Project description:Metabolic reprogramming is a hallmark of cancer cells in response to targeted therapy. Decreased glycolytic activity with enhanced mitochondrial respiration secondary to imatinib has been shown in imatinib-sensitive gastrointestional stromal tumors (GIST). However, the role of energy metabolism in imatinib-resistant GIST remains poorly characterized. Here, we investigated the effect of imatinib treatment on glycolysis and oxidative phosphorylation (OXPHOS), as well as the effect of inhibition of these energy metabolisms on cell viability in imatinib-resistant and -sensitive GIST cell lines. We observed that imatinib treatment increased OXPHOS in imatinib-sensitive, but not imatinib-resistant, GIST cells. Imatinib also reduced the expression of mitochondrial biogenesis activators (peroxisome proliferator-activated receptor coactivator-1 alpha (PGC1α), nuclear respiratory factor 2 (NRF2), and mitochondrial transcription factor A (TFAM)) and mitochondrial mass in imatinib-sensitive GIST cells. Lower TFAM levels were also observed in imatinib-sensitive GISTs than in tumors from untreated patients. Using the Seahorse system, we observed bioenergetics diversity among the GIST cell lines. One of the acquired resistant cell lines (GIST 882R) displayed a highly metabolically active phenotype with higher glycolysis and OXPHOS levels compared with the parental GIST 882, while the other resistant cell line (GIST T1R) had a similar basal glycolytic activity but lower mitochondrial respiration than the parental GIST T1. Further functional assays demonstrated that GIST 882R was more vulnerable to glycolysis inhibition than GIST 882, while GIST T1R was more resistant to OXPHOS inhibition than GIST T1. These findings highlight the diverse energy metabolic adaptations in GIST cells that allow them to survive upon imatinib treatment and reveal the potential of targeting the metabolism for GIST therapy.
Project description:Gastrointestinal stromal tumor (GIST) is the most common sarcoma of the gastrointestinal tract and arises from the interstitial cells of Cajal. It is characterized by expression of the receptor tyrosine kinase CD117 (KIT). In 70-80% of GIST cases, oncogenic mutations in KIT are present, leading to constitutive activation of the receptor, which drives the proliferation of these tumors. Treatment of GIST with imatinib, a small-molecule tyrosine kinase inhibitor, inhibits KIT-mediated signaling and initially results in disease control in 70-85% of patients with KIT-positive GIST. However, the vast majority of patients eventually develop resistance to imatinib treatment, leading to disease progression and posing a significant challenge in the clinical management of these tumors. Here, we show that an anti-KIT monoclonal antibody (mAb), SR1, is able to slow the growth of three human GIST cell lines in vitro. Importantly, these reductions in cell growth were equivalent between imatinib-resistant and imatinib-sensitive GIST cell lines. Treatment of GIST cell lines with SR1 reduces cell-surface KIT expression, suggesting that mAb-induced KIT down-regulation may be a mechanism by which SR1 inhibits GIST growth. Furthermore, we also show that SR1 treatment enhances phagocytosis of GIST cells by macrophages, indicating that treatment with SR1 may enhance immune cell-mediated tumor clearance. Finally, using two xenotransplantation models of imatinib-sensitive and imatinib-resistant GIST, we demonstrate that SR1 is able to strongly inhibit tumor growth in vivo. These results suggest that treatment with mAbs targeting KIT may represent an alternative, or complementary, approach for treating GIST.
Project description:The majority of gastrointestinal stromal tumors (GIST) are characterized by activating mutations of KIT, an HSP90 client protein. Further secondary resistance mutations within KIT limit clinical responses to tyrosine kinase inhibitors, such as imatinib. The dependence of KIT and its mutated forms on HSP90 suggests that HSP90 inhibition might be a valuable treatment option for GIST, which would be equally effective on imatinib-sensitive and -resistant clones. We investigated the activity of AT13387, a potent HSP90 inhibitor currently being evaluated in clinical trials, in both in vitro and in vivo GIST models. AT13387 inhibited the proliferation of imatinib-sensitive (GIST882, GIST-T1) and -resistant (GIST430, GIST48) cell lines, including those resistant to the geldanamycin analogue HSP90 inhibitor, 17-AAG. Treatment with AT13387 resulted in depletion of HSP90 client proteins, KIT and AKT, along with their phospho-forms in imatinib-sensitive and -resistant cell lines, irrespective of KIT mutation. KIT signaling was ablated, whereas HSP70, a marker of HSP90 inhibition, was induced. In vivo, antitumor activity of AT13387 was showed in both the imatinib-sensitive, GIST-PSW, xenograft model and a newly characterized imatinib-resistant, GIST430, xenograft model. Induction of HSP70, depletion of phospho-KIT and inhibition of KIT signaling were seen in tumors from both models after treatment with AT13387. A combination of imatinib and AT13387 treatment in the imatinib-resistant GIST430 model significantly enhanced tumor growth inhibition over either of the monotherapies. Importantly, the combination of AT13387 and imatinib was well tolerated. These results suggest AT13387 is an excellent candidate for clinical testing in GIST in combination with imatinib.
