Comprehensive molecular screening by next generation sequencing reveals a distinctive mutational profile of KIT/PDGFRA genes and novel genomic alterations: results from a 20-year cohort of patients with GIST from north-western Greece

Molecular and clinicopathological features of KIT/PDGFRA wild-type gastrointestinal stromal tumors

Approximately 10% of gastrointestinal stromal tumors (GISTs) harbor reportedly no KIT and PDGFRA mutations (wild-type GISTs). The clinicopathological features and oncologic outcomes of wild-type GISTs based on molecular profiles are unknown. We recruited 35 wild-type GIST patients from the two registry studies of high-risk GISTs between 2012 and 2015 and primary GISTs between 2003 and 2014. Molecular profiling of wild-type GISTs was performed by targeted next-generation sequencing (NGS) using formalin-fixed paraffin-embedded tumor samples. Among 35 wild-type GISTs, targeted NGS analysis detected NF1, SDH, or BRAF mutation: 16 NF1-GISTs with various NF1 mutations, 12 SDH-GISTs (4 with SDHA mutations, 4 with SDHB mutations, and 4 with SDHB-negative staining), and 5 BRAF-GISTs with the V600E mutation. Two GISTs showed no mutations based on our targeted NGS analysis. Additional gene mutations were infrequent in primary wild-type GISTs and found in TP53, CREBBP, CDKN2A, and CHEK2. Most NF1-GISTs were located in the small intestine (N = 12; 75%) and showed spindle cell features (N = 15; 94%) and multiple tumors (N = 6, 38%) with modest proliferation activities. In contrast, SDH-GISTs were predominantly found in the stomach (N = 11; 92%), exhibiting epithelioid cell (N = 6; 50%) and multiple (N = 6, 50%) features. The overall survival of patients with SDH-GISTs appeared to be better than that of BRAF-GISTs (p = 0.0107) or NF1-GISTs (p = 0.0754), respectively. In conclusion, major molecular changes in wild-type GISTs include NF1, SDH, and BRAF. NF1-GISTs involved multifocal spindle cell tumors in the small intestine. SDH-GISTs occurred in young patients and were multifocal in the stomach and clinically indolent.

Unexpected reaction of "wild-type" gastrointestinal stromal tumor to imatinib: case report and literature review

Background

Most of gastrointestinal stromal tumors (GISTs) are driven by mutations in the KIT/PDGFRA genes and can benefit from TKIs treatment. However, a small subset of GIST (10%-15%) are called "wild-type" GISTs due to the lack of these mutations. Theoretically, they would not benefit from TKIs treatment and may even develop resistance. Therefore, this unexpected response may challenge inherent perceptions. Herein, we present a case of giant wild-type GIST exhibiting an unexpected response to imatinib(IM), followed by laparoscopic surgical resection. Subsequently, potential underlying mechanisms are discussed.

Case description

This case describes a 57-year-old man who presented with abdominal pain for two weeks. CT revealed a massive lesion near the splenic hilum along the greater curvature of the stomach, concurrently involving the splenic hilar vessels and surrounding lymph nodes. Ultrasound-guided fine needle aspiration biopsy confirmed it is a mesenchymal spindle cell tumor,GIST. Due to the enormous volume and local invasion, neoadjuvant chemotherapy was initially considered. After 6 months of IM 400 mg/d, CT imaging revealed marked changes in tumor heterogeneity and a significant reduction in volume. Subsequently, laparoscopic surgical resection was performed. Postoperative pathological examination, immunohistochemistry, and genetic testing collectively confirmed it is a wild-type GIST.The patient recovered well and was discharged on the 6th day after surgery, with continued oral IM(400 mg/d) after discharge. No recurrence was observed during follow-up until the publication of this report.

Conclusion

This unexpected response suggests that wild-type GISTs may benefit from TKIs treatment, and the potential mechanisms warrant further investigation. Additionally, true wild-type GIST may not be discerned due to current limitations of Next-Generation Sequencing(NGS). Therefore, for advanced/high-risk GIST, additional genetic analysis can be performed after negative NGS results.

