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Three families with multiple gastrointestinal stromal tumors (GISTs) caused by a germline Asp820Tyr mutation at exon 17 of the c-kit gene (KIT-Asp820Tyr) have been reported. We previously generated a knock-in mouse model of the family, and the mice with KIT-Asp818Tyr corresponding to human KIT-Asp820Tyr showed a cecal tumor equivalent to human GIST. In the model mice, we reported that tyrosine kinase inhibitor, imatinib, could stabilize but not decrease the cecal tumor volume. In this report, we examined whether a heat shock protein 90 inhibitor, pimitespib (TAS-116), has an inhibitory effect on phosphorylation of KIT-Asp818Tyr and can decrease the cecal tumor volume in the model mice. First, we showed that pimitespib inhibited KIT phosphorylation both dose- and time-dependently in KIT-Asp818Tyr transfected murine Ba/F3 cells. Then, four 1-week courses of pimitespib were orally administered to heterozygous (KIT-Asp818Tyr/+) model mice. Each course consisted of once-daily administration for consecutive 5 days followed by 2 days-off. Cecal tumors were dissected, and tumor volume was histologically analyzed, Ki-67 labeling index was immunohistochemically examined, and apoptotic figures were counted. Compared to the vehicle treated mice, pimitespib administered mice showed statistically significantly smaller cecal tumor volume, lower Ki-67 labeling index, and higher number of apoptotic figures in 10 high power fields (P = 0.0344, P = 0.0019 and P = 0.0269, respectively). Western blotting revealed that activation of KIT signaling molecules was strongly inhibited in the tumor tissues of pimitespib-administered mice compared to control mice. Thus, pimitespib seemed to inhibit in vivo tumor progression effectively in the model mice. These results suggest that the progression of multiple GISTs in patients with germline KIT-Asp820Tyr might be controllable by pimitespib., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract; most of them have gain-of-function mutations of the KIT gene. There have been rare cases of families with multiple GISTs, that had autosomal dominant germline KIT mutations. Here, we present a case of multiple GISTs caused by a novel germline KIT mutation. Intraoperatively, the main tumor was present in the body of the stomach, and multiple small nodules were detected mainly in the upper and middle part of the gastric wall; several nodules were also present in the small bowel wall. The main tumor and surrounding nodules were resected. DNA sequencing of the tumor tissue, adjacent normal mucosal tissue, and peripheral blood leukocytes revealed that the patient had germline Asp820Gly mutation in exon 17 of the KIT gene. This is the first case with germline Asp820Gly mutation in exon 17 of the KIT gene.

Background: Despite the effectiveness of imatinib mesylate (IM), most gastrointestinal stromal tumours (GISTs) develop IM resistance, mainly due to the additional kinase-domain mutations accompanied by concomitant reactivation of KIT tyrosine kinase. Heat-shock protein 90 (HSP90) is one of the chaperone molecules required for appropriate folding of proteins such as KIT., Methods: We used a novel HSP90 inhibitor, TAS-116, which showed specific binding to HSP90α/β with low toxicity in animal models. The efficacy and mechanism of TAS-116 against IM-resistant GIST were evaluated by using IM-naïve and IM-resistant GIST cell lines. We also evaluated the effects of TAS-116 on the other HSP90 client protein, EGFR, by using lung cell lines., Results: TAS-116 inhibited growth and induced apoptosis in both IM-naïve and IM-resistant GIST cell lines with KIT activation. We found KIT was activated mainly in intracellular compartments, such as trans-Golgi cisternae, and TAS-116 reduced autophosphorylated KIT in the Golgi apparatus. In IM-resistant GISTs in xenograft mouse models, TAS-116 caused tumour growth inhibition. We found that TAS-116 decreased phosphorylated EGFR levels and inhibited the growth of EGFR-mutated lung cancer cell lines., Conclusion: TAS-116 may be a novel promising drug to overcome tyrosine kinase inhibitor-resistance in both GIST and EGFR-mutated lung cancer.

Background: Familial gastrointestinal stromal tumor (GIST) is a rare disease with germline mutations in the c-kit gene (KIT) or platelet-derived growth factor receptor alpha gene (PDGFRA). We had encountered multiple GISTs in the stomach and small intestine during a screening of ovarian cancer for a woman with hereditary breast and ovarian cancer syndrome (HBOC) with breast cancer susceptibility gene II (BRCA2) mutations. The aim of this study was to examine this case in detail., Case Report: A 65-year-old woman diagnosed with HBOC harboring BRCA2 mutations was found to have multiple tumors in the stomach and small intestine by abdominal screening. All tumors were resected, and KIT gene mutations (p.Trp557Leu and p.Lys558Glu) in exon 11 were detected in all tumors and peripheral blood leukocytes. The patient was diagnosed with familial GIST., Conclusion: This was an extremely rare case in which familial GIST with germline KIT gene mutations co-existed with HBOC., (Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Objective: Imatinib is a standard treatment for metastatic gastrointestinal stromal tumor (GIST). Imatinib resistance is mostly caused by secondary mutations in C-KIT. The antitumor effect of second-line agents is correlated with the type of secondary mutation: indeed, sunitinib is effective against tumors with C-KIT exon 13 or 14 mutations. We investigated whether secondary C-KIT mutations can be detected in circulating tumor DNA (ctDNA) from peripheral blood., Methods: This study included 4 patients who underwent resection of imatinib-resistant GIST. Tumor-specific mutations in each tumor were determined by Sanger sequencing. ctDNA was extracted from peripheral blood obtained before and after the treatment of imatinib-resistant lesions. Each of the secondary target mutations in ctDNA was investigated, using a next-generation sequencer., Results: Imatinib-resistant lesions had single-nucleotide substitutions in C-KIT exon 13 in 3 patients and exon 18 in 1 patient. Identical secondary C-KIT mutations could be detected in ctDNA with a mutant fraction range of 0.010-9.385%. One patient had growth of an imatinib-resistant tumor containing a C-KIT exon 13 mutation, and the fraction of ctDNA decreased after initiation of sunitinib., Conclusion: Detection of secondary C-KIT mutations in ctDNA could be useful for the selection of targeted agents and prediction of antitumor effects., (© 2016 S. Karger AG, Basel.)

