Background:The immunomodulatory molecule PD-L1 and its immunological tolerance-mediating interaction with the PD-1 receptor on many immune effector cells represent one of the most important tumor immune checkpoint axes in antibody-based anti-tumor therapies. Furthermore, PD-L1 is subject to alternative splicing, whereby, in addition to the membrane-bound PD-L1, secreted PD-L1 is also formed as an additional splice variant. This also exerts its effects in the tumor microenvironment, even away from the actual tumor cells, and contributes additional benefits to immune evasion of the tumor.Methods:To examine the association of the splicing factor SRSF2 with the PD-L1 splicing pattern, respective SRSF2 overexpression and knockdown experiments were performed. The precise characterization of SRSF2 followed in human kidney tissue samples and RCCs, including immunofluorescence staining. The impact of the known oncogenic SRSF2 on the host cell transcriptome was further analyzed by RNA sequencing analyses in SRSF2 overexpression and knockdown experiments.Results:In this original research article, the trans splicing factor SRSF2 is identified to be associated with the shift in the alternative splicing pattern of PD-L1 towards the secreted splice variant. The impact of SRSF2 on the cellular transcriptome was demonstrated, and its involvement in the process of malignant transformation, which is obviously also directly linked to immune evasion.Discussion:The optimization of anti-tumor therapies based on monoclonal antibodies against immunomodulatory axes such as PD-1 and PD-L1, including necessary cost reductions, requires the detailed characterization of the gene expression and gene regulation of such molecules, as well as comprehensive molecular biological diagnostics of the tumor sample before putative therapy formulations, e.g., antibody panel collection.Conclusion:Thus, both the amount of PD-L1 protein produced and its splicing pattern are crucial for therapy success and for selecting the most effective therapeutic antibodies.
背景：免疫调节分子PD-L1及其与多种免疫效应细胞上PD-1受体介导的免疫耐受相互作用，是基于抗体的抗肿瘤治疗中最重要的肿瘤免疫检查点轴之一。此外，PD-L1存在可变剪接现象，除膜结合型PD-L1外，分泌型PD-L1作为另一种剪接变体同样形成。该变体在肿瘤微环境中（甚至远离实际肿瘤细胞区域）发挥作用，为肿瘤的免疫逃逸提供了额外优势。 方法：为探究剪接因子SRSF2与PD-L1剪接模式的关联，本研究分别进行了SRSF2过表达和敲低实验。通过免疫荧光染色等技术，对人肾组织样本和肾细胞癌中SRSF2进行了精确表征。进一步通过RNA测序分析，在SRSF2过表达与敲低实验中研究了该已知致癌因子对宿主细胞转录组的影响。 结果：本原创研究首次发现反式剪接因子SRSF2与PD-L1可变剪接模式向分泌型剪接变体的转变存在关联。研究证实了SRSF2对细胞转录组的影响，并揭示其参与恶性转化过程，该过程显然与免疫逃逸机制存在直接联系。 讨论：基于PD-1/PD-L1等免疫调节轴的单克隆抗体抗肿瘤疗法的优化（包括必要的成本控制），需要对此类分子的基因表达与调控机制进行精细表征，并在拟定治疗方案（如抗体组合筛选）前对肿瘤样本进行全面的分子生物学诊断。 结论：因此，PD-L1蛋白的表达量及其剪接模式对治疗成功与否及选择最有效的治疗性抗体均具有决定性意义。
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