Morphological, immunohistochemical, and genetic analyses of epithelioid gastrointestinal stromal tumors

Epithelioid gastrointestinal stromal tumors (GISTs) are rare and may be confused with other tumors with epithelioid morphology. Therefore, herein, we collected 12 epithelioid GIST samples and summarized their morphological and immunohistochemical characteristics. Through genetic testing, we explored the correlation between morphology and gene mutations. The results showed that eight tumors showed focal or diffuse myxoid stromal changes with less cohesively arranged rhabdoid tumor cells; among these, five showed platelet-derived growth factor receptor alpha gene (PDGFRA) mutations. Signet ring cells with sclerosing stroma and receptor tyrosine kinase type III gene (KIT) mutations were present in two cases, which might be a KIT mutation-associated growth pattern in epithelioid GISTs. Succinate dehydrogenase gene (SDH) mutations were detected in three cases. Simultaneously, PDGFRA mutations were detected in two cases, and the Kirsten rat sarcoma viral oncogene homolog gene (KRAS) mutation was detected in another case. SDH-subunit B (SDHB) expression was partially weak and strongly diffuse in two cases with concurrent PDGFRA and SDHD mutations, respectively. The coexistence of PDGFRA and SDHD mutations may have affected SDHB expression. Altogether, we concluded that PDGFRA mutations may play an important role in co-mutant GIST pathogenesis.

Molecular landscape and clinical significance of exon 11 mutations in KIT gene among patients with gastrointestinal stromal tumor: a retrospective exploratory study

Objective

This aim of this study was to investigate the prognostic significance of KIT exon 11 mutation subtypes in patients with GISTs.

Methods

A total of 233 consecutive patients diagnosed with GISTs at the First Affiliated Hospital of Zhengzhou University from January 2013 to August 2018 were included in this study. The prevalence and mutation landscape of exon 11 in KIT was presented. The clinicopathological characteristics and prognosis among the different mutation subtypes were analyzed. All the statistical analyses were performed by SPSS22.0.

Results

Somatic mutational analysis indicated that point mutations were the most frequently detected mutations followed by deletions & compound mutations and insertion and tandem duplication mutations in the stomach. Point mutations showed a low mitotic count and a high risk of recurrence, and deletions and compound mutations have a high mitotic count while insertions and tandem duplication mutations showed a low mitotic count with an intermediate recurrence risk. Point mutations and deletions frequently occurred in sequence region codons 550-560 of exon 11, while compound mutations, insertion, and tandem duplication were mainly detected in codons 557-559, 572-580, and 577-581, respectively. The multi-variation analysis demonstrated that tumor diameter and high recurrence risk groups had worse prognostic values. However, mutation types were not significant predictors of relapse-free survival (RFS) in GISTs. Survival analysis suggested no significant difference in RFS between the 557/558 deletion and the other deletions.

Conclusion

This study suggested that mutations in exon 11 of the KIT gene were common with intermediate/high recurrence risk in GISTs patients. Tumor diameter ≥5 cm, and deletions mutations might predict a worse prognosis.

Gastrointestinal Stromal Tumours (GISTs) with KRAS Mutation: A Rare but Important Subset of GISTs

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the GI tract, usually found in the stomach, jejunum, and ileum. Typically, they are KIT or PDGFR-mutated, allowing for targetable treatments with tyrosine kinase inhibitors such as imatinib. Here, we present two KRAS-mutated wild-type gastrointestinal tumours (GISTs). Both cases occurred in the small bowel of females. Immunohistochemical studies on both tumours showed KIT and DOG-1 positivity, with SDHB retained. Molecular analysis revealed a KRAS G12D mutation and a KRAS G13D mutation, respectively. Wild-type GISTs are extremely uncommon. They typically occur in the stomach or the small bowel. KRAS is one of the genes implicated in this subset of GIST, with KRAS G12D being the most frequently encountered mutation. GIST KRAS mutations can arise alone or in conjunction with KIT, PDFRA, or BRAF mutations. Identification of these rare molecular subtypes is clinically important due to their resistance to imatinib therapy.

