CYP24 inhibition preserves 1α,25-dihydroxyvitamin D(3) anti-proliferative signaling in lung cancer cells

CYP24A1 DNA Methylation in Colorectal Cancer as Potential Prognostic and Predictive Markers

The DNA methylation of CYP24A1 can regulate its gene expression and may play a role in the occurrence and progression of colorectal cancer (CRC). However, the association between CYP24A1 DNA methylation and the prognosis of CRC patients has not yet been reported. In this study, differential methylation analysis was conducted in both blood and tissue cohorts, and differential expression analysis was performed in the tissue cohort with in vitro validation. GO and KEGG enrichment analyses were performed on CYP24A1-related genes. A correlation between CYP24A1 promoter methylation and its gene expression was explored. Kaplan-Meier survival and Cox regression analyses were performed to investigate the impact of CYP24A1 DNA methylation on the prognosis of CRC patients. Prognostic risk scores were constructed for survival prediction. Immune infiltration analysis was also conducted. Our results showed that the hypermethylation of cg02712555 in tumor tissues (hazard ratio, 0.48; 95% confidence interval, 0.24-0.94; p = 0.032) and CpG site 41 in peripheral leukocytes (HR, 0.35; 95%CI, 0.14-0.84; p = 0.019) were both associated with decreased overall mortality in CRC patients. Prognostic risk scores showed robust predictive capabilities of these two CpG loci for the prognosis of CRC patients. CYP24A1 hypermethylation was positively correlated with infiltration levels of activated CD4 + T cells, activated CD8 + T cells, activated B cells, activated dendritic cells, and macrophages. Taken together, our findings indicate that the methylation levels of specific CpG sites within the CYP24A1 promoter region in blood leukocytes and tumors are potential prognostic and predictive markers for overall survival in CRC patients.

Pan-Cancer Analysis Confirms the Prognostic and Immunological Implications of the 1,25-Dihydroxy Vitamin D3 Receptor in Cervical Squamous Cell Carcinoma

Vitamin D receptor (VDR), specifically the 1,25-dihydroxy form, holds significant importance in various types of cancer, including cervical squamous cell carcinoma (CESC), which poses a significant public health challenge. A pan-cancer analysis was conducted on VDR in CESC, with a focus on its expression and relationship with immune infiltration and genetic alterations. Bioinformatics databases, including TIMER, GEPIA, UALCAN, cBioportal, and Kaplan-Meier Plotter, have been utilized. VDR expression in CESC has been validated using publicly available data. Results were significantly upregulated (P=0.05) in THCA, BRCA, KICH, LUAD, LIHC, STAD, UCEC, CESC, CHOL, ESCA, and HNSC samples. We analyzed the correlation between VDR expression and various clinicopathological factors such as age, race, and cancer stage. VDR expression was significantly upregulated across all age groups, with the highest levels observed in older adults followed by young and middle-aged adults. VDR gene expression was significantly elevated across all races, including Caucasians, African-Americans, and Asians, compared to that in the normal group. Furthermore, VDR expression was significantly upregulated in cancer stages 1, 2, 3, and 4, with the highest increase observed in stage 3 compared to that in normal individuals. We analyzed the expression of the VDR in relation to immune cell type and tumor cell purity in CESC. Our results indicated that VDR expression was positively correlated with neutrophils and dendritic cells and negatively correlated with tumor cell purity in CESC patients. There was no significant correlation between VDR expression and the abundance of B cells, CD8+ T cells, CD4+ T cells, and macrophages. Our study found no significant effect of VDR expression on patient prognosis, although it was positively correlated with CD4+ T cells. The Cox proportional hazards model indicated that age and immune cells did not significantly affect prognosis. Most VDR mutations are concentrated in diffuse large B-cell lymphoma, with an amplification frequency of 4% and a deep deletion frequency of 2.2%. GEO confirmed VDR expression in CESC, identifying 1515 upregulated and 1877 downregulated genes, with volcano plots showing CESC downregulation in patients.

Vitamin D metabolism in cancer: potential feasibility of vitamin D metabolism blocking therapy

In this review, we discuss the possibility of the vitamin D metabolizing enzyme CYP24A1 being a therapeutic target for various tumors including breast, colorectal and prostate tumors. Given the pleiotropic cellular activity of vitamin D, its deficiency impairs its physiological function in target cells and results in various pathologies including cancer. In addition, accumulated data have shown that elevated expression of CYP24A1 promotes carcinogenesis in various cancer subtypes by decreasing the bioavailability of vitamin D metabolites. Thus, we propose the potential feasibility of vitamin D metabolism-blocking therapy in various types of human malignancies that express constitutive CYP24A1.

Cytochrome P450 27C1 Level Dictates Lung Cancer Tumorigenicity and Sensitivity towards Multiple Anticancer Agents and Its Potential Interplay with the IGF-1R/Akt/p53 Signaling Pathway

Cytochrome P450 enzymes (CYP450s) exert mighty catalytic actions in cellular metabolism and detoxication, which play pivotal roles in cell fate determination. Preliminary data shows differential expression levels of CYP27C1, one of the "orphan P450s" in human lung cancer cell lines. Here, we study the functions of CYP27C1 in lung cancer progression and drug endurance, and explore its potential to be a diagnostic and therapeutic target for lung cancer management. Quantitative real-time PCR and immunoblot assays were conducted to estimate the transcription and protein expression level of CYP27C1 in human lung cancer cell lines, which was relatively higher in A549 and H1975 cells, but was lower in H460 cells. Stable CYP27C1-knockdown A549 and H1975 cell lines were established, in which these cells showed enhancement in cell proliferation, colony formation, and migration. In addition, aberrant IGF-1R/Akt/p53 signal transduction was also detected in stable CYP27C1-knockdown human lung cancer cells, which exhibited greater tolerance towards the treatments of anticancer agents (including vinorelbine, picropodophyllin, pacritinib, and SKLB610). This work, for the first time, reveals that CYP27C1 impacts lung cancer cell development by participating in the regulation of the IGF-1R/Akt/p53 signaling pathway, and the level of CYP27C1 plays indispensable roles in dictating the cellular sensitivity towards multiple anticancer agents.

