Vitamin K2 therapy for myelodysplastic syndromes (MDS) and post-MDS acute myeloid leukemia: information through a questionnaire survey of multi-center pilot studies in Japan

Vitamin K2 in Health and Disease: A Clinical Perspective

Vitamins are essential organic compounds that vary widely in chemical structure and are vital in small quantities for numerous biochemical and biological functions. They are critical for metabolism, growth, development and maintaining overall health. Vitamins are categorised into two groups: hydrophilic and lipophilic. Vitamin K (VK), a lipophilic vitamin, occurs naturally in two primary forms: phylloquinone (VK1), found in green leafy vegetables and algae, and Menaquinones (VK2), present in certain fermented and animal foods and widely formulated in VK supplements. This review explores the possible factors contributing to VK deficiency, including dietary influences, and discusses the pharmacological and therapeutic potential of supplementary VK2, examining recent global clinical studies on its role in treating diseases such as osteoporosis, osteoarthritis, rheumatoid arthritis, cardiovascular disease, chronic kidney disease, diabetes, neurodegenerative disorders and cancers. The analysis includes a review of published articles from multiple databases, including Scopus, PubMed, Google Scholar, ISI Web of Science and CNKI, focusing on human studies. The findings indicate that VK2 is a versatile vitamin essential for human health and that a broadly positive correlation exists between VK2 supplementation and improved health outcomes. However, clinical data are somewhat inconsistent, highlighting the need for further detailed research into VK2's metabolic processes, biomarker validation, dose-response relationships, bioavailability and safety. Establishing a Recommended Daily Intake for VK2 could significantly enhance global health.

The Efficacy of Vitamin K, A Member Of Naphthoquinones in the Treatment of Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Redox dysregulation originating from metabolic alterations in cancer cells contributes to their proliferation, invasion, and resistance to therapy. Conversely, these features represent a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. Amongst them, Vitamin K (VitK) carries the potential against cancer stem cells, in addition to the rest of tumor mass.

OBJECTIVES

To assess the possible benefits and safety of VitK for cancer treatment using a systematic review and meta-analysis with a mixed-methods approach.

METHODS

We performed a systematic search on several electronic databases for studies comparing VitK treatment with and without combination to the control groups. For quantitative studies, fully or partially reported clinical outcomes such as recurrence rates, survival, overall response and adverse reactions were assessed. For qualitative studies, a narrative synthesis was accomplished.

RESULTS

Our analysis suggested that the clinical outcome of efficacy, the pooled hazard ratio for progression-free survival, and the pooled relative risk for overall survival, and overall response were significantly higher in the VitK therapy group compared to the placebo group (p<0.05). We did not observe any significant difference in the occurrence of adverse events between groups. Among qualitative studies, VitK treatment targeting myelodysplastic syndrome and advanced solid tumors resulted in 24.1% and 10% of clinical response, respectively.

CONCLUSION

VitK not only exerts antitumor effects against a wide range of tumor types, but it also has excellent synergism with other therapeutic agents.

Menatetrenone facilitates hematopoietic cell generation in a manner that is dependent on human bone marrow mesenchymal stromal/stem cells

Vitamin K2 in the form of menatetrenone has clinical benefits for osteoporosis and cytopenia. Given the dominant role of mesenchymal-osteolineage cells in the regulation of hematopoiesis, we investigated whether menatetrenone alters the hematopoiesis-supportive capability of human bone marrow mesenchymal stromal/stem cells (BM-MSCs). Menatetrenone up-regulated fibronectin protein expression in BM-MSCs without affecting their proliferation and differentiation capabilities. In addition, menatetrenone treatment of BM-MSCs enhanced generation of the CD34⁺ cell population in co-cultures through acceleration of the cell cycle. This effect was associated with cell-cell interactions mediated by VLA-4 and fibronectin. This proposal was supported by cytokine array and quantitative real-time PCR analyses, in which there were no significant differences between the expression levels of hematopoiesis-associated soluble factors in naïve and menatetrenone-treated BM-MSCs. Profiling of hematopoietic cells in co-cultures with menatetrenone-treated BM-MSCs demonstrated that they included significantly more CD34⁺CD38⁺ hematopoietic progenitor cells and cells skewed toward myeloid and megakaryocytic lineages than those in co-cultures with untreated BM-MSCs. Notably, myelodysplastic syndrome-derived cells were induced to undergo apoptosis when co-cultured with BM-MSCs, and this effect was enhanced by menatetrenone. Overall, our findings indicate that pharmacological treatment with menatetrenone bestows a unique hematopoiesis-supportive capability on BM-MSCs, which may contribute to the clinical improvement of cytopenia.

