Enhancing chemosensitivity of wild-type and drug-resistant MDA-MB-231 triple-negative breast cancer cell line to doxorubicin by silencing of STAT 3, Notch-1, and β-catenin genes

Background/objective The absence of receptors in triple-negative breast cancer limits therapeutic choices utilized in clinical management of the disease. Doxorubicin is an important member of therapeutic regimens that is hindered by emergence of resistance. The current work aim to investigate of therapeutic potential of single and combinations of siRNA molecules designed for silencing STAT 3, Notch-1, and beta-catenin genes in wild type and doxorubicin resistant MDA-MB-231 triple negative breast cancer cell line. Methods Doxorubicin resistant MDA-MB-231 cell line was developed and characterized for the expression of multidrug resistance-related genes, CD44/CD24 markers, inflammatory cytokines, and the expression of STAT 3, Notch-1, and beta-catenin targeted genes. Further, the effect of single and combinations of siRNA on cell viability and chemosensitivity of both wild type MDA-MB-231 cells (MDA-MB-231/WT) and doxorubicin resistant MDA-MB-231 cells (MDA-MB-231/DR250) were assessed by MTT assay. Results The IC50 of doxorubicin was 10-folds higher in MDA-MB-231/DR250 resistant cells compared to MDA-MB-231/WT control cells, 1.53 +/- 0.24 mu M compared to 0.16 +/- 0.02 mu M, respectively. The expression of targeted genes was higher in resistant cells compared to control cells, 3.6 +/- 0.16 folds increase in beta-catenin, 2.7 +/- 0.09 folds increase in Notch-1, and 1.8 +/- 0.09 folds increase in STAT-3. Following treatment with siRNAs, there was a variable reduction in mRNA expression of each of the targeted genes compared to scrambled siRNA and a reduction in IC50 in both cell lines. The effect of a combination of three genes produced the largest reduction in IC50 in resistant cell line. Conclusion Our study showed that the silencing of single and multiple genes involved in drug resistance and tumor progression by siRNA can enhance the chemosensitivity of cancer cells to conventional chemotherapy.