Faculty Bibliography

Total pancreatectomy has been used to treat both benign and malignant disease of the pancreas, but its use has been limited by concerns about management of the a-pancreatic state with its attendant total endocrine and exocrine insufficiency. Here, we review the indications for total pancreatectomy, operative technique, and improvements in the postoperative management of patients. Total pancreatectomy remains a viable option in the treatment of intractable pain associated with chronic pancreatitis, multicentric or extensive neuroendocrine tumors, patients with familial pancreatic cancer with premalignant lesions, and in patients with intraductal papillary mucinous neoplasia with diffuse ductal involvement or invasive disease. Improvements in postoperative management include auto-islet cell transplantation, advances in insulin formulations, and the use of glucagon rescue therapy which allow much tighter control of blood glucose than previously possible. This markedly lessens the risk of life-threatening hypoglycemia and decreases the risk of long-term complications, resulting in improved quality of life for these patients.

To investigate the role of transforming growth factor (TGF)-beta family signaling in the adult pancreas, a transgenic mouse (E-dnSmad4) was created that expresses a dominant-negative Smad4 protein driven by a fragment of the elastase promoter. Although E-dnSmad4 mice have normal growth, pancreas weight, and pancreatic exocrine and ductal histology, beginning at 4-6 wk of age, E-dnSmad4 mice show an age-dependent increase in the size of islets. In parallel, an expanded population of replicating cells expressing the E-dnSmad4 transgene is found in the stroma between the enlarged islets and pancreatic ducts. Despite the marked enlargement, E-dnSmad4 islets contain normal ratios and spatial organization of endocrine cell subtypes and have normal glucose homeostasis. Replication of cells derived from primary duct cultures of wild-type mice, but not E-dnSmad4 mice, was inhibited by the addition of TGF-beta family proteins, demonstrating a cell-autonomous effect of the transgene. These data show that, in the adult pancreas, TGF-beta family signaling plays a role in islet size by regulating the growth of a pluripotent progenitor cell residing in the periductal stroma of the pancreas.

Protein glycosylation has been implicated in key biological processes including immunological recognition, cellular adhesion, protein folding, and signaling as well as disease progression. Although several methods are available to assess glycosylation of protein structures, none of them is able to screen complex biological samples at a global as well as an individual scale. A novel strategy presented here uses an all-liquid phase enrichment and prefractionation methodology coupled to glycoprotein microarray technology using a multiple lectin-based, biotin-streptavidin detection scheme. Selective detection of glycan structures was made possible by employing multiple lectins to screen glycoprotein standards as well as serum samples from normal subjects or patients with chronic pancreatitis or pancreatic cancer. Interestingly, in some instances, a greater degree of glycosylation was seen in proteins that were underexpressed based on the reversed-phase chromatogram alone. Studies with standard proteins established the limits of detection to be in the 2.5-5-fmol range. Studies on serum samples showed differences in glycosylation patterns, particularly with respect to sialylation, mannosylation, and fucosylation, in normal, pancreatitis, and cancer sera. By coupling glycoprotein enrichment and fractionation with a microarray platform, we have shown that naturally occurring glycoproteins from human serum can be screened and characterized for different glycan structures, thereby allowing one to do comparative studies that monitor individual glycosylation changes within a glycoproteome representing different biological states. This approach may be useful to identify potential biomarkers in cancer.

A unique approach of automating the integration of monolithic capillary HPLC-based protein separation and on-plate digestion for subsequent MALDI-MS analysis has been developed. All liquid-handling procedures were performed using a robotic module. This automated high-throughput method minimizes the amount of time and extensive labor required for traditional in-solution digestion followed by exhaustive sample cleanup and analysis. Also, precise positioning of the droplet from the capillary HPLC separation onto the MALDI plate allows for preconcentration effects of analytes for improved sensitivity. Proteins from primary esophageal Barrett's adenocarcinoma tissue were prefractionated by chromatofocusing and analyzed successfully by this automated configuration, obtaining rapid protein identifications through PMF and sequencing analyses with high sequence coverage. Additionally, intact protein molecular weight values were obtained as a means to further confirm protein identification and also to identify potential sequence modifications of proteins. This simple and rapid method is a highly versatile and robust approach for the analysis of complex proteomes.

