UC Irvine

Difluoromethylornithine (DFMO) is an investigational chemopreventive agent that inhibits ornithine decarboxylase (ODC) activity, lowers cellular polyamine concentrations, and decreases cell proliferation in vivo and in vitro. In five subjects we have compared the polyamine concentrations in rectal mucosal biopsies and in exfoliated buccal mucosal cells (EBM) before and after DFMO treatment to assess the suitability of EBM as an easily accessible marker tissue for DFMO suppression of polyamine synthesis in the rectal mucosa. One month of 3 g/m2/day of DFMO treatment caused a statistically significant decrease in putrescine and spermidine concentrations in rectal mucosa biopsy specimens but not in EBM samples. ODC activity in EBM was high (approximately 1 mumol/min/mg protein), resistant to DFMO inhibition (Ki = 4200 microM), dependent on GTP concentration (maximal at 0.1 mM), and was reduced concomitantly with bacterial concentration by antiseptic mouthwashing. Bacteria adherent to EBM were visible by electron microscopy. Forty bacterial colonies/ng protein were culturable from washed EBM samples. Oral bacteria preclude the use of EBM samples as a marker tissue of DFMO effect in the rectal mucosa, but oral DFMO therapy is effective in depleting polyamines in rectal mucosa.