RESUMO
GNA13 (Gα13) is one of two alpha subunit members of the G12/13 family of heterotrimeric G-proteins which mediate signaling downstream of GPCRs. It is known to be essential for embryonic development and vasculogenesis and has been increasingly shown to be involved in mediating several steps of cancer progression. Recent studies found that Gα13 can function as an oncogene and contributes to progression and metastasis of multiple tumor types, including ovarian, head and neck and prostate cancers. In most cases, Gα12 and Gα13, as closely related α-subunits in the subfamily, have similar cellular roles. However, in recent years their differences in signaling and function have started to emerge. We previously identified that Gα13 drives invasion of Triple Negative Breast Cancer (TNBC) cells in vitro. As a highly heterogenous disease with various well-defined molecular subtypes (ER+ /Her2-, ER+ /Her2+, Her2+, TNBC) and subtype associated outcomes, the function(s) of Gα13 beyond TNBC should be explored. Here, we report the finding that low expression of GNA13 is predictive of poorer survival in breast cancer, which challenges the conventional idea of Gα12/13 being universal oncogenes in solid tumors. Consistently, we found that Gα13 suppresses the proliferation in multiple ER+ breast cancer cell lines (MCF-7, ZR-75-1 and T47D). Loss of GNA13 expression drives cell proliferation, soft-agar colony formation and in vivo tumor formation in an orthotopic xenograft model. To evaluate the mechanism of Gα13 action, we performed RNA-sequencing analysis on these cell lines and found that loss of GNA13 results in the upregulation of MYC signaling pathways in ER+ breast cancer cells. Simultaneous silencing of MYC reversed the proliferative effect from the loss of GNA13, validating the role of MYC in Gα13 regulation of proliferation. Further, we found Gα13 regulates the expression of MYC, at both the transcript and protein level in an ERα dependent manner. Taken together, our study provides the first evidence for a tumor suppressive role for Gα13 in breast cancer cells and demonstrates for the first time the direct involvement of Gα13 in ER-dependent regulation of MYC signaling. With a few exceptions, elevated Gα13 levels are generally considered to be oncogenic, similar to Gα12. This study demonstrates an unexpected tumor suppressive role for Gα13 in ER+ breast cancer via regulation of MYC, suggesting that Gα13 can have subtype-dependent tumor suppressive roles in breast cancer.
Assuntos
Proliferação de Células , Receptor alfa de Estrogênio , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP , Regulação Neoplásica da Expressão Gênica , Proteínas Proto-Oncogênicas c-myc , Humanos , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/metabolismo , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/genética , Feminino , Receptor alfa de Estrogênio/metabolismo , Receptor alfa de Estrogênio/genética , Animais , Linhagem Celular Tumoral , Camundongos , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , Neoplasias de Mama Triplo Negativas/genética , Neoplasias de Mama Triplo Negativas/patologia , Neoplasias de Mama Triplo Negativas/metabolismo , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Neoplasias da Mama/metabolismo , Transdução de Sinais , Regulação para CimaRESUMO
Gα13 and Gα12, encoded by the GNA13 and GNA12 genes, respectively, are members of the G12 family of Gα proteins that, along with their associated Gßγ subunits, mediate signaling from specific G protein-coupled receptors (GPCRs). Advanced prostate cancers have increased expression of GPCRs such as CXC Motif Chemokine Receptor 4 (CXCR4), lysophosphatidic acid receptor (LPAR), and protease activated receptor 1 (PAR-1). These GPCRs signal through either the G12 family, or through Gα13 exclusively, often in addition to other G proteins. The effect of Gα13 can be distinct from that of Gα12, and the role of Gα13 in prostate cancer initiation and progression is largely unexplored. The oncogenic effect of Gα13 on cell migration and invasion in prostate cancer has been characterized, but little is known about other biological processes such as mitochondrial function and oxidative stress. Current knowledge on the link between Gα13 and oxidative stress is based on animal studies in which GPCR-Gα13 signaling decreased superoxide levels, and the overexpression of constitutively active Gα13 promoted antioxidant gene activation. In human samples, mitochondrial superoxide dismutase 2 (SOD2) correlates with prostate cancer risk and prognostic Gleason grade. However, overexpression of SOD2 in prostate cancer cells yielded conflicting results on cell growth and survival under basal versus oxidative stress conditions. Hence, it is necessary to explore the effect of Gα13 on prostate cancer tumorigenesis, as well as the effect of Gα13 on SOD2 in prostate cancer cell growth under oxidative stress conditions.
