Encapsulation of hydroxyurea in exosomes derived from adipose mesenchymal stem cells enhances anticancer efficacy in breast cancer

• Hydroxyurea (HU) loaded into adipose-derived stem cell exosomes (HU-Exo) delivers a potent, targeted punch against breast cancer, overcoming drug resistance and boosting therapeutic precision. • HU-Exo slashes the effective drug dose by up to threefold, maximizing cancer cell death while minimizing potential side effects. • Treatment with HU-Exo not only triggers apoptosis and halts cancer cell division but also dramatically curbs metastasis by silencing key genes involved in tumor spread. • This innovative exosome-based strategy opens new doors for combination therapies, offering a smarter, safer approach to tackling aggressive breast cancers. Breast cancer treatment faces numerous challenges, including drug resistance and lack of precise drug targeting, which reduce therapeutic efficacy. This study investigated the potential use of hydroxyurea (HU), a potent antimetabolite, and exosomes derived from adipose-derived mesenchymal stem cells (AD-MSCs) as natural drug carriers to improve breast cancer therapy. Exosomes were isolated from AD-MSCs and characterized using immunophenotyping and various analytical techniques. HU was subsequently loaded into the exosomes via sonication, and its concentration was quantified by high-performance liquid chromatography (HPLC). Anticancer effects were evaluated through cell viability assays, apoptosis analysis, cell cycle profiling, and real-time PCR assessment of genes related to metastasis and angiogenesis. HU-loaded exosomes (HU-Exo) significantly enhanced cytotoxicity, reducing the IC50 value by up to threefold compared to free HU. HU-Exo also promoted apoptosis, induced S-phase cell cycle arrest, and inhibited migration of 4T1 breast cancer cells. Furthermore, expression of MMP2, MMP9, and VEGF was markedly downregulated. These results suggest that exosomes improve drug uptake and bypass drug resistance mechanisms, enabling dose reduction and minimizing side effects. This study introduces HU-Exo as a targeted and multifaceted drug delivery system capable of inhibiting breast tumor growth and metastasis, paving the way for the development of novel and combination therapies in the future.