Intercalated duct cell is starting point in development of pancreatic ductal carcinoma?

Abstract

Background: Although it is well known that the pancreatic ductal carcinoma may develop having a relationship to the mucous gland hyperplasia (MGH) with atypia (PanIN-1B by PanIN system), the starting point of this atypical MGH is unclear. To know it, we examined the pancreas tissue using many methods described below.

Methods: 1. Twenty-seven surgically resected pancreas tissue specimens, including pancreatic ductal carcinomas (PDC), chronic pancreatitis and normal pancreas, were investigated using immunohistochemical stainings for MUC1, MUC6, 45M1, Ki67 and p53. 2. DNA extraction and analysis of K-ras mutation at codon 12 using microdissection method: The paraffin blocks with 16 regions including the intercalated duct cell (IC) adjacent to the atypical MGH were prepared for DNA extraction. Mutation of K-ras codon 12 was analyzed and compared in enriched polymerase chain reaction-enzyme-linked mini sequence assay (PCR-ELMA).

Results: 1. In the normal pancreas, although no positive cell was seen in 45M1, p53, Ki67, the cytoplasm of IC were always positive for MUC1 and sometimes positive for MUC6. In the pancreas with fibrosis or inflammation, MGH was positive for MUC6 and 45M1. And atypical MGH was positive for MUC1, MUC6 and 45M1. Some IC adjacent to the atypical MGH was positive for Ki67 as well as atypical MGH. The carcinoma cells in all cases of PDC were diffusely positive for MUC1, 45M1, p53 and Ki67, and focally positive for MUC6. 2. In K-ras mutation, we examined the regions including IC adjacent to the atypical MGH, because the immunohistochemical apomucin stainings of these regions resembled those of PDC as described above. And K-ras mutation was confirmed in 12 of 16 regions (75%). All mutations were a single mutation, in 6 regions GTT was detected, in 4 regions GAT was detected and in 2 region AGT was detected.

Conclusion: Some intercalated duct cell may be the starting point of the pancreatic ductal carcinoma, because the exhibitions of mucin expressions, Ki67, p53 and K-ras mutation in some intercalated duct cell resembled those of mucous gland hyperplasia or pancreatic ductal carcinoma.

Figure 1

Enriched polymerase chain reaction – enzyme linked mini-sequence assay (PCR-ELMA), showing K-ras codon 12 mutation in mucous gland hyperplasia of the pancreas. AGT – type mutation was seen in lane 3.

Figure 2

In normal pancreas, only the intercalated duct cells were positive for MUC1. (Left: HE, Right: MUC1, original magnification × 400)

Figure 3

The epithelium of the mucous gland hyperplasia was positive for 45M1. (Left: HE, Right: 45M1, original magnification × 200)

Figure 4

The intercalated duct cells adjacent to the atypical mucous gland hyperplasia were positive for Ki67. (Ki67, original magnification × 200)