Quantitative Analysis of Carboxypeptidase M mRNA Expression in Lipomas and Liposarcomas
MR Erickson-Johnson, AR Seys, CW Roth, X Wang, YW Asmann, H Zhang, RV Lloyd, AL Folpe, AM Oliveira. Mayo Clinic, Rochester, MN
Background: Well-differentiated liposarcomas/atypical lipomatous tumors (WDL/ALT) are cytogenetically characterized by ring and giant rod chromosomes. These abnormal chromosomes contain several amplified genes including MDM2, CPM, CDK4, TSPAN31, and others. As part of a large genomic study of lipomatous neoplasms, we initially found Carboxypeptidase M (CPM) to be consistently amplified in well-differentiated liposarcoma/atypical lipomatous tumors but not in lipomas (Modern Pathol 2009). In this study we evaluated and compared CPM mRNA expression levels in these groups of tumors.
Design: Relative quantification of MDM2 and CPM were performed by quantitative real-time PCR (qPCR) in 9 WDL/ALT, 3 dedifferentiated (DD) liposarcomas, 1 pleomorphic sarcoma, 2 lipomas, and 2 normal adipose tissues. All analyses were performed in triplicate using UPL probes and a Light Cycler® 480 System (Roche, Mannheim Germany). Based on PCR efficiencies for both CPM and MDM2, using LC 480 1.5 software, relative differences between genes were determined using a standard curve generated from samples with perfect PCR efficiency. Concentrations of each sample were calculated from Cp values, and concentration of the target genes were divided by the concentration of the reference gene (PGK), thus providing the ratio. Fold induction of transcription of MDM2 and CPM were estimated by comparing to the values of PGK. Comparative and correlative expression analyses were performed using non-parametric methods.
Results: qRT-PCR showed that CPM mRNA expression levels were higher in WDL/ALT and DD liposarcomas (CPM medians 5.55 and 6.41, respectively) than in lipomas or normal fat (CPM medians 1.26 and 2.11, respectively) (p=0.005). Similar results were found with MDM2 mRNA for WDL/ALT and DD liposarcomas (MDM2 medians 8.32 and 24.47, respectively) and lipomas or normal fat (MDM2 medians 1.23 and 1.16, respectively) (p=0.001). CPM and MDM2 mRNA expression levels in pleomorphic liposarcoma were low (1.01 and 0.11, respectively). CPM mRNA expression levels were moderately correlated with MDM2 mRNA expression (r=0.61; p=0.007).
Conclusions: Similar to MDM2, CPM is transcriptionally upregulated in WDL/ALT and DD liposarcoma but not in lipomas, normal adipose tissue, and in a single example of pleomorphic liposarcoma. These results suggest a functional role of CPM in the biology of WDL/ALT and DD liposarcoma and further validate its value as a novel biomarker for the diagnosis of these tumors.
Category: Bone & Soft Tissue
Monday, March 22, 2010 1:00 PM
Poster Session II # 16, Monday Afternoon