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◇令和元年6月27日(木)加齢研研究員会セミナーのご案内
日時: 令和元年6月27日(木)午後4時00分〜5時30分
場所: 加齢研実験研究棟7階 セミナー室1
演題: がんの抗体医薬におけるFc受容体の役割について
講師: ジェイ シェフ バービーク 客員教授
所属: 桐蔭横浜大学生命医工学科
担当: 遠藤 章太(所属 遺伝子導入研究分野・内線 8504)
要旨: Tumor-targeting antibodies (Abs) have limited success against solid malignancies whereas immunomodulatory Abs blocking interactions of co-inhibitory receptors to their ligands (“checkpoint blockers”) such as CTLA4 and PD-L1 on immune cells have shown impressive therapeutic efficacy. Detailed analysis of anti-CTLA4 Ab therapy revealed that optimal therapeutic efficacy requires binding to FcγR, mediating depletion of intra-tumoral Treg cells. By using a large cohort of conditional and compound FcγR KO mice combined with cell type-specific immune cell ablation we could study the role of FcγR and FcγR expressing cells in the tumor microenvironment in tumor-targeting Ab therapy in B16F10 melanoma and anti-PD-L1 Ab therapy in MC38 C57BL/6 and CT26 BALB/c colon adenocarcinoma to provide a rationale for improvement of the therapeutic efficacy of these Abs.
We observed that the addition of innate stimulatory compounds, like TLR ligands, to tumor-targeting Ab therapy, greatly enhances its efficacy in solid cancers by increasing the frequency of intra-tumoral inflammatory macrophages which highly express all FcγR.
All IgG subclasses of anti-PD-L1 had a strong therapeutic effect. However, in the CT26 but not the MC38 model, the anti-PD-L1 IgG2a, the IgG subclass with the highest affinity for activating FcγR, showed stronger therapeutic efficacy than other IgG subclasses. This was associated with a reduction of a myeloid cell subset with high expression of PD-L1 in the tumor microenvironment. We concluded that FcγR interaction is not required for effective anti-PD-L1 immunotherapy but can add additional benefit depending on the tumor model.