Melphalan-resistant lymphoblastoid cell lines established from patients with ovarian cancer treated with cross-linking agents

Products from alkylation of DNA in cells by melphalan: human soft tissue sarcoma cell line RD and Escherichia coli WP2

Alkylation of DNA was studied after treatment with [3H]melphalan (phenylalanine mustard; 1-2 microM) using a human tumour cell line, RD, in culture, or Escherichia coli (WP2 or WP2-uvrA strains) in growth medium. After 6 h at 37 degrees C, treated cells were isolated and re-suspended in fresh growth media. Samples were taken at times up to 48 h for isolation of DNA, and in some cases also RNA and protein (which were found to be alkylated to about the same extent as DNA). Alkylated DNA was analysed as previously described (M.R. Osborne and P.D. Lawley, Chem.-Biol. Interact 89 (1993) 49-60). The four principal products, mono-7-alkylguanine (G-M-OH); mono-3-alkyladenine (A-M-OH); and the cross-linked products G-M-G and A-M-G, were identified in DNA from melphalan treated cells, and quantitatively determined. In each case, alkylation of cellular macromolecules was maximal after about 6 h. In DNA of the human tumour cell line, the relative amounts of adenine products decreased with time, most markedly with A-M-OH to 42% of the 2-h value after 48 h. In DNA of both bacterial strains, A-M-OH was virtually undetectable even at early times. Comparisons between the time course of relative decreases in amounts of these alkylpurine products and the corresponding values for alkylated DNA in vitro suggest that the adenine products are subject to removal by repair enzyme action in E. coli of either strain.

Solasodine glycosides. In vitro preferential cytotoxicity for human cancer cells

Solamargine [(22R,25R)-spiro-5-en-3 beta-yl-alpha-L-rhamnopyranosyl- (1----2glu)-O-alpha-L-rhamnopyranozyl (1----4glu)-beta-D-glucopyranoze], a glycoside of solasodine preferentially inhibits the uptake of tritiated thymidine by cancer cells. In contrast, solamargine at equivalent concentration, and the mono- and diglycosides of solasodine have a limited effect on the uptake of tritiated thymidine for other cell types, including unstimulated lymphocytes and lymphocytes stimulated with Con A. In contrast the solasodine glycosides do not inhibit the uptake of tritiated thymidine by lymphocytes stimulated with PHA or PWM. The inhibition of tritiated thymidine uptake by solamargine and the mono- and di-glycosides of solasodine are dependent upon their cellular uptake by endogenous endocytic lectins (EELs). The mode of action of the solasodine glycosides, in particular solamargine, appears to be the induction of cell lysis, as determined by morphological examination.

Development of alkylating agent-resistant human tumor cell lines

Survival curves and dose escalation studies of four representative human tumor cell lines exposed to the various alkylating agents are presented. With HN2, at a level of one log of cell kill there was a fivefold range in drug concentration required to achieve this degree of cell kill among the cell lines, from 4.5 microM for the SL6 lung adenocarcinoma to 22 microM for the SW2 small-cell lung carcinoma. Four logs of SCC-25 squamous carcinoma cells were killed by 100 microM CDDP; however, there was only about one log of SL6 cells killed by 500 microM CDDP. To kill one log of G3361 melanoma cells required 24 microM 4-HC and to kill one log of SCC-25 cells required 24 microM, approximately a 16-fold difference. The curves for cell kill by L-PAM appeared to be biphasic, with a break at about 100 microM. There was about a threefold range in drug concentration required to achieve one log of cell kill with L-PAM, from 60 microM in the SCC-25 cell line to 18 microM in the SW2 line. To kill one log of SCC-25 cells required 295 microM BCNU and to kill one log of SW2 cell required 120 microM, about a 2.5-fold difference. The range of maximally tolerated HN2 concentrations were from 1200 microM for the SL6 cell line, 48 times the initial concentration, to 300 microM for the SCC-25 line, 16 times the initial concentration. The G3361 line tolerated the highest level of CDDP, 1900 microM, 48 times the initial concentration. The SCC-25 line, on the other hand, tolerated only 600 microM, 30 times the initial concentration. The SL6 cell line maximally tolerated 36 times the initial concentration of 4-HC (1450 microM), whereas the SCC-25 cell line tolerated only 18 times the initial concentration (720 microM). The G3361 melanoma tolerated 1555 microM, 30 times the initial concentration of L-PAM, and the SCC-25 cell line tolerated 700 microM, 14 times the initial concentration. The SL6 cell line tolerated the highest concentration of BCNU, 4200 microM, 24 times the initial concentration. The SCC-25 cell line tolerated 1450 microM, 8 times the initial concentration. In all cases, the SCC-25 cell line was least able to tolerate exposure to increasing concentrations of alkylating agents. The SL6 and G3361 cell lines showed the greatest tolerance for increasing concentrations of alkylating agents.(ABSTRACT TRUNCATED AT 400 WORDS)