PT-006 - A GENOME-WIDE DNA METHYLATION ANALYSIS REVEALS DIFFERENT METHYLATION PATTERNS AND MECHANISTIC CLUES OF MEDICATION-RELATED OSTEONECROSIS OF THE JAW.

R. Alshammari^1,2, M. Tantawy³, E. Castro-Hall⁴, M. Abreu⁵, A. Villa⁵, G. Yang⁶, J. Katz⁷, L. Holliday⁷, Y. Gong⁸; ¹College of Pharmacy, University of Florida, Gainesville, FL, United States, ²College of Pharmacy, University of Hail, Hail city, Hail region, Saudi Arabia, ³College of Pharmacy, Unuversity of Florida, Gainesville, FL, United States, ⁴Miami Cancer Institute, Baptist Health South Florida, Miami, United States, ⁵Miami Cancer Institute, Baptist Health South Florida, ⁶Feinberg School of Medicine, Northwestern University, , United States, ⁷University of Florida, College of Dentistry, ⁸Department of Pharmacotherapy and Translational Research and Center for Pharmacogenomics and Precision Medicine, University of Florida College of Pharmacy, Gainesville, FL, USA.

Background: Medication-related osteonecrosis of the jaw (MRONJ) is a rare condition associated with severe side effects resulting from the use of bone-modifying agents, such as bisphosphonates (BP) and denosumab (DMB). The pathogenesis of MRONJ remains unclear. Three mechanisms were hypothesized: bone remodeling, inflammation or infection, or angiogenesis inhibition. This epigenome-wide associations study (EWAS) aims to identify genes with differential methylation patterns between MRONJ cases and controls to better understand the underlying mechanisms of MRONJ.

Methods: Genome-wide DNA methylation analyses were performed on 24 cancer patients who had been treated with BP or DMB (12 cases and 12 controls). The Infinium® MethylationEPIC v2.0 BeadChip was utilized for DNA methylation measurement and quantile normalization applied to preprocess the data. DNA methylation was analyzed using linear regression with M value as the dependent variable using the R minfi package.

Results: Eight of the 901,102 CpGs analyzed were differentially methylated between MRONJ cases and controls with p < 1*10-5. Among these, one was hypomethylated and seven were hypermethylated in MRONJ cases compared to controls. Specifically, cg20000507 within the GABARAP gene, displayed hypomethylation in cases compared to controls (p = 8.4*10-6). Another CpG, Cg21289669, located in the CpG island in the TNXB gene, showed hypermethylation in cases (p=9.8*10-6). The beta values of these two CpGs sites are shown in the figure.

Conclusion: In this first EWAS of MRONJ, we identified eight loci that were differentially methylated in MRONJ cases vs. controls, including two genes with plausible mechanistic explanations for the development of MRONJ. The hypomethylation of GABARAP leads to its upregulation, which is associated with suppressing the expression of two key proteins: VEGF and HIF-1α, which play vital roles in angiogenesis and the regulation of cellular apoptosis. Hypermethylation of TNXB reduces its expression, and literature indicates that Tenascin-X deficiency in mice leads to marked bone loss, higher osteoclast marker expression, and increased bone resorption due to increased osteoclast multinucleation. Further in-depth investigations including subanalysis of BP and DMB patients are ongoing.