The Effects of Photodynamic Therapy with Low-Level Diode Laser Compared with Doxorubicin on HT-29 Colorectal Adenocarcinoma Cells Viability.

Background and Objective: Colorectal adenocarcinoma is considered one of the major causes of cancer-related lethality among other type of malignancies. Given the several limitations and adverse outcomes of conventional therapeutic regimens against colorectal cancer, the focus of many investigations has been attributed to the introduction of a novel combined regimen with harmless agents. The purpose of the present study was to investigate the effect of combined doxorubicin (DOX) treatment and photodynamic therapy (PDT) on colorectal adenocarcinoma cells. Material and Methods: HT-29 cells were exposed to different concentrations of DOX, low-level (630 nm) diode laser, and methylene blue (MB) as a photosensitizer substrate separately and a combination of them. The cytotoxic effect of the DOX, laser, MB, and their combination and the IC50 value for each treatment group were calculated by 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT). The malondialdehyde (MDA) content as a biomarker of the lipid peroxidation process and liberated lactate dehydrogenase (LDH) enzyme into supernatant was determined. Results: The results of our study evidenced that a combination of photodynamic light (laser plus MB) and DOX caused a significant reduction in the percentage of HT-29 viable cells compared with control and other treatment groups. In addition, this mentioned combination led to a considerable decrease in IC50 of DOX. Increased cell membrane lipid peroxidation and cell destruction processes in the combination therapy group were proven through significant elevation of MDA content and LDH activity in the medium, respectively. Conclusion: The findings of the present study suggested that DOX combined with PDT had a better therapeutic impact on HT-29 colorectal adenocarcinoma cells. Hence, the simultaneous application of PDT along with antineoplastic drugs improves the chemosensitivity of cancerous cells via the disruption of their membrane and triggering death processes that lead to the decrease of chemotherapeutic agents required doses and undesirable effects.