MART-10, a less calcemic vitamin D analog, is more potent than 1α,25-dihydroxyvitamin D3 in inhibiting the metastatic potential of MCF-7 breast cancer cells in vitro

Co-drug development of gallic acid and metformin targeting the pro-inflammatory cytokines for the treatment of breast cancer

It is well-documented that pro-inflammatory cytokines and inflammation play a significant role in the expansion of cancer disease. Gallic acid (GA), a natural compound, and metformin (Met), a synthetic drug exhibit potent anticancer potential via the distinct molecular mechanism. However, whether both these compounds can act synergistically to preclude and treat cancer is still unknown. This prompted us to scrutinize, the synergism between GA and Met, and that of a new co-drug synthesizing of GA and Met (GA-Met) and investigated the chemo-protective effect against breast cancer with possible intervention of cytokines. In vivo studies were based on chemical carcinogenesis, challenging breast tissue by dimethylbenz[α]anthracene (DMBA). Tumour incidence, tumour burden, pro-inflammatory cytokines in serum, breast, hepatic tissue, macroscopically and histological analysis of mammary tumours were carried out and estimated. GA, Met and GA-Met co-drug exhibited the inhibition of cell proliferation; higher reduction of cell proliferation was observed by GA-Met. The inhibitory effect of GA-Met was linked to cell cycle arrest at G0/G1 phase, along with induction of apoptosis and accumulation in the sub-G1 phase. GA-Met significantly inhibited the cytokines production along with protection against DMBA-induced hyperplasia. Taken altogether, the current result suggests that GA-Met co-drug endows a safe and protective effect against cancer metastasis and can possibly use for the treatment of human breast cancer.

Vitamin D and Cancer: An Historical Overview of the Epidemiology and Mechanisms

This is a narrative review of the evidence supporting vitamin D’s anticancer actions. The first section reviews the findings from ecological studies of cancer with respect to indices of solar radiation, which found a reduced risk of incidence and mortality for approximately 23 types of cancer. Meta-analyses of observational studies reported the inverse correlations of serum 25-hydroxyvitamin D [25(OH)D] with the incidence of 12 types of cancer. Case-control studies with a 25(OH)D concentration measured near the time of cancer diagnosis are stronger than nested case-control and cohort studies as long follow-up times reduce the correlations due to changes in 25(OH)D with time. There is no evidence that undiagnosed cancer reduces 25(OH)D concentrations unless the cancer is at a very advanced stage. Meta-analyses of cancer incidence with respect to dietary intake have had limited success due to the low amount of vitamin D in most diets. An analysis of 25(OH)D-cancer incidence rates suggests that achieving 80 ng/mL vs. 10 ng/mL would reduce cancer incidence rates by 70 ± 10%. Clinical trials have provided limited support for the UVB-vitamin D-cancer hypothesis due to poor design and execution. In recent decades, many experimental studies in cultured cells and animal models have described a wide range of anticancer effects of vitamin D compounds. This paper will review studies showing the inhibition of tumor cell proliferation, dedifferentiation, and invasion together with the sensitization to proapoptotic agents. Moreover, 1,25-(OH)₂D₃ and other vitamin D receptor agonists modulate the biology of several types of stromal cells such as fibroblasts, endothelial and immune cells in a way that interferes the apparition of metastases. In sum, the available mechanistic data support the global protective action of vitamin D against several important types of cancer.

Vitamin D Regulates CXCL12/CXCR4 and Epithelial-to-Mesenchymal Transition in a Model of Breast Cancer Metastasis to Lung

Vitamin D deficiency is associated with poor cancer outcome in humans, and administration of vitamin D or its analogs decreases tumor progression and metastasis in animal models. Using the mouse mammary tumor virus-polyoma middle T antigen (MMTV-PyMT) model of mammary cancer, we previously demonstrated a significant acceleration of carcinogenesis in animals on a low vitamin D diet and a reduction in spontaneous lung metastases when mice received vitamin D through perfusion. We investigate here the action mechanism for vitamin D in lung metastasis in the same non-immunodeficient model and demonstrate that it involves the control of epithelial to mesenchymal transition as well as interactions between chemokine C-X-C motif chemokine 12 (CXCL12) and its receptor C-X-C chemokine receptor type 4 (CXCR4). In vitro, 10-9M vitamin D treatment modifies the phenotype of MMTV-PyMT primary mammary tumor cells and significantly decreases their invasiveness and mammosphere formation capacity by 40% and 50%, respectively. Vitamin D treatment also inhibits phospho-signal transducer and activator of transcription 3 (p-STAT3), zinc finger E-box-binding homeobox 1 (Zeb1), and vimentin by 52%, 75%, and 77%, respectively, and increases E-cadherin by 87%. In vivo, dietary vitamin D deficiency maintains high levels of Zeb1 and p-STAT3 in cells from primary mammary tumors and increases CXCL12 expression in lung stroma by 64%. In lung metastases, vitamin D deficiency increases CXCL12/CXCR4 co-localization by a factor of 2.5. These findings indicate an involvement of vitamin D in mammary cancer "seed" (primary tumor cell) and "soil" (metastatic site) and link vitamin D deficiency to epithelial-to-mesenchymal transition (EMT), CXCL12/CXCR4 signaling, and accelerated metastasis, suggesting vitamin D repleteness in breast cancer patients could enhance the efficacy of co-administered therapies in preventing spread to distant organs.

