A novel monoclonal antibody against DOG1 is a sensitive and specific marker for gastrointestinal stromal tumors. Am J Surg Pathol. 2008;32:210-218. [PMID: 18223323 DOI: 10.1097/pas.0b013e3181238cec]

Functions of volume-sensitive and calcium-activated chloride channels

The review describes molecular and functional properties of the volume regulated anion channel and Ca(2+)-dependent Cl(-) channels belonging to the anoctamin family with emphasis on physiological importance of these channels in regulation of cell volume, cell migration, cell proliferation, and programmed cell death. Finally, we discuss the role of Cl(-) channels in various diseases.

The Ca2+-activated Cl- channel ANO1/TMEM16A regulates primary ciliogenesis

The Ca²⁺-activated Cl⁻ channel ANO1/TMEM16A is located in the primary cilium, and blocking it pharmacologically or knocking it down with shRNA interferes with ciliogenesis. Before ciliogenesis, the channel is organized into a torus-shaped structure (the “nimbus”) enriched in proteins required for ciliogenesis.

Many cells possess a single, nonmotile, primary cilium highly enriched in receptors and sensory transduction machinery that plays crucial roles in cellular morphogenesis. Although sensory transduction requires ion channels, relatively little is known about ion channels in the primary cilium (with the exception of TRPP2). Here we show that the Ca²⁺-activated Cl⁻ channel anoctamin-1 (ANO1/TMEM16A) is located in the primary cilium and that blocking its channel function pharmacologically or knocking it down with short hairpin RNA interferes with ciliogenesis. Before ciliogenesis, the channel becomes organized into a torus-shaped structure (“the nimbus”) enriched in proteins required for ciliogenesis, including the small GTPases Cdc42 and Arl13b and the exocyst complex component Sec6. The nimbus excludes F-actin and coincides with a ring of acetylated microtubules. The nimbus appears to form before, or independent of, apical docking of the mother centriole. Our data support a model in which the nimbus provides a scaffold for staging of ciliary components for assembly very early in ciliogenesis and chloride transport by ANO1/TMEM16A is required for the genesis or maintenance of primary cilia.

Structure and function of TMEM16 proteins (anoctamins)

TMEM16 proteins, also known as anoctamins, are involved in a variety of functions that include ion transport, phospholipid scrambling, and regulation of other membrane proteins. The first two members of the family, TMEM16A (anoctamin-1, ANO1) and TMEM16B (anoctamin-2, ANO2), function as Ca2+-activated Cl- channels (CaCCs), a type of ion channel that plays important functions such as transepithelial ion transport, smooth muscle contraction, olfaction, phototransduction, nociception, and control of neuronal excitability. Genetic ablation of TMEM16A in mice causes impairment of epithelial Cl- secretion, tracheal abnormalities, and block of gastrointestinal peristalsis. TMEM16A is directly regulated by cytosolic Ca2+ as well as indirectly by its interaction with calmodulin. Other members of the anoctamin family, such as TMEM16C, TMEM16D, TMEM16F, TMEM16G, and TMEM16J, may work as phospholipid scramblases and/or ion channels. In particular, TMEM16F (ANO6) is a major contributor to the process of phosphatidylserine translocation from the inner to the outer leaflet of the plasma membrane. Intriguingly, TMEM16F is also associated with the appearance of anion/cation channels activated by very high Ca2+ concentrations. Furthermore, a TMEM16 protein expressed in Aspergillus fumigatus displays both ion channel and lipid scramblase activity. This finding suggests that dual function is an ancestral characteristic of TMEM16 proteins and that some members, such as TMEM16A and TMEM16B, have evolved to a pure channel function. Mutations in anoctamin genes (ANO3, ANO5, ANO6, and ANO10) cause various genetic diseases. These diseases suggest the involvement of anoctamins in a variety of cell functions whose link with ion transport and/or lipid scrambling needs to be clarified.

Role of anoctamins in cancer and apoptosis

Anoctamin 1 (TMEM16A, Ano1) is a recently identified Ca(2+)-activated chloride channel and a member of a large protein family comprising 10 paralogues. Before Ano1 was identified as a chloride channel protein, it was known as the cancer marker DOG1. DOG1/Ano1 is expressed in gastrointestinal stromal tumours (GIST) and particularly in head and neck squamous cell carcinoma, at very high levels never detected in other tissues. It is now emerging that Ano1 is part of the 11q13 locus, amplified in several types of tumour, where it is thought to augment cell proliferation, cell migration and metastasis. Notably, Ano1 is upregulated through histone deacetylase (HDAC), corresponding to the known role of HDAC in HNSCC. As Ano1 does not enhance proliferation in every cell type, its function is perhaps modulated by cell-specific factors, or by the abundance of other anoctamins. Thus Ano6, by regulating Ca(2+)-induced membrane phospholipid scrambling and annexin V binding, supports cellular apoptosis rather than proliferation. Current findings implicate other cellular functions of anoctamins, apart from their role as Ca(2+)-activated Cl(-) channels.

Nuclear expression of STAT6 distinguishes solitary fibrous tumor from histologic mimics

Solitary fibrous tumor (SFT) is composed of spindled to ovoid cells in a patternless architecture with prominent stromal collagen and hemangiopericytoma-like vessels. Some tumors show hypercellularity, nuclear atypia, and significant mitotic activity; the latter feature in particular often portends an aggressive clinical course. SFT can sometimes be difficult to distinguish from other benign mesenchymal tumors and sarcomas. The most characteristic (albeit nonspecific) immunohistochemical finding in SFT is CD34 expression. A NAB2-STAT6 gene fusion, resulting in a chimeric protein in which a repressor domain of NGFI-A binding protein 2 (EGR1 binding protein 2) (NAB2) is replaced with a carboxy-terminal transactivation domain from signal transducer and activator of transcription 6, interleukin-4 induced (STAT6), was recently identified as a consistent finding in SFT. However, as these genes are located in close proximity on 12q13, this fusion can only rarely be detected by conventional chromosomal banding or fluorescence in situ hybridization analysis. Nuclear expression of the carboxy terminal part of STAT6 is a consistent finding in SFT of the meninges (so-called 'meningeal hemangiopericytoma'). We investigated STAT6 expression by immunohistochemistry in SFTs and other soft tissue tumors arising outside the central nervous system to validate the diagnostic utility of this novel marker. Whole-tissue sections of 231 tumors were evaluated, including 60 cases of SFT as well as other benign and malignant mesenchymal neoplasms and sarcomatoid mesotheliomas. Fifty-nine of 60 SFT cases (98%) showed nuclear expression of STAT6, which was usually diffuse and intense. All other tumor types were negative for STAT6, except for three dedifferentiated liposarcomas and one deep fibrous histiocytoma, which showed weak staining. In conclusion, STAT6 is a highly sensitive and almost perfectly specific immunohistochemical marker for SFT and can be helpful to distinguish this tumor type from histologic mimics.

