Predicting dedifferentiation in liposarcoma: a proteomic approach

There are no known morphologic characteristics, cytogenetic aberrations, or molecular alterations predictive of dedifferentiation in liposarcomas. Identification of such a prognostic marker could potentially affect surgical and adjuvant therapy and/or follow-up surveillance for these patients. Two-dimensional difference gel electrophoresis was utilized to characterize protein expression patterns in lipoma, atypical lipomatous tumor (ALT), and the well-differentiated components of dedifferentiated liposarcoma (DDL). Protein spots were identified by peptide mapping/fingerprinting using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. No significant differences in protein expression were identified between lipoma and ALT or DDL. Proteins that were significantly down-regulated in the well-differentiated component of DDL compared to ALT included mitochondrial aldehyde dehydrogenase 2 (ALDH2, > 3-fold reduction) and selenium-binding protein-1 (SELENBP1, > 4-fold reduction). Subsequent validation studies were performed by immunohistochemistry (IHC) on a separate series of ALT (n = 30) and the well-differentiated components of DDL (n = 28). IHC stains were evaluated in a semi-quantitative manner, and the results were analyzed using the Mann-Whitney test and receiver-operator curve analysis. Decreased IHC staining for SELENBP1 in the well-differentiated component of DDL was confirmed. Cytoplasmic ALDH2 levels determined by IHC were not significantly different in ALT and DDL; no nuclear staining for ALDH2 was observed. Expression of SELENBP1 is decreased in the well-differentiated component of DDL compared to ALT. However, variability in the staining patterns in liposarcoma precludes its use as a predictive marker for dedifferentiation.