Abstract 1159: Hexamethylene bisacetamide (HMBA) inhibits the induction of alkaline phosphatase by butyrate in some bladder and colon cancer cell lines

Abstract

Abstract Induction of alkaline phosphatase in colon cancer cells by inhibitors of histone deacetylase activity has been widely used to monitor the induction of differentiation. We have previously identified three human bladder cancer cell lines in which alkaline phosphatase activity can be induced by inhibitors of histone deacetylase (5637, HT1197 and HT1376 cells). In earlier work it was observed that some bromodomain inhibitors inhibit growth and induction of alkaline phosphatase in these cells. After a recent report that HMBA acts as a bromodomain inhibitor, the effects of HMBA on growth and induction of alkaline phosphatase were investigated in two colon cancer cell lines (Caco-2 and HT29) and in 5637, HT1197 and HT1376 bladder cancer cells. Growth was monitored by staining with sulforhodamine B. Incubation with 2 mM butyrate for 72 hours caused induction of alkaline phosphatase in the five cell lines. In some cell lines there was inhibition of growth and of the induction of alkaline phosphatase activity by 2 mM HMBA. Increasing the HMBA concentration to 5 mM caused significant growth inhibition in all five cell lines and significant inhibition of induction of alkaline phosphatase activity by 2 mM butyrate in the 5637, Caco-2 and HT1376 cells, whether expressed as total activity or activity per unit protein. Although the effect of HMBA on induction of alkaline phosphatase in HT29 cells was not statistically significant there is evidence in the literature for inhibition with longer incubation times. The most marked effects on enzyme induction were seen with the HT1376 bladder cancer cells and this distinction was in line with previous studies on the combined effects of butyrate and the well-established bromodomain inhibitor, JQ1. HMBA has been found by several investigators to be an effective inducer of differentiation in erythroleukemia cells as judged by hemoglobin production. The lack of induction of alkaline phosphatase by HMBA as a single agent in any of the cell lines investigated in the present work suggests that different mechanisms of induction of differentiation operate in erythroleukemia cells than in bladder and colon cancer cells. Citation Format: Michael A. Lea. Hexamethylene bisacetamide (HMBA) inhibits the induction of alkaline phosphatase by butyrate in some bladder and colon cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1159.