Epidemiological studies support the hypothesis that exposure to β2-AR antagonists may indeed reduce cancer progression and mortality, e.g., in melanoma (De Giorgi et al., 2011) and in breast cancer (Powe et al., 2010), although conflicting results have also been reported (Shah et al., 2011; Choi et al., 2014). This evidence concerns the gene ADRB2 and cancer.