Tadayoshi Abe

Frequent gain of copy number on the long arm of chromosome 20 in human pancreatic adenocarcinoma.

We have used comparative genomic hybridization (CGH) to survey genomic regions with aberrant copy numbers of DNA sequences in pancreatic adenocarcinoma. In 12 cell lines and 6 primary tumors from 18 patients with pancreatic adenocarcinomas, highly frequent losses (>60%) were observed on chromosome arms 6q, 9p, and 18q and the Y chromosome. Moderately frequent losses (40–60%) were observed on chromosome arms 3p, 4q, 8p, and 21q. Interestingly, these samples showed extremely high frequencies of increases in copy numbers of DNA sequences on the long arm of chromosome 20 (15/18, 83%). We further analyzed five cell lines by fluorescence in situ hybridization (FISH) with probes on chromosome 20 to define the increase in copy number more accurately, and we found that 20q was increased to between 5 and 8 copies per cell. These results suggest the existence of an oncogene or oncogenes on 20q that play a role in the development and/or the progression of pancreatic carcinogenesis. Genes Chromosom. Cancer 19:161–169, 1997.

Distinct progression pathways involving the dysfunction of DUSP6/MKP-3 in pancreatic intraepithelial neoplasia and intraductal papillary-mucinous neoplasms of the pancreas

DUSP6/MKP-3 is identified as a candidate tumor suppressor gene for pancreatic cancer. The aim of this study was to elucidate the roles of DUSP6 in the pancreatic carcinogenesis through the pancreatic intraepithelial neoplasia and/or intraductal papillary-mucinous neoplasms, both of which are considered to be precursor lesions of invasive carcinoma of the pancreas, by comparing with involvements of other major tumor suppressive pathways. Expressions of DUSP6, CDKN2A, TP53, and SMAD4 were investigated by immunohistochemistry in a total of 206 lesions of dysplastic ductal precursors and carcinomas retrieved from 52 pancreata with invasive ductal carcinomas and 51 of those with intraductal papillary-mucinous neoplasms. The intensity of staining was evaluated in lesions at different atypical grades and statistically compared among them. Mutations of KRAS2 were analyzed by methods of the allele-specific oligonucleotide hybridization and nucleotide sequencing. In pancreata with invasive ductal carcinomas, expressions of DUSP6 were abrogated exclusively in the invasive carcinoma cells in contrast to its fairly preserved expressions in pancreatic intraepithelial neoplasia. In pancreata with intraductal papillary-mucinous neoplasms, abrogated expressions of DUSP6 were observed in a relatively small fraction of intraductal adenoma/borderlines and intraductal carcinomas. Most of the intraductal adenoma/borderline lesions with abrogation of DUSP6 harbored mutations of KRAS2. None of the molecules was associated with each other in any grade of lesions. Morphological variations of papillae of the intraductal papillary-mucinous neoplasms were evaluated and analyzed for their associations with abrogations of the molecules, which resulted in finding of no significant associations. Our results suggest that the abrogation of DUSP6 is associated exclusively with progression from pancreatic intraepithelial neoplasia to the invasive ductal carcinoma while it is potentially associated with initiation of intraductal papillary-mucinous neoplasms with mutated KRAS2, which is independent of other major tumor suppressive pathways in both types of neoplasms.

Restoration of SMAD4 by gene therapy reverses the invasive phenotype in pancreatic adenocarcinoma cells.

SMAD4 is a critical cofactor in signal transduction pathways activated in response to transforming growth factor-beta (TGF-β)-related ligands, regulating cell growth and differentiation. The roles played by SMAD4 inactivation in tumours highlighted it as a tumour-suppressor gene. However, restoration of the TGF-β antiproliferative pathway following SMAD4 gene transfer in null-tumour cell lines is controversial. Herein, we report the inhibitory effects of SMAD4 on pancreatic tumour invasion and angiogenesis. Adenoviral transfer of this gene in a panel of SMAD4 homozygous-deleted human pancreatic tumour cell lines restored SMAD4 protein expression and function. Although it did not affect proliferation significantly in vitro, SMAD4 inhibited in vivo tumour growth in immunodeficient mice. In this xenograft setting, differential suppression of tumour growth in vivo was mediated, at least in part, through downregulation of vascular endothelial growth factor and expression of gelatinases. We documented the reduced invasion and angiogenesis histologically and by intravital microscopy, and gained mechanistic insight at the messenger and protein level. Finally, we found a negative reciprocal regulation between SMAD4 and ETS-1. ETS-1 is considered a marker for tumour invasion. Upon SMAD4 deletion, we detected high expression levels of ETS-1 in pancreatic tumour cells, suggesting the shift of the pancreatic tumour toward an invasive phenotype.

