Correlation of increased acetate binding with alkylating agent resistance in Walker and Yoshida tumor cells

The utilization of acetate is fundamental to numerous cellular processes. At the level of chromatin, histone acetylation is thought to regulate transcription, and acetate is a major source of cellular energy as it is the substrate for the citric acid cycle. The present work investigates the incorporation of [1-14C]sodium acetate in alkylating agent sensitive (WS) and resistant (WR) Walker 256 carcinosarcoma cells. WR bound the labeled acetate four to six times faster than WS cells, as determined by incorporation of [1-14C]sodium acetate into trichloroacetic acid precipitable material. This difference was consistently observed in both nuclear and cytoplasmic fractions of the cells and in cells permeabilized prior to incubation with radioactive acetate. WS and WR cells did not differ from each other in content of either reduced or acetylated CoA. Since adding exogenous CoA-SH to cell lysates did not alter acetate binding or reduce the differences between WS and WR, increased acetylation in WR cells was independent of CoA levels. Using [1-14C]acetyl CoA to label lysolecithin-permeabilized WS and WR cells revealed no difference between the sensitive and resistant lines, in contrast to the 5-fold greater binding of [1-14C]sodium acetate in permeabilized WR cells. This suggests that WR cells formed acetyl CoA more rapidly than did the WS cells from acetate plus endogenous CoA. Chlorambucil treatment (24 hr) did not affect acetylation of nuclear proteins in log phase cells. Finally, 3-fold greater acetylation in a line of Yoshida sarcoma cells that is resistant to alkylating agents, compared to the sensitive line, supported the generality of the phenomenon.