RESUMEN
Ring finger protein 43 (RNF43) is an E3 ubiquitin ligase that has been described to be frequently mutated in gastrointestinal cancers. RNF43 downregulation was associated with distant metastasis, TNM stage and poorer survival in patients with gastric and colorectal cancers. Functional analysis has shown that overexpressed RNF43 negatively regulates Wnt signalling by ubiquitinating Frizzled receptors and targeting them for degradation and by sequestering T-cell factor 4 (TCF4) to the nuclear membrane, thereby inhibiting Wnt-mediated transcription. In the stomach, RNF43 overexpression was shown to impair stem-like properties and to be negatively correlated with expression of Wnt-target genes. In this study, we show that RNF43 knockdown enhances the tumourigenic potential of gastric and colorectal cancer cell lines in vitro and in vivo. Thus, loss of RNF43 leads to increased proliferation and anchorage-independent growth as well as increased invasive capacity. In a xenograft model, RNF43 depletion enhanced tumour growth. Furthermore, we established two mouse models in which mutations in the RING domain of RNF43 were introduced. In the intestine and colon, loss of Rnf43 did not induce changes in epithelial architecture or proliferation. In contrast, in the stomach, thickening of the mucosa, hyperplasia and cellular atypia were observed in these mice. Notably, this was independent of elevated Wnt signalling. Together, our results show that RNF43 plays a tumour suppressive role in gastric and colorectal cancer cells and that the loss of its function alters gastric tissue homeostasis in vivo.
Asunto(s)
Proliferación Celular/genética , Neoplasias Colorrectales/genética , Intestinos/patología , Neoplasias Gástricas/genética , Estómago/patología , Ubiquitina-Proteína Ligasas/genética , Animales , Células CACO-2 , Carcinogénesis/genética , Carcinogénesis/patología , Línea Celular , Línea Celular Tumoral , Neoplasias Colorrectales/patología , Células HT29 , Humanos , Ratones , Membrana Mucosa/patología , Mutación/genética , Neoplasias Gástricas/patología , Ubiquitinación/genética , Vía de Señalización Wnt/genéticaRESUMEN
The CRISPR/Cas9 system can be used to mutate target sequences by introduction of double-strand breaks followed by imprecise repair. To test its use for conditional gene editing we generated mice transgenic for CD4 promoter-driven Cas9 combined with guide RNA targeting CD2. We found that within CD4(+) and CD8(+) lymphocytes from lymph nodes and spleen 1% and 0.6% were not expressing CD2, respectively. T cells lacking CD2 carryied mutations, which confirmed that Cas9 driven by cell-type specific promoters can edit genes in the mouse and may thus allow targeted studies of gene function in vivo.
Asunto(s)
Antígenos CD2/genética , Sistemas CRISPR-Cas , Edición Génica/métodos , Silenciador del Gen , ARN Guía de Kinetoplastida/genética , Animales , Secuencia de Bases , Antígenos CD2/inmunología , Linfocitos T CD4-Positivos/citología , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/citología , Linfocitos T CD8-positivos/inmunología , Ingeniería Genética , Vectores Genéticos/química , Vectores Genéticos/metabolismo , Inmunofenotipificación , Ganglios Linfáticos/citología , Ganglios Linfáticos/inmunología , Ratones , Ratones Transgénicos , Mutación , Regiones Promotoras Genéticas , ARN Guía de Kinetoplastida/metabolismo , Bazo/citología , Bazo/inmunologíaRESUMEN
Given its fundamental role in development and cancer, the Wnt-ß-catenin signaling pathway is tightly controlled at multiple levels. RING finger protein 43 (RNF43) is an E3 ubiquitin ligase originally found in stem cells and proposed to inhibit Wnt signaling by interacting with the Wnt receptors of the Frizzled family. We detected endogenous RNF43 in the nucleus of human intestinal crypt and colon cancer cells. We found that RNF43 physically interacted with T cell factor 4 (TCF4) in cells and tethered TCF4 to the nuclear membrane, thus silencing TCF4 transcriptional activity even in the presence of constitutively active mutants of ß-catenin. This inhibitory mechanism was disrupted by the expression of RNF43 bearing mutations found in human gastrointestinal tumors, and transactivation of the Wnt pathway was observed in various cells and in Xenopus embryos when the RING domain of RNF43 was mutated. Our findings indicate that RNF43 inhibits the Wnt pathway downstream of oncogenic mutations that activate the pathway. Mimicking or enhancing this inhibitory activity of RNF43 may be useful to treat cancers arising from aberrant activation of the Wnt pathway.
Asunto(s)
Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/metabolismo , Proteínas de Unión al ADN/metabolismo , Membrana Nuclear/metabolismo , Proteínas Oncogénicas/metabolismo , Factores de Transcripción/metabolismo , Vía de Señalización Wnt/fisiología , beta Catenina/metabolismo , Animales , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/genética , Línea Celular Tumoral , Proteínas de Unión al ADN/genética , Humanos , Mutación , Membrana Nuclear/genética , Proteínas Oncogénicas/genética , Factor de Transcripción 4 , Factores de Transcripción/genética , Transcripción Genética , Ubiquitina-Proteína Ligasas , Xenopus laevis , beta Catenina/genéticaRESUMEN
In many different tumor entities, increased expression of tissue inhibitor of metalloproteinases-1 (Timp-1) is associated with poor prognosis. We previously reported in mouse models that elevated systemic levels of Timp-1 induce a gene expression signature in the liver microenvironment increasing the susceptibility of this organ to tumor cells. This host effect was dependent on increased activity of the hepatocyte growth factor (Hgf)/hepatocyte growth factor receptor (Met) signaling pathway. In a recent study we showed that Met signaling is regulated by Timp-1 as it inhibits the Met sheddase A disintegrin and metalloproteinase-10 (Adam-10). The aim of the present study was to elucidate whether the metastatic potential of tumor cells benefits from autocrine Timp-1 as well and involves Adam-10 and Met signaling. In a syngeneic murine model of experimental liver metastasis Timp-1 expression and Met signaling were localized within metastatic colonies and expressed by tumor cells. Knock down of tumor cell Timp-1 suppressed Met signaling in metastases and inhibited metastasis formation and tumor cell-scattering in the liver. In vitro, knock down of tumor cell Timp-1 prevented Hgf-induced Met phosphorylation. Consequently, knock down of Met sheddase Adam-10 triggered auto-phosphorylation and responsiveness to Hgf. Accordingly, Adam-10 knock down increased Met phosphorylation in metastatic foci and induced tumor cell scattering into the surrounding liver parenchyma. In conclusion, these findings show that tumor cell-derived Timp-1 acts as a positive regulator of the metastatic potential and support the concept that proteases and their natural inhibitors, as members of the protease web, are major players of signaling during normal homeostasis and disease.