CDCA7 promotes chemoresistance of drug-tolerant persister cells in breast cancer by upregulating the expression of autophagy-related protein genes.

[BACKGROUND] Chemotherapy resistance is the main obstacle to breast cancer recurrence, metastasis, and mortality. Drug-tolerant persister (DTP) cells are a novel type of target cell associated with tumor resistance, and autophagy is a key factor in maintaining the survival of tumor DTP cells. However, it is unclear whether the activation of autophagy in breast cancer DTP cells is related to their overexpression of the transcriptional regulatory factor CDCA7.

[METHODS] We analyzed CDCA7 expression using public datasets and clinical samples and established breast cancer cell lines with CDCA7 overexpression and knockdown to assess the role of CDCA7 in breast cancer. Autophagy was assessed via electron microscopy, mRFP-GFP-LC3 imaging, and immunoblotting. Mechanistic studies employed ChIP-seq, dual-luciferase assays, and site-directed mutagenesis. Functional assays measured chemosensitivity (CCK-8), migration/invasion (scratch/Transwell), and tumorigenicity (mouse xenograft).

[RESULTS] CDCA7 was significantly upregulated in breast cancer DTP cells. Overexpression of CDCA7 in breast cancer cells significantly enhanced autophagy-related biological processes and molecular functions. Through ChIP-seq and targeted knockout experiments, we identified the binding sites of CDCA7 on the autophagy-related protein genes , , and . Using transmission electron microscopy and mRFP/mCherry-GFP-LC3B tandem fluorescent tagging, we observed that knockdown significantly reduced the number of autolysosomes in breast cancer DTP cells and markedly inhibited autophagic flux. Moreover, knockdown not only decreased drug resistance in breast cancer cells but also reduced metastasis, invasion, and tumorigenic ability , ultimately prolonging the survival of tumor-bearing mice.

[CONCLUSION] CDCA7 drives breast cancer chemoresistance by transcriptionally activating a pro-survival autophagy program in DTP cells, nominating it as a promising therapeutic target.