Gastrointestinal stromal tumours: origin and molecular oncology

Effect of KIT and PDGFRA Mutations on Survival in Patients With Gastrointestinal Stromal Tumors Treated With Adjuvant Imatinib: An Exploratory Analysis of a Randomized Clinical Trial

Importance

Little is known about whether the duration of adjuvant imatinib influences the prognostic significance of KIT proto-oncogene receptor tyrosine kinase (KIT) and platelet-derived growth factor receptor α (PDGFRA) mutations.

Objective

To investigate the effect of KIT and PDGFRA mutations on recurrence-free survival (RFS) in patients with gastrointestinal stromal tumors (GISTs) treated with surgery and adjuvant imatinib.

Design, Setting, and Participants

This exploratory study is based on the Scandinavian Sarcoma Group VIII/Arbeitsgemeinschaft Internistische Onkologie (SSGXVIII/AIO) multicenter clinical trial. Between February 4, 2004, and September 29, 2008, 400 patients who had undergone surgery for GISTs with a high risk of recurrence were randomized to receive adjuvant imatinib for 1 or 3 years. Of the 397 patients who provided consent, 341 (85.9%) had centrally confirmed, localized GISTs with mutation analysis for KIT and PDGFRA performed centrally using conventional sequencing. During a median follow-up of 88 months (completed December 31, 2013), 142 patients had GIST recurrence. Data of the evaluable population were analyzed February 4, 2004, through December 31, 2013.

Main Outcomes and Measures

The main outcome was RFS. Mutations were grouped by the gene and exon. KIT exon 11 mutations were further grouped as deletion or insertion-deletion mutations, substitution mutations, insertion or duplication mutations, and mutations that involved codons 557 and/or 558.

Results

Of the 341 patients (175 men and 166 women; median age at study entry, 62 years) in the 1-year group and 60 years in the 3-year group), 274 (80.4%) had GISTs with a KIT mutation, 43 (12.6%) had GISTs that harbored a PDGFRA mutation, and 24 (7.0%) had GISTs that were wild type for these genes. PDGFRA mutations and KIT exon 11 insertion or duplication mutations were associated with favorable RFS, whereas KIT exon 9 mutations were associated with unfavorable outcome. Patients with KIT exon 11 deletion or insertion-deletion mutation had better RFS when allocated to the 3-year group compared with the 1-year group (5-year RFS, 71.0% vs 41.3%; P < .001), whereas no significant benefit from the 3-year treatment was found in the other mutational subgroups examined. KIT exon 11 deletion mutations, deletions that involved codons 557 and/or 558, and deletions that led to pTrp557_Lys558del were associated with poor RFS in the 1-year group but not in the 3-year group. Similarly, in the subset with KIT exon 11 deletion mutations, higher-than-the-median mitotic counts were associated with unfavorable RFS in the 1-year group but not in the 3-year group.

Conclusions and Relevance

Patients with KIT exon 11 deletion mutations benefit most from the longer duration of adjuvant imatinib. The duration of adjuvant imatinib modifies the risk of GIST recurrence associated with some KIT mutations, including deletions that affect exon 11 codons 557 and/or 558.

Trial Registration

clinicaltrials.gov Identifier: NCT00116935.

Non-Gaussian diffusion imaging with a fractional order calculus model to predict response of gastrointestinal stromal tumor to second-line sunitinib therapy

PURPOSE

To demonstrate the clinical value of a non-Gaussian diffusion model using fractional order calculus (FROC) for early prediction of the response of gastrointestinal stromal tumor to second-line sunitinib targeted therapy.

METHODS

Fifteen patients underwent sunitinib treatment after imatinib resistance. Diffusion-weighted imaging with multiple b-values was performed before treatment (baseline) and 2 weeks (for early prediction of response) after initiating sunitinib treatment. Conventional MRI images at 12 weeks were used to determine the good and poor responders according to the modified Choi criteria for MRI. Diffusion coefficient D, fractional order parameter β (which correlates to intravoxel tissue heterogeneity), and a microstructural quantity µ were calculated using the FROC model. The FROC parameters and the longest diameter of the lesion, as well as their changes after 2 weeks of treatment, were compared between the good and poor responders. Additionally, the pretreatment FROC parameters were individually combined with the change in D (ΔD) using a logistic regression model to evaluate response to sunitinib treatment with a receiver operating characteristic analysis.

RESULTS

Forty-two good-responding and 32 poor-responding lesions were identified. Significant differences were detected in pretreatment β (0.67 versus 0.74, P = 0.011) and ΔD (45.7% versus 12.4%, P = 0.001) between the two groups. The receiver operating characteristic analysis showed that ΔD had a significantly higher predictive power than the tumor size change (area under the curve: 0.725 versus 0.580; 0.95 confidence interval). When ΔD was combined with pretreatment β, the area under the curve improved to 0.843 with a predictive accuracy of 75.7% (56 of 74).

CONCLUSIONS

The non-Gaussian FROC diffusion model showed clinical value in early prediction of gastrointestinal stromal tumor response to second-line sunitinib targeted therapy. The pretreatment FROC parameter β can increase the predictive accuracy when combined with the change in diffusion coefficient during treatment. Magn Reson Med 79:1399-1406, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Wnt/β-catenin Signaling Contributes to Tumor Malignancy and Is Targetable in Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor (GIST) is the most common type of sarcoma and usually harbors either a KIT or PDGFRA mutation. However, the molecular basis for tumor malignancy is not well defined. Although the Wnt/β-catenin signaling pathway is important in a variety of cancers, its role in GIST is uncertain. Through analysis of nearly 150 human GIST specimens, we found that some human GISTs expressed β-catenin and contained active, dephosphorylated nuclear β-catenin. Furthermore, advanced human GISTs expressed reduced levels of the Wnt antagonist DKK4. Accordingly, in human GIST T1 cells, Wnt stimulation increased β-catenin-mediated transcriptional activity in a reporter assay as well as transcription of the downstream target genes Axin2 and CCND1 In contrast, DKK4 overexpression in GIST T1 cells reduced Wnt/β-catenin signaling. In addition, we showed that nuclear β-catenin stability was partially regulated by the E3 ligase COP1, as demonstrated with coimmunoprecipitation and COP1 knockdown. Three molecular inhibitors of the Wnt/β-catenin pathway demonstrated antitumor efficacy in various GIST models, both in vitro and in vivo Notably, the tankyrase inhibitor G007-LK alone had substantial activity against tumors of genetically engineered Kit^V558Δ/+ mice, and the effect was increased by the addition of the Kit inhibitor imatinib mesylate. Collectively, our findings demonstrate that Wnt/β-catenin signaling is a novel therapeutic target for selected untreated or imatinib-resistant GISTs. Mol Cancer Ther; 16(9); 1954-66. ©2017 AACR.

Primary Cilia and Coordination of Receptor Tyrosine Kinase (RTK) and Transforming Growth Factor β (TGF-β) Signaling

Since the beginning of the millennium, research in primary cilia has revolutionized our way of understanding how cells integrate and organize diverse signaling pathways during vertebrate development and in tissue homeostasis. Primary cilia are unique sensory organelles that detect changes in their extracellular environment and integrate and transmit signaling information to the cell to regulate various cellular, developmental, and physiological processes. Many different signaling pathways have now been shown to rely on primary cilia to function properly, and mutations that lead to ciliary dysfunction are at the root of a pleiotropic group of diseases and syndromic disorders called ciliopathies. In this review, we present an overview of primary cilia-mediated regulation of receptor tyrosine kinase (RTK) and transforming growth factor β (TGF-β) signaling. Further, we discuss how defects in the coordination of these pathways may be linked to ciliopathies.