Knockdown of CYP24A1 Aggravates 1α,25(OH)2D3-Inhibited Migration and Invasion of Mouse Ovarian Epithelial Cells by Suppressing EMT

Epithelial-mesenchymal transition (EMT) bestows cancer cells with motile and invasive properties. But for ovarian tissues, EMT plays a physiological role in the postovulatory repair of ovary surface epithelial (OSE) cells. Accumulating data indicated that 1α,25(OH)₂D₃ decreased both the migration and invasion of various cancer cells by suppressing EMT. However, it remains unclear whether 1α,25(OH)₂D₃ inhibits the process of EMT during different stages of oncogenic transformation in mouse OSE (MOSE) cells. In present study, a spontaneous malignant transformation model of MOSE cells at three sequential stages (early, intermediate and late) was established in vitro first and then subjected to 1α,25(OH)₂D₃ treatment to investigate the effect of 1α,25(OH)₂D₃ on the oncogenic transformation of MOSE cells. We found that 1α,25(OH)₂D₃ significantly reduced the proliferation and invasion of late malignant transformed MOSE (M-L cells) cells by inhibiting EMT both in vitro and in vivo, but not in intermediate transformed (M-I) cells. Importantly, we found that the levels of CYP24A1 in M-I cells were dramatically higher than that in M-L cells following treatment with 1α,25(OH)₂D₃. Furthermore, we demonstrated that, in both M-I and M-L cells with CYP24A1 knockdown, 1α,25(OH)₂D₃ suppressed the proliferation and invasion, and reduced the expression of N-cadherin, Vimentin, β-catenin and Snail. In addition, knockdown of CYP24A1 suppressed EMT by increasing E-cadherin while decreasing N-cadherin, Vimentin, β-catenin and Snail. These findings provide support for inhibiting CYP24A1 as a potential approach to activate the vitamin D pathway in the prevention and therapy of ovarian cancer.

Vitamin D-Induced Molecular Mechanisms to Potentiate Cancer Therapy and to Reverse Drug-Resistance in Cancer Cells

Increasing interest in studying the role of vitamin D in cancer has been provided by the scientific literature during the last years, although mixed results have been reported. Vitamin D deficiency has been largely associated with various types of solid and non-solid human cancers, and the almost ubiquitous expression of vitamin D receptor (VDR) has always led to suppose a crucial role of vitamin D in cancer. However, the association between vitamin D levels and the risk of solid cancers, such as colorectal, prostate and breast cancer, shows several conflicting results that raise questions about the use of vitamin D supplements in cancer patients. Moreover, studies on vitamin D supplementation do not always show improvements in tumor progression and mortality risk, particularly for prostate and breast cancer. Conversely, several molecular studies are in agreement about the role of vitamin D in inhibiting tumor cell proliferation, growth and invasiveness, cell cycle arrest and inflammatory signaling, through which vitamin D may also regulate cancer microenvironment through the activation of different molecular pathways. More recently, a role in the regulation of cancer stem cells proliferation and short non-coding microRNA (miRNAs) expression has emerged, conferring to vitamin D a more crucial role in cancer development and progression. Interestingly, it has been shown that vitamin D is able not only to potentiate the effects of traditional cancer therapy but can even contribute to overcome the molecular mechanisms of drug resistance—often triggering tumor-spreading. At this regard, vitamin D can act at various levels through the regulation of growth of cancer stem cells and the epithelial–mesenchymal transition (EMT), as well as through the modulation of miRNA gene expression. The current review reconsiders epidemiological and molecular literature concerning the role of vitamin D in cancer risk and tumor development and progression, as well as the action of vitamin D supplementation in potentiating the effects of drug therapy and overcoming the mechanisms of resistance often triggered during cancer therapies, by critically addressing strengths and weaknesses of available data from 2010 to 2020.

