Down-regulation of pancreatic and duodenal homeobox-1 by somatostatin receptor subtype 5: a novel mechanism for inhibition of cellular proliferation and insulin secretion by somatostatin

[Characteristics of gastric neuroendocrine tumors and the PDX-1 transcription factor expression]

OBJECTIVE

To study the features of gastric neuroendocrine tumors (NETs) and the diagnostic and prognostic significance of PDX-1 expression in them.

MATERIAL AND METHODS

207 NETs identified in 56 men and 115 women (59 had multiple NETs), and 94 cases of gastric cancer (comparison group) were studied morphologically and immunohistochemically.

RESULTS

In more than half of the cases (54.93%), NETs were localized in the body of the stomach; the cardiac and antral parts of the stomach accounted for 8.64% and 11.73%, respectively. NETs of the cardiac region predominated in men, and of the body and antrum - in women. NETs of the cardiac region predominated in men, and of the body and antrum - in women. The vast majority of NETs were highly differentiated (89.20%), of which Grade 1, 2 and 3 were 55.41%, 40.76% and 3.82%, respectively. Neuroendocrine carcinomas (NEC) accounted for 10.80% of all NET cases. NECs were more often localized in the cardiac part of the stomach and accounted for 35.71% of all NETs in the cardiac part. The share of NEC among all NETs of the antrum was 15.79%, of the body of the stomach - only 3.37%. Metastases were found in 17.90% of NETs. Expression of PDX-1 was detected in 44.73% of NETs, 70% of NECs and 74.50% of gastric cancers.

CONCLUSION

PDX-1 is involved in the mechanisms of precancerous and cancerous lesions of the stomach and its overexpression is detected in the majority of the most malignant NETs and gastric cancers.

Racial and Gender Disparities Among Obese Patients With Pancreatic Cancer: A Trend Analysis in the United States

BACKGROUND

Pancreatic cancer (PC) is the third leading cause of cancer death. Obesity can increase the risk of PC by up to 50%. Studies have shown racial and gender disparities in PC, however, there is a paucity of such information in obese PC patients.

AIM

The aim of this study was to: (1) evaluate the incidence and prevalence of obesity among PC patients in the United States over the last 15 years, and (2) determine if variation exists in the demographic of obese PC patients over the last 15 years. It is hoped that this information could be used to assist in primary prevention and early detection of PC.

METHODS

A population-based retrospective analysis in IBM Explorys, a pooled, national, deidentified database of 63 million patients from 300 hospitals in the United States. Patient populations were identified using SNOMED and ICD codes. Cochrane-Armitage testing was performed to analyze trends in obesity among PC. Subgroup analysis for gender, age, race, and mortality rate were assessed.

RESULTS

The percentage of obese patients with PC increased over the 15-year period (2.5% to 8.5%, P <0.0001). Rates of obesity among PC patients increased among females ( P =0.0004), individuals under age 65 years ( P =0.0002), and all races, but especially for African Americans ( P =0.0007) and those in minority groups.

CONCLUSION

Awareness of disparities in PC and applying targeted care to those at increased risk are essential to improve future outcomes, including increased health care access and recruitment in research studies for minority groups.

On the mechanism of tumor cell entry of aloe-emodin, a natural compound endowed with anticancer activity

Aloe‐emodin (1,8‐dihydroxy‐3‐[hydroxymethyl]‐anthraquinone), AE, is one of the active constituents of a number of plant species used in traditional medicine. We have previously identified, for the first time, AE as a new antitumor agent and shown that its selective in vitro and in vivo killing of neuroblastoma cells was promoted by a cell‐specific drug uptake process. However, the molecular mechanism underlying the cell entry of AE has remained elusive as yet. In this report, we show that AE enters tumor cells via two of the five somatostatin receptors: SSTR2 and SSTR5. This observation was suggested by gene silencing, receptor competition, imaging and molecular modeling experiments. Furthermore, SSTR2 was expressed in all surgical neuroblastoma specimens we analyzed by immunohistochemistry. The above findings have strong implications for the clinical adoption of this natural anthraquinone molecule as an antitumor agent.