Cost-Effectiveness Analysis of Regorafenib for Gastrointestinal Stromal Tumour (GIST) in Germany

BACKGROUND

No study has compared the cost-effectiveness of active treatment options for unresectable or metastatic gastrointestinal stromal tumours in patients who progressed on or are intolerant to prior treatment with imatinib and sunitinib. The aim of this study was to estimate the cost-effectiveness of regorafenib compared to imatinib rechallenge in this setting in Germany.

METHODS

Hazard ratios for progression-free (PFS) and overall survival (OS) with regorafenib versus imatinib rechallenge were estimated by indirect comparison. A state distribution model was used to simulate progression, mortality and treatment costs over a lifetime horizon. Drug acquisition costs and utilities were derived from clinical trial data and published literature; non-drug costs were not included. The outcomes measured were treatment costs, life-years (LYs) and quality-adjusted life-years (QALYs).

RESULTS

The indirect comparison suggested that median PFS and OS were longer with regorafenib compared to imatinib but results were not statistically significant. Regorafenib versus imatinib rechallenge was estimated to have hazard ratios of 0.58 (95% CI 0.31-1.11) for PFS and 0.77 (95% CI 0.34-1.77) for OS, with substantial uncertainty due to the rarity of the disease and small number of patients within the trials. Regorafenib treatment per patient over a lifetime horizon provided an additional 0.61 LYs and 0.42 QALYs over imatinib rechallenge, with additional direct drug costs of €8,773. The incremental cost-effectiveness ratio was €21,127 per QALY gained. At a cost-effectiveness threshold of €50,000 per QALY, regorafenib had a 67% probability of being cost-effective.

CONCLUSION

Based on the currently available clinical data, this analysis suggests that regorafenib is cost-effective compared with imatinib rechallenge in Germany.

ETV1-Positive Cells Give Rise to BRAFV600E -Mutant Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumor (GIST) is the most common subtype of sarcoma. Despite clinical advances in the treatment of KIT/PDGFRA-mutant GIST, similar progress against KIT/PDGFRA wild-type GIST, including mutant BRAF-driven tumors, has been limited by a lack of model systems. ETV1 is a master regulator in the intestinal cells of Cajal (ICC), thought to be the cells of origin of GIST. Here, we present a model in which the ETV1 promoter is used to specifically and inducibly drive Cre recombinase in ICC as a strategy to study GIST pathogenesis. Using a conditional allele for Braf^V600E , a mutation observed in clinical cases of GIST, we observed that Braf^V600E activation was sufficient to drive ICC hyperplasia but not GIST tumorigenesis. In contrast, combining Braf^V600E activation with Trp53 loss was sufficient to drive both ICC hyperplasia and formation of multifocal GIST-like tumors in the mouse gastrointestinal tract with 100% penetrance. This mouse model of sporadic GIST model was amenable to therapeutic intervention, and it recapitulated clinical responses to RAF inhibition seen in human GIST. Our work offers a useful in vivo model of human sporadic forms of BRAF-mutant GIST to help unravel its pathogenesis and therapeutic response to novel experimental agents. Cancer Res; 77(14); 3758-65. ©2017 AACR.

Orai1 mediates tumor-promoting store-operated Ca2+ entry in human gastrointestinal stromal tumors via c-KIT and the extracellular signal-regulated kinase pathway

Gastrointestinal stromal tumors originate from interstitial cells of Cajal, the pacemaker cells of the gut. Ca²⁺ regulates the pacemaker activity of interstitial cells of Cajal. Store-operated Ca²⁺ entry mediates the majority of Ca²⁺ entry in most cancer cells and may be a factor in regulating intracellular Ca²⁺ in interstitial cells of Cajal and gastrointestinal stromal tumors. Therefore, a blockade of this mechanism may affect the progression of gastrointestinal stromal tumors. Orai1 is the pore subunit of store-operated Ca²⁺ channels. Here, we reported that Orai1 was overexpressed in gastrointestinal stromal tumor tissues and was positively correlated with a high-risk grade in gastrointestinal stromal tumor patients. Furthermore, upon Orai1 silencing, the functional store-operated Ca²⁺ entry in gastrointestinal stromal tumor cells was decreased, indicating that the function of store-operated Ca²⁺ entry was mediated by Orai1. Inhibition of Orai1-mediated store-operated Ca²⁺ entry by Orai1 silencing or store-operated Ca²⁺ entry blockers (SKF-96365 and 2-aminoethyl diphenylborate) induced obvious cell proliferation suppression, cell-cycle distribution, and apoptosis stimulation in GIST-T1 cells. Conversely, Orai1 overexpression increased store-operated Ca²⁺ entry and cell proliferation in GIST882 cells. In addition, we found that activation of c-KIT and the extracellular signal-regulated kinase pathway participated in the oncogenic functions of Orai1-mediated store-operated Ca²⁺ entry in gastrointestinal stromal tumor cells. These results revealed that Orai1-mediated store-operated Ca²⁺ entry is critical for gastrointestinal stromal tumor cell proliferation via c-KIT and ERK signaling pathway activation. Orai1-mediated store-operated Ca²⁺ entry plays an oncogenic role and may be a novel prognostic factor and therapeutic target for patients with gastrointestinal stromal tumors.

Using molecular diagnostic testing to personalize the treatment of patients with gastrointestinal stromal tumors

INTRODUCTION

The diagnosis and treatment of gastrointestinal stromal tumor (GIST) has emerged as a paradigm for modern cancer treatment ('precision medicine'), as it highlights the importance of matching molecular defects with specific therapies. Over the past two decades, the molecular classification and diagnostic work up of GIST has been radically transformed, accompanied by the development of molecular therapies for specific subgroups of GIST. This review summarizes the developments in the field of molecular diagnosis of GIST, particularly as they relate to optimizing medical therapy. Areas covered: Based on an extensive literature search of the molecular and clinical aspects of GIST, the authors review the most important developments in this field with an emphasis on the differential diagnosis of GIST including mutation testing, therapeutic implications of each molecular subtype, and emerging technologies relevant to the field. Expert commentary: The use of molecular diagnostics to classify GIST has been shown to be successful in optimizing patient treatment, but these methods remain under-utilized. In order to facilitate efficient and comprehensive molecular testing, the authors have developed a decision tree to aid clinicians.

Genetic progression in gastrointestinal stromal tumors: mechanisms and molecular interventions

Gastrointestinal stromal tumors (GISTs) are the most common sarcomas in humans. Constitutively activating mutations in the KIT or PDGFRA receptor tyrosine kinases are the initiating oncogenic events. Most metastatic GISTs respond dramatically to therapies with KIT/PDGFRA inhibitors. Asymptomatic and mitotically-inactive KIT/PDGFRA-mutant "microGISTs" are found in one third of adults, but most of these small tumors never progress to malignancy, underscoring that a progression of oncogenic mutations is required. Recent studies have identified key genomic abnormalities in GIST progression. Novel insights into the genetic progression of GISTs are shedding new light on therapeutic innovations.