Research progress on the anticancer effects of vitamin K2

Despite the availability of multiple therapeutic methods for patients with cancer, the long-term prognosis is not satisfactory in a number of different cancer types. Vitamin K2 (VK2), which exerts anticancer effects on a number of cancer cell lines, is considered to be a prospective novel agent for the treatment of cancer. The present review aims to summarize the results of studies in which VK2 was administered either to patients with cancer or animals inoculated with cancerous cells, particularly investigating the inhibitory effects of VK2 on cancerous cells, primarily involving cell-cycle arrest, cell differentiation, apoptosis, autophagy and invasion. The present review summarizes evidence stating that treatment with VK2 could positively inhibit the growth of cancer cells, making it a potentially useful approach for the prevention and clinical treatment of cancer. Additionally, the combination treatment of VK2 and established chemotherapeutics may achieve better results, with fewer side effects. Therefore, more attention should be paid to the effects of micronutrients on tumors.

Vitamin K homologs as potential biomarkers for disease activity in patients with rheumatoid arthritis

The aim of this study was to evaluate the possible role of vitamin K homologs as potential biomarkers for disease activity in patients with rheumatoid arthritis (RA). In this study, 42 patients with RA and 40 healthy controls were enrolled. Serum levels of vitamin K homologs were measured using a high-performance liquid chromatography-fluorescence method. Different biochemical and clinical markers for disease activity were measured and correlated with serum levels of vitamin K homologs. There were no significant differences between RA patients and healthy subjects in demographic data. Patients with RA showed significantly higher levels of biochemical markers compared with healthy subjects (p < 0.001). These markers included rheumatoid factor (RF), anticyclic citrullinated polypeptide (anti-CCP), undercarboxylated osteocalcin (ucOC), matrix metalloproteinase (MMP-3), C-reactive protein (CRP), and disease activity score assessing 28 joints with erythrocyte sedimentation rate (DAS28-ESR). In addition, serum levels of vitamin K homologs were reduced in RA patients, and the levels of menaquinone-4 (MK-4) and menaquinone-7 (MK-7) were moderately to strongly inversely correlated with the clinical articular features in RA patients, whereas phylloquinone (PK) levels were weakly correlated. Serum levels of MK-4, MK-7 and PK were strongly inversely correlated with ucOC, MMP-3 and DAS28-ESR in RA patients. In contrast, serum levels of MK-4, MK-7 and PK were weakly correlated with CRP, RF and anti-CCP. These results suggest that serum levels of vitamin K homologs may be considered as potential biomarkers for disease activity. In addition, the results confirm the role of vitamin K deficiency in the etiology of RA.

Vitamin K: novel molecular mechanisms of action and its roles in osteoporosis

Vitamin K is a fat-soluble vitamin, which is involved in blood coagulation mediated by maintaining the activity of coagulation factors in the liver. Vitamin K also has extrahepatic actions and has been shown to prevent bone fractures in clinical studies. In addition, epidemiological studies suggest that a lack of vitamin K is associated with several geriatric diseases, including osteoporosis, osteoarthritis, dementia and arteriosclerosis. It has also been shown that vitamin K contributes to the prevention and treatment of some kinds of malignancies. Recently, we discovered a novel role for vitamin K as a ligand of the nuclear receptor, steroid and xenobiotic receptor (SXR), and its murine ortholog, pregnane X receptor (PXR). In addition to its established roles as a cofactor of γ-glutamyl carboxylase (GGCX) in mediating post-transcriptional modifications, vitamin K has a different mode of action mediated by transcriptional regulation of SXR/PXR target genes. Analysis of bone tissue from PXR-deficient mice showed that the bone protective effects of vitamin K are partially mediated by SXR/PXR-dependent signaling. The discoveries of a novel mode of vitamin K action have opened up new possibilities that vitamin K might be useful for prevention or treatment of a variety of diseases that affect the geriatric population.

