Translational insights into gastrointestinal stromal tumor and current clinical advances

TATA-box-binding protein-associated factor 15 is a novel biomarker that promotes cell proliferation and migration in gastrointestinal stromal tumor

BACKGROUND

Gastrointestinal stromal tumor (GIST) is a common neoplasm with high rates of recurrence and metastasis, and its therapeutic efficacy is still not ideal. There is an unmet need to find new molecular therapeutic targets for GIST. TATA-box-binding protein-associated factor 15 (TAF15) contributes to the progress of various tumors, while the role and molecular mechanism of TAF15 in GIST progression are still unknown.

AIM

To explore new molecular therapeutic targets for GIST and understand the biological role and underlying mechanisms of TAF15 in GIST progression.

METHODS

Proteomic analysis was performed to explore the differentially expressed proteins in GIST. Western blotting and immunohistochemical analysis were used to verify the expression level of TAF15 in GIST tissues and cell lines. Cell counting kit-8, colony formation, wound-healing and transwell assay were executed to detect the ability of TAF15 on cell proliferation, migration and invasion. A xenograft mouse model was applied to explore the role of TAF15 in the progression of GIST. Western blotting was used to detect the phosphorylation level and total level of RAF1, MEK and ERK1/2.

RESULTS

A total of 1669 proteins were identified as differentially expressed proteins with 762 upregulated and 907 downregulated in GIST. TAF15 was selected for the further study because of its important role in cell proliferation and migration. TAF15 was significantly over expressed in GIST tissues and cell lines. Overexpression of TAF15 was associated with larger tumor size and higher risk stage of GIST. TAF15 knockdown significantly inhibited the cell proliferation and migration of GIST in vitro and suppressed tumor growth in vivo. Moreover, the inhibition of TAF15 expression significantly decreased the phosphorylation level of RAF1, MEK and ERK1/2 in GIST cells and xenograft tissues, while the total RAF1, MEK and ERK1/2 had no significant change.

CONCLUSION

TAF15 is over expressed in GIST tissues and cell lines. Overexpression of TAF15 was associated with a poor prognosis of GIST patients. TAF15 promotes cell proliferation and migration in GIST via the activation of the RAF1/MEK/ERK signaling pathway. Thus, TAF15 is expected to be a novel latent molecular biomarker or therapeutic target of GIST.

New insight on the correlation of immune landscapes with immune markers expression in different risk classification of gastrointestinal stromal tumors

BACKGROUND

The immune landscapes of gastrointestinal stromal tumors (GISTs) are still unclear. We aimed to explore the immune status of GISTs with different recurrence risks and sought potential immunotherapeutic targets.

METHODS

Immune cell infiltration and the expression of 93 tumor markers of 65 GISTs with different recurrence risks from public datasets were analyzed via bioinformatic methods. Infiltrating immune cell and OX40L expression of 417 patients from the Zhongshan cohort were analyzed by immunohistochemistry and immunofluorescence. The clinicopathological data of the patients were collected and the prognostic factors were analyzed by univariate and multivariate methods.

RESULTS

Macrophages, T cells and NK cells were the most abundant immune cells in tumor microenvironment. OX40L was the only differentially expressed marker in high- and low-risk patients, as well as in patients with primary and recurrent GIST. The positive rate of OX40L in GIST was 54%. OX40L was highly expressed in patients with no metastasis, low mitotic index and relapse risk. The amount of CD68 + macrophages was the independent factor of OX40L expression. The OX40L expression was positively correlated with M2 and resting mast cells. OX40L co-located with CD4 + T cells, M2 and activated mast cells. Patients with high OX40L levels experienced more prolonged relapse-free survival (RFS).

CONCLUSIONS

We first reported that GIST cells could express OX40L, patients with high OX40L experienced longer RFS. The colocalization of OX40L with immune cells indicates that OX40L could be a promising potential target for immunotherapy in GIST.

4-(Imidazo[1,2-a]pyridin-3-yl): pyrimidine derivatives as anticancer agents

A series of 4-(imidazo[1,2-a]pyridin-3-yl)-pyrimidine derivatives are claimed as inhibitors of c-KIT and as potential treatments for cancer. Their chemical preparation and biological evaluation against imatinib-resistant tumor cells have been described. Several claimed molecules have excellent IC50 values in the nanomolar range. Several molecules were also selective against a wide panel of kinases. Few specific inhibitors have been found to have promising oral bioavailability and acceptable to excellent values regarding the inhibition of hERG channel. This class represents a new platform for developing new anticancer treatment against a wide range of c-KIT mutations and secondary mutations that may arise in gastrointestinal stromal tumor patients.

