Analysis of genome-wide DNA methylation profile according to Chlamydophila psittaci infection and the response to doxycycline treatment in ocular adnexal MALT lymphoma of Korean

Abstract

Background and purpose: Lymphomas of the ocular adnexa are the most common malignant tumor arising from the ocular adnexa. In Korea, extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) accounts for a higher proportion than in western countries. Chlamydophila psittaci (Cp) is suggested to be a possible etiologic agent for ocular adnexal MALT lymphoma and Cp-eradicating treatment using doxycycline antibiotics has been attempted as a first-line targeted therapy in South Korea. Epigenetic alterations in association with aberrant promoter hypermethylation are also observed in MALT lymphomas, but genome-wide screening of DNA methylation profiles has not been performed. In this study, we compared genome-wide DNA methylation profiles according to Cp infection status and the response to doxycycline treatment in a Korean ocular adnexal MALT lymphoma patients.

Methods: Twelve ocular adnexal MALT lymphoma cases were classified into two groups (6 Cp-positive cases and 6 Cp-negative cases). Among the 12 cases, 8 were treated with doxycycline as a first-line therapy, and they were divided into 2 groups according to their response to the treatment (4 Doxy-responders and 4 Doxy-nonresponders). The differences in the DNA methylation states of 27,578 methylation sites in 14,000 genes were evaluated using Illumina bead assay technology. We also validated the top-ranking differentially methylated genes (DMGs) by bisulfite direct sequencing or pyrosequencing.

Results: The Infinium Methylation chip assay revealed 180 DMGs in the Cp-positive group (74 hypermethylated genes and 106 hypomethylated genes) compared to the Cp-negative group. Among the 180 DMGs, DUSP22, which had 2 significantly hypomethylated loci, was validated, and the correlation was significant for one CpG site (Spearman coefficient = 0.6478, p = 0.0262). With regard to the response to doxycycline treatment, a total of 778 DMGs were revealed (389 hypermethylated genes and 336 hypomethylated genes in the Doxy-responder group). In a subsequent replication study for representative hypomethylated (IRAK1) and hypermethylated (CXCL6) genes, the correlation between the bead chip analysis and pyrosequencing was significant (Spearman coefficient = 0.8961 and 0.7619, respectively, p < 0.05).

Conclusions: Ocular adnexal MALT lymphoma showed distinct methylation patterns according to Cp infection and the response to doxycycline treatment in this genome-wide methylation study. Among the candidate genes, DUSP22 has a methylation status that was likely attributable to Cp infection. Our data also suggest that the methylation statuses of IRAK1 and CXCL6 may reflect the response to doxycycline treatment.