Induction of apoptosis in HPV16 E7 transfected human keratinocyte by ALA-mediated photodynamic therapy

Area of Science:

• Photodynamic Therapy
• Cell Biology
• Oncology

Background:

• 5-Aminolevulinic acid (ALA)-mediated photodynamic therapy (ALA-PDT) is a recognized treatment for human papillomavirus (HPV)-associated conditions.
• The precise mechanisms by which PDT affects HPV-infected cells remain incompletely understood.
• This study investigates ALA-PDT's impact on apoptosis in a specific HPV-infected cell model.

Purpose of the Study:

• To investigate the induction of apoptosis by ALA-PDT in a human keratinocyte cell line engineered to express the high-risk HPV16 E7 gene.
• To explore the cellular and molecular responses, including mitochondrial damage and caspase activation, following ALA-PDT treatment.

Main Methods:

• Transfection of a human keratinocyte cell line with the HPV16 E7 gene.
• In vitro assessment of protoporphyrin IX (PpIX) generation upon ALA incubation.
• Evaluation of ALA-PDT-induced apoptosis, mitochondrial potential, and caspase activation at varying light doses.

Main Results:

• HPV16 E7-transfected cells efficiently generated PpIX when exposed to ALA.
• ALA-PDT treatment induced apoptosis in a dose-dependent manner (4-12 J/cm²).
• Mitochondrial potential collapse was observed early post-PDT, accompanied by caspase-3 activation, while caspase-9 activation was weaker.

Conclusions:

• Human keratinocytes expressing the HPV16 E7 gene effectively produce PpIX in the presence of ALA.
• ALA-PDT triggers apoptosis through a mitochondrial-dependent pathway in HPV16 E7-transfected cells.
• The findings elucidate a key mechanism of ALA-PDT in targeting HPV-infected cells.