PTGS2 and neoplasm: However, minimally invasive laparoscopic surgery using warm, humidified CO2 insufflation, rather than cold, dry CO2, reduces expression of cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF), and hypoxia-inducible factor 1α (HIF-1α), thus diminishing tumor cell implantation and proliferation (144–146).