A recent in vivo study using colon cancer xenografts showed an association between nicotine and increased tumor size and vascularization that was attributable to an increase in the synthesis of COX-2 (Cyclooxygenase-2) prostaglandin E2, and VEGF (Vascular Endothelial Growth Factor) mediated by β-adrenergic receptors, particularly β2 receptors [9]. This evidence concerns the gene PTGS2 and malignant colon neoplasm.