The 16p11 breakpoint in myxoid liposarcomas might affect the expression ofthe LRP gene on 16p11.2 encoding the multidrug resistance associated majorvault protein

Background Chromosome breakage could influence the expression of genes. Thi s has been noticed in specific cases of acute myeloid leukaemia, where the 16p13 breakpoint affects the expression of the multidrug resistance related protein (MRP). Myxoid liposarcomas (LPS) are characterized by the t(12; 16 )(q13; p11), which leads to the formation of a FUS-CHOP fusion transcript. This study investigates the relationship between the cytogenetically detect ed breakpoint 16p11 in myxoid LPS, the presence of the FUS-CHOP fusion tran script in nonmyxoid LPS and the expression of the lung resistance major vau lt protein (LRP) gene on 16p11.2. Materials and methods Of 16 cases with a diagnosis of a (possible) liposarc oma with an abnormal karyotype, fresh frozen tumour material was available for immunohistological detection of LRP. Cases without a cytogenetically de tected t(12; 16)(q13; p11), were analyzed for the presence of a FUS-CHOP fu sion transcript by RT-PCR. Results In all 9 myxoid LPS a t(12; 16)(q13; p11) was found and LRP express ion was absent or low. In none of the remaining 7 cases was a FUS-CHOP fusi on transcript found, and four tumours were LRP positive (P = 0.02). LRP exp ression in myxoid LPS (mean: 1.3%) was lower (P = 0.07) than in the nonmyxo id tumours (mean: 35.7%). Conclusions These observations indicate a relation between the t(12; 16)(q1 3; p11), leading to a FUS-CHOP fusion transcript in myxoid LPS, and the low or absent expression of the LRP-gene located on 16p11.2.