Novel DNA Aptamer for CYP24A1 Inhibition with Enhanced Antiproliferative Activity in Cancer Cells

Overexpression of the vitamin D3-inactivating enzyme CYP24A1 (cytochrome P450 family 24 subfamily and hereafter referred to as CYP24) can cause chronic kidney diseases, osteoporosis, and several types of cancers. Therefore, CYP24 inhibition has been considered a potential therapeutic approach. Vitamin D3 mimetics and small molecule inhibitors have been shown to be effective, but nonspecific binding, drug resistance, and potential toxicity limit their effectiveness. We have identified a novel 70-nt DNA aptamer-based inhibitor of CYP24 by utilizing the competition-based aptamer selection strategy, taking CYP24 as the positive target protein and CYP27B1 (the enzyme catalyzing active vitamin D3 production) as the countertarget protein. One of the identified aptamers, Apt-7, showed a 5.8-fold higher binding affinity with CYP24 than the similar competitor CYP27B1. Interestingly, Apt-7 selectively inhibited CYP24 (the relative CYP24 activity decreased by 39.1 ± 3% and showed almost no inhibition of CYP27B1). Furthermore, Apt-7 showed cellular internalization in CYP24-overexpressing A549 lung adenocarcinoma cells via endocytosis and induced endogenous CYP24 inhibition-based antiproliferative activity in cancer cells. We also employed high-speed atomic force microscopy experiments and molecular docking simulations to provide a single-molecule explanation of the aptamer-based CYP24 inhibition mechanism. The novel aptamer identified in this study presents an opportunity to generate a new probe for the recognition and inhibition of CYP24 for biomedical research and could assist in the diagnosis and treatment of cancer.

Vitamin D in prostate cancer

Signaling through the vitamin D receptor has been shown to be biologically active and important in a number of preclinical studies in prostate and other cancers. Epidemiologic data also indicate that vitamin D signaling may be important in the cause and prognosis of prostate and other cancers. These data indicate that perturbation of vitamin D signaling may be a target for the prevention and treatment of prostate cancer. Large studies of vitamin D supplementation will be required to determine whether these observations can be translated into prevention strategies. This paper reviews the available data in the use of vitamin D compounds in the treatment of prostate cancer. Clinical data are limited which support the use of vitamin D compounds in the management of men with prostate cancer. However, clinical trials guided by existing preclinical data are limited.

The use of LP533401 as a therapeutic option for renal osteodystrophy affects, renal calcium handling, vitamin D metabolism, and bone health in uremic rats

BACKGROUND

Klotho is a key regulator of phosphate and Ca²⁺-transport in the kidney. Recently, we showed that treatment with LP533401 improved bone health in rats with chronic kidney disease (CKD) via the normalization of serum phosphate resulting from the reduced renal expression of phosphate cotransporters, including Klotho.

METHODS

We evaluated the effect of LP533401 therapy on Klotho-expression-dependent Ca²⁺-transporters, renal calcium handling, and the potential consequences for the bone of uremic rats.

RESULTS

Treatment with LP533401 and its vehicle resulted in the inhibition of transient receptor potential vanilloid receptor subtypes 5 and 6 (TRPV5, TRPV6) and calbindin (CaBP-28k, CaBP-9k) expression. The compensatory acceleration in renal expression of Na+/Ca²⁺-exchanger, 25-hydroxyvitamin d-1α-hydroxylase (CYP27B1), the intensification of vitamin D metabolism, and disruption of sophisticated balance between 1,25-dihydroxyvitamin D-serotonin was observed, especially in rats treated with LP533401. The imbalance between 1,25-dihydroxyvitamin D-serotonin levels led to intensified bone remodeling and improvement in bone geometry, mineral status, and strength in animals treated with LP533401.

CONCLUSION

The modulation of circulating serotonin and its relation to other regulators of calcium handling can play an important role in calcium homeostasis and bone integrity in CKD rats treated with LP533401.

Human uterine leiomyoma contains low levels of 1, 25 dihdroxyvitamin D3, and shows dysregulated expression of vitamin D metabolizing enzymes

OBJECTIVES

To evaluate tissue concentration of 1, 25 dihydroxyvitamin D3, and gene expression level of CYP27B1 that codes for 1-α hydroxylase (vitamin D activating enzyme), and CYP24A1 that codes for 24-hydroxylase (vitamin D catabolizing enzyme) in human uterine leiomyoma (ULM), its adjacent myometrium (Myo-F), and normal myometrium (Myo-N).

STUDY DESIGN

Levels of 1, 25 dihydroxyvitamin D3 were measured using HPLC and Diode detectors whereas CYP27B1, and CYP24A1 expressions were assessed using Real-Time PCR in ULM, Myo-F, and Myo-N. Non-parametric statistics were used.

RESULTS

ULMs contained significantly less 1, 25 dihydroxy vitamin D3 compared to Myo-F (3.0, IQR: 1.0-9.0 versus 6.0, IQR: 3.0-13.0 μg/ kg, P value is 0.03). No significant difference was detected between ULM and Myo-N, or Myo-F and Myo-N. Intratumoral level of the active form of vitamin D did not differ according to the type of ULM (submucous or interstitial/subserous), or to the ULM volume. CYP27B1 was expressed in ULM (2.17, IQR: 0.65-4.9), Myo-F (4.94, IQR: 1.04-22.59), and Myo-N (0.99, IQR: 0.49-1.71) to a comparable level. CYP24A1 expression was significantly higher in ULM compared to Myo-N (2.00, IQR: 0.69-10.77 versus 0.22, IQR: 00- 0.96, respectively, P value is 0.04).

CONCLUSIONS

Human ULMs contain significantly lower 1, 25 dihydroxyvitamin D3 than its adjacent myometrium. ULM, Myo-F, and Myo-N express CYP27B1 and CYP24A1. ULMs express significantly higher level of CYP24A1 than normal myometrium indicating that over expression of 24-hydroxylase is a mechanism by which ULMs sustain a relative state of hypovitaminosis D.

