Clinical significance of oncogenic KIT and PDGFRA mutations in gastrointestinal stromal tumours

Molecular and Clinicopathological Features of Gastrointestinal Stromal Tumors in Vietnamese Patients

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal neoplasms of the gastrointestinal tract. Management of GIST patients is currently based on clinicopathological features and associated genetic changes. However, the detailed characteristics and molecular genetic features of GISTs have not yet been described in the Vietnamese population.

METHODS

We first identified 155 patients with primary GIST who underwent surgery with primary curative intent between 2011 and 2014 at University Medical Center at Ho Chi Minh City, Vietnam. We evaluated the clinicopathological features and immunohistochemical reactivity to p53 and Ki-67 in these patients. Additionally, KIT genotyping was performed in 100 cases.

RESULTS

The largest proportion of GISTs was classified as high-risk (43.2%). Of the 155 GISTs, 52 (33.5%) were positive for Ki-67, and 58 (37.4%) were positive for p53. The expression of Ki-67 and p53 were correlated with mitotic rate, tumor size, risk assessment, and tumor stage. Out of 100 GIST cases, KIT mutation was found in 68%, of which 62 (91.2%) were found in exon 11, two (2.9%) in exon 9, and four (5.8%) in exon 17. No mutation in exon 13 was identified. Additionally, KIT mutations did not correlate with any clinicopathological features.

CONCLUSIONS

The expression of Ki-67 and p53 were associated with high-risk tumors. Mutations in exon 11 were the most commonly found, followed by exon 17 and exon 9. Additionally, KIT mutation status was not correlated with any recognized clinicopathological features.

Preclinical development of HQP1351, a multikinase inhibitor targeting a broad spectrum of mutant KIT kinases, for the treatment of imatinib-resistant gastrointestinal stromal tumors

Background

Imatinib shows limited efficacy in patients with gastrointestinal stromal tumors (GISTs) carrying secondary KIT mutations. HQP1351, an orally bioavailable multikinase BCR-ABL inhibitor, is currently in clinical trials for the treatment of T315I mutant chronic myelogenous leukemia (CML), but the potential application in imatinib-resistant GISTs carrying secondary KIT mutations has not been explored.

Methods

The binding activities of HQP1351 with native or mutant KIT were first analyzed. Imatinib-sensitive GIST T1 and imatinib-resistant GIST 430 cells were employed to test the in vitro antiproliferative activity. Colony formation assay, cell migration assay and cell invasion assay were performed to evaluate the clonogenic, migration and invasion ability respectively. Flow cytometry and western blot analysis were used to detect cell apoptosis, cell cycle and signaling pathway. In vivo antitumor activity was evaluated in mouse xenograft models derived from GIST cell lines.

Results

HQP1351 potently inhibited both wild-type and mutant KIT kinases. In both imatinib-resistant and sensitive GIST cell lines, HQP1351 exhibited more potent or equivalent antiproliferative activity compared with ponatinib, a third generation BCR-ABL and KIT inhibitor. HQP1351 led to more profound inhibition of cell colony formation, cell migration and invasion, cell cycle arrest and cell apoptosis than ponatinib. Furthermore, HQP1351 also inhibited p-KIT, p-AKT, p-ERK1/2, and p-STAT3 to a higher extent than ponatinib. Finally, in xenograft tumor models derived from imatinib-resistant GIST cancer cell lines, HQP1351 exhibited antitumor activity superior to ponatinib.

Conclusions

Collectively, our in vitro and in vivo results suggest that the therapeutic application of HQP1351 in imatinib-resistant GIST patients deserves further investigation in clinical trials.

Justification of direct Sanger sequencing application for detection of KIT and PDGFRα gene mutations in formalin-fixed, paraffin-embedded samples from gastrointestinal stromal tumours

AIMS

The knowledge concerning genetic background of gastrointestinal stromal tumours (GISTs) is well recognised, and the accurate detection of KIT and PDGFRα mutations is of great importance for the process of disease diagnosis and patient's treatment. In this study, we compare the usefulness of real-time PCR-based techniques and Sanger sequencing to detect mutations of both genes in 41 formalin-fixed, paraffin-embedded GIST samples.

METHODS

The analysis encompassed most frequently mutated coding regions of KIT (exons 9, 11, 13 and 17) and PDGFRα (exons 12, 14 and 18) genes. The GIST Mutation Detection Kit (EntroGen), direct Sanger sequencing and high-resolution melting (HRM) analysis were applied to conduct the study.

RESULTS

With the application of EntroGen kit, we found alterations in 22/38 samples, with Sanger sequencing variants were found in 36/41 samples. The concordant results for both methods were observed in 19/38 samples. With subsequently applied HRM analysis, we have confirmed that all samples, except one, harboured alterations in the regions indicated by Sanger sequencing.

CONCLUSIONS

Our results show that in GIST samples, carrying a broad spectrum of deletions, Sanger sequencing is a better, more sensitive method for mutational analysis of KIT and PDGFRα genes.

A rare simultaneous coexistence of epithelioid gastrointestinal stromal tumors and schwannoma in the stomach: a case report

BACKGROUND

Gastrointestinal stromal tumors (GISTs), a type of mesenchymal tumor in the gastrointestinal tract, are believed to be closely associated with PDGFRA and C-KIT mutations. Schwannoma in the stomach, which is an unusual location, is a rare disorder. The simultaneous occurrence of the two diseases is rarer than metachronous occurrences, and its pathological characteristics have not been reported to date. We present a case report on a patient with simultaneous coexistence of gastric schwannoma and GISTs.

CASE PRESENTATION

A 39-year-old female visited our hospital complaining of intermittent abdominal pain for the previous 3 months. CT revealed a 3.4 cm slight homogeneous enhancement in the lesser curvature of the stomach; the mass was nodular soft tissue, which was removed by radical surgery. Two solid tumors with different volumes were located in the stomach. Histologically and immunohistochemically different, the larger tumor consisted of spindle cells surrounded by a peripheral lymphoid cuff, and was positive for S-100. The larger tumor was therefore classified as a gastric schwannoma. The smaller tumor was composed of medium-sized round, oval cells with amphiphilic granular cytoplasm; vacuolization was also observed. The tumor cells were positive for DOG1 and sporadically positive for CD34 and CD117. Hence, the smaller tumor was diagnosed as epithelioid GISTs. Sanger sequencing revealed that the GIST tumor cells contained a deletion mutation (c.2527_2538 del12,843-846del4), which was located in exon 18 of PDGFRA.

CONCLUSION

GISTs combined with gastric schwannoma are a considerably rare subgroup of gastric tumors. Related clinical research is comparatively weak, and the mechanism remains unknown. We reviewed related articles to provide knowledge to improve the correct identification, diagnosis and management of patients with gastric cancer. All pathologists involved in the diagnosis and clinicians involved in the treatment should be aware of this new kind of disease pattern to improve their understanding of the disease.

Clinico-Pathological Characteristics and Mutational Analysis of Gastrointestinal Stromal Tumors from India: A Single Institution Experience

Background:

Gastrointestinal stromal tumor (GIST) is the most common type of mesenchymal neoplasm of gastrointestinal tract. The incidence of GIST in India is not known and its treatment strategy in our country is largely derived from studies in other global populations. Some of the most important features of this type of cancer include its size, site of origin, mitotic index, histology and Immunohistochemistry. In this report we have studied these parameters in the Indian GIST patients presenting at our center. Additionally, we have also studied the mutational spectrum of these GISTs by next generation sequencing.

Methods:

Thirty one Indian patients of GIST were enrolled in this study and information regarding age, gender, tumor location and size was collected from their records. Immunohistochemistry studies were performed by the pathologist. Mutational analysis of these samples was performed by next generation sequencing.

Results and Discussion:

The most common site of GIST occurrence in our study was stomach. The tumor size for all 31 patients ranged between 0.6 cms to 20 cms. A spindle-cell pattern was present in 24 out of 31 of the cases. 29 out of 31 subjects were positive for CD117 expression. C-KIT was the most highly mutated gene indentified in our patients. Apart from these findings we observed many similarities as well as dissimilarities between the results of our study and literature published previously.

