De Marchi Elena, Pegoraro Anna, Turiello Roberta, Di Virgilio Francesco, Morello Silvana, Adinolfi Elena
Department of Medical Sciences, University of Ferrara, Ferrara, Italy.
Department of Pharmacy, University of Salerno, Fisciano, Italy.
Front Cell Dev Biol. 2022 May 18;10:876510. doi: 10.3389/fcell.2022.876510. eCollection 2022.
ATP and adenosine are key constituents of the tumor niche where they exert opposite and complementary roles. ATP can be released in response to cell damage or actively released by tumor cells and subsequently degraded into adenosine, which accumulates within the tumor microenvironment. Notably, while ATP promotes immune eradicating responses mainly the P2X7 receptor (P2X7R), extracellular adenosine acts as a potent immune suppressor and facilitates neovascularization thanks to the A2A receptor (A2AR). To date, studies exploring the interplay between P2X7R and A2AR in the tumor microenvironment are as yet missing. Here, we show that, in C57/bl6 P2X7 null mice inoculated with B16-F10 melanoma cells, several pro-inflammatory cytokines, including interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), interleukin 12 (IL-12), interleukin 17 (IL-17), interferon gamma (IFN-γ) were significantly decreased, while the immune suppressant transforming growth factor beta (TGF-β) was almost three-fold increased. Interestingly, tumors growing in P2X7-null mice upregulated tumor-associated and splenic A2AR, suggesting that immunosuppression linked to lack of the P2X7R might depend upon A2AR overexpression. Immunohistochemical analysis showed that tumor cells' A2AR expression was increased, especially around necrotic areas, and that vascular endothelial growth factor (VEGF) and the endothelial marker CD31 were upregulated. A2AR antagonist SCH58261 treatment reduced tumor growth similarly in the P2X7 wild type or null mice strain. However, SCH58261 reduced VEGF only in the P2X7 knock out mice, thus supporting the hypothesis of an A2AR-mediated increase in vascularization observed in the P2X7-null host. SCH58261 administration also significantly reduced intratumor TGF-β levels, thus supporting a key immune suppressive role of A2AR in our model. Altogether, these results indicate that in the absence of host P2X7R, the A2AR favors tumor growth immune suppression and neovascularization. This study shows a novel direct correlation between P2X7R and A2AR in oncogenesis and paves the way for new combined therapies promoting anti-cancer immune responses and reducing tumor vascularization.
三磷酸腺苷（ATP）和腺苷是肿瘤微环境的关键组成部分，它们发挥着相反但又互补的作用。ATP可因细胞损伤而释放，或由肿瘤细胞主动释放，随后降解为腺苷，腺苷在肿瘤微环境中蓄积。值得注意的是，虽然ATP主要通过P2X7受体（P2X7R）促进免疫清除反应，但细胞外腺苷作为一种强效免疫抑制剂，通过A2A受体（A2AR）促进新血管形成。迄今为止，尚未有研究探索肿瘤微环境中P2X7R与A2AR之间的相互作用。在此，我们发现，在接种B16 - F10黑色素瘤细胞的C57/bl6 P2X7基因敲除小鼠中，包括白细胞介素1β（IL - 1β）、肿瘤坏死因子α（TNF - α）、白细胞介素6（IL - 6）、白细胞介素12（IL - 12）、白细胞介素17（IL - 17）、干扰素γ（IFN - γ）在内的多种促炎细胞因子显著减少，而免疫抑制因子转化生长因子β（TGF - β）几乎增加了三倍。有趣的是，在P2X7基因敲除小鼠中生长的肿瘤上调了肿瘤相关及脾脏中的A2AR，这表明与缺乏P2X7R相关的免疫抑制可能依赖于A2AR的过表达。免疫组织化学分析显示，肿瘤细胞的A2AR表达增加，尤其是在坏死区域周围，并且血管内皮生长因子（VEGF）和内皮标志物CD31上调。A2AR拮抗剂SCH58261处理在P2X7野生型或基因敲除小鼠品系中同样降低了肿瘤生长。然而，SCH58261仅在P2X7基因敲除小鼠中降低了VEGF，从而支持了在P2X7基因敲除宿主中观察到的A2AR介导的血管生成增加这一假说。给予SCH58261也显著降低了肿瘤内TGF - β水平，从而支持了A2AR在我们模型中的关键免疫抑制作用。总之，这些结果表明，在宿主缺乏P2X7R的情况下，A2AR有利于肿瘤生长、免疫抑制和新血管形成。本研究揭示了P2X7R与A2AR在肿瘤发生过程中的一种新的直接关联，并为促进抗癌免疫反应和减少肿瘤血管生成的新联合疗法铺平了道路。