Assuntos
Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP , Mitocôndrias , Estresse Oxidativo , Neoplasias da Próstata , Humanos , Masculino , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/genética , Neoplasias da Próstata/patologia , Mitocôndrias/metabolismo , Mitocôndrias/genética , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/metabolismo , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/genética , Animais , Transdução de Sinais , Receptores Acoplados a Proteínas G/metabolismo , Receptores Acoplados a Proteínas G/genética , Superóxido Dismutase/metabolismo , Superóxido Dismutase/genéticaRESUMO
Epithelial-to-mesenchymal transition (EMT) is a critical underpinning process for cancer progression, recurrence and resistance to drug treatment. Identification of new regulators of EMT could lead to the development of effective therapies to improve the outcome of advanced cancers. In the current study we discovered, using a variety of in vitro and in vivo approaches, that RAB4A function is essential for EMT and related manifestation of stemness and invasive properties. Consistently, RAB4A suppression abolished the cancer cells' self-renewal and tumor forming ability. In terms of downstream signaling, we found that RAB4A regulation of EMT is achieved through its control of activation of the RAC1 GTPase. Introducing activated RAC1 efficiently rescued EMT gene expression, invasion and tumor formation suppressed by RAB4A knockdown in both the in vitro and in vivo cancer models. In summary, this study identifies a RAB4A-RAC1 signaling axis as a key regulatory mechanism for the process of EMT and cancer progression and suggests a potential therapeutic approach to controlling these processes.
Assuntos
Neoplasias da Mama , Proteínas rac1 de Ligação ao GTP , Humanos , Feminino , Proteínas rac1 de Ligação ao GTP/genética , Proteínas rac1 de Ligação ao GTP/metabolismo , Linhagem Celular Tumoral , Transição Epitelial-Mesenquimal/genética , Transdução de SinaisRESUMO
G12 proteins comprise a subfamily of G-alpha subunits of heterotrimeric GTP-binding proteins (G proteins) that link specific cell surface G protein-coupled receptors (GPCRs) to downstream signaling molecules and play important roles in human physiology. The G12 subfamily contains two family members: Gα12 and Gα13 (encoded by the GNA12 and GNA13 genes, respectively) and, as with all G proteins, their activity is regulated by their ability to bind to guanine nucleotides. Increased expression of both Gα12 and Gα13, and their enhanced signaling, has been associated with tumorigenesis and tumor progression of multiple cancer types over the past decade. Despite these strong associations, Gα12/13 proteins are underappreciated in the field of cancer. As our understanding of G protein involvement in oncogenic signaling has evolved, it has become clear that Gα12/13 signaling is pleotropic and activates specific downstream effectors in different tumor types. Further, the expression of Gα12/13 proteins is regulated through a series of transcriptional and post-transcriptional mechanisms, several of which are frequently deregulated in cancer. With the ever-increasing understanding of tumorigenic processes driven by Gα12/13 proteins, it is becoming clear that targeting Gα12/13 signaling in a context-specific manner could provide a new strategy to improve therapeutic outcomes in a number of solid tumors. In this review, we detail how Gα12/13 proteins, which were first discovered as proto-oncogenes, are now known to drive several "classical" hallmarks, and also play important roles in the "emerging" hallmarks, of cancer.
Assuntos
Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/genética , Neoplasias/genética , Oncogenes/genética , Animais , Humanos , Camundongos , Transdução de SinaisRESUMO
DNA damage is a double-edged sword for cancer cells. On the one hand, DNA damage-induced genomic instability contributes to cancer development; on the other hand, accumulating damage compromises proliferation and survival of cancer cells. Understanding the key regulators of DNA damage repair machinery would benefit the development of cancer therapies that induce DNA damage and apoptosis. In this study, we found that isoprenylcysteine carboxylmethyltransferase (ICMT), a posttranslational modification enzyme, plays an important role in DNA damage repair. We found that ICMT suppression consistently reduces the activity of MAPK signaling, which compromises the expression of key proteins in the DNA damage repair machinery. The ensuing accumulation of DNA damage leads to cell cycle arrest and apoptosis in multiple breast cancer cells. Interestingly, these observations are more pronounced in cells grown under anchorage-independent conditions or grown in vivo. Consistent with the negative impact on DNA repair, ICMT inhibition transforms the cancer cells into a "BRCA-like" state, hence sensitizing cancer cells to the treatment of PARP inhibitor and other DNA damage-inducing agents.
