MacDonald William J, Verschleiser Brooke, Carlsen Lindsey, Huntington Kelsey E, Zhou Lanlan, El-Deiry Wafik S
Laboratory of Translational Oncology and Experimental Cancer Therapeutics, The Warren Alpert Medical School, Brown University Providence, RI 02903, USA.
Legorreta Cancer Center at Brown University, The Warren Alpert Medical School, Brown University Providence, RI 02903, USA.
Am J Cancer Res. 2023 Jul 15;13(7):2938-2947. eCollection 2023.
Integrin receptors have long posed as a potentially attractive target for disrupting cancer hallmarks. Promising preliminary findings with integrin inhibition as an adjuvant to chemotherapy have not translated to clinical success. However, the effect of integrin inhibition on tumor-immune cell interactions remains largely unexplored. Further investigation could shed light on a connection between integrin signaling and immune checkpoint expression, opening the path for using integrin inhibitors to sensitize otherwise resistant tumors to immunotherapy. Fluorescently labeled wild-type HCT-116 colorectal cancer cells and TALL-104 T-cells were co-cultured and treated with GLPG-0187, a small molecule integrin inhibitor, at various doses. This assay revealed dose dependent cancer cell killing, indicating that integrin inhibition may be sensitizing cancer cells to immune cells. The hypothesized mechanism involves TGF-β-mediated PD-L1 upregulation in cancer cells. To investigate this mechanism, both WT and p53-/- HCT-116 cells were pre-treated with GLPG-0187 and subsequently with latent-TGF-β. Western blot analysis demonstrated that the addition of latent-TGF-β increased the expression of PD-L1 in cancer cells. Additionally, a low dose of integrin inhibitor rescued these effects, returning PD-L1 expression back to control levels. This indicates that the immunostimulatory effects of integrin inhibition may be due to downregulation of immune checkpoint PD-L1 on cancer cells. It must be noted that the higher dose of the drug did not reduce PD-L1 expression. This could potentially be due to off-target effects conflicting with the proposed pathway; however, these findings are still under active investigation. Ongoing proteomic experiments will include a larger range of both drug and latent-TGF-β doses. Probing for additional downstream markers of TGF-β and up-stream markers of PD-L1 will help to further elucidate this mechanism. Further co-culture experiments will also include anti-PD-L1 and anti-PD-1 therapy to investigate the viability of integrin inhibition as an adjuvant to immune checkpoint blockade.
整合素受体长期以来一直被视为破坏癌症特征的潜在有吸引力的靶点。整合素抑制作为化疗辅助手段的有前景的初步研究结果尚未转化为临床成功。然而，整合素抑制对肿瘤-免疫细胞相互作用的影响在很大程度上仍未得到探索。进一步的研究可能会揭示整合素信号传导与免疫检查点表达之间的联系，为使用整合素抑制剂使原本耐药的肿瘤对免疫疗法敏感开辟道路。用荧光标记的野生型HCT-116结肠癌细胞和TALL-104 T细胞进行共培养，并用小分子整合素抑制剂GLPG-0187以不同剂量进行处理。该试验揭示了剂量依赖性的癌细胞杀伤，表明整合素抑制可能使癌细胞对免疫细胞敏感。假设的机制涉及癌细胞中TGF-β介导的PD-L1上调。为了研究这一机制，野生型和p53基因敲除的HCT-116细胞均先用GLPG-0187预处理，随后用潜伏性TGF-β处理。蛋白质免疫印迹分析表明，添加潜伏性TGF-β可增加癌细胞中PD-L1的表达。此外，低剂量的整合素抑制剂可挽救这些效应，使PD-L1表达恢复到对照水平。这表明整合素抑制的免疫刺激作用可能是由于癌细胞上免疫检查点PD-L1的下调。必须指出的是，较高剂量的药物并未降低PD-L1的表达。这可能是由于脱靶效应与所提出的途径相冲突；然而，这些发现仍在积极研究中。正在进行的蛋白质组学实验将包括更大范围的药物和潜伏性TGF-β剂量。探索TGF-β的其他下游标志物和PD-L1的上游标志物将有助于进一步阐明这一机制。进一步的共培养实验还将包括抗PD-L1和抗PD-1治疗，以研究整合素抑制作为免疫检查点阻断辅助手段的可行性。
