Vitamin D Analogs Regulate the Vitamin D System and Cell Viability in Ovarian Cancer Cells

Background: Ovarian cancer (OC) is one of the most lethal cancers in women. The active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25D3, calcitriol) has anticancer activity in several cancers, including ovarian cancer, but the required pharmacological doses may cause hypercalcemia. We hypothesized that newly developed, low calcemic, vitamin D analogs (an1,25Ds) may be used as anticancer agents instead of calcitriol in ovarian cancer cells. Methods: We used two patient-derived high-grade serous ovarian cancer (HGSOC) cell lines with low (13781) and high (14433) mRNA expression levels of the gene encoding 1,25-dihydroxyvitamin D3 24-hydroxylase CYP24A1, one of the main target genes of calcitriol. We tested the effect of calcitriol and four structurally related series of an1,25Ds (PRI-1906, PRI-1907, PRI-5201, PRI-5202) on cell number, viability, the expression of CYP24A1, and the vitamin D receptor (VDR). Results: CYP24A1 mRNA expression increased in a concentration-dependent manner after treatment with all compounds. In both cell lines, after 4 h, PRI-5202 was the most potent analog (in 13781 cells: EC50 = 2.98 ± 1.10 nmol/L, in 14433 cells: EC50 = 0.92 ± 0.20 nmol/L), while PRI-1907 was the least active one (in 13781 cells: EC50 = n/d, in 14433 cells: EC50 = n/d). This difference among the analogs disappeared after 5 days of treatment. The 13781 cells were more sensitive to the an1,25Ds compared with 14433 cells. The an1,25Ds increased nuclear VDR levels and reduced cell viability, but only in the 13781 cell line. Conclusions: The an1,25Ds had different potencies in the HGSOC cell lines and their efficacy in increasing CYP24A1 expression was cell line- and chemical structure-dependent. Therefore, choosing sensitive cancer cell lines and further optimization of the analogs’ structure might lead to new treatment options against ovarian cancer.

Convergent Total Synthesis of (+)-Calcipotriol: A Scalable, Modular Approach to Vitamin D Analogs

Vitamin D is a group of seco-steroids with diverse bioactivities. An enormous amount of effort was expended by medicinal chemists to search for Vitamin D analogs that could exhibit pro-differentiating and antiproliferative effects on normal and cancer cells as well as immunomodulatory effects without causing hypercalcemia. A convergent approach for the total synthesis of calcipotriol (brand name: Dovonex), a proven Vitamin D analog used for the treatment of psoriasis, and medicinally relevant synthetic analogs is described. Given the rich synthetic history of the Vitamin D family, a complete novel approach towards both the A-ring and CD-ring is reported. From a retrosynthetic standpoint, hidden symmetry within the decorated A-ring is disclosed, which allowed for scalable quantities of this advanced intermediate. In addition, a radical retrosynthetic approach is described, which highlights an electrochemical reductive coupling as well as an intramolecular hydrogen atom transfer (HAT)-Giese addition to establish the 6,5-trans-carbon skeleton found in the Vitamin D family. Lastly, a late-stage decarboxylative cross-coupling approach allowed for the facile preparation of various C20-arylated derivatives which show promising biological activity in an early bioassay.

