A Novel Squaramide Derivative, HR-19011, Induces the Integrated Stress Response via the HRI-eIF2a-ATF4 Pathway, Effectively Inhibiting Hematologic Malignancies
We investigated the therapeutic potential and mechanisms of HR-19011, a novel eIF2a phosphorylation inducer, with a focus on its effects on the integrated stress response (ISR) pathway and cell cycle regulation in K562 cells. Our findings revealed that HR-19011 exerts its anticancer effects primarily through the activation of heme-regulated inhibitor (HRI), leading to the phosphorylation of eukaryotic translation initiation factor 2 (eIF2)a, the induction of ISR signaling, and subsequent G1/S cell cycle arrest. RNA sequencing analysis further highlighted significant changes in gene expression associated with the ISR pathway, particularly those involving the key components, activating transcription factor 4 (ATF4) and CHOP, underscoring the specific targeting of HRI by HR-19011. Additionally, HR-19011 suppressed the mTORC1 pathway, a critical regulator of cell growth and metabolism, through the downregulation of components such as phosphorylated (p)-S6K and p-4EBP1, mediated by ATF4 and CHOP. In vivo studies demonstrated that HR-19011 effectively inhibited tumor growth in a K562 xenograft model, without significant toxicity, and its broad efficacy across various hematologic malignancies further suggests its potential as a versatile anticancer agent. Our findings position HR-19011 as a promising candidate for targeting the HRI-eIF2a axis in cancer treatment, warranting further investigation and optimization for clinical application. Overall design: RNA-seq profiling of K562 cells treated with 0.1% DMSO (vehicle) or 10 µM HR-19011 for 24 hours