PURPOSE BRCA1 associated protein-1 (BAP1), a nuclear deubiquitinase thought to be involved in DNA double-strand break repair is frequently mutated in mesothelioma. Because poly-(ADP-ribose) polymerase inhibitors (PARPIs) induce synthetic lethality in BRCA1/2 mutant cancers, we evaluated whether BAP1 inactivating mutations confer sensitivity to PARPIs in mesothelioma and if combination therapy with temozolomide (TMZ) is beneficial. METHODS Ten patient-derived mesothelioma cell-lines were generated and characterized for BAP1 mutation status, protein expression, nuclear localization and sensitivity to the PARPIs olaparib and talazoparib alone or in combination with TMZ. BAP1 deubiquitinase (DUB) activity was evaluated by ubiquitin-AMC assay. BAP1-knockout (KO) mesothelioma cell-lines were generated by CRISPR/Cas9. Because Schlafen 11 (SLFN11) and O6-methylguanine-DNA methyltransferase (MGMT) also drive response to TMZ and PARPIs, we tested their expression and relationship with drug response. RESULTS BAP1 mutations and/or copy-number alterations were present in all ten cell lines. However, four cell lines exhibited intact DUB activity and two had nuclear BAP1 localization. Half-maximal inhibitory concentrations of olaparib and talazoparib ranged from 4.8 μM to >50 μM and 0.039 μM to >5 μM, respectively, classifying them into sensitive (two) or resistant (seven) cells, independent of their BAP1 status. Cell lines with BAP1-KO resulted in loss of BAP1 DUB activity but did not increase sensitivity to talazoparib. Response to PARPI tended to be associated with high SLFN11 expression, and combination with temozolomide increased sensitivity of cells with low or no MGMT expression. CONCLUSIONS BAP1 status does not determine sensitivity to PARPIs in patient-derived mesothelioma cell-lines. Combination of PARPI with TMZ may be beneficial for patients whose tumors have high SLFN11 and low or no MGMT expression.

中文翻译：

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间皮瘤细胞对 PARP 抑制剂的敏感性不依赖于 BAP1，但在具有高 Schlafen 11 和低 MGMT 表达的细胞中被替莫唑胺增强

目的 BRCA1 相关蛋白-1 (BAP1)，一种被认为参与 DNA 双链断裂修复的核去泛素化酶，在间皮瘤中经常发生突变。因为聚（ADP-核糖）聚合酶抑制剂（PARPI）在 BRCA1/2 突变癌症中诱导合成致死，我们评估了 BAP1 失活突变是否赋予间皮瘤中对 PARPI 的敏感性，以及与替莫唑胺（TMZ）联合治疗是否有益。方法 生成了 10 种源自患者的间皮瘤细胞系，并表征了 BAP1 突变状态、蛋白质表达、核定位以及对 PARPIs olaparib 和 talazoparib 单独或与 TMZ 组合的敏感性。BAP1 去泛素化酶 (DUB) 活性通过泛素-AMC 测定进行评估。BAP1 敲除 (KO) 间皮瘤细胞系由 CRISPR/Cas9 生成。因为 Schlafen 11 (SLFN11) 和 O6-甲基鸟嘌呤-DNA 甲基转移酶 (MGMT) 也驱动对 TMZ 和 PARPI 的反应，我们测试了它们的表达和与药物反应的关系。结果 BAP1 突变和/或拷贝数改变存在于所有十个细胞系中。然而，四个细胞系表现出完整的 DUB 活性，两个具有核 BAP1 定位。olaparib 和 talazoparib 的半数最大抑制浓度范围分别为 4.8 μM 至 >50 μM 和 0.039 μM 至 >5 μM，将它们分为敏感（两个）或抗性（七个）细胞，与它们的 BAP1 状态无关。具有 BAP1-KO 的细胞系导致 BAP1 DUB 活性丧失，但不会增加对 talazoparib 的敏感性。对 PARPI 的反应往往与高 SLFN11 表达相关，并与替莫唑胺组合增加了 MGMT 表达低或无表达的细胞的敏感性。结论 BAP1 状态并不能决定患者来源的间皮瘤细胞系对 PARPI 的敏感性。PARPI 与 TMZ 的组合可能对肿瘤具有高 SLFN11 和低或无 MGMT 表达的患者有益。