Therapeutic Targets of Monoclonal Antibodies Used in the Treatment of Cancer: Current and Emerging

Cancer is one of the leading global causes of death and disease, and treatment options are constantly evolving. In this sense, the use of monoclonal antibodies (mAbs) in immunotherapy has been considered a fundamental aspect of modern cancer therapy. In order to avoid collateral damage, it is indispensable to identify specific molecular targets or biomarkers of therapy and/or diagnosis (theragnostic) when designing an appropriate immunotherapeutic regimen for any type of cancer. Furthermore, it is important to understand the currently employed mAbs in immunotherapy and their mechanisms of action in combating cancer. To achieve this, a comprehensive understanding of the biology of cancer cell antigens, domains, and functions is necessary, including both those presently utilized and those emerging as potential targets for the design of new mAbs in cancer treatment. This review aims to provide a description of the therapeutic targets utilized in cancer immunotherapy over the past 5 years, as well as emerging targets that hold promise as potential therapeutic options in the application of mAbs for immunotherapy. Additionally, the review explores the mechanisms of actin of the currently employed mAbs in immunotherapy.

Pathologic complete response to neoadjuvant imatinib of a gastric stromal tumor with concomitant mutations in KIT: A case report and literature review

Key clinical message

We report the first case of pathologic complete response (pCR) to neoadjuvant imatinib in a gastric stromal tumor harboring KIT mutations in both exons 11 and 9. The significance of this co-occurrence is unknown and might increase the responsiveness of gastrointestinal stromal tumors (GISTs) to imatinib.

Abstract

pCR of GIST to neoadjuvant imatinib is rare. We report a case of pCR to neoadjuvant imatinib in a gastric stromal tumor that harbored co-occurrence of multiple KIT mutations in exons 11 and 9. This co-occurrence in exons 9 and 11 is the first to be reported in the English literature.

GISTs with NTRK Gene Fusions: A Clinicopathological, Immunophenotypic, and Molecular Study

The most common mutations in gastrointestinal stromal tumors (GISTs) are KIT or PDGFRA mutations. Recently, neurotrophic tyrosine receptor kinase (NTRK) fusions have been reported in WT GISTs, which increased interest in introducing tropomyosin receptor kinase (TRK) inhibitors as treatments for GISTs with NTRK fusions. Hence, we aimed to screen NTRK fusions in WT GISTs; we used fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and immunohistochemistry (IHC) to screen NTRK fusions in 46 WT GISTs and evaluate each method. We further reviewed NTRK fusion-positive GISTs from the literature and performed clinical and pathological analyses; two GISTs with an ETV6-NTRK3 fusion (5%) were identified, while only one (50%) was positive for Pan-TRK expression. On the other hand, among the six GISTs with Pan-TRK-positive expression, only one (17%) harbored NTRK fusion. The literature review revealed the strong consistency between FISH and NGS and the limited value of Pan-TRK IHC in screening NTRK fusions in GISTs. In addition, the clinical and pathological analysis showed that GISTs with NTRK rearrangement occurred less frequently in the stomach, were more frequently larger in size, and the epithelioid type presented with a higher risk of recurrence. The NTRK3 fusion has been more common than the NTRK1 fusion in GISTs to date; our study identified two ETV6-NTRK3 fusions in 46 WT GISTs. Compared with FISH and IHC, NGS is preferred for screening WT GISTs, including NTRK rearrangements. However, since GISTs with NTRK fusions are rare, further studies including more samples and mechanistic investigations should be conducted in the future.