Background: Duodenal gastrointestinal stromal tumors (GISTs) are a rare subset of GISTs (3-5%), and their clinicopathological features have not been fully described. The purpose of this retrospective study was to examine these characteristics and compare the operative procedures., Methods: Twenty-five patients with duodenal GIST underwent complete resection, local resection (LR) or pancreaticoduodenectomy (PD) from 1990 to 2014 at our 2 hospitals. We analyzed patient characteristics, treatments, histological examinations, postoperative complications and survival outcomes., Results: Twelve patients (48%) with no symptoms were incidentally diagnosed for unrelated reasons. Sixteen patients (64%) had c-kit mutations while 6 (24%) were wild-type, including 4 with a history of neurofibromatosis type 1. Comparing LR (n = 16) and PD (n = 9), the recurrence-free survival rate was significantly worse for PD. On multivariate analysis, however, tumor size was an independent and significant prognostic factor, but not operative procedure. There was no body weight change with LR, but body weight decreased by 7% with PD., Conclusion: Duodenal GISTs had different characteristic genetic mutations compared to other GISTs. LR for duodenal GISTs appears to be oncologically and nutritionally feasible., (© 2016 S. Karger AG, Basel.)

Sporadic mast cell neoplasms and gastrointestinal stromal tumors (GISTs) often have various types of somatic gain-of-function mutations of the c-kit gene which encodes a receptor tyrosine kinase, KIT. Several types of germline gain-of-function mutations of the c-kit gene have been detected in families with multiple GISTs. All three types of model mice for the familial GISTs with germline c-kit gene mutations at exon 11, 13 or 17 show development of GIST, while they are different from each other in skin mast cell number. Skin mast cell number in the model mice with exon 17 mutation was unchanged compared to the corresponding wild-type mice. In the present study, we characterized various types of mast cells derived from the model mice with exon 17 mutation (KIT-Asp818Tyr) corresponding to human familial GIST case with human KIT-Asp820Tyr to clarify the role of the c-kit gene mutation in mast cells. Bone marrow-derived cultured mast cells (BMMCs) derived from wild-type mice, heterozygotes and homozygotes were used for the experiments. Immortalized BMMCs, designated as IMC-G4 cells, derived from BMMCs of a homozygote during long-term culture were also used. Ultrastructure, histamine contents, proliferation profiles and phosphorylation of various signaling molecules in those cells were examined. In IMC-G4 cells, presence of additional mutation(s) of the c-kit gene and effect of KIT inhibitors on both KIT autophosphorylation and cell proliferation were also analyzed. We demonstrated that KIT-Asp818Tyr did not affect ultrastructure and proliferation profiles but did histamine contents in BMMCs. IMC-G4 cells had an additional novel c-kit gene mutation of KIT-Tyr421Cys which is considered to induce neoplastic transformation of mouse mast cells and the mutation appeared to be resistant to a KIT inhibitor of imatinib but sensitive to another KIT inhibitor of nilotinib. IMC-G4 cells might be a useful mast cell line to investigate mast cell biology.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Since our first report in 1998, approximately 30 families with multiple GISTs due to a germline gain-of-function mutation of c-kit have been reported. We herein present a case of a family with multiple GISTs that have a germline c-kit mutation in exon 11 (Del-Val560) in two siblings. One of the patients showed a fair response to treatment with a half-dose of imatinib (200 mg/day). There are few reports describing the response to imatinib in familial GISTs and this drug appears to be a promising therapeutic option.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the human gut. Most sporadic GISTs have somatic gain-of-function mutations of the c-kit gene. The mutations are frequently found at exon 11, sometimes at exon 9 and rarely at exon 13 or 17. Recently, exon 8 c-kit gene mutations were reported in very minor proportion of sporadic GISTs. We also found 3 GISTs with exon 8 c-kit gene mutations in approximately 1,000 sporadic GISTs examined. In the present report, we showed the clinicopathological data of those GISTs. One case had a deletion of codon 419 of aspartate, and 2 cases had a substitution of 3 amino acids of codon 417 to codon 419 to tyrosine. The former was the same mutation recently reported in 2 GIST cases, but the latter has not been reported in any GISTs. All three cases occurred at extragastric sites and two of three showed distant metastasis. Since the remaining case was regarded as high risk for recurrence, imatinib adjuvant treatment has been done without evidence of metastasis. Our results confirmed the idea that exon 8 mutations are minor but actually existing abnormalities in sporadic GISTs, and suggested that such GISTs have a feature of extragastric development and a metastasis-prone nature. Since the exon 8 mutations appeared to be really sensitive to imatinib as shown in the present case study, accurate genotyping including exon 8 of the c-kit gene is necessary in GISTs to predict response to imatinib in both the unresectable/metastatic and adjuvant settings.

Inflammatory myofibroblastic tumors (IMTs) and gastrointestinal stromal tumors (GISTs) are both spindle cell tumors, and occur rarely in the wall of the urinary bladder. In general, immunostaining allows differentiation of IMTs and GISTs. Most IMTs are positive for anaplastic lymphoma kinase (ALK) and negative for KIT, whereas most GISTs are ALK-negative and KIT-positive. Here, we describe a case of a spindle cell tumor in the wall of the urinary bladder. The spindle cells were positive for both ALK and KIT, and it was thus difficult to determine whether the tumor was an IMT or a GIST. We eventually diagnosed an IMT, because ALK gene rearrangement was confirmed by fluorescent in-situ hybridization. Cytoplasmic staining for KIT and the absence of other GIST markers, including DOG1 and platelet-derived growth factor α, indicated that the tumor was not a GIST. Therefore, IMTs should be included in the differential diagnosis of spindle cell tumors, even those that are KIT-positive.

Multiple gastrointestinal stromal tumors (GISTs) caused by germline c-kit gene mutations are an extremely rare autosomal dominant disorder. A 57-year-old Japanese woman was referred to a hospital for appetite loss and severe weight loss. She had 2 large abdominal masses around the stomach, which were surgically resected. Histological examination revealed that these tumors were GISTs. Multiple microscopic GISTs and diffuse hyperplasia of the interstitial cells of Cajal were also seen in the background gastric and small intestinal walls. Characteristically, the GISTs showed severe hyalinization with calcification and partial heterotopic ossification, which may have caused the patient's severe dysphagia. Mutational analysis of the c-kit gene revealed a substitution at codon 642 in exon 13 (K642T) in the tumor, normal ileal mucosa and peripheral blood leukocytes, indicating that the mutation is in the germline. This is the first case of multiple GISTs with novel germline c-kit gene mutation at exon 13., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract, and typically present as discrete well-circumscribed but non-encapsulated tumor masses. In this report, we describe a case of colonic perforation caused by an unusual form of GIST. A 72-year-old Japanese woman presented to the emergency department with acute abdominal pain. Under the provisional diagnosis of sigmoid colon perforation, a laparoscopic sigmoidectomy was performed. Although the tumor mass was undetectable during the preoperative examination, a spindle cell lesion with a diffuse longitudinal growth pattern replacing the muscularis propria was revealed by microscopic examination. The spindle cell lesion was exposed at the perforation, suggesting a causal relationship between the lesion and the perforation. The spindle cell lesion was KIT-positive and had a mutation in the C-KIT gene at exon 11. We diagnosed it as diffuse infiltrating GIST. We consider that the lesion would be a cause of the colonic perforation, and emphasize the importance of accurate diagnosis of the lesion by histological, immunohistochemical and genetic examinations., (© 2014 The Authors. Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd.)

