Laboratory of Tumor Vaccinology, Melanoma Sarcoma Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.
Clin Cancer Res. 2013 Sep 1;19(17):4728-39. doi: 10.1158/1078-0432.CCR-13-0088. Epub 2013 Jul 5.
We addressed the possibility that low levels of tumor cell-bound antibodies targeting gangliosides might accelerate tumor growth.
To test this hypothesis, we treated mice with a range of monoclonal antibody (mAb) doses against GM2, GD2, GD3, and CD20 after challenge with tumors expressing these antigens and tested the activity of the same mAbs in vitro. We also explored the mechanisms behind the complement-mediated tumor growth acceleration that we observed and an approach to overcome it.
Serologically detectable levels of IgM-mAb against GM2 are able to delay or prevent tumor growth of high GM2 expressing cell lines both in vitro and in a SCID mouse model, whereas very low levels of this mAb resulted in slight but consistent acceleration of tumor growth in both settings. Surprisingly, this is not restricted to IgM mAb targeting GM2 but consistent against an IgG mAb targeting GD3 as well. These findings were mirrored by in vitro studies with antibodies against these antigens as well as GD2 and CD20 (with Rituxan), and shown to be complement-dependent in all cases. Complement-mediated accelerated growth of cultured tumor cell lines initiated by low mAb levels was associated with activation of the phosphoinositide 3-kinase (PI3K)/AKT survival pathway and significantly elevated levels of both p-AKT and p-PRAS40. This complement-mediated PI3K activation and accelerated tumor growth in vitro and in vivo are eliminated by PI3K inhibitors NVP-BEZ235 and Wortmannin. These PI3K inhibitors also significantly increased efficacy of high doses of these four mAbs.
Our findings suggest that manipulation of the PI3K/AKT pathway and its signaling network can significantly increase the potency of passively administered mAbs and vaccine-induced antibodies targeting a variety of tumor cell surface antigens.
我们研究了肿瘤细胞结合抗体针对神经节苷脂水平较低是否可能加速肿瘤生长的可能性。
为了验证这一假说，我们在表达这些抗原的肿瘤模型中用一系列单克隆抗体（mAb）治疗小鼠，并在体外测试相同 mAb 的活性，以测试针对 GM2、GD2、GD3 和 CD20 的 mAb 剂量对肿瘤生长的影响。我们还探索了我们观察到的补体介导的肿瘤生长加速的机制，以及克服这种机制的方法。
针对 GM2 的 IgM-mAb 的血清学检测水平能够延迟或阻止体外和 SCID 小鼠模型中高 GM2 表达细胞系的肿瘤生长，而这种 mAb 的极低水平导致两种情况下肿瘤生长略有但持续加速。令人惊讶的是，这不仅限于针对 GM2 的 IgM mAb，而且针对 IgG mAb 针对 GD3 也是如此。这些发现与针对这些抗原以及 GD2 和 CD20（与 Rituxan）的抗体的体外研究相吻合，并在所有情况下均显示为补体依赖性。在体外培养的肿瘤细胞系中，低 mAb 水平引发的补体介导的生长加速与磷酸肌醇 3-激酶（PI3K）/AKT 生存途径的激活有关，p-AKT 和 p-PRAS40 的水平均显著升高。这种补体介导的 PI3K 激活以及体外和体内肿瘤生长的加速，可通过 PI3K 抑制剂 NVP-BEZ235 和 Wortmannin 消除。这些 PI3K 抑制剂还显著增加了这四种 mAb 高剂量的疗效。
我们的研究结果表明，PI3K/AKT 途径及其信号网络的操纵可以显著提高被动给予的 mAb 和针对各种肿瘤细胞表面抗原的疫苗诱导抗体的效力。
