Conclusion
In summary, our data showed that BCAT1 was overexpressed in human NSCLCs. BCAT1 facilitated cell proliferation and invasion possibly through regulation of the Wnt signaling pathway.
Methods
Immunohistochemistry was used to examine the protein expression of BCAT1 in 107 cases of lung cancer tissues. Biological roles and potential mechanisms of BCAT1 were examined using MTT, colony formation assay, Matrigel invasion assay, Western blot, RNA-sequencing, and luciferase reporter assay.
Results
We found BCAT1 was upregulated in 60 of 107 lung cancer tissues and correlated with nodal metastasis, advanced stages and short overall survival. The Cancer Genome Atlas (TCGA) and ONCOMINE data analyses also indicated that BCAT1 was elevated in human NSCLC tissues. BCAT1 protein was higher in lung cancer cell lines than in normal bronchial epithelial cell line. BCAT1 overexpression increased the cell growth rate, colony numbers and invasion abilities in both BEAS-2B and H1299 cell lines, while BCAT1 siRNA decreased the cell proliferation rate, colony numbers, and inhibited invasion. RNA-sequencing (RNA-seq) and Gene Set Enrichment Analysis (GSEA) analyses indicated that BCAT1 overexpression activated Wnt/Myc signaling. Western blot revealed that BCAT1 increased protein expression of MMP7, cyclin D1, c-Myc, and decreased E-cadherin and p27 in the BEAS-2B and H1299 cell lines. Further experiments showed that BCAT1 overexpression elevated Wnt reporter luciferase activity and increased activate β-catenin protein while downregulating p-β-catenin protein expression. BCAT1 knockdown showed the opposite effects. TCGA data analysis suggested positive correlations between BCAT1 and c-Myc, cyclin D1, and MMP7 mRNA. Blockage of Wnt signaling using an inhibitor (ICG-001) downregulated c-Myc, cyclin D1, MMP7 expressions and abolished the upregulating effects of BCAT1 on these proteins.