Potentiation of the antitumor activity of 5-fluorouracil in colon carcinoma cells by the combination of interferon and deoxyribonucleosides results from complementary effects on thymidine phosphorylase

Edward L. Schwartz, Nicole Baptiste, Carolyn J. O'Connor, Scott Wadler, Brian A. Otter

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

α-Interferon (IFNα) potentiates the cytotoxicity of 5-fluorouracil (FUra) in vitro, and the combination has clinical efficacy in advanced colorectal cancer. We have reported previously an IFNα-mediated elevation in cellular FdUMP levels accompanied by the stimulation of thymidine phosphorylase (TP) activity in extracts from HT-29 human colon carcinoma cells treated with IFNα. We have now found that this effect of IFNα can be measured in vivo as an increase in thymine incorporation in intact cells. The increase was only 3-fold, however, compared to the 12-fold increase seen in TP activity in cell extracts. This suggested that the cosubstrate for TP, deoxyribose-1-phosphate, was rate limiting in the cells. Since the synthetic pathway of TP can also proceed via a transferase reaction, natural and modified deoxyribonucleosides were tested as deoxyribosyl donors. TP activity was measurable in cell extracts using deoxyinosine as cosubstrate with either thymine or FUra, although activity was only 10% ofthat measured with deoxyribose-1-phosphate. The pyrimidine analogue 5-propynyloxy-2′-deoxyuridine (PO-dUrd) had 15% of the maximal TP activity in cell extracts and also increased thymine incorporation in intact cells 10-fold. Both 2′-deoxyinosine and PO-dUrd potentiated the cytotoxicity of FUra by 8-11-fold. IFNα potentiated the cytotoxicity of FUra by 1.8-fold, and the combination of IFNα and PO-dUrd produced a 25-fold increase in the cytotoxicity of FUra. Neither the corresponding analogue riboside, 5-propynyloxyuridine, nor the analogue base, 5-propynyloxyuracil, had any effect on FUra cytotoxicity. There was a significant correlation between the ability of a nucleoside and/or IFNα combination to increase thymine incorporation and to reduce the 50% inhibitory concentration for FUra. IFNα and PO-dUrd also potentiated the inhibition by FUra of thymidylate synthase activity. These findings suggest that the use of a deoxyribonucleoside to provide the rate limiting cosubstrate would complement the stimulation of TP by IFNα, and together they should further enhance the antitumor activity of FUra.

Original languageEnglish (US)
Pages (from-to)1472-1478
Number of pages7
JournalCancer Research
Volume54
Issue number6
StatePublished - Mar 15 1994

Fingerprint

Thymidine Phosphorylase
Deoxyribonucleosides
Fluorouracil
Interferons
Colon
Carcinoma
Thymine
Cell Extracts
Deoxyribose
Fluorodeoxyuridylate
Phosphates
Thymidylate Synthase
Transferases
Nucleosides
Inhibitory Concentration 50
Colorectal Neoplasms

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Potentiation of the antitumor activity of 5-fluorouracil in colon carcinoma cells by the combination of interferon and deoxyribonucleosides results from complementary effects on thymidine phosphorylase. / Schwartz, Edward L.; Baptiste, Nicole; O'Connor, Carolyn J.; Wadler, Scott; Otter, Brian A.

In: Cancer Research, Vol. 54, No. 6, 15.03.1994, p. 1472-1478.

Research output: Contribution to journalArticle

@article{28802f38c9fc4af9ac0b3b5b1ce5df70,
title = "Potentiation of the antitumor activity of 5-fluorouracil in colon carcinoma cells by the combination of interferon and deoxyribonucleosides results from complementary effects on thymidine phosphorylase",
abstract = "α-Interferon (IFNα) potentiates the cytotoxicity of 5-fluorouracil (FUra) in vitro, and the combination has clinical efficacy in advanced colorectal cancer. We have reported previously an IFNα-mediated elevation in cellular FdUMP levels accompanied by the stimulation of thymidine phosphorylase (TP) activity in extracts from HT-29 human colon carcinoma cells treated with IFNα. We have now found that this effect of IFNα can be measured in vivo as an increase in thymine incorporation in intact cells. The increase was only 3-fold, however, compared to the 12-fold increase seen in TP activity in cell extracts. This suggested that the cosubstrate for TP, deoxyribose-1-phosphate, was rate limiting in the cells. Since the synthetic pathway of TP can also proceed via a transferase reaction, natural and modified deoxyribonucleosides were tested as deoxyribosyl donors. TP activity was measurable in cell extracts using deoxyinosine as cosubstrate with either thymine or FUra, although activity was only 10{\%} ofthat measured with deoxyribose-1-phosphate. The pyrimidine analogue 5-propynyloxy-2′-deoxyuridine (PO-dUrd) had 15{\%} of the maximal TP activity in cell extracts and also increased thymine incorporation in intact cells 10-fold. Both 2′-deoxyinosine and PO-dUrd potentiated the cytotoxicity of FUra by 8-11-fold. IFNα potentiated the cytotoxicity of FUra by 1.8-fold, and the combination of IFNα and PO-dUrd produced a 25-fold increase in the cytotoxicity of FUra. Neither the corresponding analogue riboside, 5-propynyloxyuridine, nor the analogue base, 5-propynyloxyuracil, had any effect on FUra cytotoxicity. There was a significant correlation between the ability of a nucleoside and/or IFNα combination to increase thymine incorporation and to reduce the 50{\%} inhibitory concentration for FUra. IFNα and PO-dUrd also potentiated the inhibition by FUra of thymidylate synthase activity. These findings suggest that the use of a deoxyribonucleoside to provide the rate limiting cosubstrate would complement the stimulation of TP by IFNα, and together they should further enhance the antitumor activity of FUra.",
author = "Schwartz, {Edward L.} and Nicole Baptiste and O'Connor, {Carolyn J.} and Scott Wadler and Otter, {Brian A.}",
year = "1994",
month = "3",
day = "15",
language = "English (US)",
volume = "54",
pages = "1472--1478",
journal = "Cancer Research",
issn = "0008-5472",
publisher = "American Association for Cancer Research Inc.",
number = "6",

