The role of the mμ opioid receptor (MOR), which has been shown expressed in cancer cells such lung adenocarcinoma and breast cancer, has been postulated as a mechanism of cancer progression due its interactions with angiogenesis, epithelial-mesenchymal transition, and the mammalian target of rapamycin signaling pathways [24–26]. The gene discussed is OPRM1; the disease is lung adenocarcinoma.