Triggering apoptosis by oroxylin A through caspase-8 activation and p62/SQSTM1 proteolysis

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Oroxylin A demonstrates potential antitumor properties by inducing apoptosis.
• The precise molecular pathways underlying oroxylin A's apoptotic effects remain unclear.
• Understanding these mechanisms is vital for developing novel cancer therapeutics.

Purpose of the Study:

• To elucidate the molecular mechanisms by which oroxylin A induces apoptosis in hepatocellular carcinoma cells.
• To investigate the role of p62/SQSTM1 and caspase-8 in oroxylin A-mediated cell death.
• To explore the downstream effects of p62/SQSTM1 cleavage on cellular processes.

Main Methods:

• Investigated oroxylin A-induced apoptosis in hepatocellular carcinoma cells.
• Utilized p62/SQSTM1 and caspase-8 activation assays.
• Performed site-directed mutagenesis on p62/SQSTM1 (D329H, D329G) to assess cleavage resistance.
• Assessed Nrf2 stability, oxidative stress, and reactive oxygen species (ROS) levels.
• Evaluated in vivo antitumor effects using a xenograft mouse model.

Main Results:

• Oroxylin A-induced apoptosis is dependent on p62/SQSTM1-mediated caspase-8 activation.
• Oroxylin A triggers caspase-8-dependent proteolysis of p62/SQSTM1 at Asp329.
• Mutations at Asp329 of p62/SQSTM1 confer resistance to oroxylin A-induced cleavage and apoptosis.
• Cleaved p62/SQSTM1 leads to reduced Nrf2 stability, increased oxidative stress, and elevated ROS levels.
• p62/SQSTM1 plays a significant role in oroxylin A's antitumor activity in vivo.

Conclusions:

• Oroxylin A effectively triggers apoptosis in hepatocellular carcinoma cells via caspase-8 activation and p62/SQSTM1 proteolysis.
• The cleavage of p62/SQSTM1 is a critical step in the apoptotic pathway induced by oroxylin A.
• These findings reveal a novel mechanism for oroxylin A's antitumor effects, highlighting p62/SQSTM1 as a key mediator.