[1296] Opposing Effects of Vitamin D/Vitamin D Receptor and Interferon Regulatory Factor-4 in Anaplastic Large Cell Lymphomas.

Sertac Kip, Julie C Porcher, James R Cerhan, Stephen M Ansell, Ahmet Dogan, Andrew L Feldman. Mayo Clinic, Rochester, MN

Background: Anaplastic large cell lymphomas (ALCLs) are T-cell lymphomas that express the activation-associated transcription factor, interferon regulatory factor-4 (IRF4). We previously have shown that IRF4 drives ALCL proliferation. Recently, our group identified vitamin D deficiency as a poor prognostic factor in T-cell lymphomas. As 1,25-dihydroxy-Vitamin D3 (VD3) down-regulates IRF4 in myeloid cells, we hypothesized that VD3 might inhibit IRF4-driven ALCL proliferation, and undertook this study to characterize the relationships among VD3, its receptor (VDR), IRF4, and proliferation in ALCL cell lines.
Design: Normal T cells were isolated from the peripheral blood of healthy donors by negative selection and stimulated using phorbol myristate acetate and ionomycin. ALCL cells were treated with VD3 (100 nM), doxorubicin (2 ng/mL), and IRF4 or control siRNAs (50 nM). IRF4 and VDR expression were measured by Western blotting. Proliferation was assessed by 3H-thymidine incorporation or MTT assay. Changes were evaluated in multiple experiments using paired t tests.
Results: IRF4 and VDR were absent in resting T cells, and expression of both proteins was induced upon stimulation. In contrast, expression levels of IRF4 and VDR were inversely proportional in ALCL cell lines SUDHL-1 (low IRF4/high VDR expression; arbitrary ratio, 1.0) and Karpas 299 (high IRF4/low VDR; ratio, 11.1). In SUDHL-1, VD3 inhibited IRF4 expression by 63% and inhibited proliferation by 40% (p=0.006). In Karpas 299, VD3 alone did not inhibit IRF4 expression or proliferation. In the presence of doxorubicin, however, VD3 inhibited IRF4 expression by 71% and proliferation by 48% (p=0.002). Finally, IRF4 siRNA increased expression of VDR in both cell lines.
Conclusions: VD3 inhibited ALCL proliferation and IRF4 expression when basal IRF4 expression was low and VDR expression was high. In contrast, ALCL cells with high IRF4 expression showed low VDR expression and were resistant to VD3. However, these cells could be sensitized to the inhibitory effects of VD3 by doxorubicin. The inverse relationship between IRF4 and VDR was confirmed in ALCL cells by siRNA studies, but was absent in normal T cells. Thus: (1) VD3/VDR and IRF4 have opposing effects in ALCLs, with high IRF4 expression conferring resistance to the effects of VD3; (2) IRF4 inhibition may enhance beneficial effects of VD3 by inducing expression of VDR; and (3) ensuring vitamin D sufficiency in ALCL patients may be particularly critical during administration of doxorubicin-based chemotherapy.
Category: Hematopathology

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 172, Monday Morning

 

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