The great majority of gastrointestinal stromal tumors (GISTs) have gain-of-function mutations of the c-kit gene, which encodes KIT receptor tyrosine kinase. Most of the mutations are located at exon 11, but some are at exon 9 or at other exons. Mutation types at exon 11 vary, while most mutations at exon 9 are a particular duplication of Ala502Tyr503 (KIT-Dup-Ala502Tyr503). Recently a duplication of Ser501Ala502 (KIT-Dup-Ser501Ala502) at exon 9 has been reported in two cases of pediatric mastocytosis and one case of adult mast cell leukemia. Although KIT-Dup-Ser501Ala502 had not been reported in GISTs, we found two GIST cases possessing the mutation in 45 GIST cases with exon 9 c-kit gene mutations, among a total of approximately 500 GIST cases examined. In this report, we briefly summarize clinicopathological findings of the two cases, and characterize the biology of the mutation. When autophosphorylation of KIT-Dup-Ser501Ala502 was examined by transient transfection of c-kit cDNA with Dup-Ser501Ala502 into CHO-K1 cells, KIT-Dup-Ser501Ala502 was ligand-independently activating. The inhibitory effect of selective tyrosine kinase inhibitors, imatinib and nilotinib, on KIT-Dup-Ser501Ala502 was examined and compared with that of KIT-Dup-Ala502Tyr503. Imatinib efficiently inhibited constitutive activation of KIT-Dup-Ser501Ala502 at a concentration of 0.1 μM, whereas it inhibited that of KIT-Dup-Ala502Tyr503 at a concentration of 10 μM. Constitutive activation of KIT-Dup-Ser502Ala503 was not inhibited by nilotinib even at a concentration of 10 μM but that of KIT-Dup-Ala501Tyr502 was almost completely inhibited at a concentration of 1 μM. The results suggest that imatinib and nilotinib could be more effective on GISTs with KIT-Dup-Ser501Ala502 than those with KIT-Dup-Ala502Tyr503. In fact, a patient with KIT-Dup-Ser501Ala502 showed long-term stable disease with administration of the usual dose of 400 mg imatinib. Although mutation sites of KIT-Dup-Ser501Ala502 and KIT-Dup-Ala502Tyr503 are closely located, imatinib- and nilotinib-sensitive KIT-Dup-Ser501Ala502 are distinguishable from KIT-Dup-Ala502Tyr503.

We found a novel type germline mutation at exon 11 of the c-kit gene, which results in a substitution of Tyr to Cys at codon 553 of the c-kit gene product (KIT-Tyr553Cys), in a 68-year-old female patient with multiple gastrointestinal stromal tumors (GISTs). In the present study, we carried out mutational analysis in her family members to determine the carriers and characterized the mutation by introducing the corresponding mutation (murine KIT-Tyr552Cys) into expression vector possessing murine c-kit cDNA. Mutational analysis of peripheral blood leukocytes of her family members revealed that a 44-year-old son had the same mutation, but at present he had neither apparent symptoms nor images of multiple GISTs. By transfection with the expression vector possessing the murine mutant c-kit cDNA, interleukin-3-dependent Ba/F3 murine lymphoid cells started growing autonomously without any growth factors, indicating that the mutation was considered to be of gain-of-function. Imatinib, a small molecule of tyrosine kinase inhibitor, effectively inhibited autophosphorylation of KIT-Tyr552Cys. Nilotinib, another small molecule of the KIT inhibitor, also effectively inhibited autophosphorylation of KIT-Tyr552Cys. In fact, proliferation of Ba/F3 cells expressing KIT-Tyr552Cys was effectively inhibited by both imatinib and nilotinib. These findings indicate that the novel type human KIT-Tyr553Cys mutation is the cause of the present familial and multiple GISTs, and that both imatinib and nilotinib might effectively inhibit the growth of GISTs developing in the patients of this family.

Familial gastrointestinal stromal tumor (GIST) is an extremely rare autosomal dominant disorder, and approximately 20 families have been reported to date. In this article, we present one additional family. A 25-year-old Japanese woman presented with abdominal pain, and subsequent image analyses disclosed multiple tumors measuring 12 cm in maximum diameter in the lower digestive tract. The postoperative histologic examination showed multiple GISTs and diffuse hyperplasia of interstitial cells of Cajal. Her mother had a history of GIST in the digestive tract. Three members of this family including her younger sister and mother had cutaneous hyperpigmentation of external genitalia and axilla. Their DNA samples showed identical missense mutation at exon 11 in the juxtamembrane domain of the KIT gene, and this mutation site was considered to be a hot spot in familial GIST. One year after, her younger sister suffered from multiple GISTs in the digestive tract at the age of 25 years. To correctly diagnose familial GIST, mutual information should be exchanged among clinicians, pathologists, and molecular scientists., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Two families with a germline Asp820Tyr mutation at exon 17 of the c-kit gene and multiple gastrointestinal stromal tumors (GISTs) have been reported. Recently, we generated a knock-in mouse model of the family, and mice with KIT-Asp818Tyr corresponding to human KIT-Asp820Tyr showed a cecal GIST-like tumor. In this report, we examined the in vivo effect of imatinib on tumor progression in knock-in mice. Imatinib of 100 microg/g body weight was administered to heterozygous (KIT-Asp818Tyr/+) mice orally for 7, 14 and 28 days, and cecal tumors were dissected. Both macroscopic size and the measured volume of cecal tumors were not significantly reduced after a 7-, 14- and 28-day administration of imatinib when compared with those before imatinib administration. Cell proliferation was assessed by Ki-67 immunohistochemistry and the labeling index significantly decreased after imatinib administration, but the value of the index after imatinib was only about half compared with that before imatinib. Western blotting and real-time PCR revealed that KIT expression was almost equivalent, but KIT phosphorylation was significantly but not completely inhibited in tumor tissues after 7, 14 and 28 days of imatinib administration when compared with that before imatinib administration. Phosphorylation of Akt and Stat1 was accordingly inhibited after imatinib administration. Thus, imatinib seemed to inhibit in vivo tumor proliferation but not decrease tumor volume on this mouse model, probably because of an insufficient inhibition of phosphorylation of KIT and its downstream signaling molecules. These results suggested that progression of multiple GISTs in patients with germline Asp820Tyr might be partially controlled by imatinib and that model mice provide an opportunity to examine the effect of various other targeted drugs on in vivo tumor progression.

