The recurrent translocation t(5;8)(p13;q12) in pleomorphic adenomas results in upregulation of PLAG1 gene expression under control of the LIFR promoter.

We have previously shown that the PLAG1 gene on chromosome 8q12 is consistently rearranged in pleomorphic adenomas of the salivary glands with t(3;8)(p21;q12) translocations. The t(3;8) results in promoter swapping between the PLAG1 gene, which encodes a novel zinc finger protein, and the constitutively expressed gene for beta-catenin (CTNNB1), a protein with roles in cell-cell adhesion and the WG/WNT signalling pathway. In order to assess the importance of other translocation partner genes of PLAG1, and their possible relationship to CTNNB1, we have characterized a second recurrent translocation, i.e. the t(5;8)(p13;q12). This translocation leads to ectopic expression of a chimeric transcript consisting of sequences from the ubiquitously expressed gene for the leukemia inhibitory factor receptor (LIFR) and PLAG1. As for the t(3;8), the fusions occurred in the 5'-noncoding regions of both genes, exchanging regulatory control elements while preserving the coding sequences. The results of the current as well as previous studies indicate that ectopic expression of PLAG1 under the control of promoters of distinct translocation partner genes is a general pathogenetic mechanism for pleomorphic adenomas with 8q12 aberrations.