Differential cellular internalization of anti-CD19 and -CD22 immunotoxins results in different cytotoxic activity.
Differential cellular internalization of anti-CD19 and -CD22 immunotoxins results in different cytotoxic activity.
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DOI：
10.1158/0008-5472.can-08-0461
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发表时间：
2008-08-01
期刊：
影响因子：
11.2
通讯作者：
Pastan, Ira
中科院分区：
文献类型：
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作者：
Du, Xing;Beers, Richard;FitzGerald, David J.;Pastan, Ira
B细胞恶性肿瘤通常表达表面抗原CD 19和CD 22。已经对针对两种抗原的免疫毒素进行了评价，靶向CD 22的免疫毒素更具活性。为了理解细胞毒性的这种差异并指导治疗靶标的筛选，我们比较了两种免疫毒素，靶向CD 19的FMC 63（Fv）-PE 38和靶向CD 22的RFB 4（Fv）-PE 38（BL 22）。6种淋巴瘤细胞系每个细胞对CD 19的结合位点比对CD 22的多4-9倍，但BL 22的活性比FMC 63（Fv）-PE 38高4-140倍，尽管它们具有相似的细胞结合亲和力（Kd <7 nM）。在一小时内，大量的BL 22被内化（比细胞表面上的CD 22分子的数目多2-3倍），而仅5.2-16.6%的表面结合的FMC 63（Fv）-PE 38被内化。免疫毒素内化后，CD 22的细胞内储库大大减少，表明其有助于BL 22的摄取。用放线菌酮处理细胞不会降低BL 22的内化。两种内化的免疫毒素位于相同的囊泡中。我们的研究结果表明，大量的BL 22结合到CD 22的快速内化，使CD 22比CD 19更好的治疗目标的免疫毒素，并可能为其他免疫缀合物，在细胞内的行为。
B cell malignancies routinely express surface antigens CD19 and CD22. Immunotoxins against both antigens have been evaluated and the immunotoxins targeting CD22 are more active. To understand this disparity in cytotoxicity and guide the screening of therapeutic targets, we compared two immunotoxins, FMC63(Fv)-PE38 targeting CD19 and RFB4(Fv)-PE38 (BL22) targeting CD22. Six lymphoma cell lines have 4-9-fold more binding sites per cell for CD19 than for CD22, but BL22 is 4-140-fold more active than FMC63(Fv)-PE38, even though they have a similar cell binding affinity (Kd ∼7 nM). In one hour, large amounts of BL22 are internalized (2-3-fold more than the number of CD22 molecules on the cell surface), while only 5.2-16.6% of surface bound FMC63(Fv)-PE38 is internalized. The intracellular reservoir of CD22 decreases greatly after immunotoxin internalization indicating it contributes to the uptake of BL22. Treatment of cells with cycloheximide does not reduce the internalization of BL22. Both internalized immunotoxins are located in the same vesicles. Our results show that the rapid internalization of large amounts of BL22 bound to CD22 makes CD22 a better therapeutic target than CD19 for immunotoxins and probably for other immunoconjugates that act inside cells.