Conclusions:

The dissimilarities in the results of our study and published literature could be attributed to the genetic or ethnic differences that exist between the Indian population and other global populations. The results of our study warrant a need to conduct studies of GIST in a much larger population of India. Such large scale studies may also help in better treatment and/or prevention of GIST in developing countries like India.

N822K- or V560G-mutated KIT activation preferentially occurs in lipid rafts of the Golgi apparatus in leukemia cells

Background

KIT tyrosine kinase is expressed in mast cells, interstitial cells of Cajal, and hematopoietic cells. Permanently active KIT mutations lead these host cells to tumorigenesis, and to such diseases as mast cell leukemia (MCL), gastrointestinal stromal tumor (GIST), and acute myeloid leukemia (AML). Recently, we reported that in MCL, KIT with mutations (D816V, human; D814Y, mouse) traffics to endolysosomes (EL), where it can then initiate oncogenic signaling. On the other hand, KIT mutants including KIT^D814Y in GIST accumulate on the Golgi, and from there, activate downstream. KIT mutations, such as N822K, have been found in 30% of core binding factor-AML (CBF-AML) patients. However, how the mutants are tyrosine-phosphorylated and where they activate downstream molecules remain unknown. Moreover, it is unclear whether a KIT mutant other than KIT^D816V in MCL is able to signal on EL.

Methods

We used leukemia cell lines, such as Kasumi-1 (KIT^N822K, AML), SKNO-1 (KIT^N822K, AML), and HMC-1.1 (KIT^V560G, MCL), to explore how KIT transduces signals in these cells and to examine the signal platform for the mutants using immunofluorescence microscopy and inhibition of intracellular trafficking.

Results

In AML cell lines, KIT^N822K aberrantly localizes to EL. After biosynthesis, KIT traffics to the cell surface via the Golgi and immediately migrates to EL through endocytosis in a manner dependent on its kinase activity. However, results of phosphorylation imaging show that KIT is preferentially activated on the Golgi. Indeed, blockade of KIT^N822K migration to the Golgi with BFA/M-COPA inhibits the activation of KIT downstream molecules, such as AKT, ERK, and STAT5, indicating that KIT signaling occurs on the Golgi. Moreover, lipid rafts in the Golgi play a role in KIT signaling. Interestingly, KIT^V560G in HMC-1.1 migrates and activates downstream in a similar manner to KIT^N822K in Kasumi-1.

Conclusions

In AML, KIT^N822K mislocalizes to EL. Our findings, however, suggest that the mutant transduces phosphorylation signals on lipid rafts of the Golgi in leukemia cells. Unexpectedly, the KIT^V560G signal platform in MCL is similar to that of KIT^N822K in AML. These observations provide new insights into the pathogenic role of KIT mutants as well as that of other mutant molecules.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0426-3) contains supplementary material, which is available to authorized users.

A first case report of primary epithelial myoepithelial carcinoma-like renal tumor showing a perivascular pseudorosette-like pattern: Description of morphologic, immunohistochemical, and genetic features

RATIONALE

Over the past decade, although several new entities of renal tumors have emerged, a form of renal cell carcinoma (RCC) that morphologically resembles epithelial-myoepithelial carcinoma has not been reported thus far. Herein, we describe a case of an unusual renal tumor that remained unclassified under a current RCC subtype, and briefly present its morphologic, immunophenotypic, and genetic features.

PATIENT CONCERNS

The patient was an 85-year-old man who presented with hematuria and flank pain. Imaging studies revealed a left renal mass without enlarged lymph nodes. There were no abnormal masses or nodules in other organs.

DIAGNOSES

The patient underwent no other treatment except the left radical nephrectomy under a clinical diagnosis of invasive urothelial carcinoma and was discharged on the thirteenth day. Histologically, the renal tumor showed biphasic proliferation of epithelial (strongly cytokeratin-positive; P63, P40, and vimentin-negative) and myoepithelial (strongly vimentin-positive; focal P63 and P40-positive; and weakly cytokeratin-positive) cells arranged in a perivascular pseudorosette-like pattern. No mutations were detected in multiple gene tests. According to the pathological structure, the patient was diagnosed as primary epithelial myoepithelial carcinoma-like renal tumor.

INTERVENTIONS

To the best of our knowledge, the present tumor has not been previously described, and thus, this variant has not been integrated into a known form of PCC. Therefore, we cannot diagnose this type of tumor with other types of kidney tumors.

OUTCOMES

Three years after primary diagnosis, the patient died of multiple organ failure result from multiple distant metastases.

LESSONS

We present the first case of carcinoma of the kidney with EMC-like features and a perivascular pseudorosette-like growth pattern. Clinicians should be aware of the features of this uncommon variant of RCC to avoid diagnostic delays or misdiagnosis and prevent unnecessary or inappropriate treatment.

Germline c.1A>C heterozygous pathogenic variant in SDHA reported for the first time in a young adult with a gastric gastrointestinal stromal tumour (GIST): a case report

Background

Gastrointestinal stromal tumors (GISTs) represent the most frequent mesenchymal tumor of the gastrointestinal tract. Less than 5% of them seem to be hereditary, being succinate dehydrogenase complex (SDHx) deficient disorders and neurofibromatosis type 1 the more related inherited conditions. Wild type (WT) KIT and PDGFRα GISTs constitute a clue for a hypothetical underlying germline condition.

Case presentation

We present a case of a 20 years old female diagnosed of a gastric WT GIST who developed hepatic metastases during her clinical course. No significant or typical phenotypic features suggestive of a specific syndrome were detected by physical examination. Also, her family history seemed to be irrelevant, since no other cases of GISTs, paragangliomas or pheochromocytomas were reported. Her paternal grandfather died as a consequence of a pituitary adenoma. In light of the age of tumor presentation and somatic features of gastric GIST, we performed genetic testing of SDHx genes. Analysis obtained from peripheral blood sample revealed the presence, in heterozygous state, of the c.1A > C; p.(Met1?) pathogenic variant in the SDHA.

Conclusions

To the best of our knowledge, this is the first published report in which the c.1A > C; p.(Met1?) pathogenic variant in the SDHA is associated with a GIST. SDHA pathogenic variants increase the risk of paraganglioma, pheochromocytoma, GIST, pituitary adenoma and renal cancer in an autosomal dominant inherited condition named paraganglioma syndrome type 5. The absence of family history of tumors in SDHA pathogenic variants carriers could be related to its low penetrance. All patients diagnosed with WT GISTs should be referred to a hereditary cancer genetic counseling unit regardless of the age at presentation or the absence of a suspicious family history.

Gastrointestinal stromal tumor coexisting with disseminated peritoneal leiomyomatosis

Background

A case of gastrointestinal stromal tumor (GIST) coexisting with disseminated peritoneal leiomyomatosis (DPL) is rare. We report a case of GIST coexisting with DPL.

Case presentation

A 50-year-old woman underwent exploratory laparoscopy under a preoperative diagnosis of gastric GIST with an ovarian tumor or peritoneal dissemination in the pelvic space. Laparoscopy showed multiple peritoneal masses in the pelvic space. Intraoperative frozen sectioning of the pelvic tumors showed multiple spindle cells, suggesting leiomyomas or retroperitoneal tumors; however, it was difficult to rule out peritoneal dissemination from GIST. No disseminated lesion was noted near GIST, and hence, we believed that GIST and pelvic lesions had different origins. We achieved R0 resection by partial resection of the stomach, total hysterectomy, and bilateral salpingo-oophorectomy. The postoperative immunohistopathological examination confirmed the final diagnosis of GIST and DPL. The patient has been recurrence free for 10 years.

Conclusions

Immunohistochemical examination is essential for correct diagnosis for GIST and DPL. R0 curative resection should be scheduled after immunohistochemical examination of specimens obtained from exploratory laparoscopy.