Prognostic analysis of gastric gastrointestinal stromal tumor with synchronous gastric cancer

BACKGROUND

Many patients with gastric gastrointestinal stromal tumor (GIST) and synchronous gastric cancer have been described, most in single case studies. We retrospectively investigated the clinicopathologic features and prognostic effects of gastric GIST in patients with synchronous gastric cancer.

METHODS

The study enrolled 170 patients with gastric GIST, who had undergone complete surgical resection (R0) from January 2000 to December 2011. Forty-two patients had synchronous gastric cancer (CA Group), whereas 128 did not (Non-CA Group). The clinicopathologic features and potential prognostic factors in the two groups were compared.

RESULTS

Patients in the CA Group had more obvious symptoms, but a lower rate of preoperative diagnosis of gastric GIST (P <0.05). The two groups differed significantly in gender, age, greatest tumor diameter, risk stratification, tumor-associated ulcers, and CD117 and CD34 expression (P <0.05 each). Univariate analysis showed that age, risk stratification, postoperative oral imatinib and synchronous gastric cancer were predictive factors of survival (P <0.05). Cox regression analysis showed that risk stratification, postoperative oral imatinib and synchronous gastric cancer were independent predictors of survival (P <0.05). Stratified analysis showed that the 5-year overall survival rate was lower in patients with synchronous gastric cancer than in those without synchronous gastric cancer.

CONCLUSIONS

Gastric GIST with synchronous gastric cancer had a lower rate of preoperative diagnosis, with correct diagnosis often missed. Survival, however, depended primarily on the gastric cancer.

Transmembrane protein with unknown function 16A overexpression promotes glioma formation through the nuclear factor-κB signaling pathway

Ion channels have been suggested to be important in the development and progression of tumors, however, chloride channels have rarely been analyzed in tumorigenesis. More recently, transmembrane protein with unknown function 16A (TMEM16A), hypothesized to be a candidate calcium‑activated Cl‑ channel, has been found to be overexpressed in a number of tumor types. Although several studies have implicated the overexpression of TMEM16A in certain tumor types, the exact role of TMEM16A in gliomas and the underlying mechanisms in tumorigenesis, remain poorly understood. In the present study, the role of TMEM16A in gliomas and the potential underlying mechanisms were analyzed. TMEM16A was highly abundant in various grades of gliomas and cultured glioma cells. Knockdown of TMEM16A suppressed cell proliferation, migration and invasion. Furthermore, nuclear factor‑κB (NF‑κB) was activated by overexpression of TMEM16A. In addition, TMEM16A regulated the expression of NF‑κB‑mediated genes, including cyclin D1, cyclin E and c‑myc, involved in cell proliferation, and matrix metalloproteinases (MMPs)‑2 and MMP‑9, which are associated with the migration and invasion of glioma cells. Collectively, results of the present study provide evidence for the involvement of TMEM16A in gliomas and the potential mechanism through which TMEM16A promotes glioma formation.

Differential clinical and pathological characteristics of esophageal stromal tumors and leiomyomata

The objective of the study was to assess the differences in clinical and pathological characteristics between esophageal stromal tumor and leiomyoma. Data from 93 esophageal stromal tumors and leiomyomata cases were retrospectively analyzed, including clinical symptoms, endoscopic features, pathological characteristics, immunohistochemistry (IHC), and treatment. All cases underwent endoscopic ultrasonography examination before treatment. Lesions arising from the muscularis mucosa were resected by endoscopic mucosal resection or endoscopic submucosal dissection. Lesions arising from the muscularis propria were resected by surgery. All specimens were examined by IHC. Patients were followed up after endoscopic mucosal resection or endoscopic submucosal dissection. No difference was observed in clinical symptoms and endoscopic features between the two groups. Endoscopic ultrasonography demonstrated all lesions to be hypoechoic and well circumscribed. Most lesions >2 cm had heterogeneous internal ultrasound signal. In esophageal stromal tumor, 100% (29/29) were CD117-positive and DOG-1-positive; 72.4% (21/29) and 51.7% (15/29) were CD34-positive and smooth muscle actin-positive, respectively. In esophageal leiomyomata, 100% (64/64) were smooth muscle actin-positive and desmin-positive; 100% were CD117-negative and DOG-1-negative. No local recurrence was detected in followed up patients (n = 49) after an average of 1.8 years (1.0-3.0 years). IHC analyses are important for distinguishing esophageal stromal tumor from leiomyoma. Early endoscopic resection is an effective treatment option for esophageal stromal tumors >1 cm.

Novel uses of immunohistochemistry in the diagnosis and classification of soft tissue tumors

Immunohistochemistry plays a key role in the diagnosis of soft tissue tumors. Until recently, however, the primary purpose of immunohistochemistry in this context was simply to attempt to demonstrate a line of differentiation. Unfortunately, most traditional markers (predominantly directed against cytoplasmic determinants) show relatively limited specificity. Over the last decade or so, much more specific immunohistochemical markers for soft tissue tumors have been developed. This review will provide an update of some of the most useful new diagnostic markers, which are significantly changing clinical practice for surgical pathologists, separated into three general categories: (1) lineage-restricted transcription factors, (2) protein correlates of molecular alterations, and (3) diagnostic markers identified by gene expression profiling.

DOG1 is useful for diagnosis of KIT-negative gastrointestinal stromal tumor of stomach

Approximately 80%-95% of gastrointestinal stromal tumors (GISTs) show positive staining for KIT, while the other 5%-20% show negative staining. If the tumor is negative for KIT, but is positive for CD34, a histological diagnosis is possible. However, if the tumor is negative for KIT, CD34, S-100, and SMA, a definitive diagnosis is often challenging. Recently, Discovered on GIST-1 (DOG1) has received considerable attention as a useful molecule for the diagnosis of GIST. DOG1, a membrane channel protein, is known to be overexpressed in GIST. Because the sensitivity and specificity of DOG1 are higher than those of KIT, positive staining for DOG1 has been reported, even in KIT-negative GISTs. KIT-negative GISTs most commonly arise in the stomach and are mainly characterized by epithelioid features histologically. We describe our experience with a rare case of a KIT-negative GIST of the stomach that was diagnosed by positive immunohistochemical staining for DOG1 in a patient who presented with severe anemia. Our findings suggest that immunohistochemical staining for DOG1, in addition to gene analysis, is useful for the diagnosis of KIT-negative tumors that are suspected to be GISTs.