24R,25-Dihydroxyvitamin D3 regulates breast cancer cells in vitro and in vivo

BACKGROUND

Epidemiological studies indicate high serum 25(OH)D₃ is associated with increased survival in breast cancer patients. Pre-clinical studies attributed this to anti-tumorigenic properties of its metabolite 1α,25(OH)₂D₃. However, 1α,25(OH)₂D₃ is highly calcemic and thus has a narrow therapeutic window. Here we propose another metabolite, 24R,25(OH)₂D₃, as an alternative non-calcemic vitamin D₃ supplement.

METHODS

NOD-SCID-IL2γR null female mice with MCF7 breast cancer xenografts in the mammary fat pad were treated with 24R,25(OH)₂D₃ and changes in tumor burden and metastases were assessed. ERα66+ MCF7 and T47D cells, and ERα66- HCC38 cells were treated with 24R,25(OH)₂D₃in vitro to assess effects on proliferation and apoptosis. Effects on migration and metastatic markers were assessed in MCF7.

RESULTS

24R,25(OH)₂D₃ reduced MCF7 tumor growth and metastasis in vivo. In vitro results indicate that this was not due to an anti-proliferative effect; 24R,25(OH)₂D₃ stimulated DNA synthesis in MCF7 and T47D. In contrast, markers of invasion and metastasis were decreased. 24R,25(OH)₂D₃ caused dose-dependent increases in apoptosis in MCF7 and T47D, but not HCC38 cells. Inhibitors to palmitoylation, caveolae integrity, phospholipase-D, and estrogen receptors (ER) demonstrate that 24R,25(OH)₂D₃ acts on MCF7 cells through caveolae-associated, phospholipase D-dependent mechanisms via cross-talk with ERs.

CONCLUSION

These results indicate that 24R,25(OH)₂D₃ shows promise in treatment of breast cancer by stimulating tumor apoptosis and reducing metastasis.

GENERAL SIGNIFICANCE

24R,25(OH)₂D₃ regulates breast cancer cell survival through ER-associated mechanisms similar to 24R,25(OH)₂D₃ effects on chondrocytes. Thus, 24R,25(OH)₂D₃ may modulate cell survival in other estrogen-responsive cell types, and its therapeutic potential should be investigated in ER-associated pathologies.

Interferon α-inducible protein 27 is an oncogene and highly expressed in cholangiocarcinoma patients with poor survival

Objective

Cholangiocarcinoma (CCA) is a devastating disease. Interferon α-inducible protein 27 (IFI27), originally known to involve in innate immunity, is later found to intervene in cell proliferation, leading to inventive studies regarding the role of IFI27 in cancer treatment. We aimed to investigate the role of IFI27 in CCA.

Materials and methods

Cell proliferation, migration, and invasion assays, Western blot, gene transfection and knockdown, immunofluorescent and immunohistochemical stains, and xenograft animal model were applied.

Results

IFI27 knockdown in CCA cells induced cell cycle arrest in S phase, resulting in lower cell proliferative rate in vitro and in vivo. IFI27 knockdown attenuated CCA cell migration and invasion through inhibition of epithelial–mesenchymal transition, which was supported by increased E-cadherin and decreased N-cadherin and fibronectin. Filamentous actin level was also reduced. IFI27 knockdown further repressed expression and secretion of vascular endothelial growth factor (VEGF-A), a strong stimulator of angiogenesis, through downregulation of c-jun and c-fos, which was supported in vitro by the finding that human vascular endothelial cells grew more slowly in conditioned medium of IFI27 knockdown on CCA cells and in vivo by the lower erythropoietin concentration found in the xenografted tumors derived from IFI27 knockdown on CCA cells. In addition, anti-VEGF-A antibody treatment was able to repress CCA cell growth. To the contrary, IFI27 overexpression could increase CCA cell proliferation, migration, and invasion. Clinically, higher IFI27 expression was linked to inferior overall survival of CCA patients.

Conclusion

Our data strongly suggest that IFI27 could be deemed as a potential target for CCA treatment.

