PCNA and lung cancer: According to the literature, following biomarkers are relevant in lung cancer: proliferation index KI 67, hypoxia-inducible factor- (HIF-) 1α, tumor suppressor protein p53, vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EGFR), proliferating cell nuclear antigen (PCNA), PD L1, and several cyclins [2–10].