Indeed, pharmacological phase I clinical studies involving subjects affected with cancer have demonstrated that therapeutic calcitriol may reach peak blood levels of 3–16 nM [22, 23] and herein, with the exception of the cell line SUM-229PE, the EC50 of calcitriol upon CAMP gene expression values ranged between 2.13 and 17.1 nM. This evidence concerns the gene CAMP and cancer.