HO-1 is a favorable prognostic factor for HBV-HCC patients who underwent hepatectomy

Background

More than 500,000 people suffered from hepatocelluar carcinoma (HCC) annually and the relative incidence to mortality rate indicates its unfavorable prognosis. Several studies have proved that heme-oxygenase-1 (HO-1) is indirectly engaged in the invasion and the metastasis of some types of malignancies, including breast cancer, prostate cancer, and lung cancer. The role of HO-1 in hepatitis B virus (HBV)-related HCC is still not clarified.

Materials and methods

The Western blot, doubling time, cell cycle analysis, migration assay, invasion assay, gene transfection, xenograft animal model, immunohistochemistry staining, and clinical validation study were applied in this study.

Results

HO-1 overexpression not only decreased the growth but also inhibited the migration and invasion in human HBV-HCC cells (Hep-3B vs PLC/PRF/5). The inhibitory effect on growth, migration, and invasion is further demonstrated by the overexpression of HO-1 in Hep-3B cell by transfection study. Furthermore, HO-1 decreasing the growth of HBV-HCC was confirmed in animal study. The clinical validation illustrated that higher HO1 expression was also associated with favorable disease-free survival of HBV-HCC patients who underwent hepatectomy.

Conclusions

We identified HO-1 as a favorable prognostic factor for HBV-HCC patients who underwent hepatectomy.

Circulating 25-hydroxyvitamin D level and prognosis of lung cancer patients: A systematic review and meta-analysis

BACKGROUND

Previous studies suggested a possible influence of circulating 25-hydroxyvitamin D [25(OH)D] level on the prognosis of lung cancer patients, but conflicting findings were reported. A systematic review and meta-analysis was thus conducted to comprehensively assess the influence of circulating 25(OH)D level on the prognosis of lung cancer patients.

METHODS

Prospective or retrospective cohort studies assessing the influence of circulating 25(OH)D level on the prognosis of lung cancer patients were considered eligible. Hazard Ratios (HR) were pooled using meta-analysis.

RESULTS

Eight studies with 2166 lung cancer patients were included. Meta-analysis of unadjusted HRs from four studies showed low circulating 25(OH)D level was significantly correlated with poor overall survival in lung cancer (HR=1.30, 95%CI 1.08-1.55, P=0.004). Meta-analysis of adjusted HRs from eight studies suggested that low circulating 25(OH)D level was not significantly correlated with poor overall survival (HR=1.25; P=0.13). However, sensitivity analysis suggested an obvious change in the pooled HRs when excluding single study by turns. When the study by Liu et al. was omitted, low circulating 25(OH)D level was significantly correlated with poor overall survival (HR=1.34; P=0.04).

CONCLUSION

The present systematic review and meta-analysis suggested a correlation between low circulating 25(OH)D level and poor overall survival in lung cancer. More studies are needed to further validate the finding above.

MART-10 represses cholangiocarcinoma cell growth and high vitamin D receptor expression indicates better prognosis for cholangiocarcinoma

Cholangiocarcinoma (CCA) is a devastating disease due to no effective treatments available. Since the non-mineral functions of vitamin D emerges, 1α,25(OH)₂D₃, the active form of vitamin D, has been applied in anti-cancer researches. In this study, we demonstrated that both the 1α,25(OH)₂D₃ analog, MART-10, and 1α,25(OH)₂D₃ possessed anti-growth effect on human CCA cells with MART-10 much more potent than 1α,25(OH)₂D₃. The growth inhibition of both drugs were mediated by induction of G0/G1 cell cycle arrest through upregulation of p27 and downregulation of CDK4, CDK6, and cyclin D3. Human neutrophil gelatinase associated lipocalin (NGAL) was found to be involved in 1α,25(OH)₂D₃ and MART-10 meditated growth inhibition for CCA as knockdown of NGAL decreased Ki-67 expression in SNU308 cells and rendered SNU308 cells less responsive to 1α,25(OH)₂D₃ and MART-10 treatment. Vitamin D receptor (VDR) knockdown partly abolished MART-10-induced inhibition of NGAL and cell growth in SNU308 cells. The xenograft animal study demonstrated MART-10 could effectively repressed CCA growth in vivo without inducing obvious side effects. The IHC examination of human CCA specimen for VDR revealed that higher VDR expression was linked with better prognosis. Collectively, our results suggest that MART-10 could be a promising regimen for CCA treatment.