Calcitriol and cancer therapy: A missed opportunity

The vitamin D receptor is expressed in most tissues of the body - and the cancers that arise from those tissues. The vitamin D signaling pathway is active in those tissues and cancers. This is at least consistent with the hypothesis that perturbing this signaling may have a favorable effect on the genesis and growth of cancers. Epidemiologic data indicate that vitamin D signaling may be important in the initiation and outcome of a number of types of cancer. Many studies have shown that calcitriol (1,25 dihydroxycholecalciferol) and other vitamin D compounds have antiproliferative, pro-apoptotic, anti-cell migration and antiangiogenic activity in a number of preclinical studies in many different cancer types. Unfortunately, the assessment of the activity of calcitriol or other vitamin D analogues in the treatment of cancer, as single agents or in combination with other anticancer agents has been stymied by the failure to adhere to commonly accepted principles of drug development and clinical trials conduct.

Progesterone potentiates the growth inhibitory effects of calcitriol in endometrial cancer via suppression of CYP24A1

Here, we evaluated the expression of CYP24A1, a protein that inactivates vitamin D in tissues. CYP24A1 expression was increased in advanced-stage endometrial tumors compared to normal tissues. Similarly, endometrial cancer cells expressed higher levels of CYP24A1 than immortalized endometrial epithelial cells. RT-PCR and Western blotting were used to examine CYP24A1 mRNA and protein levels in endometrial cancer cells after 8, 24, 72, and 120 h of exposure to progesterone, progestin derivatives and calcitriol, either alone or in combination. Progestins inhibited calcitriol-induced expression of CYP24A1 and splice variant CYP24SV mRNA and protein in cancer cells. Furthermore, actinomycin D, but not cycloheximide, blocked calcitriol-induced CYP24A1 splicing. siRNA-induced knockdown of CYP24A1 expression sensitized endometrial cancer cells to calcitriol-induced growth inhibition. These data suggest that CYP24A1 overexpression reduces the antitumor effects of calcitriol in cancer cells and that progestins may be beneficial for maintaining calcitriol's anti-endometrial cancer activity.

Vitamin D derivatives potentiate the anticancer and anti-angiogenic activity of tyrosine kinase inhibitors in combination with cytostatic drugs in an A549 non-small cell lung cancer model

Numerous in vitro and in vivo studies have demonstrated that calcitriol [1,25(OH)₂D₃] and different vitamin D analogs possess antineoplastic activity, regulating proliferation, differentiation and apoptosis, as well as angiogenesis. Vitamin D compounds have been shown to exert synergistic effects when used in combination with different agents used in anticancer therapies in different cancer models. The aim of this study was to evaluate the mechanisms of the cooperation of the vitamin D compounds [1,24(OH)₂D₃ (PRI-2191) and 1,25(OH)₂D₃] with tyrosine kinase inhibitors (imatinib and sunitinib) together with cytostatics (cisplatin and docetaxel) in an A549 non-small cell lung cancer model. The cytotoxic effects of the test compounds used in different combinations were evaluated on A549 lung cancer cells, as well as on human lung microvascular endothelial cells (HLMECs). The effects of such combinations on the cell cycle and cell death were also determined. In addition, changes in the expression of proteins involved in cell cycle regulation, angiogenesis and the action of vitamin D were analyzed. Moreover, the effects of 1,24(OH)₂D₃ on the anticancer activity of sunitinib and sunitinib in combination with docetaxel were examined in an A549 lung cancer model in vivo. Experiments aiming at evaluating the cytotoxicity of the combinations of the test agents revealed that imatinib and sunitinib together with cisplatin or docetaxel exerted potent anti-proliferative effects in vitro on A549 lung cancer cells and in HLMECs; however, 1,24(OH)₂D₃ and 1,25(OH)₂D₃ enhanced the cytotoxic effects only in the endothelial cells. Among the test agents, sunitinib and cisplatin decreased the secretion of vascular endothelial growth factor (VEGF)-A from the A549 lung cancer cells. The decrease in the VEGF-A level following incubation with cisplatin correlated with a higher p53 protein expression, while no such correlation was observed following treatment of the A549 cells with sunitinib. Sunitinib together with docetaxel and 1,24(OH)₂D₃ exhibited a more potent anticancer activity in the A549 lung cancer model compared to double combinations and to treatment with the compounds alone. The observed anticancer activity may be the result of the influence of the test agents on the process of tumor angiogenesis, for example, through the downregulation of VEGF-A expression in tumor and also on the induction of cell death inside the tumor.

The roles of UVB and vitamin D in reducing risk of cancer incidence and mortality: A review of the epidemiology, clinical trials, and mechanisms

Global cancer incidence and mortality rates are high and increasing. Thus, it is imperative to find novel solutions to preventing cancer incidence and treating it at an affordable yet efficacious manner. The solar UVB-vitamin D-cancer hypothesis was first proposed in 1980 based on a geographical ecological study. Since then, numerous ecological and observational studies as well as studies of mechanisms have provided support for the hypothesis. However, observational studies have not provided consistent support, in part due to using a single blood draw from any season to use for serum 25-hydroxyvitamin D [25(OH)D] concentration in prospective studies with long follow-up times. Case-controls studies, in which blood is drawn near time of diagnosis, and prospective studies in which blood is drawn in the sunnier half of the year, are more likely to find significant inverse relations between 25(OH)D and cancer incidence. Three vitamin D plus calcium clinical trials have found significant reduction in all-cancer incidence. This paper reviews the evidence for vitamin D in reducing incidence of and increasing survival from breast, colorectal, lung, ovarian, pancreatic, and prostate cancer. The epidemiological evidence provides strong support for all of these types of cancer except for non-aggressive prostate cancer. Studies of the cellular mechanisms of vitamin D action in different cancer cell types, strongly indicate that vitamin D can exert protective and anti-tumorigenic activities that would retard cellular transformation, hyperplasia and cancer progression. Based on the scientific evidence reviewed in this paper, individuals and health providers can consider increasing 25(OH)D concentrations through sensible sun exposure and/or vitamin D supplementation to reduce risk of and, in conjunction with standard care, treat cancer. Public health acceptance of vitamin D for cancer prevention and treatment requires stronger support from vitamin D clinical trials.

