Mol Pharmacol 2000 Jul;58(1):167-74
Cellular response to a glutathione S-transferase P1-1 activated prodrug.
Rosario LA, O'Brien ML, Henderson CJ, Wolf CR, Tew KD
Department of Pharmacology, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
TER286 [gamma-glutamyl-alpha-amino-beta(2-ethyl-N,N,N',
N'-tetrakis(2-chloroethyl)phosphorodiamidate)-sulfonyl-propionyl-( R)- (-) phenylglycine] is a
novel nitrogen mustard prodrug that is preferentially activated by glutathione S-transferase P1-1
(GSTP1-1). A human promyelocytic leukemia /TER286-resistant cell line was selected by
chronic, long-term exposure to the prodrug. Although resistance was not readily achieved,
eventually a 5-fold resistant clone was isolated. Cross-resistance to melphalan occurred, but not
to doxorubicin (Adriamycin), taxol, and gamma-glutamyl-S-(benzyl)cysteinyl-R(-)-phenyl glycine
diethyl ester, a GSTP1-1 inhibitor. The protein and transcript levels and enzymatic activity of
GSTP1-1 were reduced significantly in the selected resistant line. GSTalpha levels were
unchanged, and GSTmu was undetectable. Although glutathione levels were elevated in human
promyelocytic leukemia/TER286 cells, no changes in the expression of thiol-related genes
including gamma-glutamylcysteine synthetase, gamma-glutamyl transpeptidase, or multidrug
resistance protein were found. A 7-fold increase in catalase expression in the resistant cell line
indicated an adaptive response to oxidative and electrophilic stress, and this was also reflected in
the lower prevalence of drug-induced DNA single-strand breaks in the resistant cells. Mouse
embryo fibroblast GSTP1-1(-/-) cells exhibited 2-fold resistance to TER286 compared with
GSTP1-1(+/+) cells. NIH3T3 cells transfected with combinations of gamma-GCS and multidrug
resistance protein exhibited enhanced resistance to TER286, although the degree of resistance
was impaired by cotransfection of GSTP1-1. These results are consistent with responses in the
TER286-resistant cells indicative of GSTP1-1-mediated mechanism of activation. In
consequence, these data support the rationale that tumors expressing high levels of GSTP1-1 will
be more sensitive to the cytotoxic effects of the drug. |
