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Modulation of fluorouracil cytotoxicity by interferon-alpha and -gamma
A Ismail1, C J Van Groeningen, A Hardcastle
1National Cancer Institute-Navy Medical Oncology Branch, National Naval Medical Center, Bethesda, Maryland 20889, USA.
Molecular Pharmacology
|March 14, 1998
Summary
Combining interferons (IFN)-alpha and -gamma with fluorouracil (FUra) significantly enhances colon cancer cell death. This triple therapy profoundly inhibits DNA synthesis and causes extensive DNA damage, offering a promising strategy for cancer treatment.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Interferons (IFN)-alpha and -gamma individually enhance fluorouracil (FUra) cytotoxicity in vitro.
- Understanding the combined effects of these agents is crucial for optimizing cancer therapy.
Purpose of the Study:
- To investigate the synergistic effects of FUra combined with IFN-alpha and IFN-gamma in HT29 colon cancer cells.
- To elucidate the molecular mechanisms underlying the enhanced cytotoxicity.
Main Methods:
- Exposure of HT29 cells to IFN-alpha, IFN-gamma, and FUra individually and in combination.
- Assessment of cell growth, colony formation, nucleotide pool levels (FdUMP, dTTP, dATP, dUTP), thymidylate synthase activity, and DNA synthesis and integrity.
Main Results:
- The combination of IFN-alpha + gamma and FUra exhibited additive or supra-additive inhibition of cell growth and colony formation.
- The triple combination led to significant dTTP depletion, increased dATP/dTTP ratio, and reduced thymidylate synthase activity.
- IFN-alpha + gamma attenuated FUra-induced dUTP accumulation.
- The combination profoundly inhibited nascent DNA chain elongation, increased single-strand breaks in nascent DNA, and decreased net DNA synthesis.
- Double-strand breaks were observed in parental DNA with the triple combination.
Conclusions:
- The enhanced cytotoxicity of the triple combination (IFN-alpha + gamma + FUra) is attributed to dTTP depletion, dATP/dTTP imbalance, pronounced DNA synthesis inhibition, and DNA damage.
- This combination therapy presents a potent strategy for colon cancer treatment.