Collectively, our data revealed important DBD-CAP-mediated changes in tumor cell viability and expression of specific matrix effectors not only between breast cancer cells of different ER status (i.e. MCF-7/ER+ vs MDA-MB-231/ER- and Hs578T/ER-) but also between cells of the same ER profile (i.e. MDA-MB-231/ER- vs Hs578T/ER-), since MDA-MB-231/ER- cells appeared more resistant to the applied DBD-CAP treatments than the Hs578T/ER- cells. This evidence concerns the gene ESR1 and breast cancer.