DNA damage response in imatinib resistant chronic myeloid leukemia K562 cells

CIGMH Human Molecular Genetics Research Center, Department of Genetics, Faculty of Medical Sciences, Universidade Nova de Lisboa, Lisboa, Portugal.
Leukemia & lymphoma (Impact Factor: 2.89). 04/2012; 53(10):2004-14. DOI: 10.3109/10428194.2012.681654
Source: PubMed


Resistance to imatinib in patients with chronic myeloid leukemia can lead to advanced disease and blast crisis. Conventional chemotherapy with DNA damaging agents is then used, alone or in combination with other tyrosine kinase inhibitors (TKIs). Our aim was to assess whether imatinib resistant K562 cells were also resistant to DNA damaging agents. After treatment with H(2)O(2) and doxorubicin, but not camptothecin, cell survival was higher in imatinib resistant cells compared to parental cells. DNA damage, measured by comet and γ-H2AX assays, was lower in imatinib resistant cells. mRNA expression levels of 50 genes of the DNA damage response pathway showed increased expression of the base excision repair (BER) genes MBD4 and NTHL1. Knockdown of MBD4 and NTHL1 expression in resistant cells using siRNA decreased cell survival after treatment with H(2)O(2) and doxorubicin. Our results indicate that imatinib resistant cells display cross-resistance to oxidative agents, partly through up-regulation of BER genes. Expression of these genes in imatinib resistant patients was not significantly different compared to sensitive patients. However, the strategy followed in this study could help identify chemotherapeutic agents that are more effective as alternative agents in cases of resistance to TKIs.

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    • "Next, we determined whether chamaejasmenin B and neochamaejasmin C could induce DNA damage in A549 and KHOS cells. The phosphorylation of H2AX (denoted as γ-H2AX) is a marker of DNA damage19. As shown in Figure 2A and 2B, the induction of γ-H2AX in both A549 and KHOS cells was observed by Western blot analysis, indicating that DNA damage might be involved in the anti-cancer effect of the 2 compounds. "
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    ABSTRACT: Aim: To examine the anti-cancer effects of chamaejasmenin B and neochamaejasmin C, two biflavonones isolated from the root of Stellera chamaejasme L (known as the traditional Chinese herb Rui Xiang Lang Du) in vitro. Methods: Human liver carcinoma cell lines (HepG2 and SMMC-7721), a human non-small cell lung cancer cell line (A549), human osteosarcoma cell lines (MG63, U2OS, and KHOS), a human colon cancer cell line (HCT-116) and a human cervical cancer cell line (HeLa) were used. The anti-proliferative effects of the compounds were measured using SRB cytotoxicity assay. DNA damage was detected by immunofluorescence and Western blotting. Apoptosis and cell cycle distribution were assessed using flow cytometry analysis. The expression of the related proteins was examined with Western blotting analysis. Results: Both chamaejasmenin B and neochamaejasmin C exerted potent anti-proliferative effects in the 8 human solid tumor cell lines. Chamaejasmenin B (the IC50 values ranged from 1.08 to 10.8 μmol/L) was slightly more potent than neochamaejasmin C (the IC50 values ranged from 3.07 to 15.97 μmol/L). In the most sensitive A549 and KHOS cells, the mechanisms underlying the anti-proliferative effects were characterized. The two compounds induced prominent expression of the DNA damage marker γ-H2AX as well as apoptosis. Furthermore, treatment of the cells with the two compounds caused prominent G0/G1 phase arrest. Conclusion: Chamaejasmenin B and neochamaejasmin C are potential anti-proliferative agents in 8 human solid tumor cell lines in vitro via inducing cell cycle arrest, apoptosis and DNA damage.
    Preview · Article · Dec 2012 · Acta Pharmacologica Sinica
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    Full-text · Chapter · May 2013
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