Tissue-stiffness-driven platelet activation emerges as a potential target for breast cancer prevention and treatment

High mammographic breast density is a strong independent risk factor for sporadic breast cancer, yet involved mechanisms remain poorly defined. The extracellular compartment plays a critical role in the intercellular communication during tumor initiation and progression. Although several mechanosensitive pathways have been described, the role of platelets (PLTs) in stiffness-driven signaling in the breast is unknown.

Extracellular soluble proteins were sampled in situ from live breast tissue using microdialysis. A total of 108 postmenopausal women were included: women with nondense or dense breasts, women with dense breasts randomized to low-dose acetylsalicylic acid (ASA; 160 mg/day) or no treatment, and patients with estrogen receptor-positive (ER⁺) breast cancer. Breast density was assessed by magnetic resonance imaging. High-dimensional proteomic profiling of 1,158 proteins was performed using proximity extension assays. To investigate stiffness-dependent PLT responses, cells were cultured in a 3D in vitro system with tunable matrix stiffness generated by cross-linked hyaluronic acid, modeling nondense and dense breast tissue.

Dense breast tissue exhibited a distinct extracellular proteomic signature enriched for proteins associated with platelet activation, along with alterations in several immunomodulatory pathways. Several PLT-associated proteins were also elevated in ER⁺ breast cancers, supporting their clinical relevance. Post hoc exploratory proteomic analysis of samples from women treated with low-dose ASA did not reveal modulation of these proteins, suggesting that stiffness-induced PLT activation may occur via mechanotransduction rather than biochemical pathways in vivo. Consistently, in the 3D in vitro model, increased matrix stiffness representative of dense breasts promoted a procoagulant PLT phenotype without corresponding changes in classical activation markers.

Tissue stiffness is a critical regulator of PLT mechanotransduction in dense breast tissue, contributing to a microenvironment permissive for cancer progression. These findings highlight PLT mechanobiology as a potential target for breast cancer prevention and therapy.

EudraCT: 2017-000317-22.