Gastrointestinal stromal tumors – Summary of mutational status of the primary/secondary KIT/PDGFRA mutations, BRAF mutations and SDH defects

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.

Clinicopathological and mutational characteristics of primary double mutant gastrointestinal stromal tumor: a single center study with review of the literature

AIMS

Primary double KIT/PDGFRA mutations are very rare in gastrointestinal stromal tumours (GISTs) but have not been comprehensively studied to date. In the present study, we investigated the clinicopathologic and genetic features of eight cases of primary double-mutant GISTs, and we reviewed the literature.

METHODS AND RESULTS

The tumours occurred in six males and two females (age range 57-83 years) and involved the small intestine (n = 4), stomach (n = 2), rectum (n = 1) and retroperitoneum (n = 1). Clinical manifestations were variable, ranging from indolent (no symptoms) to aggressive disease (tumour rupture and haemorrhage). All patients underwent surgical excision, and six of them were treated with imatinib. No one experienced recurrence or other complications during the follow-up time (10 to 61 months). Histologically, all the tumours exhibited mixed cell types, accompanied by variable interstitial changes. KIT mutations were detected in all cases, and the majority of them were present in different exons (n = 5). No PDGFRA exon 12, 14 or 18 mutations were found. All the mutations were validated by next-generation sequencing, and two additional variants with comparatively low allelic fractions were identified in one case. Two of the cases had available allele distribution data, one with an in cis compound mutation and the other with an in trans compound mutation.

CONCLUSION

Primary double-mutant GISTs have distinctive clinicopathologic and mutational features. Studies of more cases are necessary for a better understanding of these tumours.

Exploring the Dynamic Crosstalk between the Immune System and Genetics in Gastrointestinal Stromal Tumors

Gastrointestinal Stromal Tumors (GISTs) represent a paradigmatic model of oncogene addiction. Despite the well-known impact of the mutational status on clinical outcomes, we need to expand our knowledge to other factors that influence behavior heterogeneity in GIST patients. A growing body of studies has revealed that the tumor microenvironment (TME), mostly populated by tumor-associated macrophages (TAMs) and lymphocytes (TILs), and stromal differentiation (SD) have a significant impact on prognosis and response to treatment. Interestingly, even though the current knowledge of the role of immune response in this setting is still limited, recent pre-clinical and clinical data have highlighted the relevance of the TME in GISTs, with possible implications for clinical practice in the near future. Moreover, the expression of immune checkpoints, such as PD-L1, PD-1, and CTLA-4, and their relationship to the clinical phenotype in GIST are emerging as potential prognostic biomarkers. Looking forward, these variables related to the underlying tumoral microenvironment in GIST, though limited to still-ongoing trials, might lead to the potential use of immunotherapy, alone or in combination with targeted therapy, in advanced TKI-refractory GISTs. This review aims to deepen understanding of the potential link between mutational status and the immune microenvironment in GIST.

Histiocytic Sarcoma Secondary to Gastrointestinal Stromal Tumors: A Literature Review

Histiocytic sarcoma (HS) is a rare tumor that may result from the transdifferentiation of preexisting hematolymphoid neoplasms in a subset of patients. There are instances of correlation or concurrence between HS and a number of cancers, particularly B-cell-associated hematopoietic tumors. Only three cases of HS occurring subsequent to or concurrently with gastrointestinal stromal tumors (GIST) have been recorded. Our main objective was to give an overview of demographics, clinical signs and symptoms, histopathological findings, and immunohistochemical and molecular analysis when HS develops secondary to or concurrently with GIST. A search of PubMed, Google Scholar, and ScienceDirect was undertaken using Medical Subject Headings (MeSH) keywords. According to the findings of our review, there were two males (66.6%) and one female (33.3%). The average age of patients at presentation was 59.6 years. On the immunohistochemistry, three patients were positive for cluster of differentiation (CD) 68 (100%), two patients were positive for CD 163 (67%), one patient was positive for leukocyte common antigen (LCA) (33%), and only one patient was positive for CD 4, CD 10, CD 31, CD 45, human leukocyte antigen (HLA)-DR, lysozyme, and vimentin (33%). On molecular investigation, the gastric mass of only one patient (33.33%) contained a KIT mutation on exon 11. Emperipolesis was observed in one patient (33.33%) on histological examination. Our study provides an important overview of the available literature and gives insight into important diagnostic markers of HS when it occurs secondary to or concurrently with GIST.