Vitamin K2 covalently binds to Bak and induces Bak-mediated apoptosis

Vitamin K2 (VK2, menaquinone) is known to have anticancer activity in vitro and in vivo. Although its effect is thought to be mediated, at least in part, by the induction of apoptosis, the underlying molecular mechanism remains elusive. Here, we identified Bcl-2 antagonist killer 1 (Bak) as a molecular target of VK2-induced apoptosis. VK2 directly interacts with Bak and induces mitochondrial-mediated apoptosis. Although Bak and Bcl-2-associated X protein (Bax), another member of the Bcl-2 family, are generally thought to be functionally redundant, only Bak is necessary and sufficient for VK2-induced cytochrome c (cyt c) release and cell death. Moreover, VK2-2,3 epoxide, an intracellular metabolite of VK2, was shown to covalently bind to the cysteine-166 residue of Bak. Several lines of evidence suggested that the covalent attachment of VK2 is critical for apoptosis induction. Thus this study reveals a specific role for Bak in mitochondria-mediated apoptosis. This study also provides insight into the anticancer effects of VK2 and suggests that Bak may be a potential target of cancer therapy.

Vitamin K2 administration is associated with decreased disease activity in patients with rheumatoid arthritis

OBJECTIVES

Vitamin K2 (VitK2) is reported to induce not only bone mineralization of human osteoblasts and apoptosis of osteoclasts, but also apoptosis of rheumatoid arthritis (RA) synovial cells, while its clinical effect on disease activity of RA remains unknown.

METHODS

158 female RA patients (mean age 62.5 years) who had not been treated with warfarin, biologics, or teriparatide were enrolled in this study. VitK2 (45 mg/day) was administered in 70 patients with a serum undercarboxylated osteocalcin level of >4.5 ng/ml or with decreased bone mineral density in spite of the treatment with other anti-osteoporosis medications, regardless of RA disease activity. A longitudinal study was conducted in 52 patients who were additionally treated with VitK2 without changing their other medications for three months.

RESULTS

In the cross-sectional study, as compared to the VitK2-naïve group (n = 88), the VitK2-treated group (n = 70) showed lower serum CRP (1.7 ± 0.2 vs. 0.5 ± 0.1 mg/dl; P < 0.001), MMP-3 (220.4 ± 21.9 vs. 118.0 ± 14.4 ng/ml; P < 0.001), and DAS28-CRP (2.9 ± 0.1 vs. 2.4 ± 0.1; P < 0.05). In the longitudinal study, patients who were additionally treated with VitK2 showed significant decreases in serum CRP (1.1 ± 0.2 to 0.6 ± 0.2 mg/dl; P < 0.001), MMP-3 (160.1 ± 25.6 to 125.0 ± 17.8 ng/ml; P < 0.05), and DAS28-CRP (3.1 ± 0.2 to 2.4 ± 0.1; P < 0.001).

CONCLUSIONS

VitK2 may have the potential to improve disease activity besides osteoporosis in RA.

Vitamin K2 modulates differentiation and apoptosis of both myeloid and erythroid lineages