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.

Advances of endoscopic and surgical management in gastrointestinal stromal tumors

As one of the most common mesenchymal malignancies in the digestive system, gastrointestinal stromal tumors (GISTs) occur throughout the alimentary tract with diversified oncological characteristics. With the advent of the tyrosine kinase inhibitor era, the treatment regimens of patients with GISTs have been revolutionized and GISTs have become the paradigm of multidisciplinary therapy. However, surgery resection remains recognized as the potentially curative management for the radical resection and provided with favorable oncological outcomes. The existing available surgery algorithms in clinical practice primarily incorporate open procedure, and endoscopic and laparoscopic surgery together with combined operation techniques. The performance of various surgery methods often refers to the consideration of risk evaluation of recurrence and metastases; the degree of disease progression; size, location, and growth pattern of tumor; general conditions of selected patients; and indications and safety profile of various techniques. In the present review, we summarize the fundamental principle of surgery of GISTs based on risk assessment as well as tumor size, location, and degree of progress with an emphasis on the indications, strengths, and limitations of current surgery techniques.

Efficacy of SCF drug conjugate targeting c-KIT in gastrointestinal stromal tumor

BACKGROUND

Gastrointestinal stromal tumor (GIST) is a rare type of cancer that occurs in the gastrointestinal tract. The majority of GIST cases carry oncogenic forms of KIT, the receptor for stem cell factor (SCF). Small molecule kinase inhibitor imatinib is effective in prolonging the survival of GIST patients by targeting KIT. However, drug resistance often develops during the therapeutic treatment. Here, we produced a SCF-emtansine drug conjugate (SCF-DM1) with favorable drug efficacy towards GIST cells.

METHODS

Recombinant human SCF (rhSCF) was expressed in E. coli cells and further purified with Ni-NTA Sepharose and Phenyl Sepharose. It was then conjugated with DM1, and the conjugated product SCF-DM1 was evaluated using in vitro cell-based assays and in vivo xenograft mouse model.

RESULTS

SCF-DM1 was effective in inhibiting imatinib-sensitive and -resistant GIST cell lines and primary tumor cells, with IC₅₀ values of < 30 nM. It induced apoptosis and cell cycle arrest in GIST cells. In xenograft mouse model, SCF-DM1 showed favorable efficacy and safety profiles.

CONCLUSIONS

rhSCF is a convenient and effective vector for drug delivery to KIT positive GIST cells. SCF-DM1 is an effective drug candidate to treat imatinib-sensitive and -resistant GIST.

Pimitespib in patients with advanced gastrointestinal stromal tumor (CHAPTER-GIST-301): a randomized, double-blind, placebo-controlled phase 3 trial

BACKGROUND

Prognosis of advanced gastrointestinal stromal tumors (GIST) refractory to tyrosine kinase inhibitors (TKIs) is poor. This randomized, placebo-controlled, phase 3 trial evaluated the efficacy and safety of pimitespib, a novel heat shock protein 90 inhibitor, in advanced GIST refractory to standard TKIs.

PATIENTS AND METHODS

Patients with histologically confirmed GIST refractory to imatinib, sunitinib, and regorafenib were randomized 2:1 to oral pimitespib 160 mg/day or placebo for five consecutive days per week in 21-day cycles. Following disease progression by blinded central radiological review (BCRR), crossover to open-label pimitespib was permitted. The primary endpoint was progression-free survival (PFS) by BCRR in the full analysis set. Secondary endpoints included overall survival (OS) adjusted using the rank preserving structural failure time method to reduce the expected confounding impact of crossover.

RESULTS

From Oct 31, 2018 to Apr 30, 2020, 86 patients were randomized to pimitespib (n=58) or placebo (n=28). Median PFS was 2.8 months (95% CI 1.6-2.9) with pimitespib versus 1.4 months (0.9-1.8) with placebo (hazard ratio [HR] 0.51 [95% CI 0.30-0.87]; one-sided p=0.006). Pimitespib showed an improvement in crossover-adjusted OS compared with placebo (HR 0.42 [0.21-0.85], one-sided p=0.007). Seventeen (60.7%) patients receiving placebo crossed-over to pimitespib; median PFS after crossover was 2.7 (95% CI 0.7-4.1) months. The most common (≥30%) treatment-related adverse events (AEs) with pimitespib were diarrhea (74.1%) and decreased appetite (31.0%); the most common (≥10%) grade ≥3 treatment-related AE was diarrhea (13.8%). Treatment-related AEs leading to pimitespib discontinuation occurred in 3 (5.2%) patients.

