Dysadherin expression in gastrointestinal stromal tumors (GISTs)

The purpose of this study was to detect the protein and mRNA expression of dysadherin and to investigate the clinical significance of dysadherin expression in gastrointestinal stromal tumors (GISTs).     

New issues in gastrointestinal stromal tumors of the stomach

Gastrointestinal stromal tumors (GISTs) constitute the majority of mesenchymal tumors of the gastrointestinal tract. The activating mutations in the receptor tyrosine kinases KIT and PDFRA are key molecular changes in the pathogenesis of these tumors and their recognition has led to the development of targeted therapies. Approximately 10% of GISTs, referred to as wild-type, lack such mutations and respond poorly to treatment with tyrosine kinase inhibitors. These GISTs are almost exclusive to the stomach and include primarily tumors that occur in children and tumors that are part of several tumor syndromes. Recent studies have shown that most wild-type GISTs are succinate dehydrogenase deficient. This review summarizes current advances in the molecular biology of GISTs and discusses the clinical and pathologic features associated with different genotypes.     

Gastrointestinal stromal tumors with exon 8 c-kit gene mutation might occur at extragastric sites and have metastasis-prone nature

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.     

Gastrointestinal stromal tumors in Koreans: it's incidence and the clinical, pathologic and immunohistochemical findings

Seven hundred forty seven cases of gastrointestinal stromal tumors (GISTs) in Koreans who were diagnosed between 2001 and 2002 were analyzed to evaluate their occurrence and their clinical, pathologic and immunohistochemical findings. The most frequent location of tumor was in the stomach (63%), followed by the small intestine (30%), the colorectum (5%), and the esophagus (2%). c-kit expression was found in 93.6% of the cases, while CD34, SMA and S-100 protein was positive in 80.1%, 28.2%, and 20.2%, respectively. c-kit positivity was high in the stomach (94.2%) and small intestine (94.6%), while it was relatively low in the colorectum (85.0%), and esophagus (81.2%). The positivity for CD34 was correlated with the higher risk of GISTs (p = 0.04). Follow up of the patients showed that 58 primary GISTs patients died and 20 of these patients were recurrent or metastatic at the time of diagnosis. The pathologic diagnosis to predict the risk of aggressive behavior of GISTs was correlated with the numbers of tumor, clinical stage, epithelioid histologic type, cellularity, cellular atypia, necrosis, and mucosal invasion (p = 0.00). GISTs with a poor prognosis were closely related to the clinical stage at presentation, the locations of the tumor, and the ages of the patients.     

Characterization of various types of mast cells derived from model mice of familial gastrointestinal stromal tumors with KIT-Asp818Tyr mutation

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.     

Electron microscopic and immunohistochemical studies of gastrointestinal stromal tumors

Sixteen gastrointestinal stromal tumors (GISTs) were studied by immunohistochemical analysis and an ultrastructural procedure. The tumor locations were as follows: esophagus (2), stomach (7), small intestine (3), and large intestine (4). Four of the lesions were classified as malignant, 2 as borderline, and 10 as benign. On the basis of the immunohistochemical analysis, the tumors were classified as follows: 1 as myogenic type, 2 as Schwann cell type, 8 as Cajal cell type (including 2 gastrointestinal autonomic nerve tumors, GANTs), and 5 as mixed-cell type. In each subtype the phenotype was compared to the ultrastructural findings. Myogenic and Schwann cell type revealed ultrastructurally smooth muscle differentiation and schwannian tumor. All 8 tumors of the Cajal cell type revealed interdigitating cytoplasmic processes with occasional clusters of filopodia. Two tumors were subdivided as GANT. Five tumors of mixed-cell type were composed of a mixture of cells with variable myogenic features or variable neural differentiation. We confirmed in this study that immunohistochemical analysis reflected electron microscopic findings.     

