The Functional Role of Immune-Related Intercellular Signalling Networks during Tissue Development and Cancer

Intercellular signalling networks drive tissue fundamental processes. Immune cells present a wide range of versatile functions and distinctive plasticity, which position them as tissue signalling-hubs during tissue development, homeostasis and cancer. Recent genomic advances have greatly improved our understanding of cell composition and states; however, investigation of the molecular signatures of intercellular crosstalk at the single-cell level remains limited. By applying novel single-cell RNA-sequencing technologies, as physically interacting-cell sequencing (PIC-seq), we were able to investigate cell states and gene signatures of the interactions of different cell types, and in various conditions. The mammary gland tissues go-through major morphological and cellular changes during life, therefore we hypothesized that investigating the immune-non-immune bidirectional crosstalk during its development will shed light on novel molecular pathways that control breast cancer induction and progression. Dense sampling and transcriptional profiling of immune and non-immune cells from mammary gland tissues of female mice carrying the polyomavirus middle T-antigen (MMTV-PyMT⁺) and their littermate controls (MMTV-PyMT^-), revealed differences in immune, stromal, and epithelial cell types and states between cancer and normal conditions. Projection of breast whole-tissue signalling networks along development and cancer revealed dynamics in immune-epithelial cell interactome. Moreover, immune-epithelium PIC-seq analysis revealed molecular signatures that are enriched only in the oncogene-carrier females, and are activated already during neoplasia stage, even before tumor appearance. Together, exploring tissue development, homeostasis and cancer from the point of view of immune-controlled signalling networks, has the potential to reveal novel diagnostic and therapeutic candidates with high biological and medical impact.