A preliminary study of the effect of curcumin on the expression of p53 protein in a human multiple myeloma cell line

Abstract

Curcumin is an inexpensive, natural plant ingredient with protease inhibitor effects. The present study aimed to analyze the inhibitory effects of curcumin on the multiple myeloma (MM) RPMI 8226 cell line, and examine the underlying mechanism that promotes the apoptosis of RPMI 8226 cells. A growth curve was constructed in order to observe the relative growth velocity, and MTT was used to analyze the effect of different concentrations of curcumin on inhibiting the proliferation of the RPMI 8226 cells. The mRNA expression of the p53, Bax and MDM2 genes was detected using quantitative polymerase chain reaction. The expression of p53 protein in the MM RPMI 8226 cells following treatment with curcumin was detected by western blotting and ELISA. Curcumin inhibited the proliferation of the MM RPMI 8226 cells in a dose- and time-dependent manner. In the MM RPMI 8226 cells treated with curcumin, the expression of the p53 and Bax genes was upregulated, while the expression of the MDM2 gene was downregulated. p53 protein expression was higher in the curcumin experimental group compared with the control group. Subsequent to treatment with curcumin, the growth of the MM RPMI 8226 cell line was inhibited in a concentration- and time-dependent manner. In the MM RPMI 8226 cells treated with curcumin, p53 protein levels were upregulated, which suggested that curcumin may promote the apoptosis of MM cells by upregulating p53 protein expression.

Keywords: curcumin; multiple myeloma; p53 protein.

Figure 1

Growth curve representing the growth of cells treated with different concentrations of curcumin. The initial number of cells in each well was the same (10⁵/well). After 96 h, the number of cells in the wells treated with 0, 1, 2.5, 5, 7.5 and 10 μmol/l curcumin were >3×10⁶, ~2.5×10⁶, ~2×10⁶, ~1.5×10⁶, <1×10⁶ and <5×10⁵, respectively. The cells treated with 15, 20 and 40 μmol/l curcumin, however, barely grew.

Figure 2

Cells were treated with various concentrations of curcumin for 24, 48 and 72 h prior to the determination of cytotoxicity by an MTT cell proliferation assay. Each value is expressed as the mean ± standard deviation of six measurements.

Figure 3

p53, Bax and MDM2 gene fragment expression in the RPMI 8226 cells following treatment with different concentrations of curcumin for 48 h, as detected by polymerase chain reaction.

Figure 4

p53 protein expression detected by western blotting following treatment with different concentrations of curcumin for 48 h.

Figure 5

Measured optical density (OD) values of the standard samples were constructed as horizontal ordinates, and the concentrations of each diluted standard sample were contructed as vertical coordinates. The standard curve was drawn according to the OD values of the standard groups and the formula was then generated based on the standard curve.

Figure 6

p53 protein concentration of each sample was calculated according to the formula: p53 concentration = 2318.3ODvalue − 241.19.