胃间质瘤致胃套叠一例

患者女,64岁,因"间断呕吐咖啡样物4 d"入院。患者主诉4 d前无明显诱因出现恶心,呕吐咖啡样物质,共呕吐5次,无晕厥,无意识不清。自服吗丁啉呕吐减轻,仍有腹痛,遂就诊河北省沧州市中心医院。查体:神志清楚,语言流利,腹部平坦,未见胃肠型及蠕动波,触诊腹部柔软,剑突下压痛,无反跳痛及肌紧张,肝脾肋下未触及,肝区及双肾区叩击痛阴性,移动性浊音阴性,肠鸣音正常。既往身体健康,否认高血压病、冠心病、糖尿病史,以及肝炎、结核等传染病史;无手术、外伤、输血史及过敏史。     

Increased cyclin D3 expression significantly correlates with p27 nuclear positivity in gastrointestinal stromal tumors

Gastrointestinal stromal tumors, the most common mesenchymal tumors of the gastrointestinal tract, are characterized by strong expression of c-Kit protein. Recently, it has been shown that gastrointestinal stromal tumors may also contain alterations of genes involved in the regulation of cell cycle. In this study, we evaluate the prevalence and clinical significance of cyclin D1 and D3, Ki-67, p27, and retinoblastoma protein expression in a group of 50 human gastrointestinal stromal tumors selected from the files of the Moffitt Cancer Center. Tissue sections from each case were subjected to immunostaining using the avidin-biotin complex method. Cyclin D1 nuclear positivity was detected in 21 of 50 (42%) and cyclin D3 in 24 of 50 (48%) cases. p27 high immunoreactivity and negative or decreased retinoblastoma protein expression were identified in 33 of 50 (66%) gastrointestinal stromal tumors. In 19 of 50 (38%) tumors, Ki-67 had high labeling index. Direct correlation was observed between cyclin D3 and p27 expression (P < .0001), and between cyclin D1 and retinoblastoma protein (P = .03). Coexpression of cyclin D3 and p27 was demonstrated by immunofluorescence. The p27 protein expression inversely correlated with tumor size (P = .004), but was not correlated with tumor grade (P = .12). Ki-67 directly correlated with both tumor size (P = .03) and tumor grade (P = .008). We report a direct correlation between cyclin D3 and p27 expression in gastrointestinal stromal tumors. Additional alterations in cyclin D1, Ki-67, and retinoblastoma protein expression indicate a disregulated cell cycle in these tumors.     

Biology of gastrointestinal stromal tumour and mechanisms of imatinib resistance

The introduction of imatinib therapy for GISTs has represented a major breakthrough of oncology in the last decade, improving dramatically the prognosis of GIST patients. The discovery of an oncogenic event (kinase mutations) having a major predictive value underlines the need for a paradigm of classification combining thorough pathological examination and molecular analysis. The response to therapy with imatinib is indeed determined by the type of mutation in kinase genes. Genetic analysis should be therefore performed in all cases deserving such a therapy. The study of the resistance has enabled us to discover other important oncogenetic events (e.g. dysregulation of downstream pathways) that are important in the genesis and therapy of other tumours as well. Genetic studies have also allowed a molecular classification of GISTs, thus identifying subsets of GISTs (e.g. SDH-negative, paediatric) that do not behave as the “classical”, RTK-mutated tumours, probably representing different “entities”.     

Genetic and epigenetic alterations of SDH genes in patients with sporadic succinate dehydrogenase‐deficient gastrointestinal stromal tumors

This study aimed to investigate the association of SDH gene mutations and promoter methylation with succinate dehydrogenase‐deficient gastrointestinal stromal tumors (SDH‐deficient GISTs) and to further discuss the potential molecular mechanisms underlying SDHB expression loss in these tumors. First, a total of 26 patients with SDH‐deficient GISTs were selected by identifying the loss of SDHB protein expression and wild‐type for KIT and PDGFRa mutations. Then SDH gene mutations and promoter methylation were detected by DNA sequencing and methylation‐specific polymerase chain reaction, respectively, and the clinical and pathological data of SDH‐deficient GISTs patients were collected and analyzed accordingly. The results of genetic testing demonstrated that 38.46% (10/26) of these patients harbored mutations in SDHB, SDHC, and SDHD genes (3 cases with double mutations). Besides, aberrant promoter methylation of SDH genes was detected in 10 out of 26 cases (38.46%), including 8 cases in SDHA gene, 3 cases in SDHB gene, 1 case in both SDHA and SDHB genes. It is suggested that SDH gene mutations and promoter methylation may contribute to the loss of SDH protein expression in sporadic SDH‐deficient GISTs. This study indicated that the genetic and epigenetic alterations of SDH genes may occur during tumor formation.     

