Enhanced bioluminescence imaging of tumor cells surviving chemotherapy in a murine model of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is associated with poor prognosis and high recurrence, driven by residual tumor cells that survive chemotherapy. To monitor therapy response in vivo, we established a clinically relevant TAC regimen (docetaxel, doxorubicin, cyclophosphamide) in mice bearing mammary tumors derived from K14cre;Brca1^F/F;Trp53^F/F (KB1P) organoids expressing an mCherry-AkaLuc dual reporter (mCA-KB1P). AkaLuc bioluminescence imaging (AkaBLI) enabled non-invasive detection of minimal residual disease (MRD) with a sensitivity of approximately 1000 cells. As AkaLuc elicited an immune response, we generated Histon2B-mCherry-expressing KB1P organoids (HmC-KB1P) to study tumor cell survival in immunocompetent hosts. Flow cytometry and histological analysis revealed that MRD in immunocompetent mice is characterized by few residual cells with transient loss of epithelial markers, in contrast to immunodeficient hosts, which retains more epithelial-like cells. These findings validate AkaBLI for sensitive MRD detection and highlight the immune system's critical role in modulating residual tumor cell fate following chemotherapy.