Giant gastric gastrointestinal stromal tumor with severe peritoneal dissemination controlled by imatinib therapy following debulking surgery: a case report

BACKGROUND

At the time of diagnosis, giant gastric gastrointestinal stromal tumors are sometimes associated with severe peritoneal dissemination. Unresectable gastrointestinal stromal tumors are considered a systemic disease; therefore, imatinib therapy is currently the primary treatment option in these cases.

CASE PRESENTATION

A 49-year-old Japanese woman was referred to our hospital with symptoms of anorexia, abdominal discomfort, and a palpable abdominal mass. Contrast-enhanced computed tomography revealed a huge mass with an irregular wall, approximately 22 cm in size, located between the posterior gastric wall and her pancreas. The tumor grew rapidly, and her abdominal symptoms worsened; therefore, a semi-urgent laparotomy was performed. The tumor had arisen from her upper stomach and was removed by wedge resection of her stomach. In addition, widely distributed multiple white nodules were noted, which were resected as far as possible. Immunohistochemical staining of the resected specimen was positive for KIT and CD34. The resected white nodules contained the same cells as the primary tumor. Based on these pathological findings, a final diagnosis of a gastric gastrointestinal stromal tumor with peritoneal dissemination was made. Imatinib was administered at 400 mg per day from 1 month postoperatively. The disease progression of the residual disseminated lesions was favorably controlled, and our patient is now doing well, 12 months after surgery.

CONCLUSIONS

Imatinib therapy following debulking surgery can show dramatic effectiveness in giant gastric gastrointestinal stromal tumors with severe peritoneal dissemination.

Intestinal gastrointestinal stromal tumor in a cat

A 12-year-old, 3.6-kg, spayed female domestic shorthaired cat had a 2-month history of anorexia and weight loss. Abdominal ultrasonography and computed tomography revealed an exophytic mass originating from the jejunum with very poor central and poor peripheral contrast enhancement. On day 14, surgical resection of the jejunum and mass with 5-cm margins and an end-to-end anastomosis were performed. Histopathological examination revealed the mass was a transmural, invasive cancer showing exophytic growth and originating from the small intestinal muscle layer. Immunohistochemical analysis of tumor cells revealed diffuse positivity for KIT protein and negativity for desmin and S-100. The mass was diagnosed as a gastrointestinal stromal tumor (GIST). Ultrasonographic findings indicated the tumor probably metastasized to the liver and omentum, as seen in humans and dogs. The owner rejected further treatment at the last visit on day 192. To our knowledge, this is the first report of intestinal tumor and metastasis in feline GIST and its imaging features.

Genome-Wide Analysis Identifies MEN1 and MAX Mutations and a Neuroendocrine-Like Molecular Heterogeneity in Quadruple WT GIST

Quadruple wild-type (WT) gastrointestinal stromal tumor (GIST) is a genomic subgroup lacking KIT/PDGFRA/RAS pathway mutations, with an intact succinate dehydrogenase (SDH) complex. The aim of this work is to perform a wide comprehensive genomic study on quadruple WT GIST to improve the characterization of these patients. We selected 14 clinical cases of quadruple WT GIST, of which nine cases showed sufficient DNA quality for whole exome sequencing (WES). NF1 alterations were identified directly by WES. Gene expression from whole transcriptome sequencing (WTS) and miRNA profiling were performed using fresh-frozen, quadruple WT GIST tissue specimens and compared with SDH and KIT/PDGFRA-mutant GIST. WES identified an average of 18 somatic mutations per sample. The most relevant somatic oncogenic mutations identified were in TP53, MEN1, MAX, FGF1R, CHD4, and CTDNN2. No somatic alterations in NF1 were identified in the analyzed cohort. A total of 247 mRNA transcripts and 66 miRNAs were differentially expressed specifically in quadruple WT GIST. Overexpression of specific molecular markers (COL22A1 and CALCRL) and genes involved in neural and neuroendocrine lineage (ASCL1, Family B GPCRs) were detected and further supported by predicted miRNA target analysis. Quadruple WT GIST show a specific genetic signature that deviates significantly from that of KIT/PDGFRA-mutant and SDH-mutant GIST. Mutations in MEN1 and MAX genes, a neural-committed phenotype and upregulation of the master neuroendocrine regulator ASCL1, support a genetic similarity with neuroendocrine tumors, with whom they also share the great variability in oncogenic driver genes.Implications: This study provides novel insights into the biology of quadruple WT GIST that potentially resembles neuroendocrine tumors and should promote the development of specific therapeutic approaches. Mol Cancer Res; 15(5); 553-62. ©2017 AACR.

Somatic mutational spectrum analysis in a prospective series of 104 gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors distinguished by driver mutations in proto-oncogenes KIT or PDGFRA in 85-90% of cases. These mutations have been linked to the response to imatinib, a multikinase inhibitor, and have independent prognostic impact. Here, we describe the prospective study of the molecular characteristics of 104 GISTs from French adult patients analyzed routinely through the National Hospital Program of Molecular Cancer Diagnosis. All patients with GISTs diagnosed at the University Hospital of Besançon between August 2005 and October 2014 were prospectively included in the present study. KIT, PDGFRA and KRAS-codons 12 and 13 as well as BRAF codon 600 mutations were analyzed by Sanger sequencing or SNaPshot. KIT and PDGFRA mutations were detected in 71.2 and 19.2% of the cases, respectively. A total of 43 different mutations were detected of which 13 had never been described. As expected, KIT exon 9 and PDGFRA exon 18 mutations were associated with small bowel and gastric localizations respectively. No mutation was found in KRAS and BRAF. Molecular studies are critical to improve the management of GISTs. Our study enhances the current knowledge by describing 13 new mutations in KIT. A common molecular pattern in all KIT exon 11 substitutions is also described for the first time in this study but its significance remains unknown since genetic and environmental risk factors favoring the development of GISTs such as DNA repair defects and exposure to carcinogens are not currently known.

Comparison of Gene Expression Profile Between Tumor Tissue and Adjacent Non-tumor Tissue in Patients with Gastric Gastrointestinal Stromal Tumor (GIST)

Gastrointestinal stromal tumors (GISTs) are defined as spindle cell and/or epithelioid tumors originated from interstitial Cajal cells or precursors in the digestive tract. This study was conducted to identify genes differing in expression between the gastric tumors and the adjacent non-cancerous mucosas in patients with primary gastric GIST. The gene expression profile was determined by using oligonucleotide-based DNA microarrays and further validated by quantitative real-time PCR. The Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis was performed to predict signaling pathways involved in gastric GIST. Our data showed that the expression levels of 957 genes (RAB39B, member RAS oncogene family; VCAN, versican; etc.) were higher and that of 526 genes (CXCL14, chemokine C-X-C motif ligand 14; MTUS1, microtubule-associated tumor suppressor 1; etc.) were lower in the gastric tumor tissues as compared with normal gastric tissues. Results from KEGG pathway analysis revealed that the differentially expressed genes were enriched into 16 signaling transduction pathways, including Hedeghog and Wnt signaling pathways. Our study may provide basis for identification of novel biomarkers associated with primary gastric GIST pathogenesis and for exploration of underlying mechanisms involved in this gastric sarcoma.

