Calreticulin Up‐Regulates VEGFs Expression in Neuroblastoma Cell Lines

Abstract

Neuroblastoma (NB) is a childhood cancer with a low survival rate and great potential for metastasis. Calreticulin (CRT), an ER chaperone protein, is one of the biomarkers of NB. In gastric cancer cells, we have investigated that CRT strongly enhances angiogenesis by promoting the expression of vascular endothelial growth factors (VEGFs). In this study, we aimed to investigate the correlation between the expression of CRT and VEGFs in NB. It was found that over‐expression of CRT up‐regulated VEGF expression at both the mRNA and protein levels in SK‐N‐DZ and SH‐SY5Y cells. CRT RNAi efficiently suppresses CRT expression resulting in down‐regulation of VEGFs.By using ELISA analysis, CRT was shown to significantly enhance VEGF‐A expression in conditioned medium. The CRT‐inducible stNB‐V1 cell line has been established by the lentivirus transduction system We further demonstrated that NB cell apoptosis was not affected by CRT induction in stNB‐V1 cells. Nevertheless, over‐expressing CRT suppressed cell proliferation and enhanced cell differentiation in stNB‐V1 cells, whereas blockage of VEGFR‐1 markedly suppressed expressions of neuron specific markers such as GAP43, NSE, NFH and TrkA. In xenograft experiments, we found that xenograft tumors with induced CRT expression had much smaller sizes. VEGF‐A had a much higher expression level in the tumor samples compared to control samples. These findings suggest that VEGF‐A is involved in CRT‐related neuronal differentiation in NB. Our work may provide important information for developing a new therapeutic strategy to improve the outcome of NB patients.