Exploring the heterogeneity of tumor-associated macrophages in murine models

In our project, we are studying the role of tumor-associated macrophages (TAMs) in pancreatic cancer (PDAC). TAMs are known to contribute to poor cancer prognosis, but the biological mechanisms behind this association remain unclear. TAMs are often the most abundant immune cells within tumors, making them an attractive target for potential immunotherapies. However, the heterogeneity of TAMs makes them challenging to study. We have previously identified that cell-to-cell communication, inflammation, ontogeny, and time contribute to macrophage heterogeneity. To investigate TAM heterogeneity in cancer, we use a fate-mapping mouse model based on the Ms4a3 gene, which labels all monocyte-derived cells (MoM). This model allows us to distinguish between MoM and embryonic macrophages (EmM) in various tissues and cancer models. We also developed an inducible time-stamping model to track monocytes as they differentiate into MoM. This model is beneficial for studying tumors that can grow “silently” over long periods, with a continuous influx of monocytes recruited from the bloodstream. Using this model, we focused on monocyte-derived TAMs (MoTAM) and performed single-cell RNA sequencing to identify four main clusters of monocytes and MoTAM. Pseudotime analysis revealed a trajectory from monocytes to TAMs, passing through an intermediate step we carefully annotated. In addition, we used the InfinityFlow analytical pipeline to assess the protein expression of surface markers on these macrophage clusters. The following steps in our research will involve targeting these distinct macrophage populations to modulate tumor growth and gain deeper insights into PDAC progression.