Changes in gene expression profile in two multidrug resistant cell lines derived from a same drug sensitive cell line.

Resistance to chemotherapy is one of the most relevant aspects of treatment failure in cancer. Cell lines are used as models to study resistance. We analyzed the transcriptional profile of two multidrug resistant (MDR) cell lines (Lucena 1 and FEPS) derived from the same drug-sensitive cell K562. Microarray data identified 130 differentially expressed genes (DEG) between K562 vs. Lucena 1, 1932 between K562 vs. FEPS, and 1211 between Lucena 1 versus FEPS. The NOTCH pathway was affected in FEPS with overexpression of NOTCH2 and HEY1. The highly overexpressed gene in MDR cell lines was ABCB1, and both presented the ABCB1 promoter unmethylated.

Characterization of a multidrug-resistant chronic myeloid leukemia cell line presenting multiple resistance mechanisms.

The multidrug-resistant (MDR) phenotype is multifactorial, and cell lines presenting multiple resistance mechanisms might be good models to understand the importance of the various pathways involved. The present work characterized a MDR chronic myeloid leukemia cell line, derived from K562 through a selective process using daunorubicin. This MDR cell line was shown to be resistant to vincristine, daunorubicin, and partially resistant to imatinib. It showed a slower duplication rate. Overexpression of ABCB1 and ABCC1 was observed at the protein and functional levels and the expression of CD95, a molecule related to cell death, was reduced in the MDR cell line. Conversely, no differences were observed related to the anti-apoptotic molecule Bcl-2 or p53 expression. The activation antigen CD69 was reduced in the MDR cell line and treatment with imatinib further decreased the expressed levels. Furthermore, secretion of IL-8 was diminished in the MDR cell line. When daunorubicin-selected cells were compared to another MDR cell line, Lucena 1, derived from the same parental line K562, and selected with vincristine, a different profile was observed in relation to most aspects studied. When both cell lines were silenced for ABCB1, differences in CD69 and CD95 were maintained, despite resistance reversal. These results reinforce the idea that cell lines selected in vitro may display multiple resistance strategies that may vary with the selective agent used as well as during different steps of the selection process.

Effect of extracellular ATP on the human leukaemic cell line K562 and its multidrug counterpart.

Extracellular ATP (ATPo) is capable of inducing different events on cells through receptor activation. The effect produced by ATPo was studied in the cell line K562 and its multidrug resistant (MDR) counterpart, Lucena 1. Lower ATPo concentrations (1 mM and 2.5 mM) led to high (3)H-thymidine incorporation but no increase in cell number. Similarly, the cell cycle profile indicated an increase of cells in S phase and a decrease in G1 and G2, suggesting that the cells did not duplicate their DNA content. Higher doses of ATP (5 mM and 10 mM), as well as UTP (5 mM) and the P2X(7) agonist BzATP, were cytotoxic. However, no expression of P2X(7) receptors could be detected by Western Blot nor were the cells permeabilised by ATP, suggesting that pore formation was not involved in cell death. Both ecto-ATPase and ecto-5'-nucleotidase activity could be demonstrated at the surfaces of K562 and Lucena 1 cells, the latter presenting a higher ecto-5'-nucleotidase activity. Adenosine induced cell death at lower concentrations (2.5 mM) on both cell lines. Furthermore, an increased number of dead cells could be observed when 5 mM Adenosine was used compared to the same concentrations of ATPo. It still remains to be elucidated the nature of the receptors involved in the induction of cell death in these cells.