Department of Experimental Immunology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, the Netherlands.
Amsterdam Institute for Infection and Immunity, Cancer Immunology, Amsterdam, the Netherlands.
Leukemia. 2023 Jun;37(6):1268-1276. doi: 10.1038/s41375-023-01898-w. Epub 2023 Apr 26.
Chronic lymphocytic leukemia (CLL) cells upregulate Bcl-2 proteins within the lymph node (LN) microenvironment. Signaling via B-cell receptor, Toll-like receptors and CD40 collectively reduce sensitivity to the BCL-2 inhibitor venetoclax. Time-limited treatment with venetoclax plus the BTK-inhibitor ibrutinib results in deep remissions, but how this combination affects LN-related signaling is not yet completely clear. Therefore, samples obtained from the HOVON141/VISION phase 2 clinical trial were used to analyze this. Two cycles of lead-in ibrutinib monotherapy resulted in decreased protein expression of Bcl-2 proteins in circulating CLL cells. Strikingly, at this timepoint CD40-induced venetoclax resistance was strongly attenuated, as was expression of CD40. Since CD40 signaling occurs within the CLL LN, we tested various LN-related signals that could affect CD40 signaling. While BCR stimulation had only a minor effect, TLR9 stimulation via CpG led to significantly increased CD40 expression and importantly, reverted the effects of ibrutinib treatment on venetoclax sensitivity by inducing overall protein translation. Together, these findings identify a novel effect of ibrutinib: interruption of TLR9-induced CD40 upregulation and translation of pro-survival proteins. This mechanism may potentially further inhibit priming of CLL cells in the LN microenvironment for venetoclax resistance.
慢性淋巴细胞白血病 (CLL) 细胞在淋巴结 (LN) 微环境中上调 Bcl-2 蛋白。B 细胞受体、Toll 样受体和 CD40 的信号共同降低了对 BCL-2 抑制剂 venetoclax 的敏感性。venetoclax 联合 BTK 抑制剂 ibrutinib 的限时治疗可导致深度缓解,但该联合治疗如何影响 LN 相关信号尚不完全清楚。因此,使用来自 HOVON141/VISION 二期临床试验的样本进行了分析。两周期的先导 ibrutinib 单药治疗导致循环 CLL 细胞中 Bcl-2 蛋白的蛋白表达减少。引人注目的是,此时 CD40 诱导的 venetoclax 耐药性明显减弱,CD40 的表达也减弱。由于 CD40 信号发生在 CLL LN 内,我们测试了各种可能影响 CD40 信号的 LN 相关信号。虽然 BCR 刺激仅有轻微影响,但 CpG 诱导的 TLR9 刺激导致 CD40 表达显著增加,重要的是,通过诱导总体蛋白翻译,逆转了 ibrutinib 治疗对 venetoclax 敏感性的影响。这些发现共同确定了 ibrutinib 的一种新作用:中断 TLR9 诱导的 CD40 上调和生存蛋白的翻译。该机制可能潜在地进一步抑制 LN 微环境中 CLL 细胞对 venetoclax 耐药性的启动。