Gene expression analysis of p27, p21, and GADD45A. Quantitative real-time polymerase chain reaction (gray bars) and microarray-based (black bars) expression analyses of p27, p21, and GADD45A genes were carried out in MCF-7 and MDA-MB-231 cell lines treated with CTet 6.0 μM (left) and 12.0 μM (right) for 24 hours. For quantitative real-time polymerase chain reaction, GAPDH was used as a housekeeping gene. Data are shown as mean ± standard deviation. Asterisks indicate statistically significant values (P < 0.01). GADD45A, growth arrest and DNA-damage-inducible protein alpha; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.