While there was no statistical difference in the incidence of carcinomas in the three groups, the increases in granulation tissue count, CD68-positive macrophages, CCL2, the alveolar epithelial cell PCNA index, HO-1, and hyperplasia in the D15 group compared with the D1.5 group was not reflected in the development of lung tumors in these groups. This evidence concerns the gene PCNA and carcinoma.