COMPLEX COMPOSITION AND COAMPLIFICATION OF SAS AND MDM2 IN RING AND GIANT ROD MARKER CHROMOSOMES IN WELL-DIFFERENTIATED LIPOSARCOMA

Extra abnormal chromosomes (rings and giant rods) containing chromosom e 12 sequences are characteristic of well-differentiated liposarcoma ( WDLPS). By whole chromosome painting we found in 6 WDLPS that minimall y 5 chromosomes had contributed to the formation of the extra abnormal chromosomes. To the constant chromosome 12 contribution, sequences we re variably added from chromosomes 1, 4, and 16. Material from chromos omes 1, 4, and 12 was identified by painting in interphase nuclear pro jections (''blebs'') and in micronuclei consistent with the concept th at blebs are precursors to micronuclei. The complexity of the mechanis ms generating the extra abnormal chromosomes in WDLPS was also atteste d to by the diversity and, in some cases, intricacy of the patterns of fluorescence. To begin to fathom the function of the extra abnormal c hromosomes we examined the amplification of genes, including SAS, MDM2 , and GADDI53/CHOP, known to be in the region 12q13-14. SAS and MDM2 d emonstrated constant co-amplification. GADDI53/CHOP, which is critical ly rearranged in myxoid liposarcoma, was not amplified in WDLPS. (C) 1 994 Wiley-Liss, Inc.