Osteosarcoma (OS) is the most common primary bone malignancy affecting children and young adolescents. Downregulation of microRNAs at 14q32 locus is implicated in the pathogenesis of OS. However, array comparative genome hybridization did not show any DNA copy number loss at this locus. We hypothesized that epigenetic alterations may regulate genes and microRNAs present in this locus and contribute to the development and progression of OS. Here, we show that OS is characterized by a selective loss of imprinting (LOI) at 14q32 locus. LOI at the 14q32 locus was unique to OS, compared with 10 other cancer cell lines representing 6 tissue types. Furthermore, the average demethylation at 14q32 locus was 24%, but the global demethylation as determined by LINE-1 retrotransposons was only 7%. We also found LOI in H19, MEST, and PEG3 loci in OS samples, albeit less frequently. LOI at the 14q32 locus is highly prevalent (82.6%, 19 out of 23) only in OS patients with early-onset (12-30 years of age) of the disease. Imprinted genes at 14q32 locus were downregulated in OS due to histone modifications and the locus was controlled by bivalent domain enriched with both K4-3m and K27-3m. We determined the tumor suppressor function of this locus by overexpression of 3 imprinting genes, DLK1, RTL1 or DIO3 in SaoS2 cells. We found that all 3 genes inhibited cell proliferation and enhanced apoptosis. We also tested methylation patterns using matched buccal DNA samples obtained from OS patients and their parents. Interestingly, loss of imprinting at 14q32 locus was found in most of the OS patients and their parents, suggesting that children might be predisposed to developing OS by inheriting the instability of imprinting at this genomic site. To determine if loss of imprinting at 14q32 locus is the driving mechanism, or a secondary genetic event, we evaluated tumor tissues obtained from p53LSLR270H/;Osx-Cre mice OS models. These mice developed OS at 8-12 months (potentially representing the late-onset (> 30yrs) of human OS). LOI was found only in 33% of mice OS samples, which is in agreement with the low rate of LOI detected in late-onset human OS. In conclusion, our findings suggest that LOI at the 14q32 genomic locus is likely a contributing event in the pathogenesis of OS. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4042. doi:1538-7445.AM2012-4042
Original languageEnglish (US)
StatePublished - 2012


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