Assuntos
Neoplasias da Mama/metabolismo , Dano ao DNA/genética , Reparo do DNA/genética , Sistema de Sinalização das MAP Quinases/genética , Proteínas Metiltransferases/metabolismo , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Benzamidas/farmacologia , Neoplasias da Mama/patologia , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Pontos de Checagem do Ciclo Celular/genética , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Dano ao DNA/efeitos dos fármacos , Reparo do DNA/efeitos dos fármacos , Feminino , Vetores Genéticos , Células HEK293 , Humanos , Indazóis/farmacologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Camundongos , Camundongos SCID , Piperidinas/farmacologia , Poli(ADP-Ribose) Polimerase-1/antagonistas & inibidores , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Proteínas Metiltransferases/genética , RNA Interferente Pequeno/genética , Ribonucleosídeos/farmacologia , Carga Tumoral/efeitos dos fármacos , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The ability to grow in anchorage-independent conditions is an important feature of malignant cells, and it is well-established that cellular phenotypes in adherent cultures can differ widely from phenotypes observed in xenografts and anchorage-independent conditions. The anchorage-independent soft-agar colony formation assay has been widely used as a bridge between adherent cell cultures and animal tumor studies, providing a reliable in vitro tool to predict the tumorigenicity of cancer cells. However, this functional assay is limited in its utility for molecular mechanistic studies, as currently there is no reliable method that allows the extraction of biological macromolecules from cells embedded in soft-agar matrices, especially in experimental conditions where no visible colonies form. We developed a set of new methods that enable the extraction of DNA, RNA and proteins directly from cells embedded in soft agar, allowing for a wide range of molecular signaling analysis. Using the new methods and human mammary epithelial cells (HMECs), we studied the role of epithelial-mesenchymal transition (EMT) in the ability of HMECs to form colonies in soft agar. We found that, when cultured in soft agar instead of in adherent cultures, immortalized non-malignant HME-hTERT cells upregulated the epithelial program, which was noted to be necessary for their survival in this anchorage-independent condition. Overexpression of SV40 small T antigen (ST) or the EMT master-regulator SNAI1 negates this requirement and significantly enhances colony formation in soft agar driven by mutant-RAS. Interestingly, we found that, similar to SNAI1, ST also promotes EMT changes in HMECs, providing further support for EMT as a prerequisite for the efficient anchorage-independent colony formation driven by mutant-RAS in our HMEC model.
RESUMO
Cancer stem cells possess the capacity for self-renewal and resistance to chemotherapy. It is therefore crucial to understand the molecular regulators of stemness in the quest to develop effective cancer therapies. TAZ is a transcription activator that promotes stem cell functions in post-development mammalian cells; suppression of TAZ activity reduces or eliminates cancer stemness in select cancers. Isoprenylcysteine carboxylmethyltransferase (ICMT) is the unique enzyme of the last step of posttranslational prenylation processing pathway that modifies several oncogenic proteins, including RAS. We found that suppression of ICMT results in reduced self-renewal/stemness in KRAS-driven pancreatic and breast cancer cells. Silencing of ICMT led to significant reduction of TAZ protein levels and loss of self-renewal ability, which could be reversed by overexpressing mutant KRAS, demonstrating the functional impact of ICMT modification on the ability of KRAS to control TAZ stability and function. Contrary to expectation, YAP protein levels appear to be much less susceptible than TAZ to the regulation by ICMT and KRAS, and YAP is less consequential in regulating stemness characteristics in these cells. Further, we found that the ICMT-dependent KRAS regulation of TAZ was mediated through RAF, but not PI3K, signaling. Functionally, we demonstrate that a signaling cascade from ICMT modification of KRAS to TAZ protein stability supports cancer cell self-renewal abilities in both in vitro and in vivo settings. In addition, studies using the proof-of-concept small molecule inhibitors of ICMT confirmed its role in regulating TAZ and self-renewal, demonstrating the potential utility of targeting ICMT to control aggressive KRAS-driven cancers.
Assuntos
Neoplasias da Mama/metabolismo , Células-Tronco Neoplásicas/metabolismo , Neoplasias Pancreáticas/metabolismo , Proteínas Metiltransferases/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Transativadores/metabolismo , Animais , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Autorrenovação Celular/fisiologia , Desoxicitidina/análogos & derivados , Desoxicitidina/farmacologia , Doxorrubicina/farmacologia , Feminino , Células HEK293 , Xenoenxertos , Humanos , Sistema de Sinalização das MAP Quinases , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Mutação , Células-Tronco Neoplásicas/efeitos dos fármacos , Células-Tronco Neoplásicas/patologia , Neoplasias Pancreáticas/tratamento farmacológico , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patologia , Proteínas Metiltransferases/genética , Proteínas Proto-Oncogênicas p21(ras)/genética , Transativadores/genética , Proteínas com Motivo de Ligação a PDZ com Coativador Transcricional , GencitabinaRESUMO
GNA13, the α subunit of a heterotrimeric G protein, mediates signaling through G-protein-coupled receptors (GPCRs). GNA13 is up-regulated in many solid tumors, including prostate cancer, where it contributes to tumor initiation, drug resistance, and metastasis. To better understand how GNA13 contributes to tumorigenesis and tumor progression, we compared the entire transcriptome of PC3 prostate cancer cells with those cells in which GNA13 expression had been silenced. This analysis revealed that GNA13 levels affected multiple CXC-family chemokines. Further investigation in three different prostate cancer cell lines singled out pro-tumorigenic CXC motif chemokine ligand 5 (CXCL5) as a target of GNA13 signaling. Elevation of GNA13 levels consistently induced CXCL5 RNA and protein expression in all three cell lines. Analysis of the CXCL5 promoter revealed that the -505/+62 region was both highly active and influenced by GNA13, and a single NF-κB site within this region of the promoter was critical for GNA13-dependent promoter activity. ChIP experiments revealed that, upon induction of GNA13 expression, occupancy at the CXCL5 promoter was significantly enriched for the p65 component of NF-κB. GNA13 knockdown suppressed both p65 phosphorylation and the activity of a specific NF-κB reporter, and p65 silencing impaired the GNA13-enhanced expression of CXCL5. Finally, blockade of Rho GTPase activity eliminated the impact of GNA13 on NF-κB transcriptional activity and CXCL5 expression. Together, these findings suggest that GNA13 drives CXCL5 expression by transactivating NF-κB in a Rho-dependent manner in prostate cancer cells.