Immunohistochemistry of soft tissue tumours - review with emphasis on 10 markers

Immunohistochemistry is an integral component in the proper analysis of soft tissue tumours, and a simple panel of six markers is useful in practical triage: CD34, desmin, epithelial membrane antigen (EMA), keratin cocktail AE1/AE3, S100 protein and alpha smooth muscle actin (SMA). These markers frequently assist in the differential diagnosis of fibroblastic, myoid, nerve sheath and perineurial cell tumours, synovial and epithelioid sarcoma and others. However, they all are multispecific, so that one has to be cognizant of their distribution in normal and neoplastic tissues. Four additional useful markers for specific tumour types are discussed here: CD31 and ERG for vascular endothelial tumours, and KIT and DOG1/Ano-1 for gastrointestinal stromal tumours (GISTs). However, hardly any marker is totally monospecific for any one type of tumour. Furthermore, variably lineage-specific markers do not usually distinguish between benign and malignant proliferations, so that this distinction has to be made on histological grounds. Immunohistochemical evaluation is most useful, efficient and cost-effective when used in the context of careful histological evaluation by an experienced pathologist, aware of all diagnostic entities and their histological spectra. Additional diagnostic steps that must be considered in difficult cases include clinicoradiological correlation and additional sampling of remaining wet tissue, if possible.

Soft tissue sarcomas--new approaches to diagnosis and classification

The study of sarcoma pathology is a rapidly evolving field. The continued refinement of classic diagnostic techniques in conjunction with the molecular diagnostics has resulted in an abundance of data regarding this diverse and rare group of tumors. We anticipate that cutting edge technology including next generation sequencing will continue to further our understanding of saromagenesis and enable more precise classification and diagnosis of sarcomas in the future.

Newly Available Antibodies With Practical Applications in Surgical Pathology

Selected antibodies that have become available in recent years and have applications in diagnostic pathology are discussed. They include antibodies that are organ-related, provide information on cellular differentiation or histogenetic type, have predictive value in tumors, and highlight infective agents. PAX8 (paired box gene 8) is a marker expressed in the lower female genital tract, thyroid, and kidney and their tumors. Napsin A is expressed in the lung and kidney and is an alternative marker for pulmonary adenocarcinoma. Arginase A is a sensitive and specific marker for liver tumors. ERG (Ets-related gene) is an excellent marker for endothelium and vascular tumors as well as prostatic cancer (about 50% of cases). SOX10 (SRY-related HMG box) is expressed predominantly in melanocytic and Schwann cells and the corresponding tumors. DOG1 (discovered on GIST 1) is an excellent marker for gastrointestinal stromal tumor (GIST) and acinic cell carcinoma. OCT3/4 is a pan–germ cell tumor marker, except yolk sac tumor. SALL4 is positive in various types of germ cell tumors, including yolk sac tumor. MUC4 (mucin-related antigen 4) is a sensitive and specific marker for low-grade fibromyxoid sarcoma. Langerin is a specific marker for Langerhans cells and their tumors. SOX11 is a sensitive marker for mantle cell lymphoma. New generation antibodies against anaplastic lymphoma kinase (ALK) are required to reliably demonstrate ALK gene translocation in pulmonary carcinomas. Lack of expression of succinate dehydrogenase B is seen in paragangliomas of the hereditary form and in the pediatric type of GIST. Antibodies against Trepenoma pallidum can facilitate the diagnosis of syphilis, whereas those against SV40 (simian virus 40) are helpful for diagnosis of BK virus infection and progressive multifocal leukoencephalopathy.

Anoctamin 1 induces calcium-activated chloride secretion and proliferation of renal cyst-forming epithelial cells

Polycystic kidney diseases are characterized by multiple bilateral renal cysts that gradually enlarge and lead to a decline in renal function. Cyst enlargement is driven by transepithelial chloride secretion, stimulated by enhanced levels of cyclic adenosine monophosphate, which activates apical cystic fibrosis transmembrane conductance regulator chloride channels. However, chloride secretion by calcium-dependent chloride channels, activated through stimulation of purinergic receptors, also has a major impact. To identify the molecular basis of calcium-dependent chloride secretion in cyst expansion, we determined the role of anoctamin 1 and 6, two recently discovered calcium-activated chloride channels both of which are expressed in epithelial cells. We found that anoctamin 1, which plays a role in epithelial fluid secretion and proliferation, is strongly expressed in principal-like MDCK cells (PLCs) forming cysts within a collagen matrix, in an embryonic kidney cyst model, and in human autosomal dominant polycystic kidney disease tissue. Knockdown of anoctamin 1 but not anoctamin 6 strongly diminished the calcium-dependent chloride secretion of PLCs. Moreover, two inhibitors of anoctamin ion channels, tannic acid and a more selective inhibitor of anoctamin 1, significantly inhibited PLC cyst growth and cyst enlargement in an embryonic kidney cyst model. Knockdown of ANO1 by morpholino analogs also attenuated embryonic cyst growth. Thus, calcium-activated chloride secretion by anoctamin 1 appears to be a crucial component of renal cyst growth.

Diagnostic significance of DOG-1 and PKC-θ expression and c-Kit/PDGFRA mutations in gastrointestinal stromal tumours

OBJECTIVE

To investigate discovered on gastrointestinal stromal tumor (GIST)-1 (DOG-1) and protein kinase C-θ (PKC-θ) expression in a series of GISTs and determine the sensitivity, specificity, and diagnostic value of these two antigens.

METHODS

Immnunohistochemistry (IHC) was used to detect CD117, DOG-1, PKC-θ, CD34, Ki-67, α-smooth muscle actin (SMA), S100, and Desmin expression in 147 GISTs and 51 non-GISTs. c-Kit gene (exons 9, 11, 13, and 17) and platelet-derived growth factor receptor-alpha (PDGFRA) gene (exons 12 and 18) mutations were also detected.

RESULTS

About 94.5% GISTs were CD117 positive, 96% were DOG-1 positive, and 90.5% were PKC-θ positive. DOG-1 had a specificity of 100%, while CD117 and PKC-θ had a specificity of 90% and 80%, respectively. There was no significant difference between DOG-1 and PKC-θ expressions when compared to CD117 expression. In 30 out of 42 (71.5%) GISTs, a c-Kit gene mutation was found, and in 3 out of 42 cases (7%), PDGFRA was mutated. Wild-type c-Kit/PDGFRA genes accounted for 21.5% (9/42). Most c-Kit gene mutations were found to be located at exon 11, mainly as in-frame deletions. Mutations in exon 9 were all missense mutations. Most PDGFRA gene mutations were found in exon 18, codon 842. c-Kit gene mutations in exons 13 and 17, and the PDGFRA gene mutation in exon 12 were not detected.

