Gastrointestinal Stromal Tumors Cells Research Articles

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.

Concurrent inhibition of CDK2 adds to the anti-tumour activity of CDK4/6 inhibition in GIST.

Advanced gastrointestinal stromal tumour (GIST) is characterised by genomic perturbations of key cellcycle regulators. Oncogenic activation of CDK4/6 results in RB1 inactivation and cell cycle progression. Given that single-agent CDK4/6 inhibitor therapy failed to show clinical activity in advanced GIST, we evaluated strategies for maximising response to therapeutic CDK4/6 inhibition. Targeted next-generation sequencing and multiplexed protein imaging were used to detect cellcycle regulator aberrations in GIST clinical samples. The impact of inhibitors of CDK2, CDK4 and CDK2/4/6 was determined through cellproliferation and proteindetection assays. CDK-inhibitor resistance mechanisms were characterised in GIST cell lines after long-term exposure. We identify recurrent genomic aberrations in cellcycle regulators causing co-activation of the CDK2 and CDK4/6 pathways in clinical GIST samples. Therapeutic co-targeting of CDK2 and CDK4/6 is synergistic in GIST cell lines with intact RB1, through inhibition of RB1 hyperphosphorylation and cell proliferation. Moreover, RB1 inactivation and a novel oncogenic cyclin D1 resulting from an intragenic rearrangement (CCND1::chr11.g:70025223) are mechanisms of acquired CDK-inhibitor resistance in GIST. These studies establish the biological rationale for CDK2 and CDK4/6 co-inhibition as a therapeutic strategy in patients with advanced GIST, including metastatic GIST progressing on tyrosine kinase inhibitors.

Circ-CCS enhances autophagy during imatinib resistance of gastrointestinal stromal tumor by regulating miR-197-3p/ATG10 signaling.

Drug resistance in gastrointestinal stromal tumors (GISTs) is connected with autophagy activation. Accumulating data demonstrates the critical role of circular RNAs (circRNAs) dysregulation in this development. To explore the possible function of hsa_circ_0092306 (circ-CCS) in GIST imatinib resistance. Quantitative real-time reverse transcription PCR (RT-qPCR) was used to determine the expression levels of circ-CCS and miR-197-3p. The vitality and apoptosis of cells were determined using the Cell Counting Kit-8 and TUNEL assays, respectively. Western blot analysis was used to evaluate the relative protein expression. A dual-luciferase reporter assay was used to validate the link between circ-CCS, miR-197-3p, and ATG10. Comparisons of two groups were analyzed using Student's t tests, and analysis of variance (ANOVA) with Tukey's post hoc test was used to compare three or more groups. Circulating-CCS expression was considerably increased in the serum of imatinib-resistant GIST patients (P < 0.001). Circulating-CCS deficiency decreased cell proliferation and autophagy in GIST-882 and GIST-T1 cells, but promoted apoptosis (P < 0.05). Additionally, circ-CCS was predominantly found in the cytoplasm. Mechanically, circ-CCS targeted miR-197-3p, which may influence autophagy by downregulating ATG10, in order to modulate GIST cells' malignant tendencies. Moreover, silencing miR-197-3p reversed the effect of circ-CCS knockdown on apoptosis and autophagy in GIST cells. By modulating the miR-197-3p/ATG10 axis, circ-CCS increased imatinib resistance in GIST cells, establishing a potential target for reversing medication resistance in such patients.

1489MO A phase Ib/II study of selinexor as single agent and in combination with imatinib in patients with advanced gastrointestinal stromal tumor (GIST): SeliGIST/GEIS-41 trial

Currently approved agents in metastatic GIST focus on targeted suppression of KIT or PDGFRA oncogenic activation. However, their clinical benefit after imatinib (IM) progression is still modest, suggesting the co-operation of KIT/PDGFRA-independent mechanisms in GIST cell survival. Selinexor is an oral, selective inhibitor of XPO1-mediated nuclear export, and preclinical studies evidenced antitumoral activity in GIST as single agent and in combination with IM in both IM-sensitive and IM-resistant models.

Methyltransferase-like 3 (METTL3) mediated N6-methyladenosine (m6A) modifications facilitate mir-25-3p maturation to promote gastrointestinal stromal tumors (GISTs) progression.

