Clinical relevance of peroxisome proliferator-activated receptor-gamma expression in myxoid liposarcoma

BACKGROUND: Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated transcription factor that belongs to the nuclear hormone receptor superfamily. PPARγ is essential in adipocyte differentiation from precursor cells. Its antitumorigenic effects are reported in certain malignancies; however, its effects in liposarcoma are unclear. METHODS: We analyzed PPARγ expression using immunohistochemistry (IHC) in 46 patients with myxoid liposarcoma [MLS; median age, 47 years (range, 14–90 years) and mean follow-up period, 91 months (range, 13–358 months)]. PPARγ mRNA expression levels were measured by quantitative reverse transcription polymerase chain reaction. Further, we evaluated the correlation of PPARγ expression with clinical outcomes. RESULTS: We found that the metastasis-free survival rate was significantly higher in lower PPARγ expressers [34 patients with labeling index (LI) <50 %] than in higher expressers (12 patients with LI ≥50 %; p = 0.01). Cox multivariate analysis revealed that a higher PPARγ level was an independent predictor of metastasis (relative risk = 6.945, p = 0.026). Furthermore, using 28 fresh MLS specimens, we confirmed an increased PPARγ mRNA expression level in the higher LI group (p = 0.001). CONCLUSIONS: In this study, higher PPARγ expression in MLS was a risk factor associated with distant metastasis; therefore, it would be a novel prognostic marker for MLS. Further analyses will help to understand the correlation between PPARγ expression and tumor malignancy in liposarcoma.