CCND1 and keloid: In addition, application of rapamycin to monoculture keloid fibroblasts could downregulate the expression of cytoplasmic proliferating cell nuclear antigen (PCNA), cyclin D1, fibronectin, collagen, and alpha-smooth muscle actin (alpha-SMA) in a time- and dose-dependent manner, suggesting the antiproliferative effect of rapamycin in the treatment of keloid scars [4].