Neuregulin-1β Mitigates Doxorubicin-Induced Cardiotoxicity via

Anthracyclines such as doxorubicin (DOX) are widely used in cancer treatment, but their benefits are offset by dose-related cardiotoxicity. Neuregulin-1β (NRG1) has been studied as a cardioprotective factor, yet its mechanisms during DOX treatment, particularly in the presence of cancer, are not well understood. This study evaluated daily recombinant NRG1 co-administered with DOX in 4T1-tumor-bearing female BALB/c mice. The mice were randomized to saline, DOX (3 mg/kg i.p. on days 0, 3, 6, 9; cumulatively 12 mg/kg) or DOX + NRG1 (20 µg/kg i.p. daily, starting one day before DOX). Body weight and tumor growth were monitored throughout treatment. Cardiac structure and function were assessed by transthoracic echocardiography at baseline and before sacrifice. Mechanistic studies included left ventricular proteomics and single-cell RNA-seq. We also used human 3D cardiac microtissues and 2D primary cardiac fibroblast-enriched cultures under defined experimental conditions, with targeted fibroblast gene perturbations. We found that early DOX exposure induced systolic dysfunction and pathological remodeling, while daily NRG1 preserved the ejection fraction and attenuated structural changes without impairing anti-tumor efficacy. Proteomic analysis identified