tetrodotoxin and Leukemia

To investigate the mechanism of proliferation inhibition and apoptosis of K562 leukemia cells by lithium chloride (LiCl), after K562 cells were treated with LiCl (30 mmol/L) cell cycle was examined by flow cytometry (FCM) and the expression of bcr/abl fusion gene mRNA was evaluated by RT-PCR. The intracellular Li(+) concentrations of K562 cells were determined at different time after treated with 30 mmol/L LiCl and the effects of TTX and FSK on intracellular Li(+) concentrations of K562 cells were also detected by atomic absorption spectrometry. The effects of TTX and FSK on LiCl-induced growth inhibition of K562 cells were determined by cell counting in liquid culture. The results showed that LiCl (30 mmol/L) caused a sustained arrest in G(2)/M cell cycle and down-regulated the bcr/abl mRNA expression in K562 cells, the intracellular Li(+) concentration of K562 cells increased at 30 minutes after treated with 30 mmol/L LiCl and reached apex at 2 hours, thereafter, gradually decreased and balanced at 4 hours after the treatment. If either Na(+) channel was pre-blocked with TTX or K(+) channel was pre-blocked with FSK, the intracellular Li(+) concentrations of K562 cells treated with 30 mmol/L LiCl were higher than that in the cells just treated with LiCl without pre-blocking. Furthermore, after pre-blocking either Na(+) channel with TTX or K(+) channel with FSK, the inhibition rate of K562 cell growth by 30 mmol/L LiCl could be increased. It is concluded that the mechanism of proliferation inhibition and apoptosis of K562 leukemia cells induced by LiCl is probably related with the G(2)/M cell cycle arrest, the bcr/abl mRNA expression down-regulation and the status of Na(+), K(+), or Li(+) ion channels on K562 leukemia cells.

Topics: Antineoplastic Agents; Apoptosis; Cell Cycle; Cell Proliferation; Colforsin; Flow Cytometry; Fusion Proteins, bcr-abl; Gene Expression Regulation, Neoplastic; Humans; K562 Cells; Leukemia; Lithium Chloride; Potassium Channel Blockers; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sodium Channel Blockers; Tetrodotoxin

Membrane currents were examined in a drug-sensitive human leukemia cell line (K562) and its multidrug-resistant cell line (K562/ADM) under the whole-cell variation of the patch electrode voltage clamp technique. Most K562 cells showed only the outward current, which was completely suppressed by internal Cs+ ions and 20 mM ethyleneglycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. In contrast to K562 cells, most K562/ADM cells showed tetrodotoxin-sensitive, voltage-gated Na+ channel current in addition to the outward current. Na+ current was observed in four of 29 K562 cells examined, while it was observed in 29 of 33 K562/ADM cells. Two revertant cell lines (R1-3, R1-5) did not show Na+ current. It was concluded that the amplitude of voltage-gated Na+ current increases in association with multidrug resistance in human leukemia cells.

Topics: Antineoplastic Agents; Cell Line; Doxorubicin; Drug Resistance; Egtazic Acid; Humans; Ion Channels; Leukemia; Mathematics; Membrane Potentials; Sodium; Tetrodotoxin; Vinca Alkaloids