Diet-derived 25-hydroxyvitamin D3 activates vitamin D receptor target gene expression and suppresses EGFR mutant non-small cell lung cancer growth in vitro and in vivo

Epidemiologic studies implicate vitamin D status as a factor that influences growth of EGFR mutant lung cancers. However, laboratory based evidence of the biological effect of vitamin D in this disease is lacking. To fill this knowledge gap, we determined vitamin D receptor (VDR) expression in human lung tumors using a tissue microarray constructed of lung cancer cases from never-smokers (where EGFR gene mutations are prevalent). Nuclear VDR was detected in 19/19 EGFR mutant tumors. Expression tended to be higher in tumors with EGFR exon 19 deletions than those with EGFR L858R mutations. To study anti-proliferative activity and signaling, EGFR mutant lung cancer cells were treated with the circulating metabolite of vitamin D, 25-hydroxyvitamin D3 (25D3). 25D3 inhibited clonogenic growth in a dose-dependent manner. CYP27B1 encodes the 1α-hydroxylase (1αOHase) that converts 25D3 to the active metabolite, 1,25-dihydroxyvitamin D3 (1,25D3). Studies employing VDR siRNA, CYP27B1 zinc finger nucleases, and pharmacologic inhibitors of the vitamin D pathway indicate that 25D3 regulates gene expression in a VDR-dependent manner but does not strictly require 1αOHase-mediated conversion of 25D3 to 1,25D3. To determine the effects of modulating serum 25D3 levels on growth of EGFR mutant lung tumor xenografts, mice were fed diets containing 100 or 10,000 IU vitamin D3/kg. High dietary vitamin D3 intake resulted in elevated serum 25D3 and significant inhibition of tumor growth. No toxic effects of supplementation were observed. These results identify EGFR mutant lung cancer as a vitamin D-responsive disease and diet-derived 25D3 as a direct VDR agonist and therapeutic agent.

Vitamin D-Related Gene Polymorphisms, Plasma 25-Hydroxy-Vitamin D, Cigarette Smoke and Non-Small Cell Lung Cancer (NSCLC) Risk

Epidemiological studies regarding the relationship between vitamin D, genetic polymorphisms in the vitamin D metabolism, cigarette smoke and non-small cell lung cancer (NSCLC) risk have not been investigated comprehensively. To search for additional evidence, the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique and radioimmunoassay method were utilized to evaluate 5 single-nucleotide polymorphisms (SNPs) in vitamin D receptor (VDR), 6 SNPs in 24-hydroxylase (CYP24A1), 2 SNPs in 1α-hydroxylase (CYP27B1) and 2 SNPs in vitamin D-binding protein (group-specific component, GC) and plasma vitamin D levels in 426 NSCLC cases and 445 controls from China. Exposure to cigarette smoke was ascertained through questionnaire information. Multivariable linear regressions and mixed effects models were used in statistical analysis. The results showed that Reference SNP rs6068816 in CYP24A1, rs1544410 and rs731236 in VDR and rs7041 in GC were statistically significant in relation to reduction in NSCLC risk (p < 0.001-0.05). No significant connection was seen between NSCLC risk and overall plasma 25-hydroxyvitamin D [25(OH)D] concentrations, regardless of smoking status. However, the mutation genotype of CYP24A1 rs6068816 and VDR rs1544410 were also significantly associated with increased 25(OH)D levels only in both the smoker and non-smoker cases (p < 0.01-0.05). Meanwhile, smokers and non-smokers with mutated homozygous rs2181874 in CYP24A1 had significantly increased NSCLC risk (odds ratio (OR) = 2.14, 95% confidence interval (CI) 1.47-3.43; p = 0.031; OR = 3.57, 95% CI 2.66-4.74; p = 0.019, respectively). Smokers with mutated homozygous rs10735810 in VDR had significantly increased NSCLC risk (OR = 1.93, 95% CI 1.41-2.76; p = 0.015). However, smokers with mutated homozygous rs6068816 in CYP24A1 had significantly decreased NSCLC risk (OR = 0.43, 95% CI 0.27-1.02; p = 0.006); and smokers and non-smokers with mutated homozygous rs1544410 in VDR had significantly decreased NSCLC risk (OR = 0.51, 95% CI 0.34-1.17; p = 0.002; OR = 0.26, 95% CI 0.20-0.69; p = 0.001, respectively). There are significant joint effects between smoking and CYP24A1 rs2181874, CYP24A1 rs6068816, VDR rs10735810, and VDR rs1544410 (p < 0.01-0.05). Smokers with mutated homozygous rs10735810 in VDR had significantly increased NSCLC risk (OR = 1.93, 95% CI 1.41-2.76; p = 0.015). In summary, the results suggested that the lower the distribution of vitamin D concentration, the more the genetic variations in CYP24A1, VDR and GC genes may be associated with NSCLC risk. In addition, there are significant joint associations of cigarette smoking and vitamin D deficiency on NSCLC risk.

Calcitriol Inhibits Cervical Cancer Cell Proliferation Through Downregulation of HCCR1 Expression

Calcitriol (1α,25-dihydroxyvitamin D3) has demonstrated anticancer activity against several tumors. However, the underlying mechanism for this activity is not yet fully understood. Our experiment was designed and performed to address one aspect of this issue in cervical cancer. HeLa S3 cells were cultured in media with various concentrations of calcitriol. Cell proliferation and cell cycle were assessed by spectrophotometry and flow cytometry, respectively. The mRNA and protein expression levels of human cervical cancer oncogene (HCCR-1) and p21 were determined by RT-PCR and Western blot, respectively. Results indicated that calcitriol inhibited HeLa S3 cell proliferation and induced cell cycle arrest at the G₁ phase. Calcitriol decreased HCCR-1 protein expression in a dose- and time-dependent manner. Furthermore, promoter activity analyses revealed that transcriptional regulation was involved in the inhibition of HCCR-1 expression. Overexpression of HCCR-1 in HeLa S3 cells reversed the inhibition of cell proliferation and G₁ phase arrest that resulted from calcitriol treatment. In addition, calcitriol increased p21 expression and promoter activity. HCCR-1 overexpression decreased p21 expression and promoter activity. Thus, our results suggested that calcitriol inhibited HeLa S3 cell proliferation by decreasing HCCR-1 expression and increasing p21 expression.

