Vitamin D analogues exhibit antineoplastic activity in breast cancer patient-derived xenograft cells.

Despite advances in breast cancer (BC) treatment, its mortality remains high due to intrinsic or acquired resistance to therapy. Several ongoing efforts are being made to develop novel drugs to treat this pathology with the aim to overcome resistance, prolong patient survival and improve their quality of life. We have previously shown that the non-hypercalcemic vitamin D analogues EM1 and UVB1 display antitumor effects in preclinical studies employing conventional cell lines and animal models developed from these cells. In this work, we explored the antitumor effects of EM1 and UVB1 employing BC cells derived from patient-derived xenografts (PDXs), which are a powerful preclinical tool for testing new drugs. We demonstrated that the analogues reduced the viability of HER2-positive and Triple Negative BC-PDXs. Moreover, using an in vitro model of acquired resistance to Trastuzumab-emtansine, UVB1 displayed anti-proliferative actions under 2D and 3D culture conditions. It inhibited both formation and growth of established organoids. In addition, a direct correlation between UVB1 antitumor effects and VDR expression in PDXs was found. In conclusion, all the results reinforce the potential use of these vitamin D analogues as antitumor agents to treat HER2-positive and Triple Negative BC.

Structure-Activity Relationship Study of an Alkynylphosphonate and Vynilphosphonate Analogues of Calcitriol.

BACKGROUND: 1α,25-dihydroxy vitamin D3 (calcitriol) shows potent growth-inhibitory properties on different cancer cell lines, but its hypercalcemic effects have severely hampered its therapeutic application. Therefore, it is important to develop synthetic calcitriol analogues that retain or even increase its antitumoral effects and lack hypercalcemic activity. Based on previous evidence of the potent antitumor effects of the synthetic alkynylphosphonate EM1 analogue, we have now synthesized a derivative called SG. OBJECTIVE: The aim of the present work is to evaluate the calcemic activity and the antitumor effect of SG, comparing these effects with those exerted by calcitriol and with those previously published for EM1. In addition, we propose to analyze by in silico studies, the chemical structure-biological function relationship of these molecules. METHODS: We performed the synthesis of vinylphosphonate SG analogue; in vitro assays on different cancer cell lines; in vivo assays on mice; and in silico assays applying computational molecular modeling. RESULTS: The SG compound lacks hypercalcemic activity, similar to the parent compound EM1. However, the antitumor activity was blunted, as no antiproliferative or anti-migratory effects were observed. By in silico assays, we demonstrated that SG analogue has a lower affinity for the VDRligand- binding domain than the EM1 compound due to lack of interaction with the important residues His305 and His397. CONCLUSION: These results demonstrate that the chemical modification in the lateral side chain of the SG analogue affects the antitumoral activity observed previously for EM1 but does not affect the calcemic activity. These results contribute to the rational design and synthesis of novel calcitriol analogues.

Vitamin D receptor exhibits different pharmacodynamic features in tumoral and normal microenvironments: A molecular modeling study.

The vitamin D receptor (VDR) constitutes a promising therapeutic target for the treatment of cancer. Unfortunately, its natural agonist calcitriol does not have clinical utility due to its potential to induce hypercalcemic effects at the concentrations required to display antitumoral activity. For this reason, the search for new calcitriol analogues with adequate therapeutic profiles has been actively pursued by the scientific community. We have previously reported the obtaining and the biological activity evaluation of new calcitriol analogues by modification of its sidechain, which exhibited relevant antiproliferative and selectivity profiles against tumoral and normal cells. In this work we conducted molecular modeling studies (i.e. molecular docking, molecular dynamics, constant pH molecular dynamics (CpHMD) and free energy of binding analysis) to elucidate at an atomistic level the molecular basis related to the potential of the new calcitriol analogues to achieve selectivity between tumoral and normal cells. Two histidine residues (His305 and His397) were found to exhibit a particular tautomeric configuration that produces the observed bioactivity. Also, different acid-based properties were observed for His305 and His307 with His305 showing an increased acidity (pKa 5.2) compared to His397 (pKa 6.8) and to the typical histidine residue. This behavior favored the pharmacodynamic interaction of the calcitriol analogues exhibiting selectivity for tumoral cells when VDR was modeled at the more acidic tumoral environment (pH ≅ 6) compared to the case when VDR was modeled at pH 7.4 (normal cell environment). On the other hand, non-selective compounds, including calcitriol, exhibited a similar interaction pattern with VDR when the receptor was modeled at both pH conditions. The results presented constitute the first evidence on the properties of the VDR receptor in different physicochemical environments and thus represent a significant contribution to the in silico screening and design of new calcitriol analogues.

Antitumoral effects of the alkynylphosphonate analogue of calcitriol EM1 on glioblastoma multiforme cells.

Glioblastoma multiforme (GBM) is the worst and most common brain tumor, characterized by high proliferation and invasion rates. The current standard treatment is mainly based on chemoradiotherapy and this approach has slightly improved patient survival. Thus, novel strategies aimed at prolonging the survival and ensuring a better quality of life are necessary. In the present work, we investigated the antitumoral effect of the novel analogue of calcitriol EM1 on GBM cells employing in vitro, in silico, and in vivo assays. In vitro, we demonstrated that EM1 treatment selectively decreases the viability of murine and human tumor cells without affecting that of normal human astrocytes. The analysis of the mechanisms showed that EM1 produces cell cycle arrest in the T98G cell line, which is accompanied by an increase in p21, p27, p57 protein levels and a decrease in cyclin D1, p-Akt-S473, p-ERK1/2 and c-Jun expression. Moreover, EM1 treatment also exerts in GBM cells anti-migratory effects and decreases their invasive capacity by a reduction in MMP-9 proteolytic activity. In silico, we demonstrated that EM1 is able to bind to the vitamin D receptor with greater affinity than calcitriol. Finally, we showed that EM1 treatment of nude mice administered at 50ug/kg body weight during 21days neither induces hypercalcemia nor toxicity effects. In conclusion, all the results indicate the potential of EM1 analogue as a promising therapeutic alternative for GBM treatment.

The alkynylphosphonate analogue of calcitriol EM1 has potent anti-metastatic effects in breast cancer.

The active form of vitamin D3, calcitriol, plays a major role in maintaining calcium/phosphate homeostasis. In addition, it is a potent antiproliferative and prodifferentiating agent. However, when effective antitumor doses of calcitriol are employed, hypercalcemic effects are observed, thus precluding its therapeutic application. To overcome this problem, structural analogues have been designed with the aim at retaining or even increasing the antitumor effects while decreasing its calcemic activity. This report shows the biological evaluation of an alkynylphosphonate vitamin D less-calcemic analogue in a murine model of breast cancer. We demonstrate that this compound has potent anti-metastatic effects through its action over cellular migration and invasion likely mediated through the up-regulation of E-cadherin expression. Based on the current in vitro and in vivo results, EM1 is a promising candidate as a therapeutic agent in breast cancer.

Novel alkynylphosphonate analogue of calcitriol with potent antiproliferative effects in cancer cells and lack of calcemic activity.

Here, we describe the design and synthesis of diethyl [(5Z,7E)-(1S,3R)-1,3-dihydroxy-9,10-secochola-5,7,10(19)-trien-23-in-24-yl] phosphonate (compound 10), which combines the low calcemic properties of phosphonates with the decreased metabolic inactivation due to the presence of a triple bond in C-24 and studied its in vitro effects on several cancer cell lines and its in vivo effects on blood calcium levels. We demonstrate that this compound is a potent antiproliferative vitamin D analogue, showing lack of calcemic effects in vivo.