MDM2 Amplification in Atypical Lipomatous Tumors/Well-Differentiated Liposarcomas and Dedifferentiated Liposarcomas: A Comparative RT-PCR and FISH Study
JG Willems, M Gjihaderi, A Olsson, M Lestrin, G Elmberger. Karolinska University Hospital Solna, Stockholm, Sweden
Background: As future therapeutic options for well-differentiated and dedifferentiated liposarcomas are likely to include targeting the MDM2 pathway, reliable methods for its demonstration will be required. A comparative study of the sensitivity of RT-PCR versus FISH for demonstrating amplification of MDM2 in such tumors was therefore performed.
Design: 30 consecutive resected atypical lipomatous tumors/well-differentiated liposarcomas and dedifferentiated liposarcomas as well as 6 control adipocytic tumors of different type, were reviewed by two pathologists and subsequently investigated for amplification of MDM2. Genomic DNA was extracted from formalin fixed paraffin embedded tissues using the Qiagen Qia Amp FFPE kit. Fifty nanogram of each FFPE DNA was used in a multiplex real-time PCR reaction using the FAM (MDM2) and VIC (RNase P as internal control) labeled probes on an ABI prism 7000. To distinguish samples with high MDM2 copy number from those with normal copy number, the standard delta-Ct method was used. Neoplasms with high copy number were judged to be amplified. FISH dual copy assay was performed using Poseidon Repeat Free MDM2 (12q15) & SE12 control probe. More than 4 signals were considered evidence of amplification.
Results: 1-On FISH analysis 29 of 30 atypical lipomatous tumors/well-differentiated liposarcomas and dedifferentiated liposarcomas were found to be amplified for MDM2, whereas 1 case of dedifferentiated liposarcoma was not. 2- On RT-PCR analysis of the same 30 tumors, 28 showed MDM2 amplification. Unamplified were the above mentioned case of dedifferentiated liposarcoma and 1 case of well-differentiated liposarcoma of inflammatory type. 3- None of the adipocytic tumors of other type showed MDM2 amplification by either mehod.
Conclusions: In atypical lipomatous tumors/well-differentiated liposarcomas and dedifferentiated liposarcomas demonstration of MDM2 amplification as measured by FISH was 96,6 % and by RT-PCR 93,3 %. Following methodological adjustments results could be improved.
Wednesday, March 24, 2010 9:30 AM
Poster Session V # 230, Wednesday Morning