Interaction of vitamin D derivatives and granulocyte-macrophage colony-stimulating factor in leukaemic cell differentiation

Vitamin D sufficiency enhances differentiation of patient-derived prostate epithelial organoids

Vitamin D is an essential steroid hormone that regulates systemic calcium homeostasis and cell fate decisions. The prostate gland is hormonally regulated, requiring steroids for proliferation and differentiation of secretory luminal cells. Vitamin D deficiency is associated with an increased risk of lethal prostate cancer, which exhibits a dedifferentiated pathology, linking vitamin D sufficiency to epithelial differentiation. To determine vitamin D regulation of prostatic epithelial differentiation, patient-derived benign prostate epithelial organoids were grown in vitamin D-deficient or -sufficient conditions. Organoids were assessed by phenotype and single-cell RNA sequencing. Mechanistic validation demonstrated that vitamin D sufficiency promoted organoid growth and accelerated differentiation by inhibiting canonical Wnt activity and suppressing Wnt family member DKK3. Wnt and DKK3 were also reduced by vitamin D in prostate tissue explants by spatial transcriptomics. Wnt dysregulation is a known contributor to aggressive prostate cancer, thus findings further link vitamin D deficiency to lethal disease.

Regulation of monocyte differentiation by specific signaling modules and associated transcription factor networks

Monocyte/macrophages are important players in orchestrating the immune response as well as connecting innate and adaptive immunity. Myelopoiesis and monopoiesis are characterized by the interplay between expansion of stem/progenitor cells and progression towards further developed (myelo)monocytic phenotypes. In response to a variety of differentiation-inducing stimuli, various prominent signaling pathways are activated. Subsequently, specific transcription factors are induced, regulating cell proliferation and maturation. This review article focuses on the integration of signaling modules and transcriptional networks involved in the determination of monocytic differentiation.

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.

Effects of sodium stibogluconate on differentiation and proliferation of human myeloid leukemia cell lines in vitro

PTPases are key signaling molecules and targets for developing novel therapeutics. We have studied the in vitro biological activity of PTPase inhibitor sodium stibogluconate (SS) on differentiation and proliferation of myeloid leukemia cell lines (NB4, HL-60 and U937). SS (250 microg/ml, 6 days) induced 87% of NB4 cells to reduce nitroblue tetrazolium (NBT), in comparison to the 90% induced by ATRA (1 microM, 6 days). SS treatment of NB4 cells resulted in an increase of CD11b expression and of a morphologically more mature population, coincident with growth arrest at S phase and increased cell death. The effect of SS on NB4 differentiation was irreversible and required continuous drug exposure. SS (400 microg/ml, 6 days) induced 60% and 55% of NBT-positive cells in HL-60 and U937 cell lines, which were augmented in the presence of GM-CSF (25 ng/ml) to levels (85% and 81%, respectively) comparable to those induced by ATRA. SS induced increased tyrosine phosphorylation of cellular proteins in the AML cell lines and inactivated SHP-1 PTPase in NB4 cells, consistent with SS functioning as a PTPase inhibitor in the leukemia cells. These results provide the first evidence of an anti-leukemia activity of SS as a PTPase inhibitor.

Structure-specific control of differentiation and apoptosis of human promyelocytic leukemia (HL-60) cells by A-ring diastereomers of 2-methyl-1alpha,25-dihydroxyvitamin D(3) and its 20-epimer

1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) has been shown to modulate not only proliferation and differentiation but also apoptosis of malignant cells, indicating that it would be useful for the treatment of hyperproliferative diseases such as cancer and psoriasis. Little information is available concerning structural motifs of the 1alpha,25(OH)(2)D(3) molecule responsible for modulation of differentiation and apoptosis. We synthesized all possible A-ring diastereomers of the 2-methyl-1alpha,25(OH)(2)D(3) and its 20-epimer and evaluated their biological activities in human promyelocytic leukemia (HL-60) cells. Surprisingly, the potent analogues could be clearly divided into two groups: (i) those bearing the 1alpha- and 3beta-hydroxyl groups on the A-ring were potent inducers of differentiation and growth inhibitors of HL-60 cells and (ii) those bearing the 1beta-hydroxyl group together with either 3alpha- or 3beta-hydroxyl groups on the A-ring were potent stimulators of apoptosis in these cells. We have clearly identified for the first time the structural motifs on the basis of the stereochemistry of both hydroxyl groups at positions 1 and 3 of the A-ring of the 1alpha,25(OH)(2)D(3) molecule responsible for the induction of differentiation and apoptosis of HL-60 cells. These findings provide useful information not only for structure-function studies of 1alpha,25(OH)(2)D(3) analogues but also for the development of therapeutic agents for the treatment of leukemia and other cancers.

Differential expression of multiple unexpected genes during U937 cell and macrophage differentiation detected by suppressive subtractive hybridization

OBJECTIVE

The objective of this study was to identify new markers of myelomonocytic differentiation using a sensitive technique that permits detection of rare differential gene expression.

MATERIALS AND METHODS

[corrected] Suppressive subtractive hybridization (SSH) was performed between the human myelomonocytic U937 cell line and 1 alpha, 25-dihydroxyvitamin D3 and transforming growth factor beta 1 differentiated U937 cells. cDNA clones with significant increased expression in differentiated U937 cells over nondifferentiated U937 cells were characterized by sequencing. [corrected] The pattern of differential gene expression obtained by SSH was confirmed by cDNA Southern and Northern blots on the undifferentiated vs. differentiated U937 cells, and by reverse transcriptase polymerase chain reaction on undifferentiated human CD34(+) stem cells isolated from bone marrow vs. peripheral blood CD14(+) mature monocytes.

