Tumor organoids are tridimensional cell culture systems that are generated in vitro from surgically resected patients’ tumors. They can be propagated in culture maintaining several features of the tumor of origin, including cellular and genetic heterogeneity, thus representing a promising tool for precision cancer medicine. Here, we established patient-derived tumor organoids (PDOs) from different breast cancer subtypes (luminal A, luminal B, human epidermal growth factor receptor 2 (HER2)-enriched, and triple negative). The established model systems showed histological and genomic concordance with parental tumors. However, in PDOs, the ratio of diverse cell populations was frequently different from that originally observed in parental tumors. We showed that tumor organoids represent a valuable system to test the efficacy of standard therapeutic treatments and to identify drug resistant populations within tumors. We also report that inhibitors of mechanosignaling and of Yes-associated protein 1 (YAP) activation can restore chemosensitivity in drug resistant tumor organoids.

TP53 missense mutations leading to the expression of mutant p53 oncoproteins are frequent driver events during tumorigenesis. p53 mutants promote tumor growth, metastasis and chemoresistance by affecting fundamental cellular pathways and functions. Here, we demonstrate that p53 mutants modify structure and function of the Golgi apparatus, culminating in the increased release of a pro-malignant secretome by tumor cells and primary fibroblasts from patients with Li-Fraumeni cancer predisposition syndrome. Mechanistically, interacting with the hypoxia responsive factor HIF1α, mutant p53 induces the expression of miR-30d, which in turn causes tubulo-vesiculation of the Golgi apparatus, leading to enhanced vesicular trafficking and secretion. The mut-p53/HIF1α/miR-30d axis potentiates the release of soluble factors and the deposition and remodeling of the ECM, affecting mechano-signaling and stromal cells activation within the tumor microenvironment, thereby enhancing tumor growth and metastatic colonization.

Breast cancers with a stiff extracellular matrix (ECM) frequently evade immune surveillance through mechanisms that remain incompletely understood. Here, we identify a mechanosensitive immune-evasion pathway governed by the phosphorylation-dependent prolyl isomerase Pin1. We show that ECM rigidity stabilizes Pin1 and promotes its nuclear accumulation in cancer cells, where it preserves heterochromatin organization and nuclear envelope integrity by sustaining HP1α-Lamin interactions, thereby suppressing transposable element (TE) activity. Pin1 loss induces early heterochromatin relaxation and LINE1 reactivation, activating the cGAS/STING/type I interferon pathway. Pin1 depletion further promotes TE-derived neoantigen generation and broadly remodels the tumor immune microenvironment, eliciting innate and adaptive immune responses that enhance tumor clearance. Genetic Pin1 depletion, or pharmacological inhibition with clinically available drugs, sensitizes fibrotic, immune-cold tumors to immune checkpoint blockade. These findings uncover a mechano-genomic mechanism of immune evasion in breast cancer and establish Pin1 as a therapeutic target to restore tumor immunogenicity and improve immunotherapy efficacy.