Synergistic effect of photodynamic treatment and doxorubicin on triple negative breast cancer cells

Breast cancer is a metastatic cancer that can spread to other organs, such as the bone, liver, and brain. There are many treatments for breast cancer, such as surgery and chemotherapy, but they lead to resistance and side effects. Therefore, the discovery of new therapies with high efficacy and low toxicity that selectively affect cancer cells is of great importance. Of late, the combination therapy has been suggested as a novel approach compared to existing treatments. In the present study, the effect of the combined treatment of doxorubicin (DOX) and methylene blue activated in the presence of laser irradiation (PDT) on triple-negative breast cancer cells has been investigated. Human breast cancer cell line MDA-MB-231 was exposed to different concentrations of DOX, methylene blue (MB) and DOX-methylene blue (MB-DOX) combination therapy in two different conditions: first the treatment with DOX and then with MB-PDT, and another treatment first with MB-PDT and then with DOX. Cell viability was evaluated using the MTT assay. Morphological and colonization changes were observed by light microscopy. The occurrence of apoptotic cell death was assessed by double-staining ethidium bromide-acridine orange using fluorescence microscopy and flow cytometry. The results showed that the combination of using MB-PDT, followed by DOX (even at low concentrations), has a better effect on inducing cancer cell death in comparison to DOX alone. The result of this study suggests that the combination therapy of MB-PDT-DOX can be used as a potential strategy for the treatment of triple-negative breast cancer cells.