Pancreatic ductal adenocarcinoma (PDAC) is characterized by an immunosuppressive tumor microenvironment with a dense desmoplastic stroma. The expression of β-galactoside-binding protein galectin-3 is regarded as an intrinsic tumor escape mechanism for inhibition of tumor-infiltrating T cell function. In this study, we demonstrated that galectin-3 is expressed by PDAC and by γδ or αβ T cells but is only released in small amounts by either cell population. Interestingly, large amounts of galectin-3 were released during the co-culture of allogeneic in vitro expanded or allogeneic or autologous resting T cells with PDAC cells. By focusing on the co-culture of tumor cells and γδ T cells, we observed that knockdown of galectin-3 in tumor cells identified these cells as the source of secreted galectin-3. Galectin-3 released by tumor cells or addition of physiological concentrations of recombinant galectin-3 did neither further inhibit the impaired γδ T cell cytotoxicity against PDAC cells nor did it induce cell death of in vitro expanded γδ T cells. Initial proliferation of resting peripheral blood and tumor-infiltrating Vδ2-expressing γδ T cells was impaired by galectin-3 in a cell-cell-contact dependent manner. The interaction of galectin-3 with α3β1 integrin expressed by Vδ2 γδ T cells was involved in the inhibition of γδ T cell proliferation. The addition of bispecific antibodies targeting γδ T cells to PDAC cells enhanced their cytotoxic activity independent of the galectin-3 release. These results are of high relevance in the context of an in vivo application of bispecific antibodies which can enhance cytotoxic activity of γδ T cells against tumor cells but probably not their proliferation when galectin-3 is present. In contrast, adoptive transfer of in vitro expanded γδ T cells together with bispecific antibodies will enhance γδ T cell cytotoxicity and overcomes the immunosuppressive function of galectin-3.

胰腺导管腺癌（PDAC）的特征是具有抑制性增生基质的免疫抑制性肿瘤微环境。β-半乳糖苷结合蛋白galectin-3的表达被认为是抑制肿瘤浸润性T细胞功能的内在肿瘤逃逸机制。在这项研究中，我们证明了Galectin-3由PDAC和γδ或αβT细胞表达，但仅由任一细胞群体少量释放。有趣的是，同种异体的共培养过程中释放了大量的galectin-3体外具有PDAC细胞的扩增或同种异体或自体静止T细胞。通过关注肿瘤细胞和γδT细胞的共培养，我们观察到肿瘤细胞中半乳凝素3的敲低将这些细胞鉴定为分泌的半乳凝素3的来源。肿瘤细胞释放的Galectin-3或添加生理浓度的重组Galectin-3既不会进一步抑制γδT细胞对PDAC细胞的细胞毒性，也不会诱导PDAC细胞死亡。体外扩增的γδT细胞。galectin-3以细胞-细胞接触依赖性的方式损害了静息外周血和浸润肿瘤的表达Vδ2的γδT细胞的初始增殖。galectin-3与Vδ2γδT细胞表达的α3β1整合素的相互作用参与了γδT细胞增殖的抑制。将靶向γδT细胞的双特异性抗体添加到PDAC细胞可增强其细胞毒活性，而与半乳糖凝集素3释放无关。这些结果在以下方面具有高度相关性：体内可以增强γδT细胞对肿瘤细胞的细胞毒性活性，但当存在半乳糖凝集素3时不能增殖的双特异性抗体的应用。相反，过继转移体外 扩增的γδT细胞与双特异性抗体一起可增强γδT细胞的细胞毒性，并克服了Galectin-3的免疫抑制功能。