CASR and squamous cell carcinoma: When the vitamin D receptor (VDR) is knocked out, mice are more susceptible to chemical or UV‐induced skin tumors (28, 29) and mice in which there is tissue‐selective double knock‐out of the VDR and the calcium‐sensing receptor (CaSR) in the epidermis exhibit spontaneous development of squamous cell carcinomas (30, 31).