Endocrine Abstracts

Background: The pro-proliferative and anti-apoptotic IGF-I is implicated in the development of colorectal cancer (CRC) in both the general population and patients with acromegaly. The local intracolonic environment is also likely to be important, particularly unconjugated bile acids such as deoxycholic acid (DCA). Whilst low faecal concentrations may be proliferative, high levels are toxic to colonic epithelial cells.

High levels of DCA have been linked to an increased risk of developing CRC and we have previously shown level to be high in patients with acromegaly.

Aims: To determine the influence of IGF-I on DCA, induced apoptosis in HT29 cells (a human colorectal cancer cell line).

Methods: HT29 cells (initial density 10⁵ cells) were cultured for 48hours in serum free media with or without DCA (400 micromolar) and IGF-I (20 nanogram per mililitre), either separately or together. A colorimetric MTT assay was used to measure cell viability and FACS analysis [annexin and propidium iodide (PI)] were carried out to assess early and late apoptosis respectively. Control cells were incubated in media only. The viability assessment was performed in 12 identical wells and each experiment repeated on three occasions.

Results: MTT assay: mean % viability compared to media only: IGF-I only 235%, DCA 47% and DCA+IGF-I 84%. FACS analysis confirmed a preventive effect of IGF-I on apoptosis, mean % of apoptotic cells: annexin (media only 14.6%, IGF-I 8.7%, DCA only 36% & DCA + IGF-I 19.5 %) and PI (media only 10%, IGF-I only 2.5%, DCA only 71.4% & DCA+IGF-I 33.8 %).

Conclusion: The prevention of DCA-induced apoptosis by IGF-I will lead to increased epithelial cell damage in patients with acromegaly and may account for the increased prevalence of CRC.