Darwiche N, El-Sabban M, Bazzi R, Nasr R, Al-Hashimi S, Hermine O, de Thé H, Bazarbachi A
Department of Biology, American University of Beirut, Beirut, Lebanon.
Hematol J. 2001;2(2):127-35. doi: 10.1038/sj/thj/6200098.
Adult T-cell leukemia/lymphoma, caused by the human T-cell lymphotropic virus type I, is an aggressive neoplasm of mature activated T cells that is generally resistant to conventional therapy. While arsenic trioxide (As) inhibits the growth and induces apoptosis in HTLV-I-infected T cells, synergistically, when combined with interferon-alpha, variable effects on growth with all trans retinoic acid treatment have been reported in ATL-derived cell lines and fresh ATL cells. In this study, we investigate the effects of ATRA alone or in combination with As in HTLV-I-transformed cells.
Four HTLV-I-transformed cell lines (HuT-102, MT2, C8166 and C91PL) were treated with different doses of ATRA alone or in combination with As for one to three days. Cell growth was assessed by cell count with 3H-thymidine incorporation. Cell cycle distribution was assessed by propidium iodine-labeled DNA content by flow cytometry. Apoptosis was evaluated by Hoechst nuclear staining and annexin-V binding assays. Expression of retinoid receptors, the viral transactivator Tax, and the proteins bcl-2 and IkappaB-alpha proteins, was analysed by Western blot.
Only C8166 cells were sensitive to the ATRA-induced growth inhibitory effect while HuT-102, MT2, and C91PL were resistant to ATRA treatment (up to 10(-5) M). The retinoid X receptor alpha and the retinoic acid receptor gamma (RARgamma) proteins were expressed in all four cell lines, while RARalpha protein was only detected in the HuT-102 and C8166 cells. The combination ATRA/As showed a highly synergistic effect on HuT-102 cells, and, to a lesser extent, on C8166 cells and resulted in a dramatic inhibition of cell proliferation and induction of massive apoptosis in HuT-102 cells, associated with caspase activation. While ATRA alone had no effect on Tax and IkappaB-alpha protein levels, ATRA increased the As-induced Tax degradation and the up-regulation of IkappaB-alpha protein. In contrast, the expression of bcl-2 protein was not significantly affected by any of the treatments.
Our data provide a rationale for combined ATRA and As-therapies in ATL patients refractory to conventional therapy and expressing RARalpha in their leukemic cells.
成人T细胞白血病/淋巴瘤由I型人嗜T细胞病毒引起，是一种成熟活化T细胞的侵袭性肿瘤，通常对传统疗法耐药。虽然三氧化二砷（As）可抑制HTLV-I感染的T细胞生长并诱导其凋亡，但与α干扰素联合使用时，在成人T细胞白血病衍生的细胞系和新鲜成人T细胞白血病细胞中，全反式维甲酸治疗对生长的影响各异。在本研究中，我们调查了全反式维甲酸单独或与三氧化二砷联合对HTLV-I转化细胞的影响。
用不同剂量的全反式维甲酸单独或与三氧化二砷联合处理四种HTLV-I转化细胞系（HuT-102、MT2、C8166和C91PL）1至3天。通过细胞计数和3H-胸腺嘧啶掺入评估细胞生长。通过流式细胞术用碘化丙啶标记的DNA含量评估细胞周期分布。通过Hoechst核染色和膜联蛋白-V结合试验评估凋亡。通过蛋白质印迹分析类视黄醇受体、病毒反式激活因子Tax以及bcl-2和IkappaB-α蛋白的表达。
仅C8166细胞对全反式维甲酸诱导的生长抑制作用敏感，而HuT-102、MT2和C91PL对全反式维甲酸治疗耐药（高达10^(-5) M）。四种细胞系均表达类视黄醇X受体α和维甲酸受体γ（RARγ）蛋白，而RARα蛋白仅在HuT-102和C8166细胞中检测到。全反式维甲酸/三氧化二砷组合对HuT-102细胞显示出高度协同作用，对C8166细胞的协同作用较小，导致HuT-102细胞的细胞增殖受到显著抑制并诱导大量凋亡，这与半胱天冬酶激活有关。虽然单独的全反式维甲酸对Tax和IkappaB-α蛋白水平无影响，但全反式维甲酸增加了三氧化二砷诱导的Tax降解和IkappaB-α蛋白的上调。相反，bcl-2蛋白的表达不受任何处理的显著影响。
我们的数据为在对传统疗法难治且白血病细胞中表达RARα的成人T细胞白血病患者中联合使用全反式维甲酸和三氧化二砷治疗提供了理论依据。
