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

  • Photodiagnosis Photodyn Ther. 2021 Dec;36:102605. doi: 10.1016/j.pdpdt.2021.102605.
Mengyu Luo  1 ,  Hongxia Li  1 ,  Duhong Han  1 ,  Kaizhen Yang  2 ,  Ling Kang  3
Affiliations
  • 1. College of Public Health, Xinjiang Medical University, No 567, SHangde North Road, SHuimogou District, Urumqi, Xinjiang, China.
  • 2. The First People's Hospital of Urumqi, Urumqi, Xinjiang, China.
  • 3. College of Public Health, Xinjiang Medical University, No 567, SHangde North Road, SHuimogou District, Urumqi, Xinjiang, China. Electronic address: [email protected].
PMID: 34715368 DOI: 10.1016/j.pdpdt.2021.102605
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.

Keywords
Apoptosis; Autophagy; Chlorin E6; Colorectal cancer; Photodynamic therapy.
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