Biochemistry and biology of SPINK-PSTI and monitor peptide

Three-Dimensional Structure of Novel Liver Cancer Biomarker Liver Cancer-Specific Serine Protease Inhibitor Kazal (LC-SPIK) and Its Performance in Clinical Diagnosis of Hepatocellular Carcinoma (HCC)

LC-SPIK is a liver cancer-specific isoform of Serine Protease Inhibitor Kazal and has been proposed as a new biomarker for the detection of HCC given its unique 3D structure, which differs from normal pancreatic SPIK. An ELISA technology based on its unique structure was developed to use LC-SPIK as an effective biomarker for the clinical diagnosis of HCC. AFP, the most widely used biomarker for HCC surveillance currently, suffers from poor clinical performance, especially in the detection of early-stage HCC. In one case-control study, which included 164 HCC patients and 324 controls, LC-SPIK had an AUC of 0.87 compared to only 0.70 for AFP in distinguishing HCC from liver disease controls (cirrhosis, HBV/HCV). LC-SPIK also performed significantly better than AFP for the 81 patients with early-stage HCC (BCLC stage 0 and A), with an AUC of 0.85 compared to only 0.61 for AFP. Cirrhosis is the major risk factor for HCC; about 80% of patients with newly diagnosed HCC have preexisting cirrhosis. LC-SPIK's clinical performance was also studied in HCC patients with viral and non-viral cirrhosis, including cirrhosis caused by metabolic dysfunction-associated steatotic liver disease (MASLD) and alcoholic liver disease (ALD). In a total of 163 viral cirrhosis patients with 93 HCC patients (50 early-stage), LC-SPIK had an AUC of 0.85, while AFP had an AUC of 0.70. For patients with early-stage HCC, LC-SPIK had a similar AUC of 0.83, while AFP had an AUC of only 0.60. For 120 patients with nonviral cirrhosis, including 62 HCC (23 early-stage) patients, LC-SPIK had an AUC of 0.84, while AFP had an AUC of only 0.72. For the 23 patients with early-stage HCC, LC-SPIK had a similar AUC of 0.83, while the AUC for AFP decreased to 0.65. All these results suggest that LC-SPIK exhibits significantly better performance in the detection of HCC than AFP in all etiologies of liver diseases. In addition, LC-SPIK accurately detected the presence of HCC in 71-91% of HCC patients with false-negative AFP test results in viral-associated HCC and non-viral-associated HCC.

Roles of Autophagy and Pancreatic Secretory Trypsin Inhibitor in Trypsinogen Activation in Acute Pancreatitis

The focus of the review is on roles of autophagy and pancreatic secretory trypsin inhibitor (PSTI), an endogenous trypsin inhibitor, in trypsinogen activation in acute pancreatitis. Acute pancreatitis is a disease in which tissues in and around the pancreas are autodigested by pancreatic digestive enzymes. This reaction is triggered by the intrapancreatic activation of trypsinogen. Autophagy causes trypsinogen and cathepsin B, a trypsinogen activator, to colocalize within the autolysosomes. Consequently, if the resultant trypsin activity exceeds the inhibitory activity of PSTI, the pancreatic digestive enzymes are activated, and they cause autodigestion of the acinar cells. Thus, autophagy and PSTI play important roles in the development and suppression of acute pancreatitis, respectively.

Ablation of huntingtin in adult neurons is nondeleterious but its depletion in young mice causes acute pancreatitis

The Huntington's disease (HD) protein, huntingtin (HTT), is essential for early development. Because suppressing the expression of mutant HTT is an important approach to treat the disease, we must first understand the normal function of Htt in adults versus younger animals. Using inducible Htt knockout mice, we found that Htt depletion does not lead to adult neurodegeneration or animal death at >4 mo of age, which was also verified by selectively depleting Htt in neurons. On the other hand, young Htt KO mice die at 2 mo of age of acute pancreatitis due to the degeneration of pancreatic acinar cells. Importantly, Htt interacts with the trypsin inhibitor, serine protease inhibitor Kazal-type 3 (Spink3), to inhibit activation of digestive enzymes in acinar cells in young mice, and transgenic HTT can rescue the early death of Htt KO mice. These findings point out age- and cell type-dependent vital functions of Htt and the safety of knocking down neuronal Htt expression in adult brains as a treatment.

