Organic cation transporter 3 mediates cisplatin and copper cross-resistance in hepatoma cells

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• Platinum-based drugs are crucial for treating solid tumors but face challenges from drug resistance and toxicity.
• Drug transporters significantly influence platinum drug efficacy and resistance.
• The role of copper transporter ATP7B in cisplatin resistance was investigated, as it's often overexpressed in resistant cells.

Purpose of the Study:

• To investigate the mechanisms of cisplatin resistance, particularly in the absence of the copper transporter ATP7B.
• To identify key transporters involved in cisplatin accumulation and resistance in hepatoma cells.
• To explore the potential of organic cation transporter 3 (OCT3) as a therapeutic target.

Main Methods:

• Hepatoma cell lines were used to assess cisplatin sensitivity, apoptosis, drug accumulation, and transporter gene expression.
• Gene knockout and overexpression techniques were employed for the copper transporter ATP7B.
• Levels of organic cation transporter 3 (OCT3) and metallothionein 1 (MT1) were analyzed in resistant cell lines.

Main Results:

• Overexpression or knockout of copper transporter ATP7B did not impact cisplatin sensitivity.
• Cisplatin-resistant cells exhibited reduced cisplatin accumulation and downregulation of OCT3.
• Overexpression of OCT3 reversed cisplatin resistance, and its downregulation was linked to cross-resistance to copper.

Conclusions:

• Decreased OCT3 expression is a key factor in developing resistance to cisplatin and copper.
• OCT3 represents a potential novel therapeutic target for enhancing anticancer strategies, including for hepatocellular carcinoma (HCC).
• Targeting OCT3 could offer a new approach to overcome platinum drug resistance.