Essential role of MALT1 protease activity in activated B cell-like diffuse large B-cell lymphoma

A key element for the development of suitable anti-cancer drugs is the identification of cancer-specific enzymatic activities that can be therapeutically targeted. Mucosa-associated lymphoid tissue transformation protein 1 (MALT1) is a proto-oncogene that contributes to tumorigenesis in diffuse large B-cell lymphoma (DLBCL) of the activated B-cell (ABC) subtype, the least curable subtype of DLBCL. Recent data suggest that MALT1 has proteolytic activity, but it is unknown whether this activity is relevant for tumor growth. Here we report that MALT1 is constitutively active in DLBCL lines of the ABC but not the GCB subtype. Inhibition of the MALT1 proteolytic activity led to reduced expression of growth factors and apoptosis inhibitors, and specifically affected the growth and survival of ABC DLBCL lines. These results demonstrate a key role for the proteolytic activity of MALT1 in DLBCL of the ABC subtype, and provide a rationale for the development of pharmacological inhibitors of MALT1 in DLBCL therapy. HBL-1 cells (n=8) were treated with IkB kinase beta inhibitor MLN120B (25 micromolar; Calbiochem) for 2h, 3h, 4h, 6h, 8h, 12h, 16h, and 24h (Cy5) and their gene expression compared to vehicle-treated cells (DMSO, Cy3). HBL-1 cells (n=4) and OCI-Ly3 cells (n=4) were treated with MALT1 inhibitor z-VRPR-fmk (50 micromolar; Alexis Biochemicals) for 6h, 12h, 24h, and 30h (Cy5) and their gene expression compared to vehicle-treated cells (DMSO, Cy3).

开发适配性抗肿瘤药物的核心关键之一，是识别可用于治疗靶向的癌症特异性酶活性。黏膜相关淋巴组织淋巴瘤转换蛋白1（Mucosa-associated lymphoid tissue transformation protein 1, MALT1）是一种原癌基因，可在活化B细胞（activated B-cell, ABC）亚型弥漫性大B细胞淋巴瘤（diffuse large B-cell lymphoma, DLBCL）中促进肿瘤发生——该亚型是DLBCL中最难治愈的亚型。现有研究表明MALT1具备蛋白水解活性，但目前尚不明确该活性是否与肿瘤生长相关。本研究证实，MALT1在ABC亚型DLBCL细胞系中呈组成型激活状态，而在GCB亚型细胞系中则无此现象。抑制MALT1的蛋白水解活性可降低生长因子与凋亡抑制剂的表达水平，并特异性影响ABC亚型DLBCL细胞系的增殖与存活能力。上述结果证明，MALT1的蛋白水解活性在ABC亚型DLBCL中发挥关键调控作用，同时为开发用于DLBCL治疗的MALT1药理学抑制剂提供了理论依据。

本研究开展如下实验：将HBL-1细胞（n=8）用IκB激酶β抑制剂MLN120B（25 μmol/L；Calbiochem）分别处理2小时、3小时、4小时、6小时、8小时、12小时、16小时及24小时（标记为Cy5），以二甲基亚砜（DMSO）处理的细胞作为溶剂对照（标记为Cy3），比较两组细胞的基因表达差异。此外，将HBL-1细胞（n=4）与OCI-Ly3细胞（n=4）用MALT1抑制剂z-VRPR-fmk（50 μmol/L；Alexis Biochemicals）分别处理6小时、12小时、24小时及30小时（标记为Cy5），同样以DMSO处理的细胞（标记为Cy3）作为对照，对比两组细胞的基因表达谱差异。