hERG1 is involved in the pathophysiological process and inhibited by berberine in SKOV3 cells

Abstract

The human ether-a-go-go-related potassium channel 1 (hERG1) is a functional component of the voltage-gated Kv11.1 potassium channel, which is commonly described as a crucial factor in the tumorigenesis of a variety of tumors. Ovarian cancer is one of the most severe types of cancer, with an extremely poor prognosis. Advances have been made in recent years; however, drug resistance and tumor recurrence remain critical issues underlying satisfactory treatment outcomes. Therefore, more effective antitumor agents with low levels of drug resistance for ovarian cancer treatment are urgently required in clinical practice. In the present study, hERG1 mRNA expression in ovarian tumor tissues and cell lines were measured by reverse transcription-quantitative polymerase chain reaction. Immunohistochemistry and western blotting were used to assess the expression levels of hERG1 protein. Cell proliferation, migration and invasion were assessed by Cell Counting Kit-8 assay and Transwell assay. A tumor xenograft assay was used to determine the growth of tumors in vivo. It was demonstrated that the expression levels of hERG1 were significantly elevated in ovarian cancer tissues and expressed in ovarian cancer cell lines, particularly in SKOV3 cells. Abnormal hERG1 expression was significantly associated with the proliferation, migration and invasion abilities of ovarian cancer. In addition, berberine (BBR) may be used as a potential drug in the treatment of ovarian cancer, possibly due to its inhibitory effects on the hERG1 channels. In conclusion, the present study demonstrated that hERG1 may be a potential therapeutic target in the treatment of ovarian cancer and provided novel insights into the mechanism underlying the antitumor effects of BBR in ovarian cancer.

Keywords: berberine; human ether-a-go-go-related potassium channel 1; invasion; migration; ovarian cancer; proliferation.

Figure 1.

Expression patterns of hERG1 in ovarian cancer tissues and cell lines. (A) Expression levels of hERG1 analyzed by immunohistochemistry (magnification, ×400). (B) Reverse transcription-quantitative polymerase chain reaction and (C) western blot analysis of hERG1 expression in ovarian cancer and matched adjacent non-tumor tissues (n=28). (D) Relative mRNA and (E) protein expression levels of hERG1 in various ovarian cancer cell lines (n=3). *P<0.05. hERG1, human ether-a-go-go-related potassium channel 1.

Figure 2.

BBR inhibits cell proliferation and hERG1expression in SKOV3 cells. (A) BBR (10, 30, 50 and 100 µM) inhibited the growth of SKOV3 cells in a time- and dose-dependent manner. Proliferation of cells treated with indicated doses of BBR for 24, 48 and 72 h was assessed using a Cell Counting kit-8 assay. *P<0.05 vs. 0 µM. (B) BBR inhibited the expression of hERG1 mRNA in a dose-dependent manner at 48 h. *P<0.05 vs. 0 µM. (C) BBR inhibited the expression of hERG1 protein in a dose-dependent manner at 48 h. (D) Quantification of hERG1 protein expression levels. (n=3). *P<0.05 vs. 0 µM. BBR, berberine; hERG1, human ether-a-go-go-related potassium channel 1.

Figure 3.

Knockdown of hERG1 in SKOV3 cells. (A) Knockdown of hERG1 by transfection with sh-hERG plasmid significantly reduced the mRNA expression levels of hERG1 in SKOV3 cells compared with the control group. (B) Knockdown of hERG1 gene by sh-hERG plasmid significantly reduced the protein expression of hERG1 compared with the control group in SKOV3 cells (n=3). *P<0.05, **P<0.01 vs. blank control. hERG1, human ether-a-go-go-related potassium channel 1; sh, short hairpin RNA.

Figure 4.

hERG1 is involved in the pathophysiological processes of SKOV3 cells. (A) Knockdown of hERG1 significantly reduced the cell proliferation activity in SKOV3 cells compared with in control cells. BBR at a concentration of 10 µM was used as a positive control. Quantification of the (B) migration and (C) invasion abilities of SKOV3 cells in different treatment groups. Images (magnification, ×200) represent the (D) migrating cells and (E) invading cells in the Transwell and Matrigel invasion assays, respectively. n=3. *P<0.05, **P<0.01 vs. control. BBR, berberine; hERG1, human ether-a-go-go-related potassium channel 1; IC₅₀, half-maximal inhibitory concentration; sh, short hairpin RNA; OD, optical density.

Figure 5.

Knockdown of hERG1 inhibits ovarian tumor growth in vivo. (A) When tumors reached 100 mm³ in ~1 week, BBR treatment was initiated. Mice in the control group were injected with saline. (B) Body weight of mice with xenografts. No notable difference was detected in the body weight of mice among the four groups. (C) Weight of tumor samples from nude mice. (D) Macroscopic appearance of the tumors at 4 weeks after drug administration. n=3. *P<0.05, **P<0.01 vs. control. BBR, berberine; hERG1, human ether-a-go-go-related potassium channel 1; sh, short hairpin RNA.