Plasma exosomes from individuals with type 2 diabetes drive breast cancer aggression in patient-derived organoids.

Women with obesity-driven diabetes (T2D) are predisposed to more aggressive breast cancers, yet patient metabolic status does not fully inform current standards of care. We previously identified plasma exosomes as key mediators of intercellular communication and drivers of tumor progression; however, their effect on immune cells within the tumor microenvironment (TME) remains unclear. To model this exosomal signaling, we developed a novel method to generate patient-derived organoids (PDOs) from breast tumor resections, uniquely preserving native tumor-infiltrating lymphocytes (TILs) for the first time. This modifiable and reproducible system provides a robust platform for studying human tumor-immune interactions within the TME . After 3-day exosome treatment, we assessed the impact of T2D-derived exosomes on PDOs via single-cell RNA sequencing. Exosomes from T2D patient plasma triggered a 13.6-fold expansion of immunosuppressive TILs compared to non-diabetic exosome controls. This immune dysfunction may permit the survival of micrometastases and undermine immune checkpoint therapies, a known challenge for cancer patients with comorbid T2D. Tumor-intrinsic analysis revealed a 1.5-fold increase in intratumoral heterogeneity and approximately 2.3-fold upregulation of epithelial-to-mesenchymal transition, invasiveness, and cancer stemness, consistent with enhanced tumor aggressiveness and metastatic potential of these PDOs. These findings demonstrate how metabolic dysregulation in T2D disrupts tumor-immune crosstalk, profoundly impairing anti-tumor immunity and driving cancer progression through a previously underappreciated exosomal signaling pathway. These insights into the TME could inform personalized treatments for patients with this comorbidity.