RESULTS

Seven cDNAs never associated with in vitro U937 cell myelomonocytic differentiation (prolactin, 11-beta hydroxysteroid dehydrogenase [11 beta-HSD)] haptoglobin alpha (2FS)-beta precursor, GLIPR, RTVP, the RNA helicase P68, and spermidine-spermine N1-acetyltransferase) were identified. The first five of these genes previously were associated with immune function and the last two are important for intermediary metabolism. Differential expression was confirmed in CD34(+)/CD14(+) monocyte differentiation for all genes but 11 beta-HSD.

CONCLUSIONS

We identified six new markers of U937 cell differentiation, which also are differentially expressed during normal human myelomonocytic differentiation.

Lycopene and 1,25-dihydroxyvitamin D3 cooperate in the inhibition of cell cycle progression and induction of differentiation in HL-60 leukemic cells

Lycopene, the major tomato carotenoid, has been found to inhibit proliferation of several types of cancer cells, including those of breast, lung, and endometrium. By extending the work to the HL-60 promyelocytic leukemia cell line, we aimed to evaluate some mechanistic aspects of this effect. Particularly, the possibility was examined that the antiproliferative action of the carotenoid is associated with induction of cell differentiation. Lycopene treatment resulted in a concentration-dependent reduction in HL-60 cell growth as measured by [3H]thymidine incorporation and cell counting. This effect was accompanied by inhibition of cell cycle progression in the G0/G1 phase as measured by flow cytometry. Lycopene alone induced cell differentiation as measured by phorbol ester-dependent reduction of nitro blue tetrazolium and expression of the cell surface antigen CD14. Results of several recent intervention studies with beta-carotene, which have revealed no beneficial effects of this carotenoid, suggest that a single dietary component cannot explain the anticancer effect of diets rich in vegetables and fruits. Thus another goal of our study was to examine whether lycopene has the ability to synergize with other natural anticancer compounds, such as 1,25-dihydroxyvitamin D3, which when used alone are therapeutically active only at high and toxic concentrations. The combination of low concentrations of lycopene with 1,25-dihydroxyvitamin D3 exhibited a synergistic effect on cell proliferation and differentiation and an additive effect on cell cycle progression. Such synergistic antiproliferative and differentiating effects of lycopene and other compounds found in the diet and in plasma may suggest the inclusion of the carotenoid in the diet as a cancer-preventive measure.

Leukemia cell differentiation: cellular and molecular interactions of retinoids and vitamin D

1. The conventional approach to treatment of acute myeloid leukemia has been the use of chemotherapy, which although being cytotoxic to malignant clones, is also cytodestructive to normal cells. In addition, some leukemia cells develop resistance to chemotherapy and are therefore difficult to eradicate. 2. Differentiation therapy, whereby immature cells are induced to attain a mature phenotype by differentiation agents, has provided an alternative strategy in the treatment of hyperproliferative disorders. This has been highlighted by the use of all-trans retinoic acid (ATRA) in the treatment of acute promyelocytic leukemia (APL). 3. Another differentiation agent, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), directs monocytic maturation of normal and leukemic cells. Cellular studies have revealed that combinations of vitamin D derivatives and retinoids such as ATRA and 9-cis retinoic acid (9-cis RA) exhibit cooperative effects on differentiation in established leukemia cell lines such as HL-60, U937, and NB4. Furthermore, vitamin D compounds, although not able to induce apoptosis when used alone, potentiate apoptosis induced by 9-cis RA in HL-60 cells and differentially regulate the expression of the apoptosis-related gene products bcl-2 and bax. The molecular mechanisms involved in regulating differentiation and apoptosis by these agents are mediated through the interactions of the nuclear receptors for vitamin D (VDR), ATRA (RAR), and 9-cis RA (RXR), which are able to form homo- or heterodimeric complexes and transcriptionally activate or repress target gene expression. 4. There is evidence to suggest that nitric oxide may also play a role in leukemic cell differentiation and that 1,25(OH)2D3 may influence endogenous nitric oxide production either by directly increasing tumor necrosis factor-alpha (TNF-alpha) or through a secondary mediator such as the C-type lectin CD23.

C1qRP, the C1q Receptor That Enhances Phagocytosis, Is Detected Specifically in Human Cells of Myeloid Lineage, Endothelial Cells, and Platelets

The complement component C1q can interact with a variety of different cells, resulting in multiple functional consequences depending on the cell type. mAbs R3 and R139, which recognize a 126,000 Mr (reduced) cell surface protein, are able to abrogate the C1q-mediated enhancement of monocyte phagocytosis. The cDNA encoding this C1q receptor that modulates phagocytosis, C1qRP, has recently been cloned. Using a DNA probe based on the coding region of the receptor, Northern blot and RT-PCR analysis of RNA isolated from different cell types showed C1qRP expression in cells of myeloid origin and in endothelial cells, but not in cells of lymphoid origin nor in the HeLa epithelial-like cell line or iliac artery smooth muscle cells. FACS analysis of cell surface expression of C1qRP, as detected by mAb R139 and R3, corresponded in all cases to the mRNA levels detected. Using the anti-C1qRP mAb, the 126,000 Mr receptor was also detected in lysates of human platelets. Interestingly, C1qRP is not expressed by the promyelocytic leukemia cell line HL-60, and differentiation of these cells with various chemical compounds did not induce C1qRP expression. It has been reported that C1q can induce specific receptor-mediated responses in fibroblasts. However, RNA and cell surface expression analysis for C1qRP indicate that this particular C1q receptor is not expressed by either human gingival or human skin fibroblasts. These data demonstrate selective expression of C1qRP in specific cell types and support the hypothesis that there is more than one C1q receptor mediating the diverse responses triggered by C1q.