Significance of LRP and PPAR-γ Expression in Lipomatous Soft Tissue Tumors

BACKGROUND Molecular mechanism of differentiation in lipogenic tumor is still unknown in detail. Low-density lipoprotein receptor-related protein (LRP) and peroxisome proliferator-activated receptor gamma (PPAR-gamma), representative regulatory molecules of lipogenic differentiation, have been reported today as multi-functional molecules and to modulate tumorigenesis in various kind of cancer. To date, diagnostic and therapeutic significance of the expression of these molecules in lipogenic tumors are not defined. METHODS The immunohistochemical expression status of LRP and PPAR-gamma in various grades of 54 lipogenic tumors was analyzed. Correlation between the expression levels and the differentiation of the tumors was confirmed. For statistical analyses, the Kruskal-Wallis test, the Steel-Dwass test and the Mann-Whitney U test were used. RESULTS LRP and PPAR-gamma expression was detected in 50 (92.6%) and 44 (81.5%) cases, respectively. The expression level in LRP was significantly higher in cases with well differentiated liposarcoma, pleomorphic liposarcoma and dedifferentiated liposarcoma than in lipoma. Compared with lipoma or well differentiated liposarcoma, significant elevation in expression level of PPAR-gamma was confirmed in myxoid liposarcoma, pleomorphic liposarcoma, dedifferentiated liposarcoma and the differentiated area of dedifferentiated liposarcoma. CONCLUSION The up-regulation of LRP and PPAR-gamma in higher grade cases, i.e. less differentiated tumors than in low grade cases was shown, suggesting the candidate role of these molecules as tumor progression modulators rather than regulatory molecules of differentiation in lipogenic tumors.