Gastrointestinal Stromal Tumor: Challenges and Opportunities for a New Decade

Monitoring advanced gastrointestinal stromal tumor with circulating tumor DNA

PURPOSE OF REVIEW

This review explores the role of circulating tumor (ct)DNA as a biomarker for clinical decision-making and monitoring purposes in metastatic gastrointestinal stromal tumor (GIST) patients. We discuss key insights from recent clinical trials and anticipate the future perspectives of ctDNA profiling within the clinical landscape of GIST.

RECENT FINDINGS

The identification and molecular characterization of KIT/platelet-derived growth factor receptor alpha (PDGFRA) mutations from ctDNA in metastatic GIST is feasible and reliable. Such identification through ctDNA serves as a predictor of clinical outcomes to tyrosine-kinase inhibitors (TKIs) in metastatic patients. Additionally, conjoined ctDNA analysis from clinical trials reveal the evolving mutational landscapes and increase in intratumoral heterogeneity across treatment lines. Together, this data positions ctDNA determination as a valuable tool for monitoring disease progression and guiding therapy in metastatic patients. These collective efforts culminated in the initiation of a ctDNA-based randomized clinical trial in GIST, marking a significant milestone in integrating ctDNA testing into the clinical care of GIST patients.

SUMMARY

The dynamic field of ctDNA technologies is rapidly evolving and holds significant promise for research. Several trials have successfully validated the clinical utility of ctDNA in metastatic GIST, laying the foundations for its prospective integration into the routine clinical management of GIST patients.

Heterogeneous Profile of ROR1 Protein Expression across Tumor Types

The Wnt receptor ROR1 has generated increased interest as a cancer therapeutic target. Research on several therapeutic approaches involving this receptor is ongoing; however, ROR1 tissue expression remains understudied. We performed an immunohistochemistry analysis of ROR1 protein expression in a large cohort of multiple tumor and histologic types. We analyzed 12 anonymized multi-tumor tissue microarrays (TMAs), including mesothelioma, esophageal and upper gastrointestinal carcinomas, and uterine endometrioid carcinoma, among other tumor types. Additionally, we studied 5 different sarcoma types of TMAs and 6 patient-derived xenografts (PDX) TMAs developed from 19 different anatomic sites and tumor histologic types. A total of 1142 patient cases from different histologic types and 140 PDXs placed in TMAs were evaluated. Pathologists assessed the percentage of tumor cells in each case that were positive for ROR1 and the intensity of staining. For determining the prevalence of staining for each tumor type, a case was considered positive if >1% of its tumor cells showed ROR1 staining. Our immunohistochemistry assays revealed a heterogeneous ROR1 expression profile. A high prevalence of ROR1 expression was found in mesothelioma (84.6%), liposarcoma (36.1%), gastrointestinal stromal tumors (33.3%), and uterine endometrioid carcinoma (28.9%). Other histologic types such as breast, lung, renal cell, hepatocellular, urothelial carcinoma, and colon carcinomas; glioblastoma; cholangiocarcinoma; and leiomyosarcoma showed less ROR1 overall expression, ranging between 0.9 and 13%. No ROR1 expression was seen in mesenchymal chondrosarcoma, rhabdomyosarcoma, or gastric adenocarcinoma cases. Overall, ROR1 expression was relatively infrequent and low in most tumor types investigated; however, ROR1 expression was infrequent but high in selected tumor types, such as gastroesophageal GIST, suggesting that ROR1 prescreening may be preferable for those indications. Further, mesothelioma exhibited frequent and high levels of ROR1 expression, which represents a previously unrecognized therapeutic opportunity. These findings can contribute to the development of ROR1-targeted therapies.

Precision Oncology in Soft Tissue Sarcomas and Gastrointestinal Stromal Tumors

Soft tissue sarcomas (STSs), including gastrointestinal stromal tumors (GISTs), are mesenchymal neoplasms with heterogeneous clinical behavior and represent broad categories comprising multiple distinct biologic entities. Multidisciplinary management of these rare tumors is critical. To date, multiple studies have outlined the importance of biological characterization of mesenchymal tumors and have identified key molecular alterations which drive tumor biology. GIST has represented a flagship for targeted therapy in solid tumors with the advent of imatinib which has revolutionized the way we treat this malignancy. Herein, the authors discuss the importance of biological and molecular diagnostics in managing STS and GIST patients.

FBXW7 regulates the sensitivity of imatinib in gastrointestinal stromal tumors by targeting MCL1

BACKGROUND

Imatinib contributes to improving prognosis of high-risk or unresectable gastrointestinal stromal tumors (GISTs). As therapeutic efficacy is limited by imatinib resistance and toxicity, the exploration of predictive markers of imatinib therapeutic efficacy that enables patients to utilize more effective therapeutic strategies remains urgent.

METHODS

The correlation between FBXW7 and imatinib resistance via FBXW7-MCL1 axis was evaluated in vitro and in vivo experiments. The significance of FBXW7 as a predictor of imatinib treatment efficacy was examined in 140 high-risk patients with GISTs.

RESULTS

The ability of FBXW7 to predict therapeutic efficacy of adjuvant imatinib in high-risk GIST patients was determined through 5-year recurrence-free survival (RFS) rates analysis and multivariate analysis. FBXW7 affects imatinib sensitivity by regulating apoptosis in GIST-T1 cells. FBXW7 targets MCL1 to regulate apoptosis. MCL1 involves in the regulation of imatinib sensitivity through inhibiting apoptosis in GIST-T1 cells. FBXW7 regulates imatinib sensitivity by down-regulating MCL1 to enhance imatinib-induced apoptosis in vitro. FBXW7 regulates imatinib sensitivity of GIST cells by targeting MCL1 to predict efficacy of imatinib treatment in vivo.

CONCLUSIONS

FBXW7 regulates imatinib sensitivity by inhibiting MCL1 to enhance imatinib-induced apoptosis in GIST, and predicts efficacy of imatinib treatment in high-risk GIST patients treated with imatinib.

Postoperative encapsulated hemoperitoneum in a patient with gastric stromal tumor treated by exposed endoscopic full-thickness resection: A case report

BACKGROUND

Gastric stromal tumors, originating from mesenchymal tissues, are one of the most common tumors of the digestive tract. For stromal tumors originating from the muscularis propria, compared with conventional endoscopic submucosal dissection (ESD), endoscopic full-thickness resection (EFTR) can remove deep lesions and digestive tract wall tumors completely. However, this technique has major limitations such as perforation, postoperative bleeding, and post-polypectomy syndrome. Herein, we report a case of postoperative serous surface bleeding which formed an encapsulated hemoperitoneum in a patient with gastric stromal tumor that was treated with exposed EFTR. Feasible treatment options to address this complication are described.

CASE SUMMARY

A 47-year-old male patient had a hemispherical protrusion found during gastric endoscopic ultrasonography, located at the upper gastric curvature adjacent to the stomach fundus, with a smooth surface mucosa and poor mobility. The lesion was 19.3 mm × 16.1 mm in size and originated from the fourth ultrasound layer. Computed tomography (CT) revealed no significant evidence of lymph node enlargement or distant metastasis. Using conventional ESD technology for mucosal pre-resection, exposed EFTR was performed to resect the intact tumor in order to achieve a definitive histopathological diagnosis. Based on its morphology and immunohistochemical expression of CD117 and DOG-1, the lesion was proven to be consistent with a gastric stromal tumor. Six days after exposed EFTR, CT showed a large amount of encapsulated fluid and gas accumulation around the stomach. In addition, gastroscopy suggested intracavitary bleeding and abdominal puncture drainage indicated serosal bleeding. Based on these findings, the patient was diagnosed with serosal bleeding resulting in encapsulated abdominal hemorrhage after exposed EFTR for a gastric stromal tumor. The patient received combined treatments, such as hemostasis under gastroscopy, gastrointestinal decompression, and abdominal drainage. All examinations were normal within six months of follow-up.

CONCLUSION

This patient developed serous surface bleeding in the gastric cavity following exposed EFTR. Serosal bleeding resulting in an encapsulated hemoperitoneum is rare in clinical practice. The combined treatment may replace certain surgical techniques.

KIT mutations and expression: current knowledge and new insights for overcoming IM resistance in GIST

Gastrointestinal stromal tumor (GIST) is the most common sarcoma located in gastrointestinal tract and derived from the interstitial cell of Cajal (ICC) lineage. Both ICC and GIST cells highly rely on KIT signal pathway. Clinically, about 80-90% of treatment-naive GIST patients harbor primary KIT mutations, and special KIT-targeted TKI, imatinib (IM) showing dramatic efficacy but resistance invariably occur, 90% of them was due to the second resistance mutations emerging within the KIT gene. Although there are multiple variants of KIT mutant which did not show complete uniform biologic characteristics, most of them have high KIT expression level. Notably, the high expression level of KIT gene is not correlated to its gene amplification. Recently, accumulating evidences strongly indicated that the gene coding, epigenetic regulation, and pre- or post- protein translation of KIT mutants in GIST were quite different from that of wild type (WT) KIT. In this review, we elucidate the biologic mechanism of KIT variants and update the underlying mechanism of the expression of KIT gene, which are exclusively regulated in GIST, providing a promising yet evidence-based therapeutic landscape and possible target for the conquer of IM resistance. Video Abstract.