Assessing tumor vascularization as a potential biomarker of imatinib resistance in gastrointestinal stromal tumors by dynamic contrast-enhanced magnetic resonance imaging

BACKGROUND

Most metastatic gastrointestinal stromal tumors (GISTs) develop resistance to the first-line imatinib treatment. Recently, increased vessel density and angiogenic markers were reported in GISTs with a poor prognosis, suggesting that angiogenesis is implicated in GIST tumor progression and resistance. The purpose of this study was to investigate the relationship between tumor vasculature and imatinib resistance in different GIST mouse models using a noninvasive magnetic resonance imaging (MRI) functional approach.

METHODS

Immunodeficient mice (n = 8 for each cell line) were grafted with imatinib-sensitive (GIST882 and GIST-T1) and imatinib-resistant (GIST430) human cell lines. Dynamic contrast-enhanced MRI (DCE-MRI) was performed on GIST xenografts to quantify tumor vessel permeability (K ^trans) and vascular volume fraction (v _p). Microvessel density (MVD), permeability (mean dextran density, MDD), and angiogenic markers were evaluated by immunofluorescence and western blot assays.

RESULTS

Dynamic contrast-enhanced magnetic resonance imaging showed significantly increased vessel density (P < 0.0001) and permeability (P = 0.0002) in imatinib-resistant tumors compared to imatinib-sensitive ones. Strong positive correlations were observed between MRI estimates, K ^trans and v _p, and their related ex vivo values, MVD (r = 0.78 for K ^trans and r = 0.82 for v _p) and MDD (r = 0.77 for K ^trans and r = 0.94 for v _p). In addition, higher expression of vascular endothelial growth factor receptors (VEGFR2 and VEFGR3) was seen in GIST430.

CONCLUSIONS

Dynamic contrast-enhanced magnetic resonance imaging highlighted marked differences in tumor vasculature and microenvironment properties between imatinib-resistant and imatinib-sensitive GISTs, as also confirmed by ex vivo assays. These results provide new insights into the role that DCE-MRI could play in GIST characterization and response to GIST treatment. Validation studies are needed to confirm these findings.

AMPD3 is associated with the malignant characteristics of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors of the gastrointestinal tract. It is well known that activating mutations in the receptor tyrosine kinases KIT and platelet-derived growth factor receptor-α have essential roles in the pathogenesis of GISTs. The activation of these receptor protein kinases triggers multiple signaling pathways that promote cell proliferation and survival; however, the exact mechanism by which the activation of these kinases promotes the progression of GISTs remains uncertain. The aim of the present was to search for genes that are associated with the progression of GIST. The present study used reverse transcription-quantitative polymerase chain reaction to demonstrate that adenosine monophosphate deaminase 3 (AMPD3) was highly expressed in GISTs. Furthermore, transfection of GIST-T1 cells with KIT-specific small interfering RNA (siRNA) demonstrated that the expression of AMPD3 was dependent on KIT expression, while the depletion of AMPD3 in human GIST-T1 cells using AMPD3-specific siRNA resulted in the suppression of cell migration and invasion. In addition, AMPD3 depletion sensitized GIST-T1 cells to the tyrosine kinase inhibitor imatinib. The results of the present suggested that the combined inhibition of tyrosine kinases and AMPD3 may be effective for the treatment of GISTs.

Integrated genomic analyses identify frequent gene fusion events and VHL inactivation in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. We sequenced nine exomes and transcriptomes, and two genomes of GISTs for integrated analyses. We detected 306 somatic variants in nine GISTs and recurrent protein-altering mutations in 29 genes. Transcriptome sequencing revealed 328 gene fusions, and the most frequently involved fusion events were associated with IGF2 fused to several partner genes including CCND1, FUS, and LASP1. We additionally identified three recurrent read-through fusion transcripts: POLA2-CDC42EP2, C8orf42-FBXO25, and STX16-NPEPL1. Notably, we found intragenic deletions in one of three exons of the VHL gene and increased mRNAs of VEGF, PDGF-β, and IGF-1/2 in 56% of GISTs, suggesting a mechanistic link between VHL inactivation and overexpression of hypoxia-inducible factor target genes in the absence of hypoxia. We also identified copy number gain and increased mRNA expression of AMACR, CRIM1, SKP2, and CACNA1E. Mapping of copy number and gene expression results to the KEGG pathways revealed activation of the JAK-STAT pathway in small intestinal GISTs and the MAPK pathway in wild-type GISTs. These observations will allow us to determine the genetic basis of GISTs and will facilitate further investigation to develop new therapeutic options.

FGFR1 and NTRK3 actionable alterations in "Wild-Type" gastrointestinal stromal tumors

Background

About 10–15% of adult, and most pediatric, gastrointestinal stromal tumors (GIST) lack mutations in KIT, PDGFRA, SDHx, or RAS pathway components (KRAS, BRAF, NF1). The identification of additional mutated genes in this rare subset of tumors can have important clinical benefit to identify altered biological pathways and select targeted therapies.

Methods

We performed comprehensive genomic profiling (CGP) for coding regions in more than 300 cancer-related genes of 186 GISTs to assess for their somatic alterations.

Results

We identified 24 GIST lacking alterations in the canonical KIT/PDGFRA/RAS pathways, including 12 without SDHx alterations. These 24 patients were mostly adults (96%). The tumors had a 46% rate of nodal metastases. These 24 GIST were more commonly mutated at 7 genes: ARID1B, ATR, FGFR1, LTK, SUFU, PARK2 and ZNF217. Two tumors harbored FGFR1 gene fusions (FGFR1–HOOK3, FGFR1–TACC1) and one harbored an ETV6–NTRK3 fusion that responded to TRK inhibition. In an independent sample set, we identified 5 GIST cases lacking alterations in the KIT/PDGFRA/SDHx/RAS pathways, including two additional cases with FGFR1–TACC1 and ETV6–NTRK3 fusions.

Conclusions

Using patient demographics, tumor characteristics, and CGP, we show that GIST lacking alterations in canonical genes occur in younger patients, frequently metastasize to lymph nodes, and most contain deleterious genomic alterations, including gene fusions involving FGFR1 and NTRK3. If confirmed in larger series, routine testing for these translocations may be indicated for this subset of GIST. Moreover, these findings can be used to guide personalized treatments for patients with GIST.

Trial registration NCT 02576431. Registered October 12, 2015

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1075-6) contains supplementary material, which is available to authorized users.

SETD2 histone modifier loss in aggressive GI stromal tumours

BACKGROUND

GI stromal tumours (GISTs) are clinically heterogenous exhibiting varying degrees of disease aggressiveness in individual patients.

OBJECTIVES

We sought to identify genetic alterations associated with high-risk GIST, explore their molecular consequences, and test their utility as prognostic markers.

DESIGNS

Exome sequencing of 18 GISTs was performed (9 patients with high-risk/metastatic and 5 patients with low/intermediate-risk), corresponding to 11 primary and 7 metastatic tumours. Candidate alterations were validated by prevalence screening in an independent patient cohort (n=120). Functional consequences of SETD2 mutations were investigated in primary tissues and cell lines. Transcriptomic profiles for 8 GISTs (4 SETD2 mutated, 4 SETD2 wild type) and DNA methylation profiles for 22 GISTs (10 SETD2 mutated, 12 SETD2 wild type) were analysed. Statistical associations between molecular, clinicopathological factors, and relapse-free survival were determined.