Integrated Antitumor Activities of Cellular Immunotherapy with CIK Lymphocytes and Interferons against KIT/PDGFRA Wild Type GIST

Gastrointestinal stromal tumors (GISTs) are rare, mesenchymal tumors of the gastrointestinal tract, characterized by either KIT or PDGFRA mutation in about 85% of cases. KIT/PDGFRA wild type gastrointestinal stromal tumors (wtGIST) account for the remaining 15% of GIST and represent an unmet medical need: their prevalence and potential medical vulnerabilities are not completely defined, and effective therapeutic strategies are still lacking. In this study we set a patient-derived preclinical model of wtGIST to investigate their phenotypic features, along with their susceptibility to cellular immunotherapy with cytokine-induced killer lymphocytes (CIK) and interferons (IFN). We generated 11 wtGIST primary cell lines (wtGISTc). The main CIK ligands (MIC A/B; ULBPs), along with PD-L1/2, were expressed by wtGISTc and the expression of HLA-I molecules was preserved. Patient-derived CIK were capable of intense killing in vitro against wtGISTc resistant to both imatinib and sunitinib. We found that CIK produce a high level of granzyme B, IFNα and IFNγ. CIK-conditioned supernatant was responsible for part of the observed tumoricidal effect, along with positive bystander modulatory activities enhancing the expression of PD-L1/2 and HLA-I molecules. IFNα, but not In, had direct antitumor effects on 50% (4/8) of TKI-resistant wtGISTc, positively correlated with the tumor expression of IFN receptors. wtGIST cells that survived IFNα were still sensitive to CIK immunotherapy. Our data support the exploration of CIK immunotherapy in clinical studies for TKI-resistant wtGIST, proposing reevaluation for IFNα within this challenging setting.

The Role of Regorafenib in the Management of Advanced Gastrointestinal Stromal Tumors: A Systematic Review

Regorafenib, a multi-kinase inhibitor, has been widely used to treat patients with gastrointestinal stromal tumors (GIST) who failed the initial treatment with imatinib and sunitinib. This systematic review aims to demonstrate the efficacy and safety of regorafenib for patients with metastatic and/or unresectable GIST. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to perform this systematic review. We searched PubMed, Science Direct, and Cochrane databases to identify relevant articles based on predefined selection criteria. The implication of the search strategy results in 776 records from all databases. We excluded conference abstracts, discussion articles, case reports, case series, systematic reviews, and other observational non-intervention studies from the study, along with the articles published in languages other than English. After the screening and quality assessment, 10 studies were selected for final review - two randomized controlled trials and eight non-randomized prospective and retrospective review articles of intervention. Regorafenib improved the survival rates of patients after the failure of imatinib and sunitinib treatment, with an acceptable safety profile. Close monitoring of the patients may be needed to detect and manage the grade 4 or higher adverse events.

The synergistic therapeutic effect of imatinib and protein kinase CK2 Inhibition correlates with PI3K-AKT activation in gastrointestinal stromal tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Casein kinase 2 (CK2) has been reported to be involved in several cellular processes in multiple cancers. However, the role of CK2 in GIST remains unclear.

AIM

We aimed to investigate the combinatorial treatment of imatinib (IM) and CK2 inhibition on the progression of GISTs.

METHODS

GIST biopsies and adjacent normal tissues were collected from patients. GIST882 and GIST48 cell lines were subjected to investigate the effect of IM and CK2 inhibition in GIST cells. CCK-8 assay, Caspase-3 activity assay, western blotting, and flow cytometry analysis were employed in the present investigation.

RESULTS

Our results showed that CK2 was highly expressed in GIST biopsies, and inhibition of CK2 resulted in decrease in cell viability and increase in apoptosis of GIST cells. Moreover, the combination treatment with CX-4945 (CX) and IM resulted in a more significant decrease in cell viability and increase in cell apoptosis compared with mono-treatment. Mechanistically, the combination treatment influenced the activation of the PI3K/AKT pathway. The activation of the PI3K/AKT pathway reversed the synergistic impacts of the combined treatment on cell viability and apoptosis.

CONCLUSION

Our results demonstrated that inhibition of CK2 combined with IM exhibited a synergistic anti-cancer effect on GIST cells through inactivation of the PI3K/AKT pathway.