High expression of the RNA-binding protein RBPMS2 in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract and are often associated with KIT or PDGFRA gene mutations. GIST cells might arise from the interstitial cells of Cajal (ICCs) or from a mesenchymal precursor that is common to ICCs and smooth muscle cells (SMCs). Here, we analyzed the mRNA and protein expression of RNA-Binding Protein with Multiple Splicing-2 (RBPMS2), an early marker of gastrointestinal SMC precursors, in human GISTs (n = 23) by in situ hybridization, quantitative RT-PCR analysis and immunohistochemistry. The mean RBPMS2 mRNA level in GISTs was 42-fold higher than in control gastrointestinal samples (p < 0.001). RBPMS2 expression was not correlated with KIT and PDGFRA expression levels, but was higher in GISTs harboring KIT mutations than in tumors with wild type KIT and PDGFRA or in GISTs with PDGFRA mutations that were characterized by the lowest RBPMS2 levels. Moreover, RBPMS2 levels were 64-fold higher in GIST samples with high risk of aggressive behavior than in adult control gastrointestinal samples and 6.2-fold higher in high risk than in low risk GIST specimens. RBPMS2 protein level was high in 87% of the studied GISTs independently of their histological classification. Finally, by inhibiting the KIT signaling pathway in GIST882 cells, we show that RBPMS2 expression is independent of KIT activation. In conclusion, RBPMS2 is up-regulated in GISTs compared to normal adult gastrointestinal tissues, indicating that RBPMS2 might represent a new diagnostic marker for GISTs and a potential target for cancer therapy.     

Mutation analysis of gastrointestinal stromal tumors: increasing significance for risk assessment and effective targeted therapy

Molecular characterization of gastrointestinal stromal tumors (GISTs) plays an increasing role not only for the patient's prognosis but also for treatment options and in the context of resistance to therapy. Several mutational subtypes in KIT or platelet-derived growth factor receptor-alpha (PDGFRalpha) have been identified to be correlated with a different clinical behavior of GISTs. In KIT exon 11, deletions in the proximal part are associated with a high metastatic risk, whereas duplications in the distal part lead to a less aggressive phenotype. GISTs of the small bowel with a duplication in KIT exon 9 are often high risk tumors. In contrast, PDGFRalpha exon 18 mutated GISTs tend to have a low malignant potential. The authors suggest to include these molecular data together with classical parameters such as mitotic count and tumor size into the risk assessment of GISTs. The first choice for treatment of GISTs is still the surgical resection. In advanced tumors, which cannot be R0 resected, the neoadjuvant treatment with the tyrosine kinase inhibitor imatinib is now well established. Furthermore, an adjuvant treatment of locally R0-resected intermediate and high risk tumors is evaluated in several international clinical trials. For metastatic disease, treatment with imatinib is still the first option, but with new upcoming substances, the molecular characterization of GISTs may become mandatory. Very recently, it has been shown that sunitinib may be especially effective in GISTs with KIT exon 9 mutation, whereas these tumors show only an intermediate response to imatinib. A European Organisation for Research and Treatment of Cancer clinical trial randomizing patients according to their mutational status is under preparation. Secondary resistance to imatinib treatment is increasing, at least partly due to secondary mutations in the tyrosine kinase domain of the KIT receptor. Once a lesion has been shown to carry such a mutation, the local excision may be useful, mean while still responding metastases are further controlled by continuing imatinib. Taken together, the molecular characterization of GISTs turns out to play a central role before and during the treatment with tyrosine kinase inhibitors, which have improved the treatment of GIST patients dramatically.     

Rectal gastrointestinal stromal tumor as an incidental finding in a patient with rectal polyps

A patient who was diagnosed as rectal polyps in the local hospital went to our hospital for surgical treatment. Abdominal CT demonstrated a large irregular extra-luminal tumor of at least 5 cm cross-section on the ventral side of the lower rectal wall. Intraoperatively, a large irregular extra-luminal tumor (about 5×4.5×4 cm) was found. Anterior resection with end colostomy and rectal stump (Hartmann’s procedure) was performed. Postoperative histological examination showed simultaneous development of rectal GIST and polyps.     

Advances in preclinical therapeutics development using small animal imaging and molecular analyses: the gastrointestinal stromal tumors model

The large use of target therapies in the treatment of gastrointestinal stromal tumors (GISTs) highlighted the urgency to integrate new molecular imaging technologies, to develop new criteria for tumor response evaluation and to reach a more comprehensive definition of the molecular target. These aspects, which come from clinical experiences, are not considered enough in preclinical research studies which aim to evaluate the efficacy of new drugs or new combination of drugs with molecular target. We developed a xenograft animal model GIST882 using nude mice. We evaluated both the molecular and functional characterization of the tumor mass. The mutational analysis of KIT receptor of the GIST882 cell lines and tumor mass showed a mutation on exon 13 that was still present after in vivo cell growth. The glucose metabolism and cell proliferation was evaluated with a small animal PET using both FDG and FLT. The experimental development of new therapies for GIST treatment requires sophisticated animal models in order to represent the tumor molecular heterogeneity already demonstrated in the clinical setting and in order to evaluate the efficacy of the treatment also considering the inhibition of tumor metabolism, and not only considering the change in size of tumors. This approach of cancer research on GISTs is crucial and essential for innovative perspectives that could cross over to other types of cancer.     

