Inflammatory signals secreted from the tumor microenvironment are thought to promote tumor growth and survival. It has been reported that stromal cells in the tumor microenvironment have similar characteristics to tumor-associated cells. In addition miRNAs play critical roles in various diseases, including cancer. In this study, we aimed to investigate the effects of co-culture of cancer cells and stromal cells isolated from normal and malignant breast tissue on each other and the possible effects of miRNAs on these interactions. The characterized stromal cells were co-cultured with an MDA-MB-231 cancer cell line. The proliferation capacity of the experimental groups was evaluated using the WST-1 assay. The expression of breast cancer-specific miRNAs and related genes were assessed by real-time PCR. ELISA assay was performed to determine the concentration of some cytokines and chemokines. We found that the microenvironment plays an important role in the development of cancer, confirming the changes in the expression of oncogenic and tumor suppressor miRNA and their target genes after co-culture with malignant stromal cells. As a result of the studies, specific gene expressions of related signaling pathways were detected in correlation with miRNA changes and the effects of tumor microenvironment on tumorigenesis were revealed in detail. miRNAs have been shown to play an important role in cancer development in recent studies. The idea that these small molecules can be used in diagnosis and treatment is becoming stronger day by day. We believe that new treatment approaches involving the tumor microenvironment and using miRNAs as markers are promising.