Vitamin K2 (VK2) can improve cytopenia in some patients with myelodysplastic syndrome (MDS). Although it is well known that VK2 induces differentiation and apoptosis in acute myeloid leukemia (AML) cell lines, little is known about its effect on normal hematopoietic progenitors. The effects of VK2 on primary myeloid and erythroid progenitors were examined. Mobilized CD34-positive cells from peripheral blood were used for the examination of myeloid lineage cells, and erythroid progenitors purified from peripheral blood were used for erythroid lineage cells. VK2 upregulated the expressions of myeloid markers CD11b and CD14, and increased the mRNA expression levels of CCAAT/enhancer binding protein-α (C/EBPα) and PU.1 in myeloid progenitors. In erythroid progenitors, VK2 did not show a significant effect on differentiation. However, VK2 exhibited an anti-apoptotic effect on erythroid progenitors under erythropoietin depletion. This anti-apoptotic effect was restricted to normal erythroid progenitors and was not shown in erythroleukemic cell line AS-E2. Steroid and xenobiotic receptor (SXR), which was recently identified as a receptor of VK2, was expressed on myeloid progenitors, and the SXR agonist rifampicin (RIF) also upregulated CD11b and CD14 expressions on myeloid progenitors. These results indicate that SXR is involved in the effect of VK2 on myeloid progenitors. The major effect of VK2 on myeloid progenitors was promoting differentiation, whereas its anti-apoptotic effect seemed to be dominant in erythroid progenitors. Although the detailed mechanism of VK2's effect on differentiation or apoptosis of hematopoietic progenitors remains unknown, the effect of VK2 therapy in patients with MDS could be partly explained by these mechanisms.

Synergistic growth inhibition in HL-60 cells by the combination of acyclic retinoid and vitamin K2

PURPOSE

The aim of this study was to assess the effects of acyclic retinoid (ACR) and vitamin K(2) (VK(2)) in HL-60 cells.

METHODS

We used HL-60 cells, and the Trypan Blue dye exclusion method was used for cell proliferation assays. For detection of apoptosis, the Annexin V-binding capacity of treated cells was examined by flow cytometry. To evaluate the cell cycle, we used a FITC BrdU Flow KIT and flow cytometry. Total extracted and equivalent amounts of protein were examined by Western blotting using specific antibodies.

RESULTS

ACR and VK(2) dose dependently inhibited the proliferation of HL-60 cells. These two agents in combination synergistically inhibited cell growth and induced apoptosis. VK(2) inhibited activation of the Ras/MAPK signaling pathway, and ACR plus VK(2) cooperatively inhibited phosphorylation of RXRα and the growth of HL-60 cells. Moreover, ACR and VK(2) induced increases in G0/G1 phase HL-60 cells, alone and synergistically in combination.

CONCLUSION

The synergistic effects of ACR and VK(2) on HL-60 cells may provide a novel strategy for treating leukemia.

Multicenter phase II trial of vitamin K(2) monotherapy and vitamin K(2) plus 1alpha-hydroxyvitamin D(3) combination therapy for low-risk myelodysplastic syndromes

We performed an open-labeled single-arm prospective phase II clinical trial of vitamin K(2) (menatetrenone: VK2) monotherapy and VK2 plus 1alpha-hydroxyvitamin D(3) (alfacalcidol: VD3) combination therapy for myelodysplastic syndromes (MDS) with refractory anemia and refractory cytopenia with multilineage dysplasia, having either low or intermediate-1 risks of the IPSS. The overall response rate to VK2 monotherapy (45mg/day) after 16 weeks was 13% (5/38) including 4 cases with improvement of both anemia and thrombocytopenia and 1 case with thrombocytopenia. We then enrolled and evaluated 20 out of 33 VK2-monotherapy non-responders for VK2 plus VD3 (0.75microg/day) combination therapy. The overall response rate at 16 weeks after initiation of VK2 plus VD3 was 30% (6/20). HI for hemoglobin (Hb) was observed in 6 out of 11 patients (55%) and for thrombocytopenia in 3 out of 11 patients (27%), respectively. No HI was observed for neutropenia in VK2 monotherapy and VK2 plus VD3 combination therapy. It was suggested that IPSS scores and absolute neutrophil counts positively correlated, and Hb levels inversely correlated with the response to VK2 plus VD3 combination therapy. Our study demonstrated that VK2 plus VD3 combination therapy appears to be promising for improvement of anemia and thrombocytopenia with low/intermediate-1 MDS.