CONCLUSION

Pimitespib significantly improved PFS and crossover-adjusted OS compared with placebo and had an acceptable safety profile in patients with advanced GIST refractory to standard TKIs.

Switch Pocket Kinase: An Emerging Therapeutic Target for the Design of Anticancer Agents

Protein kinases are amongst the most focused enzymes in current century to design, synthesize and formulate drugs ought to be effective in the treatment of various disordered and diseased states involving either overexpression or deficiency situations. The ATP pocket on the kinases is the binding active site for most of the kinase inhibitors. However, the kinase mutations prevent the binding of kinase inhibitors to ATP pocket. The switch pocket site on this enzyme when occupied by switch pocket inhibitors, the enzyme become inactive even in the mutated state. This review comprises the detailed information on various classical protein kinases and switch pocket kinase inhibitors with their mechanism of action so that new molecules can be designed to encounter mutations in the kinase enzyme.

FOXD3 suppresses epithelial-mesenchymal transition through direct transcriptional promotion of SMAD7 in esophageal squamous cell carcinoma

The transcription factor forkhead box D3 (FOXD3) is an important member of the FOX family, which can maintain the pluripotent properties of cell clusters, neural crest, and trophoblastic progenitor cells in vivo. It has been shown that FOXD3 could affect proliferation, migration, and angiogenesis of various tumors and its deletion and overexpression in organisms will undoubtedly have important influence on the change of cell fate and the occurrence of tumors. However, the underlying functions and molecular mechanisms of FOXD3 in esophageal squamous cell carcinoma (ESCC) have not been fully clarified. According to the present study, the expression levels and functional roles of FOXD3 were investigated, and its prognostic value and molecular mechanisms in tumorigenesis and progression of ESCC were clarified. The expression level of FOXD3 was significantly downregulated in ESCC tissues and cell lines, and correlated with gender, family history of upper gastrointestinal cancer, TNM stage, depth of invasion, lymph node metastasis, and ESCC patients' survival. Moreover, FOXD3 inhibited cells migration and invasion as well as participated in TGF-β1 induced epithelial-mesenchymal transition process. Furthermore, a positive correlation between FOXD3 and SMAD family member 7 (SMAD7) was explored in ESCC. FOXD3 could directly bind to promoter regions of SMAD7 gene, leading to transcriptional promotion of SMAD7 in human esophageal cancer cells. Taken together, FOXD3 may play a tumor suppressor role in ESCC and may be applied as a new therapeutic target and prognostic marker for ESCC.

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.

Recent Progress and Challenges in the Diagnosis and Treatment of Gastrointestinal Stromal Tumors

Simple Summary

Gastrointestinal stromal tumors (GIST) are potentially malignant tumors and require evidence-based surgical and/or medical treatment. Laparoscopy has similar safety and prognostic outcomes to those of laparotomy and is currently a standard procedure for localized GISTs. However, surgery for gastric GISTs less than 2 cm may be re-evaluated due to the indolent nature of the GIST and other competing risks among GIST patients. A work-up with endoscopy and endoscopic ultrasonography as well as endoscopic or percutaneous biopsy is important for the preoperative diagnosis of GISTs. Medical treatment with tyrosine kinase inhibitors is the mainstay for recurrent/metastatic GISTs. The activity of an individual drug is well correlated with gene alterations, and, in the era of precision medicine, cancer genome profiling should be considered before medical treatment.

Abstract

Gastrointestinal stromal tumors (GISTs) are the most frequent malignant mesenchymal tumors in the gastrointestinal tract. The clinical incidence of GISTs is estimated 10/million/year; however, the true incidence is complicated by frequent findings of tiny GISTs, of which the natural history is unknown. The initial work-up with endoscopy and endoscopic ultrasonography plays important roles in the differential diagnosis of GISTs. Surgery is the only modality for the permanent cure of localized GISTs. In terms of safety and prognostic outcomes, laparoscopy is similar to laparotomy for GIST treatment, including tumors larger than 5 cm. GIST progression is driven by mutations in KIT or PDGFRA or by other rare gene alterations, all of which are mutually exclusive. Tyrosine kinase inhibitors (TKIs) are the standard therapy for metastatic/recurrent GISTs. Molecular alterations are the most reliable biomarkers for TKIs and for other drugs, such as NTRK inhibitors. The pathological and genetic diagnosis prior to treatment has been challenging; however, a newly developed endoscopic device may be useful for diagnosis. In the era of precision medicine, cancer genome profiling by targeted gene panel analysis may enable potential targeted therapy even for GISTs without KIT or PDGFRA mutations.