Clinical Benefit of Avapritinib in KIT-Mutant Gastrointestinal Stromal Tumors: A Post Hoc Analysis of the Phase I NAVIGATOR and Phase I/II CS3007-001 Studies

PURPOSE

The efficacy of the selective KIT/PDGFRA inhibitor avapritinib (300 mg once daily) was explored in patients with non-PDGFRA-mutant gastrointestinal stromal tumors (GISTs) from the phase I NAVIGATOR and phase I/II CS3007-001 trials.

PATIENTS AND METHODS

Adults with unresectable/metastatic, KIT-only-mutant GISTs and progression following ≥1 tyrosine kinase inhibitors (TKIs) were included in this post hoc analysis. Baseline mutational status was identified in tumor and plasma. Primary endpoints were objective response rate (ORR) and progression-free survival (PFS) by blinded independent radiology review per modified RECIST v1.1 in patients harboring KIT activation-loop mutations (KIT exons 17 or 18) without ATP binding-pocket mutations (KIT exons 13 or 14; ALposABPneg), and other KIT mutations (OTHERS).

RESULTS

Sixty KIT ALposABPneg and 100 KIT OTHERS predominantly heavily pretreated patients (61.3% with ≥3 prior TKIs) were included. ORR was significantly higher in KIT ALposABPneg than KIT OTHERS patients (unadjusted: 26.7% vs. 12.0%; P = 0.0852; adjusted: 31.4% vs. 12.1%; P = 0.0047). Median PFS (mPFS) was significantly longer in KIT ALposABPneg patients compared with KIT OTHERS patients (unadjusted: 9.1 vs. 3.5 months; P = 0.0002; adjusted: 9.1 vs. 3.4 months; P < 0.0001), and longer in second- versus later-line settings (19.3 vs. 5.6-10.6 months). Benefit with avapritinib was observed in patients with KIT exon 9 mutations in the ≥4 line settings (mPFS: 5.6 and 3.7 months for 4 line and >4 line, respectively).

CONCLUSIONS

Avapritinib showed greater antitumor activity in patients with GISTs harboring KIT ALposABPneg mutations versus KIT OTHERS, and may be considered in the former subpopulation. Patients with KIT exon 9 mutations may also benefit in ≥4 line settings.

Ripretinib versus sunitinib in gastrointestinal stromal tumor: ctDNA biomarker analysis of the phase 3 INTRIGUE trial

INTRIGUE was an open-label, phase 3 study in adult patients with advanced gastrointestinal stromal tumor who had disease progression on or intolerance to imatinib and who were randomized to once-daily ripretinib 150 mg or sunitinib 50 mg. In the primary analysis, progression-free survival (PFS) with ripretinib was not superior to sunitinib. In clinical and nonclinical studies, ripretinib and sunitinib have demonstrated differential activity based on the exon location of KIT mutations. Therefore, we hypothesized that mutational analysis using circulating tumor DNA (ctDNA) might provide further insight. In this exploratory analysis (N = 362), baseline peripheral whole blood was analyzed by a 74-gene ctDNA next-generation sequencing-based assay. ctDNA was detected in 280/362 (77%) samples with KIT mutations in 213/362 patients (59%). Imatinib-resistant mutations were found in the KIT ATP-binding pocket (exons 13/14) and activation loop (exons 17/18). Mutational subgroup assessment showed 2 mutually exclusive populations with differential treatment effects. Patients with only KIT exon 11 + 13/14 mutations (ripretinib, n = 21; sunitinib, n = 20) had better PFS with sunitinib versus ripretinib (median, 15.0 versus 4.0 months). Patients with only KIT exon 11 + 17/18 mutations (ripretinib, n = 27; sunitinib, n = 25) had better PFS with ripretinib versus sunitinib (median, 14.2 versus 1.5 months). The results of this exploratory analysis suggest ctDNA sequencing may improve the prediction of the efficacy of single-drug therapies and support further evaluation of ripretinib in patients with KIT exon 11 + 17/18 mutations. ClinicalTrials.gov identifier: NCT03673501.

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.

KIT/PDGFRA Variant Allele Frequency as Prognostic Factor in Gastrointestinal Stromal Tumors (GISTs): Results From a Multi-Institutional Cohort Study

BACKGROUND

The patient selection for optimal adjuvant therapy in gastrointestinal stromal tumors (GISTs) is provided by nomogram based on tumor size, mitotic index, tumor location, and tumor rupture. Although mutational status is not currently used to risk assessment, tumor genotype showed a prognostic influence on natural history and tumor relapse. Innovative measures, such as KIT/PDGFRA-mutant-specific variant allele frequency (VAF) levels detection from next-generation sequencing (NGS), may act as a surrogate of tumor burden and correlate with prognosis and overall survival of patients with GIST, helping the choice for adjuvant treatment.

PATIENTS AND METHODS

This was a multicenter, hospital-based, retrospective/prospective cohort study to investigate the prognostic role of KIT or PDGFRA-VAF of GIST in patients with radically resected localized disease. In the current manuscript, we present the results from the retrospective phase of the study.

RESULTS

Two-hundred (200) patients with GIST between 2015 and 2022 afferent to 6 Italian Oncologic Centers in the EURACAN Network were included in the study. The receiver operating characteristic (ROC) curves analysis was used to classify "low" vs. "high" VAF values, further normalized on neoplastic cellularity (nVAF). When RFS between the low and high nVAF groups were compared, patients with GIST with KIT/PDGFRA nVAF > 50% showed less favorable RFS than patients in the group of nVAF ≤ 50% (2-year RFS, 72.6% vs. 93%, respectively; P = .003). The multivariable Cox regression model confirmed these results. In the homogeneous sub-population of intermediate-risk, patients with KIT-mutated GIST, the presence of nVAF >50% was statistically associated with higher disease recurrence.

CONCLUSION

In our study, we demonstrated that higher nVAF levels were independent predictors of GIST prognosis and survival in localized GIST patients with tumors harboring KIT or PDGFRA mutations. In the cohort of intermediate-risk patients, nVAF could be helpful to improve prognostication and the use of adjuvant imatinib.

Avapritinib-based SAR studies unveil a binding pocket in KIT and PDGFRA

Avapritinib is the only potent and selective inhibitor approved for the treatment of D842V-mutant gastrointestinal stromal tumors (GIST), the most common primary mutation of the platelet-derived growth factor receptor α (PDGFRA). The approval was based on the NAVIGATOR trial, which revealed overall response rates of more than 90%. Despite this transformational activity, patients eventually progress, mostly due to acquired resistance mutations or following discontinuation due to neuro-cognitive side effects. These patients have no therapeutic alternative and face a dismal prognosis. Notable, little is known about this drug's binding mode and its medicinal chemistry development, which is instrumental for the development of the next generation of drugs. Against this background, we solve the crystal structures of avapritinib in complex with wild-type and mutant PDGFRA and stem cell factor receptor (KIT), which provide evidence and understanding of inhibitor binding and lead to the identification of a sub-pocket (Gα-pocket). We utilize this information to design, synthesize and characterize avapritinib derivatives for the determination of key pharmacophoric features to overcome drug resistance and limit potential blood-brain barrier penetration.

Drugs in the GIST Field (Therapeutic Targets and Clinical Trial Staging)

BACKGROUND

Molecular targeted therapies are the most important type of medical treatment for GIST, but the development of GIST drugs and their targets have not been summarized.

METHODS

Drugs in the field of GIST were analyzed and collated through Pharmaprojects, ClinicalTrials. gov and PharmaGO databases.

RESULTS

As of 2021, there are 75 drugs that have appeared in the GIST clinical trials. The six most frequent targets in GIST clinical trials, in descending order of frequency, were KIT, PDGFRA, KDR (VEGFR2), FLT3, FLT1 (VEGFR1), and FLT4/VEGFR3. Only 8 drugs are in preclinical research. There are challenges in the development of new drugs for GIST.

CONCLUSION

This article analyzes and summarizes the general situation of GIST drugs, the target distribution of GIST drugs, and the trends in GIST drug-related clinical trials.

