Inhibition of SENP5 by Cucurbitacin B Suppresses Cell Growth and Promotes Apoptosis in Osteosarcoma Cells

Abstract

Purpose: To investigate the effect of cucurbitacin B on the expression of SUMO-specific proteases (SENP5).Methods: Effect of cucurbitacin B (10-50 mg/mL) on viability of U2OS and Saos-2 cells was determined in a plate reader by recording absorbance at 570 nm. In Western blot analysis, bicinconinic acid (BCA) method was used to determine protein concentration. Flow cytometry was employed to measure DNA content.Results: Ccucurbitacin B treatment inhibits the expression of SENP5 in U2OS and Saos-2 osteosarcoma cells in a dose- and time-dependent manner. Significant inhibition (p = 0.005) of SENP5 expression was observed at 50 mg/ml from day 10, reaching a maximum on day 20. It also induced a significant decrease (p = 0.005) in mRNA and protein levels of SENP5. The decrease in mRNA and protein levels of SENP5 led to decrease in proliferation of U2OS and Saos-2 cells. The 48 h cell cultures containing 50 mg of cucurbitacin B caused induction of apoptosis in 54.72 ± 5.42 % of the total cell population in U2OS cells. Similarly, in Saos-2 cells, exposure to 50 mg/mL cucurbitacin B increased apoptotic rate from 9.86 ± 8.89 % for 10 mg/mL to 48.54 ± 14.5 % with 50 mg/mL of cucurbitacin B.Conclusion: Cucurbitacin B is a potential therapeutic strategy for the treatment of aggressive malignancy in osteosarcoma.Keywords: Cucurbitacin B, Osteosarcoma, SUMO-specific proteases, Cell proliferation, Apoptosis, Malignancy