Thymoquinone Anticancer Effects Through the Upregulation of NRF2 and the Downregulation of PD-L1 in MDA-MB-231 Triple-Negative Breast Cancer Cells.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with a metastatic nature. TNBC lacks the expression of the progesterone receptor, estrogen receptor, and human epidermal growth factor receptor 2. The absence of these three receptors limits the therapy options. Meanwhile, conventional medication is not very effective in the treatment and prevention of TNBC. Developing innovative therapeutic agents from natural bioactive compounds is a viable option. In the current study, the natural compound thymoquinone (TQ) was used in MDA-MB-231 TNBC cells. A dose response to TQ (0-50 µM) was obtained following a 24-hour exposure. An Annexin V-FITC apoptosis detection was used to study the apoptotic effect of TQ.  With increasing TQ concentrations from 0-20 µM, flow cytometer examination revealed an increase in apoptotic cells. Nearly 80% of the cells studied were in the apoptotic phase at 20 µM. (early and late apoptosis). Meanwhile, at 30 µM, there was a significant drop in apoptotic cells, which may be interpreted as an increase in necrotic cells. Molecular-targeted therapy is a new approach in treating cancer. The effect of TQ on the expression of Nrf2(Nuclear factor erythroid 2- related factor 2) and PD-L1 (Programmed death-ligand 1) was investigated using a specific primary antibody against these proteins. A Western blot analysis confirmed TQ's ability to change the expression of both proteins under investigation. According to normalized data, TQ had the ability to elicit more than 2-fold increase in Nrf2 expression in IFN-γ stimulated MDA-MB-231 cells. In contrast, co-treated cells (IFN-γ + TQ) showed a 65 percent reduction in PD-L1 expression. In conclusion, TQ was suggested as a promising anticancer option for treating  TNBC.