A juglone derivative that disrupts mitochondrial redox metabolism, inhibiting the breast fibroblast-cancer cell pro-migratory signaling induced by doxorubicin.

Doxorubicin (Doxo) is a DNA-damaging chemotherapeutic widely used in breast cancer (BC) treatment. While effective at inhibiting tumor cell proliferation, Doxo paradoxically enhances pro-inflammatory signaling between stromal and BC cells and promotes pro-migratory and invasive phenotypes. Identifying strategies to counteract these adverse effects remains a relevant therapeutic challenge. In this study, we synthesized a series of juglone (5-hydroxy-1,4-naphthoquinone) derivatives and evaluated their effects on mitochondrial bioenergetics and NAD(P)H Quinone Dehydrogenase 1 (NQO1)-dependent viability in BC cell lines (ZR75-1, MCF7, and MDA-MB-231) and RMF621 fibroblasts. Among these compounds, J2 (Cpd. J2) emerged as a selective inhibitor of proliferation, inducing S-phase cell cycle arrest and suppressing clonogenic capacity. In ZR75-1 and MCF7 cells, Cpd. J2 increased mitochondrial NADH levels. This effect was abolished by inhibitors of mitochondrial complex I, transaminases, and α-ketoglutarate/pyruvate dehydrogenases, indicating activation of the tricarboxylic acid cycle. Consistently, Cpd. J2 enhanced mitochondrial oxygen consumption rate and superoxide production. These metabolic effects were absent in MCF7 ρ0 cells, demonstrating a strict dependence on functional mitochondria. Moreover, Cpd. J2 significantly reduced Doxo-induced CCL2 secretion in RMF621 fibroblasts and inhibited the motility of low-migratory BC cells stimulated with conditioned medium from Doxo-treated fibroblasts. Mechanistically, Cpd. J2 decreased the Doxo-induced metabolic remodeling and increase in mct4, but not glut1, in RMF621 cells, and attenuated the upregulation of ccr2 and snail in MCF7 cells. Collectively, these data indicate that Cpd. J2 modulates mitochondrial redox balance via NQO1, inhibiting BC cell proliferation and disrupting Doxo-driven pro-migratory stromal-tumor signaling.