Characterisation of human in vitro tumour-associated macrophage models to define translational relevance.

Tumour-associated macrophages (TAMs) are key components of the tumour microenvironment with a demonstrated ability to modulate anti-tumour T-cell responses and immunotherapy outcomes. With increasing realisation that the M1/M2 paradigm does not reflect the complexity of macrophage phenotypes in cancer patients, an urgent need has arisen to develop improved, translatable in vitro models for human TAMs. To address this gap, we have screened conditioned media from a panel of tumour cell lines for their ability to induce suppressive marker upregulation on human monocyte-derived macrophages, as well as active T-cell immunosuppression. We performed secretome characterization of these tumour-conditioned media (TCM) to shed light on cancer cell-derived soluble factors that may contribute to TAM polarisation. Furthermore, we characterized the proteomic and transcriptomic signatures of macrophages exposed to either TCM or primary ascites fluid from ovarian cancer patients and performed bioinformatics analysis to determine the most translationally relevant models of TAMs. In summary, our work provides mechanistic insights on tumour-macrophage crosstalk in the context of establishing suppressive TAM phenotypes and addresses the long-standing gap of defining translationally relevant human in vitro TAM models.