Bone marrow contains endothelial progenitor cells (EPCs) that, upon pro-angiogenic stimuli, migrate and differentiate into endothelial cells (ECs) and contribute to re-endothelialization and neo-vascularization. There are currently no reliable markers to characterize EPCs, leading to their inaccurate identification. In the past, we showed that, in a panel of tumors, some cells on the vessel wall co-expressed CD14 (monocytic marker) and CD31 (EC marker), indicating a putative differentiation route of monocytes into ECs. Herein, we disclosed monocytes as potential EPCs, using in vitro and in vivo models, and also addressed the cancer context. Monocytes acquired the capacity to express ECs markers and were able to be incorporated into blood vessels, contributing to cancer progression, by being incorporated in tumor neo-vasculature. Reactive oxygen species (ROS) push monocytes to EC differentiation, and this phenotype is reverted by cysteine (a scavenger and precursor of glutathione), which indicates that angiogenesis is controlled by the interplay between the oxidative stress and the scavenging capacity of the tumor microenvironment.

The immune microenvironment of breast cancer (BC) is composed by high macrophage infiltrates, correlated with the most aggressive subtypes. Tumour-associated macrophages (TAM) within the BC microenvironment are key regulators of immune suppression and BC progression. Nevertheless, several key questions regarding TAM polarisation by BC are still not fully understood. Recently, the modulation of the immune microenvironment has been described via the recognition of abnormal glycosylation patterns at BC cell surface. These patterns rise as a resource to identify potential targets on TAM in the BC context, leading to the development of novel immunotherapies. Herein, we will summarize recent studies describing advances in identifying altered glycan structures in BC cells. We will focus on BC-specific glycosylation patterns known to modulate the phenotype and function of macrophages recruited to the tumour site, such as structures with sialylated or N-acetylgalactosamine epitopes. Moreover, the lectins present at the surface of macrophages reported to bind to such antigens, inducing tumour-prone TAM phenotypes, will also be highlighted. Finally, we will discuss and give our view on the potential and current challenges of targeting these glycan-lectin interactions to reshape the immunosuppressive landscape of BC.

Targeted, combinatorial, and immunomodulatory therapies, such as antibody‐drug conjugates (ADCs) and immunomodulatory antibodies (Abs), are powerful weapons against tumor cells and immune cells within the tumor microenvironment (TME). Therefore, the evaluation of such therapies should be conducted in pre‐clinical models able to recapitulate the complex cellular and molecular crosstalk of the TME. To build‐in critical hallmarks of the TME, a breast cancer heterotypic 3D cell model (3D‐3) is devised using a microencapsulation strategy with an inert biomaterial (alginate) and agitation‐based cultures. Both stromal and immune components are added to multicellular tumor spheroids, therefore fostering cancer‐associated fibroblasts (CAFs) and tumor‐associated macrophages (TAMs) immunomodulatory interactions. The potential of the methodology to assess Ab‐based therapies is then addressed by employing a series of anti‐HER2‐based ADCs. ADCs induced tumor‐cell specific cytotoxicity toward HER2+ breast cancer spheroids while sparing HER2‐negative CAFs. In addition, an immunomodulatory blocking Ab against colony‐stimulating factor 1 receptor (CSF1R) decreases the expression of immunosuppressive and anti‐inflammatory markers in TAMs, like what is previously observed upon in vivo α‐CSF1R administration. Collectively, the human TME‐based 3D‐3 cell model is a suitable tool to evaluate the anti‐tumor and immunomodulatory potential of novel antibody‐based therapies directed against TME targets, such as cancer cells and macrophages.