Mechanism of action of arenesulfonylhydrazones of 2-pyridinecarboxaldehyde 1-oxide in L1210 cells

Abstract

The arenesulfonylhydrazones of 2-pyridinecarboxaldehyde 1-oxide represent a relatively new class of anticancer agents. The biochemical alterations responsible for antineoplastic activity were investigated using the most potent member of this class synthesized to date, the 3,4-dimethoxybenzenesulfonylhydrazone of 2-pyridinecarboxaldehyde 1-oxide (3,4-DSP), as the prototype compound. The primary biochemical lesion observed was the production of DNA single-strand breaks, which were analyzed using alkaline elution methodology. This production of DNA damage required the spontaneous chemical formation of a reactive species; thus, "aging" of a solution of 3,4-DSP prior to exposure of L1210 leukemia cells in culture markedly decreased the production of DNA single-strand breaks. The chemical production of an alkylating species from 3,4-DSP has been proposed to occur by the intramolecular abstraction of the nitrogen proton by the 1-oxide group, followed by release of arenesulfinic acid to form the potent alkylating species, 1-oxidopyridin-2-yldiazomethane. Replacement of the proton by a methyl group, lack of the 1-oxide group, or replacement of the aldehyde proton by a methyl group increases the chemical stability of the arenesulfonylhydrazones. These modifications have been shown in a previous publication (D .A. Shiba, J. A. May, Jr., and A. C. Sartorelli, Cancer Res., 43: 2023-2029, 1983) to lead to (a) an elimination of alkylating activity and (b) a decrease in in vitro cytotoxicity and in vivo anticancer activity. These effects are also accompanied by an inability to produce detectable DNA single-strand breaks. 3,4-DSP caused little or no inhibition of the biosyntheses of DNA, RNA, or protein, as measured by the incorporation of radiolabeled thymidine, uridine, or leucine, respectively, into acid-insoluble material; however, consistent with the production of DNA damage, 3,4-DSP inhibited the normal progression of L1210 cells through the cell cycle after a single treatment in vivo with drug (100 mg/kg). Cells were blocked in the G2-M phase of the cell cycle for 6 to 24 hr after exposure to 3,4-DSP; the cell population recovered by 48 hr after exposure and appeared to be progressing normally through the cell cycle.