Purpose: Papilla of Vater cancer has a much better prognosis than pancreatic cancer. It is not known whether this is the result of differences in the tumor biology of the two malignancies. Because metastasis formation is a critical step in tumor progression and a negative prognostic factor, we compared the expression of nm23-H1 and KAI1, two metastasis-suppressing genes, in papilla of Vater cancer and pancreatic cancer.
Patients and methods: Analysis was performed in nine normal human papilla of Vater samples, 27 papilla of Vater cancers, 16 normal pancreatic samples, and 29 pancreatic cancers. Expression of nm23-H1 and KAI1 was analyzed by Northern blot analysis and in situ hybridization. In addition, immunohistochemistry was performed to localize the respective proteins.
Results: There was no difference in nm23-H1 and KAI1 mRNA expression levels in normal versus cancerous papilla of Vater samples. In contrast, nm23-H1 and KAI1 RNA expression was upregulated in early tumor stages of pancreatic cancer and reduced in advanced tumor stages. When expression of nm23-H1 and KAI1 RNA was analyzed by use of in situ hybridization, normal epithelial cells of the papilla of Vater exhibited mRNA staining intensity similar to that of papilla of Vater cancer cells. Similar levels of nm23-H1 and KAI1 immunoreactivity also were observed in these samples. In contrast, early stage pancreatic cancer samples exhibited stronger nm23-H1 and KAI1 immunoreactivity than normal controls. Furthermore, early pancreatic cancer stages exhibited higher KAI1 and nm23-H1 immunostaining than advanced tumor stages.
Conclusion: Differences in the expression patterns of the two tumor suppressor genes nm23-H1 and KAI1 may contribute to the different prognoses of papilla of Vater cancer and pancreatic cancer. Our findings support the hypothesis that biologic differences rather than earlier diagnosis influence the different outcomes of these two tumor entities.