Assuntos
Quimiocina CXCL5/metabolismo , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/metabolismo , Regulação Neoplásica da Expressão Gênica , Proteínas de Neoplasias/metabolismo , Neoplasias da Próstata/metabolismo , Transdução de Sinais , Fator de Transcrição RelA/metabolismo , Ativação Transcricional , Quimiocina CXCL5/genética , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/genética , Humanos , Masculino , Proteínas de Neoplasias/genética , Células PC-3 , Neoplasias da Próstata/genética , Fator de Transcrição RelA/genéticaRESUMO
Cancer cells possess metabolic properties that are different from benign cells. These unique characteristics have become attractive targets that are being actively investigated for cancer therapy. p21cip1/waf1, also known as Cyclin-Dependent Kinase inhibitor 1A, is encoded by the CDKN1A gene. It is a major p53 target gene involved in cell cycle progression that has been extensively evaluated. To date, p21 has been reported to regulate various cell functions, both dependent and independent of p53. Besides regulating the cell cycle, p21 also modulates apoptosis, induces senescence, and maintains cellular quiescence in response to various stimuli. p21 transcription is induced in response to stresses, including those from oxidative and chemotherapeutic treatment. A recent study has shown that in response to metabolic stresses such as nutrient and energy depletion, p21 expression is induced to regulate various cell functions. Despite the biological significance, the mechanism of p21 regulation in cancer adaptation to metabolic stress is underexplored and thus represents an exciting field. This review focuses on the recent development of p21 regulation in response to metabolic stress and its impact in inducing cell cycle arrest and death in cancer cells.
RESUMO
Metformin has been extensively studied for its impact on cancer cell metabolism and anticancer potential. Despite evidence of significant reduction in cancer occurrence in diabetic patients taking metformin, phase II cancer trials of the agent have been disappointing, quite possibly because of the lack of molecular mechanism-based patient stratification. In an effort to identify cancers that are responsive to metformin, we discovered that mitochondria respiratory capacity and respiratory reserve, which vary widely among cancer cells, correlate strongly to metformin sensitivity in both the in vitro and in vivo settings. A causal relationship between respiratory function and metformin sensitivity is demonstrated in studies in which we lowered respiratory capacity by either genetic knockdown or pharmacologic suppression of electron transport chain components, rendering cancer cells more vulnerable to metformin. These findings led us to predict, and experimentally validate, that metformin and AMP kinase inhibition synergistically suppress cancer cell proliferation.
Assuntos
Transporte de Elétrons/genética , Metformina/farmacologia , Mitocôndrias/metabolismo , Neoplasias/tratamento farmacológico , Animais , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Transporte de Elétrons/efeitos dos fármacos , Xenoenxertos , Humanos , Metformina/metabolismo , Camundongos , Mitocôndrias/efeitos dos fármacos , Neoplasias/genética , Neoplasias/metabolismo , Oxirredução/efeitos dos fármacosRESUMO
Treatment failure in solid tumors occurs due to the survival of specific subpopulations of cells that possess tumor-initiating (TIC) phenotypes. Studies have implicated G protein-coupled-receptors (GPCRs) in cancer progression and the acquisition of TIC phenotypes. Many of the implicated GPCRs signal through the G protein GNA13. In this study, we demonstrate that GNA13 is upregulated in many solid tumors and impacts survival and metastases in patients. GNA13 levels modulate drug resistance and TIC-like phenotypes in patient-derived head and neck squamous cell carcinoma (HNSCC) cells in vitro and in vivo. Blockade of GNA13 expression, or of select downstream pathways, using small-molecule inhibitors abrogates GNA13-induced TIC phenotypes, rendering cells vulnerable to standard-of-care cytotoxic therapies. Taken together, these data indicate that GNA13 expression is a potential prognostic biomarker for tumor progression, and that interfering with GNA13-induced signaling provides a novel strategy to block TICs and drug resistance in HNSCCs.
