套细胞淋巴瘤（MCL）是一种无法治愈的B细胞非霍奇金淋巴瘤，接受靶向治疗后复发的患者预后较差。蛋白质精氨酸甲基转移酶 5 (PRMT5) 是 B 细胞转化所必需的酶，可驱动多种致癌途径，并在 MCL 中过度表达。尽管 PRMT5 抑制 (PRT-382/PRT-808) 具有抗肿瘤活性，但在患者来源的异种移植 (PDX) MCL 模型中观察到耐药性。与未接受治疗的细胞相比，移植了这些 PRMT5 抑制剂抗性细胞的小鼠的存活率降低（p 值：0.005）。 MCL 细胞系对 PRMT5 抑制表现出不同的敏感性。使用 PRT-382，将细胞系分为敏感细胞系（n=4；IC50 20-140 nM）或原发耐药细胞系（n=4；340-1650 nM）。敏感 MCL 系的延长培养和药物升级产生了 PRMT5 抑制剂耐药细胞系（n=4；200-500 nM）。在没有药物的情况下长时间培养后，这种耐药表型仍然存在，并在 PRT-808 中观察到。在耐药 PDX 和细胞系模型中，原始 PRMT5 抑制剂 IC50 实现对称二甲基精氨酸减少，表明替代耐药途径的激活。相对于敏感或短期处理的细胞，耐药细胞系和 PDX 的批量 RNA 测序突显了包括 mTOR 信号传导在内的多种途径的共同上调（p 值 < 10-5 和 z 得分 >0.3 或 <0.3）。单细胞 RNA 测序分析表明，在耐药 MCL PDX 样本中，随着 mTOR 信号传导上调，整体基因表达发生了强烈变化。使用替西罗莫司靶向阻断 mTORC1 克服了 PRMT5 抑制剂耐药表型，在耐药 MCL 细胞系中显示出治疗协同作用，并提高了耐药 PDX 的生存率。版权所有 © 2023 美国血液学会。

Mantle cell lymphoma (MCL) is an incurable B-cell non-Hodgkin's lymphoma and patients who relapse on targeted therapies have a poor prognosis. Protein arginine methyltransferase 5 (PRMT5), an enzyme essential for B-cell transformation, drives multiple oncogenic pathways and is overexpressed in MCL. Despite the anti-tumor activity of PRMT5 inhibition (PRT-382/PRT-808), drug resistance was observed in a patient derived xenograft (PDX) MCL model. Decreased survival of mice engrafted with these PRMT5 inhibitor resistant cells versus treatment-naïve cells was observed (p-value: 0.005). MCL cell lines showed variable sensitivity to PRMT5 inhibition. Using PRT-382, cell lines were classified as sensitive (n=4; IC50 20-140 nM) or primary resistant (n=4; 340-1650 nM). Prolonged culture of sensitive MCL lines with drug escalation produced PRMT5 inhibitor resistant cell lines (n=4; 200-500 nM). This resistant phenotype persisted after prolonged culture in the absence of drug and was observed with PRT-808. In the resistant PDX and cell line models, symmetric dimethylarginine reduction was achieved at the original PRMT5 inhibitor IC50 suggesting activation of alternative resistance pathways. Bulk RNA sequencing of resistant cell lines and PDX relative to sensitive or short-term treated cells, respectively, highlighted shared upregulation of multiple pathways including mTOR signaling (p-value < 10-5 and z-score >0.3 or <0.3). Single cell RNA sequencing analysis demonstrated a strong shift in global gene expression with upregulation of mTOR signaling in resistant MCL PDX samples. Targeted blockade of mTORC1 with temsirolimus overcame the PRMT5 inhibitor resistant phenotype, displayed therapeutic synergy in resistant MCL cell lines, and improved survival of a resistant PDX.Copyright © 2023 American Society of Hematology.