Glutathione-S-transferase-pi expression regulates sensitivity to glutathione-doxorubicin conjugate.
We have reported that glutathione-doxorubicin conjugate (GSH-DXR) exhibited potent cytotoxicity against tumor cells and inhibited glutathione-S-transferase (GST) enzyme activity. In order to determine whether or not the expression of GST-pi lowered the cytotoxicity of GSH-DXR, cytocidal activity of the conjugate was examined using tumor cells in which the level of GST-pi expression was regulated by transfecting GST-pi cDNA in the correct or reverse direction and comparing with that of DXR. Enhancement of GST-pi expression by transfecting GST-pi sense cDNA into human hepatoblastoma HepG2 cells in which GST-pi expression was extremely low caused an increase in GST activity from 0.26 to 55.0 nmol/mg/min and a marked reduction in transfectant sensitivity to GSH-DXR to 1/120 (0.15-18 nM IC50) although the sensitivity to DXR was slightly decreased to 1/2.6 (380-990 nM IC50). By contrast, a high GST-pi-expressing human colon cancer cell line, HT29, showed a decrease in GST enzyme activity from 72.0 to 45.9 nmol/mg/min after transfecting GST-pi antisense cDNA and a marked improvement in transfectant sensitivity to GSH-DXR was observed (28-2.9 nM IC50) compared with the transfectant sensitivity to DXR (1020-320 nM IC50). Additionally, the expression of GST-pi in HepG2 cells caused a decrease in GSH-DXR-induced activation of caspase-3, which was an apoptotic marker, whereas the suppression of GST-pi in HT29 cells showed an increase in caspase-3 activation. These results suggested that the cytocidal efficacy of GSH-DXR, but not that of DXR, was controlled by the level of GST-pi expression in the cells.
Tashiro
K
K
Department of Biochemistry (I), Jikei University School of Medicine, Tokyo 105-8461, Japan.
Asakura
T
T
Fujiwara
C
C
Ohkawa
K
K
Ishibashi
Y
Y
D000970:Antineoplastic Agents / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects; D018076:DNA, Complementary / Q000032:analysis; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology*; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D019073:HT29 Cells / Q000187:drug effects* / Q000201:enzymology; D018197:Hepatoblastoma / Q000201:enzymology / Q000628:therapy; D006801:Humans; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000201:enzymology; D014162:Transfection; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D018076:DNA, Complementary; D007527:Isoenzymes; C436625:glutathione-doxorubicin conjugate; D004317:Doxorubicin; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D005978:Glutathione