Methylene Blue-Mediated Photodynamic Therapy in Combination With Doxorubicin: A Novel Approach in the Treatment of HT-29 Colon Cancer Cells

<b>Introduction:</b> With an alarmingly growing number of patients diagnosed with colorectal cancer, adopting innovative anti-cancer approaches has recently garnered great attention. One interesting concept is the co-administration of cytotoxic agents and safer modalities such as photodynamic therapy (PDT), which can subsequently improve therapeutic efficacy and potentially reduce the risks of severe adverse effects and drug resistance. In the course of PDT, a locally injected photosensitizer (PS) is irradiated with a light source, which subsequently generates reactive oxygen species (ROS) and induces programmed cell death in tumor cells. <b>Methods:</b> In this study, to evaluate the potential anti-cancer effects of chemotherapy combined with PDT, in comparison to each alone, we employed PDT, comprising methylene blue (MB) and diode lasers at 630 and 810 nm wavelengths, in conjunction with the chemotherapeutic agent doxorubicin (DOX). <b>Results:</b> The MTT assay showed that the viability of colorectal cancer HT-29 cells decreased significantly following DOX+PDT treatment. Similarly, lactate dehydrogenase (LDH) release and lipid peroxidation rates were substantially higher in DOX+PDT treatment groups. Lastly, the catalase (CAT) assay indicated that the combination reduced the ability of CAT in the detoxification of H₂ O₂. <b>Conclusion:</b> Our study suggests that MB-mediated PDT combined with chemotherapy might provide a promising avenue to improve therapeutic efficacy and potentially reduce the risk of adverse effects and drug resistance. Without a doubt, further investigations need to delve into the pharmacological advantages and disadvantages of PTD-based combination therapy and optimize its administered doses along with other modalities.