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Polyamines as biomarkers of cervical intraepithelial neoplasia

Polyamines (putrescine, spermidine and spermine) play critical roles in cell growth and transformation. Ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, is considered a putative protooncogene crucial to the regulation of cell growth and transformation. Cancer patients have elevated levels of polyamines in their physiological fluids compared to normal counterparts. α‐Difluoromethylornithine (DFMO), a specific suicide inhibitor of ODC, exhibits antitumor and antimetastasis activities, and displays effectiveness in many carcinogen‐induced animal chemoprevention models. Therefore, we are using DFMO in a chemoprevention trial for cervical intraepithelial neoplasia grade III (CIN III), and evaluating patients for changes in polyamine metabolism as an intermediate marker of DFMO effect. A preliminary study showed that several milligrams of abnormal cervical biopsy tissue contained detectable levels of ODC activity and polyamines. Additionally, the presence of cadaverine suggested bacterial contamination of these tissues. For this reason, normal and abnormal biopsies collected during colposcopy were rinsed prior to frozen storage. In most patients, abnormal tissues showed greater ODC activities and lower spermidine/spermine ratios than normal tissues. Patients are now being treated with de‐escalating doses of DFMO (1‐0.06 g/m2/day) for one month. To study the effects of DFMO in patients with CIN III, we are collecting blood and cervical tissue specimens to measure the following parameters: Plasma DFMO, ornithine and arginine levels; plasma N1‐acetylspermidine levels; erythrocyte (blood polyamine carrier) free polyamine levels; cervical tissue free polyamine levels; cervical tissue N1‐acetyspermidine levels; and cervical tissue ODC activities. N1‐acetylspermidine will be examined as this compound is known to exist primarily in tumor tissues, not in normal tissues. We therefore established a high‐performance liquid chromatography method for N1‐acetylspermidine. We expect to find that polyamines are effective markers in analyzing DFMO effects in this chemoprevention trial, thus functioning as pharmacodynamic parameters as well as biomarkers for transformation.