Project description:Neuroblastoma is the most common extracranial solid childhood tumor with clinical manifestations ranging from benign tumors that spontaneously regress to highly aggressive metastatic disease. Unfortunately, there is no therapy known to be curative for high-risk neuroblastoma. The calcium-sensing receptor (CaSR) is a G protein-coupled receptor that senses plasmatic fluctuation in the extracellular concentration of calcium and plays a key role in maintaining calcium homeostasis. We have previously reported that this receptor exhibits tumor suppressor properties in neuroblastoma. The activation of CaSR with cinacalcet, a positive allosteric modulator of CaSR, reduces neuroblastoma tumor-growth by promoting differentiation, ER stress and apoptosis. However, these promising results came with an associated side effect, since cinacalcet exposure resulted in hypocalcemia. Based on the biased signaling shown by calcimimetics, we aimed to identify a new drug that might exert tumor-growth inhibition similar to cinacalcet without affecting plasma calcium levels. We identified a structurally different calcimimetic AC-265347 as a promising therapeutic agent for neuroblastoma, since it reduced tumor-growth by induction of differentiation, without affecting plasma calcium levels. Microarrays analysis suggested biased allosteric modulation of the CaSR signaling by both calcimimetics towards distinct intracellular pathways since no upregulation of genes involved in calcium signaling and ER stress were observed in PDX models exposed to AC-265347. Moreover, the most significant upregulated biological pathways promoted by AC-265347 were linked to RHO GTPases signaling. AC-265347 also up-regulated cancer testis antigens (CTAs), thus providing new opportunities for CTA-based immunotherapies. Taken together, this study helps to shed light about the importance of the biased allosteric modulation when targeting GPCRs in cancer. More importantly, the capacity of AC-265347 to promote differentiation of malignant neuroblastoma cells provides new opportunities, alone or in combination with other drugs, to control minimal residual disease and to prevent relapse in patients affected with neuroblastoma.

Project description:Calcium and 1,25-dihydroxyvitamin D3 (1,25D3), through the actions of their respective receptors, the Ca2+-sensing receptor (CaSR) and the vitamin D receptor (VDR), potentiate keratinocyte differentiation. VDR regulates epidermal keratinocyte proliferation and differentiation by modulating gene transcription, whereas the CaSR, a member of the family C G-protein coupled receptor, calcium mobilizes intracellular calcium and induces the formation of cell-cell junctions. 1,25D3 augments the sensitivity of the prodifferentiating actions of calcium by increasing the expression of CaSR. CaSR- and VDR-deficient keratinocytes share common characteristics such as abnormal intercellular adhesion and sphigolipid metabolism. Both CaSR and VDR are abundantly expressed in epidermal stem cell populations including CD34 expressing bulge keratinocytes in hair follicles and basal cells in interfollicular epidermis. To delineate the role of CaSR- and VDR-dependent pathways in regulating epidermal development and functions in physiological state, we generated conditional CaSR-null and VDR-null mice, where Casr and VDR gene was removed from keratinocytes. Keratinocyte-specific CaSR-null and VDR-null mice manifest distinct phenotypes. CaSR-null mice display defective epidermal permeability barrier function due to aberrant keratinocyte differentiation. VDR-null mice develop alopecia after completing the first hair follicle cycling. Concurrent ablation of CaSR and VDR genes in keratinocytes delays rate of wound repair and increases incidence of skin tumor formation to a greater extent than deletion of the CaSR or VDR alone, indicative of synergistic effects of calcium and 1,25D3 signaling. Gene expression profiles and subsequent pathway analysis on the epidermis derived from 5-day-old neonates revealed that ablation of CaSR or VDR increased expression of genes associated with cancer progression and metastasis. Deletion of VDR markedly inhibited signaling pathways that regulate hair development. Furthermore, concurrent ablation of CaSR and VDR significantly suppressed calcium, VDR, Wnt/b-catenin signaling, as well as epithelial adherence junction signaling to maintain appropriate keratinocyte adhesion. These results indicated the interplay of calcium/CaSR and 1,25D3/VDR signaling in keratinocyte proliferation and differentiation, and their importance in maintaining normal epidermal adhesion and functions.

Dataset Information

CaSR modulator in neuroblastoma model [human]

Publications

Cinacalcet inhibits neuroblastoma tumor growth and upregulates cancer-testis antigens.

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