Expression of ornithine decarboxylase mRNA in gastric carcinoma

BACKGROUND. Ornithine decarboxylase (ODC) is a key rate-limiting enzyme in polyamine biosynthesis. Several studies using an enzyme assay revealed that the ODC activity was higher in tumor tissue than in normal tissue. However, there is little information on the mRNA status of ODC in surgical specimens. ODC is a transcriptional target gene of c-myc. METHODS. cDNA was obtained by reverse transcription (RT) from fresh specimens of 56 surgical pairs of primary gastric carcinomas and corresponding normal tissue specimens. The ODC and c-myc mRNAs were subsequently detected by means of the polymerase chain reaction. The tumor/normal (T/N) ratio of ODC expression was calculated after correcting for glyceraldehyde-3-phosphate dehydrogenase as an internal control. The T/N ratio of ODC was plotted against that of c-myc. RESULTS. The corrected expression levels of ODC mRNA in the tumor were greater than those of the normal mucosa in 36 of 56 cases (64%). The cases of tumor with vascular vessel invasion showed a higher T/N ratio than those without vascular invasion (P < 0.01). Similarly, female patients showed a higher T/N ratio than male patients (P < 0.01). There was a significant correlation between the expressions of both ODC and c-myc genes (P < 0.05). CONCLUSIONS. The findings imply that (1) overexpression of ODC mRNA in tumor tissue may correlate with aggressive biologic behavior, such as vascular vessel invasion, and (2) there is an intimate correlation between ODC and c-myc genes.