}

TY - JOUR

T1 - Potentiation of the antitumor activity of 5-fluorouracil in colon carcinoma cells by the combination of interferon and deoxyribonucleosides results from complementary effects on thymidine phosphorylase

AU - Schwartz, Edward L.

AU - Baptiste, Nicole

AU - O'Connor, Carolyn J.

AU - Wadler, Scott

AU - Otter, Brian A.

PY - 1994/3/15

Y1 - 1994/3/15

N2 - α-Interferon (IFNα) potentiates the cytotoxicity of 5-fluorouracil (FUra) in vitro, and the combination has clinical efficacy in advanced colorectal cancer. We have reported previously an IFNα-mediated elevation in cellular FdUMP levels accompanied by the stimulation of thymidine phosphorylase (TP) activity in extracts from HT-29 human colon carcinoma cells treated with IFNα. We have now found that this effect of IFNα can be measured in vivo as an increase in thymine incorporation in intact cells. The increase was only 3-fold, however, compared to the 12-fold increase seen in TP activity in cell extracts. This suggested that the cosubstrate for TP, deoxyribose-1-phosphate, was rate limiting in the cells. Since the synthetic pathway of TP can also proceed via a transferase reaction, natural and modified deoxyribonucleosides were tested as deoxyribosyl donors. TP activity was measurable in cell extracts using deoxyinosine as cosubstrate with either thymine or FUra, although activity was only 10% ofthat measured with deoxyribose-1-phosphate. The pyrimidine analogue 5-propynyloxy-2′-deoxyuridine (PO-dUrd) had 15% of the maximal TP activity in cell extracts and also increased thymine incorporation in intact cells 10-fold. Both 2′-deoxyinosine and PO-dUrd potentiated the cytotoxicity of FUra by 8-11-fold. IFNα potentiated the cytotoxicity of FUra by 1.8-fold, and the combination of IFNα and PO-dUrd produced a 25-fold increase in the cytotoxicity of FUra. Neither the corresponding analogue riboside, 5-propynyloxyuridine, nor the analogue base, 5-propynyloxyuracil, had any effect on FUra cytotoxicity. There was a significant correlation between the ability of a nucleoside and/or IFNα combination to increase thymine incorporation and to reduce the 50% inhibitory concentration for FUra. IFNα and PO-dUrd also potentiated the inhibition by FUra of thymidylate synthase activity. These findings suggest that the use of a deoxyribonucleoside to provide the rate limiting cosubstrate would complement the stimulation of TP by IFNα, and together they should further enhance the antitumor activity of FUra.

AB - α-Interferon (IFNα) potentiates the cytotoxicity of 5-fluorouracil (FUra) in vitro, and the combination has clinical efficacy in advanced colorectal cancer. We have reported previously an IFNα-mediated elevation in cellular FdUMP levels accompanied by the stimulation of thymidine phosphorylase (TP) activity in extracts from HT-29 human colon carcinoma cells treated with IFNα. We have now found that this effect of IFNα can be measured in vivo as an increase in thymine incorporation in intact cells. The increase was only 3-fold, however, compared to the 12-fold increase seen in TP activity in cell extracts. This suggested that the cosubstrate for TP, deoxyribose-1-phosphate, was rate limiting in the cells. Since the synthetic pathway of TP can also proceed via a transferase reaction, natural and modified deoxyribonucleosides were tested as deoxyribosyl donors. TP activity was measurable in cell extracts using deoxyinosine as cosubstrate with either thymine or FUra, although activity was only 10% ofthat measured with deoxyribose-1-phosphate. The pyrimidine analogue 5-propynyloxy-2′-deoxyuridine (PO-dUrd) had 15% of the maximal TP activity in cell extracts and also increased thymine incorporation in intact cells 10-fold. Both 2′-deoxyinosine and PO-dUrd potentiated the cytotoxicity of FUra by 8-11-fold. IFNα potentiated the cytotoxicity of FUra by 1.8-fold, and the combination of IFNα and PO-dUrd produced a 25-fold increase in the cytotoxicity of FUra. Neither the corresponding analogue riboside, 5-propynyloxyuridine, nor the analogue base, 5-propynyloxyuracil, had any effect on FUra cytotoxicity. There was a significant correlation between the ability of a nucleoside and/or IFNα combination to increase thymine incorporation and to reduce the 50% inhibitory concentration for FUra. IFNα and PO-dUrd also potentiated the inhibition by FUra of thymidylate synthase activity. These findings suggest that the use of a deoxyribonucleoside to provide the rate limiting cosubstrate would complement the stimulation of TP by IFNα, and together they should further enhance the antitumor activity of FUra.

UR - http://www.scopus.com/inward/record.url?scp=0028210793&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0028210793&partnerID=8YFLogxK

M3 - Article

VL - 54

SP - 1472

EP - 1478

JO - Cancer Research

JF - Cancer Research

SN - 0008-5472

IS - 6

ER -