PCNA and cervical squamous intraepithelial neoplasia: Immunohistochemical investigation using monoclonal antibodies against PCNA, Ki-67 and BrdU showed strong reactivity and a great quantity of PCNA- and Ki-67-positive nuclei (marked with dark reddish-brown color) and moderate reactivity for BrdU in the gastric mucosa of animals treated with CIN for 14 days, when compared to control group, in which there was no reactivity for the three markers due to the destruction of the epithelial layer, as shown in Fig 4.