Correlation of treatment outcome in sanger/RT‑qPCR KIT/PDGFRA wild‑type metastatic gastrointestinal stromal tumors with next‑generation sequencing results: A single‑center report

In patients with gastrointestinal stromal tumors (GIST), it has become mandatory to determine the driver mutation in order to predict the response to standard treatment with tyrosine kinase inhibitors (TKI). A total of 10–15% of all GIST lack activating mutations in KIT proto-oncogene, receptor tyrosine kinase (KIT)/platelet-derived growth factor receptor alpha (PDGFRA) and have been classified as KIT/PDGFRA wild-type (WT) GIST. They are characterized by poor response to TKI. From a group of 119 metastatic GIST patients, 17 patients with KIT/PDGFRA/BRAF WT GIST as determined by reverse transcription-quantitative (RT-q) PCR and Sanger sequencing were profiled by a targeted next-generation sequencing (NGS) approach and their treatment outcome was assessed. In the present study, 41.2% of patients as KIT/PDGFRA/BRAF WT GIST examined with RT-qPCR and Sanger sequencing were confirmed to be carriers of pathogenic KIT/PDGFRA mutations by NGS and were responsive to TKI. The percentage of genuinely KIT/PDGFRA WT GIST in the present study thereby dropped from the initial 14.3% detected with the RT-qPCR and Sanger sequencing to 7.6% after NGS. Their outcome was universally poor. The reliability of RT-qPCR and direct Sanger sequencing results in this setting is therefore insufficient and it is recommended that NGS becomes a requirement for treatment decision at least in KIT/PDGFRA/BRAF WT GIST as determined by RT-qPCR and Sanger sequencing.

Efficacy and Safety of Ripretinib in Chinese Patients with Advanced Gastrointestinal Stromal Tumors as a Fourth- or Later-Line Therapy: A Multicenter, Single-Arm, Open-Label Phase II Study

PURPOSE

This is a phase II multicenter, single-arm, open-label study assessing the efficacy, safety, and pharmacokinetics (PK) of ripretinib in Chinese patients with advanced gastrointestinal stromal tumor (GIST) as a fourth- or later-line therapy. It was designed to show consistency with the phase III INVICTUS study.

PATIENTS AND METHODS

Patients with disease progression on (or intolerance to) prior imatinib, sunitinib, and at least one other drug were recruited to receive ripretinib 150 mg once daily continuously in 28-day cycles. The primary endpoint was progression-free survival (PFS) based on independent radiologic review (IRR). Secondary efficacy endpoints included objective response rate (ORR) based on IRR and overall survival. Safety endpoints included the incidence and severity of adverse events (AE).

RESULTS

Between April 2020 and August 2020, 39 patients were enrolled. All were included in the safety analysis while 38 were included in the efficacy analysis. By primary data cut-off (February 26, 2021), the median PFS [90% confidence interval (CI)] was 7.2 (2.9-7.3) months; the lower bound of the 90% CI exceeded 1 month, fulfilling the standard of bridging success. The ORR (95% CI) based on IRR was 18.4% (7.7%-34.3%). Treatment-related treatment-emergent AEs (TRAE) were reported in 37 (94.9%) patients. The majority of TRAEs were of grade 1/2. A total of 6 patients (15.4%) experienced grade 3/4 TRAEs.

CONCLUSIONS

The results demonstrated that ripretinib can clinically improve the outcomes of Chinese patients with advanced GIST as a fourth- or later-line therapy. The efficacy, safety, and PK profiles of ripretinib are consistent with those in the global patient population.

Gastrointestinal Stromal Tumors Mimicking Gynecologic Disease: Clinicopathological Analysis of 20 Cases

Diagnosis of pelvic gastrointestinal stromal tumors (GISTs) can be challenging because of their nonspecific presentation and similarity to gynecological neoplasms. In this series, we describe the clinicopathological features of 20 GIST cases: 18 patients presented with pelvic mass and/or abdominal pain concerning gynecological disease; 2 patients presented with a posterior rectovaginal mass or an anorectal mass. Total abdominal hysterectomy and/or salpingo-oophorectomy (unilateral or bilateral) were performed in 13 cases. Gross and histological examination revealed that the ovary/ovaries were involved in three cases, the uterus in two cases, the vagina in two cases and the broad ligament in one case. Immunohistochemically, all tumors (20/20, 100%) were diffusely immunoreactive for c-KIT. The tumor cells were also diffusely positive for DOG-1 (10/10, 100%) and displayed focal to diffuse positivity for CD34 (11/12, 92%). Desmin was focally and weakly expressed in 1 of the 14 tested tumors (1/14, 7%), whereas 2 of 8 tumors (2/8, 25%) showed focal SMA positivity. At the molecular level, 7 of 8 (87.5%) GISTs with molecular analysis contained c-KIT mutations with the second and third c-KIT mutations detected in some recurrent tumors. In addition to c-KIT mutation, a pathogenic RB1 mutation was detected in two cases. We extensively discussed these cases focusing on their differential diagnosis described by the submitting pathologists during consultation. Our study emphasizes the importance of precision diagnosis of GISTs. Alertness to this entity in unusual locations, in combination with clinical history, morphological features as well as immunophenotype, is crucial in leading to a definitive classification.

