Sterol regulatory element binding transcription factor 1 promotes proliferation and migration in head and neck squamous cell carcinoma

Abstract

Background: Sterol-regulatory element-binding protein 1 (SREBP1) is a transcription factor involved in lipid metabolism that is encoded by sterol regulatory element binding transcription factor 1(SREBF1). SREBP1 overexpression is associated with the progression of several human tumors; however, the role of SREBP1 in head and neck squamous cell carcinoma (HNSC) remains unclear.

Methods: SREBF1 expression in pan-cancer was analyzed using the Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) data, and the association between SREBF1 expression and clinical characteristics of HNSC patients was examined using the UALCAN database. Enrichment analysis of SREBF1-related genes was performed using the Cluster Profiler R package. TCGA database was used to investigate the relationship between immune cell infiltration and SREBF1 expression. CCK-8, flow cytometry, and wound healing assays were performed to investigate the effect of SREBF1 knockdown on the proliferation and migration of HNSC cells.

Results: SREBF1 was significantly upregulated in several tumor tissues, including HNSC, and SREBF1 overexpression was positively correlated with sample type, cancer stage, tumor grade, and lymph node stage in HNSC patients. Gene enrichment analysis revealed that SREBF1 is associated with DNA replication and homologous recombination. SREBF1 upregulation was positively correlated with the infiltration of cytotoxic cells, B cells, T cells, T helper cells, and NK CD56 bright cells in HNSC. Knockdown of SREBF1 inhibited the proliferation and migration of HNSC cells (Hep2 and TU212) and induced apoptosis by downregulating the expression of steroidogenic acute regulatory protein-related lipid transfer 4 (STARD4).

Conclusions: SREBF1 may promote HNSC proliferation, migration and inhibit apoptosis by upregulating STARD4 and affecting the level of immune cell infiltration.

Keywords: Cell proliferation; HNSC; Immune infiltration; Migration; SREBF1.

Figure 1. SREBF1 expression in human pan-cancers.

(A) TCGA and GTEx databases provide information on SREBF1 expression in tumors and adjacent normal tissues, HNSC (Normal = 44, Tumor = 520). (B–C) Expression of SREBF1 and STARD4 in adjacent normal tissues and tumors in HNSC(Normal = 44, Tumor = 502) from unpaired samples in TCGA. (D–E) Expression of SREBF1and STARD4 in tumor and adjacent normal tissues in HNSC (Normal = 43, Tumor = 43) from paired samples in TCGA. TPM (transcripts per million reads), Data are shown as the mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001.

Figure 2. Correlation of SREBF1 and STARD4 mRNA expression with clinicopathological parameters in HNSC patients from the UALCAN database.

(A+B) Type of sample (normal/primary tumor). (C+D) Cancer stage (stage 1, 2, 3, and 4). (E+F) Lymph node stage (N0, 1, 2, and 3). (G+H) Tumor grade (Grades 1, 2, 3, and 4). N, normal; P, primary tumor; S1, stage 1; S2, stage 2; S3, stage 3; S4, stage 4.G1, Grade1; G2, Grade2; G3, Grade3; G4, Grade4.

Figure 3. Analysis of SREBF1-related genes.

The top 50 genes positively associated with SREBF1 expression are shown in the heat map. The data were normalized by the Z-score normalization method.

Figure 4. Enrichment analysis of SREBF1-related genes in HNSC.

(A) KEGG pathways of genes significantly associated with SREBF1. (B–D) Gene ontology terms are significantly associated with SREBF1 [including biological processes (B), cell components (C), and molecular function (D)].

Figure 5. SREBF1 expression and immune cell infiltration in HNSC are correlated.

(A) Comparison of immune cell infiltration levels between SREBF1 differentially expressed groups in TCGA cohort of HNSC. (B) Correlation between SREBF1 and immune cell infiltration levels; red represents a positive correlation, green represents a negative correlation, and color shades represent the strength of the correlation. The data are presented as the mean ± standard deviation. *P < 0.05, **P < 0.01, ***P < 0.001. ns, not significant.

Figure 6. Knockdown of SREBF1 inhibited the proliferation and migration of HNSC cells.

(A) Expression levels of SREBF1 mRNA and STARD4 mRNA were measured in HNSC cells by RT-qPCR. (B) SREBF1 was knocked down by RNA interference, and the levels of SREBF1 and STARD were assessed by RT-qPCR. (C) Western blot analysis of SREBF1 and STARD4 levels. (D–G) CCK-8 assay and flow cytometric assessment were used to detect HNSC cell growth. (H) A wound-healing assay was used to detect the capacity of HNSC cells to migrate (original magnification × 100). The data are presented as the mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.