3-7-dihydroxycholestan-26-oic-acid and Hepatoblastoma

We have examined the ability of HepG2 human hepatoblastoma cells and 7800 C1 Morris rat hepatoma cells to convert 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid (THCA) and 3 alpha, 7 alpha-dihydroxy-5 beta-cholestanoic acid (DHCA) to cholic acid and chenodeoxycholic acid, respectively. Cell extracts from both these cell lines could neither form cholic acid from THCA nor from the activated form, THCA-CoA. This suggests that both cell lines are defective in two enzyme activities involved in the pathway, the microsomal THCA-CoA ligase and the peroxisomal THCA-CoA oxidase. Furthermore, we show that the subsequent enzymes are active in the conversion to bile acids, because the product of the THCA-CoA oxidase, 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholest-24-enoyl-coenzyme A (delta 24-THCA-CoA) or delta 24-THCA in the presence of THCA-CoA ligase, are converted to cholic acid by both cell lines. HepG2 cells were able to slowly form chenodeoxycholic acid and cholic acid from 5 beta-cholestane-3 alpha, 7 alpha-diol and 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol, respectively, in 24- and 96-h incubations. The rate of cholic acid formation was lower than the rate for chenodeoxycholic acid and there was a clear accumulation of THCA. 7800 C1 Morris cells had no ability to form cholic acid or chenodeoxycholic acid after 96 h incubation. We conclude that these two cell lines have defects in two enzyme activities involved in the peroxisomal oxidation in bile acid formation, the microsomal THCA-CoA ligase and the peroxisomal THCA-CoA oxidase.

Topics: Animals; Bile Acids and Salts; Chenodeoxycholic Acid; Cholestanols; Cholesterol 7-alpha-Hydroxylase; Cholic Acid; Cholic Acids; Clofibric Acid; Dexamethasone; Fatty Acids; Hepatoblastoma; Humans; Liver Neoplasms; Liver Neoplasms, Experimental; Male; Oxidation-Reduction; Rats; Rats, Wistar; Retinoids; Tumor Cells, Cultured