Signaling of monocytic differentiation by a non‐hypercalcemic analog of vitamin D₃, 1,25(OH)₂‐5,6 trans‐16‐ene‐vitamin D₃, involves nuclear vitamin D receptor (nVDR) and non‐nVDR–mediated pathways

Abstract

Exposure of leukemia cells to the physiologically active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25D3) normalizes their phenotype to cells that resemble mature monocytes. One of the earliest detectable events in this process is an upregulation of the nuclear receptor for 1,25D3, the vitamin D receptor (nVDR). In contrast, the novel analog of 1,25D3, 1,25-dihydroxy-5,6 trans-16-ene-vitamin D3 (5,6-16D3), which has recently been reported to have low calcium-mobilizing activity in vivo, rapidly induced the expression of CD14, CD11b, and monocyte-specific esterase (MSE), classical markers of the mature monocyte, but upregulated nVDR expression less than 1,25D3. This upregulation was shown to be the result of altered degradation of the nVDR protein, while the levels of nVDR mRNA were constant. Knock-out of nVDR transcriptional activity by a decoy VDRE double-stranded deoxyoligonucleotide, markedly abrogated 1,25D3-induced differentiation, but incompletely inhibited 5,6-16D3-induced differentiation. These findings suggest that the unique ability of 5,6-16D3 to induce cell differentiation but not systemic hypercalcemia, may be due to the activation of pathways which initiate differentiation independently of nVDR.

Retinoblastoma Protein and CCAAT/Enhancer-Binding Protein β Are Required for 1,25-Dihydroxyvitamin D3-Induced Monocytic Differentiation of HL60 Cells

“…These methods were described previously (36). Briefly, aliquots of 1 ϫ 10 6 cells were washed twice with 1ϫ PBS and then incubated with 0.5 l of MY4-RD1 and 0.5 l of -FITC (Coulter, Miami, FL) at room temperature for 45 min to analyze the expression of surface cell markers CD14 and CD11b, respectively.…”

Calcitriol derivatives with two different side-chains at C-20. Part 4: Further chain modifications that alter VDR-dependent monocytic differentiation potency in human leukemia cells

“…To reduce the inactivating C-3 epimerization, the A-ring can be modified as the 19-nor variant, 9 or by changing the geometry of the 5E double bond; 10 as a result, biological activities are enhanced. 11,12 The discovery that 20-epi vitamin D analogs can exhibit higher potencies 13,14 engendered the synthesis of Gemini, distinguished by two identical side chains emanating at C-20. 15,16 In a second generation of Gemini compounds, chain-modifications aimed at metabolic retardation and enhanced differentiation were introduced stereoselectively 17,18 and their effects evaluated.…”

1α,25‐dihydroxyvitamin D3‐mediated stimulation of steroid sulphatase activity in myeloid leukaemic cell lines requires VDRnuc‐mediated activation of the RAS/RAF/ERK‐MAP kinase signalling pathway

“…In fact, it has recently been shown that 1a,25(OH) 2 D 3 , acting via VDR nuc , increases the activity of RAF, a key activator of the ERK-MAP kinase pathway, in HL60 cells [Studzinski et al, 2005]. Furthermore, activation of the JNK-MAP kinase [Ji et al, 2002] and the p38-MAP kinase pathways [Ji et al, 2002] are required for 1a,25(OH) 2 D 3 -driven monocytic differentiation of HL60 myeloid leukaemic cells. Finally, 1a,25(OH) 2 D 3 -stimulated, VDR nuc -mediated activation of the phosphatidylinositol 3-kinase-Akt-p70 S6 kinase pathway is essential for the differentiation of THP-1 myeloid leukaemic cell lines [Hmama et al, 1999].…”

“…Similarly, 1a,25(OH) 2 D 3 -stimulated translocation and activation of several DAG/calciumdependent protein kinase C isoforms (PKCa, b and d) in both NB4 cells [Berry et al, 1996] and HL60 cells [Macfarlane and Menzel, 1994;Pan et al, 1997;Slosberg et al, 2000] is essential for the monocytic differentiation of both cell types. The necessity for the activation of the ERK-MAP kinase pathway in 1a,25(OH) 2 D 3 -stimulated monocytic differentiation of NB4 cells was described almost a decade ago [Song et al, 1998], but several studies also show that activation of the ERK-MAP kinase is essential for the 1a,25(OH) 2 D 3 -stimulated monocytic differentiation of HL60 cells as well [Marcinkowska et al, 1997;Wang and Studzinski, 2001a,b;Ji et al, 2002]. In fact, it has recently been shown that 1a,25(OH) 2 D 3 , acting via VDR nuc , increases the activity of RAF, a key activator of the ERK-MAP kinase pathway, in HL60 cells [Studzinski et al, 2005].…”

“…Nuclear localisation of VDR nuc [HumeniukPolaczek and Marinkowska, 2004], and the generation of VDR nuc -driven genomic signals, is absolutely required for monocytic differentiation of HL60, U937 and THP-1 cells [Ji et al, 2002;Ji and Studzinski, 2004]. In contrast, monocytic differentiation of the NB4 acute promyelocytic is not dependent on VDR nucderived genomic signals, but is initiated by rapid non-genomic signals that, in turn, generate prolonged genomic signals that are required for differentiation [Bhatia et al, 1995;Miura et al, 1999;Hughes et al, 2005].…”