Epithelioid variant of gastrointestinal stromal tumor harboring PDGFRA mutation and MLH1 gene alteration: A case report

Gastrointestinal stromal tumors (GISTs) are the most important and common mesenchymal tumors of the gastrointestinal tract, especially in the stomach. GISTs are usually driven by activating mutations in either KIT or PDGFRA genes. It is known that activating gene mutations predicts, to a certain extent, not only the morphology of the tumor cells but also a response to treatment with tyrosine kinase inhibitors. Here, we present a case of an epithelioid variant of GIST harboring PDGFRA and MLH1 gene alterations in the stomach of a 55-year-old Japanese woman. The tumor of 98 mm with multiple cysts showed exophytic growth from the gastric fundus. Histopathologically, it consisted of scattered medium-sized epithelioid tumor cells in a loose myxoid background. Based on c-kit and DOG-1 immunoreactivity and a PDGFRA mutation (p.Trp559_Arg560del), the tumor was diagnosed as an epithelioid variant GIST. Interestingly, it had a gene alteration (p.Met524Ile) in the MLH1 gene of unknown pathogenicity. It was assigned to Group 3a (low risk for malignant behavior). After surgery, the patient has been on imatinib therapy and disease-free for 10 months.

Relationship between efficacy of sunitinib and KIT mutation of patients with advanced gastrointestinal stromal tumors after failure of imatinib: A systematic review

BACKGROUND

A large number of studies have shown that KIT mutations are closely related to the prognosis of gastrointestinal stromal tumors (GISTs). At the same time, sunitinib (SU) has become the second-line recommended drug for GISTs because of its efficacy. We initiated a systematic review to compare the efficacy of SU after failure of Imatinib (IM) in different KIT mutations.

METHODS

We searched for SU-treated patients with advanced GISTs after failed IM treatment by using databases such as PubMed, EMBASE, and the Cochrane Library, up to March 2018. We conducted statistical analyses to calculate the odds ratio (OR), hazard ratio (HR), and 95% confidence interval (CI) using fixed-effects and random-effects models by Review Manager 5.3 software.

RESULTS

We included a total of 474 patients from 3 retrospective studies and 2 cohort studies. Patients with exon 9 mutations had higher clinical benefit (OR = 2.61, 95% CIs = 1.32-5.18, P = .006) rates and longer progression-free survival (progressive disease, HR = 0.51, 95% CIs = 0.36-0.72, P = .0001) compared with exon 11, but there was no statistically significant difference in overall survival (OS, HR = 0.93, 95% CIs = 0.34-2.55, P = .89) and there was greater heterogeneity (Tau = 0.72, Chi = 21.45, df = 3, P < .001, I = 86%). Subgroup analysis suggests that race may be one of the sources of heterogeneity.

CONCLUSION

The results show that efficacy of SU is closely associated with KIT genotypes in GISTs. Moreover, racial factor also directly affects the prognosis of different KIT mutational status, so GISTs patients of different genotypes might also consider the use of targeted drugs in consideration of ethnic differences.

Adjuvant therapy with imatinib in gastrointestinal stromal tumors (GISTs)-review and perspectives

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumor of the gastrointestinal (GI) tract. Most of them (>75%) are driven by an oncogenic initiating event involving activating mutations of the genes encoding for tyrosine kinase, KIT or platelet derived growth factor receptor alpha (PDGFRA). Efficacy of the tyrosine kinase Inhibitor imatinib is now well established for advanced disease. For localized GISTs, 3 years treatment is the recommended adjuvant therapy for high risk patients. Whether a longer duration and selection of patients for this adjuvant therapy in localized GISTs remains is not yet established (PERSIST-5 study). Similarly, it will be important to further refine the definition of the population of GIST patients at high risk of relapse including molecular criteria (Annals of Oncology, ESMO guidelines 2018). This review aims to describe current knowledges on the issue of adjuvant therapy of primary GISTs in view of available results.

Prognostication in Mesenchymal Tumors: Can We Improve?

Prognostication in mesenchymal tumors can be challenging. They exhibit diverse, and sometimes overlapping, histologic features that are not always predictive of their true behavior. This article highlights examples of both traditional and emerging sarcoma biomarkers.

What is the appropriate duration of adjuvant imatinib mesylate treatment for primary gastrointestinal stromal tumors classified according to the strict definition of tumor rupture?

In gastrointestinal stromal tumors (GISTs), rupture is a high-risk feature; however, "tumor rupture" is inconsistently defined, and its prognostic value remains controversial.Six hundred ninety-one patients undergoing surgery for primary nonmetastatic GISTs from 2003 to 2015 at our institution were enrolled. The strict definitions of "tumor rupture" according to the Kinki GIST Study Group (KGSG) were used.The median follow-up time was 64 months. The 5-year recurrence-free survival (RFS) and overall survival (OS) rates in the entire group were 79.3% and 84.1%, respectively. According to the KGSG's definition, tumor rupture occurred only in 24 (3.5%) of 691 patients. For all 691 patients, multivariable analysis showed that tumor rupture, according to KGSG's definition, is one of the independently prognostic factors for both RFS and OS. Twenty-four patients with tumor rupture were further analyzed. Receiving IM for more than 3 years was significantly associated with improved RFS and OS in GISTs patients with tumor rupture.Tumor rupture according to KGSG's definition was an independent predictive factor associated with GIST patient prognosis. More importantly, for GISTs with tumor rupture according to the KGSG's strict definition, receiving IM treatment for ≥3 years should be considered.

FoxM1 is regulated by both HIF-1α and HIF-2α and contributes to gastrointestinal stromal tumor progression

BACKGROUND

FoxM1 plays important regulatory roles in a variety of diseases. However, the functional role of FoxM1 and mechanisms responsible for its expression in gastrointestinal stromal tumor (GIST) is not thoroughly understood.

METHODS

FoxM1 protein expression and biological function were examined in human GIST tissues and cells using immunohistochemistry, quantitative real-time PCR, western blot, CCK-8, wound-healing- and Matrigel invasion assays, respectively. The role of hypoxia-inducible factor (HIF) signaling in FoxM1 expression was investigated using chromatin immunoprecipitation and luciferase reporter and in vivo tumor growth assays.

RESULTS

FoxM1 was highly expressed in highly proliferative and migratory/invasive GIST specimens. Upregulation of FoxM1 was positively correlated with the expression of HIF-1α and HIF-2α in GIST specimens, and hypoxia-induced FoxM1 expression in GIST cells. Functionally, ectopic expression of FoxM1 significantly promoted GIST cell proliferation, cell cycle progression, migration and invasion, whereas the knockdown of endogenous FoxM1 of hypoxic GIST cells had the opposite effects. Molecularly, FoxM1 was transcriptionally regulated by HIF-2α under normoxia, whereas it was upregulated by both HIF-1α and HIF-2α under hypoxia. The xenograft tumor data further confirmed the regulated effect of HIF-1α and HIF-2α on FoxM1, and demonstrated that the simultaneous downregulation of both HIF-1α and HIF-2α inhibited GIST tumor growth.

CONCLUSIONS

Our data demonstrated the critical role of FoxM1 in promoting GIST progression and uncovered a novel HIF-1α/HIF-2α-FoxM1 axis. These findings identify FoxM1 as a possible new molecular target for designing novel therapeutic treatments to control GIST progression.

A Novel Pathological Prognostic Score (PPS) to Identify "Very High-Risk" Patients: a Multicenter Retrospective Analysis of 506 Patients with High Risk Gastrointestinal Stromal Tumor (GIST)

BACKGROUND

To determine the better risk stratification based on surgical pathology and to assess the clinical outcomes after curative resection with a new scoring system in high risk gastrointestinal stromal tumor (GIST) patients.

METHODS

We retrospectively evaluated 506 high-risk GIST patients who underwent curative resection as initial treatment at four centers from 2001 to 2015.

RESULTS

Multivariate analysis revealed that only Ki-67 labeling index (LI) and mitotic index were independent prognostic factors of overall survival (OS). For the two tumor-related pathological factors, Ki-67 LI > 7% and mitotic index ≥ 7/50 high power fields were allocated 1 point each. The total score was defined as the Pathological Prognostic Score (PPS). When Ki-67 LI and mitotic index were replaced by PPS, a multivariate analysis still identified PPS as an independent predictor of OS (HR 2.719; 95% CI 1.309-5.650; P = 0.007). Patients with a PPS of 0, 1, or 2 had a 5-year survival of 91.8, 79.8, and 51.0%, respectively (P = 0.001). Furthermore, an elevated PPS (PPS = 2) was associated with larger tumor size, non-stomach tumor, and open resection (all P < 0.05).

