Vitamin D compounds and myelodysplastic syndrome

Ex vivo drug screening defines novel drug sensitivity patterns for informing personalized therapy in myeloid neoplasms

Precision medicine approaches such as ex vivo drug sensitivity screening (DSS) are appealing to inform rational drug selection in myelodysplastic syndromes (MDSs) and acute myeloid leukemia, given their marked biologic heterogeneity. We evaluated a novel, fully automated ex vivo DSS platform that uses high-throughput flow cytometry in 54 patients with newly diagnosed or treatment-refractory myeloid neoplasms to evaluate sensitivity (blast cytotoxicity and differentiation) to 74 US Food and Drug Administration-approved or investigational drugs and 36 drug combinations. After piloting the platform in 33 patients, we conducted a prospective feasibility study enrolling 21 patients refractory to hypomethylating agents (HMAs) to determine whether this assay could be performed within a clinically actionable time frame and could accurately predict clinical responses in vivo. When assayed for cytotoxicity, ex vivo drug sensitivity patterns were heterogeneous, but they defined distinct patient clusters with differential sensitivity to HMAs, anthracyclines, histone deacetylase inhibitors, and kinase inhibitors (P < .001 among clusters) and demonstrated synergy between HMAs and venetoclax (P < .01 for combinations vs single agents). In our feasibility study, ex vivo DSS results were available at a median of 15 days after bone marrow biopsy, and they informed personalized therapy, which frequently included venetoclax combinations, kinase inhibitors, differentiative agents, and androgens. In 21 patients with available ex vivo and in vivo clinical response data, the DSS platform had a positive predictive value of 0.92, negative predictive value of 0.82, and overall accuracy of 0.85. These data demonstrate the utility of this approach for identifying potentially useful and often novel therapeutic drugs for patients with myeloid neoplasms refractory to standard therapies.

Low serum vitamin D levels are associated with shorter survival after first-line azacitidine treatment in patients with myelodysplastic syndrome and secondary oligoblastic acute myeloid leukemia

BACKGROUND & AIMS

Azacitidine (AZA) therapy has become the recommended first-line treatment for patients with high-risk myelodysplastic syndromes (MDS) and oligoblastic (<30% bone marrow blasts) acute myeloid leukemia (AML). However, improvement of the efficacy of AZA treatment remains a challenge. We retrospectively tested the hypothesis that VitD levels (25-hydroxyvitamin D3) prior to start of first-line AZA therapy are predictive of overall survival (OS) in patients diagnosed with MDS and secondary oligoblastic AML. Furthermore, the antiproliferative effects of AZA in combination with 25-hydroxyvitamin D3 and 1α,25-dihydroxyvitamin D3 were investigated in vitro.

METHODS

A total of 58 patients treated at our center between 2006 and 2014 were analyzed. Serum levels of VitD were quantified using a standard, commercially available 25-hydroxyvitamin D3 chemiluminescent immunoassay. Effects on cell proliferation were assessed using tetrazolium-based MTT assays.

RESULTS

Median serum VitD level prior to AZA treatment was 32.8 nM (range 11.0-101.5 nM). Patient, disease and treatment characteristics did not differ significantly between the low (≤32.8 nM; n = 29) and high (>32.8 nM; n = 29) VitD group. Estimated probability of 2-year OS in the low versus high VitD group was 14% versus 40% (P < 0.05). In multivariable analysis with OS as endpoint, adverse cytogenetics (HR 2.66, P = 0.03) and VitD (per 10 nM decrease, HR 1.68, P = 0.02) were independent predictors of worse survival. In-vitro treatment of myeloid cell lines with AZA in combination with VitD produced synergistic and additive antiproliferative effects. Addition of nanomolar VitD concentrations to AZA resulted in potentiation of AZA activity. Conversely, combination with the VitD antagonist TEI-9647 resulted in inhibition of AZA activity.

CONCLUSIONS

Our study suggests that higher VitD levels were associated with a survival advantage following first-line AZA therapy. Enhanced cytotoxic effects upon combination treatment may contribute to the observed clinical effects. VitD repletion/supplementation during AZA treatment should be explored.

Natural compounds and pharmaceuticals reprogram leukemia cell differentiation pathways

In addition to apoptosis resistance and cell proliferation capacities, the undifferentiated state also characterizes most cancer cells, especially leukemia cells. Cell differentiation is a multifaceted process that depends on complex regulatory networks that involve transcriptional, post-transcriptional and epigenetic regulation of gene expression. The time- and spatially-dependent expression of lineage-specific genes and genes that control cell growth and cell death is implicated in the process of maturation. The induction of cancer cell differentiation is considered an alternative approach to elicit cell death and proliferation arrest. Differentiation therapy has mainly been developed to treat acute myeloid leukemia, notably with all-trans retinoic acid (ATRA). Numerous molecules from diverse natural or synthetic origins are effective alone or in association with ATRA in both in vitro and in vivo experiments. During the last two decades, pharmaceuticals and natural compounds with various chemical structures, including alkaloids, flavonoids and polyphenols, were identified as potential differentiating agents of hematopoietic pathways and osteogenesis.

