Muneekaew Saitong, Sasithong Pasut, Chupradit Koollawat, Saiprayong Kritayaporn, Nuchphongsai Thunchanok, Wattanapanitch Methichit
Siriraj Center for Regenerative Medicine, Research Department, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Biomedical Sciences Program, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
FEBS J. 2025 Jul 14. doi: 10.1111/febs.70192.
Signal regulatory protein alpha (SIRPα) is an essential immune checkpoint, predominantly expressed on myeloid cells, that binds to CD47. This interaction, termed the 'don't eat me' signal, contributes to immune suppression. Consequently, disruption of the SIRPα/CD47 axis emerges as a promising strategy to intervene in the 'don't eat me' signal, thereby initiating phagocytic activation. Various preclinical and clinical studies employed SIRPα/CD47-targeting molecules to disrupt the SIRPα/CD47 axis to promote cancer phagocytosis. However, concerns regarding their limited efficacy and side effects pose a challenge to applying this approach to cancer therapy. Here, we investigated the role of the SIRPα/CD47 axis in phagocytosis by performing clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated SIRPA gene disruption in the monocytic cell line THP-1. The SIRPα knockout (KO) THP-1 cells were comprehensively characterized for their phenotype and functions, including differentiation into M0 macrophages, polarization into M1 or M2 macrophages, and phagocytosis of bioparticles and cancer cells, and compared to their wild-type (WT) counterparts. The SIRPα KO THP-1 cells retained their monocyte and macrophage characteristics. Remarkably, they exhibited enhanced phagocytosis of bioparticles and leukemic cell lines but not breast cancer cell lines. The introduction of a chimeric antigen receptor (CAR) targeting tumor-associated mucin1 antigen (tMUC1-CAR) further enhanced their phagocytic activity against the breast cancer cell line, MCF-7, which expresses high levels of MUC1. Our findings highlight the therapeutic potential of SIRPα KO macrophages in cancer immunotherapy, particularly for hematologic malignancies. However, a combination with CAR was necessary to enhance the phagocytic activity against solid cancer models.
信号调节蛋白α（SIRPα）是一种重要的免疫检查点，主要表达于髓系细胞，可与CD47结合。这种相互作用被称为“别吃我”信号，有助于免疫抑制。因此，破坏SIRPα/CD47轴成为干预“别吃我”信号、从而启动吞噬激活的一种有前景的策略。各种临床前和临床研究采用靶向SIRPα/CD47的分子来破坏SIRPα/CD47轴，以促进癌症吞噬作用。然而，对其有限疗效和副作用的担忧给将这种方法应用于癌症治疗带来了挑战。在此，我们通过在单核细胞系THP-1中进行成簇规律间隔短回文重复序列（CRISPR）/Cas9介导的SIRPA基因破坏，研究了SIRPα/CD47轴在吞噬作用中的作用。对SIRPα基因敲除（KO）的THP-1细胞的表型和功能进行了全面表征，包括分化为M0巨噬细胞、极化为M1或M2巨噬细胞以及对生物颗粒和癌细胞的吞噬作用，并与野生型（WT）对照细胞进行了比较。SIRPα基因敲除的THP-1细胞保留了其单核细胞和巨噬细胞特征。值得注意的是，它们对生物颗粒和白血病细胞系的吞噬作用增强，但对乳腺癌细胞系则不然。引入靶向肿瘤相关粘蛋白1抗原（tMUC1-CAR）的嵌合抗原受体（CAR）进一步增强了它们对表达高水平MUC1的乳腺癌细胞系MCF-7的吞噬活性。我们的研究结果突出了SIRPα基因敲除巨噬细胞在癌症免疫治疗中的治疗潜力，特别是对血液系统恶性肿瘤。然而，需要与CAR联合使用以增强对实体癌模型的吞噬活性。
