Dynamic re-wiring of apoptotic signaling networks enhances tumor cell killing by DNA damage. Homo sapiens

Crosstalk and complexity within signaling pathways has limited our ability to devise rational strategies for using network biology to treat human disease. This is particularly problematic in cancer where oncogenes that drive or maintain the tumorigenic state alter the normal flow of molecular information within signaling networks that control growth, survival and death. Understanding the architecture of oncogenic signaling pathways, and how these networks are re-wired by ligands or drugs, could provide opportunities for the specific targeting of oncogene-driven tumors. Here we use a systems biology-based approach to explore synergistic therapeutic strategies to optimize the killing of triple negative breast cancer cells, an incompletely understood tumor type with a poor treatment outcome. Using targeted inhibition of oncogenic signaling pathways combined with DNA damaging chemotherapy, we report the surprising finding that time-staggered EGFR inhibition, but not simultaneous co-administration, can dramatically sensitize the apoptotic response of a subset of triple-negative cells to conventional DNA damaging agents. A systematic analysis of the order and timing of inhibitor/genotoxin presentation—using a combination of high-density time-dependent activity measurements of signaling networks, gene expression profiles, cell phenotypic responses, and mathematical modeling—revealed an approach for altering the intrinsic oncogenic state of the cell through dynamic re-wiring of oncogenic signaling pathways. This process converts these cells to a less tumorigenic state that is more susceptible to DNA damage-induced cell death, through re-activation of an extrinsic apoptotic pathway whose function is suppressed in the oncogene-addicted state. Overall design: Three or 4 replicates of 3 different cell lines at time points 0minutes, 30minutes, 6 hours and 1 day after EGFR inhibition with erlotinib

信号通路内的信号串扰（crosstalk）与复杂性，限制了我们利用网络生物学（network biology）制定合理策略以治疗人类疾病的能力。这一问题在癌症研究中尤为突出：驱动或维持肿瘤发生状态的癌基因（oncogene），会改变调控细胞生长、存活与死亡的信号网络内的正常分子信息流转。解析致癌信号通路的结构，以及配体（ligand）或药物如何重塑此类信号网络，有望为靶向癌基因驱动的肿瘤提供新的干预思路。
本研究采用基于系统生物学（systems biology）的研究策略，探索协同治疗方案以优化三阴性乳腺癌（triple negative breast cancer, TNBC）细胞的杀伤效果；三阴性乳腺癌是一类尚未被充分阐明、治疗预后较差的肿瘤类型。研究团队通过靶向抑制致癌信号通路并联合DNA损伤性化疗（DNA damaging chemotherapy），得到了一项意外发现：时序错开的表皮生长因子受体（epidermal growth factor receptor, EGFR）抑制（而非同时联合给药），可显著使部分三阴性乳腺癌细胞的凋亡应答对传统DNA损伤剂增敏。
研究团队结合信号网络的高密度时序活性检测、基因表达谱分析、细胞表型应答检测与数学建模，对抑制剂/基因毒剂（genotoxin）的给药顺序与时机开展系统性分析，揭示了一种通过动态重塑致癌信号通路、改变细胞内在致癌状态的策略。该过程通过重新激活在癌基因成瘾状态下功能受抑制的外源性凋亡通路（extrinsic apoptotic pathway），将肿瘤细胞转化为致瘤性更低的状态，使其更易发生DNA损伤诱导的细胞死亡。
实验设计：针对3种不同细胞系，在使用厄洛替尼（erlotinib）抑制EGFR后的0分钟、30分钟、6小时及1天四个时间点，分别设置3或4次生物学重复。