SREBP2 contributes to cisplatin resistance in ovarian cancer cells

Abstract

This study is to investigate transcription factors involved in cisplatin resistance in ovarian cancer cells. The transcriptome of cisplatin resistant and sensitive A2780 epithelial ovarian cancer cells was obtained from GSE15372. Ovarian transcriptome data GSE62944 was downloaded from TCGA and applied for transcription regulatory network analysis. The analysis results were confirmed using quantitative polymerase chain reaction. The roles of SREBP2 in cisplatin-resistant cells were investigated by RNA inference and cell viability analysis. Transcription regulatory network analysis found that 12 transcription factors and their targets were involved in cisplatin resistant in A2780 cells. Among these factors, the targets of EZH2 and SREBP2 revealed by Transcriptional Regulatory Relationships Unraveled by Sentence-based Text mining were also enriched in differentially expressed genes between cisplatin resistant and cisplatin sensitive cells. Their targets were enriched mainly in cell cycle and cholesterol metabolic process, respectively. Bioinformatic analysis illustrated three known targets of SREBP2, namely LDLR, FDFT1, and HMGCR were increased in A2780-resistant cell lines. Additionally, the three genes and SREBP2 were also elevated in live cells after cisplatin treatment via quantitative polymerase chain reaction. Importantly, RNA inference of SREBP2 in A2780 cell line resulted in a decrease of cell viability after cisplatin treatment. SREBP2 played important roles in cisplatin resistance and cholesterol metabolic process might be a novel target for cancer therapy. Impact statement Transcriptome of cisplatin resistant and sensitive A2780 epithelial ovarian cancer cells was obtained from GSE15372 and TCGA. Twelve transcription factors and their targets were involved in cisplatin resistant. Among these factors, the targets of EZH2 and SREBP2 revealed by Transcriptional Regulatory Relationships Unraveled by Sentence-based Text mining were also enriched in differentially expressed genes. Their targets were enriched mainly in cell cycle and cholesterol metabolic process. Three targets of SREBP2, namely LDLR, FDFT1, and HMGCR were increased in A2780-resistant cell lines and were found elevated in live cells after cisplatin treatment via qPCR. RNAi of SREBP2 in A2780 cell line resulted in a decrease of cell viability after cisplatin treatment. SREBP2 played important roles in cisplatin resistance and might be a novel target for cancer therapy.

Keywords: Cisplatin resistance; cholesterol metabolic process; differentially expressed genes; sterol regulatory element binding protein 2; transcription factors; transcription regulatory inference.

Figure 1.

Identification of transcription factors involved in cisplatin resistance. TCGA ovarian transcriptome data from GSE62944 were applied for transcription regulatory network analysis. Differentially expressed genes between cisplatin resistant and sensitive cells were analyzed from GSE15372. The targets of 12 TFs were enriched in DEGs (adj. P < 0.05). (A color version of this figure is available in the online journal.)

Figure 2.

Targets of EZH2 and SREBP2 and their functions. The targets of EZH2 (a). The targets of SREBP2 (b). The protein–protein interaction (PPI) network of the targets of EZH2. Red nodes showed genes included in cell cycle biological process (c). The PPI network of the targets of SREBP2. Red nodes showed genes included in cholesterol metabolic process biological process. (A color version of this figure is available in the online journal.)

Figure 3.

Bioinformatic analysis showed the expressions of most differentially expressed targets of SREBP2 were increased. The 19 targets of SREBP2 were differentially expressed between cisplatin resistant and sensitive cells, and their expressions were elevated except STARD13 (a). The expressions of FDFT1 (b), HMGCR (c) and LDLR (d) were all increased in cisplatin-resistant cells. *P < 0.05, compared with cisplatin sensitivity. (A color version of this figure is available in the online journal.)

Figure 4.

SREBP2 and its dependent genes were increased in A2780 cells treated with cisplatin. The expressions of SREBP2 (a), LDLR (b), and FDFT1 (c) were significantly up-regulated in 8 μM or 10 μM cisplatin-treated cells compared with the untreated cells, while HMGCR (d) gene was increased in 2 μM or more cisplatin-treated cells. *P < 0.05 compared with the untreated cells.

Figure 5.

Knock down of SREBP2 increased cisplatin sensitivity in A2780 cells. RNAi decreased the expressions of SREBP2 (a) and FDFT1 (b) in A2780 cells (*P < 0.05, compared to the control siNC). SREBP2 RNAi decreased cell viability (c), while FDFT1 alone RNAi increased that (*P < 0.05, compared to the control siNC). SREBP2 siRNA (d) transfection resulted in a decrease of cell viability (*P < 0.05, compared with the control of 0 μM).