Hallmarks and novel insights for gastrointestinal stromal tumors: A bibliometric analysis

BACKGROUND

Due to the increasing recognition of gastrointestinal stromal tumor (GIST), novel insights have appeared in both preclinical and clinical research and begun to reshape the field. This study aims to map the research landscape through bibliometric analysis and provide a brief overview for the future of the GIST field.

METHODS

We searched the Web of Science Core Collection without publication data restrictions for GISTs and performed a bibliometric analysis with CiteSpace and VOSviewer software.

RESULTS

In sum, 5,911 of 13,776 records were included, and these studies were published in 948 journals and written by 24,965 authors from 4,633 institutions in 100 countries. Referring to published reviews and bibliometric analysis, we classified the future trends in four groups. In epidemiological study, precise incidence and clinicopathological features in different regions and races might become potential hotspots. Novel therapy, such as drugs, modified strategies, radioligand therapy, was persistent hotspots in GIST fields, and ctDNA-guided diagnosis, monitoring, and treatment might meet future clinical needs. The debate over serosa surgery vs. mucosa surgery will remain active for a long time in GIST surgery, and function reserve surgery, biology-based surgery will play an important role in future. Moreover, rare GIST type, like NF-1-associated GIST, Carney triads and SDH mutant GIST, need more studies in pathogenesis and genetic mutation to provide appropriate treatment for this orphan GIST patients.

CONCLUSIONS

Potential hotspots in future GIST trends might involve epidemiology, agents, resection therapy and rare type GIST, moreover, researchers could pay more attention in these four fields.

Effect of Verapamil, a P-glycoprotein-1 and Cytochrome P450 3A4 Inhibitor, on Pharmacokinetics and Metabolic Stability of Ripretinib: A Drug-Drug Interaction Study in Rats

BACKGROUND AND OBJECTIVES

Ripretinib was developed to target a whole range of KIT proto-oncogene mutations and platelet-derived growth factor receptor A (PDGFR-A) kinases found in certain cancers and myeloproliferative neoplasms, particularly gastrointestinal stromal tumours (GISTs). This study investigated the effect of verapamil, a potential inhibitor of P-glycoprotein-1 (P-gp1) and cytochrome P450 3A4 (CYP3A4), on the pharmacokinetics of ripretinib in rats when administered orally together. This study also assessed the metabolic stability and in vitro cellular absorption of ripretinib in the presence of verapamil.

METHODS

A novel sensitive time-saving liquid chromatography tandem mass spectometry (LC-MS/MS) technique for determining ripretinib in rat plasma was developed and validated. A Zorbax SB C18 column was used for the separation and analysis of ripretinib with a mobile phase consisting of 50:50 (%v/v) acetonitrile and 10 mM ammonium formate buffer at a flow rate of 0.4 mL/min. Imatinib was used as an internal standard (IS) in the method. The pharmacokinetic characteristics of ripretinib were evaluated in Wistar rats by successfully administering an oral dosage of 5 mg/kg body weight of ripretinib in the presence of verapamil (10 mg/kg body weight). Subsequently, rat liver microsomes were used to assess the effect of verapamil on ripretinib metabolic stability, and absorption was tested using a Caco-2 cell transwell model.

RESULTS

Ripretinib and IS were identified using multiple reaction monitoring (MRM) modes by mass spectrometry and showed ion transitions of 510.09→94.06 m/z and 494.26→ 394.16 m/z, respectively. The high-performance liquid chromatography (HPLC) method successfully eluted ripretinib and IS at retention times of 0.91 and 0.68 min, respectively, and the method was validated for all parameters and met the criteria for acceptance. Co-administration of verapamil increased the maximum concentration (Cmax) of ripretinib from 437 ± 84 ng/mL to 492 ± 50 ng/mL (12%), and the area under the concentration-time curve from 0 to the last sampling time t (AUC0-t) increased by approximately 40.6%. Verapamil significantly reduced the basolateral-to-apical transfer of ripretinib through Caco-2 cells. Findings also showed that verapamil increased the metabolic stability of ripretinib.

CONCLUSION

The study results indicate that the co-administration of ripretinib with CYP3A4 and/or P-gp1 inhibitors is associated with significant drug-drug interactions that affect the pharmacokinetics of ripretinib. Further research in human subjects is suggested to confirm dosage adjustment and therapeutic drug monitoring of ripretinib when administered along with P-gp1/CYP3A4 inhibitors ensuring patient safety and optimizing the therapeutic benefits of ripretinib.

c-Kit Receptors as a Therapeutic Target in Cancer: Current Insights

c-Kit is a type III receptor tyrosine kinase (RTK) that has an essential role in various biological functions including gametogenesis, melanogenesis, hematopoiesis, cell survival, and apoptosis. c-KIT aberrations, either overexpression or loss-of-function mutations, have been implicated in the pathogenesis and development of many cancers, including gastrointestinal stromal tumors, mastocytosis, acute myeloid leukemia, breast, thyroid, and colorectal cancer, making c-KIT an attractive molecular target for the treatment of cancers. Therefore, a lot of effort has been put into investigating the utility of tyrosine kinase inhibitors for the management of c-KIT mutated tumors. This review of the literature illustrates the role of c-KIT mutations in many cancers, aiming to provide insights into the role of TKIs as a therapeutic option for cancer patients with c-KIT aberrations. In conclusion, c-KIT is implicated in different types of cancer, and it could be a successful molecular target; however, proper detection of the underlying mutation type is required before starting the appropriate personalized therapy.

Ripretinib for the treatment of advanced, imatinib-resistant gastrointestinal stromal tumors

Discovery of constitutive activation of KIT/PDGFRA tyrosine kinases in gastrointestinal stromal tumors (GISTs) leads to the development of the targeted drug imatinib. However, the inevitable development of imatinib resistance remains a major issue. Ripretinib is a novel targeted drug that inhibits the activities of a broad spectrum of drug-resistant KIT/PDGFRA mutants. It was approved in 2020 and is currently recommended by major international guidelines as the fourth-line and beyond therapy for advanced GISTs. Emerging evidence shows that ripretinib is superior to sunitinib as a second-line treatment for KIT exon 11-mutated GISTs due to its activity against highly heterogeneous frequently occurring secondary mutations. This review summarizes current data on the use of ripretinib to treat advanced imatinib-resistant GISTs. We also propose future research directions to improve the targeted GIST treatment.

A Rare Case of Gastrointestinal Stromal Tumor of the Abdominal Cavity: A Case Report

Gastrointestinal stromal tumors (GISTs) are rare gastrointestinal neoplasms. We are presenting a 57-year-old female patient with a GIST of considerable dimensions that was deemed unresectable during the initial intervention. The patient had a previous surgical record of a peritoneal sarcomatosis tumor that covered approximately 50% of the abdominal cavity. The patient underwent surgical procedures, including exploratory laparotomy, lumpectomy, splenectomy, proximal gastrectomy, esophagogastric anastomosis, pyloroplasty, jejunostomy, and left diaphragm plasty. One of the observed results was the presence of a 50×40 cm exophytic multilobed cerebroid-like tumor in the abdomen region, specifically dependent on the gastric fundus. The primary treatment for patients without metastases is surgical removal of the tumor, with wedge resection being recommended for the preservation of organ function and quality of life postoperatively.

SEOM-GEIS clinical guideline for gastrointestinal stromal tumors (2022)

Gastrointestinal stromal tumor (GIST) is the most common malignant neoplasm of mesenchymal origin, and a paradigmatic model for a successful rational development of targeted therapies in cancer. 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. These guidelines are elaborated by the conjoint effort of the Spanish Society of Medical Oncology (SEOM) and the Spanish Sarcoma Research Group (GEIS) and 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.

2023 GEIS Guidelines for gastrointestinal stromal tumors

Gastrointestinal stromal tumor (GIST) is the most common malignant neoplasm of mesenchymal origin. GIST spans a wide clinical spectrum that ranges from tumors with essentially no metastatic potential to malignant and life-threatening spread diseases. Gain-of-function mutations in KIT or PDGFRA receptor tyrosine kinases are the crucial drivers of most GISTs, responsible for tumor initiation and evolution throughout the entire course of the disease. The introduction of tyrosine kinase inhibitors targeting these receptors has substantially improved the outcomes in this formerly chemoresistant cancer. As of today, five agents hold regulatory approval for the treatment of GIST: imatinib, sunitinib, regorafenib, ripretinib, and avapritinib. This, in turn, represents a success for a rare neoplasm. During the past two decades, GIST has become a paradigmatic model in cancer for multidisciplinary work, given the disease-specific particularities regarding tumor biology and tumor evolution. Herein, we review currently available evidence for the management of GIST. This clinical practice guideline has been developed by a multidisciplinary expert panel (oncologist, pathologist, surgeon, molecular biologist, radiologist, and representative of patients' advocacy groups) from the Spanish Group for Sarcoma Research, and it is conceived to provide, from a critical perspective, the standard approach for diagnosis, treatment, and follow-up.

