Adipose-derived stem cells (ASCs) have received considerable attention in oncology because of the known direct link between obesity and cancer as well as the use of ASCs in reconstructive surgery after tumor ablation. Previous studies have documented how cancer cells commandeer ASCs to support their survival by altering extracellular matrix (ECM) composition and stiffness, migration, and metastasis. This study focused on delineating the effects of ASCs and adipocytes on the self-renewal of stem/progenitor cells and hierarchy of breast epithelial cells. The immortalized breast epithelial cell line MCF10A, ductal carcinoma in situ (DCIS) cell lines MCF10DCIS.com and SUM225, and MCF10A overexpressing SRC oncogene were examined using a mammosphere assay and flow cytometry for the effects of ASCs on their self-renewal and stem-luminal progenitor-differentiated cell surface marker profiles. Interestingly, ASCs promoted the self-renewal of all cell types except SUM225. ASC co-culture or treatment with ASC conditioned media (CM) altered the number of CD49fhigh/EpCAMlow basal/stem-like and CD49fmedium/EpCAMmedium luminal progenitor cells. Among multiple factors secreted by ASCs, IFN$$ and HGF displayed unique actions on epithelial cell hierarchy. IFN$$ increased stem/progenitor-like cells while simultaneously reducing the size of mammospheres, whereas HGF increased the size of mammospheres with an accompanying increase in luminal progenitor cells. ASCs expressed higher levels of HGF, whereas adipocytes expressed higher levels of IFN$$. Since luminal progenitor cells are believed to be prone for transformation, IFN$$ and HGF expression status of ASCs may influence susceptibility for developing breast cancer as well as on outcomes of autologous fat transplantation on residual/dormant tumor cells. IMPLICATIONS This study suggests that the ratio of adipose-derived stem cells to adipocytes influences cancer cell hierarchy, which may impact incidence and progression.