Inhibition of autophagy enhances apoptosis induced by Ce6-photodynamic therapy in human colon cancer cells.

Abstract

OBJECTIVE:

To evaluate the therapeutic effect of Chlorin e6 photodynamic therapy (Ce6-PDT) in human colorectal cancer cells and investigate the role of autophagy in Ce6-PDT.

METHODS:

SW480 cells underwent Ce6-PDT with and without pretreatment with the autophagy inhibitor 3-methyladenine (3MA). Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was evaluated using an Annexin V assay, using a rhodamine 123 (RH123) assay to evaluate mitochondrial membrane potential (MMP), and by measuring Caspase-3 and Bcl-2 protein expression using western blotting. Autophagy was evaluated by directly visualizing acridine orange-stained acidic vesicular organelles (AVOs) using fluorescent microscopy and by measuring LC3Ⅰ/Ⅱand Atg5 expression using western blotting.

RESULTS:

Ce6-PDT decreased SW480 viability in a dose-dependent manner. Ce6-PDT induced apoptosis in SW480 cells via the mitochondrial apoptosis pathway as indicated by decreased mitochondrial membrane potential, increased Annexin V staining, and increased Caspase-3 expression. Ce6-PDT was also shown to induce autophagy as demonstrated by increased acridine-orange stained AVOs as well as increased expression of the autophagy-associated proteins Atg5. Inhibition of autophagy with 3MA potentiated SW480 cell response to Ce6-PDT and increased the rate of apoptosis in the treated cells.

CONCLUSIONS:

Ce6-PDT induces autophagy and apoptosis of SW480 cells in a dose-dependent manner. Inhibition of autophagy increases the apoptosis induced by Ce6-PDT. Modulation of autophagy may be a potential therapeutic target for colon cancer cells treated with Ce6-PDT.

• Authors: Mengyu Luo, Hongxia Li, Duhong Han, Kaizhen Yang, Ling Kang
• Journal: Photodiagnosis and photodynamic therapy (Photodiagnosis Photodyn Ther) Vol. 36 Pg. 102605 (Dec 2021) ISSN: 1873-1597 [Electronic] Netherlands
• PMID: 34715368 (Publication Type: Journal Article)
• Copyright: Copyright © 2021. Published by Elsevier B.V.

Chemical References

• Photosensitizing Agents
• Porphyrins

Topics

• Apoptosis
• Autophagy
• Cell Line, Tumor
• Colonic Neoplasms (drug therapy)
• Humans
• Photochemotherapy (methods)
• Photosensitizing Agents (pharmacology, therapeutic use)
• Porphyrins (pharmacology, therapeutic use)