Gattei V, Aldinucci D, Petti M C, Da Ponte A, Zagonel V, Pinto A
Leukemia Unit, INRCCS, Aviano, Italy.
Leukemia. 1993 May;7 Suppl 1:42-8.
5-Aza-2'-deoxycytidine (Decitabine) is an analog of deoxycytidine now entering clinical trials in acute myeloid leukemia (AML) owing to a defined antileukemic activity mediated at least in part by DNA hypomethylation, altered gene expression, and induction of cell differentiation. In the present study, we examined the relationship between the in vitro sensitivity to Decitabine of blast progenitors and the clinical outcome, in nine AML patients treated in vivo with Decitabine within a phase II trial carried out at two different institutions. Leukemic blast progenitors in acute myeloid leukemia (AML) undergo terminal divisions giving rise to colonies in methylcellulose. The self-renewal capacity of blast progenitors is conversely reflected by a secondary methylcellulose assay after exponential growth of clonogenic cells in suspension cultures. Three out of four patients, in which clonogenic cells in methylcellulose were strongly suppressed by Decitabine and clonogenic growth of blasts cultured in suspension was only slightly affected, failed on Decitabine treatment in vivo. Two subjects, whose blast progenitors in suspension culture were significantly inhibited by Decitabine, obtained a positive hematological response (complete or partial remission, CR or PR) and an additional patient showing a similar in vitro pattern died in induction with an hypoplastic marrow without morphological evidence of persistant leukemia. Interestingly two patients displaying an unfavourable in vitro pattern (i.e. a minor suppression of self-renewal mitoses as evinced from suspension cultures) achieved a hematological response (CR and PR) upon in vivo therapy with Decitabine. The in vitro response to Decitabine of clonogenic progenitors from both these patients shifted to a favourable pattern (i.e. major suppression of self-renewal versus terminal mitoses) following manipulation of culture conditions by the addition or removal of exogenous growth factors. In addition, in a further patient refractory to treatment with Decitabine in vivo, similar alterations of the culture conditions were unable to modify the unfavourable pattern of response to the drug in vitro. Our results indicate that the sensitivity of blast progenitors in suspension cultures strongly correlates with the remission outcome of the patients. From our data, it also appears that alterations of culture microenvironment are able to modify the response of AML blasts to Decitabine, unveiling the 'hidden' sensitivity of leukemic progenitors to the drug in cases characterized by a discrepancy between in vivo and in vitro results, i.e. apparent in vitro resistance and favourable clinical outcome.
5-氮杂-2'-脱氧胞苷（地西他滨）是脱氧胞苷的类似物，由于其明确的抗白血病活性，至少部分通过DNA低甲基化、基因表达改变和细胞分化诱导介导，目前正在急性髓系白血病（AML）中进行临床试验。在本研究中，我们在两个不同机构进行的一项II期试验中，检测了9例接受地西他滨体内治疗的AML患者中，原始祖细胞对地西他滨的体外敏感性与临床结果之间的关系。急性髓系白血病（AML）中的白血病原始祖细胞进行终末分裂，在甲基纤维素中形成集落。原始祖细胞的自我更新能力则通过悬浮培养中克隆形成细胞指数生长后的二次甲基纤维素试验来反映。在4例患者中，有3例患者甲基纤维素中的克隆形成细胞被地西他滨强烈抑制，而悬浮培养的原始细胞克隆生长仅受到轻微影响，这些患者在地西他滨体内治疗中失败。2例患者悬浮培养中的原始祖细胞被地西他滨显著抑制，获得了血液学阳性反应（完全或部分缓解，CR或PR），另有1例表现出类似体外模式的患者在诱导期死于骨髓发育不全，无持续白血病的形态学证据。有趣的是，2例显示体外模式不利的患者（即从悬浮培养中可见自我更新有丝分裂的轻微抑制）在地西他滨体内治疗后获得了血液学反应（CR和PR）。通过添加或去除外源性生长因子来改变培养条件后，这2例患者克隆形成祖细胞对地西他滨的体外反应转变为有利模式（即自我更新相对于终末有丝分裂的主要抑制）。此外，在另一例对地西他滨体内治疗难治的患者中，类似的培养条件改变无法改变体外对该药物不利的反应模式。我们的结果表明，悬浮培养中原始祖细胞的敏感性与患者的缓解结果密切相关。从我们的数据还可以看出，培养微环境的改变能够改变AML原始细胞对地西他滨的反应，在体内和体外结果存在差异的情况下，即明显的体外耐药和良好的临床结果，揭示白血病祖细胞对该药物“隐藏”的敏感性。
