Methylation profiling of mediastinal gray zone lymphoma reveals a distinctive signature with elements shared by classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma.

BACKGROUND: Mediastinal gray zone lymphoma is a newly recognized entity with transitional morphological and immunophenotypic features between the nodular sclerosis subtype of Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma. Diagnostic criteria for mediastinal gray zone lymphoma are still challenging, and the optimal therapy is as yet undetermined. Epigenetic changes have been implicated in the loss of the B-cell program in classical Hodgkin's lymphoma, and might provide a basis for the immunophenotypic alterations seen in mediastinal gray zone lymphoma. DESIGN AND METHODS: We performed a large-scale DNA methylation analysis of microdissected tumor cells to investigate the biological underpinnings of mediastinal gray zone lymphoma and its association with the related entities classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma, making comparisons with the presumptively less related diffuse large B-cell lymphoma. RESULTS: Principal component analysis demonstrated that mediastinal gray zone lymphoma has a distinct epigenetic profile intermediate between classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma but remarkably different from that of diffuse large B-cell lymphoma. Analysis of common hypo- and hypermethylated CpG targets in mediastinal gray zone lymphoma, classical Hodgkin's lymphoma, primary mediastinal large B-cell lymphoma and diffuse large B-cell lymphoma was performed and confirmed the findings of the principal component analysis. Based on the epigenetic profiles we were able to establish class prediction models utilizing genes such as HOXA5, MMP9, EPHA7 and DAPK1 which could distinguish between mediastinal gray zone lymphoma, classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma with a final combined prediction of 100%. CONCLUSIONS: Our data confirm a close relationship between mediastinal gray zone lymphoma and both classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma. However, important differences were observed as well, allowing a clear distinction from both parent entities. Thus, mediastinal gray zone lymphoma cannot be assigned to either classical Hodgkin's lymphoma or primary mediastinal large B-cell lymphoma, validating the decision to create an intermediate category in the World Health Organization classification.

A Comparison of Isogenic Homozygous Clone and Wildtype Zebrafish (Danio rerio): Survival and Developmental Responses to Low pH Conditions.

The value of bioassays as analytical methods for assessing the potency of particular stressors on live animal models depends on the precision of their results, which are greatly influenced by the choice of test subjects. The genetic makeup of experimental subjects varies, and, as such, so will their responses to the test environment. Genetic diversity of test populations may contribute to statistical variability; therefore, the use of genetically similar subjects may enhance the utility of bioassays. This study addresses the efficacy of using isogenic homozygous zebrafish (Danio rerio) as subjects for bioassays. Stress responses (acidic conditions) were compared during early development for gynogenetically produced isogenic homozygous line of zebrafish (C32) and wildtype (WT) zebrafish. Experiments evaluated early life stage milestones after exposure to low pH in water of a different electrolyte composition. Because the isogenic homozygous clonal (IHC) fish possessed far less genetic variability than the WT fish tested, it was predicted that the IHC fish would exhibit less variability in their response to stress. Although we found no significant differences in the variability between the responses of the IHC and WT fish, pH and water hardness level had a differential effect on the two groups. Simple strain differences may be the probable cause of the response differences to environmental stress. Factors that may affect stress response, such as heterogeneity, co-adapted gene complexes, and domestication, are discussed. Our findings and review of recent zebrafish literature stress the need for researchers to carefully consider breeding histories and trait characteristics for each potential test subject to maximize the sensitivity of the assay.