Kornblau S M, Vu H T, Ruvolo P, Estrov Z, O'Brien S, Cortes J, Kantarjian H, Andreeff M, May W S
Section of Molecular Hematology and Therapy, The University of Texas M.D. Anderson Cancer Center, Houston, 77030-4095, USA.
Clin Cancer Res. 2000 Apr;6(4):1401-9.
Previously, we demonstrated that the level of BCL2 expression is prognostic in acute myelogenous leukemia (AML). High levels of BCL2 correlate with an adverse outcome when associated with favorable and intermediate prognosis cytogenetics (FIPC), whereas low levels portend an adverse outcome when associated with unfavorable cytogenetics (UC). Because BCL2 function can be modulated by dimerization with family members, like BAX, or by phosphorylation by protein kinase C alpha (PKCalpha), we hypothesize that the relative expression of these proteins in primary leukemic cells might alter the prognostic impact of BCL2 expression. We therefore measured BAX and PKCalpha protein levels in peripheral blood mononuclear cell lysates from 165 newly diagnosed AML patients and correlated the expression of these proteins with BCL2 expression, patient survival, and remission induction success. Expression levels of BAX and PKCalpha were normalized against a control cell line, K562. BAX and PKCalpha expression levels were heterogeneous and did not correlate with the percentage of blasts in the sample (R2 = 0.01 and <0.01). The median expression of both was similar across FAB groups but the range was greater for M4. A similar distribution of expression was observed in all cytogenetic groups, except that patients with inversion 16 demonstrated lower levels of BAX. Individually, neither PKCalpha nor BAX expression was prognostic of response to induction therapy or survival. A similar outcome was obtained when patients were stratified by cytogenetics into FIPC and UC groups. However, the ratio of either BCL2:BAX (B2:BX) or PKCalphaB2:BX (PKB2:BX) was highly prognostic. Patients with FIPC and a lower ratio (less than median) of either B2:BX or PKB2:BX had a significantly higher remission induction rate (88 versus 69%, P = 0.04) and longer survival (median: 141 versus 80.5 weeks, P = 0.007) compared with those with ratios more than median. For patients with UC, values of either B2:BX or PKB2:BX below the median had an inferior response rate to induction therapy (35 versus 78%, P = 0.0006) and inferior survival outcomes (median survival: 11 versus 53 weeks, P = 0.00002). Interestingly, FIPC and UC patients with antiapoptotic ratios (defined as B2:BX or PKB2:BX more than median) had identical response rates and survival outcomes. In multivariate analyses, the compound variables of cytogenetics and B2:BX, or PKB2:BX were independent predictors of survival. These results suggest that expression levels of proteins that affect the functional status of BCL2 modify the prognostic impact of BCL2 and suggest that the role of apoptosis in different cases of AML varies independently in the different cytogenetic subgroups.
此前，我们证实BCL2表达水平对急性髓系白血病（AML）具有预后价值。与预后良好和中等的细胞遗传学（FIPC）相关时，高水平的BCL2与不良预后相关；而与预后不良的细胞遗传学（UC）相关时，低水平的BCL2预示不良预后。由于BCL2的功能可通过与家族成员如BAX二聚化，或被蛋白激酶Cα（PKCα）磷酸化来调节，我们推测这些蛋白在原发性白血病细胞中的相对表达可能会改变BCL2表达的预后影响。因此，我们检测了165例新诊断AML患者外周血单个核细胞裂解物中BAX和PKCα蛋白水平，并将这些蛋白的表达与BCL2表达、患者生存率及缓解诱导成功率进行关联分析。以对照细胞系K562对BAX和PKCα的表达水平进行标准化。BAX和PKCα的表达水平存在异质性，且与样本中原始细胞百分比无关（R2 = 0.01和<0.01）。二者的中位表达在FAB各亚型中相似，但M4亚型的表达范围更大。除16号染色体倒位的患者BAX水平较低外，在所有细胞遗传学组中均观察到类似的表达分布。单独来看，PKCα和BAX的表达均不能预测诱导治疗反应或生存率。按细胞遗传学将患者分为FIPC和UC组时，也得到了类似结果。然而，BCL2:BAX（B2:BX）或PKCαB2:BX（PKB2:BX）的比值具有高度预后价值。与比值高于中位数的患者相比，FIPC且B2:BX或PKB2:BX比值较低（低于中位数）的患者缓解诱导率显著更高（88%对69%，P = 0.04），生存期更长（中位数：141周对80.5周，P = 0.0,07）。对于UC患者，B2:BX或PKB2:BX低于中位数的患者诱导治疗反应率较低（35%对78%，P =,0006），生存结局较差（中位生存期：11周对53周，P =,00002）。有趣的是，抗凋亡比值（定义为B2:BX或PKB2:BX高于中位数）的FIPC和UC患者具有相同的反应率和生存结局。在多变量分析中，细胞遗传学与B2:BX或PKB2:BX的复合变量是生存的独立预测因素。这些结果表明，影响BCL2功能状态的蛋白表达水平会改变BCL2的预后影响，并提示凋亡在不同细胞遗传学亚组的不同AML病例中的作用独立变化。
