Vitamin D and DDX4 regulate the proliferation and invasion of ovarian cancer cells

Abstract

Ovarian cancer is one of the most commonly occurring types of cancer and one of the most common causes of cancer-associated mortality in women. Diagnosis of ovarian cancer at an early stage is difficult due to the lack of specific symptoms. In the present study, it is demonstrated that active vitamin D treatment prohibited the proliferation and invasion of ovarian cancer cells, and the expression level of a germ cell specific marker DEAD (Asp-Glu-Ala-Asp)-box helicase 4 (DDX4), which is overexpressed in ovarian cancer, was downregulated by active vitamin D treatment. Knockdown of DDX4 by siRNA could also suppress the invasive ability of ovarian cancer cells. Therefore, DDX4 may be considered as a diagnostic marker of ovarian cancer, and vitamin D may be a candidate drug for ovarian cancer therapy.

Keywords: Asp-Glu-Ala-Asp box polypeptide; SKOV3 and OVCAR3 cells; invasion; ovarian cancer; vitamin D.

Figure 1.

Active vitamin D inhibits the proliferation of SKOV3 and OVCAR3 cells. SKOV3 or OVCAR3 cells were treated with the indicated concentrations of active vitamin D, and proliferation was quantified relative to the untreated control cells. *P<0.05, compared with control. CTL, control; VitD, active vitamin D.

Figure 2.

Active vitamin D inhibits the invasive ability of SKOV3 and OVCAR3 cells. (A) SKOV3 cells and (B) OVCAR3 cells were treated with 100 µl/ml active vitamin D for 3 or 5 days in a transwell invasion assay. **P<0.01, ***P<0.001, compared with control. CTL, control; VitD, active vitamin D.

Figure 3.

Active vitamin D reduces the expression level of DDX4 in SKOV3 and OVCAR3 cells. SKOV3 or OVCAR3 cells were treated with 100 µl/ml active vitamin D. (A) Reverse transcription-quantitative polymerase chain reaction analysis, and (B) western blot analysis was performed to examine the expression level of DDX4. **P<0.01, ***P<0.001, compared with control. DDX4, DEAD-box helicase 4; CTL, control; VitD, vitamin D.

Figure 4.

DDX4 siRNA reduces the expression level of DDX4. SKOV3 or OVCAR3 cells were transfected with two independent siRNAs against DDX4, and the DDX4 mRNA level was examined by reverse transcription-quantitative polymerase chain reaction, relative to GADPH as an internal control. *P<0.05, compared with blank control group. DDX4, DEAD-box helicase 4; siRNA, small interfering RNA; NC, negative control.

Figure 5.

DDX4 knockdown inhibited the invasive ability of SKOV3 and OVCAR3 cells. (A) SKOV3 cells or (B) OVCAR3 cells were treated with siDDX4-121 for 3 or 5 days in a transwell assay. **P<0.01, ***P<0.001, compared with control. DDX4, DEAD-box helicase 4; siDDX4, small interfering RNA targeting DDX4.