Long Non-coding RNA HOTAIR Expression in Diffuse Large B-Cell Lymphoma: In Relation to Polycomb Repressive Complex Pathway Proteins and H3K27 Trimethylation.

BACKGROUND: A long non-coding RNA hox transcript antisense intergenic RNA (HOTAIR) is involved in epigenetic regulation through chromatin remodeling by recruiting polycomb repressive complex 2 (PRC2) proteins (EZH2, SUZ12, and EED) that induce histone H3 trimethylation at lysine 27 (H3K27me3). Deregulation of c-MYC and interaction between c-MYC and EZH2 are well known in lymphomagenesis; however, little is known about the expression status of HOTAIR in diffuse large B-cell lymphomas (DLBCLs). METHODS: The expression status of PRC2 (EZH2, SUZ12, and EED), H3K27me3, c-MYC, and BCL2 was analyzed using immunohistochemistry (n = 231), and HOTAIR was investigated by a quantification real-time polymerase chain reaction method (n = 164) in DLBCLs. RESULTS: The present study confirmed the positive correlation among PRC2 proteins, H3K27me3, and c-MYC in DLBCLs. Expression level of HOTAIR was also positively correlated to EZH2 (p < .05, respectively). Between c-MYC and HOTAIR, and between c- MYC/BCL2 co-expression and HOTAIR, however, negative correlation was observed in DLBCLs (p < .05, respectively). High level of H3K27me3 was determined as an independent prognostic marker in poor overall survival (hazard ratio, 2.0; p = .023) of DLBCL patients. High expression of HOTAIR, however, was associated with favorable overall survival (p = .004) in the univariate analysis, but the impact was not significant in the multivariate analysis. The favorable outcome of DLBCL with HOTAIR high expression levels may be related to the negative correlation with c- MYC expression or c-MYC/BCL2 co-expression. CONCLUSIONS: HOTAIR expression could be one of possible mechanisms for inducing H3K27me3 via EZH2-related PRC2 activation, and induced H3K27me3 may be strongly related to aggressive DLBCLs which show poor patient outcome.

Activation of the polycomb repressive complex pathway in the bone marrow resident cells of diffuse large B-cell lymphoma patients.

The present study investigated the activation of polycomb repressive complex 2 (PRC2) pathway proteins in the resident cells within the bone marrow hematopoietic microenvironment of diffuse large B-cell lymphoma (DLBCL) patients. PRC2 proteins (enhancer of zeste homolog 2, suppressor of zeste 12 homolog, and embryonic ectoderm development), histone methylation mark (H3K27me3), and c-MYC activation were evaluated in pretreatment bone marrow from 208 DLBLC patients. Positive expression of the PRC2, H3K27me3, and c-MYC in the bone marrow resident cells was more frequent in cases with bone marrow involvement of tumor. The expression among PRC2, H3K27me3 mark, and c-MYC was closely correlated. Positive PRC2 expression in bone marrow resident cells was significantly associated with inferior progression-free survival (PFS) and overall survival (OS) and determined to be an independent prognostic factor of inferior PFS and OS. In conclusion, the PRC pathway was frequently activated in bone marrow resident cells of DLBCL patients, and PRC activation was tumor-related and associated with poor clinical outcomes.

Diffuse large B-cell lymphoma with histone H3 trimethylation at lysine 27: another poor prognostic phenotype independent of c-Myc/Bcl2 coexpression.

Deregulation of histone H3 trimethylation at lysine 27 (H3K27me3) via aberration of the histone methyltransferase, enhancer of zeste homologue 2 (EZH2), is suggested to play a critical role in cancers including hematologic malignancies. In the present study, implications of H3K27me3 were investigated in diffuse large B-cell lymphoma (DLBCL) with respect to clinicopathological factors, especially in association with c-Myc/Bcl2 coexpression and germinal center B-like (GCB) or non-GCB subtype. By immunohistochemistry, a high level of H3K27me3 was observed in approximately one-third (35.3%, 79/224) of DLBCL cases, and this subset of cases was related to poor performance status (Eastern Cooperative Oncology Group scores ≥ 2) (P = .013), elevated lactate dehydrogenase level (P = .001), and a higher international prognostic index risk group (scores ≥3) (P = .005). H3K27me3 level was significantly correlated with EZH2 expression (P = .004) and c-Myc protein expression (P = .003) but not correlated with c-Myc/Bcl2 coexpression or with GCB or non-GCB subtype. A high level of H3K27me3 was related to an inferior overall survival (P = .006) and was shown to be an independent prognostic factor for overall survival along with the higher international prognostic index risk group and c-Myc/Bcl2 coexpression. In conclusion, H3K27me3 was related to EZH2 and c-Myc expression, suggesting formation of a MYC-EZH2-H3K27me3 loop in a subgroup of DLBCL cases. H3K27me3 was associated with poor patient outcome and revealed as an independent predictor for overall survival of DLBCL patients. H3K27me3 in DLBCL may be another high-risk phenotype independent of the phenotype of c-Myc/Bcl2 coexpression or other known poor prognostic subgroups.

Long Non-coding RNA HOTAIR Expression in Diffuse Large B-Cell Lymphoma: In Relation to Polycomb Repressive Complex Pathway Proteins and H3K27 Trimethylation

BACKGROUND: A long non-coding RNA hox transcript antisense intergenic RNA (HOTAIR) is involved in epigenetic regulation through chromatin remodeling by recruiting polycomb repressive complex 2 (PRC2) proteins (EZH2, SUZ12, and EED) that induce histone H3 trimethylation at lysine 27 (H3K27me3). Deregulation of c-MYC and interaction between c-MYC and EZH2 are well known in lymphomagenesis; however, little is known about the expression status of HOTAIR in diffuse large B-cell lymphomas (DLBCLs). METHODS: The expression status of PRC2 (EZH2, SUZ12, and EED), H3K27me3, c-MYC, and BCL2 was analyzed using immunohistochemistry (n = 231), and HOTAIR was investigated by a quantification real-time polymerase chain reaction method (n = 164) in DLBCLs. RESULTS: The present study confirmed the positive correlation among PRC2 proteins, H3K27me3, and c-MYC in DLBCLs. Expression level of HOTAIR was also positively correlated to EZH2 (p < .05, respectively). Between c-MYC and HOTAIR, and between c- MYC/BCL2 co-expression and HOTAIR, however, negative correlation was observed in DLBCLs (p < .05, respectively). High level of H3K27me3 was determined as an independent prognostic marker in poor overall survival (hazard ratio, 2.0; p = .023) of DLBCL patients. High expression of HOTAIR, however, was associated with favorable overall survival (p = .004) in the univariate analysis, but the impact was not significant in the multivariate analysis. The favorable outcome of DLBCL with HOTAIR high expression levels may be related to the negative correlation with c- MYC expression or c-MYC/BCL2 co-expression. CONCLUSIONS: HOTAIR expression could be one of possible mechanisms for inducing H3K27me3 via EZH2-related PRC2 activation, and induced H3K27me3 may be strongly related to aggressive DLBCLs which show poor patient outcome.