RESULTS

High-risk GISTs harboured increased numbers of somatic mutations compared with low-risk GISTs (25.2 mutations/high-risk cases vs 6.8 mutations/low-risk cases; two sample t test p=3.1×10^-5). Somatic alterations in the SETD2 histone modifier gene occurred in 3 out of 9 high-risk/metastatic cases but no low/intermediate-risk cases. Prevalence screening identified additional SETD2 mutations in 7 out of 80 high-risk/metastatic cases but no low/intermediate-risk cases (n=29). Combined, the frequency of SETD2 mutations was 11.2% (10/89) and 0% (0/34) in high-risk and low-risk GISTs respectively. SETD2 mutant GISTs exhibited decreased H3K36me3 expression while SETD2 silencing promoted DNA damage in GIST-T1 cells. In gastric GISTs, SETD2 mutations were associated with overexpression of HOXC cluster genes and a DNA methylation signature of hypomethylated heterochromatin. Gastric GISTs with SETD2 mutations, or GISTs with hypomethylated heterochromatin, showed significantly shorter relapse-free survival on univariate analysis (log rank p=4.1×10^-5).

CONCLUSIONS

Our data suggest that SETD2 is a novel GIST tumour suppressor gene associated with disease progression. Assessing SETD2 genetic status and SETD2-associated epigenomic phenotypes may guide risk stratification and provide insights into mechanisms of GIST clinical aggressiveness.

SEOM Clinical Guideline for gastrointestinal sarcomas (GIST) (2016)

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the digestive tract, and this disease has served as a paradigmatic model for successful rational development of targeted therapies. The introduction of tyrosine kinase inhibitors with activity against KIT/PDGFRA in both localized and advanced stages has remarkably improved the survival in a disease formerly deemed resistant to all systemic therapies. The Spanish Society of Medical Oncology (SEOM) guidelines provide a multidisciplinary and updated consensus for the diagnosis and treatment of GIST patients. We strongly encourage that the managing of these patients should be performed within multidisciplinary teams in reference centers.

Surgical resection of recurrent gastrointestinal stromal tumor after interruption of long-term nilotinib therapy

Background

Nilotinib inhibits the tyrosine kinase activities of ABL1/BCR-ABL1, KIT, and platelet-derived growth factor receptors (PDGFRs). The results of a phase III clinical trial indicated that nilotinib could not be recommended for broad use as first-line therapy for gastrointestinal stromal tumor (GIST). However, some clinical studies have reported the effectiveness of nilotinib. We report here the cases of two patients who underwent surgical resections of nilotinib-resistant lesions after long-term nilotinib administration.

Case presentation

Two Japanese female patients, aged 66 and 70 years, experienced peritoneal recurrence of intestinal GIST several years after surgery. Both were registered in the ENESTg1 trial and received nilotinib therapy. Although they continued nilotinib administration with a partial response according to the protocol, nilotinib-resistant lesions, which were diagnosed as focally progressive disease, developed and complete surgical resection was performed. Pathological examination revealed that the tumors were composed of viable KIT-positive spindle cells, and the recurrent tumors were diagnosed as nilotinib-resistant GIST. In gene mutation analysis, a secondary KIT gene mutation was detected in one case. Both patients have survived more than 5 years after the first surgery.

Conclusions

Of patients who were registered in this trial, we have encountered two patients with long-term effects after nilotinib administration. Moreover, secondary mutations in the KIT gene, similar to those involved in resistance to imatinib, might be involved in resistance to nilotinib.

A rare case with synchronous gastric gastrointestinal stromal tumor, pancreatic neuroendocrine tumor, and uterine leiomyoma

Background

Although gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, they comprise less than 1% of all gastrointestinal tumors. Neuroendocrine tumors (NET) of the gastro-enteropancreatic system are also rare, representing about 2% of all gastrointestinal neoplasms. Pancreatic localization of NET is extremely uncommon—these tumors are only 1–5% of all pancreatic cancers.

Case presentation

We describe an unusual case with triple tumor localization—a gastric tumor, a formation in the pancreas, which involves the retroperitoneal space, and a uterine leiomyoma. The exact diagnosis was confirmed with immunohistochemical study after surgical treatment of the patient. Distal pancreatic resection, splenectomy, partial gastrectomy, omentectomy, and hysterectomy were performed. The histological examination proved an epithelioid type of gastric GIST. Immunostaining showed focal positive expression of c-kit and no mitotic figures per 50 HPF. Histology of the pancreatic and retroperitoneal formation proved a well-differentiated NET with origin from the islets of Langerhans. The immunohistochemical study demonstrated co-expression of chromogranin A and synaptophysin.

Conclusions

This is the fourth case published so far of a patient with synchronous pancreatic NET and gastric GIST. The main objective of the study is to present a unique case because we have not found any reports for coexistence of the described three types of neoplasm, as in our patient, and we hope that it will be valuable in the future investigations about the genesis, diagnosis, and treatment of these types of tumors.

Partial response to imatinib treatment in a patient with unresectable gastrointestinal stromal tumor: A case report and mini literature review

The aim of the present study was to evaluate the efficacy and safety of imatinib mesylate in unresectable gastrointestinal stromal tumor (GIST) and to discuss its therapeutic regimen. A patient with unresectable GIST is described, and several key clinical studies are reviewed, including the clinical trials B2222 and S0033, which contain recently reported results of the long-term clinical outcome of imatinib in patients with unresectable or metastatic GIST. The recent results of the two studies demonstrate the long-term efficacy and safety of imatinib for unresectable or metastatic GIST. A positive response to imatinib treatment was observed in the present patient, which is consistent with the data of the B2222 and S0033 trials. However, further long-term, large-scale, multicenter and controlled trials are required to determine the relative efficacy of combining imatinib agents with surgical procedures or administering imatinib alone.

Asian Consensus Guidelines for the Diagnosis and Management of Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors originating in the gastrointestinal tract. With the introduction of molecular-targeted therapy for GISTs which has yielded remarkable outcomes, these tumors have become a model of multidisciplinary oncological treatment. Although Western clinical guidelines are available for GISTs, such as those published by the National Comprehensive Cancer Network (NCCN) and the European Society of Medical Oncology (ESMO), the clinical situations in Asian countries are different from those in Western countries in terms of diagnostic methods, surgical approach, and availability of new targeted agents. Accordingly, we have reviewed current versions of several GIST guidelines published by Asian countries (Japan, Korea, China, and Taiwan) and the NCCN and ESMO and discussed the areas of dissensus. We here present the first version of the Asian GIST consensus guidelines that were prepared through a series of meetings involving multidisciplinary experts in the four countries. These guidelines provide an optimal approach to the diagnosis and management of GIST patients in Asian countries.

