Mitochondria are multifunctional organelles and mitochondrial activity is important for cellular proliferation and physiology. For example, the mitochondria play essential roles in cellular energy production via the tricarboxylic acid cycle coupled to oxidative phosphorylation, as well as Axitinib during apoptosis via reactive oxygen species generation and cytochrome c release. Several studies have indicated that mitochondrial dysfunction contributes to the development and progression of various human diseases, including cancer. A hallmark of tumor cells is altered metabolism supporting rapid cellular proliferation. Many metabolic intermediates that support cell growth are provided by the mitochondria ; consequently, the identification of proteins that regulate mitochondrial metabolic pathways is of great interest, and we sought to understand whether the VDR may modulate these pathways. In the present study, using our previously described model, we genetically silenced the receptor and examined the effects on cell growth, mitochondrial metabolism and biosynthetic pathways. The collected data provide evidence of a novel role of the VDR as a negative regulator of respiratory chain activity, and we highlight the repercussions for cellular anabolism and growth produced by the VDR on mitochondrial respiration. Based on our observations, we conclude that the VDR, by restraining mitochondrial respiratory activity, allows the cell to spare metabolic intermediates, which may be diverted from oxidative metabolism toward a biosynthetic fate, supporting cell growth. We validated the general role of the VDR as an enhancer of cellular proliferation extending our observations to several human cancer cell lines. The differentiating and antiproliferative action of vitamin D in vitro has been previously described in literature. Such effects are mediated by transcriptional control, which is preceded by BIBW2992 nuclear translocation and does not occur in vitamin D-stimulated HaCaT cells. HaCaT cells appear to be resistant to the nuclear antiproliferative effects of vitamin D, and accordingly, we found that vitamin D treatment did not alter the growth rate of HaCaT cells. Thus, HaCaT cells represent a model of resistance to the differentiating properties of vitamin D, and there is not any incongruity between the nuclear antiproliferative role of vitamin D described in literature and the proliferative effects exerted by VDR in our cell model. The results of our silencing experiments show that VDR in HaCaT cells enhances cell growth.