CONCLUSION

The PPS independently predicted postoperative survival in high-risk GIST, and it might facilitate the selection of appropriate treatment strategy for these patients.

Spectrum of the KIT Gene Mutations in Gastrointestinal Stromal Tumors in Arab Patients

Background: Gastrointestinal stromal tumors are the most common mesenchymal tumors of the gastrointestinal tract, which originate from the interstitial cells of Cajal. These tumors are characterized by expression of CD117 and CD34 antigens and activating mutations in the KIT and PDGFRA genes. While KIT and PDGFRA mutations have been extensively studied in other populations, the spectrum of mutations in Arab patients remains unknown. The study aimed at determining the distribution of KIT and PDGFRA mutations and phenotypic characterization of the gastrointestinal stromal tumors in Arab patients. Methods: Sanger sequencing was used to analyze 52 archived gastrointestinal stromal tumors for mutations in the KIT and the PDGFRA genes. Tumor descriptions were obtained from the clinical reports of patients. Results: In these patients, most tumors occur in the stomach, followed by the rest of the digestive tract. A vast majority of tumors express the CD117 and CD34 antigens. Sequencing of the KIT and PDGFRA genes identified five non-synonymous mutations and 26 deletions (25 novel) in exon 11 of the KIT gene. All non-synonymous mutations and deletions affect the juxta-membrane domain, which is known to inhibit ligand-independent activation of the KIT receptor. No mutations were found in the PDGFRA gene. Conclusions: Molecular profiling of the gastrointestinal stromal tumors in Arab patients identified a unique spectrum of mutations in exon 11 of the KIT gene. These data are important for the diagnosis and management of patients of Arab ethnic origin.

Retrospective evaluation of toceranib phosphate (Palladia®) use in the treatment of gastrointestinal stromal tumors of dogs

Background

Gastrointestinal stromal tumors (GISTs) are uncommon intestinal neoplasms in the dog. Literature regarding adjunctive therapy for GISTs in dogs is sparse. High‐risk GISTs in humans respond to tyrosine kinase inhibition in the adjuvant setting.

Objectives

To review cases of toceranib phosphate use in dogs with GISTs and provide initial assessment of possible biological activity. A secondary aim was to evaluate patient and tumor characteristics for possible prognostic value.

Animals

Twenty‐seven dogs with confirmed GISTs based on histopathology and immunohistochemistry treated with toceranib.

Methods

Retrospective study in which cases of toceranib use in dogs with GIST were solicited using the American College of Veterinary Internal Medicine Oncology and Small Animal Internal Medicine listservs.

Results

Five of 7 dogs with gross disease experienced clinical benefit (71%; 3 complete responses, 1 partial response, 1 stable disease). These included 2 dogs with durable responses after toceranib discontinuation. Median progression‐free interval (PFI) in dogs with gross disease was 110 weeks (range, 36‐155 weeks). Median PFI in dogs with microscopic disease was 67 weeks (range, 9‐257 weeks). Metastasis at diagnosis (P = 0.04) and high mitotic index (P < 0.001) were associated with shorter PFI in toceranib‐treated dogs.

Conclusions and Clinical Importance

Biological activity of toceranib is evident in dogs with gross disease. Metastasis of GIST at diagnosis, as well as high tumor mitotic index, was associated with shorter PFI in toceranib‐treated dogs. Larger studies are needed to define postsurgical risk and refine the use of toceranib in dogs with gross and microscopic GIST.

Clinicopathologic features and outcomes of gastrointestinal stromal tumors arising from the esophagus and gastroesophageal junction

Background

Our aim was to characterize the clinicopathological features and outcomes of gastrointestinal stromal tumors (GISTs) arising from the esophagus and gastroesophageal junction (GEJ) and describe the survival of patients treated at our institution as well as from a national hospital-based registry.

Methods

Twenty-eight cases were identified using the Mayo Clinic Cancer Registry from 1997 to 2016, and 1,010 cases from the National Cancer Database (NCDB) between 2004 and 2014, with analysis of TNM staging, histopathological features, mitotic index, immunohistochemical studies, and KIT mutational analysis.

Results

At Mayo Clinic, the tumors ranged in size from 0.3-13 cm (mean 5.40 cm). IHC results were: CD117 (KIT) in 100% (23/23 cases) and DOG1 in 100% (6/6), followed by CD34 (85.7%, 12/14), smooth muscle actin (27.8%, 5/18), desmin (18.2%, 2/11), and S-100 protein (13.3%, 2/15). Mutational analysis (performed in 10 cases) showed KIT exon 11 mutations in 8 cases; KIT mutation was not identified in 2 cases (presumed wild-type). Two-thirds of patients underwent surgery, of which 70% had an esophagectomy. Fourteen patients received adjuvant imatinib mesylate. Five patients had liver metastases at the time of diagnosis; none had lymph node metastases. A total of 38.9% of cases had recurrent or metastatic disease. Complete clinical follow-up was available for 10 patients (median follow-up duration 31.5 months; range, 10-145 months): one (male) had a local recurrence at the anastomotic site and one (female) suffered a liver metastasis; the others were either disease-free or had stable disease at the time of last follow-up. There was a significant association seen among metastatic disease and mitotic count >5/50 high-powered field (HPF) (P=0.016), with median mitotic rate 90/50 HPF (range, 7-500) for metastatic tumors versus 6/50 HPF (range, 0-100) for non-metastatic tumors. For metastatic disease, median tumor size was 7.3 cm (range, 1-66 cm) compared to 4.8 cm (range, 0.02-71 cm) for non-metastatic disease, which was also statistically significant (P≤0.0001). Two hundred and fifty-eight NCDB cases were risk stratified using the Joensuu criteria. Among 89 low risk category tumors, only 2 (2.2%) were ultimately metastatic. A total of 10.9% (15/138) of high risk category tumors were metastatic. The median overall survival (OS) from the time of diagnosis for the Mayo Clinic cohort was 129.5 months (95% CI, 55.7-not reached), with 5-year OS 85.7%. Median OS for the NCDB cohort was 135.95 months (95% CI, 104.08-not reached) with 5-year OS 68.2%. Superior OS was seen in females (HR 0.67, 95% CI, 0.49-0.89, P=0.006).

Conclusions

Among esophageal and GEJ GISTs, metastatic disease was associated with increased mitotic count and increased tumor size. Men were found to have inferior OS. The Joensuu risk criteria were validated for risk stratification of esophageal and GEJ GISTs.

Results of the UK NEQAS for Molecular Genetics reference sample analysis

Aims

In addition to providing external quality assessment (EQA) schemes, United Kingdom National External Quality Assessment service (UK NEQAS) for Molecular Genetics also supports the education of laboratories. As an enhancement to the Molecular Pathology EQA scheme, a human cell-line reference sample, manufactured by Thermo Fisher Scientific (AcroMetrix), was provided for analysis. This contained many variants, present at frequencies between 1% and 17.9%.

Methods

One hundred and one laboratories submitted results, with a total of 2889 test results on 53 genes being reported. Known polymorphisms, 46/2889 (1.59%) results, were excluded. Variants detected in the seven most commonly reported (and clinically relevant) genes, KRAS, NRAS, BRAF, EGFR, PIK3CA, KIT and PDGFRA, are reported here, as these genes fall within the scope of UK NEQAS EQA schemes.

Results

Next generation sequencing (NGS) was the most commonly performed testing platform. There were between 5 and 27 validated variants in the seven genes reported here. Eight laboratories correctly reported all five NRAS variants, and two correctly reported all eight BRAF variants. The validated mean variant frequency was lower than that determined by participating laboratories, with single-gene testing methodologies showing less variation in estimated frequencies than NGS platforms. Laboratories were more likely to correctly identify clinically relevant variants.

Conclusions

Over 100 laboratories took the opportunity to test the ‘educational reference sample’, showing a willingness to further validate their testing platforms. While it was encouraging to see that the most widely reported variants were those which should be included in routine testing panels, reporting of variants was potentially open to interpretation, thus clarity is still required on whether laboratories selectively reported variants, by either clinical relevance or variant frequency.