Long Noncoding RNA WDFY3-AS2 Represses the Progression of Esophageal Cancer through miR-18a/PTEN Axis

Background

Understanding the role of lncRNAs in the development of human malignancies is necessary for the targeted therapy of malignant tumors, including esophageal cancer (EC). Nevertheless, the specific role and regulatory mechanism of lncRNA WDFY3-AS2 in EC are still unclear. Here, we examined the functional role and regulatory mechanism of WDFY3-AS2 in EC.

Materials and Methods

RT-qPCR assay was applied to measure the expression of WDFY3-AS2 and miR-18a in EC samples and cells. The luciferase reporter and RIP assays were used to check the relationship between WDFY3-AS2, miR-18a, and PTEN. Counting Clock Kit-8 (CCK-8) assay was carried out to detect cell viability, and transwell assays were used for measuring cell migration and invasion.

Results

Underexpression of WDFY3-AS2 was found in EC specimens and cells, which predicted a poor prognosis of EC patients. Reexpression of WDFY3-AS2 repressed the progression of EC via inhibiting cell proliferation, migration, and invasion. Additionally, WDFY3-AS2 was negatively correlated with miR-18a and positively with PTEN. Furthermore, we discovered that the expression of PTEN decreased by miR-18a mimic was rescued by WDFY3-AS2 overexpression.

Conclusions

WDFY3-AS2 modulates the expressional level of PTEN as a competitive endogenous RNA via sponging miR-18a in EC, which suggests that the WDFY3-AS2/miR-18a/PTEN pathway might be involved in the progression of EC.

Emerging drugs for the treatment of gastrointestinal stromal tumors

INTRODUCTION

Oncogenic activation of KIT or PDGFRA receptor tyrosine kinases is the crucial event in gastrointestinal stromal tumor (GIST) biology. Seminal works during the past two decades have underscored, first, the continuous relevance of KIT/PDGFRA oncogenic signaling after progression to targeted inhibition; second, the heterogeneity of KIT/PDGFRA acquired mutations, that cannot be efficiently suppressed by any given tyrosine kinase inhibitor (TKI); and third, the presence of specific mutants highly resistant to all approved therapies.

AREAS COVERED

This review discusses treatment options in advanced/metastatic GIST, including a detailed dissection of ripretinib and avapritinib, the two novel small molecule inhibitors approved by the Food and Drug Administration in 2020.

EXPERT OPINION

The three only therapeutic options since 2012 for metastatic GIST patients were imatinib, sunitinib, and regorafenib. Although imatinib was highly effective in treatment-naïve GIST, the benefit of second- and third-line sunitinib and regorafenib was modest, thus emphasizing the medical need for new treatment options. Ripretinib, a switch control inhibitor with broad anti-KIT/PDGFRA activity, has been approved as ≥4th line in GIST after progression to all standard therapies. Avapritinib, a type I TKI highly specific against the multi-resistant PDGFRA D842V mutation, is approved in this specific subset of GIST patients.

HAND1 and BARX1 Act as Transcriptional and Anatomic Determinants of Malignancy in Gastrointestinal Stromal Tumor

PURPOSE

Gastrointestinal stromal tumor (GIST) arises from interstitial cells of Cajal (ICC) or their precursors, which are present throughout the gastrointestinal tract. Although gastric GIST is commonly indolent and small intestine GIST more aggressive, a molecular understanding of disease behavior would inform therapy decisions in GIST. Although a core transcription factor (TF) network is conserved across GIST, accessory TFs HAND1 and BARX1 are expressed in a disease state-specific pattern. Here, we characterize two divergent transcriptional programs maintained by HAND1 and BARX1, and evaluate their association with clinical outcomes.

EXPERIMENTAL DESIGN

We evaluated RNA sequencing and TF chromatin immunoprecipitation with sequencing in GIST samples and cultured cells for transcriptional programs associated with HAND1 and BARX1. Multiplexed tissue-based cyclic immunofluorescence and IHC evaluated tissue- and cell-level expression of TFs and their association with clinical factors.