In Vitro Studies to Assess the α-Glucosidase Inhibitory Activity and Insulin Secretion Effect of Isorhamnetin 3-O-Glucoside and Quercetin 3-O-Glucoside Isolated from Salicornia herbacea

In this study, we examined the effect of ethanolic extract of Salicornia herbacea (ESH), isorhamnetin 3-O-glucoside (I3G), quercetin 3-O-glucoside (Q3G), quercetin, and isorhamnetin on α-glucosidase activity and glucose-stimulated insulin secretion (GSIS) in insulin-secreting rat insulinoma (INS-1) cells. A portion of the ethyl acetate fraction of ESH was chromatographed on a silica gel by a gradient elution with chloroform and methanol to provide Q3G and I3G. ESH, Q3G, and quercetin inhibited α-glucosidase activity, and quercetin (IC50 value was 29.47 ± 3.36 μM) inhibited the activity more effectively than Q3G. We further demonstrated that ESH, Q3G, quercetin, I3G, and isorhamnetin promote GSIS in INS-1 pancreatic β-cells without inducing cytotoxicity. Among them, I3G was the most effective in enhancing GSIS. I3G enhanced the phosphorylation of total extracellular signal-regulated kinase (ERK), insulin receptor substrate-2 (IRS-2), phosphatidylinositol 3-kinase (PI3K), Akt, and activated pancreatic and duodenal homeobox-1 (PDX-1), which are associated with insulin secretion and β-cell function. As components of ESH, Q3G has the potential to regulate blood glucose by inhibiting α-glucosidase activity, and I3G enhances the insulin secretion, but its bioavailability should be considered in determining biological importance.

Stem Cell Therapy for Diabetes: Beta Cells versus Pancreatic Progenitors

Diabetes mellitus (DM) is one of the most prevalent metabolic disorders. In order to replace the function of the destroyed pancreatic beta cells in diabetes, islet transplantation is the most widely practiced treatment. However, it has several limitations. As an alternative approach, human pluripotent stem cells (hPSCs) can provide an unlimited source of pancreatic cells that have the ability to secrete insulin in response to a high blood glucose level. However, the determination of the appropriate pancreatic lineage candidate for the purpose of cell therapy for the treatment of diabetes is still debated. While hPSC-derived beta cells are perceived as the ultimate candidate, their efficiency needs further improvement in order to obtain a sufficient number of glucose responsive beta cells for transplantation therapy. On the other hand, hPSC-derived pancreatic progenitors can be efficiently generated in vitro and can further mature into glucose responsive beta cells in vivo after transplantation. Herein, we discuss the advantages and predicted challenges associated with the use of each of the two pancreatic lineage products for diabetes cell therapy. Furthermore, we address the co-generation of functionally relevant islet cell subpopulations and structural properties contributing to the glucose responsiveness of beta cells, as well as the available encapsulation technology for these cells.

Disparities in Pancreatic Cancer Treatment and Outcomes

Purpose: Pancreatic cancer remains a major health concern; in the next 2 years, it will become the second leading cause of cancer deaths in the United States. Health disparities in the treatment of pancreatic cancer exist across many disciplines, including race and ethnicity, socioeconomic status (SES), and insurance. This narrative review discusses what is known about these disparities, with the goal of highlighting targets for equity promoting interventions.

Methods: We performed a narrative review of health disparities in pancreatic cancer spanning greater than ten areas, including epidemiology, treatment, and outcome, using the PubMed NIH database from 2000 to 2019 in the Unites States.

Results: African Americans (AAs) tend to present at diagnosis with later stage disease. AAs and Hispanics have lower rates of surgical resection, are more likely to be treated at low volume hospitals, and often experience higher rates of morbidity and mortality compared to white patients, although control for confounders is often limited. Insurance and SES also factor into the delivery of treatment for pancreatic cancer.

Conclusion: Disparities by race and SES exist in the diagnosis and treatment of pancreatic cancer that are largely driven by race and SES. Improved understanding of underlying causes could inform interventions.

[Differential diagnostic value of the expression of the transcription factor PDX-1 in neuroendocrine and non-neuroendocrine tumors of the pancreas and other organs]

An important role in the differentiation of tissues in different organs is played by transforming factors (TFs); pancreatic and duodenal homebox 1 (PDX-1) is one of the earliest factors for pancreatic cells. Many malignant tumors, including neuroendocrine tumors (NETs), are similar in structure, and therefore the actual problem of oncomorphology is to search for narrow-specific markers and TFs.