Gastrointestinal stromal tumors (GISTs) are one of the representative diseases for which we now use small-molecule inhibitors against KIT and PDGFRs. Most GISTs have gain-of-function mutations of the c-kit or PDGFRA gene. The mutations result in constitutive receptor activation, and the activated receptor stimulates downstream signaling pathways. Because of resistance to conventional chemotherapy, the prognosis of patients with unresectable or metastatic GISTs has been very poor. The therapy of choice for resectable GIST is still surgery, but at present we can use imatinib, a selective tyrosine kinase inhibitor for KIT, PDGFRs and Bcr-Abl, for such advanced GIST patients. Although molecular target therapy has been very effective, secondary resistance to imatinib often develops during long-term imatinib administration. Secondary mutations of the c-kit gene in addition to primary c-kit gene mutation are a major cause of secondary resistance to imatinib. Now, we can use sunitinib for patients with imatinib-resistant GIST.

Background: Although sunitinib malate has shown significant clinical effect on imatinib-resistant gastrointestinal stromal tumors, with acceptable tolerability and improved prognosis for the patients, the mechanism of resistance to the drug is still under investigation., Methods: We analyzed findings in 8 patients (seven men and one woman, median age, 59 years) out of 17 patients with imatinib-resistant gastrointestinal stromal tumors who had been treated with sunitinib. Sunitinib was orally administered once a day at a starting dose of 37.5 mg/day, 50 mg/day, or 75 mg/day, with 4 weeks on and 2 weeks off., Results: All imatinib- as well as sunitinib-resistant lesions showed viable tumor cells strongly re-expressing the KIT protein. Pre-imatinib samples had heterogeneous KIT mutations either in exon 9 (n = 1) or exon 11 (n = 7), and seven imatinib-resistant tumors carried a secondary mutation either in the ATP-binding domain or in the activation loop in the same allele as the primary mutation. Most patients with imatinib-resistant tumors carrying secondary mutations in the ATP-binding domain obtained clinical benefits from sunitinib, whereas some tumors with mutations in the activation loop showed resistance to the drug. A tumor with mutations in exon 11 and 13 of the KIT gene, and showing partial response to sunitinib, harbored a third mutation in the activation loop when sunitinib resistance was shown. All additional secondary and tertiary mutations were located on the same allele as the primary mutation (cis-mutation)., Conclusion: These findings indicate that an additional cis-mutation in the activation loop of the KIT gene could be a potential cause of sunitinib resistance in gastrointestinal stromal tumors.

Although imatinib showed high activity for advanced gastrointestinal stromal tumor (GIST) and improved the prognosis of GIST patients, resistance to the drug appears with prolonged use. Mechanisms of acquired resistance are still under investigation. In the present study, we carried out histologic and genetic analysis of 45 secondary resistant lesions obtained from 25 Japanese GIST patients treated with imatinib. All resistant lesions showed viable tumor cells expressing KIT protein, whereas imatinib-sensitive lesions did not. All pre-imatinib samples have KIT mutations either in exon 9 (n = 3) or exon 11 (n = 22), identified in the KIT gene of corresponding resistant tumors. In addition to primary mutations, 33 out of 45 tumors (73%) showed secondary KIT mutations in the kinase domain of the KIT gene. Secondary mutations are missense mutations and are mostly located in the kinase domains of the same allele to the primary mutations (cis-position). Resistant lesions showed monoclonal development of tumor cells. Taken together, additional cis-positioned mutations in the kinase domains are a major cause of secondary resistance to imatinib in Japanese GIST patients.

Several families exhibiting multiple gastrointestinal stromal tumours (GISTs) and germline c-kit gene mutations at exons 8, 11, 13, or 17 have been reported. These patients also exhibit diffuse hyperplasia of the interstitial cells of Cajal (ICCs) as a pre-existing lesion of multiple GISTs. We generated a mouse model of a family with germline c-kit gene mutation at exon 17, and compared the phenotypes between the mice and humans. The mouse counterpart (KIT-Asp818Tyr) of the human KIT-Asp820Tyr mutation was transmitted into germline by a knock-in strategy. Mating of male and female heterozygotes (KIT-Asp818Tyr/+) resulted in the generation of homozygotes (KIT-Asp818Tyr/KIT-Asp818Tyr). Histological examination revealed that all heterozygotes had both a small KIT-positive mesenchymal tumour at the caecum, consistent with GIST, and KIT-positive diffuse spindle-shaped cell proliferation in the distal oesophagus, stomach, proximal duodenum, and colon consistent with ICC hyperplasia. All homozygotes exhibited a larger caecal tumour and more prominent spindle-shaped cell proliferation compared with the heterozygous mice, and they usually died within 10 weeks after birth, likely due to ileus. The small intestine of both genotypes showed no apparent morphological abnormality, and autonomous contraction of the ileal segments appeared normal. Western blotting demonstrated that the caecal tumours expressed phosphorylated KIT, MAPK, Stat1, and Stat5. These mutant mice are considered to be useful for further investigation of the mechanism of GIST development as a result of ICC hyperplasia and for assessment of the in vivo effects of drugs against molecular targets., (Copyright (c) 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

Lymph node metastasis from gastrointestinal stromal tumor (GIST) is quite rare. We report two cases of gastric GIST with nodal metastases and results of their mutation analyses. In the first case (78-year-old male), a mass 4.0 cm in size was located at the gastric cardia. Proximal gastrectomy was performed. In the other case (40-year-old female), the gastric tumor was 2.5 cm in size. Computed tomography scan revealed a hepatic metastasis. Imatinib mesylate was administered as primary treatment, at the patient's preference, but the tumors exhibited no response. Wedge resection of the stomach and partial hepatectomy were performed. In both cases, histological examination revealed that the tumors consisted of spindle cells. In the former case, there was an isolated lymph node metastasis at the right cardia. In the latter, three of 5 sampled nodes adjacent to the tumor were positive. In both cases, immunohistochemical analyses showed that primary and metastatic tumors were diffusely positive for CD117 and CD34 and negative for desmin and S100-protein. In the former case, there was a deletion mutation in CD117 exon 11, the most common genotype in GIST. In the latter, there were no detectable mutations in CD117 or platelet-derived growth factor receptor alpha.

