PTGS2 and neoplasm: For example, etoposide and cyclophosphamide given at low, long-term dosing to target normal cells that support tumor proliferation, such as endothelium, can produce substantial inhibition of tumor growth, even in tumors made highly resistant to these drugs.15,16,17 Similar effects can be observed using other inhibitors of endothelial cell function, including cyclooxygenase 2 inhibitors, peroxisome proliferator–activated receptor α agonists, and thalidomide.18,19,20