Antitumor Efficacy of the Novel KIT Inhibitor IDRX-42 (Formerly M4205) in Patient- and Cell Line-Derived Xenograft Models of Gastrointestinal Stromal Tumor (GIST)

PURPOSE

The majority of gastrointestinal stromal tumors (GIST) are driven by constitutively activated KIT/PDGFRA kinases and are susceptible to treatment with tyrosine kinase inhibitors. During treatment, most of these tumors will develop secondary mutations in KIT or PDGFRA inducing drug resistance, so there is an unmet need for novel therapies. We tested the efficacy of IDRX-42, a novel selective KIT inhibitor with high activity toward the most relevant KIT mutations, in 4 GIST xenograft models.

EXPERIMENTAL DESIGN

NMRI nu/nu mice were transplanted with patient-derived GIST xenograft models UZLX-GIST9 (KIT:p.P577del;W557LfsX5;D820G), UZLX-GIST2B (KIT:p.A502_Y503dup), UZLX-GIST25 (KIT:p.K642E), and the cell line-derived model GIST882 (KIT:p.K642E). Mice were treated daily with vehicle (control), imatinib (100 mg/kg), sunitinib (20 mg/kg), avapritinib (5 mg/kg), or IDRX-42 (10 mg/kg, 25 mg/kg). Efficacy was assessed by tumor volume evolution, histopathology, grading of histologic response, and IHC. The Kruskal-Wallis and Wilcoxon matched-pairs tests were used for statistical analysis, with P < 0.05 considered as significant.

RESULTS

IDRX-42 (25 mg/kg) caused tumor volume shrinkage in UZLX-GIST25, GIST882, and UZLX-GIST2B, with a relative decrease to 45.6%, 57.3%, and 35.1% on the last day as compared with baseline, and tumor growth delay (160.9%) compared with control in UZLX-GIST9. Compared with controls, IDRX-42 (25 mg/kg) induced a significant decrease in mitosis. In UZLX-GIST25 and GIST882 grade 2-4 histologic response with myxoid degeneration was observed in all IDRX-42 (25 mg/kg)-treated tumors.

CONCLUSIONS

IDRX-42 showed significant antitumor activity in patient- and cell line-derived GIST xenograft models. The novel kinase inhibitor induced volumetric responses, decreased mitotic activity, and had antiproliferative effects. In models with KIT exon 13 mutation IDRX-42 induced characteristic myxoid degeneration.

Circulating tumor DNA analysis of the phase III VOYAGER trial: KIT mutational landscape and outcomes in patients with advanced gastrointestinal stromal tumor treated with avapritinib or regorafenib

BACKGROUND

The current treatment paradigm of imatinib-resistant metastatic gastrointestinal stromal tumor (GIST) does not incorporate KIT/PDGFRA genotypes in therapeutic drug sequencing, except for PDGFRA exon 18-mutant GIST that is indicated for avapritinib treatment. Here, circulating tumor DNA (ctDNA) sequencing was used to analyze plasma samples prospectively collected in the phase III VOYAGER trial to understand how the KIT/PDGFRA mutational landscape contributes to tyrosine kinase inhibitor (TKI) resistance and to determine its clinical validity and utility.

PATIENTS AND METHODS

VOYAGER (N = 476) compared avapritinib with regorafenib in patients with KIT/PDGFRA-mutant GIST previously treated with imatinib and one or two additional TKIs (NCT03465722). KIT/PDGFRA ctDNA mutation profiling of plasma samples at baseline and end of treatment was assessed with 74-gene Guardant360® CDx. Molecular subgroups were determined and correlated with outcomes.

RESULTS

A total of 386/476 patients with KIT/PDGFRA-mutant tumors underwent baseline (pre-trial treatment) ctDNA analysis; 196 received avapritinib and 190 received regorafenib. KIT and PDGFRA mutations were detected in 75.1% and 5.4%, respectively. KIT resistance mutations were found in the activation loop (A-loop; 80.4%) and ATP-binding pocket (ATP-BP; 40.8%); 23.4% had both. An average of 2.6 KIT mutations were detected per patient; 17.2% showed 4-14 different KIT resistance mutations. Of all pathogenic KIT variants, 28.0% were novel, including alterations in exons/codons previously unreported. PDGFRA mutations showed similar patterns. ctDNA-detected KIT ATP-BP mutations negatively prognosticated avapritinib activity, with a median progression-free survival (mPFS) of 1.9 versus 5.6 months for regorafenib. mPFS for regorafenib did not vary regardless of the presence or absence of ATP-BP/A-loop mutants and was greater than mPFS with avapritinib in this population. Secondary KIT ATP-BP pocket mutation variants, particularly V654A, were enriched upon disease progression with avapritinib.

CONCLUSIONS

ctDNA sequencing efficiently detects KIT/PDGFRA mutations and prognosticates outcomes in patients with TKI-resistant GIST treated with avapritinib. ctDNA analysis can be used to monitor disease progression and provide more personalized treatment.

Tumor Microenvironment Remodeling in Gastrointestinal Cancer: Role of miRNAs as Biomarkers of Tumor Invasion

Gastrointestinal (GI) cancers are the most frequent neoplasm, responsible for half of all cancer-related deaths. Metastasis is the leading cause of death from GI cancer; thus, studying the processes that regulate cancer cell migration is of paramount importance for the development of new therapeutic strategies. In this review, we summarize the mechanisms adopted by cancer cells to promote cell migration and the subsequent metastasis formation by highlighting the key role that tumor microenvironment components play in deregulating cellular pathways involved in these processes. We, therefore, provide an overview of the role of different microRNAs in promoting tumor metastasis and their role as potential biomarkers for the prognosis, monitoring, and diagnosis of GI cancer patients. Finally, we relate the possible use of nutraceuticals as a new strategy for targeting numerous microRNAs and different pathways involved in GI tumor invasiveness.

LIX1 Controls MAPK Signaling Reactivation and Contributes to GIST-T1 Cell Resistance to Imatinib

Gastrointestinal stromal tumor (GIST), the most common sarcoma, is mainly caused by an oncogenic mutation in the KIT receptor tyrosine kinase. Targeting KIT using tyrosine kinase inhibitors, such as imatinib and sunitinib, provides substantial benefit; however, in most patients, the disease will eventually progress due to KIT secondary mutations leading to treatment failure. Understanding how GIST cells initially adapt to KIT inhibition should guide the selection of appropriate therapies to overcome the emergence of resistance. Several mechanisms have been broadly implicated in the resistance to imatinib anti-tumoral effects, including the reactivation of MAPK signaling upon KIT/PDGFRA targeted inhibition. This study provides evidence that LImb eXpression 1 (LIX1), a protein we identified as a regulator of the Hippo transducers YAP1 and TAZ, is upregulated upon imatinib or sunitinib treatment. LIX1 silencing in GIST-T1 cells impaired imatinib-induced MAPK signaling reactivation and enhanced imatinib anti-tumor effect. Our findings identified LIX1 as a key regulator of the early adaptative response of GIST cells to targeted therapies.

Whole-genome and Epigenomic Landscapes of Malignant Gastrointestinal Stromal Tumors Harboring KIT Exon 11 557-558 Deletion Mutations

Gastrointestinal stromal tumors (GIST) with KIT exon 11 deletions involving in codons 557-558 (KIT Δ557-558) exhibit higher proliferation rates and shorter disease-free survival times compared with GISTs with other KIT exon 11 mutations. We analyzed 30 GIST cases and observed genomic instability and global DNA hypomethylation only in high-risk malignant GISTs with KIT Δ557-558. Whole-genome sequencing revealed that the high-risk malignant GISTs with KIT Δ557-558 (12 cases) had more structural variations (SV), single-nucleotide variants, and insertions and deletions compared with the low-risk, less malignant GISTs with KIT Δ557-558 (six cases) and the high-risk (six cases) or low-risk (6 cases) GISTs with other KIT exon 11 mutations. The malignant GISTs with KIT Δ557-558 showed higher frequency and significance in copy number (CN) reduction on chromosome arms 9p and 22q, and 50% of them had LOH or CN-dependent expression reduction in CDKN2A. In addition, SVs with driver potential were detected in 75% of them, in which AKT3 and MGMT were recurrently identified. Genome-wide DNA methylation and gene expression analyses showed global intergenic DNA hypomethylation, SNAI2 upregulation, and higher expression signatures, including p53 inactivation and chromosomal instability, as characteristics of malignant GISTs with KIT Δ557-558 that distinguished them from other GISTs. These genomic and epigenomic profiling results revealed that KIT Δ557-558 mutations are associated with increased genomic instability in malignant GISTs.

