Defensin, a peptide detected in the saliva of patients with oral cancer patients.

The saliva of patients with oral cancer was subjected to reversed-phase HPLC and a peak (P14) eluted with a linear gradient of acetonitrile. In contrast, minimal P14 was detected in the saliva of healthy volunteers. P14 showed strong absorbance at a λ max of 278nm, and showed high fluorescence at λ em of 304nm and 348nm with a λ ex of 278nm. It seemed that P14 was a peptide containing tryptophan and tyrosine. The molecular weight of P14 was 3, 442 daltons on a mass spectrometry. Amino acid analysis by Edman degradation and homology studies showed that P14 was consistent with human α-defensin 1 (HNP-1), a peptide that belongs to the defensin family. HNP-1 was detected in the whole saliva of cancer patients, but only low levels were found in the serum, the parotid saliva, and the submandibular and sublingual saliva. The concentrations of HNP-1 in the whole saliva of the 8 preoperative and 13 postoperative carcinoma patients were 11.3±7.8 and 5.9±5.6 μg/ml (mean± S. D.), respectively. The concentration in the preoperative patients was higher than that in the postoperative patients and gradually decreased after operation. However, HNP-1 was found in the saliva of patients even a half year after operation. The origin of HNP-1 in the saliva of oral cancer patients was not clear, but it was suggested that HNP-1 might act as a defensive substance against carcinoma.