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. 𝑃 < 0 . 0 5 versus nontreated control, 𝑃 < 0 . 0 1 versus nontreated control.