Fludarabine and Cladribine Induce Changes in Surface Proteins on Human B‑Lymphoid Cell Lines Involved with Apoptosis, Cell Survival, and Antitumor Immunity

Fludarabine and cladribine are purine analogues used
to treat hematological
malignancies. Alone or in combination with therapeutic antibodies,
they are effective in treating patients with chronic lymphocytic leukemia
and non-Hodgkin's lymphoma. However, the mechanisms of action of these
drugs are not well understood. Plasma membrane proteins perform a
variety of essential functions that can be affected by malignancy
and perturbed by chemotherapy. Analysis of surface proteins may contribute
to an understanding of the mechanisms of action of purine analogues
and identify biomarkers for targeted therapy. The surface of human
cells is rich in N-linked glycoproteins, enabling use of a hydrazide-coupling
technique to enrich for glycoproteins, with iTRAQ labeling for quantitative
comparison. A number of plasma membrane proteins on human leukemia
and lymphoma cells were affected by treatment with a purine analogue,
including decreases in CD22 (an adhesion and signaling molecule) and
increases in CD205 (a “damaged cell marker”) and CD80
and CD50 (T-cell interaction molecules). Purine analogues may affect
B-cell receptor (BCR) signaling and costimulatory molecules, leading
to multiple signals for apoptosis and cell clearance. Fludarabine
and cladribine induce differential effects, with some cell survival
proteins (ECE-1 and CD100) more abundant after fludarabine treatment.
Cell surface proteins induced by fludarabine and cladribine may be
targets for therapeutic antibodies.

氟达拉滨（Fludarabine）与克拉屈滨（cladribine）均为嘌呤类类似物，临床用于治疗血液系统恶性肿瘤。二者既可单独给药，亦可与治疗性抗体联合使用，对慢性淋巴细胞白血病及非霍奇金淋巴瘤患者均展现出治疗效果。然而，此类药物的具体作用机制尚未得到充分阐明。质膜蛋白承担诸多关键生理功能，其表达可受恶性肿瘤影响，亦会因化疗发生紊乱。对细胞表面蛋白进行分析，或有助于阐明嘌呤类类似物的作用机制，并为靶向治疗筛选潜在生物标志物。人类细胞表面富含N-连接糖蛋白，因此可采用酰肼偶联技术实现糖蛋白富集，并通过iTRAQ标记完成定量比较。研究发现，人类白血病与淋巴瘤细胞表面的多种质膜蛋白会受嘌呤类类似物处理的调控：其中CD22（一种黏附与信号分子）的表达水平显著下调；而CD205（“损伤细胞标志物”）、CD80与CD50（均为T细胞相互作用分子）的表达水平则出现上调。嘌呤类类似物或可影响B细胞受体（BCR）信号通路及共刺激分子的表达，进而触发凋亡与细胞清除的多重信号级联反应。氟达拉滨与克拉屈滨可诱导产生差异化的细胞效应：经氟达拉滨处理后，部分细胞存活相关蛋白（如ECE-1与CD100）的表达丰度显著升高。氟达拉滨与克拉屈滨诱导上调的细胞表面蛋白，或可作为治疗性抗体的潜在作用靶点。