ESRP1 and breast neoplasm: In the cohort of primary breast tumor specimens – more heterogeneous cell populations – we find a positive but weak correlation (ρ ≤ 0.25) between mtDNA content and ESRP1, SNAI1 and TGFB1. In in vitro studies, a reduction in mtDNA content resulted in decreased ESRP1 protein levels but, contradictory to our findings, increased SNAI1 mRNA expression or TGFB protein expression.