Resistant L1210 Research Articles

Alterations in [ 3H]thymidine incorporation into DNA and [ 3H]uridine incorporation into RNA induced by 5-azacytidine in vivo

Administration in vivo of 5-azacytidine (5-aza-CR) caused suppression of [ 3H]thymidine ([ 3H]TdR) incorporation into DNA of bone marrow and gastrointestinal mucosa of mice and a more prolonged suppression of L1210 ascites tumor. Single doses of 5-aza-CR caused a modest and short-lived suppression of incorporation of [ 3H]uridine ([ 3H]UR) into nuclear RNA of L1210 ascites tumor cells. No suppression of [ 3H]UR incorporation into RNA of bone marrow or gastrointestinal mucosa was observed. L1210 tumor cells resistant to the other active cytidine analogue, cytosine arabinoside, demonstrated less disruption of [ 3H]TdR incorporation after exposure to 5-aza-CR, suggesting some cross resistance in the effects of these two drugs on DNA synthesis. Survival studies carried out in mice bearing both the sensitive and resistant L1210 tumor cell lines confirmed cross resistance of the anti-tumor effects of the two cytidine analogues. Second doses of 5-aza-CR, with the timing og administration based upon the differing patterns of recovery of [ 3H]TdR incorporation between normal tissues and tumor cells, led to a prolongation of survival in mice bearing the sensitive L1210 ascites tumor.

Uptake and intracellular distribution of 4,4′-diacetyldiphenylurea-bis-(guanylhydrazone) in sensitive and resistant leukemia L1210 cells

The uptake and intracellular distribution of 4, 4′-diacetyldiphenylurea-bis(guanylhydrazone) has been studied in vitro and in vivo using cells from leukemia L1210 and a subline resistant to the drug. The uptake process involved a very rapid adsorption, presumably to the cell exterior, followed by actual cellular uptake and firm binding of the drug to the cell. Both adsorption and binding occurred concurrently, although within the first few minutes adsorption predominated. The uptake exhibited first-order kinetics over a 10,000-fold range of external drug concentration with a k 37 of about 0·5 min −1 and a Q 10 of about 2·0. The intracellular-free drug concentration was found to be nearly equal to the extracellular drug concentration. Uptake was not decreased in the presence of sodium para-chloromercuribenzoate, 2, 4-dinitrophenol, of 4, 4'-diacetyldiphenylurea-mono(guanylhydrazone), or when cells were incubated in Ringer solution without calcium and glucose or killed by X-radiation. These findings support the conclusion that 4,4'-diacetyldiphenylurea-bis(guanylhydrazone) is taken up by passive diffusion. In resistant L1210 cells, the different parameters of uptake studied were uniformly 30–50 per cent lower than those found in sensitive L1210 cells; also in this case the intracellular-free drug concentration was nearly the same as the extracellular concentration. A large proportion of the drug taken up was bound to mitochondrial and nuclear fractions. The cellular uptake appeared to be rate-limited by binding or uptake within cellular compartments. The reduced rate of uptake in resistant L1210 was consistent with resistance and appeared to be related to alterations in the binding capacity of cellular organelles.

In vivo effects of methotrexate. Inhibition of DNA synthesis and cell death in sensitive and resistant L1210 ascites populations.

The effect of methotrexate on 125I-iododeoxy-uridine (125IUDR) incorporation into the DNA of L1210 and L1210/MTX ascites cells was determined at different stages of tumor development. Methotrexate administration to drug sensitive L1210 cells during the early phases of tumor growth invariably produced a dramatic decline in precursor utilization. In advanced L1210 ascites populations small drug doses (1 mg/kg) increased 125IUDR incorporation to about twice the control value, while larger doses (10 mg/kg or more) decreased uptake to less than half the original value. Log phase populations of drug resistant L1210/MTX cells resembled terminal L1210 ascites cells in that precursor uptake was enhanced by small amounts of drug and decreased by larger amounts. During the terminal phase of L1210/MTX development all drug levels up to 100 mg/kg produced an increase in 125IUDR incorporation. In parallel studies an attempt was made to correlate the in vivo perturbations of the DNA precursor metabolism to the lethal action of the drug. In terms of cell killing, L1210/MTX cells proved completely resistant to the action of methotrexate, while peritoneal L1210 cells remained fully sensitive throughout the course of ascites growth. Thus, although the results indicated some overall correlation between drug induced inhibition of DNA synthesis and subsequent cell death, the relationship between these 2 parameters would appear to be too complex and ambiguous to be used as a technique for predicting the chemotherapeutic effectiveness of the drug.

Some inhibitory properties of 6-N-Hydroxylaminopurine: An analog of adenine and hypoxanthine

6-N-Hydroxylaminopurine (HAP) prolonged the survival time of mice bearing sarcoma 180 ascites cells; several other ascitic neoplasms were less sensitive to this agent. The rate of incorporation of 2- 14C-glycine into both polynucleotide adenine and guanine of sarcoma 180 was depressed 90% or more by treatment with HAP, and the utilization of 8- 14C-hypoxanthine and 8- 14C-adenine for nucleotide formation was decreased by approximately 85% and 50% respectively. HAP competitively inhibited the formation of adenylic acid from adenine in cell-free extracts of sarcoma 180; the inhibition of inosinic acid formation from hypoxanthine by this analog was complex, being only partially competitive. Dialyzed extracts of either sarcoma 180 or of a variant resistant to purine analogs formed nucleotide from HAP at similar rates, whereas extracts of the L1210 lymphoma formed 5.6-fold more HAP-nucleotide than did those from a 6-mercaptopurine-resistant subline. The extracts from drug-sensitive and -resistant L1210 cells converted adenine to the nucleotide level at equal rates ; only the susceptible neoplasm converted guanine to guanylic acid at a significant rate. In cultured 14L5178Y lymphoblasts, capable of synthesizing purine nucleotides de novo, both hypoxanthine and adenine prevented inhibition of cell reproduction by HAP; on a molar basis adenine was the more effective. In amethopterin-treated L5178Y cells, high levels of HAP supported cell growth in the presence of thymidine and serine. The results suggest that HAP may function as both an antagonist of adenine and hypoxanthine in mammalian cells. Furthermore, the inhibition of cell reproduction caused by this compound appears to be attributable to interference with the biosynthesis of purine nucleotides.

Treatment of localized inoperable neoplasms with intra-arterial infusions of 8-azaguanine.

Treatment of localized inoperable neoplasms with intra-arterial infusions of 8-azaguanine.

Effect of 6-Mercaptopurine on the Net in vitro Gas Production of Sensitive and Resistant L1210 Mouse Leukæmia Cells

Effect of 6-Mercaptopurine on the Net in vitro Gas Production of Sensitive and Resistant L1210 Mouse Leukaemia Cells