Lipocalin 2 (LCN2) is a promising target for cholangiocarcinoma treatment and bile LCN2 level is a potential cholangiocarcinoma diagnostic marker

Cholangiocarcinoma (CCA) is a devastating disease due to resistance to traditional chemotherapies and radiotherapies. New therapeutic strategies against CCA are urgently needed. This study investigated the role of lipocalin-2 (LCN2) in human cholangiocarcinoma as a potential therapeutic target and diagnostic marker. So far, the role of LCN2 in cancer is still controversial and studies regarding the role of LCN2 in CCA are limited. LCN2 knockdown inhibited CCA cell growth in vitro and in vivo through induction of cell cycle arrest at G0/G1 phases and decreased metastatic potential due to repression of epithelial-mesenchymal transition (EMT). Overexpression of LCN2 in CCA cells increased cell metastatic potential. We showed for the first time that the N-myc downstream regulated gene 1 (NDRG1) and NDRG2, known as tumor suppressor genes, are negatively regulated by LCN2 in CCA cells. LCN2 concentration in bile was higher in patients with CCA than that in patients with gallstones, with a cutoff value of 20.08 ng/ml making this a potential diagnostic marker. Higher LCN2 expression was associated with worse survival in patients with CCA. LCN2 is a promising target for CCA treatment and bile LCN2 level is a potential diagnostic marker for CCA.

1α,25(OH)₂D₃ Suppresses the Migration of Ovarian Cancer SKOV-3 Cells through the Inhibition of Epithelial-Mesenchymal Transition

Ovarian cancer is the most lethal gynecological malignancy due to its high metastatic ability. Epithelial-mesenchymal transition (EMT) is essential during both follicular rupture and epithelium regeneration. However, it may also accelerate the progression of ovarian carcinomas. Experimental studies have found that 1α,25-dihydroxyvitamin-D3 [1α,25(OH)₂D₃] can inhibit the proliferation of ovarian cancer cells. In this study, we investigated whether 1α,25(OH)₂D₃ could inhibit the migration of ovarian cancer cells via regulating EMT. We established a model of transient transforming growth factor-β1(TGF-β1)-induced EMT in human ovarian adenocarcinoma cell line SKOV-3 cells. Results showed that, compared with control, 1α,25(OH)₂D₃ not only inhibited the migration and the invasion of SKOV-3 cells, but also promoted the acquisition of an epithelial phenotype of SKOV-3 cells treated with TGF-β1. We discovered that 1α,25(OH)₂D₃ increased the expression of epithelial marker E-cadherin and decreased the level of mesenchymal marker, Vimentin, which was associated with the elevated expression of VDR. Moreover, 1α,25(OH)₂D₃ reduced the expression level of transcription factors of EMT, such as slug, snail, and β-catenin. These results indicate that 1α,25(OH)₂D₃ suppresses the migration and invasion of ovarian cancer cells by inhibiting EMT, implying that 1α,25(OH)₂D₃ might be a potential therapeutic agent for the treatment of ovarian cancer.

MART-10, a newly synthesized vitamin D analog, represses metastatic potential of head and neck squamous carcinoma cells

Even with multidisciplinary treatment, the prognosis and quality of life of patients diagnosed with head and neck squamous cell carcinoma (HNSCC) are still not satisfactory. Previously, 19-Nor-2α-(3-hydroxypropyl)-1α,25(OH)₂D₃ (MART-10), the new brand 1α,25(OH)₂D₃ analog, has been demonstrated to be an effective drug to inhibit HNSCC growth in vitro. Since most cancer patients die of metastasis, in this study, the antimetastatic effect of MART-10 on HNSCC was investigated. Our results reveal that both 1α,25(OH)₂D₃ and MART-10 effectively repressed the migration and invasion of HNSCC cells, with MART-10 being much more potent than 1α,25(OH)₂D₃. The antimetastatic effect of 1α,25(OH)₂D₃ and MART-10 was mediated by attenuation of epithelial–mesenchymal transition (EMT), which was supported by the finding that the expression of EMT-inducing transcriptional factors, Sail and Twist, was inhibited by 1α,25(OH)₂D₃ and MART-10. The upregulation of E-cadherin and downregulation of N-cadherin in FaDu cells induced by both drugs further confirmed the repression of EMT. In addition, 1α,25(OH)₂D₃ and MART-10 treatment inhibited intracellular MMP-9 expression and extracellular MMP activity in FaDu cells. Collectively, our results suggest that the less-calcemia 1α,25(OH)₂D₃ analog, MART-10, is a promising drug for HNSCC treatment. Further clinical studies are warranted.

