Malignant pleural mesothelioma (MPM) is an aggressive cancer, related to asbestos exposure, which has a dismal prognosis. MPM diagnosis is late and often challenging, suggesting the need to identify more reliable molecular biomarkers. Here, we set out to identify differentially expressed miRNAs in epithelioid, biphasic, and sarcomatoid MPMs versus normal mesothelium and explored specific miRNA contribution to mesothelial tumorigenesis. We screened an LNA™-based miRNA-microrray with 14 formalin-fixed paraffin-embedded (FFPE) MPMs and 6 normal controls. Through real-time qRT-PCR we extended the analysis of a miRNA subset and further investigated miR-320a role through state-of-the-art techniques. We identified 16 upregulated and 32 downregulated miRNAs in MPMs versus normal tissue, including the previously identified potential biomarkers miR-21, miR-126, miR-143, miR-145. We showed in an extended series that miR-145, miR-10b, and miR-320a levels can discriminate tumor versus controls with high specificity and sensitivity. We focused on miR-320a because other family members were found downregulated in MPMs. However, stable miR-320a ectopic expression induced higher proliferation and migration ability, whereas miR-320a silencing reduced these processes, not supporting a classic tumor-suppressor role in MPM cell lines. Among putative targets, we found that miR-320a binds the 3′-UTR of the immune inhibitory receptor ligand PDL1 and, consistently, miR-320a modulation affects PDL1 levels in MPM cells. Finally, we showed that p53 over-expression induces the upregulation of miR-320a, along with miR-200a and miR-34a, both known to target PDL1, and reduces PDL1 levels in MPM cells. Our data suggest that PDL1 expression might be due to a defective p53-regulated miRNA response, which could contribute to MPM immune evasion or tumorigenesis through tumor-intrinsic roles.

恶性胸膜间皮瘤 (MPM) 是一种侵袭性癌症，与石棉暴露有关，预后不佳。MPM 诊断较晚且通常具有挑战性，这表明需要识别更可靠的分子生物标志物。在这里，我们着手确定上皮样、双相和肉瘤样 MPM 与正常间皮中差异表达的 miRNA，并探索了特定 miRNA 对间皮肿瘤发生的贡献。我们使用 14 个福尔马林固定石蜡包埋 (FFPE) MPM 和 6 个正常对照筛选了基于 LNA™ 的 miRNA 微阵列。通过实时 qRT-PCR，我们扩展了 miRNA 子集的分析，并通过最先进的技术进一步研究了 miR-320a 的作用。我们在 MPMs 与正常组织中鉴定了 16 个上调和 32 个下调的 miRNA，包括先前鉴定的潜在生物标志物 miR-21，miR-126、miR-143、miR-145。我们在一个扩展系列中表明，miR-145、miR-10b 和 miR-320a 水平可以以高特异性和敏感性区分肿瘤与对照。我们专注于 miR-320a，因为其他家族成员在 MPM 中被发现下调。然而，稳定的 miR-320a 异位表达诱导更高的增殖和迁移能力，而 miR-320a 沉默减少了这些过程，不支持 MPM 细胞系中经典的肿瘤抑制作用。在假定的靶标中，我们发现 miR-320a 结合免疫抑制受体配体的 3'-UTR 稳定的 miR-320a 异位表达诱导更高的增殖和迁移能力，而 miR-320a 沉默减少了这些过程，不支持 MPM 细胞系中的经典肿瘤抑制作用。在假定的靶标中，我们发现 miR-320a 结合免疫抑制受体配体的 3'-UTR 稳定的 miR-320a 异位表达诱导更高的增殖和迁移能力，而 miR-320a 沉默减少了这些过程，不支持 MPM 细胞系中的经典肿瘤抑制作用。在假定的靶标中，我们发现 miR-320a 结合免疫抑制受体配体的 3'-UTRPDL1和始终如一的 miR-320a 调节影响 MPM 细胞中的 PDL1 水平。最后，我们表明 p53 过表达诱导 miR-320a 以及 miR-200a 和 miR-34a 的上调，两者都已知靶向PDL1，并降低 MPM 细胞中的 PDL1 水平。我们的数据表明，PDL1 表达可能是由于 p53 调节的 miRNA 反应有缺陷，这可能通过肿瘤内在作用导致 MPM 免疫逃避或肿瘤发生。