Vitamin D Signaling Modulators in Cancer Therapy

The antiproliferative and pro-apoptotic effects of 1α,25-dihydroxycholecalciferol (1,25(OH)2D3, 1,25D3, calcitriol) have been demonstrated in various tumor model systems in vitro and in vivo. However, limited antitumor effects of 1,25D3 have been observed in clinical trials. This may be attributed to a variety of factors including overexpression of the primary 1,25D3 degrading enzyme, CYP24A1, in tumors, which would lead to rapid local inactivation of 1,25D3. An alternative strategy for improving the antitumor activity of 1,25D3 involves the combination with a selective CYP24A1 inhibitor. The validity of this approach is supported by numerous preclinical investigations, which demonstrate that CYP24A1 inhibitors suppress 1,25D3 catabolism in tumor cells and increase the effects of 1,25D3 on gene expression and cell growth. Studies are now required to determine whether selective CYP24A1 inhibitors+1,25D3 can be used safely and effectively in patients. CYP24A1 inhibitors plus 1,25D3 can cause dose-limiting toxicity of vitamin D (hypercalcemia) in some patients. Dexamethasone significantly reduces 1,25D3-mediated hypercalcemia and enhances the antitumor activity of 1,25D3, increases VDR-ligand binding, and increases VDR protein expression. Efforts to dissect the mechanisms responsible for CYP24A1 overexpression and combinational effect of 1,25D3/dexamethasone in tumors are underway. Understanding the cross talk between vitamin D receptor (VDR) and glucocorticoid receptor (GR) signaling axes is of crucial importance to the design of new therapies that include 1,25D3 and dexamethasone. Insights gained from these studies are expected to yield novel strategies to improve the efficacy of 1,25D3 treatment.

Vitamin D Repletion Reduces the Progression of Premalignant Squamous Lesions in the NTCU Lung Squamous Cell Carcinoma Mouse Model

The chemopreventive actions of vitamin D were examined in the N-nitroso-tris-chloroethylurea (NTCU) mouse model, a progressive model of lung squamous cell carcinoma (SCC). SWR/J mice were fed a deficient diet (D) containing no vitamin D3, a sufficient diet (S) containing 2,000 IU/kg vitamin D3, or the same diets in combination with the active metabolite of vitamin D, calcitriol (C; 80 μg/kg, weekly). The percentage (%) of the mucosal surface of large airways occupied by dysplastic lesions was determined in mice after treatment with a total dose of 15 or 25 μmol NTCU (N). After treatment with 15 μmol NTCU, the percentages of the surface of large airways containing high-grade dysplastic (HGD) lesions were vitamin D-deficient + NTCU (DN), 22.7% [P < 0.05 compared with vitamin D-sufficient +NTCU (SN)]; DN + C, 12.3%; SN, 8.7%; and SN + C, 6.6%. The extent of HGD increased with NTCU dose in the DN group. Proliferation, assessed by Ki-67 labeling, increased upon NTCU treatment. The highest Ki-67 labeling index was seen in the DN group. As compared with SN mice, DN mice exhibited a three-fold increase (P < 0.005) in circulating white blood cells (WBC), a 20% (P < 0.05) increase in IL6 levels, and a four-fold (P < 0.005) increase in WBC in bronchial lavages. Thus, vitamin D repletion reduces the progression of premalignant lesions, proliferation, and inflammation, and may thereby suppress development of lung SCC. Further investigations of the chemopreventive effects of vitamin D in lung SCC are warranted.

Vitamin D-neutralizing CYP24A1 expression, oncogenic mutation states and histological findings of human papillary thyroid cancer

OBJECTIVE

The aims of the present study were to examine gene and protein expression of the vitamin D-inactivating 24-hyroxylase (CYP24A1) and the activating 1-alpha-hydroxylase (CYP27B1) enzyme in human papillary thyroid cancer (PTC), furthermore, to investigate the association between CYP24A1 expression and numerous clinical, histological parameters and somatic oncogene mutation status of thyroid tumor tissues.

MATERIALS AND METHODS

Gene expression analysis was carried out in 100 Hungarian thyroid samples, both normal and papillary tumor tissue sections of the same patient. The specific mRNA to the selected genes was analyzed by TaqMan probe-based quantitative real-time RT-PCR. The somatic oncogene mutation states of BRAF, NRAS, HRAS and KRAS were also tested.

RESULTS

CYP24A1 mRNA expression was markedly increased in 52 cases (52%) of the examined papillary cancers compared with that of normal thyroid tissue. There was a tendency toward difference in the distribution of high-level CYP24A1 in the PTC accompanied with somatic oncogene mutation. Positive correlation was seen between increased CYP24A1 expression rate and a group of variables reflecting tumor malignity (mainly vascular invasion, lymph node metastasis, tumor size, hypothyreosis) by principal components analysis. No significant alteration was seen in CYP27B1 gene expression between neoplastic and normal tissues.

CONCLUSIONS

A definite alteration was seen in vitamin D3-inactivating CYP24A1 gene activity in PTC compared to their normal tissues on a relatively large patient population. Our findings raise the possibility that CYP24A1 may also directly be involved in thyroid carcinogenesis.

Simultaneous Quantification of 25-Hydroxyvitamin D3 and 24,25-Dihydroxyvitamin D3 in Rats Shows Strong Correlations between Serum and Brain Tissue Levels

While vitamin D3 is recognized as a neuroactive steroid affecting both brain development and function, efficient analytical method in determining vitamin D3 metabolites in the brain tissue is still lacking, and the relationship of vitamin D3 status between serum and brain remains elusive. Therefore, we developed a novel analysis method by using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to simultaneously quantify the concentrations of 25-hydroxyvitamin D3 (25(OH)D3) and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) in the serum and brain of rats fed with different dose of vitamin D3. We further investigated whether variations of serum vitamin D3 metabolites could affect vitamin D3 metabolite levels in the brain. Serum and brain tissue were analyzed by HPLC-MS/MS with electrospray ionization following derivatization with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD). The method is highly sensitive, specific, and accurate to quantify 25(OH)D3 and 24,25(OH)2D3 in animal brain tissue. Vitamin D3 metabolites in brain tissue were significantly lower in rats fed with a vitamin D deficiency diet than in rats fed with high vitamin D3 diet. There was also a strong correlation of vitamin D3 metabolites in serum and brain. These results indicate that vitamin D3 status in serum affects bioavailability of vitamin D3 metabolites in the brain.