An inhibitor of the acetyltransferases CBP/p300 exerts antineoplastic effects on gastrointestinal stromal tumor cells

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasm featured by activated mutations of KIT and PDGFRA. Although overall survival rates have greatly improved by the development of receptor tyrosine kinase inhibitors, most patients ultimately acquire resistance due to secondary mutations of KIT or PDGFRA. Inhibition of the histone acetyltransferases (HATs) CREB‑binding protein (CBP) and p300 results in antineoplastic effects in various cancers. To determine whether CBP/p300 can serve as an antineoplastic target for GISTs, specific short interfering RNA sequences and the selective HAT inhibitor C646 were administered to GIST882 cells. Cell viability, apoptosis and the cell cycle were analysed using the Cell Counting Kit-8, a caspase-3/7 activity assay or Annexin V-fluorescein isothiocyanate/propidium iodide (PI) staining and PI staining. Gene and protein expression levels were measured by quantitative real-time polymerase chain reaction and western blotting, respectively. Transcriptional blockage of CBP, rather than p300, resulted in suppression of cell proliferation. Interestingly, both CBP and p300 depletion enhanced caspase-3/7 activity. A lack of CBP and p300 caused ETS translocation variant 1 (ETV1) downregulation and KIT inhibition in GIST cells. Nevertheless, the absence of CBP, not p300, leads to extracellular signal-regulated kinase 1/2 inactivation and c-Jun NH2-terminal kinase activation, suggesting a more crucial role for CBP than p300 in cell proliferation and survival. Furthermore, proliferation of GIST cells was reduced by administration of C646, a selective HAT inhibitor for CBP/p300. Apoptosis induction and cell cycle arrest were detected after exposure to C646, indicating that its antitumor activities were supported by its antiproliferative and proapoptotic effects. Additionally, C646 treatment attenuated ETV1 protein expression and inactivated KIT-dependent pathways. Taken together, the present study suggests that CBP/p300 may serve as novel antineoplastic targets and that use of the selective HAT inhibitor C646 is a promising antitumor strategy for GISTs.

Gastrointestinal stromal tumors (GISTs) and second malignancies: A novel "sentinel tumor"? A monoinstitutional, STROBE-compliant observational analysis

Several evidences showed that patients with gastrointestinal stromal tumors (GISTs) develop additional malignancies. However, thorough incidence of second tumors remains uncertain as the possibility of a common molecular pathogenesis.A retrospective series of 128 patients with histologically proven GIST treated at our institution was evaluated. Molecular analysis of KIT and PDGFR-α genes was performed in all patients. Following the involvement of KRAS mutation in many tumors' pathogenesis, analysis of KRAS was performed in patients with also second neoplasms.Forty-six out of 128 GIST patients (35.9%) had a second neoplasm. Most second tumors (52%) raised from gastrointestinal tract and 19.6% from genitourinary tract. Benign neoplasms were also included (21.7%). Molecular analysis was available for 29/46 patients with a second tumor: wild-type GISTs (n. 5), exon 11 (n. 16), exon 13 (n. 1), exon 9 (n. 1) KIT mutations, exon 14 PDGFR-α mutation (n. 2) and exon 18 PDGFR-α mutation (n. 4). KIT exon 11 mutations were more frequent between patients who developed a second tumor (P = 0.0003). Mutational analysis of KRAS showed a wild-type sequence in all cases. In metachronous cases, the median time interval between GIST and second tumor was 21.5 months.The high frequency of second tumors suggests that an unknown common molecular mechanism might play a role, but it is not likely that KRAS is involved in this common pathogenesis. The short interval between GIST diagnosis and the onset of second neoplasms asks for a careful follow-up, particularly in the first 3 years after diagnosis.

Application of an individualized operative strategy for wedge resection of gastric gastrointestinal stromal tumors: Effectiveness for tumors in difficult locations

BACKGROUND

There is some concern that wedge resection of gastric gastrointestinal stromal tumors is not feasible in certain anatomic locations, such as the cardia or antrum. We sought to review our experience with treatment of gastric gastrointestinal stromal tumors with a particular focus on nonanatomic wedge resections in these challenging locations.

METHODS

Patients undergoing resection of gastrointestinal stromal tumors from 2000-2014 at the Montreal General Hospital were identified from a prospectively collected database, and outcomes were tabulated. An individualized operative strategy was used to guide resection based on tumor location, size, and characteristics. Disease-free survival and overall survival analyzed using the Kaplan-Meier method. Data are presented as median (range).

RESULTS

We identified 59 patients who underwent operative resection for gastric gastrointestinal stromal tumors. Tumor location was fundus/body/greater curvature in 35 (59%) patients, lesser curvature in 8 (14%) patients, antrum in 8 (14%) patients, and cardia in 8 (14%) patients. Median tumor size was 4.5 cm (1.4-25 cm). The majority of cardia and antral lesions were removed with wedge resections (14/16, 87%). For cardial and antral tumors, on-table gastroscopy was used to guide the operative approach and prevent narrowing of the Gastroesophageal junction or pylorus in all patients undergoing wedge resection. Negative pathologic margins were achieved in all patients. The 5-year disease-free survival was 91% and 5-year overall survival was 95%.

CONCLUSION

When selected appropriately, and under the guidance of on-table gastroscopy, laparoscopic nonanatomic wedge resection can be performed successfully in the majority of cases, even for gastrointestinal stromal tumors near the GEJ or pylorus, with excellent oncologic outcomes.

Clinicopathological features and prognosis of omental gastrointestinal stromal tumor: evaluation of a pooled case series

Clinicopathological features and prognosis of omental GISTs are limited due to the extremely rare incidence. Therefore, the aim of the present study was to investigate the clinicopathological features and prognosis of omental GISTs. Omental GISTs cases were obtained from our center and from case reports and clinical studies extracted from MEDLINE. Clinicopathological features and survivals were analyzed. A total of 99 cases of omental GISTs were enrolled in the present study. Omental GISTs occurred predominantly in greater omentum (78/99, 78.8%). The majority of tumors exceeded 10 cm in diameter (67/98, 68.3%) and were high risk (88/96, 91.7%). Histological type was correlated with tumor location and mutational status. The five year DFS and DSS was 86.3% and 80.6%, respectively. Mitotic index was risk factor for prognosis of omental GISTs. Prognosis of omental GISTs was worse than that of gastric GISTs by Kaplan-Meier analysis. However, multivariate analysis showed that the prognosis was comparable between the two groups. The majority of omental GISTs were large and high risk. Mitotic index was risk factor for prognosis of omental GISTs. The prognosis was comparable between omental and gastric GISTs.

Sustained Mutant KIT Activation in the Golgi Complex Is Mediated by PKC-θ in Gastrointestinal Stromal Tumors

PURPOSE

Tumorigenesis of gastrointestinal stromal tumors (GIST) is driven by gain-of-function mutations in the KIT gene, which result in overexpression of activated mutant KIT proteins (MT-KIT). However, the mechanism of MT-KIT overexpression is poorly understood.

EXPERIMENTAL DESIGN

By protein expression analysis and immunofluorescent microscopic analysis, we determine the stability and localization of MT-KIT in four GIST cell lines with different mutations and HeLa cells transfected with mutant KIT model vectors. We also used 154 human GIST tissues to analyze the relationship between the expression of PKC-θ and MT-KITs, and correlations between PKC-θ overexpression and clinicopathological parameters.

