1Faculty of Biotechnology, University of Wroclaw, 2Pharmaceutical Research Institute, Warszawa
Background: 1,25-Dihydroxyvitamin D3 (1,25D) mediates its biological effects by binding to the vitamin D receptor (VDR) which acts as a transcription factor. In addition to regulation of calcium homeostasis 1,25D is involved in immunomodulation, cell proliferation and differentiation. Thus differentiation therapy of myeloid leukemia using 1,25D is a very attractive alternative to existing treatments, but undesirable side effects of 1,25D caused that its semi-selective analogs, with reduced calcemic activity, have been synthesized. Usually HL60 acute myeloid leukemia (AML) cell line has been used for selection of candidate analogs for future studies. Here we used other leukemic cell lines: NB-4, THP-1 and U937 in order to compare activities of semi-selective side-chain modified 1,25D analogs named: PRI-1906, PRI-2191, PRI-2201 and PRI-2202.
Material and methods: The expression of cell surface markers CD11b and CD14 was analyzed in flow cytometry.
Results: We have noticed that expression of monocytic differentiation marker CD14 is upregulated in response to 1,25D or its analogs stronger than expression of CD11b, which is a marker of monocytic and granulocytic differentiation. Out of the three cell lines studied, differentiation was the strongest in THP-1 cell line. The differentiation-inducing potency of PRI-1906 and PRI-2191 was comparable to that of 1,25D in THP-1 cells and higher in NB-4 and U937 cells.
Discussion and conclusions: Our experiments point at a variable susceptibility to 1,25D-induced cell differentiation of cells derived from various subtypes of leukemia, and show that the analogs PRI-1906 and PRI-2191 are the most promising candidates for antileukemic therapy.
Keywords: 1,25-dihydroxyvitamin D3, side-chain modified analogs, differentiation, THP-1, NB-4, U937, flow cytometry