CONCLUSIONS

Compared to CD117, DOG-1 is a biomarker with higher sensitivity and specificity. The combination of CD117 and DOG-1 can be used to improve the diagnosis of GIST. Although PKC-θ has a lower specificity than DOG-1, it can be a useful biomarker, especially in CD117(-) and/or DOG-1(-) cases.

Mesenchymal Tumors of the Gastrointestinal Tract Other than GIST

Mesenchymal tumors involve the gastrointestinal (GI) tract more frequently than other visceral organs. Many such tumors are small, and are benign and increasingly being detected incidentally during colonoscopic screening. Some tumors show distinctive features at this site, such as schwannoma and clear cell sarcoma-like tumor of the GI tract. Without knowledge of these features, recognition of these tumor types can be difficult. This reviews addresses recent developments and diagnostic features of mesenchymal tumors of the GI tract other than gastrointestinal stromal tumor (GIST).

TMEM16A alternative splicing coordination in breast cancer

Background

TMEM16A, also known as Anoctamin-1, is a calcium-activated chloride channel gene overexpressed in many tumors. The role of TMEM16A in cancer is not completely understood and no data are available regarding the potential tumorigenic properties of the multiple isoforms generated by alternative splicing (AS).

Methods

We evaluated TMEM16A AS pattern, isoforms distribution and Splicing Coordination (SC), in normal tissues and breast cancers, through a semi-quantitative PCR-assay that amplifies transcripts across three AS exons, 6b, 13 and 15.

Results

In breast cancer, we did not observe an association either to AS of individual exons or to specific TMEM16A isoforms, and induced expression of the most common isoforms present in tumors in the HEK293 Flp-In Tet-ON system had no effect on cellular proliferation and migration. The analysis of splicing coordination, a mechanism that regulates AS of distant exons, showed a preferential association of exon 6b and 15 in several normal tissues and tumors: isoforms that predominantly include exon 6b tend to exclude exon 15 and vice versa. Interestingly, we found an increase in SC in breast tumors compared to matched normal tissues.

Conclusions

As the different TMEM16A isoforms do not affect proliferation or migration and do not associate with tumors, our results suggest that the resulting channel activities are not directly involved in cell growth and motility. Conversely, the observed increase in SC in breast tumors suggests that the maintenance of the regulatory mechanism that coordinates distant alternative spliced exons in multiple genes other than TMEM16A is necessary for cancer cell viability.

Clinicopathological features of primary leiomyosarcoma of the gastrointestinal tract following recognition of gastrointestinal stromal tumours

AIMS

We aimed to elucidate the clinicopathological and immunohistochemical features of leiomyosarcoma (LMS) of the gastrointestinal (GI) tract.

METHODS AND RESULTS

We encountered seven cases of GI-LMS in the colon (n = 4), rectum (n = 1), jejunum (n = 1) and stomach (n = 1). They ranged from 1 to 25 cm (median, 8.5 cm) in size and had high mitotic counts (median 38 per 50 high-power fields). Morphologically, the tumours were composed mainly of spindle cells with eosinophilic cytoplasm and various degrees of nuclear atypia and pleomorphism. Immunohistochemically, the tumours were positive for α-smooth muscle actin (86%), muscle-specific actin (71%), desmin (86%), calponin (71%), h-caldesmon (57%) and smoothelin (71%). All were negative for KIT, CD34, protein kinase C theta and DOG1. Local recurrence and distant metastasis occurred in one and three patients, respectively. We then reviewed 55 cases of GI-LMS from the era following the recognition of gastrointestinal stromal tumours. Among 29 of 55 cases for whom follow-up information was available, the estimated 5-year overall survival rate was 51.6%; tumour size ≥5 cm was correlated significantly with shorter overall survival time (P = 0.0016), while mitotic count (≥50 or ≥100 per 50 high-power fields) proved to be no prognostic factor.

CONCLUSIONS

GI-LMSs have distinctive clinicopathological and immunohistochemical features and exhibit aggressive biological behaviour.

A case report: endoscopic enucleation of gastrointestinal stromal tumor of the ampulla of Vater

OBJECTIVE

To report a case of endoscopic enucleation of a gastrointestinal stromal tumor of the ampulla of Vater.

DESIGN

The tumor resection was performed by needle knife endoscopic submucosal dissection.

RESULTS

The tumor was resected completely without serious complications and the patient recovered rapidly.

CONCLUSION

Endoscopic enucleation may be an alternative treatment for gastrointestinal stromal tumors of the ampulla of Vater for patients who fulfill certain requirements.

Rare presentation of a gastrointestinal stromal tumor with spontaneous esophageal perforation: A case report

INTRODUCTION

Gastrointestinal stromal tumors (GISTs) of the alimentary canal are malignant tumors with <1% of cases diagnosed in esophagus. These cases require special consideration given their close proximity to vital structures and propensity to be highly aggressive. Management of patients with GISTs has been transformed since the introduction of tyrosine kinase inhibitors. In this report, we present an unusual case of GIST with spontaneous esophageal perforation.

PRESENTATION OF CASE

A 39-year-old Caucasian male presented to our hospital with complaints of severe chest and abdominal pain. A diagnostic chest radiograph revealed a moderate right-sided pleural effusion. Subsequently, an esophagram demonstrated a perforation proximal to an elongated stricture in the distal esophagus. A left thoracotomy was performed whereby a large mediastinal mass firmly attached to the esophagus and gastroesophageal junction was encountered. The neoplasm involved proximal one-third of the stomach and perforated into the right hemithorax. Histopathological evaluation of the tumor led to a diagnosis of GIST.

DISCUSSION

GISTs of the gastroesophageal junction are uncommon and may rarely present with esophageal perforation. The standard of care for treating GIST at present includes tyrosine kinase inhibitors. This pharmacologic agent, along with improved surgical techniques and understanding of molecular markers for accurate diagnosis, will assuredly continue to improve overall survival of patients with GISTs.

CONCLUSION

When stricture or achalasia is detected on imaging, GIST should be considered in the differential diagnosis for individual patients. Additionally, chest and abdomen CT scans of may be performed to confirm presence of a tumor mass, thereby ruling out achalasia.