Methyltransferase-like 3 (METTL3) is an RNA N6-methyladenosine (m6A) methyltransferase, which plays a critical role in micorRNA (miRNAs) processing and maturation, but it is still unclear whether METTL3 regulated miRNAs participates in the regulation of cancer aggressiveness in gastrointestinal stromal tumors (GISTs). This study was designed to investigate this issue, and uncover the potential underlying mechanisms. the expression of METTL3 in GISTs tissues and cell lines were determined by RT-qPCR and Western blot. Cell proliferation and migration were assessed by colony formation, CCK-8 and Transwell. The mRNA expression of all proteins was detected by RT-qPCR, and tumor xenograft study was applied to confirm the effect of METTL3 on GISTs development in vivo. In our study, we showed that METTL3 was significantly upregulated in GISTs tissues and cell lines. Functional experiments demonstrated that overexpression of METTL3 promoted GISTs cell malignant biological behavior and tumor growth in vitro and in vivo, and conversely, silencing of METTL3 had opposite effects and suppressed GISTs progression. Further mechanistical experiments verified that METTL3 promoted the maturation of miR-25-3p in an m6A-dependent manner. Similar to METTL3, miR-25-3p was also validated as an oncogene to promote cancer development in GISTs. Finally, our rescuing experiments hinted that silencing of miR-25-3p abrogated the tumor-initiating effects of METTL3 overexpression on GISTs. Collectively, those results indicated that METTL3 played an oncogenic role in GISTs through positively modulating the miR-25-3p in an m6A-dependent manner, and we firstly discussed how the METTL3/m6A/miR-25-3p axis affected GISTs development.

SPK1/S1P axis confers gastrointestinal stromal tumors (GISTs) resistance of imatinib.

BackgroundImatinib mesylate (IM) is highly effective in the treatment of gastrointestinal stromal tumors (GISTs). However, the most of GISTs patients develop secondary drug resistance after 1–3 years of IM treatment. The aim of this study was to explore the IM-resistance mechanism via the multi-scope combined with plasma concentration of IM, genetic polymorphisms and plasma sensitive metabolites.MethodsThis study included a total of 40 GISTs patients who had been regularly treated and not treated with IM. The plasma samples were divided into three experiments, containing therapeutic drug monitoring (TDM), OCT1 genetic polymorphisms and non-targeted metabolomics. According to the data of above three experiments, the IM-resistant cell line, GIST-T1/IMR cells, was constructed for verification the IM-resistance mechanism.ResultsThe results of non-targeted metabolomics analysis suggested that the sphingophospholipid metabolic pathway including the SPK1/S1P axis was inferred in IM-insensitive patients with GISTs. A GIST cell line (GIST-T1) was immediately induced as an IM resistance cell model (GIST-T1/IMR) and we found that blocking the signal pathway of SPK1/S1P in the GIST-T1/IMR could sensitize treatment of IM and reverse the IM-resistance.ConclusionsOur findings suggest that IM secondary resistance is associated with the elevation of S1P, and blockage the signaling pathway of SPK1/S1P warrants evaluation as a potential therapeutic strategy in IM-resistant GISTs.Graphical abstractThe design of this study from blood management, group information collection, IM plasma concentration with different elements, identification of sphingolipid metabolism and lastly verification the function of SPK1/S1P in the IM-resistance GISTs cells. Supplementary InformationThe online version contains supplementary material available at 10.1007/s10120-022-01332-7.

Expression of Concern: "Neferine inhibits growth and migration of gastrointestinal stromal tumor cell line GIST-T1 by up-regulation of miR-449a" [Biomed. Pharmacother. 109 (2019) 1951-1959

Expression of Concern: "Neferine inhibits growth and migration of gastrointestinal stromal tumor cell line GIST-T1 by up-regulation of miR-449a" [Biomed. Pharmacother. 109 (2019) 1951-1959

SMYD2 aggravates gastrointestinal stromal tumor via upregulation of EZH2 and downregulation of TET1