Carcinogenesis and chemoprevention of biliary tract cancer in pancreaticobiliary maljunction

Pancreaticobiliary maljunction (PBM) is a high risk factor for biliary tract cancer. In PBM, since the pancreatic duct and bile duct converge outside the duodenal wall beyond the influence of the sphincter of Oddi, pancreatic juice and bile are constantly mixed, producing a variety of harmful substances. Because of this, the biliary mucosa is repeatedly damaged and repaired, which causes an acceleration of cell proliferative activity and multiple gene mutations. Histological changes such as hyperplasia, metaplasia, and dysplasia ultimately result in a high incidence of carcinogenesis. In a nationwide survey by the Japanese Study Group on PBM, coexisting biliary tract cancer was detected in 278 of the 1627 registered cases of PBM (17.1%). Of these cases, in those with dilatation of the extrahepatic bile duct, cancer was often detected not only in the gallbladder but also in the bile ducts. More than 90% of cancer cases without dilatation of the extrahepatic bile duct develop in the gallbladder. Standard treatment for PBM is a cholecystectomy and resection of the extrahepatic bile duct. However, cholecystectomy alone is performed at nearly half of institutions in Japan. Conversely, reports of carcinogenesis in the remnant bile duct or pancreas after diversion surgery are steadily increasing. One of the causes for this is believed to be an accumulation of gene mutations which were present before surgery. Anticancer drugs are ineffective in preventing such carcinogenesis following surgery, thus the postoperative administration of chemopreventive agents may be necessary.

Vitamin K supplementation in postmenopausal women with osteopenia (ECKO trial): a randomized controlled trial

BACKGROUND

Vitamin K has been widely promoted as a supplement for decreasing bone loss in postmenopausal women, but the long-term benefits and potential harms are unknown. This study was conducted to determine whether daily high-dose vitamin K1 supplementation safely reduces bone loss, bone turnover, and fractures.

METHODS AND FINDINGS

This single-center study was designed as a 2-y randomized, placebo-controlled, double-blind trial, extended for earlier participants for up to an additional 2 y because of interest in long-term safety and fractures. A total of 440 postmenopausal women with osteopenia were randomized to either 5 mg of vitamin K1 or placebo daily. Primary outcomes were changes in BMD at the lumbar spine and total hip at 2 y. Secondary outcomes included changes in BMD at other sites and other time points, bone turnover markers, height, fractures, adverse effects, and health-related quality of life. This study has a power of 90% to detect 3% differences in BMD between the two groups. The women in this study were vitamin D replete, with a mean serum 25-hydroxyvitamin D level of 77 nmol/l at baseline. Over 2 y, BMD decreased by -1.28% and -1.22% (p = 0.84) (difference of -0.06%; 95% confidence interval [CI] -0.67% to 0.54%) at the lumbar spine and -0.69% and -0.88% (p = 0.51) (difference of 0.19%; 95% CI -0.37% to 0.75%) at the total hip in the vitamin K and placebo groups, respectively. There were no significant differences in changes in BMD at any site between the two groups over the 2- to 4-y period. Daily vitamin K1 supplementation increased serum vitamin K1 levels by 10-fold, and decreased the percentage of undercarboxylated osteocalcin and total osteocalcin levels (bone formation marker). However, C-telopeptide levels (bone resorption marker) were not significantly different between the two groups. Fewer women in the vitamin K group had clinical fractures (nine versus 20, p = 0.04) and fewer had cancers (three versus 12, p = 0.02). Vitamin K supplements were well-tolerated over the 4-y period. There were no significant differences in adverse effects or health-related quality of life between the two groups. The study was not powered to examine fractures or cancers, and their numbers were small.

CONCLUSIONS

Daily 5 mg of vitamin K1 supplementation for 2 to 4 y does not protect against age-related decline in BMD, but may protect against fractures and cancers in postmenopausal women with osteopenia. More studies are needed to further examine the effect of vitamin K on fractures and cancers.

TRIAL REGISTRATION

ClinicalTrials.gov (#NCT00150969) and Current Controlled Trials (#ISRCTN61708241).

A dog with acute myelomonocytic leukemia

A three-year-old dog with marked leukocytosis, lymphadenopathy, and diarrhea showed an increase in unidentified blasts in the peripheral blood, and they were proliferated in the bone marrow. The dog was diagnosed with myelomonocytic leukemia (M4) because the blast cells were demonstrated by cytochemical staining to be both myeloid and monocytic cells. Although the dog was treated with a multi-combination chemotherapy and induction therapy using vitamin K2, it died on day 47 after the first admission. This case is the first report of M4 in Japan.

