To determine whether angiogenesis and cell proliferation in the metastatic tumor cells in the lungs were affected by IFN-α, we used real-time PCR with human-specific primers to detect the expression of several angiogenic and proliferation-related factors that are prominently reduced in primary tumors, as reported in our previous study[14], including VEGF-A, PDGF-A, IL-6, and PCNA. The gene discussed is PCNA; the disease is neoplasm.