SMYD2, as an oncogene, has been involved in multiple types of cancer, but the potential role of SMYD2 in gastrointestinal stromal tumors (GIST) remains enigmatic and requires further investigation. Hence, this study was conducted with the main objective of analyzing the effect of SMYD2 on GIST. GIST and adjacent normal tissues were collected from 46 patients with GIST where the expression of EZH2, SMYD2, and TET1 was determined, followed by the analysis of their interactions. The functional role of SMYD2 in cell biological functions was determined using a loss-of-function assay in GIST-T1 cells. Nude mouse xenograft experiments were performed to verify the role of the SMYD2/EZH2/TET1 axis in GIST in vivo. EZH2 was upregulated in GIST tissues and cell lines, which was positively correlated with SMYD2 expression and inversely correlated with TET1 expression in GIST tissues. EZH2 silencing due to SMYD2 inhibition reduced GIST-T1 cell proliferation and accelerated cell senescence. EZH2 repressed TET1 expression by promoting H3K27me3 methylation in the TET1 promoter region. TET1 inhibition reversed the effect of EZH2 silencing on the biological functions of GIST-T1 cells. In vivo data further revealed the promoting effect of SMYD2 on the progression of GIST by regulating the EZH2/TET1 axis. Overall, this study demonstrates that SMYD2 can increase EZH2 expression while suppressing TET1 expression, thus accelerating GIST, and creating new treatment opportunities for GIST.

N6-methyladenosine modification regulates imatinib resistance of gastrointestinal stromal tumor by enhancing the expression of multidrug transporter MRP1.

N6-methyladenosine (m6A) is a frequently occurring mRNA modification, which regulates mRNA stability, splicing, and translation. However, its role in drug resistance of gastrointestinal stromal tumor (GIST) is not known. Here, we report that m6A modification levels are elevated in imatinib-resistant GIST cells and tissues, and that methyltransferase METTL3 is one of the main protein responsible for this aberrant modification. Increased METTL3 levels contributed to imatinib resistance and worse progression-free survival of GIST patients. Mechanistic studies revealed that METTL3-mediated m6A modification of the 5'UTR of the multidrug transporter MRP1 mRNA promoted drug resistance of GIST by stimulating MRP1 mRNA translation, via binding with YTHDF1 and eEF-1. Further, METTL3 transcription in imatinib resistant GIST cells was activated by ETV1, leading to the increased m6A methylation of MRP1 mRNA. This is the first report showing a novel regulatory mechanism whereby ETV1, METTL3, and the YTHDF1/eEF-1 complex mediate the translation of MRP1 mRNA in an m6A-dependent manner to regulate the intracellular concentration of imatinib and drug resistance of GIST. These findings highlight MRP1 as a new potential therapeutic target for imatinib resistance of GIST.

CTCF-activated SNHG16 facilitates gastrointestinal stromal tumor by targeting miR-128-3p/CASC3 axis

In this study, it was ascertained that SNHG16 was up-regulated in gastrointestinal stromal tumor (GIST) tissues and cells, and was responsible for the aggravated malignant behaviors of GIST cells. CTCF served as a transcription activator responsible for the overexpression of SNHG16 in GIST cells. MiR-128-3p was negatively regulated by SNHG16 and exerted anti-tumor effects. Moreover, CASC3 was the direct target mRNA of miR-128-3p, through which miR-128-3p exerted function influence on GIST cell malignant behaviors. SNHG16 competitively bound with miR-128-3p against CASC3, thus positively regulating CASC3 expression. Finally, functional assays carried out in vitro proved SNHG16 could modulate GIST cell proliferation, migration, invasion and apoptosis via miR-128-3p/CASC3 axis. Animal experiments were also designed and implemented in a rescue way and evidenced that up-regulation of CASC3 countervailed the inhibitory impacts of SNHG16 silence on the progression of GIST. In summary, SNHG16 up-regulated by CTCF facilitated the progression of GIST through miR-128-3p/CASC3.

Infigratinib (BGJ 398), a Pan-FGFR Inhibitor, Targets P-Glycoprotein and Increases Chemotherapeutic-Induced Mortality of Multidrug-Resistant Tumor Cells.