AIM

to comparatively analyze and assess the value of the expression of the TF PDX-1 in NETs and non-NETs of different localization and histogenetic origin.

MATERIAL AND METHODS

Anti-PDX-1 antibodies were used to study 528 tumors divided into 3 groups: Group 1 included 394 NETs, among them there were those of the pancreas (n=173), stomach (n=46), bowel (n=65), lung (n=40), thymus (n=8), kidney (n=6), Merkel's cell carcinomas (n=14), NETs of the breast (n=3), larynx (n=2), trachea (n=2), bladder (n=1), and metastatic NETs (n=34) of unknown primary site; Group 2 consisted of 16 tumors, of them there were paragangliomas (n=6), medullary thyroid cancers (MTC) (n=6) and adrenal pheochromocytomas (APCC) (n=4); Group 3 comprised 118 non-NETs, among them there were tumors of the pancreas (n=54), stomach (n=26), bowel (n=17), lung (n=11), breast (n=3), kidney (n=4), adrenal glands (n=2), and bladder (n=1).

RESULTS

PDX-1 was positive in 75.1% (130/173) of pancreatic NETs, all insulinomas (50/50), gastrinomas (11/11), somatostatinomas (3/3), ACTH-producing tumors (2/2); PDX-1 was positive in the non-functioning pancreatic NETs, all PPomas (19/19), 76.1% (35/46) of NETs without the hormone detected, 50% (2/4) of calcitoninomas, and 21.1% (8/38) of silent glucagonomas. PDX-1 was positive in 32.4% (11/34) of carcinoids and 50% (6/12) of neuroendocrine carcinomas, all duodenal NETs (18/18), 90% (9/10) of rectal carcinoids and 30.8% (4/13) colonic carcinoids, 37.5% (3/8) of thymic/mediastinal carcinoids, 66.7% (4/6) of kidney carcinoids, and 37.5% (9/24) of metastatic NETs of unknown primary site. PDX-1 was negative in all carcinoids of the colon and sigmoid (0/5), ileum and jejunum (0/24), lung (0/40), trachea (0/2), larynx (0/2), Merkel's cell carcinoma (0/14), breast (0/3), bladder (0/1), as well as MTC (0/6), APCC (0/4), and paragangliomas (0/6). PDX-1-positive non-NETs included 81.8% (18/22) of adenocarcinomas (AC) and all serous cystic, mucinous cystic, intraductal and acinar cell tumors of the pancreas (4/4, 3/3, 2/2, and 3/3), 57.1% of AC (8/14) and 83.3% of signet ring cell carcinomas of the stomach (10/12), 56.2% AC of the bowel (9/17), bladder cancer (1/1). PDX-1 was negative in all anaplastic cancers (0/2) and solid pseudopapillary tumors of the pancreas (0/20), cancers of the lung (0/11), kidney (0/4), breast (0/3), and adrenal glands (0/2).

CONCLUSION

The expression of PDX-1 is very specific for most digestive tract NETs and non-NETs. Pancreatic ductal and acinar cell tumors and gastric signet ring cell carcinomas are most commonly PDX-1-positive. Most tumors that do not originate from the digestive tract have a PDX-1 negative immunophenotype.

Alpha-Mangostin Improves Insulin Secretion and Protects INS-1 Cells from Streptozotocin-Induced Damage

Alpha (α)-mangostin, a yellow crystalline powder with a xanthone core structure, is isolated from mangosteen (Garcinia mangostana), which is a tropical fruit of great nutritional value. The aim of the present study was to investigate the anti-diabetic effects of α-mangostin and to elucidate the molecular mechanisms underlying its effect on pancreatic beta (β)-cell dysfunction. To assess the effects of α-mangostin on insulin production, rat pancreatic INS-1 cells were treated with non-toxic doses of α-mangostin (1⁻10 μM) and its impact on insulin signaling was examined by Western blotting. In addition, the protective effect of α-mangostin against pancreatic β-cell apoptosis was verified by using the β-cell toxin streptozotocin (STZ). Our results showed that α-mangostin stimulated insulin secretion in INS-1 cells by activating insulin receptor (IR) and pancreatic and duodenal homeobox 1 (Pdx1) followed by phosphorylation of phospho-phosphatidylinositol-3 kinase (PI3K), Akt, and extracellular signal regulated kinase (ERK) signaling cascades, whereas it inhibited the phosphorylation of insulin receptor substrate (IRS-1) (Ser1101). Moreover, α-mangostin was found to restore the STZ-induced decrease in INS-1 cell viability in a dose-dependent manner. In addition, treatment of INS-1 cells with 50 μM STZ resulted in an increase in intracellular reactive oxygen species (ROS) levels, which was represented by the fluorescence intensity of 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). This oxidative stress was decreased by co-treatment with 5 μM α-mangostin. Similarly, marked increases in the phosphorylation of P38, c-Jun N-terminal kinase (JNK), and cleavage of caspase-3 by STZ were decreased significantly by co-treatment with 5 μM α-mangostin. These results suggest that α-mangostin is capable of improving insulin secretion in pancreatic β-cells and protecting cells from apoptotic damage.

