Intratumoral bacteria, especially Gram-positive bacteria (G⁺), have a unique bacterial niche in breast cancer that promoted tumor progression. However, the effects of G⁺ have so far been overlooked, serving an “invisible driver” of breast cancer. Moreover, due to the altered biological structure of G⁺ in tumor cells and the penetration barrier of antibiotics, the effect of antibiotic-mediated eradication of G⁺ in tumors is limited. Here, to simultaneously inhibit intratumoral G⁺ and tumor cells via ferroptosis therapy, an amorphous nano-assembly (DFTV) was constructed by assembling doxorubicin (DOX), tannic acid (TA), FeSO₄, and vancomycin (Van). DFTV treatment effectively targets intratumoral G⁺, thereby inhibiting the growth of the breast tumor and postoperative recurrence by downregulating the expression of inflammatory cytokines, including interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-alpha (TNF-α). Moreover, inhibiting intracellular G⁺ also restrains the reorganization of F-actin to form pseudopodia, thereby impairing tumor cell motility and blocking metastasis. Collectively, DFTV improves the antitumor efficacy by targeting G⁺ in breast tumors, offering novel insights into overcoming the limitations associated with the lack of intratumoral antibacterial therapy in clinical breast cancer treatment protocols.

Intracellular bacteria  /  Breast cancer  /  Ferroptosis therapy  /  Phototherapy  /  Intracellular biological oxidation-reduction cascade reaction  /  F-actin  /  Pseudopodia  /  Inflammatory factors