Vitamin D3-dependent VDR signaling delays ron-mediated breast tumorigenesis through suppression of β-catenin activity

The Ron receptor is upregulated in human breast cancers and correlates with enhanced metastasis and reduced patient survival. Ron overexpression drives mammary tumorigenesis through direct β-catenin activation and augmented tumor cell proliferation, migration and invasion. Ron and β-catenin are also coordinately elevated in breast cancers. The vitamin D receptor (VDR) antagonizes β-catenin signaling. Herein, we examined mammary tumor onset and progression using a Ron-driven murine model of breast tumorigenesis crossed with VDR deficient mice. VDR ablation accelerated mammary tumor onset and led to tumors that exhibited a desmoplastic phenotype and enhanced metastases. Tumor levels of active β-catenin were markedly increased in the absence of VDR. In vitro, VDR activation in breast cancer cells reduced β-catenin activation and transcriptional activity leading to elevated expression of the extracellular Wnt inhibitor dickkopf-related protein 1, and a reduction in the interaction of β-catenin with the cyclin D1 promoter. Expression of a stabilized form or β-catenin ablated the protective effects of VDR activation. Collectively, these studies delineate a protective role for VDR signaling in Ron-induced mammary tumorigenesis through disruption of β-catenin activation.

The Vitamin D Analog, MART-10, Attenuates Triple Negative Breast Cancer Cells Metastatic Potential

Regarding breast cancer treatment, triple negative breast cancer (TNBC) is a difficult issue. Most TNBC patients die of cancer metastasis. Thus, to develop a new regimen to attenuate TNBC metastatic potential is urgently needed. MART-10 (19-nor-2α-(3-hydroxypropyl)-1α,25(OH)₂D₃), the newly-synthesized 1α,25(OH)₂D₃ analog, has been shown to be much more potent in cancer growth inhibition than 1α,25(OH)₂D₃ and be active in vivo without inducing obvious side effect. In this study, we demonstrated that both 1α,25(OH)₂D₃ and MART-10 could effectively repress TNBC cells migration and invasion with MART-10 more effective. MART-10 and 1α,25(OH)₂D₃ induced cadherin switching (upregulation of E-cadherin and downregulation of N-cadherin) and downregulated P-cadherin expression in MDA-MB-231 cells. The EMT(epithelial mesenchymal transition) process in MDA-MB-231 cells was repressed by MART-10 through inhibiting Zeb1, Zeb2, Slug, and Twist expression. LCN2, one kind of breast cancer metastasis stimulator, was also found for the first time to be repressed by 1α,25(OH)₂D₃ and MART-10 in breast cancer cells. Matrix metalloproteinase-9 (MMP-9) activity was also downregulated by MART-10. Furthermore, F-actin synthesis in MDA-MB-231 cells was attenuated as exposure to 1α,25(OH)₂D₃ and MART-10. Based on our result, we conclude that MART-10 could effectively inhibit TNBC cells metastatic potential and deserves further investigation as a new regimen to treat TNBC.

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 and the Epithelial to Mesenchymal Transition

Several studies support reciprocal regulation between the active vitamin D derivative 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) and the epithelial to mesenchymal transition (EMT). Thus, 1,25(OH)₂D₃ inhibits EMT via the induction of a variety of target genes that encode cell adhesion and polarity proteins responsible for the epithelial phenotype and through the repression of key EMT inducers. Both direct and indirect regulatory mechanisms mediate these effects. Conversely, certain master EMT inducers inhibit 1,25(OH)₂D₃ action by repressing the transcription of VDR gene encoding the high affinity vitamin D receptor that mediates 1,25(OH)₂D₃ effects. Consequently, the balance between the strength of 1,25(OH)₂D₃ signaling and the induction of EMT defines the cellular phenotype in each context. Here we review the current understanding of the genes and mechanisms involved in the interplay between 1,25(OH)₂D₃ and EMT.

Vitamin D as Supplemental Therapy for Pneumocystis Pneumonia

The combination of all-trans retinoic acid (ATRA) and primaquine (PMQ) has been shown to be effective for therapy of Pneumocystis pneumonia (PCP). Since a high concentration of ATRA has significant adverse effects, the possibility that vitamin D can be used to replace ATRA for PCP therapy was investigated. C57BL/6 mice were immunosuppressed by depleting CD4(+) cells and infected with Pneumocystis murina 1 week after initiation of immunosuppression. Three weeks after infection, the mice were treated orally for 3 weeks with vitamin D3 (VitD3) alone, PMQ alone, a combination of VitD3 and PMQ (VitD3-PMQ), or a combination of trimethoprim and sulfamethoxazole (TMP-SMX). Results showed that VitD3 (300 IU/kg/day) had a synergistic effect with PMQ (5 mg/kg/day) for therapy of PCP. Flow cytometric studies showed that this VitD3-PMQ combination recovered the CD11b(low) CD11c(high) alveolar macrophage population in mice with PCP as effectively as TMP-SMX. The VitD3-PMQ combination also reduced the massive infiltration of inflammatory cells into the lungs and the severity of lung damage. VitD3 was also shown to reduce the dose of TMP-SMX required for effective treatment of PCP. Taken together, results of this study suggest that a VitD3-PMQ combination can be used as an alternative therapy for PCP.

