Received for publication March 11, 2005.
Revised June 21, 2005.
Accepted for publication June 21, 2005.

Pro-apoptotic effect on normal and tumor intestinal cells of cytostatic drugs with enterohepatic organotropism

Abstract

The pro-apoptotic effect of cisplatin-bile acid derivatives Bamet-R2 and Bamet-UD2, developed to treat liver and intestinal tumors, was investigated in vitro using human enterohepatic cells HepG2 (hepatoblastoma), LS 174T (colon adenocarcinoma), and its cisplatin-resistant sub-line LS 174T/R. Uptake by wild-type tumor cells was higher for Bamets than for cisplatin. In LS 174T/R cells, CTR1 was down-regulated and MRP2 was up-regulated. Consequently, uptake and efflux of cisplatin, but not those of Bamets, were reduced and increased, respectively. The degree of necrosis (LDH release) induced by these three drugs was small and similar in all cell types. In contrast, pro-apoptotic effect (caspase-3 activity and DNA fragmentation) was Bamet-UD2>cisplatin>Bamet-R2 in HepG2 and LS 174T cells, but Bamet-UD2>Bamet-R2>>cisplatin in LS 174T/R cells. This effect was consistent with the ability of these compounds to form DNA-adducts (DNA-platination, changes in the DNA melting temperature and MspI-induced restriction sequence cleavage). Oral administration of Bamet-UD2 to mice induced mild apoptosis in the small intestine (ileum>duodenum), which was not severe enough to modify its structure or function as determined by water absorption and glycocholic acid uptake by in situ perfused ileum. These results indicate that Bamet-UD2 overcomes the resistance to cisplatin when this is due in part to enhanced ability of intestinal tumors to reduce intracellular cisplatin contents. Moreover, its strong pro-apoptotic versus its weak pro-necrotic effect together with its mild effect on normal tissues, including intestinal mucosa, may account for the high anti-tumor activity of Bamet-UD2 together with its very low toxicity.

Key words: Cancer, Chemotherapy, Drug targeting, Intestine, Liver, Transporters