DOG1 regulates growth and IGFBP5 in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GIST) are characterized by activating mutations of KIT or platelet-derived growth factor receptor α(PDGFRA), which can be therapeutically targeted by tyrosine kinase inhibitors (TKI) such as imatinib. Despite long-lasting responses, most patients eventually progress after TKI therapy. The calcium-dependent chloride channel DOG1 (ANO1/TMEM16A), which is strongly and specifically expressed in GIST, is used as a diagnostic marker to differentiate GIST from other sarcomas. Here, we report that loss of DOG1 expression occurs together with loss of KIT expression in a subset of GIST resistant to KIT inhibitors, and we illustrate the functional role of DOG1 in tumor growth, KIT expression, and imatinib response. Although DOG1 is a crucial regulator of chloride balance in GIST cells, we found that RNAi-mediated silencing or pharmacologic inhibition of DOG1 did not alter cell growth or KIT signaling in vitro. In contrast, DOG1 silencing delayed the growth of GIST xenografts in vivo. Expression profiling of explanted tumors after DOG1 blockade revealed a strong upregulation in the expression of insulin-like growth factor-binding protein 5 (IGFBP5), a potent antiangiogenic factor implicated in tumor suppression. Similar results were obtained after selection of imatinib-resistant DOG1- and KIT-negative cells derived from parental DOG1 and KIT-positive GIST cells, where a 5,000-fold increase in IGFBP5 mRNA transcripts were documented. In summary, our findings establish the oncogenic activity of DOG1 in GIST involving modulation of IGF/IGF receptor signaling in the tumor microenvironment through the antiangiogenic factor IGFBP5.

Evidence for Ca(2+)-regulated ATP release in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are thought to originate from the electrically active pacemaker cells of the gastrointestinal tract. Despite the presence of synaptic-like vesicles and proteins involved in cell secretion it remains unclear whether GIST cells possess regulated release mechanisms. The GIST tumor cell line GIST882 was used as a model cell system, and stimulus-release coupling was investigated by confocal microscopy of cytoplasmic free Ca(2+) concentration ([Ca(2+)]i), flow cytometry, and luminometric measurements of extracellular ATP. We demonstrate that GIST cells have an intact intracellular Ca(2+)-signaling pathway that regulates ATP release. Cell viability and cell membrane integrity was preserved, excluding ATP leakage due to cell death and suggesting active ATP release. The stimulus-secretion signal transduction is at least partly dependent on Ca(2+) influx since exclusion of extracellular Ca(2+) diminishes the ATP release. We conclude that measurements of ATP release in GISTs may be a useful tool for dissecting the signal transduction pathway, mapping exocytotic components, and possibly for the development and evaluation of drugs. Additionally, release of ATP from GISTs may have importance for tumor tissue homeostasis and immune surveillance escape.

Anti-KIT monoclonal antibody inhibits imatinib-resistant gastrointestinal stromal tumor growth

Gastrointestinal stromal tumor (GIST) is the most common sarcoma of the gastrointestinal tract and arises from the interstitial cells of Cajal. It is characterized by expression of the receptor tyrosine kinase CD117 (KIT). In 70-80% of GIST cases, oncogenic mutations in KIT are present, leading to constitutive activation of the receptor, which drives the proliferation of these tumors. Treatment of GIST with imatinib, a small-molecule tyrosine kinase inhibitor, inhibits KIT-mediated signaling and initially results in disease control in 70-85% of patients with KIT-positive GIST. However, the vast majority of patients eventually develop resistance to imatinib treatment, leading to disease progression and posing a significant challenge in the clinical management of these tumors. Here, we show that an anti-KIT monoclonal antibody (mAb), SR1, is able to slow the growth of three human GIST cell lines in vitro. Importantly, these reductions in cell growth were equivalent between imatinib-resistant and imatinib-sensitive GIST cell lines. Treatment of GIST cell lines with SR1 reduces cell-surface KIT expression, suggesting that mAb-induced KIT down-regulation may be a mechanism by which SR1 inhibits GIST growth. Furthermore, we also show that SR1 treatment enhances phagocytosis of GIST cells by macrophages, indicating that treatment with SR1 may enhance immune cell-mediated tumor clearance. Finally, using two xenotransplantation models of imatinib-sensitive and imatinib-resistant GIST, we demonstrate that SR1 is able to strongly inhibit tumor growth in vivo. These results suggest that treatment with mAbs targeting KIT may represent an alternative, or complementary, approach for treating GIST.

Gene expression of the IGF pathway family distinguishes subsets of gastrointestinal stromal tumors wild type for KIT and PDGFRA

Gastrointestinal stromal tumors (GISTs) arise from the interstitial cells of Cajal (ICCs) and are the most common mesenchymal neoplasm of the gastrointestinal tract. While the majority of GISTs harbor activating mutations in either the v-kit Hardy-Zuckerman feline sarcoma viral oncogene homolog (KIT) or platelet-derived growth factor receptor alpha (PDGFRA) tyrosine kinases, approximately 10–15% of adult GISTs and 85% of pediatric GISTs lack such mutations. These “wild-type” GISTs have been reported to express high levels of the insulin-like growth factor 1 receptor (IGF1R), and IGF1R-targeted therapy of wild-type GISTs is being evaluated in clinical trials. However, it is not clear that all wild-type GISTs express IGF1R, because studies to date have predominantly focused on a particular subtype of gastric wild-type GIST that is deficient in the mitochondrial succinate dehydrogenase (SDH) complex. This study of a series of 136 GISTs, including 72 wild-type specimens, was therefore undertaken to further characterize wild-type GIST subtypes based on the relative expression of transcripts encoding IGF1R. Additional transcripts relevant to GIST biology were also evaluated, including members of the IGF-signaling pathway (IGF1, IGF2, and insulin receptor [INSR]), neural markers (CDH2[CDH: Cadherin], neurofilament, light polypeptide, LHX2 [LHX: LIM homeobox], and KIRREL3 [KIRREL: kin of IRRE like]), KIT, PDGFRA, CD34, and HIF1A. Succinate dehydrogenase complex, subunit B protein expression was also assessed as a measure of SDH complex integrity. In addition to the previously described SDH-deficient, IGF1R^high wild-type GISTs, other SDH-intact wild-type subpopulations were defined by high relative expression of IGF1R, neural markers, IGF1 and INSR, or low IGF1R coupled with high IGF2. These results underscore the complexity and heterogeneity of wild-type GISTs that will need to be factored into molecularly-targeted therapeutic strategies.

Primary gastrointestinal stromal tumors: Current advances in diagnostic biomarkers, prognostic factors and management of its duodenal location

Gastrointestinal stromal tumors (GIST) constitute 1-3% of all gastrointestinal malignancies and is the most common mesenchymal tumor of the gastrointestinal tract. Although GIST were first described in the literature in the year 1941, important advances of kit mutation and tyrosine kinase inhibitors were not made to understand and manage GIST until the last decade. Here current advances in research of possible cellular origin, diagnostic biomarkers and prognostic factors of primary GIST are reviewed, and the management of primary duodenal GIST is focused on due to its specific location. It is possible that personalized assessment and therapy will turn out to be another milestone for primary GIST.

Expression of DOG1, CD117 and PDGFRA in gastrointestinal stromal tumors and correlations with clinicopathology

OBJECTIVE

To discuss the significance of DOG1, CD117 and PDGFRA in the diagnosis of gastrointestinal stromal tumors (GISTs), and analyze their correlations with clinicopathological features and risk ranking.