RESULTS

We show that HAND1 is expressed in aggressive GIST, modulating KIT and core TF expression and supporting proliferative cellular programs. In contrast, BARX1 is expressed in indolent and micro-GISTs. HAND1 and BARX1 expression were superior predictors of relapse-free survival, as compared with standard risk stratification, and they predict progression-free survival on imatinib. Reflecting the developmental origins of accessory TF programs, HAND1 was expressed solely in small intestine ICCs, whereas BARX1 expression was restricted to gastric ICCs.

CONCLUSIONS

Our results define anatomic and transcriptional determinants of GIST and molecular origins of clinical phenotypes. Assessment of HAND1 and BARX1 expression in GIST may provide prognostic information and improve clinical decisions on the administration of adjuvant therapy.

Switch Control Inhibition of KIT and PDGFRA in Patients With Advanced Gastrointestinal Stromal Tumor: A Phase I Study of Ripretinib

PURPOSE

In advanced gastrointestinal stromal tumor (GIST), there is an unmet need for therapies that target both primary and secondary mutations of pathogenic KIT/PDGFRA oncoproteins. Ripretinib is a novel switch-control kinase inhibitor designed to inhibit a wide range of KIT and PDGFRA mutations.

PATIENTS AND METHODS

This first-in-human, to our knowledge, phase I study of ripretinib (ClinicalTrials.gov identifier: NCT02571036) included a dose-escalation phase and subsequent expansion phase at the recommended phase II dose (RP2D). Eligible patients included those with advanced GIST, intolerant to or experienced progression on ≥ 1 line of systemic therapy, and other advanced malignancies. Safety, dose-limiting toxicities (DLTs), maximum-tolerated dose (MTD), and preliminary antitumor activity were evaluated.

RESULTS

At data cutoff (August 31, 2019), 258 patients (n = 184 GIST) were enrolled, with 68 patients in the dose-escalation phase. Three DLTs were reported: grade 3 lipase increase (n = 2; 100 mg and 200 mg twice a day) and grade 4 increased creatine phosphokinase (n = 1; 150 mg once daily). MTD was not reached (maximum dose evaluated, 200 mg twice a day); 150 mg once daily was established as the RP2D. The most frequent (> 30%) treatment-emergent adverse events in patients with GIST receiving ripretinib 150 mg once daily (n = 142) were alopecia (n = 88 [62.0%]), fatigue (n = 78 [54.9%]), myalgia (n = 69 [48.6%]), nausea (n = 65 [45.8%]), palmar-plantar erythrodysesthesia (n = 62 [43.7%]), constipation (n = 56 [39.4%]), decreased appetite (n = 48 [33.8%]), and diarrhea (n = 47 [33.1%]). Objective response rate (confirmed) of 11.3% (n = 16/142) ranging from 7.2% (n = 6/83; fourth line or greater) to 19.4% (n = 6/31; second line) and median progression-free survival ranging from 5.5 months (fourth line or greater) to 10.7 months (second line), on the basis of investigator assessment, were observed.

CONCLUSION

Ripretinib is a well-tolerated, novel inhibitor of KIT and PDGFRA mutant kinases with promising activity in patients with refractory advanced GIST.

Ripretinib in patients with advanced gastrointestinal stromal tumours (INVICTUS): a double-blind, randomised, placebo-controlled, phase 3 trial

BACKGROUND

Resistance to approved inhibitors of KIT proto-oncogene, receptor tyrosine kinase (KIT), and platelet-derived growth factor receptor α (PDGFRA) is a clinical challenge for patients with advanced gastrointestinal stromal tumours. We compared the efficacy and safety of ripretinib, a switch-control tyrosine kinase inhibitor active against a broad spectrum of KIT and PDGFRA mutations, with placebo in patients with previously treated, advanced gastrointestinal stromal tumours.

METHODS

In this double-blind, randomised, placebo-controlled, phase 3 study, we enrolled adult patients in 29 specialised hospitals in 12 countries. We included patients aged 18 years or older who had advanced gastrointestinal stromal tumours with progression on at least imatinib, sunitinib, and regorafenib or documented intolerance to any of these treatments despite dose modifications, and who had an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. Eligible patients were randomly assigned (2:1) to receive either oral ripretinib 150 mg once daily (ripretenib group) or placebo once daily (placebo group). Randomisation was done via an interactive response system using randomly permuted block sizes of six and stratified according to number of previous therapies and ECOG performance status. Patients, investigators, research staff, and the sponsor study team were masked to a patient's treatment allocation until the blinded independent central review (BICR) showed progressive disease for the patient. The primary endpoint was progression-free survival, assessed by BICR. The primary analysis was done in the intention-to-treat population and safety was assessed in patients who received at least one dose of study drug. Patients randomly assigned to placebo were permitted to cross over to ripretinib 150 mg at the time of disease progression. The INVICTUS study is registered with ClinicalTrials.gov, number NCT03353753, and with WHO International Clinical Trials Registry Platform, number EUCTR2017-002446-76-ES; follow-up is ongoing.