Assuntos
Transformação Celular Neoplásica/genética , Resistencia a Medicamentos Antineoplásicos/genética , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/metabolismo , Subunidades alfa de Proteínas de Ligação ao GTP/genética , Carcinoma de Células Escamosas de Cabeça e Pescoço/genética , Animais , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Biomarcadores Tumorais/genética , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Transformação Celular Neoplásica/efeitos dos fármacos , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/genética , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Fenótipo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Carcinoma de Células Escamosas de Cabeça e Pescoço/tratamento farmacológico , Carcinoma de Células Escamosas de Cabeça e Pescoço/patologia , Células Tumorais CultivadasRESUMO
Abstract: GNA12 is the α subunit of a heterotrimeric G protein that possesses oncogenic potential. Activated GNA12 also promotes prostate and breast cancer cell invasion in vitro and in vivo, and its expression is up-regulated in many tumors, particularly metastatic tissues. In this study, we explored the control of expression of GNA12 in prostate cancer cells. Initial studies on LnCAP (low metastatic potential, containing low levels of GNA12) and PC3 (high metastatic potential, containing high GNA12 levels) cells revealed that GNA12 mRNA levels correlated with protein levels, suggesting control at the transcriptional level. To identify potential factors controlling GNA12 transcription, we cloned the upstream 5' regulatory region of the human GNA12 gene and examined its activity using reporter assays. Deletion analysis revealed the highest level of promoter activity in a 784 bp region, and subsequent in silico analysis indicated the presence of transcription factor binding sites for C/EBP (CCAAT/enhancer binding protein), CREB1 (cAMP-response-element-binding protein 1), and c-Jun in this minimal element for transcriptional control. A small interfering RNA (siRNA) knockdown approach revealed that silencing of c-Jun expression significantly reduced GNA12 5' regulatory region reporter activity. In addition, chromatin immunoprecipitation assays confirmed that c-Jun binds to the GNA12 5' regulatory region in PC3 cells. Silencing of c-Jun expression reduced mRNA and protein levels of GNA12, but not the closely-related GNA13, in prostate cancer cells. Understanding the mechanisms by which GNA12 expression is controlled may aid in the development of therapies that target key elements responsible for GNA12-mediated tumor progression.
Assuntos
Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP/genética , Regulação Neoplásica da Expressão Gênica , Neoplasias da Próstata/genética , Neoplasias da Próstata/metabolismo , Proteínas Proto-Oncogênicas c-jun/metabolismo , Transcrição Gênica , Sítios de Ligação , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Linhagem Celular Tumoral , Movimento Celular/genética , Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP/metabolismo , Inativação Gênica , Humanos , Masculino , Regiões Promotoras Genéticas , Ligação Proteica , Proteínas Proto-Oncogênicas c-jun/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ativação TranscricionalRESUMO
Pancreatic cancer remains one of the most difficult to treat human cancers despite recent advances in targeted therapy. Inhibition of isoprenylcysteine carboxylmethyltransferase (ICMT), an enzyme that posttranslationally modifies a group of proteins including several small GTPases, suppresses proliferation of some human cancer cells. However, the efficacy of ICMT inhibition on human pancreatic cancer has not been evaluated. In this study, we have evaluated a panel of human pancreatic cancer cell lines and identified those that are sensitive to ICMT inhibition. In these cells, ICMT suppression inhibited proliferation and induced apoptosis. This responsiveness to ICMT inhibition was confirmed in in vivo xenograft tumor mouse models using both a small-molecule inhibitor and shRNA-targeting ICMT. Mechanistically, we found that, in sensitive pancreatic cancer cells, ICMT inhibition induced mitochondrial respiratory deficiency and cellular energy depletion, leading to significant upregulation of p21. Furthermore, we characterized the role of p21 as a regulator and coordinator of cell signaling that responds to cell energy depletion. Apoptosis, but not autophagy, that is induced via p21-activated BNIP3 expression accounts for the efficacy of ICMT inhibition in sensitive pancreatic cancer cells in both in vitro and in vivo models. In contrast, cells resistant to ICMT inhibition demonstrated no mitochondria dysfunction or p21 signaling changes under ICMT suppression. These findings not only identify pancreatic cancers as potential therapeutic targets for ICMT suppression but also provide an avenue for identifying those subtypes that would be most responsive to agents targeting this critical enzyme. Mol Cancer Ther; 16(5); 914-23. ©2017 AACR.