Aggressive systemic mastocytosis (ASM) is a very rare form of mast cell neoplasm that does not benefit from conventional chemotherapy. The majority of adult mast cell neoplasms and gastrointestinal stromal tumors (GISTs) have mutations in the proto-oncogene c-kit, which encodes the KIT receptor tyrosine kinase. The c-kit gene mutations are generally confined to the tyrosine kinase II domain in mast cell neoplasms, but are often observed at the juxtamembrane domain in GISTs. We found a case of ASM with a juxtamembrane-type mutation, Val559Ile, and in this report the mutation was characterized through transfection of the mutated c-kit cDNA into human embryonic kidney cells. Phosphorylation of KIT and its possible downstream signaling molecules were examined in the presence or absence of imatinib, a selective tyrosine kinase inhibitor. Ligand-independent autophosphorylation was observed in the mutant KIT with Val559Ile as well as that with Val559Asp, as found in GISTs. Imatinib, at a concentration of 10 microM, inhibited autophosphorylation of the mutant KIT with Val559Asp, but not that with the Val559Ile. Phosphorylation of MAPK and STAT5 was also inhibited by imatinib at the same concentration, in cells expressing Val559Asp but not in those expressing Val559Ile. These results suggest that different mutations, even at the same codon, in juxtamembrane domain of the c-kit gene show different inhibitory effects of imatinib, and that patients with GISTs or mast cell neoplasms possessing this Val559Ile mutation are resistant to imatinib therapy.

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors in the gastrointestinal tract. It was found that most GIST expressed KIT, a receptor tyrosine kinase encoded by protooncogene c-kit. In normal gastrointestinal wall, KIT is expressed by interstitial cells of Cajal (ICC), which are a pacemaker for autonomous gastrointestinal movement. Because both GIST and ICC are double-positive for KIT and CD34, and because familial and multiple GIST appear to develop from diffuse hyperplasia of ICC, GIST are considered to originate from ICC or their precursor cells. It was also found that approximately 90% of the sporadic GIST have somatic gain-of-function mutations of the c-kit gene, and that the patients with familial and multiple GIST have germline gain-of-function mutations of the c-kit gene. These facts strongly suggest that the c-kit gene mutations are a cause of GIST. Approximately half of the sporadic GIST without c-kit gene mutations were demonstrated to have gain-of-function mutations in platelet-derived growth factor receptor-alpha (PDGFRA) gene that encodes another receptor tyrosine kinase. Because KIT is immunohistochemically negative in a minority of GIST, especially in PDGFRA gene mutation-harboring GIST, mutational analyses of c-kit and PDGFRA genes may be required to diagnose such GIST definitely. Imatinib mesylate was developed as a selective tyrosine kinase inhibitor. It inhibits constitutive activation of mutated KIT and PDGFRA, and is now being used for KIT-positive metastatic or unresectable GIST as a molecular target drug. Confirmation of KIT expression by immunohistochemistry is necessary for application of the drug. The effect of imatinib mesylate is different in various types of c-kit and PDGFRA gene mutations, and the secondary resistance against imatinib mesylate is often acquired by the second mutation of the identical genes. Mutational analyses of c-kit and PDGFRA genes are also significant for prediction of effectiveness of drugs including newly developed agents.

Currently, there are no data on the secondary resistance of gastrointestinal stromal tumours to imatinib. Here, we report a case of metastatic gastrointestinal stromal tumour that relapsed during imatinib therapy. Mutation analysis showed that the imatinib-resistant liver tumour contained two c-kit mutations.

Most sporadic gastrointestinal stromal tumours (GISTs) have somatic c-kit gene mutations that are considered to be causal. Neurofibromatosis type 1 (NF1) is caused by mutations of the NF1 gene and NF1 patients have an increased risk of developing GISTs. Since most neoplasms are considered to develop as a result of the combination of several gene mutations, these findings suggest that GISTs from NF1 patients might have somatic c-kit gene mutations and that sporadic GISTs from non-NF1 patients might have somatic NF1 gene mutations. The present study analysed 29 GISTs from seven NF1 patients for c-kit gene mutations and ten sporadic GISTs from ten non-NF1 patients for NF1 mutations. Exons 9, 11, 13, and 17 of the c-kit gene were amplified and directly sequenced after the extraction of genomic DNA from wax-embedded tissues from 26 GISTs from five NF1 patients. The whole coding region of the c-kit cDNA and the whole coding region of the NF1 cDNA were amplified and directly sequenced after RNA extraction and cDNA synthesis in three fresh GIST tissues from two NF1 patients and ten fresh GIST tissues from ten non-NF1 patients. Of the ten sporadic GISTs, eight had heterozygous mutations at exon 11, and one at exon 9, of c-kit. Heterozygous NF1 gene mutations were detected in GISTs from the two NF1 patients from whom fresh tissues were available. None of the 29 GISTs derived from NF1 patients had detectable c-kit gene mutations and none of the ten GISTs derived from non-NF1 patients had detectable NF1 mutations. These results suggest that the pathogenesis of GISTs in NF1 patients is different from that in non-NF1 patients., (Copyright 2004 John Wiley & Sons, Ltd.)

Objectives: Since all gastrointestinal stromal tumours (GISTs) are practically considered to be potentially malignant, they must be clinically differentiated from other submucosal tumours (SMTs). In this study, we carried out endoscopic ultrasonography-guided fine needle aspiration biopsy (EUS-FNAB) against follow-up SMTs to examine whether the method is sufficient for pathological diagnosis and analysis of c-kit mutation. The relationship between tumour growth and c-kit mutation was also examined., Methods: The tumour tissues were obtained by EUS-FNAB from 10 Japanese follow-up cases with SMT. Paraffin sections of tissues were used for haematoxylin and eosin staining, and for immunohistochemistry. Genomic DNA was extracted from the sections, and c-kit gene fragments of exons 9, 11, 13 and 17 were amplified by polymerase chain reaction and directly sequenced., Results: Nine SMTs were diagnosed as GIST and one was diagnosed as schwannoma by immunohistochemistry. Mutation at exon 11 was detected in six of nine GISTs, but no mutations were detected at exons 9, 13 and 17 in all GISTs. The case of schwannoma did not have any mutations at exons 9, 11, 13 and 17. Statistical significance was not observed between the average growth rate of six GISTs with the mutation and that of three GISTs without the mutation (P = 0.694)., Conclusions: EUS-FNAB against SMTs was useful for the differential diagnosis of SMT and the analysis of c-kit mutation. The c-kit mutation might not be one of the predictable markers for rapid tumour growth.

