Study Of PASAL1 Attenuates Gastric Carcinogenesis In Nude Mice By Blocking RAS/ERK Signaling

Background and Objective:Our previous studies have suggested that the RAS GTPase-activating like protein-1(RASALI) functions as a tumor suppressor in vitro, which affects proliferation?metastasis and apoptosis of gastric cancer's cells through the RAS/RAF/ERK signaling pathway. However, whether or not RASAL1 suppresses tumor growth in vivo remains to be determined. In the present study, we investigated the role of RASAL1 in gastric carcinogenesis by using an in vivo xenograft model.Methods:In vitro we have detected the expression of RASAL1 gene in eight gastric cancer cell lines include BGC-823 cell. It was found that the RASAL1 gene expression levels of BGC-823 and SGC-7901 gastric cancer cells were significantly decreased compared to the normal gastric epithelial cell. And considering the tumorigenicity in nude mice of gastric cancer cell, BGC-823 gastric cancer cell was chosen. A lentiviral RASAL1 expression vector was constructed and utilized to transfect the human gastric cancer cell line, BGC-823. RASAl1 expression levels were measured by quantitative real-time q-PCR and western blot analysis. Then,21 mice were randomly divided into 3 groups(7 mice each group); we established the nude mice xenograft model using BGC-823 cell line either with RASAL1 overexpression or normal. Tumor volume was measured and growth curve was observed regularly. RASAL1, extracellular signal-regulated protein kinase (ERK), phosphorylation of extracellular signal-regulated protein kinase (p-ERK) protein expression levels were measured by western blot analysis.Results:(1)Compared to BGC-823 cell lines transfected with pCDH-NC lentiviral vector and not transfected with lentiviral vector, the expression of RASAL1 mRNA and protein of BGC-823 cell lines transfected with pCDH-RASAL1 significantly increased. There was a statistically significant difference, The P value was less than 0.05. Which demonstrated RASAL1 overexpression gastric cell line was successfully constructed; (2) The BGC-823 gastric cancer cell lines were injected into themice in each group, and formed subcutaneous tumor a week later. Compared to BGC-823-NC group and BGC-823 group, both average tumor volume (176.90±50.74mm3) and weight (0.24±0.08g) of BGC-823-RASAL1 group had a significant reduction, There was a statistically significant difference. The P value was less than 0.05;(3) The RASAL1 and p-ERK protein expression levels of each group were different. The RASAL1 protein expression level in BGC-823-RASAL1 group was lower than control groups, and The p-ERK protein expression level in BGC-B23-RASAL1 group was higher than control groups, the difference was statistically significant, the P value was less than 0.05; And total ERK protein had no significant difference among the three groups.Conclusions:These findings demonstrated that overexpression of RASAL1 inhibits the growth of gastric cancer by inducing inactivation of RAS/RAF/ERK pathway in vivo. This study indicates that RASAL1 attenuates gastric carcinogenesis.