Triple-negative breast cancer (TNBC) is a very aggressive subtype of breast cancer characterized by drug resistance and distant metastasis. Cancer stem cells (CSCs) are considered a major contributor to TNBC's drug resistance. Thus targeting and eliminating CSCs have been vigorously researched. However, the precise targetable molecular networks responsible for CSC genesis remain unclear; this conundrum is mainly due to the high heterogeneity of the TNBC tumor microenvironment (TME). The cancer-associated fibroblasts (CAFs) are one of the most abundant cellular components of the TME. Emerging studies indicate that CAFs facilitate TNBC's progression by establishing a pro-tumor TME. Hence, identifying the molecular networks involved in CAF transformation and CAF-associated oncogenesis are essential areas to be explored. Through a bioinformatics approach, we identified INFG/STAT1/NOTCH3 as a molecular link between CSCs and CAF. DOX-resistant TNBC cell lines showed increased expression of INFG/STAT1/NOTCH3 and CD44 and were associated with increased self-renewal ability and CAF-transformative ability. Downregulation of STAT1 significantly reduced the tumorigenic properties of MDA-MB-231 and -468 cells and their CAF-transforming potential. Our molecular docking analysis suggested that gamma mangostin (gMG), a xanthone, formed complexes with INFG/STAT1/NOTCH3 better than celecoxib. We then demonstrated that gMG treatment reduced the tumorigenic properties similarly observed in STAT1-knocked down conditions. Finally, we utilized a DOX-resistant TNBC tumoroid-bearing mouse model to demonstrate that gMG treatment significantly delayed tumor growth, reduced CAF generation, and improved DOX sensitivity. Further investigations are warranted for clinical translation.
Keywords: Cancer stem cells (CSCs); Cancer-associated fibroblasts (CAFs); Gamma mangostin (gMG); IFNG/STAT1/NOTCH signaling; Triple-negative breast cancer (TNBC).
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