Greater synergism of retinoic acid receptor (RAR) agonists with vitamin D3 than that of retinoid X receptor (RXR) agonists with regard to growth inhibition and differentiation induction in monoblastic leukemia cells

Effect of Vitamin D on Graft-versus-Host Disease

The different cell subsets of the immune system express the vitamin D receptor (VDR). Through the VDR, vitamin D exerts different functions that influence immune responses, as previously shown in different preclinical models. Based on this background, retrospective studies explored the impacts of vitamin D levels on the outcomes of patients undergoing allogeneic hematopoietic stem-cell transplantation, showing that vitamin D deficiency is related to an increased risk of complications, especially graft-versus-host disease. These results were confirmed in a prospective cohort trial, although further studies are required to confirm this data. In addition, the role of vitamin D on the treatment of hematologic malignancies was also explored. Considering this dual effect on both the immune systems and tumor cells of patients with hematologic malignancies, vitamin D might be useful in this setting to decrease both graft-versus-host disease and relapse rates.

Baseline Serum Vitamin A and D Levels Determine Benefit of Oral Vitamin A&D Supplements to Humoral Immune Responses Following Pediatric Influenza Vaccination

Maximizing vaccine efficacy is critical, but previous research has failed to provide a one-size-fits-all solution. Although vitamin A and vitamin D supplementation studies have been designed to improve vaccine efficacy, experimental results have been inconclusive. Information is urgently needed to explain study discrepancies and to provide guidance for the future use of vitamin supplements at the time of vaccination. We conducted a randomized, blinded, placebo-controlled study of influenza virus vaccination and vitamin supplementation among 2 to 8 (inclusive) year old children over three seasons, including 2015–2016 (n = 9), 2016–2017 (n = 44), and 2017–2018 (n = 26). Baseline measurements of vitamins A and D were obtained from all participants. Measurements were of serum retinol, retinol-binding protein (RBP, a surrogate for retinol), and 25-hydroxyvitamin D (25(OH)D). Participants were stratified into two groups based on high and low incoming levels of RBP. Children received two doses of the seasonal influenza virus vaccine on days 0 and 28, either with an oral vitamin supplement (termed A&D; 20,000 IU retinyl palmitate and 2000 IU cholecalciferol) or a matched placebo. Hemagglutination inhibition (HAI) antibody responses were evaluated toward all four components of the influenza virus vaccines on days 0, 28, and 56. Our primary data were from season 2016–2017, as enrollment was highest in this season and all children exhibited homogeneous and negative HAI responses toward the Phuket vaccine at study entry. Responses among children who entered the study with insufficient or deficient levels of RBP and 25(OH)D benefited from the A&D supplement (p < 0.001 for the day 28 Phuket response), whereas responses among children with replete levels of RBP and 25(OH)D at baseline were unaffected or weakened (p = 0.02 for the day 28 Phuket response). High baseline RBP levels associated with high HAI titers, particularly for children in the placebo group (baseline RBP correlated positively with Phuket HAI titers on day 28, r = 0.6, p = 0.003). In contrast, high baseline 25(OH)D levels associated with weak HAI titers, particularly for children in the A&D group (baseline 25(OH)D correlated negatively with Phuket HAI titers on day 28, r = −0.5, p = 0.02). Overall, our study demonstrates that vitamin A&D supplementation can improve immune responses to vaccines when children are vitamin A and D-insufficient at baseline. Results provide guidance for the appropriate use of vitamins A and D in future clinical vaccine studies.

Pin1 inhibition exerts potent activity against acute myeloid leukemia through blocking multiple cancer-driving pathways

Background

The increasing genomic complexity of acute myeloid leukemia (AML), the most common form of acute leukemia, poses a major challenge to its therapy. To identify potent therapeutic targets with the ability to block multiple cancer-driving pathways is thus imperative. The unique peptidyl-prolyl cis-trans isomerase Pin1 has been reported to promote tumorigenesis through upregulation of numerous cancer-driving pathways. Although Pin1 is a key drug target for treating acute promyelocytic leukemia (APL) caused by a fusion oncogene, much less is known about the role of Pin1 in other heterogeneous leukemia.

Methods

The mRNA and protein levels of Pin1 were detected in samples from de novo leukemia patients and healthy controls using real-time quantitative RT-PCR (qRT-PCR) and western blot. The establishment of the lentiviral stable-expressed short hairpin RNA (shRNA) system and the tetracycline-inducible shRNA system for targeting Pin1 were used to analyze the biological function of Pin1 in AML cells. The expression of cancer-related Pin1 downstream oncoproteins in shPin1 (Pin1 knockdown) and Pin1 inhibitor all-trans retinoic acid (ATRA) treated leukemia cells were examined by western blot, followed by evaluating the effects of genetic and chemical inhibition of Pin1 in leukemia cells on transformed phenotype, including cell proliferation and colony formation ability, using trypan blue, cell counting assay, and colony formation assay in vitro, as well as the tumorigenesis ability using in vivo xenograft mouse models.

