RESUMEN
Angiogenesis is required for tumour growth and is induced principally by vascular endothelial growth factor A (VEGF-A). VEGF-A pre-mRNA is alternatively spliced at the terminal exon to produce two families of isoforms, pro- and anti-angiogenic, only the former of which is upregulated in prostate cancer (PCa). In renal epithelial cells and colon cancer cells, the choice of VEGF splice isoforms is controlled by the splicing factor SRSF1, phosphorylated by serine-arginine protein kinase 1 (SRPK1). Immunohistochemistry staining of human samples revealed a significant increase in SRPK1 expression both in prostate intra-epithelial neoplasia lesions as well as malignant adenocarcinoma compared with benign prostate tissue. We therefore tested the hypothesis that the selective upregulation of pro-angiogenic VEGF in PCa may be under the control of SRPK1 activity. A switch in the expression of VEGF165 towards the anti-angiogenic splice isoform, VEGF165b, was seen in PC-3 cells with SRPK1 knockdown (KD). PC-3 SRPK1-KD cells resulted in tumours that grew more slowly in xenografts, with decreased microvessel density. No effect was seen as a result of SRPK1-KD on growth, proliferation, migration and invasion capabilities of PC-3 cells in vitro. Small-molecule inhibitors of SRPK1 switched splicing towards the anti-angiogenic isoform VEGF165b in PC-3 cells and decreased tumour growth when administered intraperitoneally in an orthotopic mouse model of PCa. Our study suggests that modulation of SRPK1 and subsequent inhibition of tumour angiogenesis by regulation of VEGF splicing can alter prostate tumour growth and supports further studies for the use of SRPK1 inhibition as a potential anti-angiogenic therapy in PCa.
Asunto(s)
Inhibidores de la Angiogénesis/farmacología , Neoplasias de la Próstata/tratamiento farmacológico , Neoplasias de la Próstata/metabolismo , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Serina-Treonina Quinasas/metabolismo , Animales , Línea Celular Tumoral , Movimiento Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Humanos , Masculino , Ratones , Ratones Desnudos , Invasividad Neoplásica/patología , Neovascularización Patológica/tratamiento farmacológico , Neovascularización Patológica/metabolismo , Neoplasias de la Próstata/patología , Isoformas de Proteínas/metabolismo , Empalme del ARN/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/metabolismoRESUMEN
OBJECTIVE: Vascular endothelial growth factor (VEGF)-induced vascular permeability has been shown to be dependent on calcium influx, possibly through a transient receptor potential cation channel (TRPC)-mediated cation channel with properties of the TRPC3/6/7 subfamily. To investigate further the involvement of this subfamily, we determined the effects of dominant negative TRPC6 overexpression on VEGF-mediated changes of human microvascular endothelial cell (HMVEC) calcium, proliferation, migration, and sprouting. METHODS: Cytoplasmic calcium concentration was estimated by fura-2 fluorescence spectrophotometry, migration by Boyden chamber assay, sprouting by immunofluorescence imaging of stimulated endothelial cells, and proliferation by flow cytometry. RESULTS: Overexpression of a dominant negative TRPC6 construct in HMVECs inhibited the VEGF-mediated increases in cytosolic calcium, migration, sprouting, and proliferation. In contrast, overexpression of a wild-type TRPC6 construct increased the proliferation and migration of HMVECs. CONCLUSIONS: TRPC6 is an obligatory component of cation channels required for the VEGF-mediated increase in cytosolic calcium and subsequent downstream signaling that leads to processes associated with angiogenesis.