TOP2A and lung cancer: Previous literature reported that RRM2 promoted tumorigenesis and progression of pancreatic cancer, lung cancer, gastric cancer, ovarian cancer, bladder cancer and other tumors [21–24], TOP2A gene encoded a DNA topoisomerase, it is an ATP-dependent synthetase and hydrolase that plays a key role in cells and plays an important role in many cellular biological processes, such as DNA replication, chromatin condensation, chromosome segregation, and chromosome structure retention.