Familial adenomatous polyposis (FAP) was found to be completely reversed in a patient treated with mycophenolate mofetil (MMF) and tacrolimus following kidney transplantation. In this preliminary study, we assessed whether MMF and tacrolimus alone or in combination interfere with the cell cycle and proliferation in a human colonic adenocarcinoma cell line and in the colonic polyps of the patient with FAP.

Human colonic adenocarcinoma HT-29 cells were treated with tacrolimus and MMF alone and in combination at different concentrations. Cell viability and proliferation were assessed using the MTT assay. Cell-cycle distribution was analyzed by flow cytometry. Expression of Ki-67, a marker of mitotic activity, was evaluated in the patient's colonic polyps before and under drug treatment.

MMF in combination with tacrolimus induced S-phase cell-cycle arrest and markedly inhibited HT-29 cell proliferation. Ki-67 expression in the patient's colonic polyps was significantly reduced following combined tacrolimus and MMF treatment.

MMF and tacrolimus synergistically inhibited proliferation of a human colonic adenocarcinoma cell line and interfered with the expansion of colonic crypt proliferation in the polyp from a patient with FAP. The results confirm our clinical observation and indicate the possibility of novel approach to therapy of colorectal neoplasia.