Detailed deletion mapping on chromosome arm 12q in human pancreatic adenocarcinoma: Identification of a 1-cM region of common allelic loss

As a first step toward understanding molecular mechanisms in human pancreatic carcinogenesis, we searched for the location of tumor suppressor genes by examining loss of heterozygosity (LOH) in 44 pancreatic cancer specimens. We used 46 microsatellite markers that spanned all of the autosomes. Frequent LOH was observed in six chromosomal regions: in chromosome arms 1p (32%), 6q (37%), 9p (50%), 12q (30%), 17p (59%), and 18q (35%). Because chromosome arm 12q is a reported target for allelic loss in some other cancers, we focused on this region with 66 primary specimens and identified the minimal common region of allelic loss within a 1‐cM interval in 12q22‐q23.1. Microsatellite instability (MI) was also examined in this study, and the incidence of MI(+) cases, in which MI of two or more microsatellite loci was detected, was 61% (27 of 44 informative cases). In pancreatic tumors with MI(+), mutations of the transforming growth factor β receptor II (RII) gene were not detected. Genes Chromosom Cancer 17:88–93 (1996).

Genomic analysis of DUSP6, a dual specificity MAP kinase phosphatase, in pancreatic cancer

DUSP6 (alias PYST1), one of the dual-specificity tyrosine phosphatases, is localized on 12q21, one of the regions of frequent allelic loss in pancreatic cancer. This gene is composed of three exons, and two forms of alternatively spliced transcripts are ubiquitously expressed. Although no mutations were observed in 26 pancreatic cancer cell lines, reduced expressions of the full-length transcripts were observed in some cell lines, which may suggest some role for DUSP6 in pancreatic carcinogenesis.

Characteristic clinicopathological features of the types of intraductal papillary-mucinous neoplasms of the pancreas.

Objectives: Intraductal papillary-mucinous neoplasm (IPMN) of the pancreas encompasses a spectrum of neoplasms with both morphological and immunohistochemical variations of mucin glycoproteins. Recently, a consensus nomenclature and criteria were histologically defined for classifying these variants of IPMNs into gastric, intestinal, pancreatobiliary, and oncocytic types. The purpose of this study was to determine associations between the histological types and clinicopathological features in patients with IPMN. Methods: Sixty-one patients with IPMN operated upon at Tohoku University Hospital between 1988 and 2006 were retrospectively analyzed. Results: Our series included 27 gastric-, 29 intestinal-, 4 pancreatobiliary-, and 1 oncocytic-type IPMNs. Statistically, the types of IPMN were significantly associated with the histological diagnoses, macroscopic types, and survival of the patients. Characteristically, the gastric-type IPMNs were likely to be diagnosed as benign, to be confined to branch ducts, and to have fair prognoses. On the other hand, the intestinal-type IPMNs were likely to be diagnosed as malignant, occupy the main duct, and have poor prognoses. Because of the small number of pancreatobiliary-type IPMNs and only 1 case of oncocytic-type IPMN, we were unable to determine any of their clinicopathological characteristics in our series. Conclusions: Evaluation of the histological types of IPMN may help to predict the clinical course of patients with IPMN and to design improved clinical management for these patients.

Synchronous and Metachronous Extrapancreatic Malignant Neoplasms in Patients with Intraductal Papillary-Mucinous Neoplasm of the Pancreas

Background/Aims: Patients with intraductal papillary-mucinous neoplasm (IPMN) of the pancreas are likely to have a better prognosis than those with conventional pancreatic ductal adenocarcinoma. Recently there have been some reports on extrapancreatic malignant neoplasms (EPM) occurring in patients with IPMN. The purpose of this study was to discover the characteristic features of IPMN with EPM compared with IPMN without EPM. Methods: 61 patients with IPMN who underwent surgery at Tohoku University Hospital between 1988 and 2006 were retrospectively analyzed. Results: The 61 patients with IPMN in this study comprised 25 with intraductal papillary-mucinous adenomas (IPMA) and 36 with intraductal papillary-mucinous carcinomas (IPMC) including 6 with invasive carcinomas. Synchronous and metachronous EPM were observed in 15 out of the 61 patients (24.6%). Three of these patients, including 2 with IPMA and 1 with invasive carcinoma associated with IPMC, died of the EPM. None of the features, including sex, age, smoking, family history, macroscopic types (main duct type or branch duct type), histological types (gastric, intestinal, pancreatobiliary or oncocytic), and aberrant expression of molecules including CDKN2A, TP53, SMAD4 and DUSP6, except for the histological diagnoses were associated with the occurrence of EPM, i.e., the EPM occurred more often in patients with IPMA (10 out of 25) than in those with IPMC (5 out of 36) in our series (p = 0.0199 by the χ2 test, p = 0.0330 by Fisher’s exact probability test, p = 0.0422 by Yates’ correction). Conclusion: Patients with IPMA were more likely to have EPM than those with IPMC. Patients with IPMA are usually expected to have a fair prognosis but EPM could be fatal in some of them, so it must be noted during follow-up.

