Selective cytotoxicity of haloethylnitrosoureas in a carcinoma cell line resistant to bifunctional nitrogen mustards.
A Walker 256 rat carcinoma cell line (WR) has been shown to be resistant to a broad spectrum of bifunctional nitrogen mustards (NM) in cell culture. The parent cell line (WS) from which the WR cells were selected retains marked sensitivity to this class of drugs. Karyotype analysis showed that the parent WS had a chromosome content which was significantly higher than the WR. A number of chromosome marker bands were also distinguishable, indicative of distinct nuclear structural differences. A lack of collateral resistance to haloethylnitrosoureas was demonstrated for the WR cell line. In some cases the sensitivity of the WR to nitrosoureas was greater than that of WS. In addition, the WR could be sensitized to NM by a concomitant addition of a water-soluble carbamoylating agent, N,N'-bis(trans-4-hydroxycyclohexyl)-N'-nitrosourea, which possessed no intrinsic alkylating activity. Since NM and nitrosoureas differ pharmacologically, mainly by the latter's potential to carbamoylate, this reaction would appear to be critical to the cytotoxic properties of nitrosoureas against WR cells. Heretofore, carbamoylation has been considered of little importance to the antitumor properties of nitrosoureas. Moreover, 1-(4-amino-2-methylpyrimidine-5-yl)-methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) has been reported as possessing only minimal carbamoylating potential, as measured in vitro by a lysine assay. While remaining an accurate assay for the modification of the psi-amino groups of lysine, it is possible that the quantitative lysine assay may not predict the physiological carbamoylating potential of ACNU in the Walker cells, since marked cytotoxicity was achieved in both WR and WS by ACNU.
D000818:Animals; D000970:Antineoplastic Agents; D002279:Carcinoma 256, Walker / Q000503:physiopathology*; D002460:Cell Line; D003114:Colony-Forming Units Assay; D004351:Drug Resistance; D007621:Karyotyping; D009588:Nitrogen Mustard Compounds / Q000494:pharmacology*; D009607:Nitrosourea Compounds / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013329:Structure-Activity Relationship
D000970:Antineoplastic Agents; D009588:Nitrogen Mustard Compounds; D009607:Nitrosourea Compounds