Purpose

Stemming from a myriad of genetic and epigenetic alterations, triple-negative breast cancer (TNBC) is tied to poor clinical outcomes and aspires for individualized therapies. Here we investigated the therapeutic potential of co-inhibiting integrin-dependent signaling pathway and BRD4, a transcriptional and epigenetic mediator, for TNBC.

Methods

Two independent patient cohorts were subjected to bioinformatic and IHC examination for clinical association of candidate cancer drivers. The efficacy and biological bases for co-targeting these drivers were interrogated using cancer cell lines, a protein kinase array, chemical inhibitors, RNAi/CRISPR/Cas9 approaches, and a 4 T1-Balb/c xenograft model.

Results

We found that amplification of the chromosome 8q24 region occurred in nearly 20% of TNBC tumors, and that it coincided with co-upregulation or amplification of c-Myc and FAK, a key effector of integrin-dependent signaling. This co-upregulation at the mRNA or protein level correlated with a poor patient survival (p < 0.0109 or p < 0.0402, respectively). Furthermore, we found that 14 TNBC cell lines exhibited high vulnerabilities to the combination of JQ1 and VS-6063, potent pharmacological antagonists of the BRD4/c-Myc and integrin/FAK-dependent pathways, respectively. We also observed a cooperative inhibitory effect of JQ1 and VS-6063 on tumor growth and infiltration of Ly6G⁺ myeloid-derived suppressor cells in vivo. Finally, we found that JQ1 and VS-6063 cooperatively induced apoptotic cell death by altering XIAP, Bcl2/Bcl-xl and Bim levels, impairing c-Src/p130Cas-, PI3K/Akt- and RelA-associated signaling, and were linked to EMT-inducing transcription factor Snail- and Slug-dependent regulation.

Conclusion

Based on our results, we conclude that the BRD4/c-Myc- and integrin/FAK-dependent pathways act in concert to promote breast cancer cell survival and poor clinical outcomes. As such, they represent promising targets for a synthetic lethal-type of therapy against TNBC.

中文翻译：

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BRD4 调节三阴性乳腺癌对靶向整合素依赖性信号通路的脆弱性

目的

由于无数的遗传和表观遗传改变，三阴性乳腺癌 (TNBC) 与不良的临床结果相关，并渴望个体化治疗。在这里，我们研究了共同抑制整合素依赖性信号通路和 BRD4（一种转录和表观遗传介质）对 TNBC 的治疗潜力。

方法

对两个独立的患者队列进行了生物信息学和 IHC 检查，以了解候选癌症驱动因素的临床关联。使用癌细胞系、蛋白激酶阵列、化学抑制剂、RNAi/CRISPR/Cas9 方法和 4 T1-Balb/c 异种移植模型研究了共同靶向这些驱动因素的功效和生物学基础。

结果

我们发现染色体 8q24 区域的扩增发生在近 20% 的 TNBC 肿瘤中，并且它与 c-Myc 和 FAK 的共同上调或扩增一致，FAK 是整合素依赖性信号传导的关键效应物。这种在 mRNA 或蛋白质水平上的共同上调与较差的患者存活率相关（分别为p  < 0.0109 或p  < 0.0402）。此外，我们发现 14 种 TNBC 细胞系对 JQ1 和 VS-6063 的组合表现出高度脆弱性，它们分别是 BRD4/c-Myc 和整合素/FAK 依赖性通路的强效药理学拮抗剂。^{我们还观察到 JQ1 和 VS-6063 对肿瘤生长和 Ly6G +}浸润的协同抑制作用体内髓源性抑制细胞。最后，我们发现 JQ1 和 VS-6063 通过改变 XIAP、Bcl2/Bcl-xl 和 Bim 水平协同诱导凋亡细胞死亡，损害 c-Src/p130Cas-、PI3K/Akt- 和 RelA 相关信号，并与EMT 诱导转录因子 Snail 和 Slug 依赖性调节。

结论

根据我们的结果，我们得出结论，BRD4/c-Myc 和整合素/FAK 依赖性通路协同作用以促进乳腺癌细胞存活和不良临床结果。因此，它们代表了针对 TNBC 的合成致死型治疗的有希望的目标。