New treatment strategies for advanced-stage gastrointestinal stromal tumours

When gastrointestinal stromal tumour (GIST), the most common form of sarcoma, was first recognized as a distinct pathological entity in the 1990s, patients with advanced-stage disease had a very poor prognosis owing to a lack of effective medical therapies. The discovery of KIT mutations as the first and most prevalent drivers of GIST and the subsequent development of the first KIT tyrosine kinase inhibitor (TKI), imatinib, revolutionized the treatment of patients with this disease. We can now identify the driver mutation in 99% of patients with GIST via molecular diagnostic testing, and therapies have been developed to treat many, but not all, molecular subtypes of the disease. At present, seven drugs are approved by the FDA for the treatment of advanced-stage GIST (imatinib, sunitinib, regorafenib, ripretinib, avapritinib, larotrectinib and entrectinib), all of which are TKIs. Although these agents can be very effective for treating certain GIST subtypes, challenges remain and new therapeutic approaches are needed. In this Review, we discuss the molecular subtypes of GIST and the evolution of current treatments, as well as their therapeutic limitations. We also highlight emerging therapeutic approaches that might overcome clinical challenges through novel strategies predicated on the biological features of the distinct GIST molecular subtypes.

An oncogenic splice variant of PDGFRα in adult glioblastoma as a therapeutic target for selective CDK4/6 inhibitors

Understanding human genome alterations is necessary to optimize genome-based cancer therapeutics. However, some newly discovered mutations remain as variants of unknown significance (VUS). Here, the mutation c.1403A > G in exon 10 of the platelet-derived growth factor receptor-alpha (PDGFRA) gene, a VUS found in adult glioblastoma multiforme (GBM), was introduced in human embryonal kidney 293 T (HEK293T) cells using genome editing to investigate its potential oncogenic functions. Genome editing was performed using CRISPR/Cas9; the proliferation, drug sensitivity, and carcinogenic potential of genome-edited cells were investigated. We also investigated the mechanism underlying the observed phenotypes. Three GBM patients carrying the c.1403A > G mutation were studied to validate the in vitro results. The c.1403A > G mutation led to a splice variant (p.K455_N468delinsN) because of the generation of a 3’-acceptor splice site in exon 10. PDGFRA-mutated HEK293T cells exhibited a higher proliferative activity via PDGFRα and the cyclin-dependent kinase (CDK)4/CDK6-cyclin D1 signaling pathway in a ligand-independent manner. They showed higher sensitivity to multi-kinase, receptor tyrosine kinase, and CDK4/CDK6 inhibitors. Of the three GBM patients studied, two harbored the p.K455_N468delinsN splice variant. The splicing mutation c.1403A > G in PDGFRA is oncogenic in nature. Kinase inhibitors targeting PDGFRα and CDK4/CDK6 signaling should be evaluated for treating GBM patients harboring this mutation.

