Unraveling KDM4 histone demethylase expression and its association with adverse cytogenetic findings in chronic lymphocytic leukemia.

The acquisition of complex karyotypes is related to the progression of chronic lymphocytic leukemia (CLL) and patients with this condition have a poor prognosis. Despite recent advances in the classification of prognosis in CLL patients, understanding of the molecular mechanisms that lead to genomic instability and progression of this disease remains inadequate. Interestingly, dysregulated expression of KDM4 members is involved in the progression of several cancer types and plays a role in the DNA damage response; however, the gene expression profile and the importance of KDM4 members in CLL are still unknown. Here, we assessed the gene expression profile of KDM4A, KDM4B, and KDM4C in 59 CLL samples and investigated whether these histone demethylases have any influence on the prognostic markers of this leukemia. KDM4A gene expression was higher in CLL patients as compared with control samples. In contrast, CLL samples showed decreased levels of the KDM4B transcript in relation to control cases, and no difference was detected in KDM4C expression. Furthermore, patients with positive expression of ZAP-70 had lower expression of KDM4B and KDM4C as compared with ZAP-70-negative patients. More importantly, patients with low expression of these histone demethylases had higher leukemic cell numbers and displayed adverse cytogenetic findings and the acquisition of a complex karyotype. The present data clearly show that the expression of KDM4 members is dysregulated in CLL and impact the prognosis of this leukemia. These findings are useful for a better understanding of the impact of epigenetics on CLL progression.

Overexpression of EZH2 associates with a poor prognosis in chronic lymphocytic leukemia.

EZH2, a histone methyltransferase, is overexpressed in several human tumors, but whether it exerts any impact in chronic lymphocytic leukemia (CLL) remains unknown. We used real time PCR to investigate the expression profile of EZH1 and EZH2 in 59 CLL patients, 10 samples of purified B-cells from healthy donors and 12 normal adult tissues. EZH2 was overexpressed in CLL patients and correlates with high white blood cell count, ZAP-70 expression and chromosomal abnormalities. EHZ1 expression does not correlate with CLL progression. EZH2 overexpression is related to a poor prognosis of CLL and could be a useful tool to assess its aggressiveness.

Analysis of CD38 and ZAP70 mRNA expression among cytogenetic subgroups of Iranian chronic-lymphocytic-leukemia patients.

Chromosomal abnormalities and ZAP70 expression profile are two major independent prognostic markers in B-cell chronic lymphocytic leukemia. We investigated a possible correlation between these two markers. ZAP70 expression using real-time RT-PCR was examined in 20 B-cell chronic lymphocytic leukemia patients with del13q14, 13 patients with del11q22, 15 patients with trisomy 12, and 16 patients with no detected chromosomal abnormalities. Molecular analysis revealed that ZAP70 expression in the del13q subgroup was the same as in the control group, while it increased 2.78-fold in the del11q subgroup and 2.95-fold in the trisomy 12 subgroup, compared to the 15 cases in the control group. Comparison of the mean and standard deviation of the ZAP70 expression profile within the subgroups showed it to be highly variable among the individuals of the del11q and trisomy 12 subgroups, versus tight clustering for the del13q subgroup. Therefore, there is a correlation between del13q aberration, which has good prognosis with normal levels of ZAP70 expression. Due to a high degree of variation, no conformity is seen for del11q and trisomy 12 subgroups, making this grouping poor for prognostic discrimination. As a result, neither of these markers can serve as sole discriminators to determine the course of the disease; the use of both markers improves prognostic assessment.

CXCL12-induced chemotaxis is impaired in T cells from patients with ZAP-70-negative chronic lymphocytic leukemia.

BACKGROUND: T cells from patients with chronic lymphocytic leukemia may play an important role in contributing to the onset, sustenance, and exacerbation of the disease by providing survival and proliferative signals to the leukemic clone within lymph nodes and bone marrow. DESIGN AND METHODS: By performing chemotaxis assays towards CXCL12, CCL21 and CCL19, we sought to evaluate the migratory potential of T cells from chronic lymphocytic leukemia patients. We next analyzed the chemokine-induced migration of T cells, dividing the chronic lymphocytic leukemia samples according to their expression of the poor prognostic factors CD38 and ZAP-70 in leukemic cells determined by flow cytometry. RESULTS: We found that T cells from patients with chronic lymphocytic leukemia are less responsive to CXCL12, CCL21 and CCL19 than T cells from healthy adults despite similar CXCR4 and CCR7 expression. Following separation of the patients into two groups according to ZAP-70 expression, we found that T cells from ZAP-70-negative samples showed significantly less migration towards CXCL12 compared to T cells from ZAP-70-positive samples and that this was not due to defective CXCR4 down-regulation, F-actin polymerization or to a lesser expression of ZAP-70, CD3, CD45, CD38 or CXCR7 on these cells. Interestingly, we found that leukemic cells from ZAP-70-negative samples seem to be responsible for the defective CXCR4 migratory response observed in their T cells. CONCLUSIONS: Impaired migration towards CXCL12 may reduce the access of T cells from ZAP-70-negative patients to lymphoid organs, creating a less favorable microenvironment for leukemic cell survival and proliferation.

Bortezomib induces different apoptotic rates in B-CLL cells according to IgVH and BCL-6 mutations.

BACKGROUND: B-cell chronic lymphocytic leukemia (B-CLL) is a remarkably heterogeneous disorder. Some patients have an indolent disease whereas others undergo a more agressive presentation needing treatment. New therapeutics approaches are necessary for the treatment of B-CLL. Bortezomib (Btz), is a proteasome inhibitor, currently undergoing clinical trials whose function, at least in part, by stabilizing the IkappaBalpha protein and inhibiting NFkappaB activation. OBJECTIVE: The objective of this work was to study the effects of Btz on isolated human B-CLL cells, in vitro, and to correlate the differential rates of apoptosis induction with biological variables. MATERIAL AND METHODS: 31 B-CLL samples, from patients in stage A of Binet were used for this study, and the apoptotic effect of Btz on these cells was measured. RESULTS: Our data show that Btz treatment of B-CLL cells induces apoptosis in a time and dose-dependent manner. The apoptosis induction is mediated in part by inhibition of NFkappaB and is dependent on caspases activation. Interesting, in IgVH mutated cells, Btz have statistically significant differences in their in vitro activity on B-CLL cells according to their BCL-6 mutational status. CONCLUSIONS: Btz is a promising pharmacologic agent for the treatment of B-CLL, but its efficacy seems to be related to IgVH and BCL-6 mutational status, therefore, it could be interesting to further investigate the mechanisms involved in the different behavior of the cells in response to apoptosis induction by this drug.