RESUMEN
Transforming Growth Factor-ß (TGF-ß) plays crucial and complex roles in liver and gastrointestinal cancers. These include a multitude of distinct functions, such as maintaining stem cell homeostasis, promoting fibrosis, immune modulating, as a tumor suppressor and paradoxically, as a tumor progressor. However, key mechanisms for the switches responsible for these distinct actions are poorly understood, and remain a challenge. The Cancer Genome Atlas (TCGA) analyses and genetically engineered mouse models now provide an integrated approach to dissect these multifaceted and context-dependent driving roles of the TGF-ß pathway. In this review, we will discuss the molecular mechanisms of TGF-ß signaling, focusing on colorectal, gastric, pancreatic, and liver cancers. Novel drugs targeting the TGF-ß pathway have been developed over the last decade, and some have been proven effective in clinical trials. A better understanding of the TGF-ß pathway may improve our ability to target it, thus providing more tools to the armamentarium against these deadly cancers.
Asunto(s)
Neoplasias Gastrointestinales/metabolismo , Neoplasias Hepáticas/metabolismo , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismo , Animales , Antineoplásicos/uso terapéutico , Neoplasias Gastrointestinales/tratamiento farmacológico , Neoplasias Gastrointestinales/genética , Neoplasias Gastrointestinales/patología , Regulación Neoplásica de la Expresión Génica , Humanos , Neoplasias Hepáticas/tratamiento farmacológico , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patología , Terapia Molecular Dirigida , Mutación , Células Madre Neoplásicas/metabolismo , Receptores de Factores de Crecimiento Transformadores beta/antagonistas & inhibidores , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Transducción de Señal/efectos de los fármacos , Factor de Crecimiento Transformador beta/antagonistas & inhibidores , Factor de Crecimiento Transformador beta/genéticaRESUMEN
Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide, with few effective therapeutic options for advanced disease. At least 40% of HCCs are clonal, potentially arising from STAT3+, NANOG+ and OCT3/4+ liver progenitor/stem cell transformation, along with inactivation of transforming growth factor-beta (TGF-beta) signaling. Here we report significantly greater signal transducer and activator of transcription 3 (STAT3) and tyrosine phosphorylated STAT3 in human HCC tissues (P<0.0030 and P<0.0455, respectively) than in human normal liver. Further, in HCC cells with loss of response to TGF-beta, NSC 74859, a STAT3-specific inhibitor, markedly suppresses growth. In contrast, CD133(+) status did not affect the response to STAT3 inhibition: both CD133(+) Huh-7 cells and CD133(-) Huh-7 cells are equally sensitive to NSC 74859 treatment and STAT3 inhibition, with an IC(50) of 100 muM. Thus, the TGF-beta/beta2 spectrin (beta2SP) pathway may reflect a more functional 'stem/progenitor' state than CD133. Furthermore, NSC 74859 treatment of Huh-7 xenografts in nude mice significantly retarded tumor growth, with an effective dose of only 5 mg/kg. Moreover, NSC 74859 inhibited tyrosine phosphorylation of STAT3 in HCC cells in vivo. We conclude that inhibiting interleukin 6 (IL6)/STAT3 in HCCs with inactivation of the TGF-beta/beta2SP pathway is an effective approach in management of HCCs. Thus, IL6/STAT3, a major signaling pathway in HCC stem cell renewal and proliferation, can provide a novel approach to the treatment of specific HCCs.