Significance

We present genomic and epigenomic insights into the malignant progression of GISTs with KIT exon 11 deletions involving in 557-558, demonstrating their unique chromosomal instability and global intergenic DNA hypomethylation.

Neuropsychiatric Adverse Drug Reactions with Tyrosine Kinase Inhibitors in Gastrointestinal Stromal Tumors: An Analysis from the European Spontaneous Adverse Event Reporting System

Tyrosine kinase inhibitors (TKIs) are widely used in gastrointestinal stromal tumors (GISTs). The aim of this study is to evaluate the reporting frequency of neuropsychiatric adverse drug reactions (ADRs) for TKIs through the analysis of European individual case safety reports (ICSRs). All ICSRs collected in EudraVigilance up to 31 December 2021 with one TKI having GISTs as an indication (imatinib (IM), sunitinib (SU), avapritinib (AVA), regorafenib (REG), and ripretinib (RIP)) were included. A disproportionality analysis was performed to assess the frequency of reporting for each TKI compared to all other TKIs. The number of analyzed ICSRs was 8512, of which 57.9% were related to IM. Neuropsychiatric ADRs were reported at least once in 1511 ICSRs (17.8%). A higher reporting probability of neuropsychiatric ADRs was shown for AVA. Most neuropsychiatric ADRs were known, except for a higher frequency of lumbar spinal cord and nerve root disorders (reporting odds ratio, ROR 4.46; confidence interval, CI 95% 1.58–12.54), olfactory nerve disorders (8.02; 2.44–26.33), and hallucinations (22.96; 8.45–62.36) for AVA. The analyses of European ICSRs largely confirmed the safety profiles of TKIs in GISTs, but some ADRs are worthy of discussion. Further studies are needed to increase the knowledge of the neuropsychiatric disorders of newly approved TKIs.

Deubiquitylation of Rab35 by USP32 promotes the transmission of imatinib resistance by enhancing exosome secretion in gastrointestinal stromal tumours

Imatinib is a tyrosine kinase inhibitor that is widely used to combat gastrointestinal stromal tumours (GISTs). However, secondary resistance to imatinib is an important challenge in GIST treatment. Recent studies have demonstrated that cancer-derived nanosized exosomes play a key role in intercellular communication, but little is known about the roles of exosomes in imatinib-resistant GISTs. Here, we reveal that exosomes released from imatinib-resistant GISTs transmit drug resistance to imatinib-sensitive tumours. By using iTRAQ technology, we demonstrate that Ras-related protein Rab-35 (Rab35) is upregulated differentially in imatinib-resistant GISTs. Loss of Rab35 decreases exosome secretion, thereby hampering the transmission of imatinib resistance to sensitive tumours. Mechanistically, we showed that the ubiquitin‒proteasome system is involved in elevated Rab35 expression and that ubiquitin-specific protease 32 (USP32), a deubiquitylating enzyme, is bound to Rab35. Further experiments demonstrate that this protease protects Rab35 from proteasomal degradation by reducing Lys48 (K48)-ubiquitination. Additionally, we found that the transcription factor ETV1, which is a lineage survival factor in GISTs, promotes USP32 expression. Collectively, our results reveal that exosomes transmit imatinib resistance in GISTs and that deubiquitylation plays a key role in regulating the transmission process. The USP32-Rab35 axis provides a potential target for interventions to reduce the occurrence of imatinib resistance in GISTs.

The microphthalmia-associated transcription factor is involved in gastrointestinal stromal tumor growth

Gastrointestinal stromal tumors (GISTs) are the most common neoplasms of mesenchymal origin, and most of them emerge due to the oncogenic activation of KIT or PDGFRA receptors. Despite their relevance in GIST oncogenesis, critical intermediates mediating the KIT/PDGFRA transforming program remain mostly unknown. Previously, we found that the adaptor molecule SH3BP2 was involved in GIST cell survival, likely due to the co-regulation of the expression of KIT and Microphthalmia-associated transcription factor (MITF). Remarkably, MITF reconstitution restored KIT expression levels in SH3BP2 silenced cells and restored cell viability. This study aimed to analyze MITF as a novel driver of KIT transforming program in GIST. Firstly, MITF isoforms were characterized in GIST cell lines and GIST patients' samples. MITF silencing decreases cell viability and increases apoptosis in GIST cell lines irrespective of the type of KIT primary or secondary mutation. Additionally, MITF silencing leads to cell cycle arrest and impaired tumor growth in vivo. Interestingly, MITF silencing also affects ETV1 expression, a linage survival factor in GIST that promotes tumorigenesis and is directly regulated by KIT signaling. Altogether, these results point to MITF as a key target of KIT/PDGFRA oncogenic signaling for GIST survival and tumor growth.

Chinese Pedigree with Hereditary Gastrointestinal Stromal Tumors: A Case Report and Literature Review

Familial gastrointestinal stromal tumor (GIST) is a rare autosomal dominant genetic disorder with only a few affected families reported to date. Here, we report a case of familial GISTs harboring a novel germline mutation within exon 18 of KIT. A 58-year-old male patient presented with gastric subepithelial lesions accompanied by cutaneous hyperpigmentation, which were subsequently diagnosed as multinodular GISTs. Endoscopic surgery was initially conducted to remove the larger lesions, and pathological examinations were then conducted for the diagnosis of GISTs. Family history revealed that some other family members had similar cutaneous pigmentations. Whole-exome sequencing was used to search for potential driver mutations, and Sanger sequencing was used for mutation validation. A novel primary driver mutation of KIT (c.G2485C, p.A829P) was detected in these hereditary GISTs, which has been reported in some targeted chemotherapy-resistant GISTs. Cell models were subsequently established for the rapid screening of candidate drugs and exploring potential mechanisms. This mutation could lead to cell proliferation and imatinib resistance by ligand-independent activation of KIT; however, ripretinib administration was identified as an applicable targeted therapy for this mutation. The mutation activated the JAK/STAT3 and MAPK/ERK pathways, which could be inhibited by ripretinib administration. To the best of our knowledge, this is the first report of the KIT-A829P mutation in familial GISTs, complementing the pathogenesis of familial GISTs and providing valuable information for the precision treatment of this disease.

Transcriptomic study of gastrointestinal stromal tumors with liver metastasis

Introduction: GIST (gastrointestinal stromal tumor) is the most prominent mesenchymal neoplasms of the gastrointestinal tract, and liver is the most common metastasis site for GIST. The molecular mechanism leading to liver metastasis of GIST is currently unclear. Methods: With the goal of revealing the underlying mechanism, we performed whole-genome gene expression profiling on 18 pairs of RNA samples comprised of GIST tissues (with liver metastasis) and corresponding non-tumor tissues. After identifying differentially expressed gene, functional annotation and signal pathway analyses were conducted. GSE13861, datasets that compare GIST (without liver metastasis) with adjacent tissues, served as a comparison. Results: A total of 492 up-regulated genes and 629 down-regulated genes were identified as differentially expressed genes between liver metastasis tissues and non-tumor tissues. We characterized expression patterns of DEGs identified from our cohort and GSE13861 that show signatures of enrichment for functionality. In subsequent gene set enrichment analysis, differentially expressed genes were mainly enriched in Epithelial Mesenchymal Transition in both datasets. 493 genes were overlapped among our whole-genome gene expression profiling results and GSE13861, consisting 188 up-regulated genes and 305 down-regulated genes. By using CytoHubba plugin of Cytoscape, CDH1, CD34, KIT, PROM1, SOX9, FGF2, CD24, ALDH1A1, JAG1 and NES were identified as top ten hub genes in tumorigenesis and liver metastasis of GIST. higher expression levels of FGF2, JAG1, CD34, ALDH1A1 and the lower expression level of CDH1 were respectively associated with unfavorable overall survival. Meanwhile higher expression levels of CD34, FGF2, KIT, JAG1, ALDH1A were correlated with worse disease-free survival. Discussion: The present study may help to provide candidate pathways and targets for treatment of GIST and prevention methods to liver metastasis.

Identification of Thiazolo[5,4-b]pyridine Derivatives as c-KIT Inhibitors for Overcoming Imatinib Resistance

c-KIT is a promising therapeutic target against gastrointestinal stromal tumor (GIST). In order to identify novel c-KIT inhibitors capable of overcoming imatinib resistance, we synthesized 31 novel thiazolo[5,4-b]pyridine derivatives and performed SAR studies. We observed that, among these substances, 6r is capable of inhibiting significantly c-KIT and suppressing substantially proliferation of GIST-T1 cancer cells. It is of note that 6r is potent against a c-KIT V560G/D816V double mutant resistant to imatinib. Compared with sunitinib, 6r possesses higher differential cytotoxicity on c-KIT D816V Ba/F3 cells relative to parental Ba/F3 cells. In addition, kinase panel profiling reveals that 6r has reasonable kinase selectivity. It was found that 6r remarkably attenuates proliferation of cancer cells via blockade of c-KIT downstream signaling, and induction of apoptosis and cell cycle arrest. Furthermore, 6r notably suppresses migration and invasion, as well as anchorage-independent growth of GIST-T1 cells. This study provides useful SAR information for the design of novel c-KIT inhibitors overcoming imatinib-resistance.

