METTL3 藉由 m6A 修飾調控泛素連接酶網絡以促進瀰漫大B細胞淋巴瘤之病程進展

Abstract

瀰漫大B細胞淋巴瘤（DLBCL）是一種高度侵襲性的血液惡性腫瘤，其特徵為治療耐受性（抗藥性）以及高頻率的復發。NF-κB訊號傳遞路徑的持續活化是驅動DLBCL進展的關鍵機制之一，且往往導致不良的治療預後。雖然基因體突變能解釋部分案例中的NF-κB活化現象，但仍無法全面說明在大量突變陰性個案中所觀察到的NF-κB路徑持續過度活化。這一臨床現實突顯了在DNA層級之外運作的調控機制之重要性，並提示了表觀轉錄組修飾（epitranscriptomic modifications）所扮演的關鍵角色。在本研究中，實驗結果顯示m6A甲基轉移酶METTL3的缺失會導致global m6A修飾水平下降，並伴隨著DLBCL細胞增殖受阻與細胞凋亡的增加。透過MeRIP-seq定序、RT-qPCR以及轉譯分析（polysome profiling）等機制探討，本研究提出了一種轉錄後調控網絡：METTL3藉由在其 mRNA 上調節 m6A 修飾，參與調控一系列關鍵E3泛素連接酶（包括LUBAC複合物成員 RNF31、RBCK1、SHARPIN，以及 MIB1和MIB2）的轉譯效率，進而影響 DLBCL 細胞的存活。患者資料庫分析顯示，METTL3及其下游連接酶在惡性度高的活化B細胞樣（ABC）亞型中呈現同步上調，且 METTL3具備作為獨立預後生物標記候選者的潛力。最後，利用小分子抑制劑 STM2457 抑制 METTL3，顯示出能與蛋白體抑制劑波特佐米（Bortezomib）產生治療協同效應，有助於提升細胞對蛋白體靶向療法的敏感性。總結來說，這些研究結果揭示了一種轉錄後調控機制，即METTL3經由泛素連接酶網絡的m6A修飾來維持DLBCL細胞的存活，從而提示METTL3可能作為治療DLBCL一種具可行性的標靶治療策略。

Diffuse large B-cell lymphoma (DLBCL) is a highly aggressive hematological malignancy frequently characterized by therapeutic resistance and frequent relapse. The constitutive activation of the NF-κB signaling pathway is a critical contributor driver of DLBCL progression, frequently contributing to poor treatment outcomes. While genomic mutations explain NF-κB activation in certain instances, they fail to account for the persistent pathway hyperactivation observed in a substantial portion of mutation-negative cases. These clinical observations suggest the importance of regulatory mechanisms operating beyond the DNA level, underscoring a potential role for epitranscriptomic modifications. In this study, we observe that the depletion of the "m" ^6 "A" methyltransferase METTL3 leads to a reduction in global "m" ^6 "A" modification levels, which is accompanied by suppressed cell proliferation and increased apoptosis in DLBCL cells. Through MeRIP-seq profiling, RT-qPCR, and translational efficiency analysis (polysome profiling), our data points to a post-transcriptional network potentially linked to DLBCL cell survival. Mechanistically, METTL3 appears to regulate a cluster of essential E3 ubiquitin ligases—including LUBAC subunits (RNF31, RBCK1, SHARPIN) and the MIB complex (MIB1, MIB2)—by modulating their "m" ^6 "A" deposition and supporting their translational efficiency. Clinical dataset analysis supports the translational relevance of this axis, revealing that METTL3 and its downstream targets are concurrently elevated in the aggressive activated B-cell-like (ABC) subtype and that METTL3 holds potential utility as an independent prognostic biomarker candidate. Finally, pharmacological inhibition using the small-molecule inhibitor STM2457 mirrors these phenotypes and demonstrates therapeutic synergy with the proteasome inhibitor Bortezomib, suggesting a method to sensitize DLBCL cells to proteasome-targeted therapies. Collectively, these findings provide insights into a post-transcriptional mechanism where METTL3 sustains DLBCL cell survival through the m6A modification of a ubiquitin ligase network, supporting METTL3 as a viable targeted therapeutic strategy for the treatment of DLBCL.