A review of animal models of nonneoplastic pancreatic diseases

The nonneoplastic diseases of the human pancreas generally comprise the inflammatory and degenerative conditions that include acute and chronic pancreatitis, with cystic fibrosis being arguably one of the most important diseases that induce the condition. Both acute and chronic conditions vary in severity, but both can be life threatening; and because of this fact, the study of their progression, and their responsiveness to therapy, is largely conducted by indirect means using serum markers of damage and repair such as amylase and lipase activities that normally occur at very low levels in the circulation but can be significantly increased during inflammatory episodes. Progress in the understanding the pathogenesis of both conditions has therefore been largely due to time course studies in animal models of pancreatitis, and it is in this context that animal model development has been so significant. In general terms, the animal models can be divided into the invasive, surgical procedures, and those induced by the administration of chemical secretagogues that induce hypersecretion of the pancreatic enzymes. The former include ligation and/or cannulation of the biliopancreatic ducts with infusion of solutions of various kinds, or the formation of closed duodenal loops. Secretagogue administration includes administration of caerulein or l-arginine in various protocols. An additional model involves administration of dibutyltin dichloride, which induces a partial blockage of the pancreatic ducts to induce pancreatic disease through enzymic reflux into the gland. The models have been invaluable in generating testable hypotheses for the human diseases. These hypotheses for the production of cellular damage as the initiating events in the disease include (1) intracellular chemical activation, (2) pancreatic secretion reflux, (3) intracellular production of reactive oxygen species, and (4) intracellular production of free radicals.

Cyst fluid SPINK1 may help to differentiate benign and potentially malignant cystic pancreatic lesions

OBJECTIVE

Differential diagnosis between benign and potentially malignant cystic pancreatic lesions may be difficult. Previously we have compared cyst fluid serine protease inhibitor Kazal type I (SPINK1) with some traditionally used tumour markers (amylase, CEA, Ca19-9) and found that it may be a new promising maker in the differential diagnosis of cystic pancreatic lesions. In the present study, we focused on cyst fluid SPINK1 levels in benign and potentially malignant cystic pancreatic lesions.

DESIGN

Sixty-one patients operated on for cystic pancreatic lesion in Tampere University Hospital, Finland and in Verona University Hospital, Italy, were included. Cyst fluid was aspirated during surgery, stored at -70 °C, and analysed with immunofluorometric assay for SPINK1. The final diagnosis was acute pancreatitis with fluid collection (Acute FC) in 4 patients, chronic pseudocyst (PS) in 17 patients, serous cystadenoma (SCA) in 7 patients, mucinous cystadenoma (MCA) in 21 patients and intraductal papillary-mucinous neoplasm (IPMN) in 12 patients (9 main/mixed duct type and 3 branch duct type).

RESULTS

The acute FC patients had high SPINK1 levels. Among chronic cysts, SPINK1 levels were significantly higher in patients with potentially malignant cysts (main/mixed duct IPMN and MCA) than with benign cysts (side branch IPMN and SCA), (median and range, [480 (13-3602) vs. 18 (0.1-278) μg/L]; p < 0.0001). In the subcohort of 24 patients with <3 cm chronic cyst, cyst fluid SPINK 1 levels were significantly lower in SCA or side branch IPMN (3 [2-116] μg/L) than in main duct IPMN or MCA (638 [66-3602] μg/L; p = 0.018). The best sensitivity and specificity to differentiate any size MCA or main/mixed type IPMN from SCA or side branch IPMN were 85% and 84% (AUC 0.94; cut-off value 118 μg/L). The best sensitivity and specificity to differentiate <3 cm MCA or main duct IPMN from SCA or side branch IPMN were 93% and 89% (AUC 0.98; cut-off value 146 μg/L).

