VDR and skin neoplasm: A study showed that a few key players (e.g. retinoic acid receptor β (RARβ), peroxisome proliferator-activated receptor β and δ (PPARβ/δ), vitamin D receptor (VDR), glucocorticoid receptor (GR) and androgen receptor (AR) in the context of skin cancer) seem to be involved in both cancer aggressiveness and drug resistance.