LSD1 mediates AKT activity in PIK3CA mutant colorectal cancer [RNA-Seq]. LSD1 mediates AKT activity in PIK3CA mutant colorectal cancer [RNA-Seq]

Activation of the epithelial-mesenchymal transition (EMT) program is a critical mechanism for initiating cancer progression and migration. Colorectal cancers (CRCs) contain many genetic and epigenetic alterations that can contribute to EMT. Mutations activating the PI3K/AKT signaling pathway are observed in >40% of patients with CRC contributing to increased invasion and metastasis. Little is known about how oncogenic signaling pathways such as PI3K/AKT synergize with chromatin modifiers to activate the EMT program. Lysine Specific Demethylase 1 (LSD1) is a chromatin-modifying enzyme that is overexpressed in colorectal cancer (CRC) and enhances cell migration. In this study we determine that LSD1 expression is significantly elevated in CRC patients with mutation of the catalytic subunit of PI3K, PIK3CA, compared to CRC patients with WT PIK3CA. LSD1 enhances activation of the AKT kinase in CRC cells through a non-catalytic mechanism, acting as a scaffolding protein for the transcription-repressing CoREST complex. Additionally, growth of PIK3CA mutant CRC cells is uniquely dependent on LSD1. Knockdown or CRISPR knockout of LSD1 blocks AKT-mediated stabilization of the EMT-promoting transcription factor Snail and effectively blocks AKT-mediated EMT and migration. Overall we uniquely demonstrate that LSD1 mediates AKT activation in response to growth factors and oxidative stress, and LSD1-regulated AKT activity promotes EMT-like characteristics in a subset of PIK3CA mutant cells. Overall design: RNA sequencing profiles were generated for LSD1 knockdown and GSK-LSD1 treated SW480 cells as well as LSD1 knockdown in HT29 cells compared to controls.

上皮间质转化（Epithelial-Mesenchymal Transition, EMT）程序的激活是启动癌症进展与迁移的关键机制。结直肠癌（Colorectal Cancers, CRCs）存在诸多可促进EMT发生的遗传与表观遗传改变。在超过40%的CRC患者中，可观察到PI3K/AKT信号通路的激活性突变，此类突变可加剧肿瘤侵袭与转移。目前学界对PI3K/AKT这类致癌信号通路如何与染色质修饰因子协同激活EMT程序仍知之甚少。
赖氨酸特异性去甲基化酶1（Lysine Specific Demethylase 1, LSD1）是一类在CRC中过表达的染色质修饰酶，可增强细胞迁移能力。本研究发现，相较于携带野生型（Wild Type, WT）PIK3CA的CRC患者，携带PI3K催化亚基PIK3CA突变的CRC患者，其肿瘤组织中LSD1的表达水平显著升高。LSD1可通过非催化机制增强CRC细胞内AKT激酶的激活，其作用模式为作为转录抑制复合物CoREST的支架蛋白。
此外，携带PIK3CA突变的CRC细胞的生长具有独特的LSD1依赖性。敲低或CRISPR敲除LSD1，可阻断AKT介导的EMT促进转录因子Snail的稳定性维持，并有效抑制AKT介导的EMT与细胞迁移。
本研究首次证实，LSD1可介导生长因子与氧化应激刺激下的AKT激活，且在部分PIK3CA突变的细胞中，LSD1调控的AKT活性可促进类EMT特征的形成。
实验整体设计：本研究对LSD1敲低、GSK-LSD1处理的SW480细胞，以及HT29细胞中的LSD1敲低样本进行了RNA测序，并与相应对照组开展对比分析。