CONCLUSIONS

Cyst fluid SPINK1 may be a possible marker in the differential diagnosis of benign and potentially malignant cystic pancreatic lesions.

Peptidergic control of food intake and digestion in insects 1This review is part of a virtual symposium on recent advances in understanding a variety of complex regulatory processes in insect physiology and endocrinology, including development, metabolism, cold hardiness, food intake and digestion, and diuresis, through the use of omics technologies in the postgenomic era

Like all heterotrophic organisms, insects require a strict control of food intake and efficient digestion of food into nutrients to maintain homeostasis and to fulfill physiological tasks. Feeding and digestion are steered by both external and internal signals that are transduced by a multitude of regulatory factors, delivered either by neurons innervating the gut or mouthparts, or by midgut endocrine cells. The present review gives an overview of peptide regulators known to control feeding and digestion in insects. We describe the discovery and functional role in these processes for insect allatoregulatory peptides, diuretic hormones, FMRFamide-related peptides, (short) neuropeptide F, proctolin, saliva production stimulating peptides, kinins, and tachykinins. These peptides control either gut myoactivity, food intake, and (or) release of digestive enzymes. Some peptides exert their action at multiple levels, possibly having a biological function that depends on their site of delivery. Many regulatory peptides have been physically extracted from different insect species. However, multiple peptidomics, proteomics, transcriptomics, and genome sequencing projects have led to increased discovery and prediction of peptide (precursor) and receptor sequences. In combination with physiological experiments, these large-scale projects have already led to important steps forward in unraveling the physiology of feeding and digestion in insects.

Poly(A) RT-PCR measurement of diagnostic genes in pancreatic juice in pancreatic cancer

Background:

The last decade has seen significant progress in understanding the molecular biology of pancreatic adenocarcinoma. There is now an urgent need to translate these molecular techniques to clinical practice in order to improve diagnosis and prediction of response to treatment. The objectives of this study are to utilise poly(A) RT–PCR to measure expression levels of diagnostic Indicator genes, selected from microarray studies, of RNA from intraoperatively sampled pancreatic ductal juice and to correlate these expression levels with those in matched pancreatic tissue resection samples.

Methods:

Intraoperative sampling of pancreatic juice and collection of matched tissue samples was undertaken in patients undergoing pancreaticoduodenectomy for suspected tumour. RNA was isolated and poly(A) PCR and real-time PCR used to measure expression levels of 30 genes. Spearman's rank correlation test was used to examine the relationship of gene expression between pancreatic juice and tissue.

Results:

Of the 30 Indicator genes measured, just one, ANXA1, showed a significant correlation of expression level between pancreatic juice and tissue samples, whereas three genes, IGFBP3 (P⩽0.035), PSCA (P⩽0.001) and SPINK1 (P⩽0.05), showed significantly different expression between cancerous and benign pancreatic tissue samples.

Conclusions:

These results demonstrate that RNA analysis of pancreatic juice is feasible using the poly(A) cDNA technique, that correlation of gene expression exists between pancreatic juice and tissue for very few genes and that gene expression profiling can distinguish between benign and malignant pancreatic tissue. This indicates possible use of the technique for measurement of Indicator genes in pancreatic tissue for diagnosis of pancreatic cancer from very small tissue samples.