Gastric Antral Vascular Ectasia Pathogenesis and the Link to the Metabolic Syndrome

PURPOSE OF REVIEW

Gastric antral vascular ectasia (GAVE) is a well-described source of chronic blood loss. We aim to review the previously hypothesized etiologies of GAVE and focus on recent proposed mechanisms, including metabolic syndrome. We will support these theories with newly discovered clinical associations and possible therapeutic implications.

RECENT FINDINGS

Historically, GAVE has been associated with connective tissue disease and liver disease. Based on these associations and its histologic appearance, GAVE has presumed to be caused by mechanical- and hormonally mediated injury. Recent findings have been notable for a clinical association with aspects of the metabolic syndrome. Therefore, the pathogenic etiology may be akin to aspects of the metabolic syndrome via microvascular injury and neoangiogenesis. The potential etiologies of GAVE include hypergastrinemia, mechanical injury, and microvascular injury with neovascular proliferation particularly in the metabolic syndrome. Further research is needed to evaluate these proposed mechanisms and potential targets for treatment.

Silencing of adaptor protein SH3BP2 reduces KIT/PDGFRA receptors expression and impairs gastrointestinal stromal tumors growth

Gastrointestinal stromal tumors (GISTs) represent about 80% of the mesenchymal neoplasms of the gastrointestinal tract. Most GISTs contain oncogenic KIT (85%) or PDGFRA (5%) receptors. The kinase inhibitor imatinib mesylate is the preferential treatment for these tumors; however, the development of drug resistance has highlighted the need for novel therapeutic strategies. Recently, we reported that the adaptor molecule SH3 Binding Protein 2 (SH3BP2) regulates KIT expression and signaling in human mast cells. Our current study shows that SH3BP2 is expressed in primary tumors and cell lines from GIST patients and that SH3BP2 silencing leads to a downregulation of oncogenic KIT and PDGFRA expression and an increase in apoptosis in imatinib-sensitive and imatinib-resistant GIST cells. The microphthalmia-associated transcription factor (MITF), involved in KIT expression in mast cells and melanocytes, is expressed in GISTs. Interestingly, MITF is reduced after SH3BP2 silencing. Importantly, reconstitution of both SH3BP2 and MITF restores cell viability. Furthermore, SH3BP2 silencing significantly reduces cell migration and tumor growth of imatinib-sensitive and imatinib-resistant cells in vivo. Altogether, SH3BP2 regulates KIT and PDGFRA expression and cell viability, indicating a role as a potential target in imatinib-sensitive and imatinib-resistant GISTs.

Gastrointestinal stromal tumors: A multidisciplinary challenge

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors located in the alimentary tract. Its usual manifestation is gastrointestinal bleeding. However, small asymptomatic lesions are frequently detected as incidental finding. Characteristically, most GISTs (> 95%) are positive for the KIT protein (CD117) by IHC staining and approximately 80%-90% of GISTs carry a mutation in the c-KIT or PDGFRA genes. Mutational analysis should be performed when planning adjuvant and neoadjuvant therapy, due to its possible resistance to conventional treatment. The arise of tyrosine kinase inhibitor has supposed a revolution in GISTs treatment being useful as adjuvant, neoadjuvant or recurrence disease treatment. That is why a multidisciplinary approach to this disease is required. The correct characterization of the tumor at diagnosis (the diagnosis of recurrences and the evaluation of the response to treatment with tyrosine kinase inhibitors) is fundamental for facing these tumors and requires specialized Endoscopist, Radiologists and Nuclear Medicine Physician. Surgery is the only potentially curative treatment for suspected resectable GIST. In the case of high risk GISTs, surgery plus adjuvant Imatinib-Mesylate for 3 years is the standard treatment. Neoadjuvant imatinib-mesylate should be considered to shrink the tumor in case of locally advanced primary or recurrence disease, unresectable or potentially resectable metastasic tumors, and potentially resectable disease in complex anatomic locations to decrease the related morbidity. In the case of Metastatic GIST under Neoadjuvant treatment, when there are complete response, stable disease or limited disease progression, complete cytoreductive surgery could be a therapeutic option if feasible.

Gastrointestinal Stromal Tumor With Multiple Primary Tyrosine Kinase Mutations-Clinicopathologic and Molecular Characterization

A unique cohort of chemo-naive gastrointestinal stromal tumors (GISTs) with double-primary tyrosine kinase mutations was characterized particularly to determine whether coexistent mutations represent a single mutational event. Up to 2013, 4 UK centers reported 9 GISTs with 2 primary tyrosine kinase mutations. In each of 8 cases validated by next generation sequencing, both mutations were present in the same allele of the same exon (KIT exon 11 or 17, or PDGFRA exon 18). One case showed the second mutation only on some of the mutant alleles. Seven cases showed both mutations in all the reads, but in 2 cases, additional variants were found only in some reads. Clinicopathologic features of the 8 cases were similar to GISTs with single-primary mutations. When GIST genotyping rarely uncovers multiple tyrosine kinase variants in an exon, they occur in the same allele but are likely to represent separate mutational events and lack clinical significance.

Oncogene mutational analysis in Chinese gastrointestinal stromal tumor patients

Background

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors and exhibit a high frequency of oncogenic KIT or PDGFRA mutations. Tyrosine kinase inhibitors (TKIs) have been mainly used in the treatment of GISTs bearing KIT/PDGFRA mutations. However, other mutation profiles have been found to affect the sensitivity to and effectiveness of TKIs in the treatment of GISTs.

Purpose

The aim of the present study was to describe the mutational status of multiple genes in GIST samples and to provide information for finding potential predictive markers of therapeutic targets in Chinese GIST patients.

Patients and methods

MassARRAY spectrometry was used to test 40 Chinese GIST patients for 238 mutations affecting 19 oncogenes.

Results

A total of 14 oncogenes with 43 mutations were detected in 38 samples, with a mutation frequency of 95%. Among these mutation samples, 26 GISTs were found for KIT or PDGFRA mutations, while 12 were KIT/PDGFRA wild-type. Approximately half of the GIST samples harbored multiple mutations. The most frequent mutations were found in KIT (62.5%), CDK4 (17.5%), NRAS (15%) and EGFR (12.5%). Other mutations included PIK3CA and AKT1 (10%), BRAF and ABL1 (7.5%), PDGFRA, ERBB2 and HRAS (5%), and AKT2, FLT3 and KRAS (2.5%). New mutated genes (CDK4, AKT2, FLT3, ERBB2, ABL1 and AKT1), a higher BRAF mutation frequency (7.5%) and new BRAF mutation sites (G464E) were found in Chinese GIST patients.

Conclusion

This study demonstrated useful mutations in a small fraction of Chinese GIST, but targeted therapeutics on these potential predictive markers need to be investigated in depth especially in Oriental populations.

Analysis of KIT gene mutations in patients with melanoma of the head and neck mucosa: a retrospective clinical report

Unlike their cutaneous counterparts, head and neck mucosal malignant melanomas (HNMM) are more aggressive, and their prognostic markers have not been fully elucidated. This study, comprising 28 patients with HNMM, aimed to establish the relationship between different mutations and outcome, define the incidence of KIT mutations in HNMM, and identify the correlation among therapeutic options, histopathological findings, demographic data, and clinical response. Clinical analysis included patient characteristics, staging, primary and palliative treatments, and disease-free survival and overall survival (OS). Progression-free survival and OS were analyzed. Paraffin blocks were selected following histologic analyses, enabling DNA extraction. PCR amplification of exons 9, 11, 13, and 17, with different DNA concentrations, was performed. Patients were predominantly females (57%) and aged 27–85 years. All patients underwent surgery; 17 received adjuvant radiotherapy, and recurrences occurred in 82% patients. Oncologic mutations in KIT were found in 7 of 7 tumors, 3 in exon 9, 3 in exon 11, and 1 in exon 13. Predictive factors for recurrence were mitotic rate, vascular invasion, and perineural spread. There were no significant differences in DFS and OS according to KIT mutation. Our study results suggest that some patients might benefit from appropriate targeted therapy with kinase inhibitors.

