ReviewNovel vitamin D analogues; cytotoxic and anti-proliferative activity against a diffuse large B-cell lymphoma cell line and B-cells from healthy donors
Introduction
Calcitriol (1,25-dihydroxyvitamin D3; 1,25D3) impacts physiological processes in the human body, with perhaps the most notable being the regulation of Ca2+ and phosphate (Pi) transport and bone mineralization [1]. Other actions include control of the growth, differentiation and functional activity of numerous cell types including those of the skin, immune system and pancreas [2].
Numerous studies demonstrate that the active form of vitamin D promotes the differentiation of HL-60 cells (a cell line that typifies acute myeloid leukaemia AML) to a phenotype resembling differentiated monocytes in bone marrow [3], such that majority of cells are now CD14+ cells [4]. Similar results have been obtained for cell lines of biologically related origin, e.g., THP-1 and U-937 cells [5], [6]. In addition to the pro-differentiative effects of 1,25D3, considerable attention has been paid to its cytotoxic and anti-proliferative actions. This has been studied in various mouse models, human cultured breast and colon cancers and also in HL-60 cells, which growth arrest in the G1 phase of cell cycle [7], [8], [9]. It should be noted however that the antitumor activity of 1,25D3 is evident at supra-physiological concentrations, which also promote hypercalcemia and hypercalciuria [10], which are likely to limit therapeutic potential. This has motivated the search for vitamin D analogues (VDAs) with less propensity to increase Ca2+ levels. Some identified compounds retain interaction with the VDR and the anti-proliferative/pro-differentiative capacity but display more limited effect on calcium levels in comparison to 1,25D3 [11].
Lymphoma is a cancer of lymphocytes presenting as either Hodgkin’s (HL) or non-Hodgkin’s lymphoma (NHL); over 90% of all NHL are of B-cell origin. According to the Cancer Research UK statistics over 12,000 people are diagnosed with NHL every year in the UK which makes it the 6th most common cancer in this country and the 11th most common cause of cancer death worldwide. As many as 40% of people diagnosed with this disease are predicted to survive less than 10 years.
It is estimated that 50% of NHL cases in the UK and 25–35% worldwide can be categorised as diffuse large B-cell lymphoma (DLBCL) [12]. DLBCL is an aggressive malignancy of B lymphocytes of germinal centre origin and is characterised by the presence of rapidly proliferating large cells with basophilic cytoplasm and vesicular nuclei [13]. Current treatments for DLBCL include the anti-CD20 monoclonal antibody, rituximab, and cycles of a combination of cyclophosphamide, doxorubicin, vincristine, prednisone (CHOP). Unfortunately, rituximab-CHOP treatment (R-CHOP) can be associated with severe toxicity and only displays failure-free survival of 65% after 3 years [14].
There is little data concerning the therapeutic potential of vitamin D analogues for the treatment of NHL. To address further therapeutic potential from 1,25D3 and VDAs, we investigate in the present study the impact of 1,25D3 and novel VDAs upon DOHH2 and K422, cell lines representative of DLBCL, as well as B-cells from healthy donors.
Section snippets
Vitamin D analogues
1,25D3 and all analogues (PRI-1890, PRI-1906, PRI-2191, PRI-2205; Fig. 1) were synthesized in the Pharmaceutical Research Institute (Warsaw, Poland). The compounds were dissolved in absolute ethanol, the concentration adjusted to 100 μM and the aliquots stored at −20 °C prior to experiments.
Cell culture
HL-60 and DOHH-2 cells were cultured in RPMI-1640 medium (Sigma–Aldrich, UK) supplemented with 1% L-glutamine (Life Technologies), 1% penicillin/streptomycin (Sigma–Aldrich, 10,000 units penicillin and 10 mg
Results and discussion
There are already a few reports describing the impact of vitamin D on B-cells. It is known that normal B-cells express VDR at very low levels though the protein is up-regulated following the stimulation of the cells [15]. Malignant B-cells express VDR and both Hodgkin’s and Non-Hodgkin’s lymphoma cells have relatively high levels of this protein [16]. It has been shown that 1,25D3 inhibits proliferation of anti-CD40, anti-IgM, and IL-21 stimulated B-cells [17]. 1,25D3 has also been shown to
Conclusions
In summary, this study demonstrates that relatively high concentrations of 1,25D3 and vitamin D analogues are cytotoxic to DOHH2 cells (with less pronounced effect in K422 cells) with the extent of killing similar to that observed against HL-60 cells. We have also shown that DOHH2 cells express VDR and that ligand engagement increases expression. From this, we conclude that DOHH2 is a good model to study the effects of 1,25D3 and derived compounds in DLBCL. VDAs also inhibited the proliferation
Acknowledgments
The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013 under REA grant agreement number 315902. PK gratefully acknowledges receipt of a Marie Curie Research Associate post. AK and NMB are partners within the Marie Curie Initial Training Network DECIDE (Decision-making within cells and differentiation entity therapies)
References (31)
Induction of vitamin D receptor mRNA expression in psoriatic plaques correlates with clinical response to 1,25-dihydroxyvitamin D3
J. Invest. Dermatol.
(1996)- et al.
The vitamin D receptor: new paradigms for the regulation of gene expression by 1,25-dihydroxyvitamin D(3)
Endocrinol. Metab. Clin. North Am.
(2010) - et al.
Cell differentiating and anti-proliferative activity of side-chain modified analogues of 1,25-dihydroxyvitamin D3
J. Steroid Biochem. Mol. Biol.
(1998) Antiproliferative effect of a vitamin D3 analog, EB1089, on HL-60 cells by the induction of TGF-beta receptor
Leuk. Res.
(1999)Vitamin D and cancer: deciphering the truth
Biochim. Biophys. Acta
(2011)Diffuse large B-cell lymphoma
Crit. Rev. Oncol. Hematol.
(2013)Dose-densified chemoimmunotherapy followed by systemic central nervous system prophylaxis for younger high-risk diffuse large B-cell/follicular grade 3 lymphoma patients: results of a phase II Nordic Lymphoma Group study
Ann. Oncol.
(2013)- et al.
New vitamin D analogs
Kidney Int. Suppl.
(2003) Structure-function analysis of vitamin D(2) analogs as potential inducers of leukemia differentiation and inhibitors of prostate cancer proliferation
J. Steroid Biochem. Mol. Biol.
(2011)The apoptosis and proliferation of SAC-activated B cells by IL-10 are associated with changes in Bcl-2, Bcl-xL, and Mcl-1 expression
Cell Immunol.
(1997)