Abstract：
Multiple myeloma (MM) progression is closely dependent on cells in the bone marrow (BM) microenvironment, including fibroblasts (FBs) and immune cells. In their BM niche, MM cells adhere to FBs sustaining immune evasion, drug resistance and the undetectable endurance of tumor cells known as minimal residual disease (MRD). Here, we describe the novel bi-specific designed ankyrin repeat protein (DARPin) α-FAPx4-1BB (MP0310) with FAP-dependent 4-1BB agonistic activity. The α-FAPx4-1BB DARPin simultaneously binds to FAP and 4-1BB overexpressed by activated FBs and immune cells, respectively. Although flow cytometry analysis showed that T and NK cells from MM patients were not activated and did not express 4-1BB, stimulation with daratumumab or elotuzumab, monoclonal antibodies (mAbs) currently used for the treatment of MM, significantly upregulated 4-1BB both in vitro and in MM patients following mAb-based therapy. The mAb-induced 4-1BB overexpression allowed the engagement of α-FAPx4-1BB that acted as a bridge between FAP+FBs and 4-1BB+NK cells. Therefore, α-FAPx4-1BB enhanced both the adhesion of daratumumab-treated NK cells on FBs as well as their activation by improving release of CD107a and perforin, hence MM cell killing via antibody-mediated cell cytotoxicity (ADCC). Interestingly, α-FAPx4-1BB significantly potentiated daratumumab-mediated ADCC in the presence of FBs, suggesting that it may overcome the BM FBs\' immunosuppressive effect. Overall, we speculate that treatment with α-FAPx4-1BB may represent a valuable strategy to improve mAb-induced NK cell activity fostering MRD negativity in MM patients through the eradication of latent MRD cells.
摘要：
多发性骨髓瘤（MM）的进展密切依赖于骨髓（BM）微环境中的细胞，包括成纤维细胞（FBs）和免疫细胞。在他们的BM利基市场，MM细胞粘附在FBs上，维持免疫逃避，被称为微小残留病（MRD）的肿瘤细胞的耐药性和不可检测的耐力。这里,我们描述了具有FAP依赖性4-1BB激动活性的新型双特异性设计的锚蛋白重复蛋白（DARPin）α-FAPx4-1BB（MP0310）。α-FAPx4-1BBDARPin同时与活化的FBs和免疫细胞过表达的FAP和4-1BB结合,分别。尽管流式细胞术分析显示MM患者的T细胞和NK细胞未被激活且不表达4-1BB,用达雷妥单抗或埃洛妥珠单抗刺激，目前用于治疗MM的单克隆抗体（mAb），在基于mAb的治疗后，体外和MM患者中4-1BB均显著上调。mAb诱导的4-1BB过表达允许α-FAPx4-1BB的参与,其充当FAP+FBs和4-1BB+NK细胞之间的桥梁。因此,α-FAPx4-1BB通过改善CD107a和穿孔素的释放来增强达雷木单抗处理的NK细胞在FBs上的粘附及其激活，因此通过抗体介导的细胞毒性(ADCC)杀伤MM细胞。有趣的是,α-FAPx4-1BB在存在FBs的情况下显着增强达雷木单抗介导的ADCC，表明它可以克服BMFBs的免疫抑制作用。总的来说,我们推测,α-FAPx4-1BB治疗可能是一种有价值的策略,可以通过根除潜伏MRD细胞来改善mAb诱导的NK细胞活性,培养MM患者的MRD阴性。
