Troglitazone suppresses glutamine metabolism through a PPAR-independent mechanism

Area of Science:

• Oncology
• Cancer Metabolism

Background:

• Enhanced glutamine metabolism fuels tumor cell growth and survival.
• Targeting glutaminolysis is a promising anti-cancer strategy.
• Troglitazone, a PPARγ agonist, has demonstrated anti-tumor activity and affects glutamine metabolism.

Purpose of the Study:

• To investigate if troglitazone disrupts glutamine metabolism in tumor cells.
• To determine if troglitazone's anti-cancer effects are dependent on PPARγ activity.
• To explore the potential of repurposing troglitazone for cancer therapy.

Main Methods:

• Assessed troglitazone's impact on glutamine uptake, ASCT2 and glutaminase expression.
• Measured 13C-glutamine incorporation into the TCA cycle and ATP levels.
• Evaluated troglitazone's effects on cell growth, c-Myc levels, and ROS production.
• Investigated the role of PPARγ, proteasomal degradation, and combinatorial treatments with metformin and α-ketoglutarate.

Main Results:

• Troglitazone suppressed glutamine uptake, ASCT2 and glutaminase expression, and TCA cycle incorporation.
• Treatment led to decreased ATP, increased ROS, and reduced tumor cell growth.
• Troglitazone's effects were independent of PPARγ activity.
• Troglitazone decreased c-Myc levels, an effect reversed by MG132, which also rescued glutamine uptake and cell number.
• Combination therapy with metformin showed synergistic anti-proliferative effects.

Conclusions:

• Troglitazone effectively disrupts cancer cell glutamine metabolism and proliferation through PPARγ-independent mechanisms.
• The drug's action involves downregulating c-Myc and potentially proteasomal pathways.
• Troglitazone, particularly in combination with metformin, represents a viable repurposed therapeutic strategy for cancer treatment.