DNA repair, DNA synthesis and cell cycle delay in human lymphoblastoid cells differentially sensitive to the cytotoxic effects of nitrogen mustard

Mutat Res. Jul-Aug 1984;132(1-2):63-72. doi: 10.1016/0167-8817(84)90067-1.


Two cloned human lymphoblastoid cell lines, Raji and TK6, differ in their sensitivity to the cytotoxic effects of nitrogen mustard (HN2). Raji cells exhibit a biphasic response with an initial D value of 0.06 microgram/ml and a final slope of 0.25 microgram/ml. TK6 cells were considerably more sensitive, D0 value 0.02 microgram/ml. Dose-response relationships for delay in cell cycle progression were measured using flow cytometry. Delay in S-phase traverse was concentration-dependent in both cell lines, and at a given concentration was 2-fold greater in TK6 than in Raji. Numbers of crosslinks (determined by alkaline elution) increased linearly with increasing HN2 concentration and were approximately 2-fold higher in TK6 than in Raji. At equal levels of DNA crosslinks, rates of removal were similar in both cell lines. Inhibition of [3H]TdR uptake was concentration-dependent and the extent of inhibition was similar in both cell lines. Recovery from HN2-induced inhibition of cell cycle progression markedly preceded recovery from inhibition of [3H]TdR incorporation suggesting that nucleotide pools are markedly perturbed in HN2-treated cells. The difference in sensitivity of these two cell lines cannot be adequately explained by differences in amounts of initial DNA damage, rates of repair, differential S-phase delay or rate of loss of DNA crosslinks.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Burkitt Lymphoma
  • Cell Cycle / drug effects
  • Cell Line
  • Cell Survival / drug effects
  • DNA Repair / drug effects*
  • DNA Replication / drug effects*
  • Flow Cytometry
  • Humans
  • Lymphocytes / cytology
  • Mechlorethamine / toxicity*


  • Mechlorethamine