Chromosomal Characterization of Methotrexate-resistant Human T-lymphoblast Leukemia Cells (CCRF-CEM) with Impaired Polyglutamylation

Chromosome studies of murine T-cell lymphoid leukemia and derived cell lines

Several cell lines were previously established from a spontaneous murine T-cell leukemia (LB). The aim of this study was to analyze the G- and C-banded karyotypes of the parental LB tumor cells and the derived cell lines. A sensitive cell line (LBL) from which two sublines originated, as well as Vincristine (LBR-V160) and Doxorubicin (LBR-D160) resistant cell lines, were used. Our results showed that LB cells had a pseudo-diploid karyotype with 40 acrocentric chromosomes in which trisomy of chromosome 14 was the most relevant alteration. The sensitive cell line showed this alteration in all metaphases studied; no changes in karyotypes were observed in either subline, despite their dissimilar morphology and growth patterns. In contrast, both resistant lines displayed a more heterogeneous karyotype with no common markers, except for the finding that chromosome 5 was involved in a trisomy in LBR-V160 and in a translocation with chromosome 12 in LBR-D160. Taking into account that the mdr genes are located in chromosome 5, these results suggest a possible association between such alterations and the acquisition of drug resistance.

The effect of folate on the methotrexate/indomethacin interaction in a murine cancer cell line

1. The effect of folate on the interaction between methotrexate (a folate analogue) and indomethacin has been examined in murine NC carcinoma cells. 2. Conditioning of NC cells to a physiological (20 nM) folate concentration after culture in a high folate concentration increased the response to methotrexate. The sensitivity of these conditioned cells to methotrexate related inversely to the folate concentration. 3. At 20 nM and 2 microM folate, indomethacin 1 micrograms ml-1 potentiated the cytotoxicity of methotrexate 4 and 8 ng ml-1 (both P < 0.03). 4. When NC cells were incubated with [3H]-methotrexate at 20 nM and 2 microM folate, there was a trend for increased tritium accumulation with indomethacin 0.36 micrograms ml-1 (1 microM; P < 0.01). 5. We conclude that the folate concentration can affect the sensitivity of NC cells to methotrexate, although the degree of potentiation of cytotoxicity by indomethacin remains similar.