Conclusion
PPARγ improves pemetrexed therapeutic efficacy in non-squamous NSCLC. The cytotoxicity effect of PMX can be synergized by activating PPARγ and thereby inhibiting NF-κB pathway.
Methods
PMX effect was evaluated in a urethane-induced lung adenocarcinoma mouse model. The interaction between PMX and intracellular proteins, particularly peroxisome proliferator-activated receptor γ (PPARγ), was investigated. The role of PPARγ in mediating pemetrexed cytotoxicity was investigated using NSCLC cell lines, mouse models and clinical specimens.
Objective
The folic acid analog pemetrexed (PMX) is recommended for the first-line chemotherapy for advanced non-squamous non-small cell lung cancer (NSCLC). However, the mechanisms underlying PMX cytotoxicity in NSCLC remain to be fully explored.
Results
This study found that PPARγ expression was correlated with prolonged progression-free survival in NSCLC patients. PPARγ downregulated hypoxanthine-guanine phosphoribosyl transferase (HGPRT), a key enzyme for nucleotide salvage synthesis, thereby sensitizing cells to PMX inhibition on nucleotide de novo synthesis. PMX was also a candidate partial agonist of PPARγ, and PMX-activated PPARγ bound to NF-κB and transcriptionally suppressed the NF-κB target gene, c-Myc. PMX inhibited tumor growth by activating PPARγ in a urethane-induced lung cancer model characterized by elevated NF-κB activity.