Increased CYP24A1 expression is associated with BRAF(V600E) mutation and advanced stages in papillary thyroid carcinoma

OBJECTIVE

1α, 25(OH)2 D3 (calcitriol), the active form of vitamin D, has been shown to exert antiproliferative effects in many cancers. Overexpression of CYP24A1, the primary vitamin D-inactivating enzyme, is also observed in a variety of human cancers, thus potentially neutralizing the antitumour effect of 1α, 25(OH)2 D3. This study investigates the expression of CYP24A1 and the effect of BRAF(V600E) on its expression in thyroid cancer.

METHODS

We investigated 60 papillary thyroid carcinoma (PTC) specimens for CYP24A1 expression and its association with BRAF mutation and disease progression. CYP24A1 expression was measured by real-time RT-PCR, and BRAF(V600E) mutation was detected by PCR-DNA sequencing analysis. The interaction between BRAF(V600E) and CYP24A1 expression was determined by Western blot analysis and real-time RT-PCR.

RESULTS

CYP24A1 expression was increased in PTC as compared to benign multinodular goitre. The expression was further increased in stage III and IV tumours. There is a strong correlation between CYP24A1 overexpression and BRAF(V600E) mutation (P < 0·01). In thyroid cancer cell lines expressing BRAF(V600E) , CYP24A1 expression was significantly higher when compared to those without BRAF(V600E) expression. BRAF(V600E) transgene expression in CAL62 cell line can induce CYP24A1 expression. Furthermore, BRAF(V600E) inhibitor PLX4720 can significantly down-regulate CYP24A1 expression and enhance the antiproliferative effects of calcitriol in thyroid cancer cell lines.

CONCLUSION

CYP24A1 overexpression is a poor prognostic indicator for PTC and may reflect BRAF(V600E) mutation and MARK activation. The crosstalk between vitamin D and MAPK signalling pathways results in resistance to calcitriol-mediated antitumour effects, and the resistance can be reversed by BRAF(V600E) inhibitor PLX4720.

Pharmacological effects of vitamin D and its analogs: recent developments

Calcitriol, the hormonally active form of vitamin D, is well known for its diverse pharmacological activities, including modulation of cell growth, neuromuscular and immune function and reduction of inflammation. Calcitriol and its analogs exert potent effects on cellular differentiation and proliferation, regulate apoptosis and produce immunomodulatory effects. The purpose of this review is to provide information on various physiological and pharmacological activities of calcitriol and its newly discovered analogs. Special emphasis is given to skin diseases, cancer, diabetes and multiple sclerosis. A discussion is raised on the mechanisms of action of calcitriol and its analogs in various diseases, as well as on possible methods of delivery and targeting.

VDR activity is differentially affected by Hic-5 in prostate cancer and stromal cells

Patients with prostate cancer treated with androgen deprivation therapy (ADT) eventually develop castrate-resistant prostate cancer (CRPC). 1,25-Dihydroxyvitamin D3 (1,25D3/calcitriol) is a potential adjuvant therapy that confers antiproliferative and pro-differentiation effects in vitro, but has had mixed results in clinical trials. The impact of the tumor microenvironment on 1,25D3 therapy in patients with CRPC has not been assessed. Transforming growth factor β (TGFβ), which is associated with the development of tumorigenic "reactive stroma" in prostate cancer, induced vitamin D3 receptor (VDR) expression in the human WPMY-1 prostate stromal cell line. Similarly, TGFβ enhanced 1,25D3-induced upregulation of CYP24A1, which metabolizes 1,25D3 and thereby limits VDR activity. Ablation of Hic-5, a TGFβ-inducible nuclear receptor coregulator, inhibited basal VDR expression, 1,25D3-induced CYP24A1 expression and metabolism of 1,25D3 and TGFβ-enhanced CYP24A1 expression. A Hic-5-responsive sequence was identified upstream (392-451 bp) of the CYP24A1 transcription start site that is occupied by VDR only in the presence of Hic-5. Ectopic expression of Hic-5 sensitized LNCaP prostate tumor cells to growth-inhibitory effects of 1,25D3 independent of CYP24A1. The sensitivity of Hic-5-expressing LNCaP cells to 1,25D3-induced growth inhibition was accentuated in coculture with Hic-5-ablated WPMY-1 cells. Therefore, these findings indicate that the search for mechanisms to sensitize prostate cancer cells to the antiproliferative effects of VDR ligands needs to account for the impact of VDR activity in the tumor microenvironment.

IMPLICATIONS

Hic-5 acts as a coregulator with distinct effects on VDR transactivation, in prostate cancer and stromal cells, and may exert diverse effects on adjuvant therapy designed to exploit VDR activity in prostate cancer.

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) Signaling Capacity and the Epithelial-Mesenchymal Transition in Non-Small Cell Lung Cancer (NSCLC): Implications for Use of 1,25(OH)2D3 in NSCLC Treatment

1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) exerts anti-proliferative activity by binding to the vitamin D receptor (VDR) and regulating gene expression. We previously reported that non-small cell lung cancer (NSCLC) cells which harbor epidermal growth factor receptor (EGFR) mutations display elevated VDR expression (VDR^high) and are vitamin D-sensitive. Conversely, those with K-ras mutations are VDR^low and vitamin D-refractory. Because EGFR mutations are found predominately in NSCLC cells with an epithelial phenotype and K-ras mutations are more common in cells with a mesenchymal phenotype, we investigated the relationship between vitamin D signaling capacity and the epithelial mesenchymal transition (EMT). Using NSCLC cell lines and publically available lung cancer cell line microarray data, we identified a relationship between VDR expression, 1,25(OH)₂D₃ sensitivity, and EMT phenotype. Further, we discovered that 1,25(OH)₂D₃ induces E-cadherin and decreases EMT-related molecules SNAIL, ZEB1, and vimentin in NSCLC cells. 1,25(OH)₂D₃-mediated changes in gene expression are associated with a significant decrease in cell migration and maintenance of epithelial morphology. These data indicate that 1,25(OH)₂D₃ opposes EMT in NSCLC cells. Because EMT is associated with increased migration, invasion, and chemoresistance, our data imply that 1,25(OH)₂D₃ may prevent lung cancer progression in a molecularly defined subset of NSCLC patients.

