Enhanced cytotoxicity with interleukin-1 alpha and 5-fluorouracil in HCT116 colon cancer cells.
Recombinant human interleukin-1 alpha (rIL-1 alpha), at concentrations that were not growth-inhibitory when given alone (100-10,000 U/ml), enhanced the growth inhibition resulting from a 72-h fluorouracil (FUra) exposure in HCT116 colon cancer cells. Median-effect analysis of clonogenic assays indicated that rIL-1 alpha, given 24 h prior to and following a 24-h exposure to FUra, increased lethality in a more than additive fashion. rIL-1 alpha did not appear to significantly affect [3H]-FUra metabolism, total [3H]-FUra-RNA incorporation or RNA retention after drug removal, inhibition of thymidylate synthase, or thymidine triphosphate pool depletion. During continuous exposure to rIL-1 alpha, transient stimulation of RNA and DNA synthesis was observed at 72 h, with a return to normal by 96 h. A 24-h exposure to 10 microM FUra altered the elution profile of newly synthesized DNA as monitored by pH step alkaline elution. An accumulation of lower-MW single-stranded DNA species was noted with FUra compared to control, accompanied by a significantly decreased proportion of DNA retained on the polycarbonate filter: 10% retained vs. 32% for control (P = 0.01). A 48-h exposure to rIL-1 alpha alone did not affect the elution profile of nascent DNA species, nor did it enhance the effects of FUra. Although FUra did not appreciably affect pulse [3H]-uridine incorporation into RNA for the initial 8-24 h of FUra exposure, progressive inhibition of net RNA synthesis was observed thereafter. FUra prevented the stimulatory effect of rIL-1 alpha on RNA synthesis, and net RNA synthesis was significantly inhibited (by 64-79% after 72 and 96 h) with the combination compared to rIL-1 alpha alone. Continuous exposure to 10 microM thymidine did not rescue cells from the lethality of FUra alone or the combination of FUra plus rIL-1 alpha, suggesting that depletion of deoxythymidine triphosphate as a consequence of thymidylate synthase inhibition was not the most important component of FUra toxicity. In contrast, 1 mM uridine provided partial protection against the toxicity of FUra alone or with rIL-1 alpha. Although uridine did not affect FUra metabolism, it decreased FUra-RNA incorporation by 42-60%, presumably as a consequence of the 2-fold expansion of UTP pools. [125I]-rIL-1 alpha binding was nonspecific; with a 24-h exposure, however, internalized [125I]-rIL-1 alpha exceeded cell surface-bound material by 2-fold.(ABSTRACT TRUNCATED AT 250 WORDS)
Geoffroy
F J
FJ
Navy Medical Oncology Branch, National Cancer Institute, Bethesda, MD 20889-5101, USA.
Allegra
C J
CJ
Sinha
B
B
Grem
J L
JL
D001711:Biotransformation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004357:Drug Synergism; D005472:Fluorouracil / Q000378:metabolism / Q000633:toxicity*; D006801:Humans; D007375:Interleukin-1 / Q000633:toxicity*; D011355:Prodrugs / Q000378:metabolism / Q000633:toxicity*; D012334:RNA, Neoplasm / Q000096:biosynthesis; D017472:Receptors, Interleukin-1 / Q000378:metabolism; D011994:Recombinant Proteins / Q000633:toxicity; D013936:Thymidine / Q000494:pharmacology; D013942:Thymine Nucleotides / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D014529:Uridine / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000378:metabolism
D004273:DNA, Neoplasm; D007375:Interleukin-1; D011355:Prodrugs; D012334:RNA, Neoplasm; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins; D013942:Thymine Nucleotides; C024157:thymidine 5'-triphosphate; D005472:Fluorouracil; D014544:Uridine Triphosphate; D013936:Thymidine; D014529:Uridine