Highly accumulated hyaluronan (HA) not only provides a physiological barrier but also supports an immune-suppressive tumour microenvironment. High-molecular-weight (HMW)-HA inhibits the activation of immune cells and their access into tumour tissues, whereas, low-molecular-weight oligo-HA is known to potentially activate dendritic cells (DCs). In this paper, we investigated whether small extracellular vesicle (EVs)-PH20 hyaluronidase induces tumour HA degradation, which, in turn, activates DCs to promote anti-cancer immune responses. Informed by our previous work, we used a small EV carrying GPI-anchored PH20 hyaluronidase (Exo-PH20) that could deeply penetrate into tumour foci via HA degradation. We found that Exo-PH20-treatment successfully activates the maturation and migration of DCs in vivo, particularly CD103⁺ DCs leading to the activation of tumour-specific CD8⁺ T cells, which work together to inhibit tumour growth. Moreover, combination with anti-PD-L1 antibody provided potent tumour-specific CD8⁺ T cell immune responses as well as elicited prominent tumour growth inhibition both in syngenic and spontaneous breast cancer models, and this anti-tumour immunity was durable. Together, these results present new insights for HA degradation by Exo-PH20, providing a better understanding of oligo HA-triggered immune responses to cancer.

高度积累的透明质酸（HA）不仅提供了生理屏障，而且还支持了免疫抑制性肿瘤微环境。高分子量（HMW）-HA抑制免疫细胞的活化及其进入肿瘤组织的通路，而已知低分子量的oligo-HA则可能激活树突状细胞（DC）。在本文中，我们研究了小的细胞外囊泡（EVs）-PH20透明质酸酶是否会诱导肿瘤HA降解，进而激活DC从而促进抗癌免疫反应。在我们之前的工作中得知，我们使用了带有GPI锚定的PH20透明质酸酶（Exo-PH20）的小型EV，它可以通过HA降解深入渗透到肿瘤灶中。我们发现Exo-PH20处理成功激活了DC在体内的成熟和迁移，特别是CD103 ⁺ DC会激活肿瘤特异性CD8 ⁺ T细胞，这些细胞共同抑制肿瘤的生长。此外，与抗PD-L1抗体的组合提供了有效的肿瘤特异性CD8 ⁺ T细胞免疫应答，并在同基因和自发性乳腺癌模型中均引起了显着的肿瘤生长抑制作用，并且这种抗肿瘤免疫力是持久的。总之，这些结果为Exo-PH20对HA降解提供了新的见解，从而更好地了解了寡聚HA触发的对癌症的免疫反应。