RESULTS

We report that four different MT-KIT proteins are intrinsically less stable than wild-type KIT due to proteasome-mediated degradation and abnormally localized to the endoplasmic reticulum (ER) or the Golgi complex. By screening a MT-KIT-stabilizing factor, we find that PKC-θ is strongly and exclusively expressed in GISTs and interacts with intracellular MT-KIT to promote its stabilization by increased retention in the Golgi complex. In addition, Western blotting analysis using 50 GIST samples shows strong correlation between PKC-θ and MT-KIT expression (correlation coefficient = 0.682, P < 0.000001). Immunohistochemical analysis using 154 GISTs further demonstrates that PKC-θ overexpression significantly correlates with several clinicopathological parameters such as high tumor grade, frequent recurrence/metastasis, and poor patient survival.

CONCLUSIONS

Our findings suggest that sustained MT-KIT overexpression through PKC-θ-mediated stabilization in the Golgi contributes to GIST progression and provides a rationale for anti-PKC-θ therapy in GISTs. Clin Cancer Res; 23(3); 845-56. ©2016 AACR.

Syndromic gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of gastrointestinal tract. They feature heterogeneous triggering mechanisms, implying relevant clinical differences. The vast majority of GISTs are sporadic tumors. Rarely, however, GIST-prone syndromes occur, mostly depending on heritable GIST predisposing molecular defects involving the entire organism. These conditions need to be properly identified in order to plan appropriate diagnostic, prognostic and therapeutic procedures. Clinically, GIST-prone syndromes must be thought of whenever GISTs are multiple and/or associated with accompanying signs peculiar to the background tumorigenic trigger, either in single individuals or in kindreds. Moreover, syndromic GISTs, individually considered, tend to show distinctive features depending on the underlying condition. When applicable, genotyping is usually confirmatory. In GIST-prone conditions, the prognostic features of each GIST, defined according to the criteria routinely applied to sporadic GISTs, combine with the characters proper to the background syndromes, defining peculiar clinical settings which challenge physicians to undertake complex decisions. The latter concern preventive therapy and single tumor therapy, implying possible surgical and molecularly targeted options. In the absence of specific comprehensive guidelines, this review will highlight the traits characteristic of GIST-predisposing syndromes, with particular emphasis on diagnostic, prognostic and therapeutic implications, which can help the clinical management of these rare diseases.

Sarcomas Associated With Genetic Cancer Predisposition Syndromes: A Review

: Sarcomas are rare mesenchymal malignancies that demonstrate great clinical and biological heterogeneity. A variety of sarcomas develop in the context of well-defined heritable cancer predisposition syndromes, associations that are often overlooked, given the rarity and diversity of sarcomas and the equivalent relative infrequency of cancer genetic syndromes. This review describes in detail selected heritable cancer predisposition syndromes that are known to be associated with sarcomas. Beyond the molecular and clinical features that define each syndrome, disparities in clinical presentation, natural history, and treatment of syndrome-associated compared with otherwise histologically identical sporadic sarcomas will be described. The clinical approach to selected sarcoma subsets with a view to identifying possible associations with these syndromes will then be described. Although the treatment of the majority of sarcomas will not differ significantly between sporadic cases and those associated with predisposition syndromes, knowledge of features such as unique anatomic sites of affliction or excess toxicities with particular cytotoxic therapies can facilitate alterations in therapeutic strategies to maximize efficacy and minimize toxicity. In addition, recognition of cancer genetic predisposition syndrome will allow patients and their relatives to undertake appropriate genetic counseling and testing, as well as screening, surveillance, and interventional measures, as needed. Situating sarcomas within the genetic endowment of particular patients-specifically that which confers a higher risk of malignancy-will enable clinicians to better manage the patient as a whole, complementing the great efforts currently routinely undertaken to genomically characterize somatic tumor changes with a view to achieving the dream of personalized medicine.

IMPLICATIONS FOR PRACTICE

Sarcomas are uncommon malignancies that often occur sporadically but can also arise in the setting of a recognized heritable cancer predisposition syndrome. Identification of such associations when present can facilitate refinement and optimization of treatment strategies for the sarcoma so as to minimize toxicity and maximize efficacy. Discerning genetic predisposition can also facilitate institution of genetic counseling, as well as screening or surveillance schema for both the patient and his or her relatives, if required. Vigilance for these syndromes has the potential to significantly enhance the quality and comprehensiveness of sarcoma clinical management.

The impact of additional malignancies in patients diagnosed with gastrointestinal stromal tumors

A higher incidence of additional malignancies has been described in patients diagnosed with gastrointestinal stromal tumors (GIST). This study aimed to identify risk factors for developing additional malignancies in patients diagnosed with GIST and evaluate the impact on survival. Individuals diagnosed with GIST from 2001 to2009 were identified from the SEER database. Logistic regression was used to identify predictors of additional malignancies and Cox-proportional hazards regression used to identify predictors of survival. In the study period, 1705 cases of GIST were identified, with 181 (10.6%) patients developing additional malignancies. Colorectal cancer was the most common cancer developing within 6 months of GIST diagnosis (30%). The median time to diagnosis of a malignancy after 6 months of GIST diagnosis was 21.9 months. Older age (p < 0.0001) and extraoesophagogastric GIST (p = 0.0027) were significant prognostic factors associated with additional malignancies. The overall 5-year survival was 65%, with the presence of additional malignancies within 6 months of GIST diagnosis associated with poor overall survival (54%, HR 1.55 1.05-2.3 95% CI, p = 0.04). Predictive factors of additional malignancies in patients diagnosed with GIST are increasing age and the primary disease site. Developing additional malignancies within 6 months of GIST diagnosis is associated with poorer overall survival. Targeted surveillance may be warranted in patients diagnosed with GIST that are at high risk of developing additional malignancies.

A meta-analysis of prognostic value of KIT mutation status in gastrointestinal stromal tumors

Numerous types of KIT mutations have been reported in gastrointestinal stromal tumors (GISTs); however, controversy still exists regarding their clinicopathological significance. In this study, we reviewed the publicly available literature to assess the data by a meta-analysis to characterize KIT mutations and different types of KIT mutations in prognostic prediction in patients with GISTs. Twenty-eight studies that included 4,449 patients were identified and analyzed. We found that KIT mutation status was closely correlated with size of tumors and different mitosis indexes, but not with tumor location. KIT mutation was also observed to be significantly correlated with tumor recurrence, metastasis, as well as the overall survival of patients. Interestingly, there was higher risk of progression in KIT exon 9-mutated patients than in exon 11-mutated patients. Five-year relapse-free survival (RFS) rate was significantly higher in KIT exon 11-deleted patients than in those with other types of KIT exon 11 mutations. In addition, RFS for 5 years was significantly worse in patients bearing KIT codon 557–558 deletions than in those bearing other KIT exon 11 deletions. Our results strongly support the hypothesis that KIT mutation status is another evaluable factor for prognosis prediction in GISTs.