Hepatocellular carcinoma cells express 25(OH)D-1α-hydroxylase and are able to convert 25(OH)D to 1α,25(OH)₂D, leading to the 25(OH)D-induced growth inhibition

Hepatocellular carcinoma (HCC) is the most diagnosed liver cancer without effective treatments available for advanced HCC. Vitamin D is getting popular due to its anti-cancer characteristics. However, the clinical application of 1α,25(OH)2D, the active form of vitamin, is hampered by its hypercalcemia side effect. 1α,25(OH)2D is converted from 25(OH)D, the index of serum vitamin D status, by CYP27B1, which is originally found in kidneys but recently detected in non-renal tissues. 25(OH)D has been shown to repress some cancers expressing CYP27B1 due to the local conversion of 25(OH)D to 1α,25(OH)2D, which works in a intra-, auto-, or paracrine manner and thus minimizes the risk of hypercalcemia. In this study, we found CYP27B1 expression in human hepatocyte, HCC, and HepG2 cells. As we treated HepG2 cells with 25(OH)D, the 1α,25(OH)2D target gene CYP24A1 expression was increased and was further upregulated as CYP27B1 transfection or downregulated as CYP27B1 knockdown. Other 1α,25(OH)2D target genes in HepG2 cells, p21 and p27 were also stimulated by 25(OH)D after CYP27B1 transfection. Further, 25(OH)D could inhibit HepG2 cells growth, which was potentiated by CYP27B1 transfection. Collectively, we showed for the first time that HCC expressed CYP27B1 and was able to covert 25(OH)D to 1α,25(OH)2D in vitro, thus responsive to 25(OH)D treatment. Our data justifies the application of 25(OH)D and CYP27B1 gene transfection therapy in further HCC treatment studies.

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.

MART-10, the vitamin D analog, is a potent drug to inhibit anaplastic thyroid cancer cell metastatic potential

The survival rate of anaplastic thyroid cancer (ATC) is still very poor due to its fast growth and high metastatic potential. Currently, no effective treatment is available. The active form of vitamin D3, 1α,25(OH)2D3, has been shown to have a anti-metastatic effect in pre-clinical studies, however induction of hypercalcemia hampered its clinical application. The new class of less-calcemic vitamin D analog, 19-nor-2α-(3-hydroxypropyl)-1α,25-dihydroxyvitamin D3 (MART-10), is much more potent than 1α,25(OH)2D3 to repress cancer growth and metastasis in a variety of cancers. In this study, we demonstrated that both 1α,25(OH)2D3 and MART-10 could effectively inhibit the migration and invasion of ATC cells, 8305C and 8505C, with MART-10 much more potent than 1α,25(OH)2D3. The anti-metastatic effect of 1α,25(OH)2D3 and MART-10 on ATC cells is mediated by reversal of cadherin switch (upregulation of E-cadherin and downregulation of N-cadherin), which led to the attenuation of EMT process, and decrease of F-actin formation. We further showed that the expressions of Slug, the EMT-related transcriptional factor, and MMP-9 were inhibited by 1α,25(OH)2D3 and MART-10 in 8505C cells, but not in 8303C cells. Since metastasis is the important cause of ATC-related death, our results strongly encourage the further in vivo study of MART-10 application against ATC.

Vitamin D in cancer chemoprevention

CONTEXT

There is increasing evidence that Vitamin D (Vit D) and its metabolites, besides their well-known calcium-related functions, may also exert antiproliferative, pro-differentiating, and immune modulatory effects on tumor cells in vitro and may also delay tumor growth in vivo.

OBJECTIVE

The aim of this review is to provide fresh insight into the most recent advances on the role of Vit D and its analogues as chemopreventive drugs in cancer therapy.

METHODS

A systematic review of experimental and clinical studies on Vit D and cancer was undertaken by using the major electronic health database including ISI Web of Science, Medline, PubMed, Scopus and Google Scholar.

