Abstract P069

Analysis of circulating tumor DNA shows Epstein-Barr virus associated differences of mutagenic processes in classical Hodgkin lymphoma.

Background: About 30% of classical Hodgkin lymphomas (cHL) are associated with EBV (Epstein-Barr virus) infection. However, it is not fully understood how EBV positivity affects genetic profile of cHL and associated characteristics of circulating tumor DNA (ctDNA).

Methods: We prospectively analyzed pre-treatment plasma samples of 140 patients with cHL using Cancer Personalized Profiling by deep Sequencing (CAPP-Seq) and Clinical Lymphoma Exploration and Research Sequencing (CLEARS) panel (521 genes). COSMIC (Catalogue of Somatic Mutations in Cancer) mutational signatures were detected by SigProfiler. EBV status was determined by immunohistochemistry (LMP1), ISH (EBER), or qPCR (peripheral EBV DNA).

Results: Among 140 analyzed cHL patients, the median age at diagnosis was 39 years (range 19 – 77); the most frequent histological subtype was nodular sclerosis (64.7%; mixed cellularity - 28.7%; lymphocyte rich - 6.6%); most patients had advanced GHSG (German Hodgkin Study Group) clinical stage (70.1%; intermediate stage - 16.7%, early stage - 12.7%); 24% of patients were EBV positive. Advanced GSHG stage was associated with higher levels of pre-treatment ctDNA in comparison to patients with intermediate/early stages (18.4 vs. 8.1 ng/mL, respectively; P < 0.001). EBV positivity was associated with lower tumor mutational burden (median TMB 6.07 vs. 10.0 mut/Mb; P = 0.03) and a trend towards higher ctDNA concentration (mean 2.3 vs. 1.7 ng/mL; P = 0.13). Importantly, EBV+ tumors were largely missing alterations in several critical genes most frequently (20% of cases) altered in EBV- cases, namely in TNFAIP3 and NFKBIE (negative regulators of NFκB signaling) and in ITPKB (a negative regulator of PI3K/AKT signaling). Other cHL driver genes were altered in EBV+ and EBV- cHL tumors at similar frequencies (e.g., SOCS1, HLA-B, GNA13, or KMT2C). Based on identified mutagenic processes, EBV- cHL tumors showed higher contribution of activation induced cytidine deaminase (AID) and had evidence of mismatch repair deficiency (MMRD, which was missing in EBV+ tumors).

Conclusion: EBV positivity and related expression of viral proteins (e.g. LMP1) seems to trigger similar cellular signaling as alterations of several key driver genes in EBV- cHL. Consequently, EBV+ tumors need lower number of additional mutations and EBV- cHL is associated with other mutagenic processes, as are AID activity and MMRD.

Supported by NU22-03-00182, DRO-FNOl_00098892, DRO-VFN00064165, LX22NPO5102.