Mimicking the native microenvironment is vital for tumor engineering. Breast cancer is a highly heterogeneous disease with various molecular subtypes exhibiting distinct biological behaviors and treatment responsiveness. The heterogeneity of extracellular matrix (ECM) of breast cancer has remained largely unexplored and underestimated. The present study addressed this issue by comparing the composition, architecture, and functional roles of ECMs derived from breast cancers of two molecular subtypes, which are luminal-A breast cancer (less aggressive, ERα+)-derived ECM (LA-ECM) and triple-negative breast cancer (high aggressive, ERα-)-derived ECM (TN-ECM). Compared with normal breast tissue-derived ECMs (B-ECM), tumor-derived ECMs showed higher contents of pro-collagen I, fibronectin, and laminin, in addition with a significantly altered architecture. Transcriptome sequencing revealed that, compared with those cultured with B-ECM, MCF7 cells (an estrogen receptor (ER)α + luminal-A breast cancer cell line) cultured with LA-ECM and TN-ECM showed approximately 9.65 % and 9.04 % changes in the expression of all detected genes, respectively. The TN-ECM induced proliferation, promoted epithelial-to-mesenchymal transition, downregulated ERα expression, and reduced endocrine treatment sensitivity of MCF7. Above results have elucidated the role of phenotype-specific tumor ECM in cell phenotype maintenance, treatment sensitivity, and cancer progression, which highlighted the importance of ECM heterogeneity as well as its role in tumor microenvironment engineering and drug screening.Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.