Non-classical Vitamin D Actions for Renal Protection

Chronic Kidney Disease (CKD), a disorder that affects 11% of the world's population, is characterized by an acceleration in skeletal, immune, renal, and cardiovascular aging that increases the risk of cardiovascular mortality by 10- to 20-fold, compared to that in individuals with normal renal function. For more than two decades, the progressive impairment in renal capacity to maintain normal circulating levels of the hormonal form of vitamin D (1,25-dihydroxyvitamin D or calcitriol) was considered the main contributor to the reduced survival of CKD patients. Accordingly, calcitriol administration was the treatment of choice to attenuate the progression of secondary hyperparathyroidism (SHPT) and its adverse impact on bone health and vascular calcification. The development of calcitriol analogs, designed to mitigate the resistance to calcitriol suppression of PTH associated with CKD progression, demonstrated survival benefits unrelated to the control of SHPT or skeletal health. The exhaustive search for the pathophysiology behind survival benefits associated with active vitamin D analogs has identified novel anti-inflammatory, anti-hypertensive, anti-aging actions of the vitamin D endocrine system. A major paradigm shift regarding the use of calcitriol or active vitamin D analogs to improve survival in CKD patients emerged upon demonstration of a high prevalence of vitamin D (not calcitriol) deficiency at all stages of CKD and, more significantly, that maintaining serum levels of the calcitriol precursor, 25(OH)vitamin D, above 23 ng/ml delayed CKD progression. The cause of vitamin D deficiency in CKD, however, is unclear since vitamin D bioactivation to 25(OH)D occurs mostly at the liver. Importantly, neither calcitriol nor its analogs can correct vitamin D deficiency. The goals of this chapter are to present our current understanding of the pathogenesis of vitamin D deficiency in CKD and of the causal link between defective vitamin D bioactivation to calcitriol and the onset of molecular pathways that promote CKD progression independently of the degree of SHPT. An understanding of these mechanisms will highlight the need for identification of novel sensitive biomarkers to assess the efficacy of interventions with vitamin D and/or calcitriol(analogs) to ameliorate CKD progression in a PTH-independent manner.

Effects of Hypocalcemic Vitamin D Analogs in the Expression of DNA Damage Induced in Minilungs from Hescs: Implications for Lung Fibrosis

BackgroundIn our previous work, we evaluated the therapeutic effects of 1α,25-Dihydroxyvitamin D3, the biologically active form of vitamin D, in the context of bleomycin-induced lung fibrosis. Contrary to the expected, vitamin D supplementation increased DNA damage expression and cellular senescence in alveolar epithelial type II cells and aggravated the overall lung pathology induced in mice by bleomycin. These effects were probably due to an alteration of the cellular DNA double-strand breaks repair capability. In the present work we have evaluated the effects of two hypocalcemic vitamin D analogs (calcipotriol and paricalcitol) in the expression of DNA damage in the context of minilungs derived from human embryonic stem cells and in the cell line A549.ResultsAs in the case of the cell line A549, bleomycin can induce DNA damage in the generated minilungs enriched in alveolar cells. The results indicate that, in contrast to vitamin D, the treatment of the minilungs with the hypocalcemic analogs reduce significantly the bulk of DNA damage expression in both bidimensional arrays of epithelial cells (2D minilungs) and lung bud organoids (3D minilungs). The initial evaluation of a battery of commercially available vitamin D analogs shows a significant reduction in A549 cells of gH2AFX expression levels, a marker of DNA damage, cell senescence and aging.ConclusionsThe treatments based in hypocalcemic vitamin D analogs might be used to reduce the bulk of DNA damage and eventually the subsequent cell senescence expression that underlie lung conditions as those that can evolve with fibrosis.

Vitamin D Analogs Can Retard the Onset or Progression of Diabetic Kidney Disease: A Systematic Review

IntroductionPrevious studies have shown that vitamin D analogs (such as paricalcitol) can reduce albuminuria in patients with diabetes mellitus and retard the progression of diabetic kidney disease (DKD). A recent systematic review reported significant improvement of renal function in patients with DKD who received vitamin D or its analogs. Study-driven data about their use in improving DKD outcomes have continued to accumulate over the years.AimThis paper aims to systematically review the contemporary evidence about the effectiveness of vitamin D analogs in retarding the onset or progression of DKD.MethodsWith appropriate descriptors, two electronic databases (PubMed and Google Scholar) were searched for articles published between 2015 and 2021 in the English language. Primary studies that fulfilled the inclusion criteria were selected; their titles and abstracts were screened, and duplicates were removed. Relevant data were retrieved from the final selected studies using a preconceived data-extraction form.ResultsA total of eight studies (three randomized-controlled trials, one prospective study, and four cross-sectional studies) were reviewed. A total of 6,243 participants were investigated in the eight studies and comprised young adults, middle-aged adults, and the elderly with a male-gender predominance. One randomized controlled trial reported that paricalcitol significantly improved renal function in type 1 diabetes patients with renal impairment when combined with renin-angiotensin-aldosterone system (RAAS) blockers. A strong correlation between vitamin D deficiency and DKD risk was noted in the majority of the cross-sectional studies. High doses of cholecalciferol (4,000 or 10,000 IU/day), given early in DKD, significantly reduced disease prevalence.ConclusionParicalcitol may retard the onset or progression of DKD, especially if administered in combination with RAAS blockers. The association of vitamin D deficiency with DKD risk also supports this therapeutic effect. Future systematic reviews are still needed to strengthen the current evidence on therapeutic benefit of vitamin D or its analogs in DKD.

