Molecular characterization of a complex chromosomal rearrangement in a pleomorphic salivary gland adenoma involving the 3'-UTR of HMGIC.

Recently, the high mobility group protein gene, HMGIC, was identified as a common genetic denominator in benign tumors with chromosome 12q13-15 aberrations, such as lipomas, uterine leiomyomas, pleomorphic adenoma of the salivary glands, hamartomas of breast and lung, angiomyxomas, and endometrial polyps. In most cases, the rearrangements resulted in the separation of the three HMGIC DNA-binding motifs from the acidic carboxy-terminal tail. Here, we report about the molecular characterization of a case of pleomorphic adenoma carrying a t(1;12)(p22;q15). Studies were performed on a cell line derived from the primary tumor, i.e., cell line Ad-312/SV40. Although the chromosome 12 breakpoint was initially mapped more than 1 Mb distal to the HMGIC gene by fluorescence in situ hybridization (FISH) analysis, the present molecular studies reveal a more complex chromosomal rearrangement that directly affects the HMGIC gene. Using 3'-RACE analysis, a HMGIC fusion transcript was detected that contained the complete HMGIC, coding region but lacked the putative mRNA destabilizing AUUUA motifs that are normally present in the 3'-UTR of HMGIC. Wild-type HMGIC transcripts were also detected in the tumor cells. The results suggest that alterations in the 3'-noncoding region of HMGIC may have to be considered as pathogenetically relevant.