Results

First, we found that the expression of Pin1 mRNA and protein was significantly increased in both de novo leukemia clinical samples and multiple leukemia cell lines, compared with healthy controls. Furthermore, genetic or chemical inhibition of Pin1 in human multiple leukemia cell lines potently inhibited multiple Pin1 substrate oncoproteins and effectively suppressed leukemia cell proliferation and colony formation ability in cell culture models in vitro. Moreover, tetracycline-inducible Pin1 knockdown and slow-releasing ATRA potently inhibited tumorigenicity of U937 and HL-60 leukemia cells in xenograft mouse models.

Conclusions

We demonstrate that Pin1 is highly overexpressed in human AML and is a promising therapeutic target to block multiple cancer-driving pathways in AML.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0611-7) contains supplementary material, which is available to authorized users.

Induced differentiation of human myeloid leukemia cells into M2 macrophages by combined treatment with retinoic acid and 1α,25-dihydroxyvitamin D3

Retinoids and 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) induce differentiation of myeloid leukemia cells into granulocyte and macrophage lineages, respectively. All-trans retinoic acid (ATRA), which is effective in the treatment of acute promyelocytic leukemia, can induce differentiation of other types of myeloid leukemia cells, and combined treatment with retinoid and 1,25(OH)₂D₃ effectively enhances the differentiation of leukemia cells into macrophage-like cells. Recent work has classified macrophages into M1 and M2 types. In this study, we investigated the effect of combined treatment with retinoid and 1,25(OH)₂D₃ on differentiation of myeloid leukemia THP-1 and HL60 cells. 9-cis Retinoic acid (9cRA) plus 1,25(OH)₂D₃ inhibited proliferation of THP-1 and HL60 cells and increased myeloid differentiation markers including nitroblue tetrazolium reducing activity and expression of CD14 and CD11b. ATRA and the synthetic retinoic acid receptor agonist Am80 exhibited similar effects in combination with 1,25(OH)₂D₃ but less effectively than 9cRA, while the retinoid X receptor agonist HX630 was not effective. 9cRA plus 1,25(OH)₂D₃ effectively increased expression of M2 macrophage marker genes, such as CD163, ARG1 and IL10, increased surface CD163 expression, and induced interleukin-10 secretion in myeloid leukemia cells, while 9cRA alone had weaker effects on these phenotypes and 1,25(OH)₂D₃ was not effective. Taken together, our results demonstrate selective induction of M2 macrophage markers in human myeloid leukemia cells by combined treatment with 9cRA and 1,25(OH)₂D₃.

Lithocholic acid derivatives act as selective vitamin D receptor modulators without inducing hypercalcemia

1alpha,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], a vitamin D receptor (VDR) ligand, regulates calcium homeostasis and also exhibits noncalcemic actions on immunity and cell differentiation. In addition to disorders of bone and calcium metabolism, VDR ligands are potential therapeutic agents in the treatment of immune disorders, microbial infections, and malignancies. Hypercalcemia, the major adverse effect of vitamin D(3) derivatives, limits their clinical application. The secondary bile acid lithocholic acid (LCA) is an additional physiological ligand for VDR, and its synthetic derivative, LCA acetate, is a potent VDR agonist. In this study, we found that an additional derivative, LCA propionate, is a more selective VDR activator than LCA acetate. LCA acetate and LCA propionate induced the expression of the calcium channel transient receptor potential vanilloid type 6 (TRPV6) as effectively as that of 1alpha,25-dihydroxyvitamin D(3) 24-hydroxylase (CYP24A1), whereas 1,25(OH)(2)D(3) was more effective on TRPV6 than on CYP24A1 in intestinal cells. In vivo experiments showed that LCA acetate and LCA propionate effectively induced tissue VDR activation without causing hypercalcemia. These bile acid derivatives have the ability to function as selective VDR modulators.