Asunto(s)
Ácidos Aminosalicílicos , Bencenosulfonatos/uso terapéutico , Carcinoma Hepatocelular/tratamiento farmacológico , Neoplasias Hepáticas/tratamiento farmacológico , Factor de Transcripción STAT3/antagonistas & inhibidores , Factor de Crecimiento Transformador beta/metabolismo , Antígeno AC133 , Ácido Aminosalicílico/uso terapéutico , Animales , Antígenos CD/metabolismo , Apoptosis/efectos de los fármacos , Western Blotting , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Ensayo de Unidades Formadoras de Colonias , Femenino , Glicoproteínas/metabolismo , Humanos , Técnicas para Inmunoenzimas , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patología , Ratones , Ratones Desnudos , Péptidos/metabolismo , Fosforilación/efectos de los fármacos , Factor de Transcripción STAT3/metabolismo , Factor de Crecimiento Transformador beta/genética , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Transforming growth factor-beta (TGF-beta) signaling members, TGF-beta receptor type II (TBRII), Smad2, Smad4 and Smad adaptor, embryonic liver fodrin (ELF), are prominent tumor suppressors in gastrointestinal cancers. Here, we show that 40% of elf(+/-) mice spontaneously develop hepatocellular cancer (HCC) with markedly increased cyclin D1, cyclin-dependent kinase 4 (Cdk4), c-Myc and MDM2 expression. Reduced ELF but not TBRII, or Smad4 was observed in 8 of 9 human HCCs (P<0.017). ELF and TBRII are also markedly decreased in human HCC cell lines SNU-398 and SNU-475. Restoration of ELF and TBRII in SNU-398 cells markedly decreases cyclin D1 as well as hyperphosphorylated-retinoblastoma (hyperphosphorylated-pRb). Thus, we show that TGF-beta signaling and Smad adaptor ELF suppress human hepatocarcinogenesis, potentially through cyclin D1 deregulation. Loss of ELF could serve as a primary event in progression toward a fully transformed phenotype and could hold promise for new therapeutic approaches in human HCCs.
Asunto(s)
Carcinoma Hepatocelular/etiología , Carcinoma Hepatocelular/metabolismo , Proteínas Portadoras/fisiología , Ciclinas/metabolismo , Neoplasias Hepáticas Experimentales/etiología , Proteínas de Microfilamentos/fisiología , Transducción de Señal/fisiología , Espectrina/fisiología , Factor de Crecimiento Transformador beta2/antagonistas & inhibidores , Animales , Proteínas Portadoras/genética , Línea Celular Tumoral , Ciclina D , Ciclinas/antagonistas & inhibidores , Humanos , Neoplasias Hepáticas Experimentales/metabolismo , Ratones , Ratones Noqueados , Proteínas de Microfilamentos/deficiencia , Proteínas de Microfilamentos/genética , Fosforilación , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Retinoblastoma/metabolismo , Transducción de Señal/genética , Espectrina/deficiencia , Espectrina/genética , Factor de Crecimiento Transformador beta2/metabolismo , Factor de Crecimiento Transformador beta2/fisiología , Proteínas Supresoras de Tumor/genética , Proteínas Supresoras de Tumor/fisiologíaRESUMEN
In gastrointestinal cells, biological signals for transforming growth factor-beta (TGF-beta) are transduced through transmembrane serine/threonine kinase receptors that signal to Smad proteins. Smad4, a tumor suppressor, is often mutated in human gastrointestinal cancers. The mechanism of Smad4 inactivation, however, remains uncertain and could be through E3-mediated ubiquitination of Smad4/adaptor protein complexes. Disruption of ELF (embryonic liver fodrin), a Smad4 adaptor protein, modulates TGF-beta signaling. We have found that PRAJA, a RING-H2 protein, interacts with ELF in a TGF-beta-dependent manner, with a fivefold increase of PRAJA expression and a subsequent decrease in ELF and Smad4 expression, in gastrointestinal cancer cell lines (P < 0.05). Strikingly, PRAJA manifests substantial E3-dependent ubiquitination of ELF and Smad3, but not Smad4. Delta-PRAJA, which has a deleted RING finger domain at the C terminus, abolishes ubiquitination of ELF. A stable cell line that overexpresses PRAJA exhibits low levels of ELF in comparison to a Delta-PRAJA stable cell line, where ELF expression is high compared to normal controls. The alteration of ELF and/or Smad4 expression and/or function in the TGF-beta signaling pathway may be induced by enhancement of ELF degradation, which is mediated by a high-level expression of PRAJA in gastrointestinal cancers. In hepatocytes, half-life (t(1/2)) and rate constant for degradation (k(D)) of ELF is 1.91 h and 21.72 min(-1) when coupled with ectopic expression of PRAJA in cells stimulated by TGF-beta, compared to PRAJA-transfected unstimulated cells (t(1/2) = 4.33 h and k(D) = 9.6 min(-1)). These studies reveal a mechanism for tumorigenesis whereby defects in adaptor proteins for Smads, such as ELF, can undergo degradation by PRAJA, through the ubiquitin-mediated pathway.