Development of an innovative nomogram of risk factors to predict postoperative recurrence of gastrointestinal stromal tumors

BACKGROUND

There are many staging systems for gastrointestinal stromal tumors (GISTs), and the risk indicators selected are also different; thus, it is not possible to quantify the risk of recurrence among individual patients.

AIM

To develop and internally validate a model to identify the risk factors for GIST recurrence after surgery.

METHODS

The least absolute shrinkage and selection operator (LASSO) regression model was performed to identify the optimum clinical features for the GIST recurrence risk model. Multivariable logistic regression analysis was used to develop a prediction model that incorporated the possible factors selected by the LASSO regression model. The index of concordance (C-index), calibration curve, receiver operating characteristic curve (ROC), and decision curve analysis were used to assess the discrimination, calibration, and clinical usefulness of the predictive model. Internal validation of the clinical predictive capability was also evaluated by bootstrapping validation.

RESULTS

The nomogram included tumor site, lesion size, mitotic rate/50 high power fields, Ki-67 index, intracranial necrosis, and age as predictors. The model presented perfect discrimination with a reliable C-index of 0.836 (95%CI: 0.712-0.960), and a high C-index value of 0.714 was also confirmed by interval validation. The area under the curve value of this prediction nomogram was 0.704, and the ROC result indicated good predictive value. Decision curve analysis showed that the predicting recurrence nomogram was clinically feasible when the recurrence rate exceeded 5% after surgery.

CONCLUSION

This recurrence nomogram combines tumor site, lesion size, mitotic rate, Ki-67 index, intracranial necrosis, and age and can easily predict patient prognosis.

Protein tyrosine kinase inhibitor resistance in malignant tumors: molecular mechanisms and future perspective

Protein tyrosine kinases (PTKs) are a class of proteins with tyrosine kinase activity that phosphorylate tyrosine residues of critical molecules in signaling pathways. Their basal function is essential for maintaining normal cell growth and differentiation. However, aberrant activation of PTKs caused by various factors can deviate cell function from the expected trajectory to an abnormal growth state, leading to carcinogenesis. Inhibiting the aberrant PTK function could inhibit tumor growth. Therefore, tyrosine kinase inhibitors (TKIs), target-specific inhibitors of PTKs, have been used in treating malignant tumors and play a significant role in targeted therapy of cancer. Currently, drug resistance is the main reason for limiting TKIs efficacy of cancer. The increasing studies indicated that tumor microenvironment, cell death resistance, tumor metabolism, epigenetic modification and abnormal metabolism of TKIs were deeply involved in tumor development and TKI resistance, besides the abnormal activation of PTK-related signaling pathways involved in gene mutations. Accordingly, it is of great significance to study the underlying mechanisms of TKIs resistance and find solutions to reverse TKIs resistance for improving TKIs efficacy of cancer. Herein, we reviewed the drug resistance mechanisms of TKIs and the potential approaches to overcome TKI resistance, aiming to provide a theoretical basis for improving the efficacy of TKIs.

THZ1 targeting CDK7 suppresses c-KIT transcriptional activity in gastrointestinal stromal tumours

Background

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the gastrointestinal tract and are characterized by activating mutations of c-KIT or PDGFRa receptor tyrosine kinases (RTKs). Despite the clinical success of tyrosine kinase inhibitors (TKIs), more than half of GIST patients develop resistance due to a second mutation. Cyclin-dependent kinase 7 (CDK7) is the catalytic subunit of CDK-activating kinase (CAK), and it plays an important role in the regulation of cell cycle transitions and gene transcription. THZ1, a CDK7 inhibitor, exhibits a dose-dependent inhibitory effect in various cancers.

Methods

Data from the public GEO database and tissue microarray were used to analyse the gene expression levels of CDKs in GISTs. The impact of CDK7 knockdown and the CDK7 inhibitor THZ1 on GIST progression was investigated in vitro using CCK-8, colony formation, and flow cytometry assays and in vivo using a xenograft mouse model. RNA sequencing was performed to investigate the mechanism of GIST cell viability impairment mediated by THZ1 treatment.

Results

Our study demonstrated that CDK7 is relatively overexpressed in high-risk GISTs and predicts a poor outcome. A low concentration of THZ1 exhibited a pronounced antineoplastic effect in GIST cells in vivo and in vitro. Moreover, THZ1 exerted synergistic anticancer effects with imatinib. THZ1 treatment resulted in transcriptional modulation by inhibiting the phosphorylation of Ser2, Ser5, and Ser7 within RNA polymerase II (RNAPII). c-KIT, an oncogene driver of GIST, was transcriptionally repressed by THZ1 treatment or CDK7 knockdown. Transcriptome sequencing analysis showed that OSR1 acts as a downstream target of CDK7 and regulates c-KIT expression. Taken together, our results highlight elevated CDK7 expression as a predictor of poor outcome in GIST and present the combination of CDK7 and RTK inhibitors as a potent therapeutic strategy to improve the efficacy of GIST treatment.

An overview of agents and treatments for PDGFRA-mutated gastrointestinal stromal tumors

Platelet-derived growth factor receptor A (PDGFRA) mutations occur in approximately 10-15% of gastrointestinal stromal tumors (GISTs). These tumors with PDGFRA mutations have a different pathogenesis, clinical characteristics, and treatment response compared to tumors with receptor tyrosine kinase protein (KIT) mutations (60-70%). Many clinical studies have investigated the use of tyrosine kinase inhibitors mainly in patients with KIT mutations; however, there is a lack of attention to the PDGFRA-mutated molecular subtype. The main effective inhibitors of PDGFRA are ripretinib, avapritinib, and crenolanib, and their mechanisms and efficacy in GIST (as confirmed in clinical trials) are described in this review. Some multi-targeted tyrosine kinase inhibitors with inhibitory effects on this molecular subtype are also introduced and summarized in this paper. This review focuses on PDGFRA-mutated GISTs, introduces their clinical characteristics, downstream molecular signaling pathways, and existing resistance mechanisms. We focus on the most recent literature that describes the development of PDGFRA inhibitors and their use in clinical trials, as well as the potential benefits from different combination therapy strategies.

Exploratory analysis of tumor imaging in a Phase 2 trial with cabozantinib in gastrointestinal stromal tumor: lessons learned from study EORTC STBSG 1317 'CaboGIST'

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are malignant mesenchymal tumors arising in the gastrointestinal tract. Their systemic treatment is based on the use of tyrosine kinase inhibitors (TKIs) with imatinib, sunitinib, and regorafenib being the preferred agents. Assessment of tumor response to TKI treatment in GISTs is traditionally done according the Response Evaluation Criteria in Solid Tumors (RECIST), while Choi criteria have also been proposed as alternative tool assessing both volumetric and density changes on computer tomography (CT) scans. EORTC STBSG 1317 'CaboGIST' was a single-arm prospective Phase 2 trial which met its primary endpoint, as 60% of patients previously treated with imatinib and sunitinib were progression-free at 12 weeks (95% CI 45-74%) based on local RECIST assessment.

MATERIALS AND METHODS

We report here an exploratory analysis of local versus central RECIST version 1.1 assessment and a comparison of RECIST version 1.1 versus Choi criteria.

RESULTS

Comparisons between local and central RECIST version 1.1 at week 12 revealed discrepancies in 17/43 evaluable cases (39.5%). When comparing Choi with local and central RECIST version 1.1, discrepancies were observed in 27/43 (62.8%) and 21/43 (48.8%) cases, respectively. A total of 68% of evaluable patients were progression-free and alive at week 12 based on local RECIST, 84% according to central RECIST analysis and 81% when applying Choi criteria. Central assessment upgraded the treatment response both with RECIST version 1.1 and Choi.

CONCLUSIONS

The results of this exploratory analysis support the conclusion that cabozantinib is active in patients with metastatic or recurrent GIST after treatment with imatinib and sunitinib and confirm once again the limitations of RECIST to capture response to TKI in GIST, and the importance to include density changes in the response evaluation in this setting. Clinical trial number: EORTC 1317, NCT02216578.

