Therapeutic Mechanisms of Vernonia amygdalina Delile in the Treatment of Prostate Cancer

Abstract

Prostate cancer patients have been suffering from limited treatment options due to late diagnosis, poor drug tolerance, and multi-drug resistance to almost all the current drug treatments. Therefore, it is important to seek a new alternative therapeutic medicine that can effectively prevent the disease and even eradicate the progression and metastasis of prostate cancer. Vernonia amygdalina Delile (VAD) is a common edible vegetable in Cameroon that has been used as a traditional medicine for some human diseases. However, to the best of our knowledge, no previous reports have explored its therapeutic efficacy against human prostate cancer. The objective of the present study was to assess the anticancer activities of VAD methanolic extracts in the prevention and treatment of prostate cancer using human androgen-independent prostate cancer (PC-3) cells as a test model. To achieve our objective, PC-3 cells were treated with various doses of VAD for 48 h. Data generated from the trypan blue test and MTT assay demonstrated that VAD extracts exhibited significant growth-inhibitory effects on PC-3 cells. Collectively, we established for the first time the antiproliferative effects of VAD on PC-3 cells, with an IC₅₀ value of about 196.6 µg/mL. Further experiments, including cell morphology, lipid peroxidation and comet assays, and apoptosis analysis showed that VAD caused growth-inhibitory effects on PC-3 cells through the induction of cell growth arrest, DNA damage, apoptosis, and necrosis in vitro and may provide protection from oxidative stress diseases as a result of its high antioxidant content. These results provide useful data on the anticancer activities of VAD for prostate cancer and demonstrate the novel possibilities of this medicinal plant for developing prostate cancer therapies.

Keywords: DNA damage; PC-3 cells; Vernonia amygdalina Delile; apoptosis; necrosis; oxidative stress.

Figure 1

Antiproliferative effect of Vernonia amygdalina Delile (VAD) on PC-3 cells. Growth inhibition of PC-3 cells treated with different doses of VAD for 48 h and measured by trypan blue test. Data are means ± SD from three independent determinations in triplicate.

Figure 2

Antiproliferative effect of Vernonia amygdalina Delile (VAD) on PC-3 cells. Growth inhibition of PC-3 cells treated with different doses of VAD for 48 h and measured by MTT assay as described in Materials and Methods section. Data are expressed as means ± SD (n = 3). * Significantly different from the control by ANOVA and Dunnett’s test; p < 0.05.

Figure 3

Morphological changes of PC-3 cells were observed under a microscope. The figure shows untreated cells (A-control) and cells treated with Vernonia amygdalina Delile (VAD) of 125 µg/mL (B); 250 µg/mL (C); and 500 µg/mL (D) for 48 h. Results were confirmed by repeating the experiment three times.

Figure 4

Malondialdehyde (MDA) standard curve (Left) and effects of Vernonia amygdalina Delile (VAD) extract on MDA level in PC-3 cells (Right). PC-3 cells were treated with various doses of VAD: 125, 250 and 500 µg/mL. MDA concentrations were determined as described in Materials and Methods section. Data are expressed as means ± SD (n = 3). * Significantly different from the control by ANOVA and Dunnett’s test; p < 0.05.

Figure 5

Representative SYBR Green comet assay images of untreated control (A) and Vernonia amygdalina Delile (VAD)-treated PC-3 cells at 125 µg/mL (B); 250 µg/mL (C); and 500 µg/mL (D). Cells observed in the treated images for each VAD dose exhibited an increase in DNA damage as VAD dose rose.

Figure 6

Representative dot plots showing the apoptotic and necrotic potential of Vernonia amygdalina Delile (VAD) in PC-3 cells upon 48 h of extract exposure. (A): Controls (untreated); (B): 125 µg/mL VAD; (C): 250 µg/mL VAD; (D): 500 µg/mL VAD. Quadrant 1: Live cells or annexin V- and PI-negative cells; 2: Early apoptotic or annexin V-positive cells; 3: Late apoptotic and necrotic or annexin V- and PI-positive cells; 4: Necrotic or PI-positive cells.