Ripretinib and MEK Inhibitors Synergize to Induce Apoptosis in Preclinical Models of GIST and Systemic Mastocytosis

The majority of gastrointestinal stromal tumors (GIST) harbor constitutively activating mutations in KIT tyrosine kinase. Imatinib, sunitinib, and regorafenib are available as first-, second-, and third-line targeted therapies, respectively, for metastatic or unresectable KIT-driven GIST. Treatment of patients with GIST with KIT kinase inhibitors generally leads to a partial response or stable disease but most patients eventually progress by developing secondary resistance mutations in KIT. Tumor heterogeneity for secondary resistant KIT mutations within the same patient adds further complexity to GIST treatment. Several other mechanisms converge and reactivate the MAPK pathway upon KIT/PDGFRA-targeted inhibition, generating treatment adaptation and impairing cytotoxicity. To address the multiple potential pathways of drug resistance in GIST, the KIT/PDGFRA inhibitor ripretinib was combined with MEK inhibitors in cell lines and mouse models. Ripretinib potently inhibits a broad spectrum of primary and drug-resistant KIT/PDGFRA mutants and is approved by the FDA for the treatment of adult patients with advanced GIST who have received previous treatment with 3 or more kinase inhibitors, including imatinib. Here we show that ripretinib treatment in combination with MEK inhibitors is effective at inducing and enhancing the apoptotic response and preventing growth of resistant colonies in both imatinib-sensitive and -resistant GIST cell lines, even after long-term removal of drugs. The effect was also observed in systemic mastocytosis (SM) cells, wherein the primary drug-resistant KIT D816V is the driver mutation. Our results show that the combination of KIT and MEK inhibition has the potential to induce cytocidal responses in GIST and SM cells.

Clinical and biologic roles of PDGFRA in papillary thyroid cancer: a study based on immunohistochemical and in vitro analyses

BACKGROUND

Platelet-derived growth factor receptor alpha (PDGFRA) plays essential roles in several malignant tumors. Nevertheless, its clinical function in papillary thyroid cancer (PTC) is still unclear. This study aimed to examine the clinicopathologic implication and potential molecular underpinning of PDGFRA in PTC.

MATERIAL AND METHODS

Relative PDGFRA expression levels in eight cases of normal thyroid tissue, 15 cases of benign thyroid disease, and 90 cases of PTC were examined by immunohistochemistry (IHC). The prognostic value of PDGFRA was assessed by data mining of The Cancer Genome Atlas dataset. LV-PDGFRA overexpression and negative control CON220 lentivirus vectors were constructed and transfected into a PTC cell line. The capacity for cell proliferation, status of the cell cycle, efficiency of colony-forming, and migration ability of the PTC cells after PDGFRA were detected by multiple assays including methyl thiazolyl tetrazolium, flow cytometry, colony formation, transwell assay, and wound healing. Furthermore, bioinformatics analyses were conducted to determine the potential biologic mechanisms of PDGFRA.

RESULTS

Results of IHC showed that PDGFRA expression was significantly upregulated in PTC samples and was associated with an advanced pathologic stage. Furthermore, patients with PDGFRA overexpression showed poor survival. Ectopically overexpressed PDGFRA accelerated the migration and invasion of PTC cells. Results of the bioinformatics analyses suggested that PDGFRA was involved in several cell proliferation-related pathways.

CONCLUSION

Collectively, our results indicate that PDGFRA overexpression is associated with the poor survival of patients with PTC and that PDGFRA is a potent oncogene in PTC because it significantly increases PTC cell migration and invasion. Thus, PDGFRA may be a promising novel biomarker and therapeutic target for treating PTC.

Targeted Deep Sequencing Uncovers Cryptic KIT Mutations in KIT/PDGFRA/SDH/RAS-P Wild-Type GIST

Background: Gastrointestinal stromal tumors (GIST) are known to carry oncogenic KIT or PDGFRA mutations, or less commonly SDH or NF1 gene inactivation, with very rare cases harboring mutant BRAF or RAS alleles. Approximately 10% of GISTs are devoid of any of such mutations and are characterized by very limited therapeutic opportunities and poor response to standard treatments.

Methods: Twenty-six sporadic KIT/PDGFRA/SDH/RAS-pathway wild type GIST were profiled for the molecular status of genes frequently altered in GIST by a targeted next generation sequencing (NGS) approach. Molecular findings were validated by alternative amplicon-based targeted sequencing, immunohistochemistry, gene expression profiling and Sanger sequencing.

