Effect of allicin treatment on the protein expression levels of cyclin D1, CDK4 and CDK6 in chondrocytes. (A) The protein expression levels of cyclin D1, CDK4 and CDK6 were analyzed using western blot analysis. β-actin was used as an internal control. The protein expression levels of (B) cyclin D1, (C) CDK4 and (D) CDK6 in allicin-treated and untreated cells. For the quantification of western blot analysis, data are presented as the average ± SD (error bars). *P < 0.05, significant vs. untreated cells.