Selleri C, Maciejewski J P, Pane F, Luciano L, Raiola A M, Mostarda I, Salvatore F, Rotoli B
Division of Hematology, CEINGE and Department of Biochemistry and Biotechnology, Federico II University Medical School, Naples, Italy.
Blood. 1998 Aug 1;92(3):981-9.
Fas-R is expressed constitutively in CD34(+) cells of patients with chronic myelogenous leukemia (CML); Fas-R triggering results in decreased proliferation rate due to apoptosis of clonogenic cells. We have already shown that alpha-interferon (IFN-alpha) enhances Fas-R expression on CML progenitor cells, thus increasing their sensitivity to Fas-R agonists. Although it appears that IFN-alpha can prime CML cells for the effects of Fas, the response to IFN-alpha in vivo is not a constant feature in CML patients. We studied the mechanisms of Fas-mediated apoptosis in 11 patients suffering from CML in chronic phase and tried to see whether there was a correlation between in vitro inducibility of apoptosis in CD34(+) CML cells after Fas-R triggering and the clinical response to IFN-alpha. After priming with IFN-alpha, Fas triggering resulted in in vitro suppression of hematopoietic cell growth in seven of eight patients who had optimal hematologic response to IFN-alpha; in the same conditions, no inhibitory response to Fas-R agonist was observed in cells from three of three patients who proved to be poor responders to IFN-alpha. In responders to IFN-alpha, Fas-R agonist induced dose-dependent apoptosis of CD34(+) cells; this effect was associated with a decrease in the bcr/abl protein level. In cells derived from patients with a poor response to IFN-alpha, the rate of apoptosis in culture remained unchanged in the presence of Fas-R agonist and no bcr/abl downmodulation was observed. Finally, we measured bcr/abl mRNA by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and found that decreased bcr/abl protein after Fas triggering was not associated with decreased amounts of specific mRNA, a finding which is consistent with a posttranscriptional regulation of the bcr/abl protein expression. It appears that Fas-mediated downmodulation of p210 bcr/abl restores susceptibility to apoptosis of CML cells; in addition, in vitro studies on CML cells may predict response to IFN-alpha treatment.
Fas-R在慢性粒细胞白血病（CML）患者的CD34(+)细胞中组成性表达；Fas-R触发导致克隆形成细胞凋亡，从而使增殖率降低。我们已经表明，α-干扰素（IFN-α）可增强CML祖细胞上的Fas-R表达，从而增加其对Fas-R激动剂的敏感性。尽管似乎IFN-α可使CML细胞对Fas的作用产生预敏感性，但CML患者体内对IFN-α的反应并非恒定特征。我们研究了11例慢性期CML患者中Fas介导的凋亡机制，并试图观察Fas-R触发后CD34(+) CML细胞体外凋亡诱导能力与对IFN-α的临床反应之间是否存在相关性。用IFN-α预处理后，Fas触发导致8例对IFN-α有最佳血液学反应的患者中有7例的造血细胞生长在体外受到抑制；在相同条件下，3例对IFN-α反应较差的患者的细胞未观察到对Fas-R激动剂的抑制反应。在对IFN-α有反应的患者中，Fas-R激动剂诱导CD34(+)细胞发生剂量依赖性凋亡；这种效应与bcr/abl蛋白水平降低有关。在对IFN-α反应较差的患者来源的细胞中，在存在Fas-R激动剂的情况下，培养物中的凋亡率保持不变，且未观察到bcr/abl下调。最后，我们通过定量逆转录聚合酶链反应（RT-PCR）测量了bcr/abl mRNA，发现Fas触发后bcr/abl蛋白减少与特异性mRNA量的减少无关，这一发现与bcr/abl蛋白表达的转录后调节一致。似乎Fas介导的p210 bcr/abl下调可恢复CML细胞对凋亡的敏感性；此外，对CML细胞的体外研究可能预测对IFN-α治疗的反应。
