Differential Activity of Vincristine and Vinblastine Against Cultured Cells1 ;
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[CANCER RESEARCH 44, 3307-3312, August 1984] Differential Activity of Vincristine and Vinblastine against Cultured Cells1 ; Peter J. Ferguson,2 J. Robert Phillips, Milada Seiner, and Carol E. Cass3 Cancer Research Group (McEachern Laboratory) [P. J. F., J. Ft. P., M. S., C. E. C.] and Department of Biochemistry [P. J. F., C. E. C.¡,University of Alberta, Edmonton, Alberta, Canada T6G 2H7 ABSTRACT determine if differential activity is related to differences in uptake4 or release of drug. Included were cells from these established Vincristine and vinblastine exhibit differential activity against lines: mouse neuroblastoma; mouse leukemia L1210; mouse tumors and normal tissues. In this work, a number of cultured lymphoma S49; HeLa; and human promyelocytic leukemia HL- cell lines were assayed for their sensitivity to the antiproliferative 60. Drug sensitivity in each cell line was determined by assaying and cytotoxic effects of the two drugs following short-term (4 hr) inhibition of proliferation during a continuous exposure to either or during continuous exposures. Differential activity was not drug or by assaying colony formation following a 24-hr exposure. seen when cells were subjected to continuous exposures. The Because of rapid loss of Vinca alkaloids from human serum concentrations of Vincristine and vinblastine, respectively, that following an i.v. bolus injection (11, 12,14, 17), the sensitivity of inhibited growth rates by 50% were: mouse leukemia L1210 cells to short-term (1- and 4-hr) exposures was also determined cells, 4.4 and 4.0 nw; mouse lymphoma S49 cells, 5 and 3.5 nM; for both drugs. Although there were differences in sensitivity to mouse neuroblastoma cells, 33 and 15 nw; HeLa cells, 1.4 and vincristine and vinblastine between cell lines, there was little or 2.6 nw; and human leukemia HL-60 cells, 4.1 and 5.3 nM. In no difference in sensitivity to the 2 drugs within a given cell line contrast, differential toxicity was seen when cells were subjected during continuous exposures. In contrast, after exposures of 4 to 4-hr exposures and transferred to drug-free medium: the 50% hr or less, L1210 and HL-60 cells were much more sensitive to growth-inhibitory concentrations for Vincristine and vinblastine, vincristine than to vinblastine. Experiments were undertaken to respectively, for inhibition (a) of proliferation of L1210 cells were determine if the difference in sensitivity of L1210 cells to vincris 100 and 380 nM and of HL-60 cells were 23 and 900 nM and (b) tine and vinblastine after short exposures was due to differences of colony formation of L1210 cells were 6 and >600 nM and of HeLa cells were 33 and 62 nM. Uptake and release of [3H]- in uptake and/or release of the drugs by cells. Others have vincristine and [3H]vinblastine were examined in L1210 cells observed that vinblastine associates with and is released more quickly from rat platelets than vincristine (8). Radiolabeled vin under the conditions of growth experiments. Uptake of both cristine and vinblastine were utilized in assaying uptake and drugs was dependent on the pH of culture media, and signifi release of drugs from the cells during and following 4-hr expo cantly greater amounts of [3H]vinblastine than of [3H]vincristine sures. The results obtained suggest that rapid release of vin were associated with cells after 4-hr exposures to equal concen blastine by cells is the reason for its lesser toxicity, compared trations of either drug. When cells were transferred to drug-free with vincristine, after 1- or 4-hr exposures. medium after 4-hr exposures, vinblastine was released much more rapidly from cells than was Vincristine, and by 0.5 hr after MATERIALS AND METHODS resuspension of cells, the amount of Vincristine associated with the cells was greater than the amount of vinblastine and remained Cell Culture so for up to at least 6 hr. Unless otherwise noted, stock cultures of the cell lines described below were restarted after 30 to 40 subculture generations from frozen INTRODUCTION cells that had been demonstrated to be free of Mycoplasma (Dr. J. Robertson, Medical Bacteriology, University of Alberta). Stock cultures Vincristine and vinblastine are potent mitotic inhibitors that were routinely maintainedin antibiotic-freegrowth medium of the appro have been used clinically in the treatment of a variety of neo priate type and were expanded in antibiotic-containingmedium(penicillin, plasms. Although they differ in their molecular structure by only 100 units/ml; streptomycin, 100 ¿/g/ml;and,in some cases, gentamycin, 50 Mg/ml)to obtain cells for experimental use. All cultures were grown one carbonyl group, vinblastine and Vincristine exhibit quite at 37°in5% CO2in air, and cell numbers were determined by enumer different spectra of activity in both their targets of antitumor activity and their sites of dose-limiting