FINDINGS

Between Feb 27, 2018, and Nov 16, 2018, 129 of 154 assessed patients were randomly assigned to receive either ripretinib (n=85) or placebo (n=44). At data cutoff (May 31, 2019), at a median follow-up of 6·3 months (IQR 3·2-8·2) in the ripretinib group and 1·6 months (1·1-2·7) in the placebo group, 51 patients in the ripretinib group and 37 in the placebo group had had progression-free survival events. In the double-blind period, median progression-free survival was 6·3 months (95% CI 4·6-6·9) with ripretinib compared with 1·0 months (0·9-1·7) with placebo (hazard ratio 0·15, 95% CI 0·09-0·25; p<0·0001). The most common (>2%) grade 3 or 4 treatment-related treatment-emergent adverse events in the ripretinib group (n=85) included lipase increase (four [5%]), hypertension (three [4%]), fatigue (two [2%]), and hypophosphataemia (two (2%]); in the placebo group (n=43), the most common (>2%) grade 3 or 4 treatment-related treatment-emergent adverse events were anaemia (three [7%]), fatigue (one [2%]), diarrhoea (one [2%]), decreased appetite (one [2%]), dehydration (one [2%]), hyperkalaemia (one [2%]), acute kidney injury (one [2%]), and pulmonary oedema (one [2%]). Treatment-related serious adverse events were reported in eight (9%) of 85 patients who received ripretinib and three (7%) of 43 patients who received placebo. Treatment-related deaths occurred in one patient in the placebo group (septic shock and pulmonary oedema) and one patient in the ripretinib group (cause of death unknown; the patient died during sleep).

INTERPRETATION

Ripretinib significantly improved median progression-free survival compared with placebo and had an acceptable safety profile in patients with advanced gastrointestinal stromal tumours who were resistant to approved treatments.

FUNDING

Deciphera Pharmaceuticals.

A Serosa-Originated Gastric Stromal Tumor Misdiagnosed by Ultrasonography and Frozen Section Pathology: A Case Report

Gastric gastrointestinal stromal tumor (GIST) is a mesenchymal neoplasm, typically arising from the muscularis propria layer of the stomach wall. Serosa-derived GIST is rarely seen and has not been reported yet. A 49-year-old Chinese female was presented with marked abdominal distension. Ultrasonography revealed a retroperitoneal tumor adjacent to the stomach wall with an intact structure of five echo layers, indicating a non-stomach tumor origin. Preoperative radiological studies suggested tight tumor-stomach adjacency, which was confirmed by intraoperative dissection. Initial frozen section indicated a pathological diagnosis of spindle cell tumor, which turned out to be a gastric GIST originated from the serosa layer of the stomach wall. The current case demonstrates the rare occurrence of serosa-derived GIST. This case also suggests difficulties in preoperative diagnosis of gastric GISTs, especially when uncommon pathological conditions like rare tumor origins were presented.

LINC01980 facilitates esophageal squamous cell carcinoma progression via regulation of miR-190a-5p/MYO5A pathway

Understanding the role of Long non-coding RNAs (lncRNAs) in tumorigenesis in diverse human malignancies would helpful for targeted therapies, containing esophageal squamous cell carcinoma (ESCC). However, the specific role and molecular mechanisms of LINC01980 in ESCC remain unclarified. In this study, we investigated the expression level, function role, and molecular mechanisms of LINC01980 in esophageal cancer cells and ESCC tissues. The high expression of LINC01980 was detected in ESCC tissues and cells, and predicted poor prognosis. LINC01980 promoted the cell proliferation, migration, invasion ability and epithelial-mesenchymal transition (EMT) progress in ESCC cells. In addition, a negative correlation between LINC01980 and miR-190a-5p or miR-190a-5p and MYO5A was observed in ESCC. We found that miR-190a-5p could directly bind with the mRNA of LINC01980 and MYO5A, and it was detected low expression in ESCC. We further demonstrated that the downregulation of MYO5A caused by overexpressing miR-190a-5p was released via upregulation of LINC01980. Functionally, LINC01980 acted as a competitively endogenous RNA (ceRNA) to impact the expression of MYO5A by sponging miR-190a-5p in ESCC. Therefore, these findings suggest that LINC01980 may act as an oncogenic lncRNA in ESCC and LINC01980/miR-190a-5p/MYO5A pathway contributes to the development of ESCC.