Perspectives of differentiation therapies of acute myeloid leukemia: the search for the molecular basis of patients' variable responses to 1,25-dihydroxyvitamin d and vitamin d analogs

The concept of differentiation therapy of cancer is ~40 years old. Despite many encouraging results obtained in laboratories, both in vitro and in vivo studies, the only really successful clinical application of differentiation therapy was all-trans-retinoic acid (ATRA)-based therapy of acute promyelocytic leukemia (APL). ATRA, which induces granulocytic differentiation of APL leukemic blasts, has revolutionized the therapy of this disease by converting it from a fatal to a curable one. However, ATRA does not work for other acute myeloid leukemias (AMLs). Since 1,25-dihydroxyvitamin D₃ (1,25D) is capable of inducing monocytic differentiation of leukemic cells, the idea of treating other AMLs with vitamin D analogs (VDAs) was widely accepted. Also, some types of solid cancers responded to in vitro applied VDAs, and hence it was postulated that VDAs can be used in many clinical applications. However, early clinical trials in which cancer patients were treated either with 1,25D or with VDAs, did not lead to conclusive results. In order to search for a molecular basis of such unpredictable responses of AML patients toward VDAs, we performed ex vivo experiments using patient’s blast cells. Experiments were also performed using 1,25D-responsive and 1,25D-non-responsive cell lines, to study their mechanisms of resistance toward 1,25D-induced differentiation. We found that one of the possible reasons might be due to a very low expression level of vitamin D receptor (VDR) mRNA in resistant cells, which can be increased by exposing the cells to ATRA. Our considerations concerning the molecular mechanism behind the low VDR expression and its regulation by ATRA are reported in this paper.

Monocytic differentiation induced by side-chain modified analogs of vitamin D in ex vivo cells from patients with acute myeloid leukemia

The differentiation-inducing potential of side-chain modified analogs of vitamins D, compared to the reference compound, 1,25-dihydroxyvitamin D3, was studied in blast cells from patients with acute myeloid leukemia and in cell lines. Analogs PRI-1906 and PRI-1907 showed increased cell-differentiation activities, PRI-1907 even at a very low concentration. Our study revealed a high variability of individual patients' blasts in their susceptibility to vitamin D analogs. The blasts of the patients with normal karyotype and with mutated NPM1 reacted to analogs with stronger differentiation than the blasts of the remaining patients, while the blasts with mutated FLT3 receptor reacted with weaker differentiation than the remaining blasts.

Regulation of Leukemic Cell Differentiation through the Vitamin D Receptor at the Levels of Intracellular Signal Transduction, Gene Transcription, and Protein Trafficking and Stability

1α,25-Dihydroxyvitamin D₃ (1,25(OH)₂D) exerts its biological activities through vitamin D receptor (VDR), which is a member of the superfamily of steroid receptors, that act as ligand-dependent transcription factors. Ligated VDR in complex with retinoid X receptor (RXR) binds to regulatory regions of 1,25(OH)₂D-target genes. 1,25(OH)₂D is able to induce differentiation of leukemic blasts towards macrophage-like cells. Many different acute myeloid leukemia (AML) cell lines respond to 1,25(OH)₂D by increasing CD14 cell surface receptor, some additionally upregulate CD11b and CD11c integrins. In untreated AML cells VDR protein is present in cytosol at a very low level, even though its mRNA is continuously expressed. Ligation of VDR causes protein stabilization and translocation to the cell nuclei, where it regulates transcription of target genes. Several important groups of genes are regulated by 1,25(OH)₂D in HL60 cells. These genes include differentiation-related genes involved in macrophage function, as well as a gene regulating degradation of 1,25(OH)₂D, namely CYP24A1. We summarize here the data which demonstrate that though some cellular responses to 1,25(OH)₂D in AML cells are transcription-dependent, there are many others which depend on intracellular signal transduction, protein trafficking and stabilization. The final effect of 1,25(OH)₂D action in leukemic cells requires all these acting together.

