The evaluation of effect of imatinib and silimarin on BCR-ABL1, GRB2, GAB2, AKT and ERK gene expression levels in human myeloid leukemia cell line K562

BCR-ABL1 fusion gene, located on Philedelphia (Ph) chromosome has a major role in the pathogenesis of CML. Fusion protein, the product of this translocation, encodes a tyrosine kinase that activates AKT, ERK and STAT pathways. The modulators of BCR-ABL1 fusion protein are GRB2 (Growth factor receptor-bound protein 2) and GAB2 (Grb-2-associated binder 2) in the activation of cell signalling pathways. STI571, that is given to patients in CML treatment protocol, binds to the ATP-binding domain of tyrosine kinase enyzme by competative inhibition. The tyrosine phosphorylation of the proteins, responsible of BCR-ABL1 signalling, is inhibited. The aim of this study is to determine the effect of silimarin, a herbal flavonoid, treatment together with STI571 on human CML cell line K562 signalling pathways. K562 cells were maintained in RPMI 1640 medium, at 37°C in a 95% (v/v) humidified atmosphere of 5% (v/v) CO2. After determining the cytotoxic dose of STI571 by MTT test, cells were treated by STI571, silymarin, and combination of both STI571 and silymarin. Control group was not treated with any of the substances. After the treatment of cells with previously designated doses and times, mRNA were isolated and cDNA were synthesed. BCR-ABL1, GRB2, GAB2, AKT and ERK gene expression levels were analyzed with real-time PCR. In conclusion, the decrease of GAB2 and ERK gene exression levels was determined in K562 cells that are treated with imatinib and silimarin combination. Silimarin as dietary supplement may increase the effect of imatinib and supress the defined cell signalling pathways on drug resistance on CML cells. Key words: Chronic myelogenous leukemia, silymarin, imatinib, BCR-ABL1, GRB2, GAB2, AKT, ERK