Action of camptothecin on mammalian cells in culture

L H Li, T J Fraser, E J Olin, B K Bhuyan
1972 Cancer Research  
Camptothecin (CN) is active against several experimental tumors and has also been studied clinically. We report here the effect of CN on LI210 cells and asynchronous and synchronous DON cells in culture. CN was toxic both to LI210 cells (0.06 ¿ig/ml,2-hr exposure) and DON cells (0.15 Mg/ml, 1-hr exposure), and it inhibited DNA and RNA synthesis more than it inhibited protein synthesis. CN was more cytotoxic to DON cells in S phase than cells in GÃOE or G2, although it inhibited DNA and RNA
more » ... ted DNA and RNA synthesis of LI 210 cells and asynchronous DON cells almost equally. When asynchronous DON cells were exposed to CN for 30 min and CN was then removed, RNA synthesis was no longer significantly inhibited, but the inhibition of DNA synthesis persisted. The survival patterns of synchronous DON cells were closely related to DNA synthesis inhibition but not to RNA synthesis inhibition. These results collectively suggested that the marked effect of CN on DNA synthesis appeared to be one of the primary determinants of its cytotoxicity. Since no significant effect was observed on the enzymes involved in DNA synthesis, DNA synthesis inhibition by CN may be in part due to its effect on the DNA template. The interaction between CN and DNA was detected by melting point determinations. CN did not block the progression of mitotic cells into S phase. At 100 Mg/ml, CN prevented the progression of S phase cells into G2 ; at 1 A/g/ml, some cells did leave S and proceeded into G2. Cells in G2 were blocked from moving into mitosis even at 0.01-¿/g/mldoses of CN. Thus, the progression of late S or early G2 cells into mitosis was most sensitive to the drug. MATERIALS AND METHODS Tissue Culture Systems L1210 cells were grown at 37°in basal medium (RPMI 1634 medium3: fetal calf serum, 100:5) developed by Moore et al. (16). A mixture of penicillin (0.1 mg/ml of medium) and streptomycin (50 Mg/ml of medium) was added. Cells used in uptake studies were in the logarithmic phase of growth (ca. 5X 10s cells/ml). DON cells, a Chinese hamster fibroblast line (ATCC No. CCL 16), were grown in McCoy's Medium 5A modified by the addition of lactalbumin hydrolysate (0.8 g/liter) and fetal calf serum (200 ml/liter). The cell monolayer was detached from glass by treatment with a 0.1% trypsin solution. The cells were dispersed and grown in 8-oz bottles planted with about 2X IO6 cells in 25 ml medium. The cells were maintained in the logarithmic growth phase by subculturing every 2 days. Chemicals and Medium
pmid:4674679 fatcat:xokev6gujvbpdi5jlkbqpzfusi