The microtubule-targeting agents (MTAs) are well-known chemotherapeutic agents commonly used for therapy of a broad spectrum of human malignancies, exhibiting epithelial origin, including breast, lung, and prostate cancer. Despite the impressive response rates shortly after initiation of MTA-based therapy, the vast majority of human malignancies develop resistance to MTAs due to the different mechanisms. Here, we report that infigratinib (BGJ 398), a potent FGFR1-4 inhibitor, restores sensitivity of a broad spectrum of ABCB1-overexpressing cancer cells to certain chemotherapeutic agents, including paclitaxel (PTX) and doxorubicin (Dox). This was evidenced for the triple-negative breast cancer (TNBC), and gastrointestinal stromal tumor (GIST) cell lines, as well. Indeed, when MDR-overexpressing cancer cells were treated with a combination of BGJ 398 and PTX (or Dox), we observed a significant increase of apoptosis which was evidenced by an increased expression of cleaved forms of PARP, caspase-3, and increased numbers of Annexin V-positive cells, as well. Moreover, BGJ 398 used in combination with PTX significantly decreased the viability and proliferation of the resistant cancer cells. As expected, no apoptosis was found in ABCB1-overexpressing cancer cells treated with PTX, Dox, or BGJ 398 alone. Inhibition of FGFR-signaling by BGJ 398 was evidenced by the decreased expression of phosphorylated (i.e., activated) forms of FGFR and FRS-2, a well-known adaptor protein of FGFR signaling, and downstream signaling molecules (e.g., STAT-1, -3, and S6). In contrast, expression of MDR-related ABC-transporters did not change after BGJ 398 treatment, thereby suggesting an impaired function of MDR-related ABC-transporters. By using the fluorescent-labeled chemotherapeutic agent PTX-Alexa488 (Flutax-2) and doxorubicin, exhibiting an intrinsic fluorescence, we found that BGJ 398 substantially impairs their efflux from MDR-overexpressing TNBC cells. Moreover, the efflux of Calcein AM, a well-known substrate for ABCB1, was also significantly impaired in BGJ 398-treated cancer cells, thereby suggesting the ABCB1 as a novel molecular target for BGJ 398. Of note, PD 173074, a potent FGFR1 and VEGFR2 inhibitor failed to retain chemotherapeutic agents inside ABCB1-overexpressing cells. This was consistent with the inability of PD 173074 to sensitize Tx-R cancer cells to PTX and Dox. Collectively, we show here for the first time that BGJ 398 reverses the sensitivity of MDR-overexpressing cancer cells to certain chemotherapeutic agents due to inhibition of their efflux from cancer cells via ABCB1-mediated mechanism.

The KDM6A-SPARCL1 axis blocks metastasis and regulates the tumour microenvironment of gastrointestinal stromal tumours by inhibiting the nuclear translocation of p65.

It is urgent to explore the pathogenic mechanism of gastrointestinal stromal tumours (GISTs). KDM6A, a histone demethylase, can activate gene transcription and has not been reported in GISTs. SPARCL1 may serve as a metastasis marker in GIST, but the molecular mechanism remains to be further explored. This study aimed to explore the biological function and molecular mechanism of KDM6A and SPARCL1 in GIST. CCK-8, live cell count, colony formation, wound-healing and Transwell migration and invasion assays were employed to detect the cell proliferation, migration and invasion. A xenograft model and hepatic metastasis model were used to assess the role of KDM6A and SPARCL1 in vivo. KDM6A inhibited the proliferation, migration and invasion of GIST cells. Mechanistically, KDM6A promotes the transcription of SPARCL1 by demethylating histone H3 lysine trimethylation and consequently leads to the inactivation of p65. SPARCL1 affected the metastasis of GIST cells in a mesenchymal-epithelial transition- and matrix-metalloproteinase-dependent manner. SPARCL1 knockdown promoted angiogenesis, M2 polarisation and macrophage recruitment by inhibiting the phosphorylation of p65. Moreover, KDM6A and SPARCL1 inhibited hepatic metastasis and macrophage infiltration in vivo. Our findings establish the critical role of the KDM6A-SPARCL1-p65 axis in restraining the malignancy of GIST.

CADM1 promotes adhesion to vascular endothelial cells and transendothelial migration in cultured GIST cells.

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the human gastrointestinal tract. Small intestinal GISTs appear to be associated with poorer prognosis and higher metastasis rate than gastric GISTs of the same size and mitotic index. Recently, we reported that cell adhesion molecule 1 (CADM1) is expressed specifically in most small intestinal GISTs, but not in most gastric GISTs, suggesting that this difference in CADM1 expression between gastric GISTs and small intestinal GISTs might influence the difference in clinical behavior between them. The aim of the present study was to examine whether high CADM1 expression affected proliferation, migration, invasion, adhesion to endothelial cells and transendothelial migration of cultured GIST cells by comparing original GIST-T1 cells with very low CADM1 expression with GIST-T1 cells with high CADM1 expression induced by CADM1 cDNA transfection (GIST-T1-CAD cells). GIST-T1-CAD cells had reduced ability to proliferate, migrate and invade compared with the original GIST-T1 cells, but showed significantly higher ability to adhere to human umbilical vein endothelial cells and migrate through endothelial cell monolayers. Thus, CADM1 may contribute to higher metastasis rates in small intestinal GISTs facilitating tumor cell adhesion to vascular endothelial cell and transendothelial migration of tumor cells. CADM1 might serve as a potential target for inhibition of metastasis in small intestinal GISTs.