Project description:The increasing use of patient-administered oral anticancer drugs is paralleled by new challenges in maintaining treatment adherence. These challenges are particularly significant with adjuvant therapies for prevention of disease recurrence, where the benefits of ongoing treatment are not readily apparent to patients. Nurse practitioners and physician assistants (collectively referred to as advanced practitioners) play integral roles in providing education on disease and treatment to patients that can increase adherence to oral therapies and ideally improve outcomes. For patients with gastrointestinal stromal tumor (GIST), the oral targeted therapy imatinib has become the mainstay of treatment for advanced and recurrent disease and as adjuvant therapy following surgical resection. Recent data indicate significantly improved overall survival with 3 years vs. 1 year of adjuvant imatinib therapy. Continuous dosing with imatinib is needed for optimal efficacy and to limit additional health-care costs associated with management of disease progression in GIST. However, longer duration of therapy increases the risk of nonadherence. Imatinib adherence rates, as well as factors contributing to nonadherence to adjuvant therapy in routine clinical practice, are discussed in this review. Also explored are practical approaches for improving adherence to adjuvant imatinib therapy through greater patient education, in light of the increased duration of therapy in select patients.
Project description:Emerging evidence has shown that long non-coding RNAs (lncRNAs) play crucial roles in human cancers. However, systematic characterization of lncRNAs and their roles in gastrointestinal stromal tumor (GIST) therapy have been lacking. We performed high-throughput RNA sequencing (RNA-seq) of 20 GIST and paired adjacent normal samples. We characterized the transcriptional landscape and dysregulation of lncRNAs in GIST. We identified 866 upregulated and 1,268 downregulated lncRNAs in GIST samples, the majority of which were GIST-specific over other cancer types. Most hallmarks were found to be dysregulated in GIST samples, and lncRNAs were highly associated with cancer-related hallmarks. RP11-616M22.7 was identified to increase in imatinib-resistant samples compared to those in non-resistant samples. Further analysis revealed that RP11-616M22.7 was closely associated with the Hippo signaling pathway. By treating GIST cells with different doses of imatinib, we verified that RP11-616M22.7 knockdown promotes the sensitivity of tumor cells, whereas RP11-616M22.7 overexpression induces resistance to imatinib. We further confirmed reducing of resistance to imatinib by knocking down RP11-616M22.7 in vivo. Additionally, RP11-616M22.7 was observed to interact with RASSF1 protein. Our study revealed that deficiency of RP11-616M22.7 was able to reduce resistance of the GIST cell response to imatinib treatment both in vitro and in vivo.
Project description:Although imatinib mesylate (IM) has transformed the treatment of gastrointestinal stromal tumors (GIST), many patients experience primary/secondary drug resistance. In a previous study, we identified a gene signature, consisting mainly of Kruppel-associated box (KRAB) domain containing zinc finger (ZNF) transcriptional repressors that predict short-term response to IM. To determine if these genes have functional significance, a siRNA library targeting these genes was constructed and applied to GIST cells in vitro. These screens identified seventeen "IM sensitizing genes" in GIST cells (sensitization index (SI) <0.85 ratio of drug/vehicle) with a false discovery rate (FDR) <15%, including twelve ZNF genes, the majority of which are located within the HSA19p12-13.1 locus. These genes were shown to be highly specific to IM and another tyrosine kinase inhibitor (TKI), sunitinib, in GIST cells. In order to determine mechanistically how these ZNFs might be modulating response to IM, RNAi approaches were used to individually silence genes within the predictive signature in GIST cells and expression profiling was performed. Knockdown of the 14 IM-sensitizing genes (10 ZNFs) universally led to downregulation of six genes, including TGFb3, periostin, and NEDD9. These studies implicate a role of KRAB-ZNFs in modulating response to TKIs in GIST.
Project description:BackgroundThe effect of neoadjuvant therapy (NAT) with imatinib versus upfront resection (UR) followed by adjuvant therapy (AT) with imatinib on the outcomes of gastrointestinal stromal tumors (GIST) is unknown.MethodsThis is a retrospective study at a high-volume center. All the patients with primary localized GIST were identified in a hospital database from 2007 to 2021. The endpoints included local recurrence-free survival (LRFS), distance recurrence-free survival (DRFS), and overall survival (OS). Cox regression was used to perform multivariate survival analyses. The sensitivity analysis was conducted with the inverse probability of treatment weighting (IPTW) method.ResultsA total of 211 patients were included (Group A: UR + AT, n=140; Group B: NAT + resection + AT, n=71). In the entire cohort, 5-year DRFS, LRFS, and OS were 85.6%, 90.7%, and 92.5%, respectively. In the multivariate analysis, better DRFS was linked to NAT, tumor size of 5 cm, and AT. Sixteen patients (11.4%) in Group A and 1 (1.4%) in Group B had distant recurrences after AT discontinuation. The sensitivity analysis by IPTW provided approximately similar results. An interaction effect was observed between NAT and tumor location on DRFS. In non-gastric GISTs, NAT was associated with better DRFS [hazard ratio =0.131, 95% confidence interval (CI): 0.017-0.989, P=0.049], which was not the case in gastric GIST (P=0.08). NAT was not independently associated with LRFS or OS.ConclusionsWhen compared to UR + AT, NAT + resection + AT may reduce the risk of distant recurrence in localized GIST and may be especially beneficial for patients with non-gastric GISTs.