Vitamin D and Vitamin D Analogs as Adjuncts to Field Therapy Treatments for Actinic Keratoses: Current Research and Future Approaches

Actinic keratoses (AK), also known as solar keratoses, are precancerous hyperkeratotic papules caused by long-term exposure to ultraviolet radiation. Management of AK prior to progression to cutaneous malignancy represents an important window of intervention. This is important on a population level, given the high incidence, morbidity, financial costs, and the low but measurable risk of mortality from cutaneous neoplasia. Treatments for AK have been refined for many years with significant progress over the past decade. Those recent advancements lead to questions about current treatment paradigms and the role of harnessing the immune system in field therapies. Recent studies suggest a key interplay between vitamin D and cancer immunity; in particular, the systemic and/or topical vitamin D analogs can augment field therapies used for severe actinic damage. In this review, we will examine the literature supporting the use of vitamin D-directed therapies to improve field therapy approaches. An enhanced understanding of these recent concepts with a focus on mechanisms is important in the optimized management of AK. These mechanisms will be critical in guiding whether selected populations, including those with immunosuppression, heritable cancer syndromes, and other risk factors for skin cancer, can benefit from these new concepts with vitamin D analogs and whether the approaches will be as effective in these populations as in immunocompetent patients.

MO058INHIBITION OF OSTEOCLAST DIFFERENTIATION BY 1.25-D AND THE CALCIMIMETIC KP2326 REVEALS 1.25-D RESISTANCE IN ADVANCED CKD

Background and Aims Active vitamin D analogs and calcimimetics are cornerstones for managing secondary hyperparathyroidism (SHPT) in chronic kidney disease (CKD). Their direct effects on bone cells remain to be determined. Method Peripheral blood mononuclear cells (PBMCs) of 19 pediatric CKD patients and 6 healthy donors (HD) were differentiated into osteoclasts in presence of M-CSF and RANKL. Effect of combined or single treatment with active vitamin D (1.25-D) and/or the calcimimetic KP2326 were evaluated onto osteoclast differentiation and osteoclast mediated bone resorption. Results 1.25-D inhibited osteoclastic differentiation, a significant resistance to 1.25-D was observed when CKD worsens. A significant albeit less important inhibitory effect of KP2326 on osteoclastic differentiation was also found both in cells derived from HD and CKD patients, through an activation of the Erk pathway. This inhibitory effect was not modified by CKD stage. Combinatorial treatment with 1.25-D and KP2326 did not result in synergistic effects. Last, KP2326 significantly inhibited human osteoclast-mediated bone resorption. Conclusion Both 1.25-D and KP2326 inhibit osteoclastic differentiation, however to a different extent. Whilst 1.25-D has no significant effect on bone resorption, KP2326 inhibits bone resorption. Recent data showed that calcimimetics also have a direct anabolic effect on bone, through the stimulation of osteoblastic differentiation and mineralization in human mesenchymal stem cells in vitro. All these results provide a strong rationale for a global positive effect of calcimimetics on bone remodeling. Calcimimetics also significantly decrease FGF23 levels. In the setting of global systematic deleterious effects of high FGF23 levels in CKD, and keeping in mind that active vitamin D analogs stimulate FGF 23 production, all these data could favor the use of decreased doses of 1.25-D with low-doses of calcimimetics in SHPT in dialysis, the combination of these two therapies already being proposed in the 2017 K-DIGO guidelines.