Photodynamic therapy with 9-hydroxypheophorbide alpha on AMC-HN-3 human head and neck cancer cells: induction of apoptosis via photoactivation of mitochondria and endoplasmic reticulum.

Abstract

Skin phototoxicity is one of the main side effects of photodynamic therapy (PDT). To overcome this problem, some new photosensitizers have been developed with longer absorbance wavelengths and shorter half-life in the body. In this study, we investigated the mechanism of PDT mediated by a new chlorophyll derivative photosensitizer, 9-hydroxypheophorbide alpha (9-HPbD), on AMC-HN-3 cancer cells. Phototoxicity and apoptosis on AMC-HN-3 cells induced by 9-HPbD was exhibited in a time- and dose-dependent manner. Mitochondria and endoplasmic reticulum (ER) were observed as preferential sites of 9-HPbD accumulation. Photoactivation of 9-HPbD-loaded AMC-HN-3 cells led to a rapid generation of reactive oxygen species (ROS) at 30 min, followed by a loss of mitochondrial membrane potential (MMP) at 2 h, translocation of apoptosis-inducing factor (AIF) at 2 h, and the release of cytochrome c at 3 h following PDT. Caspase-12, an important caspase involved in ER-induced apoptosis, and C/EBP homologous protein (CHOP), an ER stress inducible transcription factor, were also upregulated after PDT (3-12 h and 6-12 h, respectively). Subsequently, activation of caspase-9 at 6 h, caspase-3 and PARP at 12 h also occurred in PDT-treated AMC-HN-3 cells. The above observations demonstrate that both mitochondria and ER serve not only as the sites of sensitizer binding, but also the subcellular targets of 9-HPbD-PDT, effective activation of which is responsible for 9-HPbD PDT-induced apoptosis in AMC-HN-3 cells.

• Authors: Phil-Sang Chung, Peijie He, Jang-In Shin, Hee-Jun Hwang, Sang Joon Lee, Jin-Chul Ahn
• Journal: Cancer biology & therapy (Cancer Biol Ther) Vol. 8 Issue 14 Pg. 1343-51 (Jul 2009) ISSN: 1555-8576 [Electronic] United States
• PMID: 19421004 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• 9-hydroxypheophorbide alpha
• Neoplasm Proteins
• Radiation-Sensitizing Agents
• Reactive Oxygen Species
• Chlorophyll

Topics

• Apoptosis (drug effects, radiation effects)
• Carcinoma, Squamous Cell (pathology)
• Cell Line, Tumor (drug effects)
• Chlorophyll (analogs & derivatives, pharmacology, radiation effects)
• Drug Screening Assays, Antitumor
• Endoplasmic Reticulum (drug effects, radiation effects)
• Enzyme Activation (drug effects)
• Head and Neck Neoplasms (pathology)
• Humans
• Lasers
• Lipid Peroxidation (drug effects)
• Mitochondria (drug effects, radiation effects)
• Neoplasm Proteins (metabolism)
• Oxidative Stress (drug effects, radiation effects)
• Photochemotherapy
• Protein Transport (drug effects)
• Radiation-Sensitizing Agents (pharmacology, radiation effects)
• Reactive Oxygen Species (metabolism)