TY - JOUR
T1 - Effects of perturbations of pools of deoxyribonucleoside triphosphates on expression of ribonucleotide reductase, a G1/S transition state enzyme, in p53-mutated cells
AU - Wadler, Scott
AU - Horowitz, Robert
AU - Zhang, Hong Yang
AU - Schwartz, Edward L.
N1 - Funding Information:
This work was supported, in part, by Cancer Center Core Grant P30CA1330-21 from the National Cancer Institute. Dr. Horowitz is a recipient of an American Cancer Society Clinical Oncology Fellowship. The authors wish to acknowledge the excellent technical assistance of Dr. David Gephart and Dr. Jie Rao, and wish to thank Dr. Terry Dugan for support of this project.
PY - 1998/5/1
Y1 - 1998/5/1
N2 - Effects of drug treatment with antimetabolites on a human colon cancer cell line, SW480, were studied. Cells were treated with 10 μM of 5- fluorouracil (5FU), an inhibitor of pyrimidine synthesis, or 1000 μM of hydroxyurea (HU), an inhibitor of both purine and pyrimidine syntheses, or the combination. Recombinant α-2a-interferon (IFN), 500 U/mL, also was employed, as this augments the effects of both antimetabolites in vitro and in vivo. The predominant effect of this combination was to block cells in early S phase as measured by 5-bromo-2'-deoxyuridine (BrdUrd) incorporation. By 24 hr, 86% of the cells had accumulated in S phase, but failed to progress to G2/M. This was accompanied by an early, rapid decline in all four deoxyribonucleoside triphosphates (dNTPs) by 38-86% at 4-24 hr. Despite these effects, expression of the G1/S transition state enzyme, ribonucleotide reductase (RR), increased at 24 hr as measured by a 3 to 5-fold increase in mRNA levels for the M2 subunit, in the absence of a measurable effect on protein levels. The rise in levels of RR mRNA and the continued progression of cells into S phase were associated with a synergistic inhibition of cell cycle proliferation resulting from treatment with the three-drug combination. This suggests that in the presence of antimetabolite-induced depletion of dNTPs, SW480 cells, which lack a normal p53 gene, will proceed into S phase, and that this is associated with a rise in expression of the G1/S transition state enzyme, RR. Cells arrested in S phase by a p53-independent mechanism will undergo a synergistic enhancement of cell death.
AB - Effects of drug treatment with antimetabolites on a human colon cancer cell line, SW480, were studied. Cells were treated with 10 μM of 5- fluorouracil (5FU), an inhibitor of pyrimidine synthesis, or 1000 μM of hydroxyurea (HU), an inhibitor of both purine and pyrimidine syntheses, or the combination. Recombinant α-2a-interferon (IFN), 500 U/mL, also was employed, as this augments the effects of both antimetabolites in vitro and in vivo. The predominant effect of this combination was to block cells in early S phase as measured by 5-bromo-2'-deoxyuridine (BrdUrd) incorporation. By 24 hr, 86% of the cells had accumulated in S phase, but failed to progress to G2/M. This was accompanied by an early, rapid decline in all four deoxyribonucleoside triphosphates (dNTPs) by 38-86% at 4-24 hr. Despite these effects, expression of the G1/S transition state enzyme, ribonucleotide reductase (RR), increased at 24 hr as measured by a 3 to 5-fold increase in mRNA levels for the M2 subunit, in the absence of a measurable effect on protein levels. The rise in levels of RR mRNA and the continued progression of cells into S phase were associated with a synergistic inhibition of cell cycle proliferation resulting from treatment with the three-drug combination. This suggests that in the presence of antimetabolite-induced depletion of dNTPs, SW480 cells, which lack a normal p53 gene, will proceed into S phase, and that this is associated with a rise in expression of the G1/S transition state enzyme, RR. Cells arrested in S phase by a p53-independent mechanism will undergo a synergistic enhancement of cell death.
KW - 5- fluorouracil
KW - Cytokinesis
KW - Deoxyribonucleoside triphosphates
KW - Hydroxyurea
KW - Ribonucleotide reductase
KW - p53
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U2 - 10.1016/S0006-2952(97)00641-2
DO - 10.1016/S0006-2952(97)00641-2
M3 - Article
C2 - 10076525
AN - SCOPUS:0032499432
SN - 0006-2952
VL - 55
SP - 1353
EP - 1360
JO - Biochemical Pharmacology
JF - Biochemical Pharmacology
IS - 9
ER -