Mutations of proto-oncogene c-KIT in gastrointestinal stromal tumors (GISTs) are considered to cause a constitutive activation of KIT responsible for their oncogenesis. Imatinib has therapeutic potential for GISTs because of its inhibitory effect on KIT kinase activity. To investigate the effect of Imatinib on various c-KIT mutations found in GISTs, we examined kinase activity of KIT, cell proliferation and tumorigenicity of transfectants with various c-KIT mutations. Murine lymphoid Ba/F3 cells transfected with one of the three types of mutants (KIT(del559-560), KIT(642Glu), and KIT(820Tyr)) or wild-type KIT were used for the experiments. Phosphorylation of KIT, mitogen-activated protein (MAP) and Akt was studied by immunoblotting with or without immunoprecipitation. In vitro studies on cell proliferation using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylcetrazolium bromide colorimetric assay and in vivo tumorigenicity assay using nude mice were also carried out. Imatinib could inhibit the KIT, MAP and Akt phosphorylation of all the transfectants but had a weaker effect on KIT(820Tyr). Imatinib potently inhibited the proliferation of cells transfected with KIT(820Tyr) at the concentration of 10 microM whereas it inhibited the other 3 types at 1 microM. Moreover, Imatinib could inhibit the tumor formation in nude mice transplanted with transfectants. In various types of activating mutant KIT, Imatinib could inhibit the constitutive activation of KIT signal transduction and cell proliferation both in vitro and in vivo although the effect of Imatinib on KIT(820Tyr) was weaker than that on KIT(del559-560) or KIT(642Glu)., (Copyright 2003 Wiley-Liss, Inc.)

Background and Aim: Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the human gut. They frequently have gain-of-function mutations of the c-kit gene, which encodes a receptor, tyrosine kinase. The mutations were found at exon 11 in most cases, and either at exon 9 or at exon 13 in rare cases. Recently, we found a family with multiple GIST and a gain-of-function mutation at exon 17. The family was the first reported GIST case with c-kit gene mutation at exon 17 including sporadic GIST. Although we previously reported that the c-kit gene mutation at exon 17 was not detected in 124 sporadic GIST by single-strand conformation polymorphism (SSCP) analysis, the mutation at exon 17 observed in the familial GIST was detectable by the use of direct sequencing but not by our SSCP method. In the present study, we examined the mutations at exon 17 and exon 13 by using direct sequencing., Methods: Genomic DNA was extracted from formalin-fixed, paraffin-embedded GIST tissues. We could obtain 143 sporadic GIST cases appropriate for DNA analysis at exon 17 and 141 at exon 13. Exons 17 and 13 were amplified by using polymerase chain reaction and direct sequencing was conducted., Results: No mutation was found at exon 17, and only one case with the mutation at exon 13 was observed. The GIST with the mutation at exon 13 was large and showed frequent mitosis, and the patient died of the recurrent GIST 3 years after the first operation., Conclusion: The mutation at exons 17 or 13 was considered to be very rare in sporadic GIST.

Background: Diabetes mellitus is a well-known cause of gastrointestinal dysmotility. The pathogenesis of diabetic gastroenteropathy is mainly considered to be a neuropathy, but the cause of dysmotility remains unknown. Interstitial cells of Cajal (ICC), which express c-kit receptor tyrosine kinase (KIT), are considered to be pacemaker cells for the gastrointestinal movement. Therefore, we investigated a possible involvement of ICC in the pathogenesis of diabetic gastroenteropathy in humans., Methods: The KIT-positive cells in the proper muscle layer of the colon were detected by immunohistochemistry in patients with diabetes mellitus and normal control subjects. Mast cells, which are also known to express KIT, were detected by staining with Alcian blue. The numbers of KIT-positive cells and Alcian blue-positive cells in the proper muscle layer were counted under the microscope and the number of KIT-positive cells apart from Alcian blue-positive cells was calculated., Results: In the normal control subjects, KIT-positive cells were located at the myenteric plexus region and in the circular muscle layer of the colon. Their distribution pattern was similar to that of ICC. The average number of KIT-positive cells, apart from mast cells (which reflects the number of ICC), in patients with diabetes mellitus was approximately 40% of that found in normal subjects., Conclusions: Deficiency of ICC might be related to the pathogenesis of diabetic gastroenteropathy in humans.

A family with multiple gastrointestinal stromal tumors (GISTs), a new type of germline mutation of KIT gene, and dysphagia is reported. The mutation was observed at Asp-820 in tyrosine kinase (TK) II domain. Mutations in TK II domain have been found in mast cell and germ cell tumors but not in GISTs, and the present family members are the first reported cases of GISTs with TK II domain mutations, including sporadic GISTs. Because interleukin 3-dependent Ba/F3 murine lymphoid cells transfected with the mutant KIT complementary DNA grew autonomously without any growth factors and formed tumors in nude mice, the mutation was considered to be gain-of-function type. Family members with the germline KIT mutation reported dysphagia, but those without the mutation did not. The mechanism of dysphagia was examined with gastrointestinal fiberscopy, endoscopic ultrasonography, and esophageal manometry. No mechanical obstruction was found, and the esophagus was not remarkably dilated. In the family members with dysphagia, endoscopic ultrasonography at the esophagocardiac junction showed a thickened hyperechoic layer between the circular and longitudinal muscle layers, suggesting hyperplasia of interstitial cells of Cajal at the myenteric plexus layer. Manometry showed low resting lower esophageal sphincter pressure and abnormal simultaneous contractions of the esophagus without normal peristalsis. These findings indicate that the dysphagia of the present family is different from typical achalasia. This is the first report of familial dysphagia caused by germline gain-of-function mutation of the KIT gene at the TK II domain.