Targeted therapy of gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs) are mesenchymal neoplasms originating in the gastrointestinal tract, usually in the stomach or the small intestine, and rarely elsewhere in the abdomen. The malignant potential of GISTs is variable ranging from small lesions with a benign behaviour to fatal sarcomas. The majority of the tumours stain positively for the CD-117 (KIT) and discovered on GIST-1 (DOG-1 or anoctamin 1) expression, and they are characterized by the presence of a driver kinase-activating mutation in either KIT or platelet-derived growth factor receptor α. Although surgery is the primary modality of treatment, almost half of the patients have disease recurrence following surgery, which highlights the need for an effective adjuvant therapy. Traditionally, GISTs are considered chemotherapy and radiotherapy resistant. With the advent of targeted therapy (tyrosine kinase inhibitors), there has been a paradigm shift in the management of GISTs in the last decade. We present a comprehensive review of targeted therapy in the management of GISTs.

NKp30 isoforms and NKp30 ligands are predictive biomarkers of response to imatinib mesylate in metastatic GIST patients

Despite effective targeted therapy acting on KIT and PDGFRA tyrosine kinases, gastrointestinal stromal tumors (GIST) escape treatment by acquiring mutations conveying resistance to imatinib mesylate (IM). Following the identification of NKp30-based immunosurveillance of GIST and the off-target effects of IM on NK cell functions, we investigated the predictive value of NKp30 isoforms and NKp30 soluble ligands in blood for the clinical response to IM. The relative expression and the proportions of NKp30 isoforms markedly impacted both event-free and overall survival, in two independent cohorts of metastatic GIST. Phenotypes based on disbalanced NKp30B/NKp30C ratio (ΔBC^low) and low expression levels of NKp30A were identified in one third of patients with dismal prognosis across molecular subtypes. This ΔBC^low blood phenotype was associated with a pro-inflammatory and immunosuppressive tumor microenvironment. In addition, detectable levels of the NKp30 ligand sB7-H6 predicted a worse prognosis in metastatic GIST. Soluble BAG6, an alternate ligand for NKp30 was associated with low NKp30 transcription and had additional predictive value in GIST patients with high NKp30 expression. Such GIST microenvironments could be rescued by therapy based on rIFN-α and anti-TRAIL mAb which reinstated innate immunity.

MicroRNAs and Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor (GIST) is the most commonly diagnosed mesenchymal tumor in the gastrointestinal tract. This tumor type is driven by gain-of-function mutations in receptor tyrosine kinases (such as KIT, PDGFRA, and BRAF) or loss-of-function mutations in succinate dehydrogenase complex subunit genes (SDHx). Molecular studies on GIST have improved our understanding of the biology of the disease and have led to the use of targeted therapy approach, such as imatinib for KIT/PDGFRA-mutated GIST. Recently, microRNAs have emerged as important regulators of KIT expression, cancer cell behavior, and imatinib response in GIST. This chapter aims to provide an overview on current understanding of the biological roles of microRNAs in GIST and possible implications in prognosis and therapeutic response.

The embryonic Brachyury transcription factor is a novel biomarker of GIST aggressiveness and poor survival

BACKGROUND

The T-box transcription factor Brachyury was recently reported to be upregulated and associated with prognosis in solid tumors. Here, we proposed to evaluate the potential use of Brachyury protein expression as a new prognostic biomarker in gastrointestinal stromal tumors (GIST).

METHODS

Brachyury protein expression was analyzed by immunohistochemistry in a cohort of 63 bona fide GIST patients. Brachyury expression profiles were correlated with patients' clinicopathological features and prognostic impact. Additionally, an in silico analysis was performed using the Oncomine database to assess Brachyury alterations at DNA and mRNA levels in GISTs.

RESULTS

We found that Brachyury was overexpressed in the majority (81.0 %) of primary GISTs. We observed Brachyury staining in the nucleus alone in 4.8 % of cases, 23.8 % depicted only cytoplasm staining, and 52.4 % of cases exhibited both nucleus and cytoplasm immunostaining. The presence of Brachyury was associated with aggressive GIST clinicopathological features. Particularly, Brachyury nuclear (with or without cytoplasm) staining was associated with the presence of metastasis, while cytoplasm sublocalization alone was correlated with poor patient survival.

CONCLUSIONS

Herein, we demonstrate that Brachyury is overexpressed in GISTs and is associated with worse outcome, constituting a novel prognostic biomarker and a putative target for GIST treatment.

Synchronous occurrence of gastrointestinal stromal tumor and acute myeloid leukemia: A case report and review of the literature

Gastrointestinal stromal tumors (GISTs) originate from the mesenchymal tissue of the gastrointestinal tract. The pathogenesis of GIST is associated with the mutational activation of the receptor tyrosine kinase cluster of differentiation (CD)117 or platelet-derived growth factor receptor-α. Overall, ~60% of GISTs occur in the stomach. Clinically, GISTs may coexist with various types of cancer, including liver cancer, pancreatic tumors and lymphoma, either synchronously or metachronously. The present study reports the case of a patient with the synchronous occurrence of a CD117-positive GIST and acute myeloid leukemia. A 69-year-old man was hospitalized for heart palpitations and dizziness, and was diagnosed with acute myeloid leukemia (AML) by bone marrow aspiration and flow cytometry analysis. An abdominal computed tomograpy and gastroscopy revealed the presence of GIST. The patient received chemotherapy in combination with imatinib (400 mg/day), and the mass was removed 2 months later. To the best of our knowledge, the present study is the first reported case of the synchronous development of a CD117-positive GIST and AML. Additional studies are required in order to understand the association between GIST and hematological malignancies.

KIT Exon 11 Codons 557-558 Deletion Mutation Promotes Liver Metastasis Through the CXCL12/CXCR4 Axis in Gastrointestinal Stromal Tumors

PURPOSE

KIT mutations, the most prevalent genetic event in gastrointestinal stromal tumors (GIST), are associated with malignant features and poor prognosis. Aggressive GISTs possess a high propensity to spread to the liver. This study aimed to explore the role of KIT mutations in GIST liver metastasis.

EXPERIMENTAL DESIGN

A total of 170 GISTs were used to determine the association between KIT mutations and liver metastasis. Immunohistochemistry was performed to assess the correlation of KIT mutations with CXCR4 and ETV1 expression. Genetic and pharmacologic methods were used to study the regulation of CXCR4 and ETV1 by KIT mutations.

RESULTS

Codons 557 and 558 in KIT exon 11 were deletion hot spots in GISTs. KIT exon 11 deletions involving codons 557-558 were highly associated with liver metastasis. Overexpression of mutant KIT with exon 11 codons 557-558 deletion (KIT Δ557-558) increased GIST cell motility and liver metastasis. Mechanistically, overexpression of KIT Δ557-558 in GIST cells increased ETV1 and CXCR4 expression. CXCR4 knockdown counteracted KIT Δ557-558-mediated cell migration. Moreover, KIT Δ557-558-induced CXCR4 expression could be abolished by silencing ETV1. The chromatin immunoprecipitation assay showed that ETV1 directly bound to the CXCR4 promoter. After ERK inhibitor PD325901 treatment, the upregulation of ETV1 by KIT Δ557-558 was prevented. In addition, KIT exon 11 codons 557-558 deletion enhanced CXCL12-mediated GIST cell migration and invasion.

CONCLUSIONS

KIT exon 11 557-558 deletion upregulates CXCR4 through increased binding of ETV1 to the CXCR4 promoter in GIST cells, which thus promotes liver metastasis. These findings highlighted the potential therapeutic targets for metastatic GISTs. Clin Cancer Res; 22(14); 3477-87. ©2016 AACR.