Our results also support the clinical analyses, in which carriers of more active variants of the HO-1 promoter were more frequent among healthy subjects than among patients suffering from oral squamous cell carcinoma in betel chewers, lung adenocarcinoma in heavy smokers, and breast carcinoma in women subjected to iron supplementation [27,28,32–35]. The gene discussed is HMOX1; the disease is oral cavity squamous cell carcinoma.