Figure 4: Effect of cucurbitacin B on p21 gene expression. MCF7:5C, MDA-MB-231, and SKBR-3 were incubated for 48 hr with the specified concentrations of cucurbitacin B, and RNA was extracted for real-time PCR to quantitate the expression level of p21. Relative expression levels of p21 mRNA at indicated concentration. Results shown are the average of three independent experiments. versus nontreated control, versus nontreated control.