Preclinical models of breast cancer: Two-way shuttles for immune checkpoint inhibitors from and to patient bedside

The Food and Drug Administration has lately approved atezolizumab, anti-programmed death ligand 1 (PD-L1), to be used together with nanoparticle albumin-bound (nab) paclitaxel in treating patients with triple negative breast cancer (BC) expressing PD-L1. Nonetheless, immune checkpoint inhibitors (ICIs) are still challenged by the resistance and immune-related adverse effects evident in a considerable subset of treated patients without conclusive comprehension of the underlying molecular basis, biomarkers and tolerable therapeutic regimens capable of unleashing the anti-tumour immune responses. Stepping back to preclinical models is thus inevitable to address these inquiries. Herein, we comprehensively review diverse preclinical models of BC exploited in investigating ICIs underscoring their pros and cons as well as the learnt and awaited lessons to allow full exploitation of ICIs in BC therapy.