Inhibition of lung carcinogenesis by 1alpha,25-dihydroxyvitamin D3 and 9-cis retinoic acid in the A/J mouse model: evidence of retinoid mitigation of vitamin D toxicity

9-cis-Retinoic acid (9cRA) and 1alpha,25-dihydroxyvitamin D3 (1,25D) show promise as potential chemopreventive agents. We examined 9cRA and 1,25D, alone and in combination, for their potential to inhibit carcinogen (NNK)-induced lung carcinogenesis in A/J mice. A/J mice (n=14/group) were treated with 9cRA (7.5, 15, or 30 mg/kg diet), 1,25D (2.5 or 5.0 microg/kg diet), or a combination of 9cRA (15 mg/kg diet) plus 1,25D (2.5 microg/kg diet) for 3 weeks before and 17 weeks after carcinogen injection. Lung tumor incidence, tumor multiplicity, plasma 1,25D levels and kidney expression of vitamin D 24-hydroxylase (CYP24) were determined. Compared to carcinogen-injected controls, mice receiving 9cRA supplementation had significantly lower tumor multiplicity at all doses (decreased 68-85%), with body weight loss at the higher doses of 9cRA. Mice receiving 1,25D supplementation had significantly lower tumor incidence (decreased 36 and 82%) and tumor multiplicity (decreased 85 and 98%), but experienced significant body weight loss, kidney calcium deposition, elevated kidney CYP24 expression and decreased fasting plasma 1,25D levels. Although, there was no apparent influence on chemopreventive efficacy, addition of 9cRA to 1,25D treatment effectively prevented the weight loss and kidney calcification associated with 1,25D treatment alone. These data demonstrate that 9cRA and 1,25D, alone or combined, can inhibit lung tumor promotion in the A/J mouse model. Combining 1,25D with 9cRA has the potential to mitigate the toxicity of 1,25D, while preserving the significant effect of 1,25D treatment against lung carcinogenesis. The underlying mechanism behind this effect does not appear to be related to retinoid modulation of vitamin D catabolism.

Selective activation of vitamin D receptor by lithocholic acid acetate, a bile acid derivative

The vitamin D receptor (VDR), a member of the nuclear receptor superfamily, mediates the biological actions of the active form of vitamin D, 1alpha,25-dihydroxyvitamin D(3). It regulates calcium homeostasis, immunity, cellular differentiation, and other physiological processes. Recently, VDR was found to respond to bile acids as well as other nuclear receptors, farnesoid X receptor (FXR) and pregnane X receptor (PXR). The toxic bile acid lithocholic acid (LCA) induces its metabolism through VDR interaction. To elucidate the structure-function relationship between VDR and bile acids, we examined the effect of several LCA derivatives on VDR activation and identified compounds with more potent activity than LCA. LCA acetate is the most potent of these VDR agonists. It binds directly to VDR and activates the receptor with 30 times the potency of LCA and has no or minimal activity on FXR and PXR. LCA acetate effectively induced the expression of VDR target genes in intestinal cells. Unlike LCA, LCA acetate inhibited the proliferation of human monoblastic leukemia cells and induced their monocytic differentiation. We propose a docking model for LCA acetate binding to VDR. The development of VDR agonists derived from bile acids should be useful to elucidate ligand-selective VDR functions.

Enhancement by other compounds of the anti-cancer activity of vitamin D(3) and its analogs

Differentiation therapy holds promise as an alternative to cytotoxic drug therapy of cancer. Among compounds under scrutiny for this purpose is the physiologically active form of vitamin D(3), 1,25-dihydroxyvitamin D(3), and its chemically modified derivatives. However, the propensity of vitamin D(3) and its analogs to increase the levels of serum calcium has so far precluded their use in cancer patients except for limited clinical trials. This article summarizes the range of compounds that have been shown to increase the differentiation-inducing and antiproliferative activities of vitamin D(3) and its analogs, and discusses the possible mechanistic basis for this synergy in several selected combinations. The agents discussed include those that have differentiation-inducing activity of their own that is increased by combination with vitamin D(3) or analogs, such as retinoids or transforming growth factor-beta and plant-derived compounds and antioxidants, such as curcumin and carnosic acid. Among other compounds discussed here are dexamethasone, nonsteroidal anti-inflammatory drugs, and inhibitors of cytochrome P450 enzymes, for example, ketoconazole. Thus, recent data illustrate that there are extensive, but largely unexplored, opportunities to develop combinatorial, differentiation-based approaches to chemoprevention and chemotherapy of human cancer.

Future perspectives for acute promyelocytic leukemia therapy

Acute promyelocytic leukemia (APL) is the first leukemia where targeted therapy proved to be effective, as only patients with retinoic acid-sensitive APL leukemic-clones responded in vivo. The future perspectives of APL therapy should persist in targeting either the APL's cell-specific characteristics concerning differentiation, cell cycle, and survival potentials, or the molecular markers specific to the APL clone. Converging recent advances in cellular therapy and in scientific concepts of cell differentiation should aim toward a possible cure of APL.