Targeted Therapies: Friends or Foes for Patient's NK Cell-Mediated Tumor Immune-Surveillance?

In the last 20 years there has been a huge increase in the number of novel drugs for cancer treatment. Most of them exploit their ability to target specific oncogenic mutations in the tumors (targeted therapies–TT), while others target the immune-checkpoint inhibitor molecules (ICI) or the epigenetic DNA modifications. Among them, TT are the longest established drugs exploited against a wide spectrum of both solid and hematological tumors, often with reasonable costs and good efficacy as compared to other innovative therapies (i.e., ICI). Although they have greatly improved the treatment of cancer patients and their survival, patients often relapse or develop drug-resistance, leading to the impossibility to eradicate the disease. The outcome of TT has been often correlated with their ability to affect not only tumor cells, but also the repertoire of immune cells and their ability to interact with cancer cells. Thus, the possibility to create novel synergies among drugs an immunotherapy prompted scientists and physicians to deeply characterize the effects of TT on immune cells both by in-vitro and by ex-vivo analyses. In this context, NK cells may represent a key issue, since they have been shown to exert a potent anti-tumor activity, both against hematological malignancies and solid tumors. In the present review we will discuss most recent ex-vivo analyses that clarify the effect of TT treatment on patient’s NK cells comparing them with clinical outcome and previous in-vitro data.

Mechanisms of resistance to a PI3K inhibitor in gastrointestinal stromal tumors: an omic approach to identify novel druggable targets

Background: Gastrointestinal stromal tumors (GISTs) represent a worldwide paradigm of target therapy. The introduction of tyrosine kinase inhibitors has deeply changed the prognosis of GIST patients, however, the majority of them acquire secondary mutations and progress. Unfortunately, besides tyrosine-kinase inhibitors, no other therapeutic options are available. Therefore, it is mandatory to identify novel molecules and/or strategies to overcome the inevitable resistance. In this context, after promising preclinical data on the novel PI3K inhibitor BYL719, the NCT01735968 trial in GIST patients who had previously failed treatment with imatinib and sunitinib started. BYL719 has attracted our attention, and we comprehensively characterized genomic and transcriptomic changes taking place during resistance.

Methods: For this purpose, we generated two in vitro GIST models of acquired resistance to BYL719 and performed an omic-based analysis by integrating RNA-sequencing, miRNA, and methylation profiles in sensitive and resistant cells.

Results: We identified novel epigenomic mechanisms of pharmacological resistance in GISTs suggesting the existence of pathways involved in drug resistance and alternatively acquired mutations. Therefore, epigenomics should be taken into account as an alternative adaptive mechanism.

Conclusion: Despite the fact that currently we do not have patients in treatment with BYL719 to verify this hypothesis, the most intriguing result is the involvement of H19 and PSTA1 in GIST resistance, which might represent druggable targets.

A Phase I Study of Binimetinib (MEK162) Combined with Pexidartinib (PLX3397) in Patients with Advanced Gastrointestinal Stromal Tumor

Lessons Learned.

The combination of pexidartinib and binimetinib was safe and tolerable and demonstrated encouraging signs of efficacy in two patients with advanced gastrointestinal stromal tumor (GIST) refractory to tyrosine kinase inhibitors (TKIs).

Molecular profiling of GISTs at diagnosis and upon progression may provide insight into the mechanisms of response or resistance to targeted therapies.

Additional trials are needed to further explore combined KIT and MEK inhibition in treatment‐naïve and TKI‐refractory patients with advanced GIST.

Background.

Nearly all patients with advanced gastrointestinal stromal tumor (GIST) develop resistance to imatinib, and subsequent treatments have limited efficacy. Dual inhibition of KIT and MAPK pathways has synergistic antitumor activity in preclinical GIST models.

Methods.

This was an investigator‐initiated, phase I, dose escalation study of the MEK inhibitor binimetinib combined with pexidartinib, a potent inhibitor of CSF1R, KIT, and FLT3, in patients with advanced or metastatic GIST who progressed on imatinib. The primary endpoint was phase II dose determination; secondary endpoints included safety, tolerability, and efficacy. An expansion cohort to further evaluate safety and efficacy was planned.

Results.