The GIST of Advances in Treatment of Advanced Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor (GIST) is the most common malignant neoplasm of mesenchymal origin and a compelling clinical and biologic model for the rational development of molecularly targeted agents. This is because the majority of GISTs are driven by gain-of-function mutations in KIT or PDGFRA receptor tyrosine kinases. Specific GIST mutations circumscribe well-defined molecular subgroups that must be determined during the diagnostic work-up to guide clinical management, including therapeutic decisions. Surgery is the cornerstone treatment in localized disease and can also be clinically relevant in the metastatic setting. The correct combination and sequence of targeted agents and surgical procedures improves outcomes for patients with GIST and should be discussed individually within multidisciplinary expert teams. All currently approved agents for the treatment of GIST are based on orally available tyrosine kinase inhibitors targeting KIT and PDGFRA oncogenic activation. Although first-line imatinib achieves remarkable prolonged disease control, the benefit of subsequent lines of treatment is more modest. Novel therapeutic strategies focus on overcoming the heterogeneity of KIT or PDGFRA secondary mutations and providing more potent inhibition of specific challenging mutations. This article reviews the current understanding and treatment of GIST, with an emphasis on recent advances.

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.

Patient demographics, clinicopathologic features, and outcomes in wild-type gastrointestinal stromal tumor: a national cohort analysis

Wild-type KIT and PDGFRA gastrointestinal stromal tumors (GIST) are rare tumors with limited treatment options. We sought to determine the clinicopathologic features of wild-type GIST and identify factors that influence overall survival (OS) using a large national database. Retrospective evaluation of patients with wild-type GIST in the National Cancer Database (NCDB) was performed. Demographic, clinicopathologic, and treatment data were analyzed. Features associated with OS were investigated using Kaplan-Meier analysis and Cox proportional hazards model. 244 patients with median diagnosis age of 59 years (95% CI 57-63) were identified. The stomach was the most common primary site (57%) followed by the small intestine (35%). Surgical resection was performed on 85% of patients and 53% of patients received systemic therapy. Factors associated with decreased OS on multivariable analysis included small intestine primary (HR 2.72, 95% CI 1.13-6.69, P = 0.026) and > 5 mitoses per 50 HPF (HR 4.77, 95% CI 1.86-13.2, P = 0.001). Wild-type GISTs may be identified in older patients, with most arising in the stomach and small bowel. Surgery remains the principal treatment modality. Small intestine primary site and high mitotic count were associated with abbreviated OS.

Noncoding RNAs in Drug Resistance of Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor in the gastrointestinal tracts and a model for the targeted therapy of solid tumors because of the oncogenic driver mutations in KIT and PDGDRA genes, which could be effectively inhibited by the very first targeted agent, imatinib mesylate. Most of the GIST patients could benefit a lot from the targeted treatment of this receptor tyrosine kinase inhibitor. However, more than 50% of the patients developed resistance within 2 years after imatinib administration, limiting the long-term effect of imatinib. Noncoding RNAs (ncRNAs), the non-protein coding transcripts of human, were demonstrated to play pivotal roles in the resistance of various chemotherapy drugs. In this review, we summarized the mechanisms of how ncRNAs functioning on the drug resistance in GIST. During the drug resistance of GIST, there were five regulating mechanisms where the functions of ncRNAs concentrated: oxidative phosphorylation, autophagy, apoptosis, drug target changes, and some signaling pathways. Also, these effects of ncRNAs in drug resistance were divided into two aspects. How ncRNAs regulate drug resistance in GIST was further summarized according to ncRNA types, different drugs and categories of resistance. Moreover, clinical applications of these ncRNAs in GIST chemotherapies concentrated on the prognostic biomarkers and novel therapeutic targets.

Postoperative Adjuvant Imatinib Therapy-Associated Nomogram to Predict Overall Survival of Gastrointestinal Stromal Tumor

BACKGROUND

Adjuvant imatinib therapy has been shown to improve overall survival (OS) of gastrointestinal stromal tumor (GIST) significantly. Few nomograms combining the use of adjuvant imatinib and clinicopathological characteristics estimate the outcome of patients. We aimed to establish a more comprehensive nomogram for predicting OS in patients with GIST.

METHODS

In total, 1310 GIST patients undergoing curative resection at four high-volume medical centers between 2001 and 2015 were enrolled. Independent prognostic factors were identified by multivariate Cox analysis. Eligible patients were randomly assigned in a ratio of 7:3 into a training set (916 cases) and a validation set (394 cases). A nomogram was established by R software and its predictive power compared with that of the modified National Institutes of Health (NIH) classification using time-dependent receiver operating characteristic (ROC) curves and calibration plot.

RESULTS

Age, tumor site, tumor size, mitotic index, postoperative imatinib and diagnostic delay were identified as independent prognostic parameters and used to construct a nomogram. Of note, diagnostic delay was for the first time included in a prognostic model for GIST. The calibrated nomogram resulted in predicted survival rates consistent with observed ones. And the decision curve analysis suggested that the nomogram prognostic model was clinically useful. Furthermore, time-dependent ROC curves showed the nomogram exhibited greater discrimination power than the modified NIH classification in 3- and 5-year survival predictions for both training and validation sets (all P < 0.05).

CONCLUSIONS

Postoperative adjuvant imatinib therapy improved the survival of GIST patients. We developed and validated a more comprehensive prognostic nomogram for GIST patients, and it could have important clinical utility in improving individualized predictions of survival risks and treatment decision-making.

E3 ubiquitin ligase Atrogin-1 mediates adaptive resistance to KIT-targeted inhibition in gastrointestinal stromal tumor

KIT/PDGFRA oncogenic tyrosine kinase signaling is the central oncogenic event in most gastrointestinal stromal tumors (GIST), which are human malignant mesenchymal neoplasms that often feature myogenic differentiation. Although targeted inhibition of KIT/PDGFRA provides substantial clinical benefit, GIST cells adapt to KIT/PDGFRA driver suppression and eventually develop resistance. The specific molecular events leading to adaptive resistance in GIST remain unclear. By using clinically representative in vitro and in vivo GIST models and GIST patients' samples, we found that the E3 ubiquitin ligase Atrogin-1 (FBXO32)-the main effector of muscular atrophy in cachexia-resulted in the most critical gene derepressed in response to KIT inhibition, regardless the type of KIT primary or secondary mutation. Atrogin-1 in GISTs is transcriptionally controlled by the KIT-FOXO3a axis, thus indicating overlap with Atrogin-1 regulation mechanisms in nonneoplastic muscle cells. Further, Atrogin-1 overexpression was a GIST-cell-specific pro-survival mechanism that enabled the adaptation to KIT-targeted inhibition by apoptosis evasion through cell quiescence. Buttressed on these findings, we established in vitro and in vivo the preclinical proof-of-concept for co-targeting KIT and the ubiquitin pathway to maximize the therapeutic response to first-line imatinib treatment.

Not all KIT 557/558 codons mutations have the same prognostic influence on recurrence-free survival: breaking the exon 11 mutations in gastrointestinal stromal tumors (GISTs)

Background:

Although the gastrointestinal stromal tumor (GIST) genotype is not currently included in risk-stratification systems, a growing body of evidence shows that the pathogenic variant (PV) type and codon location hold a strong prognostic influence on recurrence-free survival (RFS). This information has particular relevance in the adjuvant setting, where an accurate prognostication could help to better identify high-risk tumors and guide clinical decision-making.

Materials and Methods:

Between January 2005 and December 2020, 96 patients with completely resected GISTs harboring a KIT proto-oncogene receptor tyrosine kinase (KIT) exon 11 PV were included in the study. We analyzed the type and codon location of the PV according to clinicopathological characteristics and clinical outcome; the metastatic sites in relapsed patients were also investigated.

Results:

Tumors harboring a KIT exon 11 deletion or deletion/insertion involving the 557 and/or 558 codons, showed a more aggressive clinical behavior compared with tumors carrying deletion/deletion/insertion in other codons, or tumors with duplication/insertion/single-nucleotide variant (SNV) (7-year RFS: 50% versus 73.1% versus 88.2%, respectively; p < 0.001). Notably, among 18 relapsed patients with 557 and/or 558 deletion or deletion/insertion, 14 patients (77.8%) harbored deletions simultaneously involving 557 and 558 codons, while only 4 patients (22.2%) harbored deletions involving only 1 of the 557/558 codons. Thus, when 557 or 558 deletions occurred separately, the tumor showed a prognostic behavior similar to the GIST carrying deletions outside the 557/558 position. Remarkably, patients with GISTs stratified as intermediate risk, but carrying the 557/558 deletion, showed a similar outcome to the high-risk patients with tumors harboring deletions in codons other than 557/558, or duplication/insertion/SNV.

Conclusion:

Our data support the inclusion of the PV type and codon location in routine risk prediction models, and suggest that intermediate-risk patients whose GISTs harbor 557/558 deletions may also need to be treated with adjuvant imatinib like the high-risk patients.

