Dysregulation of apoptosis-regulating genes B-cell lymphoma 2 (BCL-2), CL2 associated X (BAX), and cysteinyl aspartate specific proteinase 3 and 9 (CASPASE-3, CASPASE-9) further promotes tumor cell survival, while nicotine addiction genes cholinergic receptor nicotinic beta 3 subunit (CHRNB3), dopamine receptor D2 (DRD2), catechol-O-methyltransferase (COMT), and dopamine beta-hydroxylase (DBH) reinforce dependency via dopaminergic pathways. Here, DRD2 is linked to nicotine dependence.