Assuntos
Proteínas de Membrana/genética , Neoplasias Pancreáticas/tratamento farmacológico , Proteínas Metiltransferases/antagonistas & inibidores , Proteínas Proto-Oncogênicas/genética , Proteínas rho de Ligação ao GTP/genética , Animais , Apoptose/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Inibidores Enzimáticos/administração & dosagem , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Camundongos , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patologia , Proteínas Metiltransferases/genética , Transdução de Sinais/efeitos dos fármacos , Bibliotecas de Moléculas Pequenas/administração & dosagem , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Gα13 (encoded by GNA13 gene) is the alpha subunit of a heterotrimeric G-protein that mediates signaling through specific G-protein-coupled receptors (GPCRs). Increased GNA13 expression has been observed in metastatic breast cancer cells. Recently, we have shown that enhanced GNA13 signaling in MCF-10a cells, a benign breast cancer cell line increased its invasiveness. Previous studies have reported that Kallikrein-related peptidases (KLKs 1-15) are down-regulated in breast tumors and may have a tumor protective function. However, the mechanisms that lead to the down-regulation of KLK genes in breast cancer are yet to be elucidated. We found that enhanced GNA13 signaling represses KLK gene expression in breast cancer, and undertook examination of the mechanisms involved. A microarray analysis revealed down-regulation of several members of the Kallikrein-related peptidases (KLK) gene family, namely KLK5, KLK6, KLK7, KLK8 and KLK10, in MCF-10a lines with enhanced GNA13 protein expression. Using real-time PCR and promoter analysis, we identified that the mRNA expression and promoter activities of these KLKs are suppressed upon enforced expression of GNA13 in MCF-10a cells. Using Rhotekin pull-down assays, we identified that GNA13 suppressed Rho-A activation and protein levels in MCF-10a cells. Blocking Rho-A activation using C3-toxin or by inhibiting its down-stream effector, Rho-associated kinase (ROCK), reduced the above-mentioned KLK mRNAs in MCF-10A cells. Importantly, in a metastatic breast cancer cell line MDA-MB-157, knock down of GNA13 alone was sufficient to induce the expression KLK mRNAs. Taken together, our findings suggested that enhanced GNA13 signaling down-regulates KLK gene transcription. The ability of enhanced GNA13 signaling to suppress KLK gene expression appears at least in part due to the ability of enhanced GNA13 signaling to negatively impact Rho/ROCK-signaling.
Assuntos
Neoplasias da Mama/genética , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/metabolismo , Calicreínas/genética , Transdução de Sinais , Proteína rhoA de Ligação ao GTP/metabolismo , Toxinas Bacterianas/farmacologia , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/genética , Feminino , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Humanos , Calicreínas/metabolismo , Regiões Promotoras Genéticas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/metabolismo , Reprodutibilidade dos Testes , Transdução de Sinais/efeitos dos fármacos , Quinases Associadas a rho/metabolismoRESUMO
GNA13 is the most frequently mutated gene in germinal center (GC)-derived B-cell lymphomas, including nearly a quarter of Burkitt lymphoma and GC-derived diffuse large B-cell lymphoma. These mutations occur in a pattern consistent with loss of function. We have modeled the GNA13-deficient state exclusively in GC B cells by crossing the Gna13 conditional knockout mouse strain with the GC-specific AID-Cre transgenic strain. AID-Cre(+) GNA13-deficient mice demonstrate disordered GC architecture and dark zone/light zone distribution in vivo, and demonstrate altered migration behavior, decreased levels of filamentous actin, and attenuated RhoA activity in vitro. We also found that GNA13-deficient mice have increased numbers of GC B cells that display impaired caspase-mediated cell death and increased frequency of somatic hypermutation in the immunoglobulin VH locus. Lastly, GNA13 deficiency, combined with conditional MYC transgene expression in mouse GC B cells, promotes lymphomagenesis. Thus, GNA13 loss is associated with GC B-cell persistence, in which impaired apoptosis and ongoing somatic hypermutation may lead to an increased risk of lymphoma development.