Vitamin D deficiency and the lung: disease initiator or disease modifier?

Vitamin D deficiency is a global public health problem and has been associated with an increased incidence and severity of many diseases including diseases of the respiratory system. These associations have largely been demonstrated epidemiologically and have formed the basis of the justification for a large number of clinical supplementation trials with a view to improving disease outcomes. However, the trials that have been completed to date and the ongoing experimental studies that have attempted to demonstrate a mechanistic link between vitamin D deficiency and lung disease have been disappointing. This observation raises many questions regarding whether vitamin D deficiency is truly associated with disease pathogenesis, is only important in the exacerbation of disease or is simply an indirect biomarker of other disease mechanisms? In this review, we will briefly summarize our current understanding of the role of vitamin D in these processes with a focus on lung disease.

24-Hydroxylase in cancer: impact on vitamin D-based anticancer therapeutics

The active vitamin D hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) plays a major role in regulating calcium homeostasis and bone mineralization. 1,25(OH)2D3 also modulates cellular proliferation and differentiation in a variety of cell types. 24-Hydroxylase, encoded by the CYP24A1 gene, is the key enzyme which converts 1,25(OH)2D3 to less active calcitroic acid. Nearly all cell types express 24-hydroxylase, the highest activity being observed in the kidney. There is increasing evidence linking the incidence and prognosis of certain cancers to low serum 25(OH)D3 levels and high expression of vitamin D 24-hydroxylase, supporting the idea that elevated CYP24A1 expression may stimulate degradation of vitamin D metabolites including 25(OH)D3 and 1,25(OH)2D3. The over expression of CYP24A1 in cancer cells may be a factor affecting 1,25(OH)2D3 bioavailability and anti-proliferative activity pre-clinically and clinically. The combination of 1,25(OH)2D3 with CYP24A1 inhibitors enhances 1,25(OH)2D3 mediated signaling and anti-proliferative effects and may be useful in overcoming effects of aberrant CYP24A1 expression. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Differential response to 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) in non-small cell lung cancer cells with distinct oncogene mutations

We previously demonstrated that non-small cell lung cancer (NSCLC) cells and primary human lung tumors aberrantly express the vitamin D3-catabolizing enzyme, CYP24, and that CYP24 restricts transcriptional regulation and growth control by 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) in NSCLC cells. To ascertain the basis for CYP24 dysregulation, we assembled a panel of cell lines that represent distinct molecular classes of lung cancer: cell lines were selected which harbored mutually exclusive mutations in either the K-ras or the Epidermal Growth Factor Receptor (EGFR) genes. We observed that K-ras mutant lines displayed a basal vitamin D receptor (VDR)(low)CYP24(high) phenotype, whereas EGFR mutant lines had a VDR(high)CYP24(low) phenotype. A mutation-associated difference in CYP24 expression was also observed in clinical specimens. Specifically, K-ras mutation was associated with a median 4.2-fold increase in CYP24 mRNA expression (p=4.8×10(-7)) compared to EGFR mutation in a series of 147 primary lung adenocarcinoma cases. Because of their differential basal expression of VDR and CYP24, we hypothesized that NSCLC cells with an EGFR mutation would be more responsive to 1,25(OH)2D3 treatment than those with a K-ras mutation. To test this, we measured the ability of 1,25(OH)2D3 to increase reporter gene activity, induce transcription of endogenous target genes, and suppress colony formation. In each assay, the extent of 1,25(OH)2D3 response was greater in EGFR mutation-positive HCC827 and H1975 cells than in K-ras mutation-positive A549 and 128.88T cells. We subsequently examined the effect of combining 1,25(OH)2D3 with erlotinib, which is used clinically in the treatment of EGFR mutation-positive NSCLC. 1,25(OH)2D3/erlotinib combination resulted in significantly greater growth inhibition than either single agent in both the erlotinib-sensitive HCC827 cell line and the erlotinib-resistant H1975 cell line. These data are the first to suggest that EGFR mutations may identify a lung cancer subset which remains responsive to and is likely to benefit from 1,25(OH)2D3 administration. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Serum 1,25-dihydroxyvitamin D: an outcome prognosticator in human sepsis

In sepsis, the vitamin D active metabolite 1,25-dihydroxyvitamin D (1,25(OH)₂D) may play a crucial role by its action to produce cathelicidin and improve endothelial barrier function, such that a deficiency in 1,25(OH)₂D is associated with poor outcome. To test our hypothesis, we performed analysis of stored plasma samples from a prospective observational study in 91 patients with sepsis, age of 59.1+/−2.0 years, 52.7% females, and 11.0% deaths at 30 days. Vitamin D status, including 25-hydroxyvitamin D (25(OH)D), 1,25(OH)₂D, 24,25-dihydroxyvitamin D (24,25(OH)₂D), and parathyroid hormone (PTH), were measured daily over 3 days after hospital admission. At baseline, 1,25(OH)₂D was significantly different between survivors vs. non-survivors. But there was no significant difference in 25(OH)D, 24,25(OH)₂D, and PTH. In a multivariable binomial logistic regression model, age, total calcium and 1,25(OH)₂D were significant predictors of 30-day mortality. Kaplan Meier analysis showed that patients with mean 1,25(OH)₂D measured over 3 days of < = 13.6 pg/mL had 57.1% 30-day survival compared to 91.7% in patients with 1,25 (OH)₂D level >13.6 pg/mL (p<0.01). From repeated measures regression analysis, there was significant increase in 1,25(OH)₂D for increases in 25(OH)D in both survivors and non-survivors. However, compared to survivors, the low 25(OH)D in non-survivors was insufficient to account for the larger decrease in 1,25(OH)₂D, indicating a dysfunctional 1α-hydroxylase. Additionally, there was a significant negative correlation between PTH and 1,25(OH)₂D in both survivors and non-survivors, suggesting a severe impairment in the effect of PTH to increase renal 1α-hydroxylase activity. In conclusion, low 1,25(OH)₂D levels are associated with increased 30-day mortality in sepsis patients, likely due to impaired 25(OH)D hydroxylation and PTH insensitivity. Our data also suggest that the active metabolite 1,25(OH)₂D may be an important therapeutic target in the design of sepsis clinical trials.