Anti-arthritis effects of vitamin K(2) (menaquinone-4)--a new potential therapeutic strategy for rheumatoid arthritis

Vitamin K(2) (menaquinone-4, MK-4) has been reported to induce apoptosis in hepatocellular carcinoma, leukemia and myelodysplastic syndrome cell lines. The effects of MK-4 on the development of arthritis have never been addressed thus far. In the present study, we investigated the effect of MK-4 upon the proliferation of rheumatoid synovial cells and the development of arthritis in collagen-induced arthritis. We analyzed the effect of MK-4 on the proliferation of fibroblast-like synoviocytes using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The pro-apoptotic effect of MK-4 upon fibroblast-like synoviocytes was investigated with annexin V staining and DNA fragmentation and caspase 3/7 assays. Moreover, we analyzed the effect of MK-4 on the development of collagen-induced arthritis in female dark agouti rats. Our results indicated that MK-4 inhibited the proliferation of fibroblast-like synoviocytes and the development of collagen-induced arthritis in a dose-dependent manner. We conclude that MK-4 may represent a new agent for the treatment of rheumatoid arthritis in the setting of combination therapy with other disease-modifying antirheumatic drugs.

Regression of hepatocellular carcinoma during vitamin K administration

An 85-year-old man with HCV infection and diabetes mellitus was diagnosed as having hepatocellular carcinoma (HCC, 13 cm in diameter) based on high serum alpha-fetoprotein (AFP), AFP-L3, and des-γ-carboxy prothrombin levels as well as typical enhancement pattern on contrast-enhanced CT. The patient did not receive any interventional treatments because of advanced age and the advanced stage of HCC. He chose to take vitamin K, which was reported to suppress the growth of HCC in vitro. Three months after starting vitamin K, all three tumor markers were normalized and HCC was markedly regressed, showing no enhancement in the early arterial phase on CT. Here we present the report describing the regression of HCC during the administration of vitamin K.

Assessment of the international prognostic scoring system for determining chemotherapeutic indications in myelodysplastic syndrome: Japanese retrospective multicenter study

To standardize a rational therapeutic strategy of chemotherapy using the International Prognostic Scoring System (IPSS), we retrospectively analyzed 292 high-risk myelodysplastic syndrome (MDS) patients in 20 hospitals in Japan. Results of multivariate analysis of the data on patients who received all types of chemotherapy indicated that poor cytogenetics as shown by the IPSS was the only significant risk factor (P = .047). We then focused on the IPSS composition of each patient. The intermediate 2 (Int-2) category consisted of a heterogeneous group. We attempted to subdivide the category into Int-2A and Int-2B. Patients with good or intermediate cytogenetics had > or = 5% bone marrow (BM) blasts (Int-2A), and most of the other patients had poor cytogenetics and < or = 10% BM blasts (Int-2B). In the Int-2B category, overall survival for patients who received chemotherapy was significantly worse than for those who did not receive chemotherapy (P = .005). Most patients in the High category who had the diagnosis of MDS according to the World Health Organization classification had poor overall survival with or without chemotherapy. We propose the Int-2B and High categories may be considered possible high risk, whereas all patients in the Int-2A category and patients with more than 5% BM blasts in the Int-1 category may be categorized as being at possible intermediate risk. Our proposition may be useful for developing a chemotherapeutic strategy for patients with MDS in Japan.

[Basic studies for the development of anticancer, antidementia, and taste modifier drugs]

We developed various types of differentiation- and apoptosis-inducing agents against tumor cells and also studied the function and structure of synucleins and taste modifiers. Differentiation- and apoptosis-inducing agents are classified into DNA-damaging agents, Na(+), K(+)-ATPase inhibitors, agents affecting the redox states of tumor cells, agents affecting signal transduction pathways, isoprenoid compounds, and ATP-noncompetitive tyrosine kinase inhibitors. These include camptothecin, etoposide, cisplatin, transplantin, bufalin, arsenic trioxide, costunolide, C(2)- ceramide, daidzein, geranylgeranylacetone, geranylgeraniol, vitamin K(2), sophoranone, and beta-hydroxyisovalerylshikonin. The mechanisms of action of these differentiation- and apoptosis-inducing agents are described. The structure and function of synucleins are also reviewed for the development of potential antidementia agents. In addition, the structures of three purified taste modifiers are described.