HECT E3 Ubiquitin Ligase Itch Functions as a Novel Negative Regulator of Gli-Similar 3 (Glis3) Transcriptional Activity

The transcription factor Gli-similar 3 (Glis3) plays a critical role in the generation of pancreatic ß cells and the regulation insulin gene transcription and has been implicated in the development of several pathologies, including type 1 and 2 diabetes and polycystic kidney disease. However, little is known about the proteins and posttranslational modifications that regulate or mediate Glis3 transcriptional activity. In this study, we identify by mass-spectrometry and yeast 2-hybrid analyses several proteins that interact with the N-terminal region of Glis3. These include the WW-domain-containing HECT E3 ubiquitin ligases, Itch, Smurf2, and Nedd4. The interaction between Glis3 and the HECT E3 ubiquitin ligases was verified by co-immunoprecipitation assays and mutation analysis. All three proteins interact through their WW-domains with a PPxY motif located in the Glis3 N-terminus. However, only Itch significantly contributed to Glis3 polyubiquitination and reduced Glis3 stability by enhancing its proteasomal degradation. Itch-mediated degradation of Glis3 required the PPxY motif-dependent interaction between Glis3 and the WW-domains of Itch as well as the presence of the Glis3 zinc finger domains. Transcription analyses demonstrated that Itch dramatically inhibited Glis3-mediated transactivation and endogenous Ins2 expression by increasing Glis3 protein turnover. Taken together, our study identifies Itch as a critical negative regulator of Glis3-mediated transcriptional activity. This regulation provides a novel mechanism to modulate Glis3-driven gene expression and suggests that it may play a role in a number of physiological processes controlled by Glis3, such as insulin transcription, as well as in Glis3-associated diseases.

Pancreatic Islet APJ Deletion Reduces Islet Density and Glucose Tolerance in Mice

Protection and replenishment of a functional pancreatic β-cell mass (BCM) are key goals of all diabetes therapies. Apelin, a small regulatory peptide, is the endogenous ligand for the apelin receptor (APJ) receptor. The apelin-APJ signaling system is expressed in rodent and human islet cells. Apelin exposure has been shown to inhibit and to stimulate insulin secretion. Our aim was to assess the influence of a selective APJ deletion in pancreatic islet cells on islet homeostasis and glucose tolerance in mice. Cre-LoxP strategy was utilized to mediate islet APJ deletion. APJ deletion in islet cells (APJ(Δislet)) resulted in a significantly reduced islet size, density and BCM. An ip glucose tolerance test showed significantly impaired glucose clearance in APJ(Δislet) mice. APJ(Δislet) mice were not insulin resistant and in vivo glucose-stimulated insulin secretion was reduced modestly. In vitro glucose-stimulated insulin secretion showed a significantly reduced insulin secretion by islets from APJ(Δislet) mice. Glucose clearance in response to ip glucose tolerance test in obese APJ(Δislet) mice fed a chronic high-fat (HF) diet, but not pregnant APJ(Δislet) mice, was impaired significantly. In addition, the obesity-induced adaptive elevations in mean islet size and fractional islet area were reduced significantly in obese APJ(Δislet) mice when compared with wild-type mice. Together, these findings demonstrate a stimulatory role for the islet cell apelin-APJ signaling axis in regulation of pancreatic islet homeostasis and in metabolic induced β-cell hyperplasia. The results indicate the apelin-APJ system can be exploited for replenishment of BCM.