VDR and non-Hodgkin lymphoma: A possible mechanism underlying the role of vitamin D in the incidence of NHL is explained by the expression of vitamin D receptors and 1α-hydrolase, an enzyme that converts the circulating form of vitamin D (25(OH)D) into the bioactive metabolite (1,25-dihydroxyvitamin D), in activated B-and T-lymphocytes, and thus by the autocrine and paracrine role of vitamin D in regulating cell proliferation as well as inducing apoptosis and differentiation [44–47].