Caveolin-1 expression predicts favourable outcome and correlates with PDGFRA mutations in gastrointestinal stromal tumours (GISTs)

AIMS

Novel prognostic markers are warranted for gastrointestinal stromal tumours. Caveolin-1 is a multifunctional protein that proved to be associated with outcome in multiple tumour types. Aim of this study was to investigate Caveolin-1 expression and prognostic efficacy in a series of gastrointestinal stromal tumours.

METHODS

Caveolin-1 expression was assessed by immunohistochemistry in a retrospective series of 66 gastrointestinal stromal tumours representative of the different molecular subtypes. Correlations with clinical, histopathological and molecular features were investigated. Statistical analyses were performed as appropriate.

RESULTS

Thirty-five cases out of 66 (53.0%) expressed Caveolin-1. Presence of Caveolin-1 expression correlated with favourable histopathologic and clinical traits, including a lower mitotic count (p=0.003) and lower relapse rate (p=0.005). Caveolin-1 expression also resulted associated with the presence of PDGFRA mutations (p=0.010). Outcome analyses showed a favourable prognostic significance of Caveolin-1 expression in terms of relapse-free survival (HR=0.14; 95% CI=0.03 to 0.63) and overall survival (HR=0.29; 95% CI=0.11 to 0.74), even after adjusting for the mutational subgroup (relapse-free survival: HR=0.14, 95% CI=0.04 to 0.44; overall survival: HR=0.29, 95% CI=0.11 to 0.51) and imatinib treatment (relapse-free survival: HR=0.14, 95% CI=0.02 to 0.81; overall survival: HR=0.29, 95% CI=0.17 to 0.48).

CONCLUSION

Caveolin-1 represents a novel prognostic marker in gastrointestinal stromal tumours. Further studies are warranted to validate these results and to explore the mechanisms linking Caveolin-1 expression with the PDGFRA oncogenic pathway.

A Rare Case of Histiocytic Sarcoma Secondary to Gastrointestinal Stromal Tumor in the Stomach: Transdifferentiation or Synchronicity?

Histiocytic sarcoma is a rare malignant histiocytic neoplasm composed of cells with morphologic and immunophenotypic features of mature tissue histiocytes. It occurs anywhere in the body and behaves aggressively. However, its etiology is unknown. Here, we report a 68-year-old female who developed histiocytic sarcoma following chemotherapy with imatinib (Gleevec) for gastrointestinal stromal tumor. Possible mechanisms of transdifferentiation from gastrointestinal stromal tumor to histiocytic sarcoma are discussed based on the features of our case and other two similar cases in the literature.

Simultaneous Integrated Boost Intensity-Modulated Radiotherapy for Locally Advanced Drug-Resistant Gastrointestinal Stromal Tumors: A Feasibility Study

Background

As an emerging clinical problem, locally advanced drug-resistant gastrointestinal stromal tumors (LADRGISTs) has relatively few therapeutic schemes. Although radiotherapy is not often considered for GISTs, it could be a valuable contributing modality. The aim of our study is to explore a safe and effective radiation regimen for LADR-GISTs.

Methods

Three patients with LADR-GISTs were treated with simultaneous integrated boost intensity-modulated radiation therapy (SIB-IMRT) plans. In the SIB-IMRT plans, gross target volume (GTV) was divided into GTV-outer, GTV-mid, and GTV-center. And the prescribed dose of planning gross target volume (PGTV) and GTV-outer were both set to 50.4 Gy in 28 fractions. GTV-mid and GTV-center were simultaneously boosted to 60–62 Gy and 62–64 Gy respectively. For comparison purposes, conventional IMRT (Con-IMRT) plans with uniform dose distribution were generated for same optimization objectives without a dose boost to GTV-mid and GTV-center. All plans were optimized to make sure that deliver at least 95% of the prescription dose was delivered to PGTV. Isodose distribution, dose profiles, conformity indexes (CIs), monitor units (MUs), and dose volume histogram (DVH) was evaluated for each individual patient. After the three patients were treated with SIB-IMRT plans, the relative changes in the tumor size and CT values by CT scanning were also tracked.

Results

Compared with Con-IMRT plans, SIB-IMRT plans saw a significant increase from D₉₅ to D₂ of the GTV. With steeper dose gradients in the dose profiles, SIB-IMRT plans had GTV-mid and GTV-center accumulated with higher dose mainly by delivering extra 93 MUs in average. However, there was no significant difference in CIs and organs at risks (OARs) DVH. The relative changes in tumor size and CT values of the three patients in follow up were up to the Choi criteria and the three patients were all assessed as partial response.