Kaposi sarcoma is a therapeutic target for vitamin D3receptor agonist

Kaposi sarcoma (KS) is responsive to a number of different steroid hormones, such as glucocorticoids and retinoids. An active metabolite of vitamin D, 1α,25 dihydroxyvitamin D3, was used to study the effect of this steroid hormone in KS. Steroid hormones exert their effect through their cognate nuclear receptors, which for vitamin D metabolites is the vitamin D receptor (VDR). It was first shown that KS cell lines and primary tumor tissue express high levels of VDR, whereas endothelial cells had minimal expression and fibroblasts had no expression. Second, KS cell growth was inhibited by VDR agonist 1α,25 dihydroxyvitamin D3 with a 50% inhibitory concentration of 5 × 10 −8 mol/L, whereas endothelial cells and fibroblast cells showed no response. Studies on the mechanism of KS tumor growth inhibition by 1α,25 dihydroxyvitamin D3 showed that production of autocrine growth factors interleukin (IL)-6 and IL-8 was reduced in a dose-dependent manner, whereas no effect was observed on vascular endothelial growth factor and basic fibroblast growth factor. Transcription initiated at the IL-6 promoter was repressed by VDR agonist. The DNA sequences required to mediate this repression were localized to nucleotides −225/−110 in the 5′-flanking region. The antitumor activity of VDR agonists was also confirmed in KS tumor xenograft and after topical application in patients with KS. 1α,25 Dihydroxyvitamin D3 and its analogs may thus be candidates for clinical development in KS.

Kaposi sarcoma is a therapeutic target for vitamin D3receptor agonist

Kaposi sarcoma (KS) is responsive to a number of different steroid hormones, such as glucocorticoids and retinoids. An active metabolite of vitamin D, 1α,25 dihydroxyvitamin D3, was used to study the effect of this steroid hormone in KS. Steroid hormones exert their effect through their cognate nuclear receptors, which for vitamin D metabolites is the vitamin D receptor (VDR). It was first shown that KS cell lines and primary tumor tissue express high levels of VDR, whereas endothelial cells had minimal expression and fibroblasts had no expression. Second, KS cell growth was inhibited by VDR agonist 1α,25 dihydroxyvitamin D3 with a 50% inhibitory concentration of 5 × 10 −8 mol/L, whereas endothelial cells and fibroblast cells showed no response. Studies on the mechanism of KS tumor growth inhibition by 1α,25 dihydroxyvitamin D3 showed that production of autocrine growth factors interleukin (IL)-6 and IL-8 was reduced in a dose-dependent manner, whereas no effect was observed on vascular endothelial growth factor and basic fibroblast growth factor. Transcription initiated at the IL-6 promoter was repressed by VDR agonist. The DNA sequences required to mediate this repression were localized to nucleotides −225/−110 in the 5′-flanking region. The antitumor activity of VDR agonists was also confirmed in KS tumor xenograft and after topical application in patients with KS. 1α,25 Dihydroxyvitamin D3 and its analogs may thus be candidates for clinical development in KS.

Role of vitamin D3 receptor in the synergistic differentiation of WEHI-3B leukemia cells by vitamin D3 and retinoic acid

WEHI-3B D- cells differentiate in response to 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) but not to all-trans-retinoic acid (RA) or other inducing agents. Combinations of RA with 1,25-(OH)2D3 interact to produce synergistic differentiation of WEHI-3B D- cells. To determine factors involved in the synergistic interaction, expression of the 1,25-(OH)2D3 receptor (VDR) and retinoid receptors, RARalpha and RXRalpha, was measured. No VDR was detected in untreated WEHI-3B D- cells; however, RA and 1,25-(OH)2D3 when used as single agents caused a slight induction of the VDR and in combination produced a marked increase in the VDR. In contrast, no changes in RARalpha and RXRalpha were initiated by these compounds. An RAR-selective agonist combined with 1,25-(OH)2D3 produced synergistic differentiation of WEHI-3B D- cells, whereas an RXR-selective agonist did not. To gain information on the role of the VDR in the synergistic interaction, the VDR gene was transferred into WEHI-3B D+ cells, in which no VDR was detected and no synergism was produced. Expression of the VDR conferred differentiation responsiveness to 1,25-(OH)2D3 in WEHI-3B D+ cells. These findings suggest that (a) induction of VDR expression is a key component in the synergistic differentiation induced by 1,25-(OH)2D3 and RA and (b) RAR and not RXR must be activated for enhanced induction of the VDR and for the synergistic differentiation produced by RA and 1, 25-(OH)2D3.