METHOD

DOG1, CD117 and PDGFRA were detected with IHC Envision ldpe-g-nvp in 63 GISTs and 43 cases of non-GISTs, and analyzed for relations with clinicopathological factors (gender, age, location, tumor size, mitotic phase, histology) and risk degree.

RESULTS

The positive expression rate of DOG1, CD117 and PDGFRA in GISTs was 84.1% (53/63), 90.5% (57/63), 53.2% (33/63), respectively. Among the 6 CD117 negative cases, all were DOG1 positive and 5 were PDGFRA positive. Rates in patients with non-GISTs was 11.6%, 16.3%, 6.98%, respectively. Expression of DOG1 and PDGFRA demonstrated no significant variation with gender, age, position, tumor size, mitotic phase, histology, and risk rank. However, CD117 was related with position and histology (P=0.008 and P=0.045), those in the mesentery having a higher positive rate than those derived from stomach, small intestine, colon and rectum (50.0% vs 94.7%, P=0.008). Furthermore CD117 was also highly expressed in spindle and epithele types.

CONCLUSIONS

DOG1 had a good sensitivity and specificity as a kind of newly discovered marker, especially for KIT negative GISTs. However, DOG1, CD117 and PDGFRA cannot be used for assessing the rish of patients.

Significance of TMEM16A expression in colorectal carcinoma

AIM: To investigate the expression of transmembrane protein 16A (TMEM16A) in colorectal carcinoma.

METHODS: The expression of TMEM16A was detected by immunohistochemistry in 67 surgical colorectal carcinoma specimens and matched tumor-adjacent colorectal specimens.

RESULTS: TMEM16A was expressed in both cytoplasm and cell membrane. Among 67 colorectal carcinoma specimens, TMEM16A expression was negative in 4 cases (5.97%), weakly positive in 11 cases (16.42%), positive in 20 cases (29.85%), and strongly positive in 32 cases (47.76%). Among 67 tumor-adjacent healthy tissue specimens, TMEM16A expression was negative in 27 cases (40.30%), weakly positive in 35 cases (52.24%), positive in 3 cases (4.48%), and strongly positive in 2 cases (2.99%). The positive ("positive" plus "strongly positive") rate of TMEM16A expression was significantly higher in colorectal carcinoma tissue than in tumor adjacent healthy tissue (77.61% vs 7.46%, P < 0.005).

CONCLUSION: Aberrant expression of TMEM16A is a frequent feature in colorectal carcinoma. TMEM16A can be used as a new candidate target for diagnosis and treatment of colorectal carcinoma.

Molecular Pathology of Gastrointestinal Cancer

The purpose of this review is to discuss important molecular changes that aid decision making in patient management and play a role in emerging treatment strategies for gastrointestinal malignancies. Although screening and surveillance practices have had an impact on the natural history of some tumor types, gastric carcinoma is a major cause of morbidity and mortality in high prevalence regions and colorectal carcinoma is still the fourth leading cause of cancer related death in the United States.

DOG1 (clone K9) is seldom expressed and not useful in the evaluation of pancreatic neoplasms

DOG1, a transmembrane calcium-regulated chloride channel protein, is a sensitive and specific marker for gastrointestinal stromal tumors compared with other spindle cell and epithelioid neoplasms. Overexpression has also been described in a variety of both benign and malignant epithelial neoplasms. Recently, DOG1 immunoreactivity has been reported in pancreatic solid pseudopapillary tumors (SPT), suggesting a role as a marker for SPT. Utilizing immunohistochemistry, we evaluated DOG1 expression in pancreatic neoplasms to determine the prevalence of staining and establish diagnostic utility. Multiple tissue microarrays (TMA) were created from cores of formalin-fixed paraffin-embedded blocks containing pancreatic adenocarcinomas (n=112), neuroendocrine tumors (n=99), serous cystadenomas (n=28), and SPT (n=14) as well as normal pancreas (n=12). Immunoreactivity for DOG1 (clone K9) was assessed for intensity (1 to 3+), percentage of tumor positivity and location. Of the 99 cases of neuroendocrine tumors, only 2 (2%) were focally positive. Patchy staining was identified in 8 cases (7%) of adenocarcinoma of 1 to 2+ intensity, involving 15% to 80% of the tumor cells and primarily seen in a membranous and luminal distribution. In contrast to a previous report, no DOG1 positivity was observed in SPT, evaluated by both TMA and full sections. The TMAs of serous cystadenomas and normal pancreas were negative for DOG1. Rarely, pancreatic islets displayed granular, cytoplasmic staining. DOG1 antibody clone K9 is not a useful marker for SPT or other primary pancreatic neoplasms. Additional studies may be helpful to evaluate differences between clones of DOG1.

DOG1 immunoreactivity in uterine leiomyosarcomas

AIMS

DOG1 is a recently described marker of gastrointestinal stromal tumour (GIST) which is considered to be extremely sensitive and, among mesenchymal neoplasms, quite specific for this tumour type. Following the identification of DOG1 immunoreactivity in a uterine leiomyosarcoma, we wished to ascertain how prevalent DOG1 immunoreactivity was in this tumour type.

METHODS

We stained a series of uterine leiomyosarcomas (n=26) with DOG1 and with CD117 (c-kit), another marker of GIST. Staining with both markers was classified as negative, focal (<50% tumour cells positive) or diffuse (≥50% tumour cells positive).

RESULTS

DOG1 immunoreactivity was present in seven of 26 (27%) leiomyosarcomas. Staining was focal in five cases and diffuse in two. CD117 was positive in three of 26 (11.5%) cases, two focal and one diffuse. Two cases were positive with DOG1 and CD117. One of five uterine leiomyomas was focally positive with DOG1, and one extrauterine pelvic leiomyoma was diffusely positive with this marker.

CONCLUSIONS

Since GISTs have rarely been described as primary uterine neoplasms, the presence of DOG1 immunoreactivity in a uterine leiomyosarcoma may result in diagnostic confusion, and a panel of markers is necessary for diagnosis. Uterine leiomyosarcomas should be added to the list of mesenchymal neoplasms which may be DOG1 positive.

Inhibition of cell proliferation by a selective inhibitor of the Ca(2+)-activated Cl(-) channel, Ano1

BACKGROUND

Ion channels play important roles in regulation of cellular proliferation. Ano1 (TMEM16A) is a Ca(2+)-activated Cl(-) channel expressed in several tumors and cell types. In the muscle layers of the gastrointestinal tract Ano1 is selectively expressed in interstitial cells of Cajal (ICC) and appears to be required for normal gastrointestinal slow wave electrical activity. However, Ano1 is expressed in all classes of ICC, including those that do not generate slow waves suggesting that Ano1 may have other functions. Indeed, a role for Ano1 in regulating proliferation of tumors and ICC has been recently suggested. Recently, a high-throughput screen identified a small molecule, T16A(inh)-A01 as a specific inhibitor of Ano1.

