ADRB2 and neoplasm: Depending on the immunoreactivity of beta 2 adrenergic receptors, we also observed a positive correlation between the increase in immunoreactivity for these receptors and the tumor proliferation index (r = 0.5159, 95% confidence interval 0.3590 to 0.6445, p < 0.0001, Figure 6B), thus suggesting a link between these receptors and the degree of tumor proliferation.