The somatic mutation frequency of the transforming growth factor β receptor type II gene varies widely among different cancers with microsatellite instability

Disruption of the DNA mismatch repair system, characterized by microsatellite instability (MSI), plays an important role in the course of human carcinogenesis. Frequent somatic mutations in a polyadenine (poly(A)) tract and two GT repeats within the coding region of the transforming growth factor beta (TGFbeta) receptor II (RII) gene were reported in colorectal cancers with MSI. We examined mutations of RII in cancers of various organs with MSI and found deletions at the poly(A) tract in eight of nine (89%) gastric cancers and four of five (80%) colorectal cancers. In contrast, no mutations were found in cancers of the pancreas, endometrium, or lungs. These results suggest that TGFbeta-mediated growth control plays a very important role in the stomach and colorectum.

Identification of three commonly deleted regions on chromosome arm 6q in human pancreatic cancer.

Pancreatic cancer has one of the poorest prognoses among malignant diseases. To understand its molecular mechanisms, we studied allelic losses on the long arm of chromosome 6. Using 55 paired DNAs of tumors and their corresponding normal tissues and 30 microsatellite markers that spanned the entire 6q chromosome arm, we found three distinct regions of common allelic loss: region A, a less than 500‐kb region bordered by D6S449 and D6S283 on 6q21 with a loss of heterozygosity (LOH) frequency of 69% (38/55); region B, a 7‐cM region bordered by D6S292 and D6S308 on 6q23–q24 with a LOH frequency of 60% (33/55); and region C, a 13‐cM region bordered by D6S305 and D6S264 with a LOH frequency of 51% (28/55). We further focused on region A and constructed a physical map using yeast artificial chromosome (YAC) clones, their derived cosmid clones, and bacterial artificial chromosome (BAC) clones. Region A was completely covered by three overlapping BAC clones. Our results in the present study should shed light on the cloning and characterization of tumor suppressor genes in pancreatic carcinogenesis. Genes Chromosomes Cancer 25:60–64, 1999.

Chromosome 12, frequently deleted in human pancreatic cancer, may encode a tumor-suppressor gene that suppresses angiogenesis.

Several lines of evidence have suggested that the long arm of chromosome 12 may carry a tumor-suppressor gene(s) that plays a role in pancreatic ductal carcinogenesis. We have previously found a significant association between loss of heterozygosity of the 12q arm and a poor prognosis in pancreatic cancer patients. In this study, we introduced a normal copy of chromosome 12 into some pancreatic ductal carcinoma cells. Both anchorage-dependent and -independent proliferations as well as invasiveness were similar throughout the hybrid clones when compared with their corresponding parental cells. In sharp contrast, significant suppression of tumorigenesis was observed after inoculation of the hybrid clones into nude mice. Measurements made up to 1 month later showed that there was a significant delay in the growth of tumors into which the introduced normal copy of chromosome 12 had been restored. More significantly, using our dorsal skin chamber and an intravital microscopy system experiment in SCID mice, we demonstrated and visualized directly that implantation of the hybrids failed to promote the angiogenic phenotype encountered in the parental cells. Gene expression profiling using the complementary DNA microarray system identified a set of 24 genes differentially expressed between the hybrids and parental cells. An additional set of 18 genes was also identified that were differentially expressed between the hybrid clone that lost its growth-suppression activity and one that retained such activity. Another set of 25 genes mapped on 12q was detected that showed high expression levels in the hybrid clones retaining growth-suppressive activity. In summary, this study provides the first functional evidence of the existence of an additional tumor-suppressor gene(s) on chromosome 12, whose absence is responsible for the pathogenesis in pancreatic ductal carcinogenesis.