Vitamin D insufficiency in myeloproliferative neoplasms and myelodysplastic syndromes: clinical correlates and prognostic studies

Vitamin D insufficiency is commonly observed in the general population; observational studies have suggested an association with increased risk of cancer development. We examined the clinical and prognostic relevance of low plasma levels of 25-hydroxyvitamin D (25[OH]D) in myeloproliferative neoplasms (MPN) and myelodysplastic syndromes (MDS). A total of 409 patients were studied: 247 (60%) with primary myelofibrosis (PMF), 74 (18%) with de novo MDS, 63 (15%) with polycythemia vera (PV), and 25 (6%) with essential thrombocythemia (ET). Plasma 25(OH)D levels were measured by liquid chromatography-tandem mass spectrometry; a level lower than 25 ng/mL indicated vitamin D insufficiency and a level lower than 10 ng/mL indicated severe deficiency. The proportion of patients with 25(OH)D insufficiency was significantly greater in PMF (48%) and PV (43%) when compared with ET (28%) and MDS (28%) (P = 0.01). Severe 25(OH)D deficiency was significantly more frequent in ET (12%) and PMF (9%), compared with PV (3%) and MDS (1%) (P = 0.05). There were no significant correlations between 25(OH)D insufficiency, or severe deficiency, and a variety of clinical or laboratory variables in PMF, MDS, or PV. Furthermore, Vitamin D insufficiency did not influence either overall or leukemia-free survival in PMF, MDS, or PV (P > 0.05). We conclude that while hypovitaminosis D is relatively common in MPN and MDS, its clinical relevance for prognosis is limited.

Differentiation therapy of acute myeloid leukemia

Acute Myeloid Leukemia (AML) is a predominant acute leukemia among adults, characterized by accumulation of malignantly transformed immature myeloid precursors. A very attractive way to treat myeloid leukemia, which is now called 'differentiation therapy', was proposed as in vitro studies have shown that a variety of agents stimulate differentiation of the cell lines isolated from leukemic patients. One of the differentiation-inducing agents, all-trans retinoic acid (ATRA), which can induce granulocytic differentiation in myeloid leukemic cell lines, has been introduced into clinics to treat patients with acute promyelocytic leukemia (APL) in which a PML-RARA fusion protein is generated by a t(15;17)(q22;q12) chromosomal translocation. Because differentiation therapy using ATRA has significantly improved prognosis for patients with APL, many efforts have been made to find alternative differentiating agents. Since 1,25-dihydroxyvitamin D3 (1,25D) is capable of inducing in vitro monocyte/macrophage differentiation of myeloid leukemic cells, clinical trials have been performed to estimate its potential to treat patients with AML or myelodysplastic syndrome (MDS). Unfortunately therapeutic concentrations of 1,25D can induce potentially fatal systemic hypercalcemia, thus limiting clinical utility of that compound. Attempts to overcome this problem have focused on the synthesis of 1,25D analogs (VDAs) which retain differentiation inducing potential, but lack its hypercalcemic effects. This review aims to discuss current problems and potential solutions in differentiation therapy of AML.

A systems approach to bone pathophysiology

With evolving interest in multiscalar biological systems one could assume that reductionist approaches may not fully describe biological complexity. Instead, tools such as mathematical modeling, network analysis, and other multiplexed clinical- and research-oriented tests enable rapid analyses of high-throughput data parsed at the genomic, proteomic, metabolomic, and physiomic levels. A physiomic-level approach allows for recursive horizontal and vertical integration of subsystem coupling across and within spatiotemporal scales. Additionally, this methodology recognizes previously ignored subsystems and the strong, nonintuitively obvious and indirect connections among physiological events that potentially account for the uncertainties in medicine. In this review, we flip the reductionist research paradigm and review the concept of systems biology and its applications to bone pathophysiology. Specifically, a bone-centric physiome model is presented that incorporates systemic-level processes with their respective therapeutic implications.

Differentiation therapy of leukemia: 3 decades of development

A characteristic feature of leukemia cells is a blockade of differentiation at a distinct stage in cellular maturation. In the 1970s and 1980s, studies demonstrating the capabilities of certain chemicals to induce differentiation of hematopoietic cell lines fostered the concept of treating leukemia by forcing malignant cells to undergo terminal differentiation instead of killing them through cytotoxicity. The first promising reports on this notion prompted a review article on this subject by us 25 years ago. In this review, we revisit this interesting field of study and report the progress achieved in the course of nearly 3 decades. The best proof of principle for differentiation therapy has been the treatment of acute promyelocytic leukemia with all-trans retinoic acid. Attempts to emulate this success with other nuclear hormone ligands such as vitamin D compounds and PPARgamma agonists or different classes of substances such as hematopoietic cytokines or compounds affecting the epigenetic landscape have not been successful on a broad scale. However, a multitude of studies demonstrating partial progress and improvements and, finally, the new powerful possibilities of forward and reverse engineering of differentiation pathways by manipulation of transcription factors support the continued enthusiasm for differentiation therapy of leukemia in the future.