RESULTS AND CONCLUSION

Experimental and clinical observations suggest that Vit D and its analogues may be effective in preventing the malignant transformation and/or the progression of various types of human tumors including breast cancer, prostate cancer, colorectal cancer, and some hematological malignances. These findings suggest the possibility of the clinical use of these molecules as novel potential chemopreventive and anticancer agents.

19-Norvitamin D analogs for breast cancer therapy

The active form of vitamin D3, 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3 or calcitriol), is known to inhibit the proliferation and invasiveness of many types of cancer cells, including breast, colon, pancreatic, prostate, and liver cancer cells. These findings support the use of 1α,25(OH)2D3 for the treatment of these types of cancer. However, 1α,25(OH)2D3 can cause hypercalcemia, so analogs of 1α,25(OH)2D3 that are less calcemic but exhibit more potent anti-tumor activity would be good candidates as therapeutic agents. Therefore, a series of 19-norvitamin D analogs, in which the methylidene group on C19 is replaced with 2 hydrogen atoms, have been synthesized by several laboratories. In our laboratory, we have designed and synthesized a series of 2α-functional group substituted 19-norvitamin D3 analogs and examined their anti-proliferative activity. Among them, 2α- and 2β-(3-hydroxypropyl)-1α,25-dihydroxy-19-norvitamin D3 (MART-10 and MART-11) were found to be the most promising. Here, we review the rationale and approaches for the synthesis of different 19-norvitamin D analogs, and the pre-clinical studies using these analogs in breast cancer cells, in particular, we chose MART-10 for its potential application to the prevention and treatment of breast cancer.

WNT-1 inducible signaling pathway protein-1 enhances growth and tumorigenesis in human breast cancer

WNT1 inducible signaling pathway protein 1 (WISP1) plays a key role in many cellular functions in a highly tissue-specific manner; however the role of WISP1 in breast cancer is still poorly understood. Here, we demonstrate that WISP1 acts as an oncogene in human breast cancer. We demonstrated that human breast cancer tissues had higher WISP1 mRNA expression than normal breast tissues and that treatment of recombinant WISP1 enhanced breast cancer cell proliferation. Further, ectopic expression of WISP1 increased the growth of breast cancer cells in vitro and in vivo. WISP1 transfection also induced epithelial-mesenchymal-transition (EMT) in MCF-7 cells, leading to higher migration and invasion. During this EMT-inducing process, E-cadherin was repressed and N-cadherin, snail, and β-catenin were upregulated. Filamentous actin (F-actin) remodeling and polarization were also observed after WISP1 transfection into MCF-7 cells. Moreover, forced overexpression of WISP1 blocked the expression of NDRG1, a breast cancer tumor suppressor gene. Our study provides novel evidence that WISP1-modulated NDRG1 gene expression is dependent on a DNA fragment (-128 to +46) located within the human NDRG1 promoter. Thus, we concluded that WISP1 is a human breast cancer oncogene and is a potential therapeutic target.

The vitamin D analog, MART-10, represses metastasis potential via downregulation of epithelial-mesenchymal transition in pancreatic cancer cells

Pancreatic cancer (PDA) is a devastating disease and there is no effective treatment available at present. To develop new regiments against PDA is urgently needed. Previously we have shown that vitamin D analog, MART-10 (19-nor-2α-(3-hydroxypropyl)-1α,25(OH)2D3), exerted potent antiproliferative effect on PDA in vitro and in vivo without causing hypercalcemia. Since metastasis is the major cause of PDA-related death, we therefore investigate the anti-metastasis effect of MART-10 on PDA. Our results showed that both 1α,25(OH)2D3 and MART-10 repressed migration and invasion of BxPC-3 and PANC cells with MART-10 much more potent than 1α,25(OH)2D3. 1α,25(OH)2D3 and MART-10 inhibited epithelial-mesenchymal transition (EMT) in pancreatic cancer cells through downregulation of Snail, Slug, and Vimentin expression in BxPC-3 and PANC cells. MART-10 further blocked cadherin switch (from E-cadherin to N-cadherin) in BxPC-3 cells. The F-actin synthesis in the cytoplasm of BxPC-3 cells was also repressed by 1α,25(OH)2D3 and MART-10 as determined by immunofluorescence stain. Both 1α,25(OH)2D3 and MART-10 decreased MMP-2 and -9 secretion in BxPC-3 cells as determined by western blot and zymography. Collectively, MART-10 should be deemed as a promising regimen against PDA.