Management of hemorrhage in gastrointestinal stromal tumors: a review

Gastrointestinal stromal tumors (GISTs) are relatively common mesenchymal tumors. They originate from the wall of hollow viscera and may be found in any part of the digestive tract. The prognosis of patients with stromal tumors depends on various risk factors, including size, location, presence of mitotic figures, and tumor rupture. Emergency surgery is often required for stromal tumors with hemorrhage. The current literature suggests that stromal tumor hemorrhage indicates poor prognosis. Although the optimal treatment options for hemorrhagic GISTs are based on surgical experience, there remains controversy with regard to optimum postoperative management as well as the classification of malignant potential. This article reviews the biological characteristics, diagnostic features, prognostic factors, treatment, and postoperative management of GISTs with hemorrhage.

Prognostic significance of CD117 expression and TP53 missense mutations in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is extremely aggressive and associated with poor prognosis. There are no known predictive or prognostic markers for TNBC. Inhibition of tumor protein P53 (TP53) has been demonstrated to increase the levels of cluster of differentiation 117 (CD117) in human colorectal cancer cells. However, the function of TP53 in the regulation of CD117 in TNBC has, to the best of our knowledge, not been reported. In the present study, the association between the expression of CD117 protein and TP53 mutations was investigated, and their prognostic value in patients with TNBC was assessed. A total of 58 TNBC and 48 non-TNBC breast cancer tissue samples were assessed for the expression of CD117, p53 and TP53 mutations. The marker of proliferation Ki-67 (MKI67) proliferation index and vascular invasion index (obtained by measuring D2-40 and CD34) was investigated via immunohistochemistry, and mutations in exons 4–8 of TP53 were measured using direct sequencing. Associations between CD117 and p53 levels or TP53 mutations and clinical parameters were statistically evaluated. The rates of CD117 or MKI67 positivity, CD117⁺/TP53 missense mutation⁺, TP53 missense mutations or recurrence were significantly higher in patients with TNBC than in patients with non-TNBC. In TNBC tissues, the presence of CD117 was associated with TP53 missense mutations (P=0.031), vascular invasion, recurrence and MKI67. CD117⁺/TP53 missense mutation⁺ also associated with vascular invasion, recurrence and MKI67. Under univariate analysis, MKI67, vascular invasion, CD117, CD117⁺/TP53 missense mutation⁺ and TP53 missense mutations were associated with the overall survival of patients with TNBC. Multivariate analysis revealed that vascular invasion and CD117⁺/TP53 missense mutation⁺ in primary tumors were independent prognostic factors in patients with TNBC. In conclusion, CD117⁺/TP53 missense mutation⁺ was associated with MKI67, vascular invasion and tumor recurrence in TNBC. The presence of CD117 and TP53 missense mutations together in the primary tumors was an independent prognostic factor for survival of patients with TNBC.

Gastrointestinal Stromal Tumors: The GIST of Precision Medicine

The discovery of activated KIT mutations in gastrointestinal (GI) stromal tumors (GISTs) in 1998 triggered a sea change in our understanding of these tumors and has ushered in a new paradigm for the use of molecular genetic diagnostics to guide targeted therapies. KIT and PDGFRA mutations account for 85-90% of GISTs; subsequent genetic studies have led to the identification of mutation/epimutation of additional genes, including the succinate dehydrogenase (SDH) subunit A, B, C, and D genes. This review focuses on integrating findings from clinicopathologic, genetic, and epigenetic studies, which classify GISTs into two distinct clusters: an SDH-competent group and an SDH-deficient group. This development is important since it revolutionizes our current management of affected patients and their relatives, fundamentally, based on the GIST genotype.

Gastrointestinal stromal tumor of unusual phenotype after imatinib treatment: A case report and diagnostic utility of ETV1 mRNA in situ hybridization

RATIONALE

Gastrointestinal stromal tumor (GIST) is the most common tumor of mesenchymal origin in gastrointestinal tract. Immunohistochemical (IHC) staining combined with a typical morphology is used for the diagnosis of GIST. Typically, IHC staining for v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene (KIT) and discovered on GIST-1(DOG1) is positive in almost all GISTs. However, imatinib mesylate, a specific inhibitor of KIT tyrosine kinase, frequently involves changes in the morphology and IHC staining of GIST, impeding the diagnosis. Recently, in situ hybridization (ISH) for E26 transformation-specific sequence variant 1 (ETV1) mRNA was introduced as a useful marker to diagnose GIST.

PATIENT CONCERNS

We report 2 cases of gastric GIST, which expressed unusual phenotypes after imatinib therapy.

DIAGNOSES

The first patient was found to have a gastric subepithelial tumor in gastroduodenoscopy done for regular checkup. In biopsy of the tumor, it showed homogenous spindle cells that were positive to standard IHC markers for GIST. The second patient visited our hospital because of a palpable mass in the abdomen. In abdominal computed tomography (CT), a tumor arising from the stomach was found. A needle biopsy was done and the patient was diagnosed of gastric GIST because the biopsy showed spindle cells positive to typical IHC markers for GIST. After imatinib treatment, in both patients, the resected tumors were composed of heterogeneous spindle cells negative to KIT, DOG1, and CD34 IHC staining, which was unusual for GIST. However, ISH for ETV1 mRNA done for both biopsied and resected tumors was positive, even after imatinib treatment. A molecular analysis found a mutation in exon 11 of KIT gene before and after imatinib therapy in both patients, confirming the diagnosis of GIST.

INTERVENTIONS

Both patients took neoadjuvant imatinib treatment, and afterwards, underwent a surgical resection.

OUTCOMES

The patients remain on imatinib treatment and no progression or recurrence has been detected to date.

LESSONS

ISH for ETV1 mRNA is a useful technique in diagnosing GIST when IHC with KIT, DOG1, or CD34 fail to stain positive after imatinib therapy.

Characterization of malignant gastrointestinal stromal tumors-a single center experience

Background

The recurrence rate, related to the unpredictable behavior of gastrointestinal stromal tumors (GISTs), continues to be a major topic of investigation, since no actual risk evaluation scales have proven to be exceedingly effective in predicting prognosis. We therefore focus in this study on investigating the predictive variables of disease recurrence.

Methods

Between September 2004 and January 2011, 34 patients, 18 males and 16 females with a median age of 62 (range, 27-87) years, underwent operations for primary, localized and advanced GISTs. Immunohistochemical profile, KIT and the platelet-derived growth factor receptor-alpha (PDGFR-α) gene mutations, tumor size, tumor site, mitotic index, synchronous tumors, adjuvant therapy, symptoms and gender were considered and analyzed as predictive variables. The receiver operating characteristic (ROC) analysis was used to determine the optimal cut-off value for tumor dimension to predict recurrence.

Results

The median follow-up (FU) was 20 months (range, 6-86 months). A first-line adjuvant therapy was performed in nine patients. Disease relapse occurred in five cases. The tumor size and the mitotic index were the strongest predictive factors (P<0.001). The optimal maximum value for the tumor size was 7 cm [area under the curve (AUC) =0.955].

Conclusions

In light of the most recent evidence, a tumor size of 7 cm should be considered the threshold value for malignancy, and smaller GISTs with low mitotic counts as tumors with a low-grade risk.

Oncogenic Kit signalling on the Golgi is suppressed by blocking secretory trafficking with M-COPA in gastrointestinal stromal tumours

Most gastrointestinal stromal tumours (GISTs) are caused by constitutively active mutations in Kit tyrosine kinase. The drug imatinib, a specific Kit inhibitor, improves the prognosis of metastatic GIST patients, but these patients become resistant to the drug by acquiring secondary mutations in the Kit kinase domain. We recently reported that a Kit mutant causes oncogenic signals only on the Golgi apparatus in GISTs. In this study, we show that in GIST, 2-methylcoprophilinamide (M-COPA, also known as "AMF-26"), an inhibitor of biosynthetic protein trafficking from the endoplasmic reticulum (ER) to the Golgi, suppresses Kit autophosphorylation at Y703/Y721/Y730/Y936, resulting in blockade of oncogenic signalling. Results of our M-COPA treatment assay show that Kit Y703/Y730/Y936 in the ER are dephosphorylated by protein tyrosine phosphatases (PTPs), thus the ER-retained Kit is unable to activate downstream molecules. ER-localized Kit Y721 is not phosphorylated, but not due to PTPs. Importantly, M-COPA can inhibit the activation of the Kit kinase domain mutant, resulting in suppression of imatinib-resistant GIST proliferation. Our study demonstrates that Kit autophosphorylation is spatio-temporally regulated and may offer a new strategy for treating imatinib-resistant GISTs.