Dysregulation of vitamin D3 synthesis leads to enhanced cholangiocarcinoma growth

BACKGROUND

Cholangiocarcinoma is a deadly biliary tumour with limited treatment strategies. Vitamin (1,25(OH)2D) has anti-proliferative effects on several cancers. Vitamin D3 is synthesized by the enzyme, CYP27B1, and signals via the nuclear vitamin D3 receptor. The enzyme, CYP24A1, degrades vitamin D3.

AIMS

(i) Measure the expression of CYP27B1, CYP24A1, and vitamin D3 receptor in human nonmalignant and cholangiocarcinoma lines and biopsy control or tumour samples; and (ii) evaluate the effects of vitamin D3 on vitamin D3 synthesis and cholangiocarcinoma growth.

METHODS

In vitro studies were performed in malignant and nonmalignant cholangiocytes. Vitamin D3 receptor, CYP24 and CYP27 expression was measured in cell lines and biopsy samples. Cell lines were stimulated with vehicle or vitamin D3 from 30min to 48h. Cell viability was assessed by MTS assays and BrdU incorporation. Vitamin D3 receptor, CYP24A1 and CYP27B1 expression was measured in cholangiocarcinoma cells stimulated with vehicle or vitamin D3.

RESULTS

In cholangiocarcinoma lines and biopsy samples, vitamin D3 receptor and CYP24A1 expression increased compared to controls, whereas CYP27B1 expression was decreased or unchanged. Vitamin D3 induced nuclear translocation of vitamin D3 receptor in cholangiocarcinoma and decreased cholangiocarcinoma growth.

CONCLUSION

Treatment with vitamin D3 decreased CYP24A1, whereas CYP27B1 expression increased. Modulation of vitamin D3 synthesis may be important in the management of cholangiocarcinoma.

Inhibition of protein kinase CK2 reduces Cyp24a1 expression and enhances 1,25-dihydroxyvitamin D(3) antitumor activity in human prostate cancer cells

Vitamin D has broad range of physiological functions and antitumor effects. 24-Hydroxylase, encoded by the CYP24A1 gene, is the key enzyme for degrading many forms of vitamin D including the most active form, 1,25D(3). Inhibition of CYP24A1 enhances 1,25D(3) antitumor activity. To isolate regulators of CYP24A1 expression in prostate cancer cells, we established a stable prostate cancer cell line PC3 with CYP24A1 promoter driving luciferase expression to screen a small molecular library for compounds that inhibit CYP24A1 promoter activity. From this screening, we identified, 4,5,6,7-tetrabromobenzimidazole (TBBz), a protein kinase CK2 selective inhibitor as a disruptor of CYP24A1 promoter activity. We show that TBBz inhibits CYP24A1 promoter activity induced by 1,25D(3) in prostate cancer cells. In addition, TBBz downregulates endogenous CYP24A1 mRNA level in TBBz-treated PC3 cells. Furthermore, siRNA-mediated CK2 knockdown reduces 1,25D(3)-induced CYP24A1 mRNA expression in PC3 cells. These results suggest that CK2 contributes to 1,25D(3)-mediated target gene expression. Finally, inhibition of CK2 by TBBz or CK2 siRNA significantly enhances 1,25D(3)-mediated antiproliferative effect in vitro and in vivo in a xenograft model. In summary, our findings reveal that protein kinase CK2 is involved in the regulation of CYP24A1 expression by 1,25D(3) and CK2 inhibitor enhances 1,25D(3)-mediated antitumor effect.

Analytical measurement of serum 25-OH-vitamin D₃, 25-OH-vitamin D₂ and their C3-epimers by LC-MS/MS in infant and pediatric specimens

OBJECTIVES

To develop a simple and sensitive LC-MS/MS procedure for quantification of serum 25-OH-vitamin D₃ (25-OH-D₃), 25-OH-vitamin D₂ (25-OH-D₂), and their C3-epimers.

METHODS

Serum 25-OH-vitamin D metabolites were extracted with MTBE and quantified by LC-MS/MS. Commercially available calibrators and QC materials were employed. The ion-transition 401.2→365.2 was monitored for 25-OH-D₃ and C3-epi-25-OH-D₃, 407.2→371.3 for d6-25-OH-D₃, 413.2→331.2 for 25-OH-D₂ and C3-epi-25-OH-D₂ and 419.2→337.1 for, d6-25-OH-D₂. As a proof-of-principle, 25-OH-D₃ and C3-epi-25-OH-D₃ were quantified in 200 pediatric subjects (0-20 years of age). Cholecalciferol supplements were examined as a potential source of C3-epimer.

RESULTS

The assay provided an LLOQ of ≤2.8 nmol/L for all 25-OH-D metabolites, with a linear response up to 400 nmol/L. The CV was <10% for 25-OH-D₂/₃ and <15% for C3-epi-25-OH-D₃. C3-epi-25-OH-D₃ was quantified in all subjects, with higher concentrations observed in infants ≤1 year of age (11.44 nmol/L vs. 4.4 nmol/L; p<0.001). Within the first year of life, 25-OH-D₃ concentrations increased linearly, while C3-epi-25-OH-D₃ concentrations remained constant. At 12 months of age, C3-epi-25-OH-D₃ concentration dropped by almost 50% (11.4 nmol/L in infants ≤1year of age vs. 5.4 nmol/L in infants 1-2years of age; p<0.001). Liquid vitamin D₃ supplements did not contain appreciable amounts of C3-epi-D₃.

CONCLUSIONS

The proposed LC-MS/MS procedure is suitable for quantifying 25-OH-D₃ metabolites. Although the C3-epimer is present in all pediatric subjects, it is significantly elevated in individuals ≤1 year of age and drops at 12 months of age. Oral vitamin D supplements are unlikely to be a significant source of C3-vitamin D epimer.