Tumor stromal topography promotes chemoresistance in migrating breast cancer cell clusters.

Multicellular clustering provides cancer cells with survival advantages and facilitates metastasis. At the tumor migration front, cancer cell clusters are surrounded by an aligned stromal topography. It remains unknown whether aligned stromal topography regulates the resistance of migrating cancer cell clusters to therapeutics. Using a hybrid nanopatterned model to characterize breast cancer cell clusters at the migration front with aligned stromal topography, we demonstrate that topography-induced migrating cancer cell clusters exhibit upregulated cytochrome P450 family 1 (CYP1) drug metabolism and downregulated glycolysis gene signatures, which correlates with unfavorable prognosis. Screening on approved oncology drugs shows that cancer cell clusters on aligned stromal topography are more resistant to diverse chemotherapeutics. Full-dose drug testings further indicate that topography induces drug resistance of hormone receptor-positive breast cancer cell clusters to doxorubicin and tamoxifen and triple-negative breast cancer cell clusters to doxorubicin by activating the aryl hydrocarbon receptor (AhR)/CYP1 pathways. Inhibiting the AhR/CYP1 pathway restores reactive oxygen species-mediated drug sensitivity to migrating cancer cell clusters, suggesting a plausible therapeutic direction for preventing metastatic recurrence.