Non-Protein Sulphydryl Group in the Original Strain and Sub-line of the Ascites Tumour resistant to Alkylating Reagents

Abstract

I HAVE succeeded in establishing resistant variants of the Yoshida ascites sarcoma and ascites hepatoma (AH 13 and AH 7974) to methyl-bis-(β-chlorethyl)-amine N-oxide, one of the alkylating agents, by passing tumour cells through animals treated with the reagents¹. These resistant variants were proved to be cross-resistant to the other alkylating reagents, but not cross-resistant to the unrelated reagents². Furthermore, no difference could be detected in cytological features of tumour cells between the original and resistant sub-lines. Details concerning the biological properties of these resistant sub-lines are to be found in previous papers^1–3. The mechanism of development of resistance to this reagent is not yet clear. However, it is well known that nitrogen mustard inactivates sulphydryl groups. Also a preferential affinity of methyl-bis-(β-chlorethyl)-amine N-oxide to sulphydryl groups has already been reported by Torigoe⁴ and Ishidate⁵. From this point of view, I attempted to study the non-protein sulphydryl content of tumour cells in the original strain and resistant sub-line.