Loss-of-function mutations of the c-kit receptor tyrosine kinase (KIT) result in depletion of mast cells and interstitial cells of Cajal (ICCs). In contrast, gain-of-function mutations of KIT induce neoplasms of mast cells and ICCs. In humans, the sites of mutations are different between mast cell neoplasms and those of ICCs. The former were found in the juxtamembrane domain between the transmembrane and tyrosine kinase domains, and the latter in the tyrosine kinase domain. Moreover, the mechanism of constitutive activation is different. Point mutations and/or deletions in the juxtamembrane domain induced the KIT dimerization, and the dimerized KIT was activated. A point mutation at the particular aspartic acid in the tyrosine kinase domain induced spontaneous activation without forming dimers. Mutations of the c-kit gene are a good model for understanding the relationship between mutations and diseases in both humans and mice.

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the human gastrointestinal tract. Previous studies of GISTs found gain-of-function mutations of the c-kit gene, which encodes a receptor tyrosine kinase (KIT). All the mutations were confined to exon 11, which encodes the juxtamembrane domain. By further examination of the whole coding region of c-kit complementary DNA in 35 GISTs, two were found to show the identical mutation at exon 9, which encodes the extracellular domain. The aims of the present study were to examine the frequency of the extracellular domain mutation and to determine whether the mutation is a gain-of-function type or not. Genomic DNA was extracted from paraffin-embedded tissues of 133 GISTs and exon 9 of the c-kit gene was amplified by polymerase chain reaction. Screening of the mutation was carried out by single-strand conformation polymorphism analysis and direct sequencing was done. Mutant c-kit cDNA was transfected into 293T human embryonic kidney cells and the magnitude of autophosphorylation of the mutant KIT was examined with or without the ligand of KIT, stem cell factor (SCF). In total, seven GIST cases (approximately 5%) were found with the identical mutation at exon 9. The mutant KIT exhibited constitutive autophosphorylation without SCF stimulation. The prognosis of the patients with the extracellular domain mutation was comparable to that of the patients with the juxtamembrane domain mutation., (Copyright 2001 John Wiley & Sons, Ltd.)

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the gastrointestinal tract. Recently, we found that GISTs expressed KIT, a receptor tyrosine kinase encoded by the protooncogene c-kit. We propose that GISTs may originate from interstitial cells of Cajal (ICCs), which are considered to be pacemaker cells for the autonomous movement of the gastrointestinal tract. There are major two reasons for this proposal: one is that both GISTs and ICCs are double-positive for KIT and CD34, and the other is that multiple GISTs appear to develop from diffuse ICC hyperplasia in germline mutations of the c-kit gene. Because somatic gain-of-function mutations of the c-kit gene are observed in solitary GISTs, and because the germline gain-of-function mutations of the c-kit gene are observed in familial and multiple GISTs, the gain-of function mutations of the c-kit gene are considered to be a cause of the development of GISTs.

The c-kit receptor tyrosine kinase encoded by the white-spotting (W) gene is highly expressed in rat hippocampal CA1-CA4 regions. We found an impaired spatial learning and memory in homozygous c-kit (Ws/Ws) mutant rats that have a 12-base deletion in the tyrosine kinase domain of the c-kit gene and a very low kinase activity. Electrophysiological studies in hippocampal slices revealed that the long-term potentiation (LTP) induced by the tetanic stimulation (100 Hz, 1 sec) in the mossy fiber (MF)-CA3 pathway, but not in the Schaffer collaterals/commissural-CA1 pathway, was significantly reduced in c-kit mutants compared with wild-type (+/+) rats. The paired-pulse facilitation (PPF) was measured before the tetanus and after the establishment of the LTP in each slice. The initial PPF in the MF-CA3 pathway positively correlated with the amplitude of the LTP in the wild-type rats but not in the c-kit mutant rats. Furthermore, they failed to show the normal characteristics observed in the MF-CA3 pathway of +/+ rats; that is, the negative correlation between the initial PPF and the changes in PPF measured after the LTP. These findings suggest an involvement of SCF/c-kit signaling in hippocampal synaptic potentiation and spatial learning and memory.

The proto-oncogene KIT encodes the receptor tyrosine kinase KIT. Gain-of-function mutations in the juxtamembrane domain of KIT have been reported in human gastrointestinal stromal tumors. In a family with multiple gastrointestinal stromal tumors and diffuse hyperplasia of myenteric plexus layer, we have identified another mutation of KIT, a single base mutation, resulting in the substitution of Glu for Lys(642) in the kinase I domain, and studied its biological effect in a cellular system. The mouse homologue of the human KIT mutant was generated by site-directed mutagenesis and stably transfected into the interleukin-3-dependent Ba/F3 murine cell line. The oncogenic potential of the mutated KIT was assessed in vitro by a proliferation assay and in vivo by transplantation into nude mice. Transfected Ba/F3 cells grew autonomously in absence of growth factors and formed tumors in nude mice. Substitution of Glu for Lys(642) is an oncogenic mutation in the tyrosine kinase domain of KIT. As germline heterozygous mutation, it causes a diffuse hyperplasia of myenteric interstitial cells of Cajal during embryonic development and occurrence of multiple gastrointestinal stromal tumors at adulthood.

Nonepithelial malignancies of the large bowel are rare. A new disease entity, gastrointestinal stromal tumors, has attracted attention among primary mesenchymal tumors of the gastrointestinal tract. Here we present a case of spindle-cell sarcoma of the rectum, lacking either smooth muscle cells or neural elements. Immunohistochemical findings and sequencing of the c-kit proto-oncogene diagnosed this tumor as a malignant gastrointestinal stromal tumor of the rectum.

Protooncogene c-kit encodes a receptor tyrosine kinase, KIT. Interstitial cells of Cajal (ICCs) that are important for the autonomous movement of the gastrointestinal tract essentially require the normal function of the KIT for their development. Therefore, germline loss-of-function mutations of the c-kit gene cause deficiency of ICCs that results in disturbed gastrointestinal movement. On the other hand, somatic gain-of-function mutations of the c-kit gene induce gastrointestinal stromal tumors (GIST) that are considered to originate from ICCs. Moreover, germline gain-of-function mutations of the c-kit gene are a cause of familial development of multiple GISTs.