Project description:Despite the introduction of tyrosine kinase inhibitors, gastrointestinal stromal tumors (GIST) resistance remains a major clinical challenge. We previously identified phosphodiesterase 3A (PDE3A) as a potential therapeutic target expressed in most GIST. The PDE3 inhibitor cilostazol reduced cell viability and synergized with the tyrosine kinase inhibitor imatinib (Gleevec™) in the imatinib-sensitive GIST882 cell line. Here, we found that cilostazol potentiated imatinib also in the imatinib-resistant GIST48 cell line. Cilostazol induced nuclear exclusion, hence inactivation, of the transcriptional co-activator YAP, in a cAMP-independent manner. Verteporfin, a YAP/TEAD interaction inhibitor, reduced by 90% the viability of both GIST882 and GIST48 cells. Our results highlight the potential use of compounds targeting PDE3A or YAP in combined multitherapy to tackle GIST resistance.
Project description:BackgroundThe potential correlation between KIT secondary mutations and Imatinib-resistance in gastrointestinal stromal tumor (GIST) has been hinted, yet their specific linkage and underlying mechanisms remained unelucidated, also the development of substitute strategies dealing with this resistance was urgently needed.MethodsIn this study, we explored the distribution of the most prevalent forms of KIT mutation in Chinese GIST patients, after that, we established cell lines that was overexpressed with mutant KIT, and by performing RNA sequencing, immunoblotting and cell viability, we analyzed their functional and mechanistic relevance with Imatinib-resistance in GIST cell lines. Additionally, we evaluated the tumor inhibition efficacy of four regimens in Imatinib-resistant GIST cell lines and patient-derived xenograft (PDX) models.ResultsWe found that KIT exon 13-V654A and exon 17-N822K were the most common secondary mutations in GIST with primary exon 11 mutations. These two secondary mutations induced Imatinib resistance by activating PI3K-Akt signaling pathway, while PI3K-Akt inhibition rescued the resistance. By assessing the feasibility of other four tyrosine kinase inhibitor (TKIs, Sunitinib/Regorafenib/Avapritinib/Ripretinib) against Imatinib-resistant GIST, we found that Sunitinib was more suitable for KIT exon 13 secondary mutations, the rest were more effective for KIT exon 17 secondary mutations, while all four TKIs displayed efficacy for KIT exon 9 mutations, emphasizing their clinical applications against Imatinib resistance.ConclusionsWe demonstrated the mechanism by which KIT secondary mutations on exon 13/17 cause Imatinib resistance to GIST, and validated that several novel TKIs were valuable therapeutic options against Imatinib-resistance for both secondary- and primary-KIT mutations.
Project description:Gastrointestinal stromal tumor (GIST) is commonly driven by oncogenic KIT mutations that are effectively targeted by imatinib (IM), a tyrosine kinase inhibitor (TKI). However, IM does not cure GIST, and adjuvant therapy only delays recurrence in high-risk tumors. We hypothesized that GIST contains cells with primary IM resistance that may represent a reservoir for disease persistence. Here, we report a subpopulation of CD34+KITlow human GIST cells that have intrinsic IM resistance. These cells possess cancer stem cell-like expression profiles and behavior, including self-renewal and differentiation into CD34+KIThigh progeny that are sensitive to IM treatment. We also found that TKI treatment of GIST cell lines led to induction of stem cell-associated transcription factors (OCT4 and NANOG) and concomitant enrichment of the CD34+KITlow cell population. Using a data-driven approach, we constructed a transcriptomic-oncogenic map (Onco-GPS) based on the gene expression of 134 GIST samples to define pathway activation during GIST tumorigenesis. Tumors with low KIT expression had overexpression of cancer stem cell gene signatures consistent with our in vitro findings. Additionally, these tumors had activation of the Gas6/AXL pathway and NF-κB signaling gene signatures. We evaluated these targets in vitro and found that primary IM-resistant GIST cells were effectively targeted with either single-agent bemcentinib (AXL inhibitor) or bardoxolone (NF-κB inhibitor), as well as with either agent in combination with IM. Collectively, these findings suggest that CD34+KITlow cells represent a distinct, but targetable, subpopulation in human GIST that may represent a novel mechanism of primary TKI resistance, as well as a target for overcoming disease persistence following TKI therapy.