AIM

To investigate the effect of the T16A(inh)-A01 inhibitor on proliferation in ICC and in the Ano1-expressing human pancreatic cancer cell line CFPAC-1.

METHODS

Inhibition of Ano1 was demonstrated by whole cell voltage clamp recordings of currents in cells transfected with full-length human Ano1. The effect of T16A(inh)-A01 on ICC proliferation was examined in situ in organotypic cultures of intact mouse small intestinal smooth muscle strips and in primary cell cultures prepared from these tissues. ICC were identified by Kit immunoreactivity. Proliferating ICC and CFPAC-1 cells were identified by immunoreactivity for the nuclear antigen Ki67 or EdU incorporation, respectively.

RESULTS

T16A(inh)-A01 inhibited Ca(2+)-activated Cl(-) currents by 60% at 10μM in a voltage-independent fashion. Proliferation of ICC was significantly reduced in primary cultures from BALB/c mice following treatment with T16A(inh)-A01. Proliferation of the CFPAC-1 human cell-line was also reduced by T16A(inh)-A01. In organotypic cultures of smooth muscle strips from mouse jejunum, the proliferation of ICC was reduced but the total number of proliferating cells/confocal stack was not affected, suggesting that the inhibitory effect was specific for ICC.

CONCLUSIONS

The selective Ano1 inhibitor T16A(inh)-A01 inhibited Ca(2+)-activated Cl(-) currents, reduced the number of proliferating ICC in culture and inhibited proliferation in the pancreatic cancer cell line CFPAC-1. These data support the notion that chloride channels in general and Ano1 in particular are involved in the regulation of proliferation.

Gastrointestinal stromal tumor

Gastrointestinal stromal tumor has received a lot of attention over the last 10 years due to its unique biologic behavior, clinicopathological features, molecular mechanisms, and treatment implications. GIST is the most common mesenchymal neoplasm in the gastrointestinal tract and has emerged from a poorly understood and treatment resistant neoplasm to a well-defined tumor entity since the discovery of particular molecular abnormalities, KIT and PDGFRA gene mutations. The understanding of GIST biology at the molecular level promised the development of novel treatment modalities. Diagnosis of GIST depends on the integrity of histology, immunohistochemistry and molecular analysis. The risk assessment of the tumor behavior relies heavily on pathological evaluation and significantly impacts clinical management. In this review, historic review, epidemiology, pathogenesis and genetics, diagnosis, role of molecular analysis, prognostic factor and treatment strategies have been discussed.

Enhanced expression of ANO1 in head and neck squamous cell carcinoma causes cell migration and correlates with poor prognosis

Head and neck squamous cell carcinoma (HNSCC) has the potential for early metastasis and is associated with poor survival. Ano1 (Dog1) is an established and sensitive marker for the diagnosis of gastrointestinal stromal tumors (GIST) and has recently been identified as a Ca²⁺ activated Cl⁻ channel. Although the ANO1 gene is located on the 11q13 locus, a region which is known to be amplified in different types of human carcinomas, a detailed analysis of Ano1 amplification and expression in HNSCC has not been performed. It is thus still unclear how Ano1 contributes to malignancy in HNSCC. We analyzed genomic amplification of the 11q13 locus and Ano1 together with Ano1-protein expression in a large collection of HNSCC samples. We detected a highly significant correlation between amplification and expression of Ano1 and showed that HNSCC patients with Ano1 protein expression have a poor overall survival. We further analyzed the expression of the Ano1 protein in more than 4′000 human samples from 80 different tumor types and 76 normal tissue types and detected that besides HNSCC and GISTs, Ano1 was rarely expressed in other tumor samples or healthy human tissues. In HNSCC cell lines, expression of Ano1 caused Ca²⁺ activated Cl⁻ currents, which induced cell motility and cell migration in wound healing and in real time migration assays, respectively. In contrast, knockdown of Ano1 did not affect intracellular Ca²⁺ signaling and surprisingly did not reduce cell proliferation in BHY cells. Further, expression and activity of Ano1 strongly correlated with the ability of HNSCC cells to regulate their volume. Thus, poor survival in HNSCC patients is correlated with the presence of Ano1. Our results further suggest that Ano1 facilitates regulation of the cell volume and causes cell migration, which both can contribute to metastatic progression in HNSCC.

Clinical features and treatment of gastrointestinal stromal tumors: Recent advances

Gastrointestinal stromal tumors (GISTs) are the most common gastrointestinal mesenchymal tumors. The development of molecular biology, pathology and clinical medicine in recent years has deepened our understanding of GISTs. The combination of traditional surgery and molecular targeted drugs is particularly important for the treatment of GISTs. Multi-target and multi-kinase inhibitors such as imatinib and sunitinib have been used for the treatment of unresectable and recurrent GISTs. This paper provides a brief review of gene analysis, pathological characteristics, operational and adjuvant therapy of GISTs.

Interstitial cells in the primate gastrointestinal tract

Kit immunohistochemistry and confocal reconstructions have provided detailed 3-dimensional images of ICC networks throughout the gastrointestinal (GI) tract. Morphological criteria have been used to establish that different classes of ICC exist within the GI tract and physiological studies have shown that these classes have distinct physiological roles in GI motility. Structural studies have focused predominately on rodent models and less information is available on whether similar classes of ICC exist within the GI tracts of humans or non-human primates. Using Kit immunohistochemistry and confocal imaging, we examined the 3-dimensional structure of ICC throughout the GI tract of cynomolgus monkeys. Whole or flat mounts and cryostat sections were used to examine ICC networks in the lower esophageal sphincter (LES), stomach, small intestine and colon. Anti-histamine antibodies were used to distinguish ICC from mast cells in the lamina propria. Kit labeling identified complex networks of ICC populations throughout the non-human primate GI tract that have structural characteristics similar to that described for ICC populations in rodent models. ICC-MY formed anastomosing networks in the myenteric plexus region. ICC-IM were interposed between smooth muscle cells in the stomach and colon and were concentrated within the deep muscular plexus (ICC-DMP) of the intestine. ICC-SEP were found in septal regions of the antrum that separated circular muscle bundles. Spindle-shaped histamine(+) mast cells were found in the lamina propria throughout the GI tract. Since similar sub-populations of ICC exist within the GI tract of primates and rodents and the use of rodents to study the functional roles of different classes of ICC is warranted.

