Apoptosis induced, in vitro and in vivo, on colon tumor cells from rat after sodium butyrate treatment.

Sodium butyrate (NaB) is known to induce the process of cell differentiation, particularly for epithelial colonic cells. We previously observed that treatment with NaB in association with interleukine 2 (IL2), cures 60% of peritoneal carcinomatosis induced by injection of DHDK12/TRb cells in syngenic rats [15]. In the present work, we evidenced in vitro metabolic alterations of the DHDK12/TRb cell line treated with NaB, followed by an apoptotic process. Flow cytometric analysis evidenced that the tumour cells were arrested in the G1 and G2 phases of the cell cycle for the adherent cells to the plastic. Biological analysis of cells and debris released in the culture medium were essentially apoptotic cells. Complementary, the NaB-induced apoptotic process was confirmed by the staining of the nucleus from releasing cells by Hoechst 33258 and the DNA fragmentation revealed by DNA electrophoresis. Mitochondrial activity and glucose consumption were significantly stimulated after NaB treatment which reveal an alteration of the metabolic activity of the treated tumour cells. As a consequence, we measured a significant increase of the active TGF beta 1 production, a cytokine previously described to participate to the epithelial cell differentiation. These in vitro data were confirmed in vivo showing a significant expression of apoptotic tumour cells in NaB- or NaB/IL2-treated tumours. Thus, the present results in the rat peritoneal carcinomatosis treatment show that combination of apoptotic process induced by NaB with immunostimulation by IL2 has powerful therapeutic properties.