Abstract B032: Genome-wide 5-hydroxymethylation mapping in cell-free DNA to characterize the epigenetic differences in minimal residual disease of multiple myeloma
Authors: Zhang Zhou , Wang Bei , Kowitwanich Krissana , Cursio John , Appelbaum Daniel , He Chuan , Zhang Wei , Derman Benjamin , Chiu Brian , Jakubowiak Andrzej 
Published: November 2024

Abstract
Background: Multiple myeloma (MM), a B-cell neoplasm characterized by the infiltration of malignant plasma cells into the bone marrow, is the second most common blood malignancy in the United States. The molecular pathogenesis of MM involves both genetic and epigenetic alterations. While 60-75% of newly diagnosed patients achieve a complete response or better with current modern combination therapies, almost all patients eventually progress largely due to the persistence or re-emergence of minimal residual disease (MRD). Monitoring for MRD has become essential for evaluating treatment efficacy and predicting long-term outcomes in MM patients. We aimed to investigate whether epigenetic changes, particularly 5- hydroxymethylcytosines (5hmC), at diagnosis are associated with MRD status following treatment. Methods: Utilizing 5hmC-Seal, a highly sensitive chemical labeling technique, we profiled genome-wide 5hmC in circulating cell-free DNA (cfDNA) and bone marrow genomic DNA (gDNA) at baseline and after 8 cycles of treatment (C8) from newly diagnosed MM patients (n=25) enrolled in a clinical trial (NCT01816971). MRD testing was performed on bone marrow samples using the clonoSEQ next generation sequencing assay (limit of detection 10-6). Results: The 5hmC modification levels were summarized across various genomic features, revealing enrichment in gene bodies and enhancer regions, consistent with the known regulatory role of 5hmC. We ranked 5hmC-modified genes at baseline by their variability, and found that the number of overlapping genes between cfDNA and gDNA was significantly higher than expected by permutation analysis. Subsequently, we identified the top 100 most variable 5hmC- modified genes in gDNA, which exhibited a higher Pearson correlation with cfDNA within individuals (mean r=0.90) compared to between individuals (mean r=0.82; p&lt;0.05), suggesting that cfDNA has the potential to reflect gDNA in capturing some MM-related variations. Among the 11 patients with MRD+ at C8, a genome-wide scan of 5hmC in cfDNA comparing baseline and C8 identified 1,614 differentially modified genes (p&lt;0.05) after adjusting for age and sex. [BC1] Furthermore, we identified 459 differentially modified genes comparing baseline 5hmC levels between patients who were MRD+ (n=11) and MRD- (n= 14) at C8 (p&lt;0.05), after adjusting for age and sex. These results highlight the differential epigenetic landscape associated with MRD status. Conclusions: Genome-wide 5hmC profiling of cfDNA from blood revealed a similar epigenetic landscape to gDNA from bone marrow in patients with MM, suggesting that cfDNA may offer a less invasive alternative for assessing epigenetic modifications. Moreover, this profiling identified distinct epigenetic changes associated with the achievement of MRD- negativity. These findings provide a foundation for further investigation into the molecular alterations linked to MM disease biology that could potentially lead to MRD negativity. Future directions will focus on identifying biomarkers that could inform personalized treatment strategies.
Citation Format: Zhou Zhang, Bei Wang, Krissana Kowitwanich, John Cursio, Daniel Appelbaum, Chuan He, Wei Zhang, Benjamin Derman, Brian Chiu, Andrzej Jakubowiak. Genome-wide 5-hydroxymethylation mapping in cell-free DNA to characterize the epigenetic differences in minimal residual disease of multiple myeloma [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr B032.