ABSTRACT
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.
Subject(s)
Gene Expression Regulation, Enzymologic , Gene Expression Regulation, Leukemic , Leukemia, Lymphocytic, Chronic, B-Cell/diagnosis , Leukemia, Lymphocytic, Chronic, B-Cell/enzymology , Polycomb Repressive Complex 2/biosynthesis , Adult , Aged , Aged, 80 and over , Enhancer of Zeste Homolog 2 Protein , Female , Humans , Male , Middle Aged , Prognosis , Real-Time Polymerase Chain Reaction , ZAP-70 Protein-Tyrosine Kinase/biosynthesisABSTRACT
The histone lysine methyltransferases contain a SET domain, which catalyzes the addition of methyl groups to specific lysine residues. The MLL family of genes encodes histone-modifying enzymes with histone 3-lysine 4 methyltransferase activity that can regulate gene transcription. The MLL family exists in multi-protein complexes and has been implicated in a variety of processes including normal development and cell growth. Although some of the MLL family members have already been described to be involved in cancer, a clear relationship of these genes with breast cancer is not determined to date. In the present study, we used quantitative PCR to investigate the expression profile of all five MLL genes [MLL (ALL-1), MLL2, MLL3, MLL4 and MLL5] in 7 breast cancer cell lines, 8 breast tumors and adjacent non-tumor tissues and in 12 normal tissues. We observed a diminished expression of all five genes in the breast cancer cell lines when compared to normal breast tissue. We found a significantly decreased expression of MLL2 in the tumor samples compared to the non-tumor controls. In tumor samples, MLL5 also showed a clear suppression tendency. Among the normal tissues analyzed, all genes showed a markedly higher expression in skeletal muscle and brain. Although further studies are required to determine the exact role of these methyltransferases in cancer development, our results indicate that the suppression of MLL genes, especially MLL2 and 5, take part in modulating breast carcinogenesis. Our assessment of the MLL family gene expression patterns in a diverse set of breast cancer cell lines and in a multitude of tissue types and breast tumors should lead to increasingly detailed information on the involvement of these genes in cancer progression.