Assuntos
Linfócitos B/metabolismo , Subunidades alfa de Proteínas de Ligação ao GTP/metabolismo , Centro Germinativo/metabolismo , Linfoma de Células B/metabolismo , Animais , Linfócitos B/patologia , Subunidades alfa de Proteínas de Ligação ao GTP/genética , Centro Germinativo/patologia , Cadeias Pesadas de Imunoglobulinas/genética , Cadeias Pesadas de Imunoglobulinas/metabolismo , Região Variável de Imunoglobulina/genética , Região Variável de Imunoglobulina/metabolismo , Linfoma de Células B/genética , Linfoma de Células B/patologia , Masculino , Camundongos , Camundongos Knockout , Proteínas Proto-Oncogênicas c-myc/biossíntese , Proteínas Proto-Oncogênicas c-myc/genéticaRESUMO
The modification of eukaryotic proteins by isoprenoid lipids, which is known as prenylation, controls the localization and activity of a range of proteins that have crucial functions in biological regulation. The roles of prenylated proteins in cells are well conserved across species, underscoring the biological and evolutionary importance of this lipid modification pathway. Genetic suppression and pharmacological inhibition of the protein prenylation machinery have provided insights into several cellular processes and into the aetiology of diseases in which prenylation is involved. The functional dependence of prenylation substrates, such as RAS proteins, on this modification and the therapeutic potential of targeting the prenylation process in pathological conditions accentuate the need to fully understand this form of post-translational modification.
Assuntos
Alquil e Aril Transferases/metabolismo , Prenilação de Proteína , Processamento de Proteína Pós-Traducional , Terpenos/metabolismo , Proteínas ras/metabolismo , Envelhecimento/genética , Envelhecimento/metabolismo , Alquil e Aril Transferases/antagonistas & inibidores , Alquil e Aril Transferases/genética , Animais , Antineoplásicos/farmacologia , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Transformação Celular Neoplásica/patologia , Endopeptidases/genética , Endopeptidases/metabolismo , Inibidores Enzimáticos/farmacologia , Humanos , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Neoplasias/enzimologia , Neoplasias/genética , Neoplasias/patologia , Neoplasias/prevenção & controle , Transporte Proteico , Proteínas ras/antagonistas & inibidores , Proteínas ras/genéticaRESUMO
The process of protein prenylation involves the covalent linkage of either farnesyl (15-carbon) or geranylgeranyl (20-carbon) isoprenoid lipds to conserved cysteine residues in the carboxyl-terminus of proteins. Protein geranylgeranyltransferase I (GGTase-I) is the enzyme that catalyzes the addition of the geranylgeranyl moiety from geranylgeranyl pyrophosphate to the target protein, which contains a Cterminal consensus sequence termed a CaaX motif. Geranylgeranylation is important to the function of a number of proteins, including the majority of Rho GTPases, G protein gamma subunits, and several other regulatory proteins. Studies over the past two decades have revealed that many of these proteins contribute to tumor development and metastasis. Blocking Rho GTPase activity through inhibition of GGTase-I in particular has been advanced as a potential strategy for disease therapy. This review will provide an overview of the CaaX prenyltransferases, the rationale for targeting GGTase-I in cancer in particular, and the current status of GGTase-I inhibitor (GGTI) development.
Assuntos
Alquil e Aril Transferases/metabolismo , Neoplasias/metabolismo , Animais , Inibidores Enzimáticos/farmacologia , Inibidores Enzimáticos/uso terapêutico , Farnesiltranstransferase/metabolismo , Humanos , Neoplasias/tratamento farmacológico , Prenilação de Proteína/efeitos dos fármacosRESUMO
Despite the success of BCR-ABL1 tyrosine kinase inhibitors in patients with chronic myeloid leukemia (CML), resistance to tyrosine kinase inhibitors remains a therapeutic challenge. One strategy used to overcome resistance is combination of existing BCR-ABL1 tyrosine kinase inhibitors with agents that target alternative pathways. We report that inhibition of isoprenylcysteine carboxylmethyltransferase (Icmt), a key enzyme in the protein prenylation pathway, with the selective inhibitor cysmethynil enhances the effect of BCR-ABL1 tyrosine kinase inhibitors in killing CML cells. Cysmethynil augments tyrosine kinase inhibitor-induced apoptosis in both BCR-ABL1 wild type and BCR-ABL1 kinase domain mutant-expressing cell lines. Importantly, the enhanced apoptosis observed with the combination of cysmethynil and imatinib is significant only in primary CML CD34+ progenitor cells, not normal cord blood progenitor cells. The combination was also selective in inhibiting colony formation in CML CD34+ cells. The enhanced apoptosis appears to be due to combination of immediate and persistent inhibition of MAPK signaling. Consistent with in vitro studies, cysmethynil and imatinib, in combination, enhance the in vivo effects of either drug used alone. We found that simultaneous inhibition of BCR-ABL1 and Icmt may represent a potential therapeutic strategy for CML.
