Are Epigenetic Changes in Normal Fibroblasts Imposed by Colonic Cancer Cells? A Preliminary Inquiry

The molecular mechanisms underlying the transformation of normal fibroblasts into cancer-associated fibroblasts promoting the neoplastic process remain elusive. An attractive possibility is that subversive signals from cancer cells alter the epigenomic profile of normal fibroblasts, reprogramming them as partners in crime endowed with a stable pro-tumorigenic phenotype. To test this tenable hypothesis, human colonic fibroblasts (CCD-18Co cell line) and human colonic cancer cells (HT-29 cell line) were co-cultured for 24, 48 and 72 h in a Transwell system preventing direct cell-to-cell contact but allowing brisk paracrine communication. Each cell line cultured separately served as the appropriate control.

At the end of the selected culture time periods genomic DNA was extracted and levels of 5-methyl cytosine were determined using a microplate-based ELISA. The findings indicate that co-culture for 72 h of CCD -18Co cells with HT-29 cells resulted in marked global DNA hypomethylation of colonic fibroblasts. Putative molecular changes provoked in fibroblasts by HT-29 induced- DNA hypomethylation, such as the expression of cyclooxygenase-2 (COX-2) and fibroblast-activation protein, are under investigation. Consonant with this line of research, COX-2 expression was shown to be up-regulated by HT-29-derived - conditioned medium (CM).

A concomitant research is focused on the characterization of the epigenetic profile of human stromal colonic fibroblasts harvested from tissue specimens of normal individuals and from patients during the adenoma-carcinoma sequence of colorectal cancer (CRC). The question asked is: at which CRC stage(s) normal stromal colonic fibroblasts become rogue, cancer-promoting cells?