toxicity. The major sites ation with an electronic particle counter (Coulter Electronics, Hialeah, FL). of toxicity for Vincristine and vinblastine, respectively, are the L1210 Cells.TheoriginandcharacteristicsofmouseleukemiaL1210/ nervous system and the hematopoietic system (1). C2 cells have been described (2). Stock cultures were routinely main The objectives of the current study were to identify cell types tained in Fischer's medium with 10% horse serum, and 5 mw HEPES5 that differ in their sensitivity to Vincristine and vinblastine and to and antibiotics were added to the growth medium of experimental cultures. Cells grew exponentially with doubling times of 14 to 16 hr. ' Supported by the National Cancer Institute of Canada and the Alberta Heritage Savings Trust Fund: Applied Research—Cancer. Portions of this work were ' Uptake refers to total cell-associated drug and may include drug adsorbed to presented in a preliminary report (7). cell surfaces as well as internalized drug. 2 Recipient of a Studentship Award from the Alberta Heritage Foundation for 5 The abbreviations used are: HEPES, A/-2-hydroxyethylpiperazine-W'-2-eth- Medical Research. anesulfonate; \CM. concentration of drug that inhibited proliferation rates by 50% 3 To whom requests for reprints should be addressed. over the period of time specified in text; IQ»,concentration of drug that gave 10% Received August 22, 1983; accepted May 8, 1984. survival. AUGUST1984 3307 Downloaded from cancerres.aacrjournals.org on September 26, 2021. © 1984 American Association for Cancer Research. P. J. Ferguson et al. The effects of drugs on proliferation and viability of L1210/C2 cells after single cells was obtained, and counting with an electronic particle coun 4- or 24-hr exposures were determined as described previously (2). ter. S49 Cells. Mouse lymphoma S49 cells were provided by Dr. D. W. Martin, Jr., University of California, San Francisco, CA, and were main Uptake and Release of Wnca Alkaloids tained in the same manner as L1210 cells. Drug effects on cell prolifer Uptake of [3H]vinblastine and [3H]vincristine by L1210 cells was mea ation were also determined as described for L1210 cells (2). Cells grew exponentially with doubling times of about 15 hr. sured by a modification of a procedure described previously for use in studies of uptake of 3H-nucleosides by suspended cells (9). Solutions HL-60 Cells. Human promyelocytic leukemia HL-60 cells (6) were a containing 3H-labeled drug at twice the concentration to be tested were generous gift from Dr. R. Gallo, NIH, Bethesda, MD. Growth medium prepared in Fischer's growth medium with 10% horse serum and 5 mw consisted of Roswell Park Memorial Institute Medium 1640 supple mented with 15% fetal calf serum. Stock cultures were subcultured 3 or HEPES (pH 7.4). Uptake experiments were initiated by combining equal more times per week by diluting cells to 105/ml. Such cells grew expo volumes of logarithmically growing cells (3 x 10s cells/ml) and the 3H- drug solution and incubating at 37°.At graded time intervals, duplicate nentially with doubling times of about 36 hr. Drug effects on proliferation of HL-60 cells were determined by a modification of the procedure 1-ml samples of the reaction mixtures were transferred to 1,5-ml poly propylene microcentrifuge tubes and centrifuged 1 min in a microcentri- described previously (2) for L1210 cells. Drug exposures were initiated by combining suspensions of exponentially proliferating cells (2 x 105 fuge. The supematants were aspirated, and the cell pellets were washed cells/ml) with equal volumes of fresh growth medium containing drug at by resuspending in 1 ml of cold 0.15 M NaCI solution and centrifuging. The 3H content of cell pellets was determined by removing the superna twice the concentration to be tested. Duplicate cultures were prepared tant and solubilizing the pellet in 100 >i\of 1% Triton X-100 (v/v). Tubes for each drug concentration. For exposures of 4 hr, cells were removed from the drug solution by centrifugation, washed, and resuspended in were uncapped, placed in plastic scintillation vials, and filled with 8 ml of the original volume of drug-free growth medium. Cell recovery was about a xylene:detergent scintillant (16) for determination of radioactivity by 85 to 90% for all cultures including controls. liquid scintillation counting. In some experiments, the water content of cell pellets and the intra- and extracellular water spaces were determined HeLa Cells. Maintenance of stock cultures of HeLa S3 cells and by measuring uptake of [3H]sucrose or 3H2O as described previously (9). expansion of cells for experimental use were carried out as described previously (3). In suspension cultures, cell concentrations were main The number of cells in reaction mixtures was determined by processing tained below 5 x 105 cells/ml, and cell proliferation was exponential with additional samples at each time point as described above, except that doubling times of about 20 hr.