The Polycomb group (PcG) of genes is important for differentiation and cell-cycle regulation and is aberrantly expressed in several cancers. To analyse the role of deregulated PcG genes in acute myeloid leukaemia (AML), we determined by RQ-PCR the expression of the PcG genes BMI-1, MEL18, SCML2, YY1 and EZH2, and the downstream PcG targets HOXA4, HOXA9 and MEIS1 in diagnostic bone marrow samples from 126 AML patients. There was a general overexpression of the genes in AML patients compared to 20 healthy donors, except of HOXA4 and MEL18, which both displayed a wide range of expression levels within the AML subgroups. Among the AML patients with normal karyotype, a low HOXA4 level was associated with a shorter overall survival (P = 0.005). In addition, expression levels of MEL18 and EZH2 were significantly (P < 0.025) higher in patients with complex karyotype and lower in CBF-mutated patients. The t(8;21) vs. inv(16) positive patients showed significantly different expression of SCML2, BMI-1, YY1, HOXA9 and MEIS1 (P < or = 0.01). Comparisons between the PcG and PcG-regulated genes and a number of clinical and molecular data revealed correlations to genes involved in DNA methylation (DNMT1, DNMT3B), apoptosis (BAX, CASPASE 3) and multidrug-resistance (MDR1, MRP ) (P < 0.01). In conclusion, our data suggest that the role of PcG and PcG-regulated genes in leukaemogenesis varies between, as well as within karyotypic subgroups.

HOXA4 gene expression is a predictor for outcome in normal karyotypic acute myeloid leukaemia (AML) patients. Given that Meis1 is a co-factor for Hox genes, we hypothesized that the combined expression of HOXA4 and MEIS1 might add prognostic information in these patients. When diagnostic samples from 246 AML patients were divided into three main groups based on gene expression levels of HOXA4 combined with MEIS1 we found that within the group of patients exhibiting low levels of HOXA4, those with a high expression of MEIS1 had a significantly worse outcome than those exhibiting low MEIS1 expression (P = 0.025). Moreover, this prediction was independent of cytogenetics, mutational status of the NPM1 and FLT3 genes as well as upon WBC and age. To evaluate the possible contribution of regulatory events underlying these observations, 157 patient samples were subjected to promoter hypermethylation analysis. We observed that 77% were HOXA4- and 15%MEIS1 hypermethylated and that this epigenetic alteration was highly correlated to the gene expression level (MEIS1: P = 0.001; HOXA4: P = 0.007). Finally, we found a higher expression level and a higher frequency of hypermethylation of HOXA4 among patients with NPM1 mutations. In conclusion, our data show that the combination of low HOXA4 and low MEIS1 gene expression is a favourable predictor for outcome in all AML patients and that the expression levels are governed by the methylation state of these genes.

Survival of diffuse large B-cell lymphoma (DLBCL) patients has improved by inclusion of rituximab. Refractory/recurrent disease caused by treatment resistance is, however, a major problem. Determinants of rituximab sensitivity are not fully understood, but effect of rituximab are enhanced by antagonizing cell surface receptor CXCR4. In a two-step strategy, we tested the hypothesis that prognostic value of CXCR4 in DLBCL relates to rituximab treatment, due to a hampering effect of CXCR4 on the response of DLBCL cells to rituximab. First, by investigating the prognostic impact of CXCR4 mRNA expression separately for CHOP (n=181) and R-CHOP (n=233) cohorts and, second, by assessing the interaction between CXCR4 and rituximab in DLBCL cell lines. High CXCR4 expression level was significantly associated with poor outcome only for R-CHOP-treated patients, independent of IPI score, CD20 expression, ABC/GCB and B-cell-associated gene signature (BAGS) classifications. s. For responsive cell lines, inverse correlation was observed between rituximab sensitivity and CXCR4 surface expression, rituximab induced upregulation of surface-expressed CXCR4, and growth-inhibitory effect of rituximab increased by plerixafor, supporting negative impact of CXCR4 on rituximab function. In conclusion, CXCR4 is a promising independent prognostic marker for R-CHOP-treated DLBCL patients, possibly due to inverse correlation between CXCR4 expression and rituximab sensitivity.

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Within recent years, many precision cancer medicine initiatives have been developed. Most of these have focused on solid cancers, while the potential of precision medicine for patients with hematological malignancies, especially in the relapse situation, are less elucidated. Here, we present a demographic unbiased and observational prospective study at Aalborg University Hospital Denmark, referral site for 10% of the Danish population. We developed a hematological precision medicine workflow based on sequencing analysis of whole exome tumor DNA and RNA. All steps involved are outlined in detail, illustrating how the developed workflow can provide relevant molecular information to multidisciplinary teams. A group of 174 hematological patients with progressive disease or relapse was included in a non-interventional and population-based study, of which 92 patient samples were sequenced. Based on analysis of small nucleotide variants, copy number variants, and fusion transcripts, we found variants with potential and strong clinical relevance in 62% and 9.5% of the patients, respectively. The most frequently mutated genes in individual disease entities were in concordance with previous studies. We did not find tumor mutational burden or micro satellite instability to be informative in our hematologic patient cohort.