Breast cancer stem cells (BCSCs) have been implicated as the root of tumorinitiation, therapeutic resistance, relapse, and metastasis due to their uniqueabilities of self-renew, differentiation potentials and resistance to mostconventional therapies.Signaling pathways of stemness markers, Notch-1, ALDH1 andmicroRNAs, a class of emerging small non-coding RNAs, are importantregulators of BCSC functions and self-renewal capacity by modulatingmultiple biological processes via the post-transcriptional regulation of geneexpression and cellular signaling pathways. Understanding the earlymolecular mechanisms and identifying the miRNAs that are involved inchemo-resistance, and their crosstalk with Notch-1 and ALDH1, could be apotential therapeutic option for breast cancer drug resistant.Previously, we showed that Trigonella foenum (Fenugreek) extract (FCE),a traditional herbal plant, has an anti-tumor activity against HepG2 cell line.In the present study, we evaluated and screened a panel of aberrant expressedmiRNAs (i.e. miR-142, let-7a, let-7b and miR-34a) that might have a crosstalkwith Notch-1 and ALDH1 in isolated (CD44+/CD24−/ALDH1+)subpopulation treated with or without FCE extract alone or in combinationwith Doxorubicin for different time intervals.Our results revealed that FCE treatment alone for 48 h showed a significantdecrease in cell viability, clonogenicity and invasion capacity of(CD44+/CD24−/ALDH1+) BCSCs subpopulation compared to untreatedcells. Furthermore, FCE-inhibited Notch-1 and ALDH1 expression that wasassociated with a significant decrease in miR-142 by 4.6-folds and an increasein expression levels of let-7a, let-7b and miR-34a by 4.5, 7.7 and 15.4 foldsrespectively. Moreover, ectopic miR-34a expression significantly reduce cellproliferation and increase apoptotic induction consistent with downregulationof Notch-1 and ALDH1 expression in treated cells extract alone or incombination with Doxorubicin for 24h, suggesting that miR-34a expressionmight play a role in the breast cancer potential.Furthermore, FCE treated (CD44+/CD24−/ALDH1+) subpopulationectopically expressing miR-34a showed an increase in chemosensitivity todoxorubicin at low doses after 24 h compared to the controls. In initiated(CD44+/CD24−/ALDH1+) BCSC tumor xenografts ectopically expressingmiR-34a, FCE/Doxorubicin combined treatment showed a significant regression in tumor size by 62% after 72h compared to untreated controls orDoxorubicin alone.All in all, the aberrant expression of selected miRNAs, such as of miR-34a, might regulate a crosstalk with stemness characteristic markers, Notch-1and ALDH1, that are involved in the pathogenesis of breast cancer.

Citation Format: Rana H. Ateya, Ahmed S. Sultan. Trigonella foenum (fenugreek) extract and ectopic miR-34a inhibit stemness characteristics and enhance sensitivity of (CD44+/CD24−/ALDH1+) breast cancer stem cells subpopulation to doxorubicin by targeting notch1/ALDH1signaling pathways [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS19-26.