ABSTRACT
OBJECTIVES: Chromosomal translocations are among the most common mutational events in cancer development, especially in hematologic malignancies. However, the precise molecular mechanism of these events is still not clear. It has been recently shown that alternative non-homologous end-joining (alt-NHEJ), a newly described pathway for double-stranded DNA break repair, mediates the formation of chromosomal translocations. Here, we examined the expression levels of the main components of alt-NHEJ (PARP1 and LIG3) in acute myeloid leukemia (AML) patients and assessed their potential correlation with the formation of chromosomal translocations. MATERIALS AND METHODS: This experimental study used reverse transcription-quantitative polymerase chain reaction (RTqPCR) to quantify the expression levels of PARP1 and LIG3 at the transcript level in AML patients (n=78) and healthy individuals (n=19). RESULTS: PARP1 was the only gene overexpressed in the AML group when compared with healthy individuals (P=0.0004), especially in the poor prognosis sub-group. Both genes were, however, found to be up-regulated in AML patients with chromosomal translocations (P=0.04 and 0.0004 respectively). Moreover, patients with one isolated translocation showed an over-expression of only LIG3 (P=0.005), whereas those with two or more translocations over-expressed both LIG3 (P=0.002) and PARP1 (P=0.02). CONCLUSIONS: The significant correlations observed between PARP1 and LIG3 expression and the rate of chromosomal translocations in AML patients provides a molecular context for further studies to investigate the causality of this association.
ABSTRACT
In acute myeloid leukemia (AML) the functional abnormalities of osteopontin (OPN), NF-kB, PI3K/AKT/mTOR/PTEN pathway or ß-catenin have been considered. AIM: To analyze the response of U937 cells to parthenolide (PTL) through the involvement of expression of OPN protein, RelB, AKT1, mTOR, PTEN and ß-catenin genes. MATERIALS AND METHODS: The U937 cells were treated with PTL at concentrations of 4 µM (IC25) or 6 µM (IC50) and with OPN siRNA for MTT assay and colony forming assay. Western blot analysis using antibodies against OPN was performed with lysates of PTL-treated cells. Quantitative real-time polymerase chain reaction was performed using primers for OPN siRNA, RelB, AKT1, mTOR, PTEN and ß-catenin. RESULTS: PTL reduces OPN protein level and down-regulates RelB mRNA in U937 cell line. Suppression of OPN with siRNA increases the cytotoxic effects of PTL. Also, mRNA expression of AKT1, mTOR, PTEN, and ß-catenin decreases with PTL or OPN siRNA. CONCLUSION: Sensitivity of U937 cells to PTL can be associated with the reduction in expression of prosurvival mediators.