Within breast tissue, adipose-derived stem cells (ADSCs) are responsible for maintaining cellular homeostasis. However, this potential can also contributed to the undesirable effect of tumor promotion. Therefore, this work deals with the effect of ionizing radiation on these interactions. In summary, the promoting effects of ADSCs on MCF-7 breast cancer cells were neutralized or reversed by a radiation treatment. Furthermore, ADSCs exhibit a medium radiation sensitivity associated with a functional DNA repair system.