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

Background Chromosome breakage could influence the expression of genes. This 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 detected breakpoint 16p11 in myxoid LPS, the presence of the FUS-CHOP fusion transcript in nonmyxoid LPS and the expression of the lung resistance major vault protein (LRP) gene on 16p11.2.

Materials and methods Of 16 cases with a diagnosis of a (possible) liposarcoma with an abnormal karyotype, fresh frozen tumour material was available for immunohistological detection of LRP. Cases without a cytogenetically detected t(12; 16)(q13; p11), were analyzed for the presence of a FUS-CHOP fusion transcript by RT-PCR.

Results In all 9 myxoid LPS a t(12; 16)(q13; p11) was found and LRP expression was absent or low. In none of the remaining 7 cases was a FUS-CHOP fusion transcript found, and four tumours were LRP positive (P = 0.02). LRP expression in myxoid LPS (mean: 1.3%) was lower (P = 0.07) than in the nonmyxoid tumours (mean: 35.7%).

Conclusions These observations indicate a relation between the t(12; 16)(q13; 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.