Combination of 22-oxa-1,25-dihydroxyvitamin D(3), a vitamin D(3) derivative, with vitamin K(2) (VK2) synergistically enhances cell differentiation but suppresses VK2-inducing apoptosis in HL-60 cells

We originally reported that vitamin K(2) (VK2) effectively induces apoptosis in various types of primary cultured leukemia cells and leukemia cell lines in vitro. In addition, VK2 was shown to induce differentiation of leukemia cells when the cells were resistant against VK2-inducing apoptosis. A novel synthetic vitamin D(3)derivative, 22-oxa-1,25-dihydroxyvitamin D(3) (OCT: oxacarcitriol) shows a more potent differentiation-inducing ability among myeloid leukemia cells in vitro with much lesser extent of the induction of hypercalcemia in vivo as compared to the effects of 1alpha,25(OH)(2)D(3). In the present study, we focused on the effects of a combination of OCT plus VK2 on leukemia cells. Treatment of HL-60 cells with OCT for 72 h induces monocytic differentiation. A combination of OCT plus VK2 dramatically enhances monocytic differentiation as assessed by morphologic features, positivity for non-specific esterase staining, and cell surface antigen expressions. This combined effect far exceeds the maximum differentiation induction ability at the optimal concentrations of either OCT or VK2 alone. In addition, pronounced accumulation of the cells in the G0/G1 phase is observed by combined treatment with OCT plus VK2 as compared with each vitamin alone. In contrast to cell differentiation, caspase-3 activation and apoptosis induction in response to VK2 are significantly suppressed in the presence of OCT in HL-60 cells. These data suggest that monocytic differentiation and apoptosis induction of HL-60 cells are inversely regulated. Furthermore, pronounced induction of differentiation by combined treatment with VK2 plus OCT was also observed in four out of six cases of primary cultured acute myeloid leukemia cells in vitro, suggesting that VK2 plus OCT might be a potent combination for the differentiation-based therapy for acute myeloid leukemias.

Apoptosis/differentiation-inducing effects of vitamin K2 on HL-60 cells: dichotomous nature of vitamin K2 in leukemia cells

We originally reported that vitamin K2 (VK2) analogs, including menaquinone 4 (MK4) but not vitamin K1, effectively induce apoptosis in various types of primary cultured leukemia cells and leukemia cell lines in vitro. It has also been reported by others that VK2 showed the differentiation-inducing activity in leukemia cell lines. To investigate the discrepancy between apoptosis- and differentiation-inductions of leukemia cells by VK2 treatment, we used bcl-2 gene transfected HL-60 cells (HL-60-bcl-2) which resulted in five-fold over-expression of BCL-2 protein, and then compared the effects of MK4 to the control HL-60-neo cells. Seventy-two hours of exposure to various concentrations of MK4 resulted in growth inhibition of these cells in a dose-dependent manner (0.1-50 microM), however, HL-60-bcl-2 was less sensitive against MK4. MK4 potently induced apoptosis of HL-60-neo cells along with the depolarization of mitochondrial membrane potential and caspase-3 activation. Notably, HL-60-bcl-2 was almost completely resistant to apoptosis induction in response to MK4, although cell growth inhibition was still observed. In spite of the abrogation of apoptosis induction, about 90% of HL-60-bcl-2 cells were arrested in the G0/G1 phase within 48 h of exposure to 10 microM of MK4 accompanied by up-modulation of p27KIP1 expression. Concomitantly, HL-60-bcl-2 cells underwent monocytic differentiation. These data suggest that VK2 also shows the differentiation inducing effects on leukemia cells which are resistant against VK2-inducing apoptosis. The dichotomous nature of VK2 against leukemia cells appears to have clinical benefits for the treatment of patients with leukemias and myelodysplastic syndromes.