Asunto(s)
Genes Supresores de Tumor , Proteínas/fisiología , Factor de Crecimiento Transformador beta/fisiología , Ubiquitina/metabolismo , Animales , Línea Celular , Proliferación Celular , Cicloheximida/farmacología , Humanos , Inmunohistoquímica , Hígado/metabolismo , Hígado/fisiología , Regeneración Hepática , Ratones , Ubiquitina-Proteína LigasasRESUMEN
Inactivation of the transforming growth factor-beta (TGF-beta) pathway occurs often in malignancies of the gastrointestinal (GI) system. However, only a fraction of sporadic GI tumors exhibit inactivating mutations in early stages of cancer formation, suggesting that other mechanisms play a critical role in the inactivation of this pathway. Here, we show a wide range of GI tumors, including those of the stomach, liver and colon in elf+/- and elf+/- / Smad4+/- mutant mice. We found that embryonic liver fodrin (ELF), a beta-Spectrin originally identified in endodermal stem/progenitor cells committed to foregut lineage, possesses potent antioncogenic activity and is frequently inactivated in GI cancers. Specifically, E-cadherin accumulation at cell-cell contacts and E-cadherin-beta-catenin-dependent epithelial cell-cell adhesion is disrupted in elf+/- / Smad4+/- mutant gastric epithelial cells, and could be rescued by ectopic expression of full-length elf, but not Smad3 or Smad4. Subcellular fractionation revealed that E-cadherin is expressed mainly at the cell membrane after TGF-beta stimulation. In contrast, elf+/- / Smad4+/- mutant tissues showed abnormal distribution of E-cadherin that could be rescued by overexpression of ELF but not Smad3 or Smad4. Our results identify a group of common lethal malignancies in which inactivation of TGF-beta signaling, which is essential for tumor suppression, is disrupted by inactivation of the ELF adaptor protein.
Asunto(s)
Proteínas Portadoras/biosíntesis , Proteínas de Unión al ADN , Neoplasias Gastrointestinales/genética , Proteínas de Microfilamentos/biosíntesis , Factor de Crecimiento Transformador beta/fisiología , Animales , Cadherinas/fisiología , Proteínas Portadoras/fisiología , Adhesión Celular , Células Epiteliales/fisiología , Neoplasias Gastrointestinales/fisiopatología , Perfilación de la Expresión Génica , Ratones , Proteínas de Microfilamentos/fisiología , Transducción de Señal , Proteína Smad4/biosíntesis , Proteína Smad4/genética , beta Catenina/fisiologíaRESUMEN
Three new species of the Dactylogyridae are described from aquarium fishes collected in India and two new genera are proposed: Heterotylus heterotylus n. g., n. sp. from Hypostomus sp. (Loricariidae), Diaphorocleidus armillatus n. g., n. sp. from Gymnocorymbus ternetzi (Characidae) and Urocleidoides vaginoclaustrum n. sp. from Xiphophorus helleri (Poeciliidae). Heterotylus n. g. is characterised by species having overlapping gonads (testis posterodorsal to the ovary), a mid-ventral vaginal aperture, a copulatory complex consisting of a relatively straight copulatory organ unarticulated to a complex accessory piece, erect acute hook thumbs, unexpanded hook shanks, dorsal and ventral anchor/bar complexes and absence of well-defined basal roots of the ventral anchors. Diaphorocleidus n. g. includes species with overlapping gonads (testis posterodorsal to the ovary), submarginal sinistral vaginal pore, a copulatory complex comprising a coiled (counterclockwise) copulatory organ unarticulated to an accessory piece, protruding depressed hook thumb, hook shank with two subunits (proximal subunit expanded), dorsal and ventral anchor/bar complexes and V-shaped bars. The following new combinations are proposed: D. affinis (Mizelle, Kritsky & Crane, 1968) n. comb. (syn. U. affinis Mizelle, Kritsky & Crane, 1968), D. kabatai (Molnar, Hanek & Fernando, 1974) n. comb. (syn. U. kabatai Molnar, Hanek & Fernando, 1974) and D. microstomus (Mizelle, Kritsky & Crane, 1968) n. comb. (syn. U. microstomus Mizelle, Kritsky & Crane, 1968).