Purification and assay of secretory lithostathine in human pancreatic juice by fast protein liquid chromatography

Pancreatic stone protein/regenerating protein family in pancreatic and gastrointestinal diseases

Pancreatic stone protein (PSP; reported in 1979), pancreatitis-associated protein (PAP; 1984) and regenerating protein (Reg I; 1988) were discovered independently in the fields of the exocrine (pancreatitis) and endocrine (diabetes) pancreas. Subsequent analysis revealed that PSP and Reg I are identical and PAP belongs to the same protein family. PSP/Reg I and PAP share a selective and specific trypsin cleavage site and result in insoluble fibrils (PTP, PATP). Search for a functional role of PSP had led to the idea that it might serve as an inhibitor in pancreatic stone formation and PSP was renamed lithostathine. Inhibitory effects of lithostathine in stone formation have been questioned. Evidence so far obtained can support a lithogenic role rather than a lithostatic role of PSP. PAP and its isoforms have been investigated mainly regarding responses to inflammation and stress. Reg I and its isoforms have been examined on regeneration, growth and mitogenesis in gastrointestinal neoplastic diseases as well as diabetes. Evidence obtained can be applied in the prediction of prognosis and therapy for inflammatory and neoplastic diseases.

Pancreatitis-associated protein levels in pancreatic juice from patients with pancreatic diseases

BACKGROUND

Pancreatitis-associated protein (PAP), the acute-phase protein of the pancreas, is overexpressed in acute pancreatitis. Serum PAP levels were reported to be useful as an indicator of the severity, prognosis and healing of acute pancreatitis. Although PAP was originally identified in pancreatic juice, there has been no clinical report on PAP levels in pancreatic juice. This study was conducted to determine levels of PAP in pancreatic juice (PJ-PAP) in various human pancreatic diseases.

METHODS

PAP levels in endoscopically aspirated PJ were measured by enzyme-linked immunosorbent assay in 86 patients with pancreatic diseases.

RESULTS

55% of 22 patients with pancreatic cancer (PC) and 25% of 49 patients with chronic pancreatitis (CP) were positive (> 350 ng/ml) for PJ-PAP. PJ-PAP levels were significantly higher in PC than in CP, in which PJ-PAP was also significantly higher than in 15 control subjects. There was no significant correlation between PJ-PAP and serum PAP, and combination assay of serum PAP and/or PJ-PAP detected 80% of PC cases and 44% of CP cases.

CONCLUSIONS

We have demonstrated that human PAP could be detected in pancreatic juice from patients with pancreatic diseases. Determination of PAP in pancreatic juice might be helpful for early detection of pancreatic injury.

Human aspartyl (asparaginyl) beta-hydroxylase monoclonal antibodies: potential biomarkers for pancreatic carcinoma

INTRODUCTION

Pancreatic adenocarcinoma is among the top 10 leading causes of death due to cancer in the United States. The lack of reliable and sensitive biomarkers for this disease makes it difficult to render an early diagnosis.

AIMS

To evaluate carcinoma-associated monoclonal antibodies (MoAbs), including AF-20, SF-25, and FB-50, for their binding specificity to pancreatic adenocarcinoma relative to normal pancreatic tissue. In addition, binding of the Th9 MoAb to human Reg 1 protein was studied because of its potential role in cell growth.

METHODOLOGY

Adjacent histologic sections were immunostained with each of the MoAbs and graded on a scale of 0 to 4+, corresponding to the relative distribution and intensity of immunoreactivity within the tumor and normal adjacent tissue.

RESULTS

Intense levels (grade 3 or 4) of FB50 immunoreactivity were detected in 19 of 19 tumors but not in normal adjacent pancreatic tissue. In addition, increased levels of FB50 immunoreactivity were detected in at least 75% of the tumor cells in 18 of the 19 cases. SF-25 immunoreactivity similarly distinguished pancreatic adenocarcinoma from normal pancreas in 14 of 19 cases. In contrast, AF20 immunoreactivity was detected in 6 of 19 pancreatic adenocarcinomas, and for the most part, the labeling was focal and of a low level. TH9 immunoreactivity was detected in 5 of 19 tumors but also in normal as well as inflamed adjacent pancreatic tissue.

CONCLUSION

These results suggest that the FB50 and SF25 MoAbs represent excellent potential biomarkers of pancreatic adenocarcinoma and could be configured in an immunoassay for detecting pancreatic adenocarcinoma cells in biologic fluids.

No abnormalities of reg1 alpha and reg1 beta gene associated with diabetes mellitus

In order to investigate whether there would be any association between abnormalities of either reg1 alpha or reg1 beta gene and diabetes mellitus in man, these two genes were analyzed in 42 patients with type 1 diabetes mellitus, 12 with fibrocalculous pancreatopathy, 37 with type 2 diabetes mellitus, and 22 normal controls, by PCR-SSCP analysis and nucleotide sequencing technique. Polymorphism in the reg1 alpha gene resulted in three mobility patterns in the PCR-SSCP analysis, due to nucleotide constituents at position -10 before exon 1 being either C/C, T/C or T/T. These three mobility patterns were observed in every group of subjects. The analysis of reg1 beta gene showed nucleotide substitutions in exon 4 in one patient, exon 5 in another patient with type 1 diabetes, and in exon 4 and intron 5 in one patient with fibrocalculous pancreatopathy. The nucleotide substitutions in exon 4 in the patient with type 1 diabetes and that with fibrocalculous pancreatopathy occurred at codons 103 and 84 while that in exon 5 in the patient with type 1 diabetes occurred at codon 141, changing the codons from CAT to CAC, GTG to GCG, and ACT to AAT and resulting in H103H silent, V84A and T141N missense mutations, respectively. In conclusion, using PCR-SSCP and nucleotide sequence analyses, we did not find any association between abnormalities of either reg1 alpha or reg1 beta gene with any type of diabetes studied.

Lithostathine, the presumed pancreatic stone inhibitor, does not interact specifically with calcium carbonate crystals

Lithostathine (pancreatic stone protein, Reg protein) is, in addition to albumin, the major nonenzymatic protein of the pancreatic juice. It has been assumed to inhibit calcium carbonate precipitation and therefore to prevent stone formation in the pancreatic ducts. This function is, however, debatable. The assumption is based on the inhibition of in vitro crystal nucleation and growth by lithostathine. Considering that these phenomena occur only under certain critical conditions, we re-examined the question using a protein preparation where the purity and folding have been tested by mass spectroscopy and NMR in the absence of nonprotein contaminants. Under these conditions, we showed conclusively that lithostathine does not inhibit calcium carbonate nucleation and crystal growth. We demonstrated that previous findings on the alleged inhibition can be attributed to the uncontrolled presence of salts in the protein preparation used. Moreover, the affinity of lithostathine to calcite crystals, expressed as the half-life of bound iodinated protein in the presence of unlabeled competitor, was significantly lower than that of bovine serum albumin (8.8 and 11.2 h, respectively). Using glass microspheres instead of crystals did not significantly change the half-life of bound lithostathine (8.0 h). These findings are incompatible with the hypothesis of a specific interaction of lithostathine with calcium carbonate crystals. In conclusion, considering that components of pancreatic juice such as NaCl and phosphate ions are powerful inhibitors of calcium carbonate crystal growth, the mechanism of stone formation in pancreatic ducts must be reconsidered. The presence in normal pancreatic juice of small amounts of the 133-residue isoform of lithostathine (PSP-S1), which precipitates at physiological pH, should be noted, and the possibility should be considered that they form micro-precipitates that aggregate and are progressively calcified.