Effect of deoxycholic acid on the tumour incidence, distribution, and receptor status of colorectal cancer in the rat model.

It has previously been observed that 25% of human colorectal cancers contain specific receptors to deoxycholic acid (DCA). In the present study, the effect of intrarectal instillation of DCA on tumour number, distribution, size, and DCA receptor status was measured in rats receiving the colorectal carcinogen, azoxymethane. Rats treated with azoxymethane and intrarectal DCA developed significantly more colorectal cancers than rats receiving azoxymethane and intrarectal saline (median 11.5, range 8-17 vs. median 6.0, range 3-9 tumours/rat, respectively, p less than 0.01). This reflected a significantly higher number of tumours in the distal colon of the DCA-treated group (median 8.0, range 5-10 tumours/rat) compared to the saline-treated group (p less than 0.01). In those rats receiving DCA and azoxymethane, 5 of 12 tumours tested were found to be DCA receptor-positive, compared with only 1 of 11 in the saline and azoxymethane group. These results confirm the belief that DCA acts as a tumour promoter, and suggest a possible role for DCA receptors.