administração & dosagem , Inibidores Enzimáticos/administração & dosagem , Neoplasias Mamárias Experimentais/tratamento farmacológico , Neoplasias Mamárias Experimentais/enzimologia , Tiadiazóis/administração & dosagem , Animais , Processos de Crescimento Celular/efeitos dos fármacos , Esquema de Medicação , Redes Reguladoras de Genes , Humanos , Neoplasias Mamárias Experimentais/genética , Neoplasias Mamárias Experimentais/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos TransgênicosAssuntos
Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Genes Neoplásicos/genética , Glândulas Mamárias Humanas/fisiologia , Animais , Neoplasias da Mama/metabolismo , Modelos Animais de Doenças , Feminino , Fibroblastos/fisiologia , Genes Neoplásicos/fisiologia , Humanos , Glândulas Mamárias Humanas/patologia , Camundongos , Transplante de Neoplasias , Células Estromais/fisiologiaRESUMO
Breast cancer development is a complex pathobiological process involving sequential genetic alterations in normal epithelial cells that results in uncontrolled growth in a permissive microenvironment. Accordingly, physiologically relevant models of human breast cancer that recapitulate these events are needed to study cancer biology and evaluate therapeutic agents. Here, we report the generation and utilization of the human breast cancer in mouse (HIM) model, which is composed of genetically engineered primary human breast epithelial organoids and activated human breast stromal cells. By using this approach, we have defined key genetic events required to drive the development of human preneoplastic lesions as well as invasive adenocarcinomas that are histologically similar to those in patients. Tumor development in the HIM model proceeds through defined histological stages of hyperplasia, DCIS to invasive carcinoma. Moreover, HIM tumors display characteristic responses to targeted therapies, such as HER2 inhibitors, further validating the utility of these models in preclinical compound testing. The HIM model is an experimentally tractable human in vivo system that holds great potential for advancing our basic understanding of cancer biology and for the discovery and testing of targeted therapies.
Assuntos
Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/patologia , Animais , Apoptose/efeitos dos fármacos , Neoplasias da Mama/metabolismo , Transformação Celular Neoplásica/metabolismo , Ciclina D1/metabolismo , Modelos Animais de Doenças , Progressão da Doença , Regulação Neoplásica da Expressão Gênica , Humanos , Camundongos , Invasividade Neoplásica , Fosfatidilinositol 3-Quinases/metabolismo , Interferência de RNA , Receptor ErbB-2/antagonistas & inibidores , Receptor ErbB-2/genética , Receptor ErbB-2/metabolismo , Vírus 40 dos Símios/genética , Vírus 40 dos Símios/metabolismo , Telomerase/metabolismo , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto , Proteínas ras/genética , Proteínas ras/metabolismoRESUMO
Prolonged growth of murine embryonic stem (ES) cells lacking the telomerase reverse transcriptase, mTert, results in a loss of telomere DNA and an increased incidence of end-to-end fusions and aneuploidy. Furthermore, loss of only one copy of mTert also results in telomere shortening intermediate between wild-type (wt) and mTert-null ES cells [Liu, Y., Snow, B. E., Hande, M. P., Yeung, D., Erdmann, N. J., Wakeham, A., Itie, A., Siderovski, D. P., Lansdorp, P. M., Robinson, M. O. & Harrington, L. (2000) Curr. Biol. 10, 1459-1462]. Unexpectedly, although average telomere length in mTert(+/-) ES cells declined to a similar level as mTert-null ES cells, mTert(+/-) ES cell lines retained a minimal telomeric DNA signal at all chromosome ends. Consequently, no end-to-end fusions and genome instability were observed in the latest passages of mTert(+/-) ES cell lines. These data uncover a functional distinction between the dosage-dependent function of telomerase in average telomere-length maintenance and the selective maintenance of critically short telomeres in cells heterozygous for mTert. In normal and tumor cells, we suggest that telomerase activity insufficient to maintain a given average telomere length may, nonetheless, provide a protective advantage from end-to-end fusion and genome instability.
Assuntos
Heterozigoto , Telomerase/genética , Telomerase/metabolismo , Telômero/enzimologia , Telômero/metabolismo , Animais , Células Cultivadas , Aberrações Cromossômicas , Proteínas de Ligação a DNA , Deleção de Genes , Genoma , Hibridização in Situ Fluorescente , Metáfase/genética , Camundongos , Transporte Proteico , Células-Tronco/citologia , Células-Tronco/enzimologia , Células-Tronco/metabolismo , Telômero/genéticaRESUMO
The molecular cloning of telomerase and telomere components has enabled the analysis and precise manipulation of processes that regulate telomere length maintenance. In mammalian cells and in other organisms, we now recognize that disruption of telomere integrity via any one of a number of perturbations induces chromosome instability and the activation of DNA damage responses. Thus, telomere dysfunction may represent a physiological trigger of the DNA damage or apoptotic response in an analogous fashion to other genotoxic insults that introduce chromosome breaks. Initial studies in mice lacking the murine telomerase RNA and in cells expressing a dominant negative version of the telomere binding protein TRF2 revealed a strong p53-dependent response to telomere dysfunction. Yet, telomere dysfunction exhibits p53-independent effects as well, an observation supported by p53-independent responses to telomere dysfunction in p53 mutant human tumor cell lines and mouse cells. As most tumors are compromised for p53 function, examination of this p53-independent response warrants closer attention. A better understanding of this p53-independent response may prove critical for determining the ultimate utility of telomerase inhibitors in the clinic. This review will summarize our current understanding of the molecular responses to telomere dysfunction in mammalian cells.