Two patients were treated at dose level one (binimetinib 30 mg b.i.d. and pexidartinib 400 mg every morning and 200 mg every evening), after which the study was terminated by the manufacturer. No dose‐limiting toxicities (DLTs) were reported, and treatment was well tolerated. The only grade ≥3 treatment‐emergent adverse event (TEAE) was asymptomatic elevated creatine phosphokinase (CPK). Both patients had a best response of stable disease (SD) by RECIST. Progression‐free survival (PFS) and overall survival (OS) were 6.1 and 14.6 months, respectively, in one patient with five prior lines of therapy. The second patient with NF1‐mutant GIST had a 27% decrease in tumor burden by RECIST and remains on study after 19 months of treatment.

Conclusion.

Pexidartinib combined with binimetinib was tolerable, and meaningful clinical activity was observed in two imatinib‐refractory patients.

Enhancer Domains in Gastrointestinal Stromal Tumor Regulate KIT Expression and Are Targetable by BET Bromodomain Inhibition

Gastrointestinal stromal tumor (GIST) is a mesenchymal neoplasm characterized by activating mutations in the related receptor tyrosine kinases KIT and PDGFRA. GIST relies on expression of these unamplified receptor tyrosine kinase (RTK) genes through a large enhancer domain, resulting in high expression levels of the oncogene required for tumor growth. Although kinase inhibition is an effective therapy for many patients with GIST, disease progression from kinase-resistant mutations is common and no other effective classes of systemic therapy exist. In this study, we identify regulatory regions of the KIT enhancer essential for KIT gene expression and GIST cell viability. Given the dependence of GIST upon enhancer-driven expression of RTKs, we hypothesized that the enhancer domains could be therapeutically targeted by a BET bromodomain inhibitor (BBI). Treatment of GIST cells with BBIs led to cell-cycle arrest, apoptosis, and cell death, with unique sensitivity in GIST cells arising from attenuation of the KIT enhancer domain and reduced KIT gene expression. BBI treatment in KIT-dependent GIST cells produced genome-wide changes in the H3K27ac enhancer landscape and gene expression program, which was also seen with direct KIT inhibition using a tyrosine kinase inhibitor (TKI). Combination treatment with BBI and TKI led to superior cytotoxic effects in vitro and in vivo, with BBI preventing tumor growth in TKI-resistant xenografts. Resistance to select BBI in GIST was attributable to drug efflux pumps. These results define a therapeutic vulnerability and clinical strategy for targeting oncogenic kinase dependency in GIST. SIGNIFICANCE: Expression and activity of mutant KIT is essential for driving the majority of GIST neoplasms, which can be therapeutically targeted using BET bromodomain inhibitors.

Enhancer Domains in Gastrointestinal Stromal Tumor Regulate KIT Expression and Are Targetable by BET Bromodomain Inhibition

Gastrointestinal stromal tumor (GIST) is a mesenchymal neoplasm characterized by activating mutations in the related receptor tyrosine kinases KIT and PDGFRA. GIST relies on expression of these unamplified receptor tyrosine kinase (RTK) genes through a large enhancer domain, resulting in high expression levels of the oncogene required for tumor growth. Although kinase inhibition is an effective therapy for many patients with GIST, disease progression from kinase-resistant mutations is common and no other effective classes of systemic therapy exist. In this study, we identify regulatory regions of the KIT enhancer essential for KIT gene expression and GIST cell viability. Given the dependence of GIST upon enhancer-driven expression of RTKs, we hypothesized that the enhancer domains could be therapeutically targeted by a BET bromodomain inhibitor (BBI). Treatment of GIST cells with BBIs led to cell-cycle arrest, apoptosis, and cell death, with unique sensitivity in GIST cells arising from attenuation of the KIT enhancer domain and reduced KIT gene expression. BBI treatment in KIT-dependent GIST cells produced genome-wide changes in the H3K27ac enhancer landscape and gene expression program, which was also seen with direct KIT inhibition using a tyrosine kinase inhibitor (TKI). Combination treatment with BBI and TKI led to superior cytotoxic effects in vitro and in vivo, with BBI preventing tumor growth in TKI-resistant xenografts. Resistance to select BBI in GIST was attributable to drug efflux pumps. These results define a therapeutic vulnerability and clinical strategy for targeting oncogenic kinase dependency in GIST. SIGNIFICANCE: Expression and activity of mutant KIT is essential for driving the majority of GIST neoplasms, which can be therapeutically targeted using BET bromodomain inhibitors.