Fibrinogen-like protein 2 in gastrointestinal stromal tumour.

Gastrointestinal stromal tumour (GIST), the most common sarcoma of the gastrointestinal tract, can be treated effectively with tyrosine kinase inhibitors, such as imatinib. Cancer immune therapy has limited efficacy, and little is known about the immune suppressive factors in GISTs. Fibrinogen‐like protein 2 (FGL2) is expressed either as a membrane‐associated protein or as a secreted soluble protein that has immune suppressive functions. We found that GISTs expressed FGL2 mRNA highly compared to other types of cancer in a large human cancer transcriptome database. GIST expressed FGL2 frequently also when studied using immunohistochemistry in two large clinical series, where 333 (78%) out of the 425 GISTs were FGL2 positive. The interstitial cells of Cajal, from which GISTs may originate, expressed FGL2. FGL2 expression was associated with small GIST size, low mitotic counts and low tumour‐infiltrating lymphocyte (TIL) counts. Patients whose GIST expressed FGL2 had better recurrence‐free survival than patients whose GIST lacked expression. Imatinib upregulated FGL2 in GIST cell lines, and the patients with FGL2‐negative GIST appeared to benefit most from long duration of adjuvant imatinib. We conclude that GISTs express FGL2 frequently and that FGL2 expression is associated with low TIL counts and favourable survival outcomes.

Glucose transporter‑1 inhibition overcomes imatinib resistance in gastrointestinal stromal tumor cells.

Imatinib mesylate (imatinib) is the primary agent of choice used to treat gastrointestinal stromal tumors (GIST). However, drug resistance to imatinib poses a major obstacle to treatment efficacy. In addition, the relationship between imatinib resistance and glycolysis is poorly understood. Glucose transporter (GLUT)-1 is a key component of glycolysis. The present study aimed to assess the potential relationship between components in the glycolytic pathway and the acquisition of imatinib resistance by GIST cells, with particular focus on GLUT-1. An imatinib-resistant GIST cell line was established through the gradual and continuous imatinib treatment of the parental human GIST cell line GIST-T1. The expression of glycolysis-related molecules (GLUT-1, hexokinase 2, pyruvate kinase M2 and lactate dehydrogenase) was assessed in parental and imatinib-resistant cells by western blotting, reverse transcription-quantitative PCR and glucose and lactate measurement kits. In addition, clinical information and transcriptomic data obtained from the gene expression omnibus database (GSE15966) were used to confirm the in vitro results. The potential effects of GLUT-1 inhibition on the expression of proteins in the glycolysis (GLUT-1, hexokinase 2, pyruvate kinase M2 and lactate dehydrogenase) and apoptosis pathways (Bcl-2, cleaved PARP, caspase-3 and caspase-9) in imatinib-resistant cells were then investigated following gene silencing and treatment using the GLUT-1 inhibitor WZB117 by western blotting. For gene silencing, the mature siRNAs for SLC2A1 were used for cell transfection. Annexin V-FITC/PI double-staining followed by flow cytometry was used to measure apoptosis whereas three-dimensional culture experiments were used to create three-dimensional spheroid cells where cell viability and spheroid diameter were measured. Although imatinib treatment downregulated GLUT-1 expression and other glycolysis pathway components hexokinase 2, pyruvate kinase M2, and lactate dehydrogenase in parental GIST-T1 cells even at low concentrations. By contrast, expression of these glycolysis pathway components in imatinib-resistant cells were increased by imatinib treatment. WZB117 administration significantly downregulated AKT phosphorylation and Bcl-2 expression in imatinib-resistant cells, whereas the combined administration of imatinib and WZB117 conferred synergistic growth inhibition effects in apoptosis assay. WZB117 was found to exert additional inhibitory effects by inducing apoptosis in imatinib-resistant cells. Therefore, the present study suggests that GLUT-1 is involved in the acquisition of imatinib resistance by GIST cells, which can be overcome by combined treatment with WZB117 and imatinib.

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.

Targeted therapy for drug-tolerant persister cells after imatinib treatment for gastrointestinal stromal tumours.

