Deregulation of transcription factors (TFs) leading to uncontrolled proliferation of tumor cells within the microenvironment represents a hallmark of cancer. However, the biological and clinical impact of transcriptional interference, particularly in multiple myeloma (MM) cells, remains poorly understood. The present study shows for the first time that MYC and JUNB, two crucial TFs implicated in MM pathogenesis, orchestrate distinct transcriptional programs. Specifically, our data revealed that expression levels of MYC, JUNB, and their respective downstream targets do not correlate and that their global chromatin-binding patterns are not significantly overlapping. Mechanistically, MYC expression was not affected by JUNB knockdown, and conversely, JUNB expression and transcriptional activity were not affected by MYC knockdown. Moreover, suppression of MYC levels in MM cells via targeting the master regulator BRD4 by either siRNA-mediated knockdown or treatment with the novel proteolysis targeting chimera (PROTAC) MZ-1 overcame bone marrow (BM) stroma cell/IL-6-induced MYC- but not MEK-dependent JUNB-upregulation and transcriptional activity. Consequently, targeting of the two non-overlapping MYC- and JUNB-transcriptoms by MZ-1 in combination with genetic or pharmacological JUNB-targeting approaches synergistically enhanced MM cell death, both in 2D and our novel dynamic 3D models of the BM milieu as well as in murine xenografts. In summary, our data emphasize the opportunity to employ MYC and JUNB dual-targeting treatment strategies in MM as another exciting approach to further improve patient outcomes.

转录因子 （TF） 的失调导致微环境中肿瘤细胞不受控制的增殖是癌症的标志。然而，转录干扰的生物学和临床影响，特别是在多发性骨髓瘤 （MM） 细胞中，仍然知之甚少。本研究首次表明 MYC 和 JUNB 是与 MM 发病机制有关的两个关键 TF，它们协调不同的转录程序。具体来说，我们的数据显示 MYC 、 JUNB 及其各自的下游靶标的表达水平不相关，并且它们的全局染色质结合模式没有显着重叠。从机制上讲，MYC 表达不受 JUNB 敲低的影响，相反，JUNB 表达和转录活性不受 MYC 敲低的影响。此外，通过 siRNA 介导的敲低或用新型蛋白水解靶向嵌合体 （PROTAC） MZ-1 处理来靶向主调节因子 BRD4 抑制 MM 细胞中的 MYC 水平，克服了骨髓 （BM） 基质细胞/IL-6 诱导的 MYC 但不依赖 MEK 的 JUNB 上调和转录活性。因此，MZ-1 靶向两个不重叠的 MYC 和 JUNB 转录组，结合遗传或药理学 JUNB 靶向方法，协同增强了 MM 细胞死亡，无论是在 2D 和我们新颖的 BM 环境动态 3D 模型中，还是在小鼠异种移植物中。总之，我们的数据强调了在 MM 中采用 MYC 和 JUNB 双靶点治疗策略的机会，这是进一步改善患者预后的另一种令人兴奋的方法。