Pathology of gastrointestinal stromal tumors

Gastrointestinal stromal tumor (GIST) is a well recognized and relatively well understood soft tissue tumor. Early events in GIST development are activating mutations in KIT or PDGFRA, which occur in most GISTs and encode for mutated tyrosine receptor kinases that are therapeutic targets for tyrosine kinase inhibitors, including imatinib and sunitinib. A small minority of GISTs possessing neither KIT nor PDGFRA mutations may have germline mutations in SDH, suggesting a potential role of SDH in the pathogenesis. Immunohistochemical detection of KIT, and more recently DOG1, has proven to be reliable and useful in the diagnosis of GISTs. Because current and future therapies depend on pathologists, it is important that they recognize KIT-negative GISTs, GISTs in specific clinical contexts, GISTs with unusual morphology, and GISTs after treatment. This review focuses on recent developments in the understanding of the biology, immunohistochemical diagnosis, the role of molecular analysis, and risk assessment of GISTs.

TMEM16A induces MAPK and contributes directly to tumorigenesis and cancer progression

Frequent gene amplification of the receptor-activated calcium-dependent chloride channel TMEM16A (TAOS2 or ANO1) has been reported in several malignancies. However, its involvement in human tumorigenesis has not been previously studied. Here, we show a functional role for TMEM16A in tumor growth. We found TMEM16A overexpression in 80% of head and neck squamous cell carcinoma (SCCHN), which correlated with decreased overall survival in patients with SCCHN. TMEM16A overexpression significantly promoted anchorage-independent growth in vitro, and loss of TMEM16A resulted in inhibition of tumor growth both in vitro and in vivo. Mechanistically, TMEM16A-induced cancer cell proliferation and tumor growth were accompanied by an increase in extracellular signal-regulated kinase (ERK)1/2 activation and cyclin D1 induction. Pharmacologic inhibition of MEK/ERK and genetic inactivation of ERK1/2 (using siRNA and dominant-negative constructs) abrogated the growth effect of TMEM16A, indicating a role for mitogen-activated protein kinase (MAPK) activation in TMEM16A-mediated proliferation. In addition, a developmental small-molecule inhibitor of TMEM16A, T16A-inh01 (A01), abrogated tumor cell proliferation in vitro. Together, our findings provide a mechanistic analysis of the tumorigenic properties of TMEM16A, which represents a potentially novel therapeutic target. The development of small-molecule inhibitors against TMEM16A may be clinically relevant for treatment of human cancers, including SCCHN.

Updates on the management of gastrointestinal stromal tumors

Despite being the most common sarcoma of the gastrointestinal tract, gastrointestinal stromal tumor (GIST) has been widely recognized as a unique entity for just over a decade. The advent of tyrosine kinase inhibitors has revolutionized the diagnosis and treatment of GIST. Although surgery remains the only chance for cure, multimodal treatment that includes molecular therapy continues to develop. Optimal management of GIST requires careful radiographic, pathologic, medical, and surgical care, emphasizing the need for a multidisciplinary approach. This review highlights recent developments in the management of GIST.

Gastrointestinal stromal tumors: a review of case reports, diagnosis, treatment, and future directions

Gastrointestinal stromal tumor (GIST) is a nonepithelial, mesenchymal tumor first described by Mazur and Clark in 1983. Since then, its molecular biology has been studied in great detail. Special interest in the role of tyrosine kinase in its regulation has been the target by different drug research. Mutation in c-kit exons 9, 11, 13, 17 and PDGFRA mutation in exons 12, 14, 18 are responsible for activation of gene signaling system resulting in uncontrolled phosphorylation and tissue growth. However, 5 to 15% of GISTs does not harbor these mutations, which raises additional questions in another alternate signaling pathway mutation yet to be discovered. Diagnosis of GISTs relies heavily on KIT/CD117 immunohistochemical staining, which can detect most GISTs except for a few 3% to 5% that harbors PDGFRA mutation. Newer staining against PKC theta and DOG-1 genes showed promising results but are not readily available. Clinical manifestation of GISTs is broad and highly dependent on tumor size. Surgery still remains the first-line treatment for GISTs. The advancement of molecular biology has revolutionized the availability of newer drugs, Imatinib and Sunitinib. Together with its advancement is the occurrence of Imatinib/Sunitinib drug resistance. With this, newer monoclonal antibody drugs are being developed and are undergoing clinical trials to hopefully improve survival in patients with GISTs.

Involvement of Na(+)-leak channel in substance P-induced depolarization of pacemaking activity in interstitial cells of Cajal

Interstitial cells of Cajal (ICCs) are the pacemaking cells in the gastrointestinal muscles that generate the rhythmic oscillations in membrane potential known as slow waves. ICCs also mediate or transduce inputs from the enteric nervous system. Substance P (SubP) is a member of the family of mammalian tachykinin peptides that are predominantly released by enteric neurons. This study assessed the relationship of Na(+)-leak channel (NALCN) in the SubP-induced depolarization in pacemaking activity in the gastrointestinal tract. The patch-clamp technique for whole-cell recording was used in cultured cluster and single ICCs. Electrophysiological and pharmacological properties of SubP in ICC pacemaking activity were similar to those of NALCN. Reverse-transcription polymerase chain reaction, Western blotting, and immunohistochemistry all showed abundant and localized expression of NALCN messenger RNA and protein in mouse small intestine. NALCN is involved in the SubP-induced depolarization of intestinal pacemaking activity. The protein is a potential target for pharmacological treatment of motor disorders of the gut.

Gastrointestinal stromal tumours can express CD10 and epithelial membrane antigen but not oestrogen receptor or HMB45

AIMS

Gastrointestinal stromal tumour (GIST) may share morphological and/or immunohistochemical features with various intra-abdominal neoplasms, including endometrial stromal sarcoma, perivascular epithelioid cell tumour (PEComa), melanoma and synovial sarcoma. Each of these various neoplasms has characteristic immunohistochemical markers, including epithelial membrane antigen (EMA), CD10, oestrogen receptor alpha (ERa) and/or HMB45, and therefore the primary aim of this study was to determine whether these markers are also expressed by GISTs.

METHODS AND RESULTS

Standard size sections of 52 GISTs were immunostained for EMA, CD10, ERa and a melanoma marker cocktail (targeting HMB45 and melan-A). Ten GISTs (19%) showed CD10 immunopositivity. This positivity was confined almost completely to small intestinal GISTs, and was seen among spindle cell GISTs but not epithelioid or mixed cell-type GISTs. Five of the 52 GISTs (9.6%) showed EMA immunopositivity. This positivity was always focal and usually seen in a perivascular location. None of the GISTs showed immunopositivity for ERa or the melanoma marker cocktail.

CONCLUSIONS

GISTs occasionally show CD10 immunopositivity (especially small intestinal spindle cell GISTs), and infrequently show focal EMA positivity. GISTs do not show immunopositivity for ERa or HMB45.