Surgical Resection Is Still Better Than Endoscopic Resection for Patients With 2-5 cm Gastric Gastrointestinal Stromal Tumours: A Propensity Score Matching Analysis

Background

The management of 2-5 cm gastric gastrointestinal stromal tumours (GISTs) is still debated between surgeons and endoscopists. We aimed to investigate short-term and long-term outcomes between surgical resection (SR) and endoscopic resection (ER).

Methods

This study included 67 and 215 patients between 2010 and 2020 who underwent ER and SR, respectively. After propensity score matching, the clinical outcomes were compared. Individual patient information that requires special instructions is also summarized.

Results

After matching, the operation time (P=0.005) and postoperative hospital stay (P=0.005) were significantly longer in the SR group than in the ER group. However, there were no significant differences in blood loss (P=0.741), resection margin (P=1.000) or time to liquid diet (P=0.055). Statistical differences were also seen in en bloc resection (P<0.001) and adverse events (P=0.027). The recurrence rate did not differ significantly between the two techniques, and the mitotic index and ulceration were identified as independent prognostic factors of progression-free survival.

Conclusions

ER might be comparable to SR for the treatment of 2-3 cm gastric GISTs. SR is still considered the standard treatment for 3-5 cm gastric GISTs, while the intraoperative and postoperative information of ER should be recorded in detail and closely evaluated. Surgical resection is recommended if the tumour has a high mitotic index or mucosal ulceration.

Clinicopathological characteristics and longterm survival of patients with synchronous multiple primary gastrointestinal stromal tumors: A propensity score matching analysis

BACKGROUND

Multiple gastrointestinal stromal tumors (MGISTs) are specific and rare. Little is known about the impact of MGISTs on the survival of patients with gastrointestinal stromal tumors (GIST). The diagnosis, treatment and follow-up strategies of MGISTs is not specifically described in guidelines.

AIM

To compare the clinicopathological characteristics and prognosis of MGISTs and solitary GISTs (SGISTs)

METHODS

Patients diagnosed with primary GISTs from March 2010 to January 2020 were included. Due to the inhomogeneous distribution of several baseline characteristics and uneven MGIST and SGIST group sizes, propensity score matching was performed according to comorbidities, body mass index, tumor location, mitotic index, sex, age and American Society of Anesthesiologists score. Differences in clinicopathological characteristics and prognosis between patients with MGISTs and patients with SGISTs were compared.

RESULTS

Among the entire cohort of 983 patients, the incidence of MGISTs was 4.17%. Before matching, patients with MGISTs and those with SGISTs had disparities in body mass index, surgical approach, tumor size and mitotic index. After 1:4 ratio matching, the clinical baseline data were comparable. The 5-year progression-free survival rate was 52.17% in the MGIST group and 75.00% in the SGIST group (P = 0.031). On multivariate analysis, tumor location, tumor size, mitotic index, imatinib treatment and MGISTs (hazard ratio = 2.431, 95% confidence interval = 1.097-5.386, P = 0.029) were identified as independent prognostic factors of progression-free survival. However, overall survival was similar between the SGIST and MGIST groups.

CONCLUSION

Patients with MGISTs had poorer progression-free survival than patients with SGISTs. Risk criteria and diagnostic and treatment strategies should be developed to achieve personalized precision therapy and maximize the survival benefit.

Avapritinib in unresectable or metastatic gastrointestinal stromal tumor with PDGFRA exon 18 mutation: safety and efficacy

INTRODUCTION

Avapritinib (formerly known as BLU-285) is an orally available type I tyrosine kinase inhibitor that, in 2020, obtained regulatory approval for the treatment of patients with gastrointestinal stromal tumors (GISTs) harboring a primary mutation in PDGFRA exon 18, including the PDGFRA D842V mutation.

AREAS COVERED

Herein, we comprehensively review the available efficacy and safety data on avapritinib, with the final goal of providing practical knowledge to both sarcoma and community-based oncologists for the correct management of this rare GIST subpopulation with this novel therapy.

EXPERT OPINION

The approval of avapritinib in GIST is a milestone in precision oncology, as this is the first agent ever demonstrating unequivocal antitumoral activity in GIST driven by the multi-resistant PDGFRA D842V mutation. The safety profile is manageable and tolerability-guided dose adjustment is recommended to manage treatment-related adverse events without compromising efficacy. Based on its unprecedented activity, avapritinib should be considered as first-line therapy for GIST patients harboring this mutation. We strongly recommend to determine KIT/PDGFRA genotype in order to identify the different GIST molecular subtypes and guide treatment decision.

Targeted and immuno-based therapies in sarcoma: mechanisms and advances in clinical trials

Sarcomas represent a distinct group of rare malignant tumors with high heterogeneity. Limited options with clinical efficacy for the metastatic or local advanced sarcoma existed despite standard therapy. Recently, targeted therapy according to the molecular and genetic phenotype of individual sarcoma is a promising option. Among these drugs, anti-angiogenesis therapy achieved favorable efficacy in sarcomas. Inhibitors targeting cyclin-dependent kinase 4/6, poly-ADP-ribose polymerase, insulin-like growth factor-1 receptor, mTOR, NTRK, metabolisms, and epigenetic drugs are under clinical evaluation for sarcomas bearing the corresponding signals. Immunotherapy represents a promising and favorable method in advanced solid tumors. However, most sarcomas are immune "cold" tumors, with only alveolar soft part sarcoma and undifferentiated pleomorphic sarcoma respond to immune checkpoint inhibitors. Cellular therapies with TCR-engineered T cells, chimeric antigen receptor T cells, tumor infiltrating lymphocytes, and nature killer cells transfer show therapeutic potential. Identifying tumor-specific antigens and exploring immune modulation factors arguing the efficacy of these immunotherapies are the current challenges. This review focuses on the mechanisms, advances, and potential strategies of targeted and immune-based therapies in sarcomas.

Delayed adjuvant imatinib in patients with high risk of recurrence of gastrointestinal stromal tumor after radical surgery: a retrospective cohort study

PURPOSE

To investigate the impact of delayed adjuvant imatinib on GIST patients with high risk of recurrence.

METHOD

Adult GIST patients were retrospectively collected from our hospital between 2011 and 2018, and patients having high risk of recurrence were included for subsequent analyses. The primary endpoint was recurrence-free survival (RFS).

RESULTS

According to the interval between the radical surgery and the beginning of adjuvant imatinib, 222 patients were divided into three groups: group A (≤ 2 months, n = 41), group B (2-≤ 4 months, n = 113), and group C (4-≤ 6 months, n = 68). Univariate, multivariate, and survival analyses all showed that patients in group A had significantly more favorable RFS than those in group C but not group B, and patients taking adjuvant imatinib for over 12 months were also associated with longer RFS comparing to adjuvant imatinib of ≤ 12 months. When stratified by the duration of adjuvant imatinib, no significant differences were found in RFS among groups A, B, and C for adjuvant imatinib of ≤ 12 months. While for adjuvant imatinib of over 12 months, both groups A and B had significantly more favorable RFS than group C, and no significant difference in RFS was found between group A and B.

CONCLUSION

Delayed postoperative adjuvant imatinib for over 4 months in patients with high risk of recurrence of GIST may lead to worse RFS, and longer treatment with shorter delay has best results.

Early and Next-Generation KIT/PDGFRA Kinase Inhibitors and the Future of Treatment for Advanced Gastrointestinal Stromal Tumor

The majority of gastrointestinal stromal tumors (GIST) harbor an activating mutation in either the KIT or PDGFRA receptor tyrosine kinases. Approval of imatinib, a KIT/PDGFRA tyrosine kinase inhibitor (TKI), meaningfully improved the treatment of advanced GIST. Other TKIs subsequently gained approval: sunitinib as a second-line therapy and regorafenib as a third-line therapy. However, resistance to each agent occurs in almost all patients over time, typically due to secondary kinase mutations. A major limitation of these 3 approved therapies is that they target the inactive conformation of KIT/PDGFRA; thus, their efficacy is blunted against secondary mutations in the kinase activation loop. Neither sunitinib nor regorafenib inhibit the full spectrum of KIT resistance mutations, and resistance is further complicated by extensive clonal heterogeneity, even within single patients. To combat these limitations, next-generation TKIs were developed and clinically tested, leading to 2 new USA FDA drug approvals in 2020. Ripretinib, a broad-spectrum KIT/PDGFRA inhibitor, was recently approved for the treatment of adult patients with advanced GIST who have received prior treatment with 3 or more kinase inhibitors, including imatinib. Avapritinib, a type I kinase inhibitor that targets active conformation, was approved for the treatment of adults with unresectable or metastatic GIST harboring a PDGFRA exon 18 mutation, including PDGFRA D842V mutations. In this review, we will discuss how resistance mutations have driven the need for newer treatment options for GIST and compare the original GIST TKIs with the next-generation KIT/PDGFRA kinase inhibitors, ripretinib and avapritinib, with a focus on their mechanisms of action.