Cetylpyridinium chloride inhibits the polarization of tumor-associated macrophages and the proliferation of triple-negative breast cancer cells.

[OBJECTIVES] Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. Due to its radiotherapy resistance, high metastasis rate and recurrence rate, the prognosis is poor. So far, effective therapeutic drugs for it remain elusive. Cetylpyridinium chloride (CPC) has initially demonstrated anti-tumor properties in various tumors. Therefore, the aim of this study is to explore the intervention effect of CPC on macrophages in the tumor microenvironment (TME) and its therapeutic effect on TNBC.

[METHODS] The effects of CPC on macrophage polarization and expression changes were evaluated by WB and RT-qPCR. Multiple TNBC cell lines and non-cancer cells were exposed to CPC under different conditions (concentration and duration), and cell survival and proliferation were assessed by CCK8 and colony formation. The effects of CPC on apoptosis, migration and invasion of TNBC cells were further evaluated. The mitochondrial status was assessed by Mito-Tracker Red CMXRos staining, mitochondrial protein expression detection and ATP content detection to explain the cause of apoptosis. The effect of CPC on TNBC growth was further confirmed in animal models.

[RESULTS] Our results demonstrated that CPC (2 μM) inhibited the M2 polarization of macrophages induced by interleukin-4 (IL-4) and tumor secretions, and reduced their characteristic secretions that promote tumor growth. Meanwhile, CPC significantly suppressed the proliferation of multiple TNBC cell lines, induced mitochondrial damage, significantly decreased cellular ATP levels, and ultimately led to tumor cell apoptosis. Moreover, TNBC cells are more sensitive to CPC than non-tumor cells. Additionally, CPC significantly inhibited the migration and invasion of TNBC cells. Finally, we confirmed the growth inhibitory effect of CPC on TNBC in vivo.

[CONCLUSION] CPC has dual effects: it inhibits the M2 polarization of tumor-associated macrophages (TAMs) and directly suppresses the proliferation and invasion of TNBC cells, ultimately effectively inhibiting the growth of TNBC in vivo. Considering that CPC has been administered in humans as a safe drug-disinfectant for decades, our study here provides a molecular basis for the application of CPC as a potential option to clinical treatments of TNBC.