Stearoyl-CoA desaturase 1 (SCD1) facilitates the growth and anti-ferroptosis of gastric cancer cells and predicts poor prognosis of gastric cancer

Abstract

Cancer cells are characterized by metabolic alterations. Thereinto, Stearoyl-CoA Desaturase 1 (SCD1), an enzymatic node located in the conversion of saturated fatty acids into monounsaturated fatty acids (MUFAs), has been reported to accelerate the tumorigenesis of multiple cancers. However, its role in the metabolic process of gastric cancer remains largely unexplored. In this study, by in vitro, in vivo and in silico assessments, our results revealed that SCD1 exhibited the ability to promote tumor growth, migration and anti-ferroptosis of gastric cancer. The underlying mechanism might involve the alteration of cancer stemness and modulation of cell cycle-related proteins. Moreover, based on our findings, high expression of SCD1 might predict poor prognosis in gastric cancer patients. Our study provided new insights into the potential of SCD1 as a biomarker as well as a therapeutic target in the treatment of gastric cancer.

Keywords: SCD1; ferroptosis; gastric cancer; lipid metabolism; proliferation.

Figure 1

Expression level and prognostic value of SCD1 in various types of cancer. (A) SCD1 mRNA expression level in pan-cancer tissues and normal tissues. BLCA, bladder urothelial carcinoma; BRCA, breast invasive carcinoma; CESC, cervical squamous cell carcinoma and endocervical adenocarcinoma; CHOL, cholangio carcinoma; COAD, colon adenocarcinoma; ESCA, esophageal carcinoma; GBM, glioblastoma multiforme; HNSC, head and neck squamous cell carcinoma; KICH, kidney chromophobe; KIRC, kidney renal clear cell carcinoma; KIRP, kidney renal papillary cell carcinoma; LIHC, liver hepatocellular carcinoma; LUAD, lung adenocarcinoma; LUSC, lung squamous cell carcinoma; PAAD, pancreatic adenocarcinoma; PRAD, prostate adenocarcinoma; PCPG, pheochromocytoma and paraganglioma; READ, rectum adenocarcinoma; SARC, sarcoma; SKCM, skin cutaneous melanoma; THCA, thyroid carcinoma; THYM, thymoma; STAD, stomach adenocarcinoma; UCEC, uterine corpus endometrial carcinoma; (B) SCD1 mRNA expression were significantly overexpressed in gastric cancer tissues compared with peritumor tissues in TCGA database. (C, D) SCD1 mRNA expression were significantly overexpressed in gastric cancer tissues compared with normal ones in GSE13911 and GSE19826 database. (E) The mRNA expression level of SCD1 in different lymph node metastasis based on TCGA-STAD database. (F) The mRNA expression level of SCD1 in different AJCC stages based on TCGA-STAD database. (G) Overall survival of patients in SCD1-low expression group and SCD1-high expression group based on GEO database. (H) Post-progression survival of patients in SCD1-low expression group and SCD1-high expression group based on GEO database. (I) Progression-free survival of patients in SCD1-low expression group and SCD1-high expression group based on GEO database. The survival time of patients was compared between groups using the Mantel-Cox test. *, P <0.05; **, P <0.01; ***, P <0.001; ****, P <0.0001, respectively. (J) Overall survival of patients in SCD1-low expression group and SCD1-high expression group based on TCGA-STAD database. (K) Gastric cancer nomogram of overall survival for patients in TCGA-STAD database was examined by adding up of the points identified on the points scale for each characteristics. The total points existed on the bottom scales stand for the probability of 1-, 3- and 5- year survival. (L) Time-dependent area under the curve (AUC).

Figure 2

Bioinformatic analyses of SCD1. (A–C) Receiver operating characteristic (ROC) curve at 1, 3 and 5 years according to SCD1 gene expression in the TCGA-STAD database. (D–F) The calibration curve for predicting overall survival at 1-, 3- and 5-years in the TCGA-STAD database. (G) Representative images from gastric cancer tissue stained with SCD1, the scale bar, 100 μm and 50 μm, respectively. (H) Endoplasmic reticulum of gastric cancer cells were isolated, proteins were separated by SDS-PAGE and evaluated by immunoblots. (I) The alteration frequency of SCD1 were determined by using the cBioportal. (J) Screenshot of SCD1 mutation frequencies. (K) The Venn diagram illustrated the common correlated factors of SCD1 identified via cBioportal, Gepia and MEM analysis tools. (L) The correlations between SCD1 and correlated factors mRNA expression levels in human gastric cancer tissues (TCGA, n=375).

Figure 3

Oncogenic function of SCD1 in gastric cancer cells. (A) The KEGG pathways and GO terms participated by SCD1 and related factors with P value < 0.05. (B) The KEGG pathways and GO terms identified via gene set enrichment analysis of tissues with high and low SCD1 expression levels. (C) The proteins participated in “DNA replication”, “cell cycle”, “cell cycle G1-S phase transition” and “cyclin dependent protein serine threonine kinase regulator activity”, anti-ferroptosis markers as well as Wnt/β-catenin and Hippo signaling pathways were analyzed using western blotting with the indicated antibodies. GAPDH was used as the internal protein loading control. Each experiment was examined in triplicates. (D, E) SCD1 promoted proliferation of gastric cancer cells. (F–I) SCD1 promoted colony formation of gastric cancer cells. Each experiment was examined in triplicate. *, P <0.05; **, P <0.01; ***, P <0.001; ****, P <0.0001, respectively.

Figure 4

Oncogenic function of SCD1 in gastric cancer cells. (A–C) Gastric cancer cells were treated with 1 μM Erastin for 24 hours, then cell death was assessed using propidium iodide (PI), the bar plot represent quantification of PI-positive cells. Each experiment was conducted in triplicates. (D–F) C11-BODIPY staining of gastric cancer cells following treatment with 1 μM Erastin for 24 hours, the bar plot represent quantification of C11-BODIPY-positive cells. Each experiment was conducted in triplicates. (G, H) SCD1 ameliorated the migration ability of gastric cancer cells. (I, J) The metastatic related markers were analyzed by using western blotting with the indicated antibodies. (K, L) the cancer stemness related markers were analyzed by using western blotting with the indicated antibodies. GAPDH was used as the internal protein loading control. Each experiment was conducted in triplicates. *, P <0.05; **, P <0.01; ***, P <0.001; ****, P <0.0001, respectively.

Figure 5

Oncogenic activity of SCD1 in xenograft mice model. (A) Representative mice and tumor nodules in each group were shown. (B) Tumor volumes were analyzed (n = 5), results were shown as mean ± SEM (Student t test). (C) Tumor weights were calculated (n = 5), results were shown as mean ± SEM (Student t test). (D) Immunofluorescent staining of the indicated markers were performed. Scale bar, 50 μm. (E) the SCD1, Twist1 and Ki67 positive cells in the tumors were analyzed by using image J software, and results were shown as mean ± SEM (Student t test). (F) Representative mice and tumor nodules in each group were shown. (G) tumor volumes were analyzed (n = 3), results were shown as mean ± SEM (the analysis of variance test). (H) Tumor weights were calculated (n = 3), and results were shown as mean ± SEM (the analysis of variance test). (I) Mice were treated by SCD1 inhibitor A939572 or Vehicle i.p. All regimens were administered for twice a week. Body weight was measured weekly during the treatment. There was no obvious decrease in body weight when administration of A939572. *, P <0.05; **, P <0.01; ***, P <0.001; ****, P <0.0001; NS, no significance, respectively.