Vitamin D receptor (VDR) mediates many genomic and non-genomic effects of vitamin D. Recently, the mitochondrial effects of vitamin D have been characterized in many cell types. In this article, we investigated the importance of VDR not only in mitochondrial activity and integrity but also in cell health. The silencing of the receptor in different healthy, non-transformed, and cancer cells initially decreased cell growth and modulated the cell cycle. We demonstrated that, in silenced cells, the increased respiratory activity was associated with elevated reactive oxygen species (ROS) production. In the long run, the absence of the receptor caused impairment of mitochondrial integrity and, finally, cell death. Our data reveal that VDR plays a central role in protecting cells from excessive respiration and production of ROS that leads to cell damage. Because we confirmed our observations in different models of both normal and cancer cells, we conclude that VDR is essential for the health of human tissues.

Vitamin D and TGF-β exert opposite effects on epithelial-mesenchymal EMT transition. Here we report a novel mechanism of action of TGF-β that promotes the counteracting activity of vitamin D; in two models of human epithelial-mesenchymal EMT transition we demonstrated for the first time that TGF-β strongly induced the expression of vitamin D receptor (VDR) and that 1,25(OH) 2 D 3 was able to contrast the TGF-β-driven EMT transition by transcriptional modulation. In human bronchial epithelial cells the effects of TGF-β on EMT transition markers (E-Cadherin expression and cell motility) were reversed by pre-treatment and co-treatment with 1,25(OH) 2 D 3, but not when the hormone was given later. Silencing experiments demonstrated that the inhibition of TGF-β activity was VDR-dependent. 1,25(OH) 2 D 3 abrogated the mitochondrial stimulation triggered by TGF-β. In fact we showed that 1,25(OH) 2 D 3 repressed the transcriptional induction of respiratory complex, limited the enhanced mitochondrial membrane potential and restrained the increased levels of mitochondrial ATP; 1,25(OH) 2 D 3 also decreased the production of reactive oxygen species promoted by TGF-β. Overall, our study suggests that the overexpression and activity of VDR may be a regulatory response to TGF-β signaling that could be exploited in clinical protocols, unraveling the therapeutic potentiality of 1,25(OH) 2 D 3 in the prevention of cancer metastasis.

In this study, we investigated whether the relative abundance of glutamate and glutamine in human proteins reflects the availability of these amino acids (AAs) dictated by the cellular context. In particular, because hypoxia increases the conversion of glutamate to glutamine, we hypothesized that the ratio glutamate/glutamine could be related to tissue oxygenation. By histological, biochemical and genetic evaluation, we identified proteins expressed selectively by distinct cellular populations that are exposed in the same tissue to high or low oxygenation, or proteins codified by different chromosomal loci. Our biochemical assessment was implemented by software tools that calculated the absolute and the relative frequencies of all AAs contained in the proteins. Moreover, an agglomerative hierarchical cluster analysis was performed. In the skin model that has a strictly local metabolism, we demonstrated that the ratio glutamate/glutamine of the selected proteins was directly proportional to oxygenation. Accordingly, the proteins codified by the epidermal differentiation complex in the region 1q21.3 and by the lipase clustering region 10q23.31 showed a significantly lower ratio glutamate/glutamine compared with the nearby regions of the same chromosome. Overall, our results demonstrate that the estimation of glutamate/glutamine ratio can give information on tissue oxygenation and could be exploited as marker of hypoxia, a condition common to several pathologies.

The inflammatory cytokine TGFβ is both a tumor suppressor during cancer initiation and a promoter of metastasis along cancer progression. Inflammation and cancer are strictly linked, and cancer onset often correlates with the insufficiency of vitamin D, known for its anti-inflammatory properties. In this study, we investigated the interplay between TGFβ and vitamin D in two models of human pancreatic cancer, and we analyzed the metabolic effects of a prolonged TGFβ treatment mimicking the inflammatory environment of pancreatic cancer in vivo. We confirmed the induction of the vitamin D receptor previously described in epithelial cells, but the inhibitory effects of vitamin D on epithelial–mesenchymal transition (EMT) were lost when the hormone was given after a long treatment with TGFβ. Moreover, we detected an ROS-mediated toxicity of the acute treatment with TGFβ, whereas a chronic exposure to low doses had a protumorigenic effect. In fact, it boosted the mitochondrial respiration and cancer cell migration without ROS production and cytotoxicity. Our observations shed some light on the multifaceted role of TGFβ in tumor progression, revealing that a sustained exposure to TGFβ at low doses results in an irreversibly increased EMT associated with a metabolic modulation which favors the formation of metastasis.

Notwithstanding the huge amount of detailed information available in protein databases, it is not possible to automatically download a list of proteins ordered by the position of their codifying gene. This order becomes crucial when analyzing common features of proteins produced by loci or other specific regions of human chromosomes. In this study, we developed a new procedure that interrogates two human databases (genomic and protein) and produces a novel dataset of ordered proteins following the mapping of the corresponding genes. We validated and implemented the procedure to create a user-friendly web application. This novel data mining was used to evaluate the distribution of critical amino acid content in proteins codified by a human chromosome. For this purpose, we designed a new methodological approach called chromosome walking, which scanned the whole chromosome and found the regions producing proteins enriched in a selected amino acid. As an example of biomedical application, we investigated the human chromosome 15, which contains the locus DYX1 linked to developmental dyslexia, and we found three additional putative gene clusters whose expression could be driven by the environmental availability of glutamate. The novel data mining procedure and analysis could be exploited in the study of several human pathologies.