THERMORESPONSIVE HYDROGEL INCREASES PROSTATIC ANTITUMORAL ACTIVITY OF Viscum album EXTRACT

INTRODUCTION AND OBJECTIVE: Viscum album L. (VA) extracts are widely used in complementary cancer therapy due to their cytotoxic, immunostimulatory, and anti-inflammatory properties. In the present work, the seasonal VA dry extracts effects of winter (VADWE) and summer (VADSE), as well as, the influence of delivery system (Pluronic hydrogel), were investigated for the first time, in in vitro human prostate cancer (PCa) cells. MATERIAL AND METHOD: The cytotoxicity of samples was evaluated in DU145, PC3, and LNCaP cell lines. The following analyses were performed: cytotoxicity by MTT; clonogenic growth; cell death mechanisms; activity of caspases by Caspase-Glo® assay kit; cell cycle progression and expression of regulating proteins by western blot. The chemical profile of the extracts including the flavonoid content and the presence of chemical markers was analyzed by UV spectrophotometer and thin-layer chromatography, respectively. RESULTS AND CONCLUSION: The summer hydrogel (VADSE-loaded hydrogel) exhibited the highest cytotoxicity among the samples analyzed. The IC₅₀ values after 24, 48, and 72 h of incubation were as follows: DU-145: 63, 42, 35 µg/mL; PC-3: 87, 44, 49 µg/mL; LNCaP: 262, 195.7, 119.5 µg/mL. The incubation with VADSE-loaded hydrogel at 50 μg/mL for 48h decreased DU-145 viability in 26% (p<0.0001) and an increased cell percentage undergoing late apoptosis (13%; p<0.0001) and necrosis (11%; p<0.001) was detected. In addition, summer hydrogel (50 μg/mL, for 24 h) showed a decrease in caspase 9 activity of 18% (p<0.01) and without effect on caspase 8 and 3. The same treatment for 48 h led to a cell cycle S phase arrest. Then, the cell cycle-regulating proteins were analyzed resulting in up-regulation of pAKT (+52%; p<0.04) and down-regulation of AKT (-42%; p<0.0001), Cyclin A  (-21%; p<0.03) and B (-42%; p<0.0007), CDK1 (-41%; p<0.03), CDK2 (-52%; p<0.0007), and no effect on p21 was registered when compared to untreated cells. In PC-3 cells, summer hydrogel (50 μg/mL, for 48 h) decreased viability in 16% (p<0.0001) and increased the cellular percentage on late apoptosis in 7% (p<0.01). Besides, the same treatment for 24 h increases the caspase 3/7(17%; p<0.01), 8 (14%; p<0.05), and 9 (20.6%; p<0.01) activity. In counterpart, the highest concentration of summer hydrogel (200 μg/mL; 48 h) was needed to promote 64% (p<0.0001) of LNCaP viability reduction besides a decrease in 10.5% (p<0.01) of cells under necrosis. Additionally, an increase in cell percentage under early apoptosis (35%; p<0.001) and late apoptosis (40%; p<0.001). In addition, the summer hydrogel promoted an increase of caspase 3/7 (26%; p<0.01) and 8 (27%; p<0.0001). Chemical analysis of the extracts showed the expected chemical profile. Our study highlights a novel VADSE-loaded thermosensitive hydrogel as a promising therapeutic option for the treatment of human prostate cancer.