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Additional file 1: Figure S1. (A-B) qRT-PCR was performed to detect the B4GALT1 mRNA expression after siRNA-mediated knockdown and plasmid-mediated overexpression in A549 and PC9 cells. (C) Western blot was performed to detect the B4GALT1 protein expression. (D) The protein expression levels of CDK4 and Cyclin D1 in control and ectopic B4GALT1-expressing A549 and PC9 cells were determined using western blotting analyses. * P < 0.05, ** P < 0.01. Figure S2. (A) The linear correlations between the B4GALT1 expression and the CD8+ T-cell expression in the TCGA-LUAD dataset. (B) Comparison of TIDE scores between the B4GALT1-high group and B4GALT1-low group. (C) Comparison of overall survival between CTL top (samples above average CTL values among all samples) and CTL bottom (samples below average CTL values among all samples) groups in patients with different B4GALT1 levels. The two-sided Wald test in the Cox-PH regression was applied to compute the association between the CTL level and overall survival, and samples were split by the best separation strategy according to the B4GALT1 expression coefficients in the Cox-PH regression model. ** P < 0.01. Figure S3. (A-B) The differential expression of CD274 in tumours with high expression of B4GALT1 and low expression of B4GALT1 in the CCLE mRNA dataset (A) and the differential expression of PD-L1 in tumours with high expression of B4GALT1 and low expression of B4GALT1 in the TCGA-protein dataset (B). RPKM: reads per kilobase per million mapped reads; RPPA: reverse phase protein array. (C) Representative immunohistochemical images (left panel) and the association between B4GALT1 and PD-L1 level in MPLC tumours (right panel). Scale bars, 200 μm. (D) qRT-PCR was performed to detect the B4galt1 mRNA expression after siRNA-mediated knockdown in LLC cells. (E-F) LLC cells were transfected with si-B4galt1 or pcDNA- B4galt1, and Cd274 mRNA and PD-L1 protein was analysed by qRT-PCR and western blotting analyses. (G) LLC cells cocultured with activated CD8+ T cells for 48 h were subjected to crystal violet staining and quantified at 570 nm. The ratio of LLC cells to T cells is 1:3. (H) Western blot analysis of PD-L1 expression in LLC cells with or without the knockdown or overexpression of B4galt1 followed by the treatment with CHX. (I) Western blot analysis of PD-L1 levels in B4galt1 knock-down cells, B4galt1 overexpression cells, and tunicamycin (TM) treated cells. * P < 0.05, ** P < 0.01, ****P

Additional file 2. Supplementary Figures.

Gastric cancer is one of the most common malignant gastrointestinal tumors whose morbidity and mortality account for the second and third place respectively in malignant tumors in China. As an important participant in tumor biology, the abnormal expression of long non-coding RNA (lncRNAs) in cancer cells is closely related to the occurrence and development of tumors and plays the role of oncogenes or tumor suppressor genes. In this study, we identified a novel lncRNA NFIA antisense RNA 1 (NFIA-AS1) and explored its role and clinical significance in gastric cancer. Real-time quantitative PCR was performed to detect the expression of NFIA-AS1 in tumor tissues and corresponding normal tissues from 42 pairs of gastric cancer samples. The lower expression of NFIA-AS1 was significantly associated with larger tumor size, lower histological grade, and advanced TNM stage. Kaplan-meier analysis showed that NFIA-AS1 expression could be used as an independent predictor of overall survival. We also demonstrated that overexpression of NFIA-AS1 significantly inhibited the proliferation of gastric cancer cells through affecting p16 levels. In conclusion, our results suggest that the lncRNA NFIA-AS1 may play the role of tumor suppressor gene, and serve as a biomarker for prognosis or progression of gastric cancer.