Active targeting of nanoparticles to tumours can be achieved by conjugation with specific antibodies. Specific active targeting of the HER2 receptor is demonstrated in vitro and in vivo with a subcutaneous MCF-7 breast cancer mouse model with trastuzumab-functionalized gold nanoparticles. The number of attached antibodies per nanoparticle was precisely controlled in a way that each nanoparticle was conjugated with either exactly one or exactly two antibodies. As expected, in vitro we found a moderate increase in targeting efficiency of nanoparticles with two instead of just one antibody attached per nanoparticle. However, the in vivo data demonstrate that best effect is obtained for nanoparticles with only exactly one antibody. There is indication that this is based on a size-related effect. These results highlight the importance of precisely controlling the ligand density on the nanoparticle surface for optimizing active targeting, and that less antibodies can exhibit more effect.

Human epidermal growth factor receptor-2 (HER-2) overexpressing breast cancer is a breast cancer subtype characterized by high aggressiveness, high frequency of brain metastases and poor prognosis. HER-2, a glycoprotein belonging to the ErbB receptor family, is overexpressed on the outer membrane of cancer cells and has been an important therapeutic target for the development of targeted drugs, such as the monoclonal antibodies trastuzumab and pertuzumab. These therapies have been available in clinics for more than twenty years. However, despite the initial enthusiasm, a major issue emerged limiting HER-2 targeted therapy efficacy, i.e., the evolution of drug resistance, which could be tackled by nanotechnology. The aim of this review is to provide a first critical update on the different types of HER-2-targeted nanoparticles that have been proposed in the literature in the last decade for therapeutic purposes. We focus on the different targeting strategies that have been explored, their relative outcomes and current limitations that still need to be improved. Then, we review the nanotools developed as diagnostic kits, focusing on the most recent techniques, which allow accurate quantification of HER-2 levels in tissues, with the aim of promoting more personalized medicinal approaches in patients.

Patient-derived organoids (PDO) technology represents an emerging tool for the study of tumor biology and drug responsiveness, thus being useful to design personalized medicine approaches. Despite several studies and clinical trials are ongoing using PDO from colorectal and pancreatic cancer, only few research papers have been published exploiting PDO from breast cancer. Here, we have developed a new protocol to establish PDO from surgical and biopsy samples. Furthermore, we have set up also the methodologies adopted for culture and morphological evaluations. Surgical and core biopsy specimens collected from 33 patients with diagnosis of breast cancer have been processed using the protocols here described obtaining PDO from cancerous and healthy mammary tissue (when available) in a quick and easy way with good yields. The more critical aspects influencing the yield were the characteristic of the tissue of origin (healthy vs tumor tissue) and the amount of material obtained after enzymatic digestion process. Success rate from healthy samples was about 20,83%, while this percentage was higher in samples from cancer tissue (i.e. 87,5%). Also the morphological characterization of breast cancer PDO by brightfield and transmission electron microscopy has been reported. Despite obtaining some organoids from a surgical or biopsy specimen is not a difficult procedure, the establishment of a stable organoid line able to grow and replicate, suitable for long-term biobank storage, is not so obvious. A novel, simple and quick procedure to obtain PDO from surgical and biopsy samples is here proposed to achieve high success rate .

Cancer-associated fibroblasts (CAF) are the most abundant cells of the tumor stroma and they critically influence cancer growth through control of the surrounding tumor microenvironment (TME). CAF-orchestrated reactive stroma, composed of pro-tumorigenic cytokines and growth factors, matrix components, neovessels, and deregulated immune cells, is associated with poor prognosis in multiple carcinomas, including breast cancer. Therefore, beyond cancer cells killing, researchers are currently focusing on TME as strategy to fight breast cancer. In recent years, nanomedicine has provided a number of smart delivery systems based on active targeting of breast CAF and immune-mediated overcome of chemoresistance. Many efforts have been made both to eradicate breast CAF and to reshape their identity and function. Nano-strategies for CAF targeting profoundly contribute to enhance chemosensitivity of breast tumors, enabling access of cytotoxic T-cells and reducing immunosuppressive signals. TME rearrangement also includes reorganization of the extracellular matrix to enhance permeability to chemotherapeutics, and nano-systems for smart coupling of chemo- and immune-therapy, by increasing immunogenicity and stimulating antitumor immunity. The present paper reviews the current state-of-the-art on nano-strategies to target breast CAF and TME. Finally, we consider and discuss future translational perspectives of proposed nano-strategies for clinical application in breast cancer.