Despite the effectiveness of tyrosine kinase inhibitors (TKI), gastrointestinal stromal tumours (GIST) develop after the withdrawal of TKI. Based on previous studies, a subpopulation of drug-tolerant cells called "persister cells" may be responsible for the recurrence and have thus, gained attention as a novel target in cancer therapy. The metabolic changes were investigated in imatinib-derived persister GIST cells. We investigated the efficacy and the mechanism of GPX4 inhibitor, which is known as a major inducer of "ferroptosis". We also evaluated the effects of RSL3 to the gefitinib-derived persister lung cancer cells. We demonstrated a downregulation of glucose metabolism, subsequent decrease in the glutathione level and sensitivity to glutathione peroxidase 4 (GPX4) inhibitor, RSL3 in persister cells. As the cell death induced by RSL3 was found to be "iron-dependent" and "caspase-independent", loss of GPX4 function could have possibly induced selective persister cell ferroptotic death. In the xenograft model, we confirmed the inhibition of tumour regrowth after discontinuation of imatinib treatment. Moreover, RSL3 prevented the growth of gefitinib-derived persister lung cancer cells. RSL3 combined with TKI may be a promising therapy for both GIST and epidermal growth factor receptor-mutated lung cancer.

A novel anti-c-Kit antibody-drug conjugate to treat wild-type and activating-mutant c-Kit-positive tumors.

c‐Kit overexpression and activating mutations, which are reported in various cancers, including gastrointestinal stromal tumor (GIST), small‐cell lung cancer (SCLC), acute myeloid leukemia, acral melanoma, and systemic mastocytosis (SM), confer resistance to tyrosine kinase inhibitors (TKIs). To overcome TKI resistance, an anti‐c‐Kit antibody–drug conjugate was developed in this study to treat wild‐type and mutant c‐Kit‐positive cancers. NN2101, a fully human IgG1, was conjugated to DM1, a microtubule inhibitor, through N‐succinimidyl‐4‐(N‐maleimidomethyl) cyclohexane‐1‐carboxylate (SMCC) (to give NN2101‐DM1). The antitumor activity of NN2101‐DM1 was evaluated in vitro and in vivo using various cancer cell lines. NN2101‐DM1 exhibited potent growth‐inhibitory activities against c‐Kit‐positive cancer cell lines. In a mouse xenograft model, NN2101‐DM1 exhibited potent growth‐inhibitory activities against imatinib‐resistant GIST and SM cells. In addition, NN2101‐DM1 exhibited a significantly higher anti‐cancer effect than carboplatin/etoposide against SCLC cells where c‐Kit does not mediate cancer pathogenesis. Furthermore, the combination of NN2101‐DM1 with imatinib in imatinib‐sensitive GIST cells induced complete remission compared with treatment with NN2101‐DM1 or imatinib alone in mouse xenograft models. These results suggest that NN2101‐DM1 is a potential therapeutic agent for wild‐type and mutant c‐Kit‐positive cancers.

Effect of Long Non-Coding RNA AOC4P on Gastrointestinal Stromal Tumor Cells [Retraction

[This retracts the article DOI: 10.2147/OTT.S174524.].

Inhibition of PI3K and MAPK pathways along with KIT inhibitors as a strategy to overcome drug resistance in gastrointestinal stromal tumors.

Activating mutations in KIT/PDGFRA receptor tyrosine kinases drive gastrointestinal stromal tumors (GIST). KIT/PDGFRA inhibitors, such as imatinib do not evoke an effective cytocidal response, leaving room for quiescence and development of multiple secondary resistance mutations. As the majority of the secondary resistance clones activate PI3K and MAPK pathways, we investigated whether combined targeting of KIT/PI3K/MAPK (KPM) pathways overcomes drug resistance and quiescence in GIST cells. We monitored the proliferation of imatinib–sensitive and–resistant GIST cell lines after treating them with various combinations of drugs to inhibit KPM pathways. Cytocidal response was evaluated through proliferation, apoptosis and colony outgrowth assays. Combined inhibition of KPM signaling pathways using a KPM inhibitor cocktail decreased the survival of drug-resistant GIST cells and dramatically reduced their proliferation. Downstream pathway analysis showed that the residual PI3K/MAPK signaling observed after KIT inhibitor treatment plays a role in mediating quiescence and drug resistance. The KPM inhibitor cocktail with sunitinib or regorafenib effectively induced apoptosis and prevented colony outgrowth after long-term drug removal, suggesting that it can be used as an effective strategy against quiescence and drug resistance in metastatic GIST.