Conclusions

The proposed SIB-IMRT may be a potential technique for achieving objective response and prolonging survival of selected GISTs patients.

Gastrointestinal stromal tumour of the rectum and intestinal obstruction: case report

We report the case of a 75-year-old female patient with a big tumour in the lower rectum with intestinal obstruction and lower gastrointestinal bleeding history who underwent a tumour biopsy under laparotomy and end colostomy at another hospital in Peru. She came to our institution for clinical evaluation with a pathology result of a rectal gastrointestinal stromal tumour. An extra elevator abdominoperineal resection was performed with tumour-free margins. The histology confirmed a high-grade (G2) rectal gastrointestinal stromal tumour with a mitotic index of 27/50. DOC-1 (+) and CD117 (+) in immunohistochemistry. Genomic DNA was extracted from the paraffin-fixed tumour sample, and c.1504_1509dupGCCTAT (p.Ala502_Tyr503dup) mutation was detected in exon 9 of the KIT gene. Imatinib 400 mg per day for 3 years was indicated as adjuvant treatment. Currently, she has a disease-free survival of 12 months.

Sarcoma treatment in the era of molecular medicine

Sarcomas are heterogeneous and clinically challenging soft tissue and bone cancers. Although constituting only 1% of all human malignancies, sarcomas represent the second most common type of solid tumors in children and adolescents and comprise an important group of secondary malignancies. More than 100 histological subtypes have been characterized to date, and many more are being discovered due to molecular profiling. Owing to their mostly aggressive biological behavior, relative rarity, and occurrence at virtually every anatomical site, many sarcoma subtypes are in particular difficult-to-treat categories. Current multimodal treatment concepts combine surgery, polychemotherapy (with/without local hyperthermia), irradiation, immunotherapy, and/or targeted therapeutics. Recent scientific advancements have enabled a more precise molecular characterization of sarcoma subtypes and revealed novel therapeutic targets and prognostic/predictive biomarkers. This review aims at providing a comprehensive overview of the latest advances in the molecular biology of sarcomas and their effects on clinical oncology; it is meant for a broad readership ranging from novices to experts in the field of sarcoma.

Research status and progress of drug resistance in gastrointestinal stromal tumors

Targeted drug therapy is another effective treatment for gastrointestinal stromal tumors (GISTs) in addition to surgical treatment, which has significantly improved the prognosis of GIST patients, but drug resistance in some patients is still a tough problem in clinical work. This article reviews the mechanism of primary and secondary drug resistance in first-line treatment of GIST patients and the progress of second-line and third-line treatment, and describes the current problems faced by drug-resistant GIST patients and the direction of future efforts.

BRAF mutations in KIT/PDGFRA positive gastrointestinal stromal tumours (GISTs): Is their frequency underestimated?

BRAF V600E mutations in GISTs are considered to be one of the mutational events in KIT/PDGFRA negative or positive GISTs, respectively. BRAF mutated GISTs usually do not respond to imatinib treatment, even more GISTs with imatinib sensitive KIT mutation. However, they are almost phenotypically and morphologically identical with KIT/PDGFRA positive GISTs. In general, due to the small number of BRAF mutations in GIST and because of the rarity of concomitant BRAF/KIT or BRAF/PDGFRA mutations, their frequency may be depreciated. The aim of this study was BRAF mutation detection in KIT/PDGFRA positive GISTs and their verification by other molecular methods. We applied the sensitive droplet digital PCR on 35 randomly selected KIT/PDGFRA positive GISTs to detect V600E mutations. We have established two criteria for the evaluation of samples: false positive rate (FPR) based on the negative controls; Limit of Detection (LoD) based on the serial dilution of positive control from RKO cell line harboring heterozygous V600E mutation in constant wild-type DNA background. Results from ddPCR were verified by other molecular methods: allele-specific PCR, dideoxysequencing, competitive allele-specific TaqMan PCR (castPCR). FPR was determined as 5 (∼4.4) positive droplets, and LoD was assessed to 3.4293 copies/μL what is the method sensitivity of 0.0162 %. We identified eight KIT/PDGFRA positive patients with concomitant V600E mutation. The five of them were in coexistence with KIT mutation and three with PDGFRA mutation. We also included the liver metastasis, but data from primary tumour were not available. We achieved the very high sensitivity of the ddPCR method for detecting BRAF mutation in GISTs to have importance from the point of view of therapy.