Results: Three patients harboring NF1 inactivating mutations were identified and excluded from further analysis. Intriguingly, five patients carried cryptic KIT alterations, mainly represented by low-allele-fraction mutations (12–16% allele ratio). These mutations were confirmed by another targeted NGS approaches and supported by CD117 immuno-staining, gene expression profiling, Sanger sequencing, with peak signals at the level of background noise, and by the patients' clinical course assessment.

Conclusion: This study indicates that ~20% patients diagnosed with a KIT/PDGFRA/SDH/RAS-pathway wild-type GIST are bona-fide carriers of pathogenic KIT mutations, thus expected to be eligible for and responsive to the various therapeutic lines of TK-inhibitors in use for KIT/PDGFRA-mutant GIST. The centralization for a second level molecular analysis of GIST samples diagnosed as wild-type for KIT and PDGFRA is once again strongly recommended.

Molecular Profile of Gastrointestinal Stromal Tumors in Sixty-Eight Patients from a Single Swiss Institution

INTRODUCTION

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. It has distinct molecular features and primarily affects the KIT and PDGFRA genes.

OBJECTIVE

We wanted to assess the molecular profile of 68 GIST patients who were sequenced consecutively between 2014 and 2019 at our institute of pathology.

METHODS

Our cohort comprised 60 primary and 8 metastatic GIST patients; 43 and 57% of the cases, respectively, were analyzed by Sanger sequencing or next-generation sequencing (NGS).

RESULTS

Of the 60 primary GIST patients, 47 (78%) showed a KIT mutation; 2 cases showed a double KIT mutation, and 1 of these was a therapy-naive GIST. Nine (15%) patients harbored a PDGFRA mutation, 2 (3%) had a BRAF mutation, 1 (2%) had a PIK3CA mutation, and 1 (2%) did not show any mutation. One BRAF and the PIK3CA mutation have not been described in GIST before. All metastatic GIST harbored exclusively KIT mutations.

CONCLUSION

A retrospective analysis of GIST sequenced at our institute revealed incidences of KIT and PDGFRA mutations comparable to those in other cohorts from Europe. Interestingly, we found 2 previously undescribed mutations in the BRAF and PIK3CA genes as well as 1 treatment-naive case with a double KIT mutation in exon 11.

[Wild-type gastroinestinal stromal tumors]

Gastrointestinal stromal tumors (GIST) are the most common non-epithelial tumors of the gastrointestinal tract. Wild-type GISTs (WT-GIST) consist of a rare heterogeneous group characterized by the lack of activating mutations in the tyrosine kinase receptor (Kit) and/or platelet derived growth factor receptor A (PDGFRA). However, WT-GIST is characterized by other genomic alterations, including dehydrogenase succinate (SDH) deficiency or mutations in the Ras pathway. Recent studies have reported many mutations in others genes that may be incriminated in the development of WT-GISTs. Moreover, WT-GIST is frequently associated with hereditary cancer syndromes such as the Carney Triad and Type 1 Neurofibromatosis (NF1). WT-GIST affects usually young and pediatric patients. Most WT-GIST subtypes are insensitive to imatinib; therefore, their therapeutic management is somewhat different from usual GISTs. This review resumes the molecular and therapeutic features of this rare entity.

Increased ski expression levels are associated with a higher risk and poor prognosis in patients with gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most commonly diagnosed primary mesenchymal tumors of the gastrointestinal tract and 30% of GISTs are associated with a high recurrence risk or metastasis. The current risk classification criteria of the National Comprehensive Cancer Network are based on tumor size, mitotic activity and localization. Investigating additional biomarkers associated with clinical risk may aid in the diagnosis of GIST and improves prediction of patient prognosis. In the present study, the value of using the expression levels of the oncoprotein ski as a prognostic predictor for GISTs was investigated. The results demonstrated that high ski expression levels were correlated with high risk and recurrence rates and indicated poor prognosis regarding median disease-free survival. Overall, the present study suggests that ski expression levels may serve as a predictor for clinical risk and prognosis of patients with GISTs.

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.

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.