據2021年統計，肝癌是人類最具侵襲性的癌症之一，並在全球癌症死亡率中排名第三。在肝癌的進展中，對於腫瘤免疫微環境有很密切的關係。而在腫瘤微環境中，浸潤的巨噬細胞會因為與癌細胞的相互作用而演變成腫瘤相關巨噬細胞。腫瘤相關巨噬細胞與癌細胞的相互作用會影響彼此的行為。例如:癌細胞會釋放CD47會分別與腫瘤相關巨噬細胞上的受體Siglec10與SIRPα做結合，誘導「勿吃我」的訊號，引發先天免疫檢查點，以逃避巨噬細胞的攻擊與吞噬。而腫瘤相關巨噬細胞則會釋放細胞激素，促進癌細胞生長與轉移的能力，增加血管新生，進而加速腫瘤惡化的程度。實驗室先前研究顯示，中心體P4.1結合蛋白CPAP在肝癌細胞中有過度表達的情形，而CPAP會增加腫瘤幹細胞的特質並發現會透過增加IL-6/STAT的活性來增加CD24的表現。因此本研究認為肝癌中，CPAP會透過增加CD24的表現，增加肝癌的幹細胞特質以及影響腫瘤相關巨噬細胞的行為；透過與腫瘤相關巨噬細胞的相互作用。而我們的結果表明，CPAP與CD24透過與巨噬細胞的作用來參與HCC免疫微環境的調節和免疫逃逸；若能以此為目標可能可以為 HCC 患者提供一種新的免疫療法。

In tumor immune microenvironment (TIME), cancer cells act as an important driver on the polarization and functional regulation of tumor-associated macrophages (TAMs) differentiated from infiltrated macrophages. Furthermore, it has been known that cancer cells utilize diverse regulatory mechanisms to evade phagocytosis by macrophages, such as "don't eat me" signals. Notely, these mechanisms involve the up-regulation of cancer stemness-related proteins CD47 and CD24 in the cancer cells, enabling their interaction with specific receptors, SIRPα and Siglec10, which are expressed in tumor-associated macrophages (TAMs), resulting in the initiation of a ''don't eat me'' signal. In our previous studies, we demonstrated the overexpression of centrosomal P4.1-associated protein (CPAP) in hepatocellular carcinoma (HCC) tissue. The overexpression of CPAP in HCC increases cancer stemness properties and upregulates CD24 expression by activating the IL-6/STAT3 singling pathways. In this study, qPCR analysis, transwell assay, flow cytometry, and CCK-8 assay were performed by using THP-1 cells or human peripheral blood mononuclear cells (PBMCs) co-cultured with conditioned medium (CM) derived from CPAP-overexpressing HCC cells to investigate the impact of CPAP on the polarization and functions of TAMs in HCC. We found that the expressions of TAM-related genes and migratory ability are increased in macrophages following co-cultured with CM derived from CPAP-overexpressing HCC cells, while no effect on their proliferation. Additionally, the protein and mRNA levels of CD24 in CPAP-overexpressing HCC spheroids were higher than those in HCC stable cells. Phagocytosis assays have demonstrated that CPAP-overexpressing HCC spheroids exhibit an enhanced ability to evade macrophage phagocytosis in comparison to HCC stable cells. Confirmation of CPAP by CD24 siRNA and anti-CD24 antibody regulates phagocytosis directly by upregulating CD24 expression. As a result, the occurrence of the CD24-Siglec10 "don't eat me" signaling pathway increased. In conclusion, this research findings the potential role of CPAP in regulating the TIME and immune evasion through the CPAP/CD24 axis. Targeting this axis may offer a novel therapeutic strategy for HCC.

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