ISHL10 Abstract T004

Analysis of the mutational landscape and dynamics in Hodgkin Lymphoma using NGS

Few studies have been aimed to the identification of driver mutations in classical Hodgkin Lymphoma (cHL), and only occasional gene mutations in members of the NF-kappaB and JAK/STAT pathways, and, more recently B2M, have been previously described.

We analyzed 57 cHL tumor samples (FFPE) using massive parallel sequencing (Ion Torrent™ semiconductor technology). To increase coverage a previous tumor cell enrichment process by punch tissue cores from selected tumor-rich areas was implemented. In addition, we have also analyzed an independent group of 12 patients with primary refractory cHL (patients that did not achieve complete response after first line ABVD, or who presented with primary progressive disease), using the same methodology for NGS, but with an enrichment procedure based on laser microdissection of HRS cells (CD30+).

Overall, the results show very high genomic heterogeneity with a range of 10-400 SNVs per sample, most of them (~60%) missense type. We found a relatively large number of genes recurrently mutated at low frequency and only a few genes mutated in up to 15-20% of the patients, reflecting a high level of genomic instability in the neoplasm. Specific mutations in genes previously described in cHL (NFKBIA, TNFRSF14) and in diffuse large B-cell lymphomas (CARD11, STAT6, CREBBP, CMYB) were consistently found, as well as new SNVs in genes not previously described (STAT6, BTK, NFKB2).

Of note, we found high prevalence of mutations affecting BTK and the BCR pathway, suggesting some dependencies of active BCR signaling albeit the absence of BCR expression by HRS cells. Consistent with this interpretation, incubation of a panel of cHL cellular models with either Ibrutinib or AVL-292, selective-BTK inhibitors, in vitro constrains cell proliferation and causes cell death. Indeed, gene expression and GSEA analysis of the cHL HDML-2 cell line showed a similar basal BCR pathway activation levels than the HBL1 DLBCL cell followed by an intense inhibition after ibrutinib incubation.

In conclusion, cHL is characterized by high genomic instability, including numerous mutations in genes related with B-cell function and specific signaling pathways. Pathogenic predictions of the different SNVs identify potential driver mutations that can be associated with the pathogenesis of the disease and might represent new therapeutic targets.