1,25-Dihydroxyvitamin D3 Stimulates Expression and Translocation of Protein Kinase Cα and Cδ via a Nongenomic Mechanism and Rapidly Induces Phosphorylation of a 33-kDa Protein in Acute Promyelocytic NB4 Cells

Abstract

NB4 cells are the only in vitro model for the study of acute promyelocytic leukemia (1). These cells contain the characteristic translocation (15;17) that disrupts the retinoic acid ␣-receptor and is thought to be the major contributor to the leukemic phenotype in acute promyelocytic leukemia patients (2). The majority of acute promyelocytic leukemia blasts from patients and the NB4 cell line in culture respond to pharmacologic doses of all-trans-retinoic acid by differentiating along the neutrophilic pathway. Remissions are frequent in diseased patients; however, relapse usually ensues as a result of the development of retinoic acid resistance (3). The mechanisms responsible for resistance are likely to include increased expression of cellular retinoic acid-binding proteins. This has prompted investigators, including ourselves, to consider the possibility of initiating cellular differentiation in the monocytic lineage as a potential treatment to be used cooperatively with all-trans-retinoic acid treatment or as an alternative therapy should all-trans-retinoic acid fail.We recently succeeded in inducing monocytic differentiation of NB4 cells using combinations of 1,25-dihydroxyvitamin D 3 (1,25-(OH) 2 D 3 ) 1 and TPA (4). We also demonstrated that the nongenomic analogue 1,25␣-dihydroxyprevitamin D 3 (HF) (5), which lacks the ability to bind and activate the vitamin D receptor (VDR), was 20-fold more potent than authentic 1,25-(OH) 2 D 3 in priming NB4 cells for monocytic differentiation (6). Co-administration of a selective nongenomic antagonist, 1␤,25-dihydroxyvitamin D 3 (HL) (7), attenuated the responses to both 1,25-(OH) 2 D 3 and HF (6). Thus, the differentiative activity of 1,25-(OH) 2 D 3 in this model appeared to involve nonclassical targets of 1,25-(OH) 2 D 3 , the so-called nongenomic actions of 1,25-(OH) 2 D 3 . We also showed that inhibitors of protein kinase C (PKC) attenuated the differentiating ability of 1,25-(OH) 2 D 3 in the priming phase of the response (8). Tyrosine kinase inhibitors also attenuated the differentiation response to 1,25-(OH) 2 D 3 , while a phosphotyrosylphosphatase inhibitor synergized with 1,25-(OH) 2 D 3 to promote monocyte development (8). These data suggested that PKC and tyrosine signaling cascades were pivotal in the response to 1,25-(OH) 2 D 3 in NB4 cell monocytic differentiation.Reports in the literature strongly implicate PKC␤ as a key mediator of differentiation in the monocytic lineage (9, 10). As well, PKC activation and PKC␣ translocation appear to be common features of chemically induced monocytic differentiation in HL-60 cells and a number of other cell differentiation models (reviewed in Ref. 11). However, among the many differences we have observed between HL-60 and NB4 cells (12), one of the most striking is the fact that nongenomic 1,25-(OH) 2 D 3 analogues are incapable of inducing monocytic differentiation in HL-60 cells, while they are fully active (even more potent) in the NB4 cell model. Therefore, we predicted that the NB4 cell line may utilize dist...

1,25 dihydroxyvitamin D3 stimulates phospholipase C-gamma in rat colonocytes: role of c-Src in PLC-gamma activation.

“…In other cell types, activation of PLC-␥ , in addition to translocation from the soluble to the membrane fraction, also involves tyrosine phosphorylation of this PLC isoform. In this regard, in preliminary studies, our laboratory has noted that 1,25(OH) 2 D 3 induced the tyrosine phosphorylation of a number of proteins in rat colonocytes (7), in agreement with recent findings of this secosteroid's actions in acute promyelocytic NB4 cells (8). In the present studies, we examined the effects of 1,25(OH) 2 D 3 on the tyrosine phosphorylation, subcellular distribution, and biochemical activity of PI-PLC-␥ in intact colonocytes.…”

p27 Is Essential for the Antiproliferative Action of 1,25-Dihydroxyvitamin D3 in Primary, but Not Immortalized, Mouse Embryonic Fibroblasts

“…These rapid actions may be mediated by a membrane-bound vitamin D receptor that differs from the nuclear vitamin D receptor. These actions may be involved in cross-talk with other signaling pathways that affect cellular proliferation and differentiation (21).…”

Bryostatin-1 and 1α,25-dihydroxyvitamin D3 synergistically stimulate the differentiation of NB4 acute promyelocytic leukemia cells

“…42 Activation of different PKC isoforms by 1␣,25(OH) 2 D 3 and PMA was also proposed as a mechanism in the differentiation of THP-1 leukemia cells and NB4 cells. 43,44 We have already reported that in NB4 cells, mitogen-activated protein kinase is involved in 1␣,25(OH) 2 D 3 action. 45 Since the ALP activity is one manifestation of NB4 cell differentiation 20 and is greatly induced by the combination of bryostatin-1 and 1␣,25(OH) 2 D 3 , we postulate that there are probably two different signal transduction pathways involved in this NB4 cell differentiation.…”