A strategy is developed in this study for identifying sialylated glycoprotein markers in human cancer serum. This method consists of three steps: lectin affinity selection, a liquid separation and characterization of the glycoprotein markers using mass spectrometry. In this work, we use three different lectins (Wheat Germ Agglutinin, (WGA) Elderberry lectin,(SNA), Maackia amurensis lectin, (MAL)) to extract sialylated glycoproteins from normal and cancer serum. Twelve highly abundant proteins are depleted from the serum using an IgY-12 antibody column. The use of the different lectin columns allows one to monitor the distribution of alpha(2,3) and alpha(2,6) linkage type sialylation in cancer serum vs that in normal samples. Extracted glycoproteins are fractionated using NPS-RP-HPLC followed by SDS-PAGE. Target glycoproteins are characterized further using mass spectrometry to elucidate the carbohydrate structure and glycosylation site. We applied this approach to the analysis of sialylated glycoproteins in pancreatic cancer serum. Approximately 130 sialylated glycoproteins are identified using microLC-MS/MS. Sialylated plasma protease C1 inhibitor is identified to be down-regulated in cancer serum. Changes in glycosylation sites in cancer serum are also observed by glycopeptide mapping using microLC-ESI-TOF-MS where the N83 glycosylation of alpha1-antitrypsin is down regulated. In addition, the glycan structures of the altered proteins are assigned using MALDI-QIT-MS. This strategy offers the ability to quantitatively analyze changes in glycoprotein abundance and detect the extent of glycosylation alteration as well as the carbohydrate structure that correlate with cancer.

Pancreatic cancer is a difficult and unsolved surgical problem. It remains one of the top five causes of cancer-related deaths and has the lowest 5-year survival of any cancer, largely due to late diagnosis, low resection rates, and local recurrence. Clinical trials examining the optimal timing and delivery of adjuvant therapies for pancreatic cancer have yielded controversial results. Although most experts agree that the addition of chemotherapy has survival benefit in patients with resectable pancreatic cancer, there is no consensus regarding the optimal therapeutic agents, timing (neoadjuvant versus adjuvant), and the addition of radiation therapy to the treatment regimen. Multiple phase III trials are in progress in efforts to examine these issues. Additionally, exciting progress has been made with novel chemotherapeutic combinations, and alternative treatment modalities including interferon-alpha, immunotherapy, and pancreatic cancer stem cells. Given the high failure pattern after surgical resection, with more than half of patients developing locoregional recurrence, all patients undergoing pancreaticoduodenectomy are candidates for adjuvant therapy.

Human chromosome 1p35-p36 has long been suspected to harbor a tumor suppressor gene in pancreatic cancer and other tumors. We found that expression of rap1GAP, a gene located in this chromosomal region, is significantly down-regulated in pancreatic cancer. Only a small percentage of preneoplastic pancreatic intraductal neoplasia lesions lost rap1GAP expression, whereas loss of rap1GAP expression occurred in 60% of invasive pancreatic cancers, suggesting that rap1GAP contributes to pancreatic cancer progression. In vitro and in vivo studies showed that loss of rap1GAP promotes pancreatic cancer growth, survival, and invasion, and may function through modulation of integrin activity. Furthermore, we showed a high frequency of loss of heterozygosity of rap1GAP in pancreatic cancer. Collectively, our data identify rap1GAP as a putative tumor suppressor gene in pancreatic cancer.

