Determinants of trimetrexate lethality in human colon cancer cells

Jean L Grem, D. M. Voeller, F. Geoffroy, E. Horak, P. G. Johnston, C. J. Allegra

Research output: Contribution to journalArticle

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Abstract

We examined the cytotoxicity and biochemical effects of the lipophilic antifol trimetrexate (TMQ) in two human colon carcinoma cell lines, SNU-C4 and NCI-H630, with different inherent sensitivity to TMQ. While a 24 h exposure to 0.1 μM TMQ inhibited cell growth by 50-60% in both cell lines, it did not reduce clonogenic survival. A 24 h exposure to 1 and 10 μM TMQ produced 42% and 50% lethality in C4 cells, but did not affect H630 cells. Dihydrofolate reductase (DHFR) and thymidylate synthase were quantitatively and qualitatively similar in both lines. During drug exposure, DHFR catalytic activity was inhibited by ≥ 85% in both cell lines; in addition, the reduction in apparent free DHFR binding capacity (≤ 20% of control), depletion of dTTP, ATP and GTP pools and inhibition of [6- 3 H]deoxyuridine incorporation into DNA were similar in C4 and H630 cells. TMQ produced a more striking alteration of the pH step alkaline elution profile of newly synthesised DNA in C4 cells compared with 630 cells, however, indicating greater interference with DNA chain elongation or more extensive DNA damage. When TMQ was removed after a 24 h exposure to 0.1 μM, recovery of DHFR catalytic activity and apparent free DHFR binding sites was evident over the next 24-48 h in both cell lines. With 1 and 10 μM, however, persistent inhibition of DHFR was evident in C4 cells, whereas DHFR recovered in H630 cells. These data suggest that, although DHFR inhibition during TMQ exposure produced growth inhibition, DHFR catalytic activity 48 h after drug removal was a more accurate predictor of lethality in these two cell lines. Several factors appeared to influence the duration of DHFR inhibition after drug removal, including initial TMQ concentration, declining cytosolic TMQ levels after drug removal, the ability to acutely increase total DHFR content and the extent of TMQ-mediated DNA damage. The greater sensitivity of C4 cells to TMQ-associated lethality may be attributed to the greater extent of TMQ-mediated DNA damage and more prolonged duration of DHFR inhibition after drug exposure.

Original languageEnglish (US)
Pages (from-to)1075-1084
Number of pages10
JournalBritish journal of cancer
Volume70
Issue number6
DOIs
StatePublished - Jan 1 1994

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Trimetrexate
Tetrahydrofolate Dehydrogenase
Colonic Neoplasms
Cell Line
DNA Damage
Pharmaceutical Preparations
DNA
Growth
Guanosine Triphosphate

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

Cite this

Grem, J. L., Voeller, D. M., Geoffroy, F., Horak, E., Johnston, P. G., & Allegra, C. J. (1994). Determinants of trimetrexate lethality in human colon cancer cells. British journal of cancer, 70(6), 1075-1084. https://doi.org/10.1038/bjc.1994.451

Determinants of trimetrexate lethality in human colon cancer cells. / Grem, Jean L; Voeller, D. M.; Geoffroy, F.; Horak, E.; Johnston, P. G.; Allegra, C. J.

In: British journal of cancer, Vol. 70, No. 6, 01.01.1994, p. 1075-1084.

Research output: Contribution to journalArticle

Grem, JL, Voeller, DM, Geoffroy, F, Horak, E, Johnston, PG & Allegra, CJ 1994, 'Determinants of trimetrexate lethality in human colon cancer cells', British journal of cancer, vol. 70, no. 6, pp. 1075-1084. https://doi.org/10.1038/bjc.1994.451
Grem JL, Voeller DM, Geoffroy F, Horak E, Johnston PG, Allegra CJ. Determinants of trimetrexate lethality in human colon cancer cells. British journal of cancer. 1994 Jan 1;70(6):1075-1084. https://doi.org/10.1038/bjc.1994.451
Grem, Jean L ; Voeller, D. M. ; Geoffroy, F. ; Horak, E. ; Johnston, P. G. ; Allegra, C. J. / Determinants of trimetrexate lethality in human colon cancer cells. In: British journal of cancer. 1994 ; Vol. 70, No. 6. pp. 1075-1084.
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