Surgical Pathology of Gastrointestinal Stromal Tumors: Practical Implications of Morphologic and Molecular Heterogeneity for Precision Medicine

Gastrointestinal stromal tumor (GIST), the most common mesenchymal neoplasm of the gastrointestinal tract, exhibits diverse histologic and clinical manifestations. With its putative origin in the gastrointestinal pacemaker cell of Cajal, GIST can arise in association with any portion of the tubular gastrointestinal tract. Morphologically, GISTs are classified as spindled or epithelioid, though each of these subtypes encompasses a broad spectrum of microscopic appearances, many of which mimic other histologic entities. Despite this morphologic ambiguity, the diagnosis of GIST is aided in many cases by immunohistochemical detection of KIT (CD117) or DOG1 expression. The natural history of GIST ranges from that of a tumor cured by surgical resection to that of a locally advanced or even widely metastatic, and ultimately fatal, disease. This clinicopathologic heterogeneity is paralleled by an underlying molecular diversity: the majority of GISTs are associated with spontaneous activating mutations in KIT, PDGFRA, or BRAF, while additional subsets are driven by genetic lesions-often inherited-of NF1 or components of the succinate dehydrogenase enzymatic complex. Specific gene mutations correlate with particular anatomic or morphologic characteristics and, in turn, with distinct clinical behaviors. Therefore, prognostication and treatment are increasingly dictated not only by morphologic clues, but also by accompanying molecular genetic features. In this review, we provide a comprehensive description of the heterogenous molecular underpinnings of GIST, including implications for the practicing pathologist with regard to morphologic identification, immunohistochemical diagnosis, and clinical management.

Prognostic role of tumor necrosis in patients undergoing curative resection for gastric gastrointestinal stromal tumor: a multicenter analysis of 740 cases in China

Tumor necrosis is associated with poor clinical outcomes in many malignancies. We aimed to determine whether tumor necrosis was an independent predictor of outcomes in gastric gastrointestinal stromal tumors (GISTs). We retrospectively analyzed data from 740 patients undergoing curative resection for gastric GIST at four centers between 2001 and 2015. Disease‐free survival (DFS) was estimated with the Kaplan–Meier method, and associations with prognosis were assessed with Cox regression models. Tumor necrosis was present in 122 cases (16.5%). The prevalence of tumor necrosis increased with higher risk‐stratification, including 0.7%, 7.4%, 17.3%, and 39.3% for very low‐, low‐, intermediate‐ and high‐risk tumors, respectively (P < 0.001). Tumor necrosis was associated with aggressive tumor biology, such as larger tumor size, higher mitotic index, tumor rupture, and presence of nuclear atypia (all P < 0.05). Multivariate analysis revealed that tumor necrosis was an independent predictor of unfavorable DFS (HR: 2.641; 95% CI: 1.359–5.131; P = 0.004). When stratified by the modified National Institutes of Health (NIH) classification, tumor necrosis still independently predicted DFS in high‐risk patients (P = 0.001) but not in non‐high‐risk patients (P = 0.349). The 5‐year DFS rate in high‐risk patients with and without tumor necrosis was 56.5% and 82.9%, respectively (P = 0.004). Notably, the prognostic significance of tumor necrosis was maintained when the patients were stratified by age, sex, tumor location, tumor size, and mitotic index (All P < 0.05). Tumor necrosis is a useful predictor of outcomes in gastric GIST, especially in high‐risk patients. Based on these results, we recommend that the current NIH classification should be further improved and expanded to include tumor necrosis as a valuable prognostic indicator.

MiRNA profiling of gastrointestinal stromal tumors by next-generation sequencing

Deregulation of miRNAs has been observed virtually in all major types of cancer, whereas the miRNA signature in GIST is not well characterized yet. In this study the first high-throughput miRNA profiling of 15 paired GIST and adjacent normal tissue samples was performed using small RNA-seq approach and differentially expressed miRNAs as well as isomiRNAs were defined. Highly significantly deregulated miRNAs were selected for validation by Taq-Man low-density array in replication group of 40 paired samples. Validated miRNAs were further subjected to enrichment analysis, which revealed significantly enriched KEGG pathways in the main GIST associated pathways. Further, we used an integrated analysis of miRNA-mRNA correlations for KIT and PDGFRA target genes and found a significant correlation between all of the enriched miRNAs and their target gene KIT. Results of the phenotype analysis showed miR-509-3p to be up-regulated in epithelioid and mixed cell types compared to spindle type, whereas miR-215-5p showed negative correlation with risk grade of GIST. These data reveal a detailed miRNA profile of GIST and highlight new candidates that may be important in the development of malignant disease.

Clinical and pathological characteristics of gastrointestinal stromal tumor (GIST) metastatic to bone

Our aim in this study was to describe the clinical, morphological, and molecular profile of gastrointestinal stromal tumor (GIST) metastatic to bone. We analyzed the morphological, phenotypic, and molecular characteristics of seven cases, and in addition reviewed 17 cases from literature. Sequence analysis of KIT and PDGFRA genes was possible for six cases. For the GIST cases with bone metastasis, the most common primaries were small intestine (29%), stomach (25%), and rectum (21%). Sites of bone metastases were vertebrae (11), pelvis (8), femur (8), ribs (6), humerus (5), skull (3), scapula (1), and mandible (1). The size ranged from 1.5 to 13 cm (median, 3.8 cm). Bone metastases without involvement of any other organ were seen in 17% of the cases and were solitary in 14 (58%). Adjacent soft tissue involvement was present in nearly half of the patients. Bone metastasis was either manifest at the time of diagnosis (28%) or occurred after a mean period of 4.7 years (3 months-20 years). Morphologically, neoplastic cells were spindle in 67%, epithelioid in 13%, and mixed epithelioid and spindle in 20%. CD117, DOG1, and CD34 were positive in 88, 86, and 85% of the cases, respectively. KIT Exon 11 mutations were the most frequent gene alteration (78%), followed by KIT Exon 13 mutations. Of 17 of the cases with available follow-up information, 7 (41%) patients developed bone metastasis under imatinib therapy. Five patients (29%) died of disease within a mean of 17 months. Bone metastases from GIST are usually found in patients with advanced disease and typically present as lytic masses with occasional soft tissue involvement. We could not identify any KIT or PDGFRA alterations predisposing to bone metastasis.

Management of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasm of the gastrointestinal tract. The stomach is the most common site of origin. Management of GISTs changed after the introduction of molecularly targeted therapies. Although the only potentially curative treatment of resectable primary GISTs is surgery, recurrence is common. Patients with primary GISTs at intermediate or high risk of recurrence should receive imatinib postoperatively. Imatinib is also first-line therapy for advanced disease. Cytoreductive surgery might be considered in advanced GIST for patients with stable/responding disease or limited focal progression on tyrosine kinase inhibitor therapy. GIST requires multidisciplinary management.