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. Gain-of-function mutations in the juxtamembrane domain of the c-kit gene have been found in several GISTs. In this study, we examined the correlation between the presence of c-kit mutation and prognosis in 124 cases of GIST. DNA samples were extracted from paraffin sections. Exon 11 of the c-kit gene encoding the juxtamembrane domain and exon 17 encoding the kinase domain were amplified by PCR and sequenced. Most GISTs (89%) express the KIT protein, and missense mutations of exon 11 were found in 71 of 124 GISTs (57%). No mutations were detectable in exon 17. These 71 mutation-positive GISTs were larger in size and had more frequently invaded adjacent tissues than did the 53 mutation-negative GISTs. Histologically, the mutation-positive GISTs showed higher mitotic figures and more necrosis and hemorrhage. The patients with mutation-positive GISTs showed more frequent recurrences (P = 0.0005) and higher mortality (P = 0.0001) than did those with mutation-negative GISTs. The c-kit mutation was an independent prognostic factor for overall and cause-specific survival of the patients with GISTs. These results suggest that GISTs may be divided into mutation-positive and -negative subtypes. The prognosis was worse in patients with mutation-positive GISTs than in those with mutation-negative GISTs. Thus, mutation of the c-kit gene may be a good prognostic marker of GISTs.

Interstitial cells of Cajal (ICC) are believed to initiate the basic contractile activity of the gastrointestinal tract. Interstitial cells of Cajal express c-kit receptor tyrosine kinase and are deficient in Ws/Ws mutant rats with a small deletion of the c-kit gene. As Ws/Ws rats show remarkable bile reflux to the stomach, the contraction pressure of the pylorus was compared between Ws/Ws and control +/+ rats. The contraction pressure of the pylorus was measured using a microtransducer, which was inserted through a pin-hole in the anterior wall of the stomach under anesthesia. The magnitude of bile reflux was estimated by measuring the content of bile acids in the stomach. The c-kit messenger RNA-expressing cells were detected by in situ hybridization. Frequency and the maximum pressure of the contraction were comparable between Ws/Ws and +/+ rats, but the duration of the contraction was significantly shorter in Ws/Ws rats than in +/+ rats. The number of c-kit messenger RNA-expressing ICC in the pylorus of Ws/Ws rats was 1.7% that of +/+ rats. The bile reflux observed in Ws/Ws rats was attributed to the decrease in the duration of the pyloric contraction, which appeared to result from the deficiency of c-kit messenger RNA-expressing ICC.

Background & Aims: The c-kit gene encodes a receptor tyrosine kinase (KIT). Recently, we found gain-of-function mutations of the c-kit gene in gastrointestinal stromal tumors (GISTs). All mutations were confined within the 11 amino acids (Lys-550 to Val-560) in the juxtamembrane domain, but one GIST showed a novel deletion-type mutation at codon 579 (Asp) in the juxtamembrane domain. The aim of this study was to clarify whether the mutation is activating., Methods: Mutant c-kit cDNA was transfected into an interleukin 3 (IL-3)-dependent Ba/F3 murine lymphoid cell line, and the magnitude of autophosphorylation of the mutant KIT was examined with or without stem cell factor (SCF), a ligand of KIT. An in vitro kinase assay was also performed. The biological behavior of the transfectant was estimated by both an in vitro proliferation assay and in vivo transplantation to nude mice., Results: The mutant KIT exhibited constitutive phosphorylation and strong kinase activity without SCF. The transfectant grew autonomously without IL-3 and SCF, and it formed tumors in nude mice., Conclusions: Deletion at codon 579 (Asp) in the juxtamembrane domain of the c-kit gene is a novel gain-of-function mutation other than the region between Lys-550 and Val-560.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the human digestive tract, but their molecular etiology and cellular origin are unknown. Sequencing of c-kit complementary DNA, which encodes a proto-oncogenic receptor tyrosine kinase (KIT), from five GISTs revealed mutations in the region between the transmembrane and tyrosine kinase domains. All of the corresponding mutant KIT proteins were constitutively activated without the KIT ligand, stem cell factor (SCF). Stable transfection of the mutant c-kit complementary DNAs induced malignant transformation of Ba/F3 murine lymphoid cells, suggesting that the mutations contribute to tumor development. GISTs may originate from the interstitial cells of Cajal (ICCs) because the development of ICCs is dependent on the SCF-KIT interaction and because, like GISTs, these cells express both KIT and CD34.

Interstitial cells in the circular muscle layer of the stomach of the Ws/Ws mutant rat, which lacks c-kit-expressing cells, and its siblings have been studied by electron microscopy. In the sibling control rats, two types of interstitial cells are found lying in close association with nerve bundles. Cells of the first type are characterized by electron-dense cytoplasm containing abundant mitochondria, granular endoplasmic reticulum, and Golgi apparatus. Intermediate filaments are richly distributed throughout the perinuclear region and the cell processes. Caveolae, subsurface cisterns, and indistinct basal lamina are observed along the cell membrane. The most conspicuous feature of this cell type is the existence of many large gap junctions that interconnect with the same type of cell, smooth muscle cells, or cells of the second type. Cells of the second type show an ultrastructure similar to fibroblasts, viz., a well-developed Golgi apparatus and granular endoplasmic reticulum whose cisterns often show a dilated form and contain flocculent material. Unlike typical fibroblasts, however, cells of this type also form many gap junctions with cells of the first type and smooth muscle cells. Both types of cells are observed in close apposition to nerve varicosities. Since cells of the first type are absent in the Ws/Ws mutant rat, we concluded that they correspond to c-kit-expressing cells and to interstitial cells of Cajal.

Objectives: Chronic idiopathic intestinal pseudo-obstruction (CIIP) is a syndrome characterized by a failure of intestinal movement, but the cause of dysmotility remains unknown. Because interstitial cells of Cajal (ICCs) are believed to initiate basic contractile activity of the gastrointestinal tract, there is a possibility that changes in ICCs are involved in the development of CIIP. ICCs express c-kit in mice, and it has been reported that the c-kit+ cells, the location and shape of which resemble those in mice, are detected in the human gastrointestinal muscular layer using immunohistochemistry. In the present study, we counted the number of c-kit+ cells in the affected intestine of two patients with myopathic form of CIIP and compared this number with the number of c-kit+ cells in the normal intestine., Methods: The c-kit+ cells in the external muscle layer were detected by immunohistochemistry, and the number of them was counted under the microscope. Mast cells, which are known to express c-kit, were detected by staining with Alcian blue, and the number of them was also counted., Results: Immunohistochemistry revealed that the distribution pattern of c-kit+ cells resembles that of ICCs in the external muscle layer of normal control subjects. The numbers of c-kit+ cells apart from mast cells in two patients with myopathic form of CIIP decreased to about 3% of those in normal subjects., Conclusions: The failure of intestinal movement in patients with CIIP, at least in a subpopulation, might be related to a deficiency of c-kit+ cells, probably ICCs.