RESUMO
SPROUTY-2 (SPRY2) is a modulator of tyrosine kinase receptor signaling with receptor- and cell type-dependent inhibitory or enhancing effects. Studies on the action of SPRY2 in major cancers are conflicting and its role remains unclear. Here we have dissected SPRY2 action in human colon cancer. Global transcriptomic analyses show that SPRY2 downregulates genes encoding tight junction proteins such as claudin-7 and occludin and other cell-to-cell and cell-to-matrix adhesion molecules in human SW480-ADH colon carcinoma cells. Moreover, SPRY2 represses LLGL2/HUGL2, PATJ1/INADL and ST14, main regulators of the polarized epithelial phenotype, and ESRP1, an epithelial-to-mesenchymal transition (EMT) inhibitor. A key action of SPRY2 is the upregulation of the major EMT inducer ZEB1, as these effects are reversed by ZEB1 knock-down by means of RNA interference. Consistently, we found an inverse correlation between the expression level of claudin-7 and those of SPRY2 and ZEB1 in human colon tumors. Mechanistically, ZEB1 upregulation by SPRY2 results from the combined induction of ETS1 transcription factor and the repression of microRNAs (miR-200 family, miR-150) that target ZEB1 RNA. Moreover, SPRY2 increased AKT activation by epidermal growth factor, whereas AKT and also Src inhibition reduced the induction of ZEB1. Altogether, these data suggest that AKT and Src are implicated in SPRY2 action. Collectively, these results show a tumorigenic role of SPRY2 in colon cancer that is based on the dysregulation of tight junction and epithelial polarity master genes via upregulation of ZEB1. The dissection of the mechanism of action of SPRY2 in colon cancer cells is important to understand the upregulation of this gene in a subset of patients with this neoplasia that have poor prognosis.
Assuntos
Neoplasias do Colo/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Membrana/metabolismo , MicroRNAs/metabolismo , Proteína Proto-Oncogênica c-ets-1/metabolismo , Homeobox 1 de Ligação a E-box em Dedo de Zinco/metabolismo , Adesão Celular/genética , Linhagem Celular Tumoral , Polaridade Celular/genética , Proliferação de Células/fisiologia , Neoplasias do Colo/genética , Neoplasias do Colo/patologia , Células Epiteliais , Células HEK293 , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Proteínas de Membrana/genética , MicroRNAs/genética , Fenótipo , Proteína Proto-Oncogênica c-ets-1/genética , Transdução de Sinais , Transfecção , Regulação para Cima , Homeobox 1 de Ligação a E-box em Dedo de Zinco/genéticaRESUMO
The presence of hypoxic regions in solid tumors is an adverse prognostic factor for patient outcome. Here, we show that hypoxia induces the expression of Ephrin-A3 through a novel hypoxia-inducible factor (HIF)-mediated mechanism. In response to hypoxia, the coding EFNA3 mRNA levels remained relatively stable, but HIFs drove the expression of previously unknown long noncoding (lnc) RNAs from EFNA3 locus and these lncRNA caused Ephrin-A3 protein accumulation. Ephrins are cell surface proteins that regulate diverse biological processes by modulating cellular adhesion and repulsion. Mounting evidence implicates deregulated ephrin function in multiple aspects of tumor biology. We demonstrate that sustained expression of both Ephrin-A3 and novel EFNA3 lncRNAs increased the metastatic potential of human breast cancer cells, possibly by increasing the ability of tumor cells to extravasate from the blood vessels into surrounding tissue. In agreement, we found a strong correlation between high EFNA3 expression and shorter metastasis-free survival in breast cancer patients. Taken together, our results suggest that hypoxia could contribute to metastatic spread of breast cancer via HIF-mediated induction of EFNA3 lncRNAs and subsequent Ephrin-A3 protein accumulation.
Assuntos
Neoplasias da Mama/metabolismo , Loci Gênicos , Fator 1 Induzível por Hipóxia/metabolismo , Proteínas de Neoplasias/metabolismo , RNA Longo não Codificante/biossíntese , RNA Neoplásico/biossíntese , Animais , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Hipóxia Celular/genética , Linhagem Celular Tumoral , Efrina-A3/genética , Efrina-A3/metabolismo , Feminino , Células Endoteliais da Veia Umbilical Humana , Humanos , Fator 1 Induzível por Hipóxia/genética , Camundongos , Camundongos Nus , Metástase Neoplásica , Proteínas de Neoplasias/genética , RNA Longo não Codificante/genética , RNA Neoplásico/genética , Peixe-ZebraRESUMO
Pigment epithelium-derived factor (PEDF) is a multifunctional secreted glycoprotein that displays broad anti-tumor activity based on dual targeting of the tumor microenvironment (anti-angiogenic action) and the tumor cells (direct anti-tumor action). Here, we show that PEDF expression is high in melanocytes, but it is lost during malignant progression of human melanoma. Using a high-throughput analysis of the data from microarray studies of molecular profiling of human melanoma, we found that PEDF expression is lost in highly invasive melanomas. In paired cell lines established from the same lesion but representing the high and low extremes of malignant potential, abundant PEDF expression was restricted to the poorly aggressive counterparts. We used RNA interference to directly address the functional consequences of PEDF silencing. PEDF knockdown in poorly aggressive melanoma cell lines augmented migration, invasion and vasculogenic mimicry, which translated into an increased in vivo metastatic potential. PEDF interference also significantly enhanced the migratory and invasive capability of normal melanocytes and moderately increased their proliferative potential. Our results show that loss of PEDF enables melanoma cells to acquire an invasive phenotype and, therefore, modulation of this multifunctional factor could be critical for the malignant progression of human melanoma.