Bone metastasis in gastrointestinal stromal tumors preferentially occurs in patients with original tumors in sites other than the stomach

Bone metastases are rare in gastrointestinal stromal tumors (GISTs) and data on the clinicopathological profiles are lacking. The purpose of this report was to identify the clinicopathological profiles of this rare clinical setting by evaluating 23 cases, four of which were our own and the additional 19 were from the relevant English literature. In 18 cases, the primary GISTs occurred in sites other than the stomach, although a high proportion of these tumors do arise in the stomach. All tumors at the disease presentation had more than a low risk of recurrence, with most tumors either at a high risk or initially malignant with liver metastasis. In four cases, bone metastasis was the primary metastatic manifestation. Although rare in GISTs, bone metastasis should be considered in patients with primary tumors at a high risk for recurrence or in initially malignant tumors with liver metastasis, especially with primary tumors in sites other than the stomach.     

Multiple sporadic gastrointestinal stromal tumors concomitant with ampullary adenocarcinoma: A case report with KIT and PDGFRA mutational analysis and miR-221/222 expression profile

GISTs originating multifocally at different GI sites, in patients lacking familial syndromes, could be interpreted as recurrent/metastatic disease. MiR-221/222 have recently been identified as regulators of KIT expression in GISTs. We report the first case of synchronous GISTs in the stomach and duodenum concomitant with an ampullary adenocarcinoma. Different CD117 expression patterns could be related to different KIT mutational status in the two lesions: gastric GIST showed a dot-like pattern and lacked KIT mutations; duodenal GIST had a strong membranous expression pattern, likely due to KIT exon 9 duplication, which is associated with lower response to imatinib. MiR-221/222 were downregulated in GISTs as compared with normal tissue (p < 0.05) and expressed increased levels in the gastric GIST as compared with duodenal one (p < 0.05). Our data support an independent origin of the two GISTs. Determining whether these tumors are multiple primaries or recurrencies is helpful to predict their malignancy and to select proper treatment.     

Pathology of gastrointestinal stromal tumors

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.     

Diagnosis and treatment of gastrointestinal stromal tumors of the stomach: report of 28 cases

We retrospectively analyzed 28 patients with gastric gastrointestinal stromal tumors (GISTs) at our hospital to investigate their clinical features, diagnosis, and treatment. All patients underwent surgical resection. There were 18 cases with subtotal gastrectomy, 8 cases with partial gastrectomy, 1 case with total gastrectomy, and 1 case with subtotal gastrectomy combined with right hemihepatectomy. Based on pathological findings, the tumors were benign in 16 cases (57%), borderline in 2 cases (7%), and malignant in 10 cases (36%). The tumor diameter was significantly correlated with the malignancy of gastric GISTs (3.5+/-1.6 cm in benign tumors, vs 7.5+/-1.3 cm in malignant tumors, p<0.05). Immunohistochemical staining for CD117 and CD34 was positive in 26 (93%) and 17 (61%), respectively. The mean follow-up period ranged from 6 to 60 mo in 23 of the patients, and the other 5 patients (all with benign tumors) were lost to follow-up. No recurrence or metastasis was found in patients with benign gastric GISTs. Four cases of malignant GISTs (17%, 4/23) had liver metastasis or intra-abdominal dissemination, and 2 of them received a second resection for liver metastasis. Four cases of malignant gastric GISTs died with tumors more than 10 cm in maximum diameter, 3 of them died of liver metastasis and multiple organ failure, and 1 died of myocardial infarction. Excluding 2 patients with benign tumors that were followed for <3 yr, the 3-yr survival rate was 81% (17/21) in this group, and 60% (6/10) in the patients with malignant gastric GISTs. In conclusion, the prognosis is related to the tumor size and the number of mitoses seen on histological examination. Positive detection of CD117, combined with other markers and pathological features, is of great importance in the differential diagnosis of gastric GISTs. Complete resection with negative margins remains the fundamental objective in the surgical management of gastric GISTs.