PCNA staining revealed a significant decrease in tumor cell proliferation (the mean±SD PCNA scores were 88%±10.2% and 73%±14.7% in control tumors and 25%±10.2% and 15%±6.5% in WFA-treated tumors of SKLMS1 and HT1080 xenografts, respectively; P = 0.025 and P = 0.04). This evidence concerns the gene PCNA and neoplasm.