Assuntos
Apoptose/efeitos dos fármacos , Proteínas de Fusão bcr-abl/antagonistas & inibidores , Mesilato de Imatinib/farmacologia , Indóis/farmacologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Proteínas Metiltransferases/antagonistas & inibidores , Animais , Feminino , Proteínas de Fusão bcr-abl/genética , Proteínas de Fusão bcr-abl/metabolismo , Humanos , Leucemia Mielogênica Crônica BCR-ABL Positiva/enzimologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/genética , Masculino , Camundongos , Células-Tronco Neoplásicas/enzimologia , Células-Tronco Neoplásicas/patologia , Proteínas Metiltransferases/genética , Proteínas Metiltransferases/metabolismoRESUMO
BACKGROUND: Gα13 (GNA13) is the α subunit of a heterotrimeric G protein that mediates signaling through specific G protein-coupled receptors (GPCRs). Our recent study showed that control of GNA13 expression by specific microRNAs (miRNAs or miRs) is important for prostate cancer cell invasion. However, little is known about the control of GNA13 expression in breast cancers. This project was carried out to determine (i) whether enhanced GNA13 expression is important for breast cancer cell invasion, and (ii) if so, the mechanism of deregulation of GNA13 expression in breast cancers. METHODS: To determine the probable miRNAs regulating GNA13, online miRNA target prediction tool Targetscan and Luciferase assays with GNA13-3'-UTR were used. Effect of miRNAs on GNA13 mRNA, protein and invasion was studied using RT-PCR, western blotting and in vitro Boyden chamber assay respectively. Cell proliferation was done using MTT assays. RESULTS: Overexpression of GNA13 in MCF-10a cells induced invasion, whereas knockdown of GNA13 expression in MDA-MB-231 cells inhibited invasion. Expression analysis of miRNAs predicted to bind the 3'-UTR of GNA13 revealed that miR-31 exhibited an inverse correlation to GNA13 protein expression in breast cancer cells. Ectopic expression of miR-31 in MDA-MB-231 cells significantly reduced GNA13 mRNA and protein levels, as well as GNA13-3'-UTR-reporter activity. Conversely, blocking miR-31 activity in MCF-10a cells induced GNA13 mRNA, protein and 3'-UTR reporter activity. Further, expression of miR-31 significantly inhibited MDA-MB-231 cell invasion, and this effect was partly rescued by ectopic expression of GNA13 in these cells. Examination of 48 human breast cancer tissues revealed that GNA13 mRNA levels were inversely correlated to miR-31 levels. CONCLUSIONS: These data provide strong evidence that GNA13 expression in breast cancer cells is regulated by post-transcriptional mechanisms involving miR-31. Additionally our data shows that miR-31 regulates breast cancer cell invasion partially via targeting GNA13 expression in breast cancer cells. Loss of miR-31 expression and increased GNA13 expression could be used as biomarkers of breast cancer progression.
Assuntos
Fatores de Transcrição de Zíper de Leucina Básica/genética , Neoplasias da Mama/genética , Regulação Neoplásica da Expressão Gênica/genética , MicroRNAs/genética , Invasividade Neoplásica/genética , Regiões 3' não Traduzidas/genética , Fator 6 Ativador da Transcrição , Biomarcadores Tumorais/genética , Mama/patologia , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Movimento Celular/genética , Proliferação de Células/genética , Feminino , Humanos , Invasividade Neoplásica/patologia , Processamento Pós-Transcricional do RNA/genética , RNA Mensageiro/genéticaRESUMO
BACKGROUND: Recent studies on the involvement of the G12 family of heterotrimeric G proteins (Gα12 and Gα13, the products of the GNA12 and GNA13 genes, respectively) in oncogenic pathways have uncovered a link between G12 signaling and cancer progression. However, despite a well characterized role of Rho GTPases, the potential role of secreted factors in the capacity of G12 signaling to promote invasion of cancer cells is just beginning to be addressed. METHODS: MDA-MB-231 and MCF10A breast cancer cell lines were employed as a model system to explore the involvement of secreted factors in G12-stimulated cell invasion. Factors secreted by cells expressing dominant-active Gα12 were identified by protein array, and their involvement in breast cancer cell invasion was assessed through both RNAi-mediated knockdown and antibody neutralization approaches. Bioinformatics analysis of the promoter elements of the identified factors suggested NF-κB elements played a role in their enhanced expression, which was tested by chromatin immunoprecipitation. RESULTS: We found that signaling through the Gα12 in MDA-MB-231 and MCF10A breast cancer cell lines enhances expression of interleukins (IL)-6 and -8, and matrix metalloproteinase (MMP)-2, and that these secreted factors play a role in G12-stimulated cell invasion. Furthermore, the enhanced expression of these secreted factors was found to be facilitated by the activation of their corresponding promoters, where NF-κB seems to be one of the major regulators. Inhibition of IL-6 and IL-8, or MMP-2 activity significantly decreased Gα12-mediated cell invasion. CONCLUSIONS: These studies confirm and extend findings that secreted factors contribute to the oncogenic potential of G12 signaling, and suggest potential therapeutic targets to control this process.