# Heterotypic 3D Model of Breast Cancer Based on Tumor, Stromal and Endothelial Cells: Cytokines Interaction in the Tumor Microenvironment

## TL;DR

This study creates a 3D breast cancer model to explore how tumor, stromal, and endothelial cells interact in the tumor microenvironment.

## Contribution

The study introduces a novel heterotypic 3D model to investigate cytokine interactions and immune evasion mechanisms in breast cancer.

## Key findings

- Stromal cells, especially fibroblasts, promote tumor cell aggregation and pseudovessel formation.
- Heterotypic spheroids with cancer-associated fibroblasts show a more aggressive and immunosuppressive phenotype.
- A cluster of cytokines (LIF, SDF-1, HGF, SCGFb) may regulate PD-L1 expression, suggesting a mechanism for immune evasion.

## Abstract

The recreation of the tumor microenvironment remains a significant challenge in the development of experimental cancer models. The present study constitutes an investigation into the interconnection between tumor, endothelial and stromal cells in heterotypic breast cancer spheroids. The generation of models was achieved through the utilization of MCF7, MDA-MB-231, and SK-BR-3 tumor cell lines, in conjunction with endothelial TIME-RFP cells and either cancer-associated (BrC4f) or normal (BN120f) fibroblasts, within ultra-low attachment plates. It was established that stromal cells, most notably fibroblasts, were conducive to the aggregation of tumor cells into spheroids and the formation of pseudovessels in close proximity to fibroblast bands. In contrast to the more aggressive tumor models MDA-MB-231 and SK-BR-3, microenvironment cells do not influence the migration ability of MCF7 tumor cells. Heterotypic spheroids incorporating CAFs demonstrated a more aggressive and immunosuppressive phenotype. Multiplex immunoassay analysis of cytokines, followed by STRING cluster analysis, was used to identify key processes including angiogenesis, invasion, stem cell maintenance, and immunosuppression. Furthermore, a cluster of cytokines (LIF, SDF-1, HGF, SCGFb) was identified as potentially involved in the regulation of PD-L1 expression by tumor cells. This finding reveals a potential mechanism of immune evasion and suggests new avenues for therapeutic investigation.