Extracellular vesicles derived from irradiated oral squamous cell carcinoma cells inhibits M2 macrophage polarization by the miR-198-5p/MYD88 axis

Extracellular vesicle (EV)-mediated delivery of microRNAs (miRNAs) plays a crucial role in intercellular communication between tumor cells and their microenvironment, thereby influencing the response to radiotherapy. This study aims to elucidate the effects of EVs derived from irradiated tumor cells on macrophage polarization in oral squamous cell carcinoma (OSCC) and to explore the underlying mechanisms involved. The expression levels of miR-198-5p within EVs isolated from both normoxic and irradiated OSCC cells were quantified. Subsequently, we assessed the impact of these EVs on macrophage polarization by analyzing the expression profiles of M1 and M2 markers. Additionally, bioinformatics analyses were performed to predict potential targets for miR-198-5p, with dual-luciferase assays confirming its interaction with myeloid differentiation primary response 88 (MYD88). miR-198-5p was found to be enriched in EVs derived from irradiated OSCC cells (IR-EVs), facilitating its transfer into macrophages. IR-EVs abundant in miR-198-5p inhibited an M2 macrophage polarization phenotype. Furthermore, it was demonstrated that miR-198-5p directly targets MYD88, leading to a reduction in its expression within macrophages. Importantly, overexpression of MYD88 mitigated the inhibitory effect exerted by miR-198-5p-rich IR-EVs on M2 polarization of macrophages. Our findings indicate that EVs rich in miR-198-5p derived from irradiated OSCC cells inhibit M2 polarization of macrophages through inhibition of MYD88 expression; thus suggesting that encapsulating miR-198-5p within EVs may represent a promising therapeutic strategy for OSCC.

细胞外囊泡（Extracellular vesicle, EV）介导的微小RNA（microRNAs, miRNAs）递送在肿瘤细胞与其微环境之间的细胞间通讯中发挥关键作用，进而影响肿瘤对放射治疗的响应。本研究旨在阐明辐照肿瘤细胞来源的EV对口腔鳞状细胞癌（Oral Squamous Cell Carcinoma, OSCC）中巨噬细胞极化的影响，并探究其潜在的作用机制。研究人员对常氧及辐照OSCC细胞分离得到的EV中miR-198-5p的表达水平进行了定量检测。随后，通过分析M1型与M2型巨噬细胞标志物的表达谱，评估了上述EV对巨噬细胞极化的影响。此外，研究通过生物信息学分析预测了miR-198-5p的潜在靶点，并借助双荧光素酶报告基因实验证实了其与髓系分化初级应答基因88（Myeloid Differentiation Primary Response 88, MYD88）的相互作用。实验结果显示，miR-198-5p在辐照OSCC细胞来源的EV（IR-EVs）中富集，可被高效递送至巨噬细胞内。富含miR-198-5p的IR-EVs可抑制巨噬细胞向M2型极化的表型。进一步研究证实，miR-198-5p可直接靶向MYD88，导致巨噬细胞内MYD88的表达水平下调。重要的是，MYD88过表达可抵消富含miR-198-5p的IR-EVs对巨噬细胞M2型极化的抑制作用。本研究结果表明，辐照OSCC细胞来源的富含miR-198-5p的EV可通过抑制MYD88的表达，进而抑制巨噬细胞的M2型极化，这提示将miR-198-5p包裹于EV中或可成为口腔鳞状细胞癌的一种极具前景的治疗策略。