PURPOSE According to the American Cancer Society, 1 in 8 women in the U.S. will develop breast cancer, with triple-negative breast cancer (TNBC) comprising 15-20% of all breast cancer cases. TNBC is an aggressive subtype due to its high metastatic potential and lack of targeted therapy. Recently, folate receptor alpha (FRA) is found to be expressed on 80% of TNBC with high expression correlating with poor prognosis. In this study, we examined whether binding IgA Fc-folate molecules to FRA receptors on TNBC cells can elicit and induce neutrophils (PMNs), by binding their FcαR1 receptors, to destroy TNBC cells. METHODS FRA was analyzed on TNBC cells and binding assays were performed using 3H-folate. Fc-folate was synthesized by linking Fc fragments of IgA via amine groups to folate. Binding specificity and antibody-dependent cellular cytotoxicity (ADCC) potential of Fc-folate to FcαR1 were confirmed by measuring PMN adhesion and myeloperoxidase (MPO) release in a cell-based ELISA. Fc-folate binding to FRA-expressing TNBC cells inducing PMNs to destroy these cells was determined using 51Cr-release and calcein-labeling assays. RESULTS Our results demonstrate expression of FRA on TNBC cells at levels consistent with folate binding. Fc-folate binds with high affinity to FRA compared to whole IgA-folate and induces MPO release from PMN when bound to FcαR1. Fc-folate inhibited binding of 3H-folate to TNBC cells and induced significant cell lysis of TNBC cells when incubated in the presence of PMNs. CONCLUSION These findings support the hypothesis that an IgA Fc-folate conjugate can destroy TNBC cells by eliciting PMN-mediated ADCC.

中文翻译：

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IgA Fc叶酸偶联物激活并募集嗜中性粒细胞以直接靶向三阴性乳腺癌细胞。

目的根据美国癌症协会的数据，美国八分之一的女性会患乳腺癌，三阴性乳腺癌（TNBC）占所有乳腺癌病例的15-20％。TNBC是一种具有侵袭性的亚型，因为它具有很高的转移潜力并且缺乏靶向治疗。最近，发现叶酸受体α（FRA）在80％的TNBC中表达，且表达高与预后差有关。在这项研究中，我们研究了将IgA Fc叶酸分子与TNBC细胞上的FRA受体结合是否可以通过结合FcαR1受体来破坏TNBC细胞，从而引起并诱导嗜中性粒细胞（PMN）。方法对TNBC细胞进行FRA分析，并使用3H-叶酸进行结合测定。通过经由胺基将IgA的Fc片段连接至叶酸来合成Fc-叶酸。通过在基于细胞的ELISA中测量PMN粘附力和髓过氧化物酶（MPO）释放，证实了叶酸对FcαR1的结合特异性和抗体依赖性细胞毒性（ADCC）的潜力。使用51Cr释放和钙黄绿素标记测定法确定了与叶酸结合的FRA表达TNBC细胞诱导PMN破坏这些细胞。结果我们的结果证明FRA在TNBC细胞上的表达水平与叶酸结合一致。与完整的IgA叶酸相比，Fc叶酸与FRA的亲和力高，与FcαR1结合时可诱导PMN从MPN释放。当在PMN存在下孵育时，Fc叶酸抑制3H叶酸与TNBC细胞结合，并诱导TNBC细胞发生明显的细胞裂解。