Transfection with Rho T19N induced significant reduction (p < 0.05) in cyclin D1 gene expression producing a 25.5% and a 33% reduction in normal and IPF derived lung fibroblasts respectively compared to cells treated with 5 ng/ml TGF-β1 alone, further supporting involvement of RhoA in cyclin D1 expression. The gene discussed is TGFB1; the disease is idiopathic pulmonary fibrosis.