Berberine downregulates HPV oncogene expression, increased p53, Rb levels and inhibit hTERT expression in cervical cancer cells. A, Effect of berberine on HPV16 and HPV18 mRNA expression. Northern blots (middle panels) of HPV16 positive SiHa cells and HPV18 positive HeLa cells incubated with indicated concentrations of berberine. Quantity and quality of total RNA (15 μg/lane) extracted was examined on agarose gel (upper panels). The membrane was rehybridized with β-actin-specific DNA probe as internal control to assess equal loading (lower panels). B, Effect of berberine on the expression of HPV E6 and E7 oncoproteins. Representative immunoblots of HPV16E6 &E7 and HPV18E6 &E7 in SiHa and HeLa cells respectively treated with berberine for indicated doses. β-actin was used as loading control. C, Effect of berberine on the expression of p53 and Rb proteins. HPV16 positive SiHa cells and HPV18-positive HeLa cells were treated with different concentration of berberine. The cells were harvested after 24 h to obtain whole cell extracts, which were analyzed for p53 and Rb expression by Western blotting. Equal sample loading was confirmed by determining the β-actin expression levels. D, Effect of berberine on the expression of hTERT. Immunoblots of cellular proteins isolated from SiHa and HeLa cells treated with berberine. β-actin was used as loading control. The abundance ratios to β-actin were analyzed by densitometry. The data are expressed as the mean ± SD of 3 independent experiments.