Pancreatic cancer has a poor prognosis, in part due to lack of early detection. The identification of circulating tumor antigens or their related autoantibodies provides a means for early cancer diagnosis. We have used a proteomic approach to identify proteins that commonly induce a humoral response in pancreatic cancer. Proteins from a pancreatic adenocarcinoma cell line (Panc-1) were subjected to two-dimensional PAGE, followed by Western blot analysis in which individual sera were tested for autoantibodies. Sera from 36 newly diagnosed patients with pancreatic cancer, 18 patients with chronic pancreatitis and 15 healthy subjects were analyzed. Autoantibodies were detected against a protein identified by mass spectrometry as vimentin, in sera from 16/36 patients with pancreatic cancer (44.4%). Only one of 18 chronic pancreatitis patients and none of the healthy controls exhibited reactivity against this vimentin isoform. Interestingly, none of several other isoforms of vimentin detectable in 2-D gels exhibited reactivity with patient sera. Vimentin protein expression levels were investigated by comparing the integrated intensity of spots visualized in 2-D PAGE gels of various cancers. Pancreatic tumor tissues showed greater than a 3-fold higher expression of total vimentin protein than did the lung, colon, and ovarian tumors that were analyzed. The specific antigenic isoform was found at 5-10 fold higher levels. The detection of autoantibodies to this specific isoform of vimentin may have utility for the early diagnosis of pancreatic cancer.

PURPOSE: In the current study, we examined the functional significance and mechanism of action of S100P in pancreatic cancer cells. EXPERIMENTAL DESIGN: S100P levels were increased in Panc-1 cells, which do not express S100P, by transfection with an S100P cDNA and S100P levels were reduced in BxPC3 cells, which express high levels of S100P, by small interfering RNA gene silencing. Effects of these manipulations on cell proliferation, resistance to apoptotic insults, cell migration, and invasion were estimated in vitro using standard assays. The influences of S100P on tumor growth in vivo were studied using xenograft mouse models. To identify the mechanisms involved in these responses, coimmunoprecipitation studies were conducted with S100P with receptor for advanced glycation end products (RAGE) and the effects of inhibiting RAGE using an antagonistic peptide were analyzed. RESULTS: S100P levels correlated with the rates of cell proliferation, survival, migration, and invasion in both cell models in vitro. In vivo, increased S100P levels increased the growth of tumors in mice with s.c.-implanted Panc-1 cells and decreased S100P levels decreased tumor growth after orthotopic implantation of BxPC-3 cells. A direct interaction between S100P and RAGE was indicated by coimmunoprecipitation of these molecules from pancreatic cancer cells. A RAGE antagonist peptide inhibited this interaction and also inhibited the biological effects of S100P on these cells in vitro. CONCLUSIONS: These data suggest that S100P plays a major role in the aggressiveness of pancreatic cancer that is likely mediated by its ability to activate RAGE. Thus, interference with S100P may provide a novel approach for treatment of pancreatic cancer.

OBJECTIVES: Tissue desmoplasia occurs in a number of disease states, but its molecular basis is poorly understood. To determine which genes are overexpressed in cells contained within the desmoplastic stroma of pancreatic adenocarcinoma and chronic pancreatitis, we undertook genetic profiling of microdissected tissue samples of pancreatic adenocarcinoma, chronic pancreatitis, normal pancreas, and pancreatic cancer cell lines. We observed that samples of both pancreatic adenocarcinoma and chronic pancreatitis showed elevated expression of many shared genes compared with the normal pancreas. We hypothesized that these common genes likely important in stromal production and/or function could be identified using a strategy that involved comparisons between pancreatic adenocarcinoma, chronic pancreatitis, normal pancreas, and pancreatic cancer cell lines. METHODS: We performed oligonucleotide microarray analysis of 6800 different genes expressed in 10 samples of pancreatic adenocarcinoma, 5 samples of normal pancreas, 5 samples of chronic pancreatitis, and 7 pancreatic cancer cell lines. Microarray findings were validated with RT-PCR, and immunohistochemistry was used to verify protein localization to the stromal compartment of both pancreatic cancer and chronic pancreatitis. RESULTS: We employed a deductive comparison whereby genes expressed in the normal pancreas and pancreatic cancer cell lines were selectively eliminated from those expressed in common by pancreatic adenocarcinoma and chronic pancreatitis. This strategy identified 107 genes predicted to be expressed within cells of the stromal compartment of both pancreatic adenocarcinoma and chronic pancreatitis. CONCLUSIONS: These genes are likely important factors in epithelial-stromal signaling in pancreatic desmoplasia and may serve as diagnostic or therapeutic targets.