Background/Objectives: The interaction between brain-metastasizing melanoma cells and surrounding microglia shapes the immune tumor microenvironment and influences tumor progression. Gene expression analysis revealed that sphingosine-1-phosphate receptor 1 (S1PR1), encoding the S1P1 receptor, is upregulated in microglia upon interaction with melanoma cells. Here, we investigated the functions of S1P1 in microglia and its contribution to melanoma–microglia crosstalk. Methods: We examined the effects of S1P1 inhibition on microglia and four brain-metastasizing human melanoma cell lines in monocultures and co-cultures using the selective S1P1 antagonist NIBR0213 andS1PR1gene knockdown. Results: We found that melanoma-secreted IL-6 upregulatedS1PR1expression in microglia. S1P1 inhibition increased expression of CD32, CD150, and CD163 in microglia; however, CD150 and CD163 upregulation was abolished in the presence of melanoma cells. S1P1 inhibition downregulated immunosuppressive and anti-inflammatory factors in microglia, includingCD274,SOCS3,TGFBR1,TGFBR2, and JunB, promoting a pro-inflammatory phenotype. It also reduced viability of both melanoma and microglia cells, inducing apoptosis in melanoma-associated microglia, possibly via downregulation of CH25H, an upstream regulator of SREBPs. In co-cultures, melanoma cells were more sensitive than microglia to NIBR0213-induced growth arrest. In 3D spheroid cultures, NIBR0213 delayed melanoma–microglia aggregation. Combined treatment with the BRAF inhibitor Vemurafenib and NIBR0213 enhanced Vemurafenib efficacy in three of four melanoma lines. Conclusions: S1P1 contributes to the immunosuppressive phenotype of microglia. Inhibiting the S1P/S1P1 axis impairs viability and crosstalk between melanoma cells and tumor-activated microglia, offering a potential therapeutic strategy for melanoma brain metastases.
背景/目的：脑转移性黑色素瘤细胞与周围小胶质细胞之间的相互作用塑造了免疫肿瘤微环境并影响肿瘤进展。基因表达分析显示，在与黑色素瘤细胞相互作用时，编码S1P1受体的鞘氨醇-1-磷酸受体1（S1PR1）在小胶质细胞中表达上调。本研究旨在探讨S1P1在小胶质细胞中的功能及其对黑色素瘤-小胶质细胞相互作用的影响。方法：通过选择性S1P1拮抗剂NIBR0213和S1PR1基因敲降技术，在单培养及共培养体系中检测S1P1抑制对小胶质细胞及四种脑转移性人黑色素瘤细胞系的影响。结果：研究发现黑色素瘤分泌的IL-6可上调小胶质细胞中S1PR1的表达。抑制S1P1能增加小胶质细胞中CD32、CD150和CD163的表达，但在黑色素瘤细胞存在时，CD150和CD163的上调被抑制。S1P1抑制下调了小胶质细胞中的免疫抑制及抗炎因子（包括CD274、SOCS3、TGFBR1、TGFBR2和JunB），促进其向促炎表型转化。同时，S1P1抑制降低了黑色素瘤细胞和小胶质细胞的活力，可能通过下调SREBPs上游调控因子CH25H，诱导黑色素瘤相关小胶质细胞发生凋亡。在共培养体系中，黑色素瘤细胞对NIBR0213诱导的生长抑制比小胶质细胞更敏感。在三维球体培养中，NIBR0213延缓了黑色素瘤-小胶质细胞聚集。BRAF抑制剂维莫非尼与NIBR0213联合治疗，在四种黑色素瘤细胞系中有三种增强了维莫非尼的疗效。结论：S1P1参与小胶质细胞免疫抑制表型的形成。抑制S1P/S1P1轴可削弱黑色素瘤细胞与肿瘤活化小胶质细胞的活力及相互作用，为黑色素瘤脑转移提供了潜在治疗策略。
肿瘤(癌症)患者之家