Transgenic expression of pancreatic secretory trypsin inhibitor-1 rescues SPINK3-deficient mice and restores a normal pancreatic phenotype

Endogenous trypsin inhibitors are synthesized, stored, and secreted by pancreatic acinar cells. It is believed that they play a protective role in the pancreas by inhibiting trypsin within the cell should trypsinogen become prematurely activated. Rodent trypsin inhibitors are highly homologous to human serine protease inhibitor Kazal-type 1 (SPINK1). The mouse has one pancreatic trypsin inhibitor known as SPINK3, and the rat has two trypsin inhibitors commonly known as pancreatic secretory trypsin inhibitors I and II (PSTI-I and -II). Rat PSTI-I is a 61-amino acid protein that shares 65% sequence identity with mouse SPINK3. It was recently demonstrated that mice with genetic deletion of the Spink3 gene (Spink3(-/-)) do not survive beyond 15 days and lack normal pancreata because of pancreatic autophagy. We have shown that targeted transgenic expression of the rat Psti1 gene to acinar cells in mice [TgN(Psti1)] protects mice against caerulein-induced pancreatitis. To determine whether the autophagic phenotype and lethality in Spink3(-/-) mice were due to lack of pancreatic trypsin inhibitor, we conducted breeding studies with Spink3(+/-) heterozygous mice and TgN(Psti1) mice. We observed that, whereas Spink3(+/+), Spink3(+/-), and Spink3(-/-)/TgN(Psti1) mice had similar survival rates, no Spink3(-/-) mice survived longer than 1 wk. The level of expression of SPINK3 protein in acini was reduced in heterozygote mice compared with wild-type mice. Furthermore, endogenous trypsin inhibitor capacity was reduced in the pancreas of heterozygote mice compared with wild-type or knockout mice rescued with the rat Psti1 gene. Surprisingly, the lesser amount of SPINK3 present in the pancreata of heterozygote mice did not predispose animals to increased susceptibility to caerulein-induced acute pancreatitis. We propose that a threshold level of expression is sufficient to protect against pancreatitis.

Hepatitis B and hepatitis C virus replication upregulates serine protease inhibitor Kazal, resulting in cellular resistance to serine protease-dependent apoptosis

Hepatitis B and C viruses (HBV and HCV, respectively) are different and distinct viruses, but there are striking similarities in their disease potential. Infection by either virus can cause chronic hepatitis, liver cirrhosis, and ultimately, liver cancer, despite the fact that no pathogenetic mechanisms are known which are shared by the two viruses. Our recent studies have suggested that replication of either of these viruses upregulates a cellular protein called serine protease inhibitor Kazal (SPIK). Furthermore, the data have shown that cells containing HBV and HCV are more resistant to serine protease-dependent apoptotic death. Since our previous studies have shown that SPIK is an inhibitor of serine protease-dependent apoptosis, it is hypothesized that the upregulation of SPIK caused by HBV and HCV replication leads to cell resistance to apoptosis. The evasion of apoptotic death by infected cells results in persistent viral replication and constant liver inflammation, which leads to gradual accumulation of genetic changes and eventual development of cancer. These findings suggest a possibility by which HBV and HCV, two very different viruses, can share a common mechanism in provoking liver disease and cancer.

Tumor-associated protein SPIK/TATI suppresses serine protease dependent cell apoptosis

Serine protease dependent cell apoptosis (SPDCA) is a recently described caspase independent innate apoptotic pathway. It differs from the traditional caspase dependent apoptotic pathway in that serine proteases, not caspases, are critical to the apoptotic process. The mechanism of SPDCA is still unclear and further investigation is needed to determine any role it may play in maintaining cellular homeostasis and development of disease. The current knowledge about this pathway is limited only to the inhibitory effects of some serine protease inhibitors. Synthetic agents such as pefabloc, AEBSF and TPCK can inhibit this apoptotic process in cultured cells. There is little known, however, about biologically active agents available in the cell which can inhibit SPDCA. Here, we show that over-expression of a cellular protein called serine protease inhibitor Kazal (SPIK/TATI/PSTI) results in a significant decrease in cell susceptibility to SPDCA, suggesting that SPIK is an apoptosis inhibitor suppressing this pathway of apoptosis. Previous work has associated SPIK and cancer development, indicating that this finding will help to open the doorway for further study on the mechanism of SPDCA and the role it may play in cancer development.