M-COPA suppresses endolysosomal Kit-Akt oncogenic signalling through inhibiting the secretory pathway in neoplastic mast cells

Gain-of-function mutations in Kit receptor tyrosine kinase result in the development of a variety of cancers, such as mast cell tumours, gastrointestinal stromal tumours (GISTs), acute myeloid leukemia, and melanomas. The drug imatinib, a selective inhibitor of Kit, is used for treatment of mutant Kit-positive cancers. However, mutations in the Kit kinase domain, which are frequently found in neoplastic mast cells, confer an imatinib resistance, and cancers expressing the mutants can proliferate in the presence of imatinib. Recently, we showed that in neoplastic mast cells that endogenously express an imatinib-resistant Kit mutant, Kit causes oncogenic activation of the phosphatidylinositol 3-kinase-Akt (PI3K-Akt) pathway and the signal transducer and activator of transcription 5 (STAT5) but only on endolysosomes and on the endoplasmic reticulum (ER), respectively. Here, we show a strategy for inhibition of the Kit-PI3K-Akt pathway in neoplastic mast cells by M-COPA (2-methylcoprophilinamide), an inhibitor of this secretory pathway. In M-COPA-treated cells, Kit localization in the ER is significantly increased, whereas endolysosomal Kit disappears, indicating that M-COPA blocks the biosynthetic transport of Kit from the ER. The drug greatly inhibits oncogenic Akt activation without affecting the association of Kit with PI3K, indicating that ER-localized Kit-PI3K complex is unable to activate Akt. Importantly, M-COPA but not imatinib suppresses neoplastic mast cell proliferation through inhibiting anti-apoptotic Akt activation. Results of our M-COPA treatment assay show that Kit can activate Erk not only on the ER but also on other compartments. Furthermore, Tyr568/570, Tyr703, Tyr721, and Tyr936 in Kit are phosphorylated on the ER, indicating that these five tyrosine residues are all phosphorylated before mutant Kit reaches the plasma membrane (PM). Our study provides evidence that Kit is tyrosine-phosphorylated soon after synthesis on the ER but is unable to activate Akt and also demonstrates that M-COPA is efficacious for growth suppression of neoplastic mast cells.

GEIS guidelines for gastrointestinal sarcomas (GIST)

Gastrointestinal stromal sarcomas (GISTs) are the most common mesenchymal tumours originating in the digestive tract. They have a characteristic morphology, are generally positive for CD117 (c-kit) and are primarily caused by activating mutations in the KIT or PDGFRA genes(1). On rare occasions, they occur in extravisceral locations such as the omentum, mesentery, pelvis and retroperitoneum. GISTs have become a model of multidisciplinary work in oncology: the participation of several specialties (oncologists, pathologists, surgeons, molecular biologists, radiologists…) has forested advances in the understanding of this tumour and the consolidation of a targeted therapy, imatinib, as the first effective molecular treatment in solid tumours. Following its introduction, median survival of patients with advanced or metastatic GIST increased from 18 to more than 60months. Sunitinib and Regorafenib are two targeted agents with worldwide approval for second- and third-line treatment, respectively, in metastatic GIST.

Oncogenic signaling by Kit tyrosine kinase occurs selectively on the Golgi apparatus in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are caused by gain-of-function mutations in the Kit receptor tyrosine kinase. Most primary GIST patients respond to the Kit inhibitor imatinib, but this drug often becomes ineffective because of secondary mutations in the Kit kinase domain. The characteristic intracellular accumulation of imatinib-sensitive and -resistant Kit protein is well documented, but its relationship to oncogenic signaling remains unknown. Here, we show that in cancer tissue from primary GIST patients as well as in cell lines, mutant Kit accumulates on the Golgi apparatus, whereas normal Kit localizes to the plasma membrane (PM). In imatinib-resistant GIST with a secondary Kit mutation, Kit localizes predominantly on the Golgi apparatus. Both imatinib-sensitive and imatinib-resistant Kit (Kit(mut)) become fully auto-phosphorylated only on the Golgi and only if in a complex-glycosylated form. Kit(mut) accumulates on the Golgi during the early secretory pathway, but not after endocytosis. The aberrant kinase activity of Kit(mut) prevents its export from the Golgi to the PM. Furthermore, Kit(mut) on the Golgi signals and activates the phosphatidylinositol 3-kinase–Akt (PI3K–Akt) pathway, signal transducer and activator of transcription 5 (STAT5), and the Mek–Erk pathway. Blocking the biosynthetic transport of Kit(mut) to the Golgi from the endoplasmic reticulum inhibits oncogenic signaling. PM localization of Kit(mut) is not required for its signaling. Activation of Src-family tyrosine kinases on the Golgi is essential for oncogenic Kit signaling. These results suggest that the Golgi apparatus serves as a platform for oncogenic Kit signaling. Our study demonstrates that Kit(mut)’s pathogenicity is related to its mis-localization, and may offer a new strategy for treating imatinib-resistant GISTs.

Clinicopathological and molecular features of a large cohort of gastrointestinal stromal tumors (GISTs) and review of the literature: BRAF mutations in KIT/PDGFRA wild-type GISTs are rare events

In KIT/PDGFRA wild-type gastrointestinal stromal tumors (wt-GISTs), BRAF mutations are regarded as alternative pathogenic events driving tumorigenesis. In our study, we aimed at analyzing a large cohort (n=444) of GISTs for BRAF mutations using molecular and immunohistochemical methods. More than 3000 GIST samples from caucasian patients were available in our GIST and Sarcoma Registry NRW. Of these, we selected 172 wt-GISTs to evaluate the frequency of BRAF mutations. Furthermore, 272 GISTs with a representative KIT and PDGFRA mutational status were selected. BRAF mutational status was evaluated by high-resolution melting analysis, Sanger sequencing, and VE1 immunohistochemistry. A BRAF mutation (p.V600E) was found in 7 cases (3.9%) of the wt-GIST cohort. In 2 cases, multiple synchronous tumors harbored the same somatic BRAF mutation. VE1 immunohistochemical staining had a sensitivity of 81.8% and a specificity of 97.5% to detect BRAF p.V600E mutations. Analyzing our cases and the cases reported in the literature (n=37), the percentage of intermediate and high-risk BRAF-mutated wt-GISTs (17/31; 54.8%) was comparable to that recorded for large GIST cohorts irrespective of the mutational status. BRAF mutations are rare events in wt-GISTs, and VE1 immunohistochemistry appears to be a valuable pre-screening tool for the detection of BRAF p.V600E mutations. BRAF mutations in GISTs do not seem to have a prognostic value per se. However, as BRAF inhibition represents a therapeutic option to control disease, we suggest the assessment of the BRAF mutational status, especially in the setting of advanced GIST disease.

Cancer genomics guide clinical practice in personalized medicine

Targeted therapies have revolutionized the treatment of many cancers. Widely developed over the last decade, this new concept of precision medicine relies on the use of genomic technologies to analyze tumor samples in order to identify actionable targets and biomarkers of resistance. The goal is to optimize treatment by identifying which therapeutic approach is best for each patient, i.e. the treatment that is effective, has minimal adverse effects, and avoids unnecessary intervention and cost. The purpose of this review is to highlight, using a few seminal examples of therapeutic targets, the important contribution of appropriate analysis of key oncogenes or driver genes in making clinical decisions. Cancer genomics is now an indispensable part of clinical management. Furthermore, the development of next generation sequencing (NGS) will enable exploration of more and more genes of interest, leading to new treatment options for personalized medicine.

Gastrointestinal stromal tumors (GISTs): SEAP-SEOM consensus on pathologic and molecular diagnosis

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the digestive tract, with an incidence of 1.1 cases/100,000 inhabitants/year. A group of experts from the Spanish Society of Pathology and the Spanish Society of Oncology met to discuss a brief update on GISTs and agree on aspects relating to the pathological and molecular diagnosis of these tumors. GISTs are generally solitary, well-circumscribed lesions of variable size (<10 mm-35 cm) that may present with intra- or extra-luminal parietal growth or a mixed-type (hourglass) growth pattern. Histologically, they are unencapsulated neoplasms displaying expansive growth and spindle-shaped (70%), epithelioid (20%), or mixed cellularity (10%). Mitotic activity is generally moderate or low and should be evaluated only in areas with high cellularity or higher mitotic frequency. The great majority of GISTs harbour mutually exclusive activating mutations in genes coding for the type III receptor tyrosine kinases KIT and PDGFRA; less commonly, GISTs have also been reported to display mutations elsewhere, including BRAF and NF1 and SDH-complex genes. The method most widely used to detect KIT and PDGFRA mutations is amplification of the exons involved by polymerase chain reaction followed by direct sequencing (Sanger method) of these amplification products. Molecular analyses should always specify the type of analysis performed, the region or mutations evaluated, and the sensitivity of the detection method employed.