A Novel 3D Model Co‐Culturing Breast Cancer Cells in Direct Contact with Patient‐Derived Mature Adipocytes Demonstrates Cell‐Type Specific Alterations in Phenotype and Chemosensitivity

Mature adipocytes within the breast tumour microenvironment contribute a significant role in malignant progression. At the invasive front of breast tumours, mature adipocytes undergo morphological and phenotypic changes and may provide metabolic support to fuel tumour growth and spread. However, investigations into mature adipocyte-breast cancer interactions have been limited by the lack of suitable in vitro models. Here, we developed an innovative 3D in vitro co-culture system allowing direct contact between patient-derived mature breast adipocytes and breast cancer cell lines, to systematically examine cell-cell interactions over 21 days. In co-culture with triple negative breast cancer cells (MDA-MB-231), mature adipocytes exhibited loss of Perilipin 1 (PLIN1) expression and were associated with reduced chemotherapy responsiveness and increased Major Vault Protein (MVP) abundance. In contrast, Luminal A (MCF7) breast cancer cells displayed increased expression of mesenchymal markers (N-cadherin and Vimentin), consistent with a partial epithelial to mesenchymal transition. The direct 3D co-culture model developed by this work provides a novel platform to study breast cancer subtype-specific interactions between mature adipocytes and cancer cells, revealing interactions associated with chemotherapy responsiveness and malignant progression.