Downsizing treatment with tyrosine kinase inhibitors in patients with advanced gastrointestinal stromal tumors improved resectability.
ABSTRACT: Gastrointestinal stromal tumors (GISTs) express the receptor tyrosine kinase KIT. Most GISTs have mutations in the KIT or PDGFRA gene, causing activation of tyrosine kinase. Imatinib, a tyrosine kinase inhibitor (TKI), is the first-line palliative treatment for advanced GISTs. Sunitinib was introduced for patients with mutations not responsive to imatinib. The aim was to compare the survival of patients with high-risk resected GISTs treated with TKI prior to surgery with historical controls and to determine if organ-preserving surgery was facilitated.Ten high-risk GIST-patients had downsizing/adjuvant TKI treatment: nine with imatinib and one with sunitinib. The patients were matched with historical controls (n = 89) treated with surgery alone, from our population-based series (n = 259). Mutational analysis of KIT and PDGFRA was performed in all cases. The progression-free survival was calculated.The primary tumors decreased in mean diameter from 20.4 cm to 10.5 cm on downsizing imatinib. Four patients with R0 resection and a period of adjuvant imatinib had no recurrences versus 67% in the historical control group. Four patients with residual liver metastases have stable disease on continuous imatinib treatment after surgery. One patient has undergone reoperation with liver resection. The downsizing treatment led to organ-preserving surgery in nine patients and improved preoperative nutritional status in one patient.Downsizing TKI is recommended for patients with bulky tumors with invasion of adjacent organs. Sunitinib can be used for patients in case of imatinib resistance (e.g., wild-type GISTs), underlining the importance of mutational analysis for optimal surgical planning.
Project description:Gastrointestinal stromal tumors (GISTs) with KIT or platelet-derived growth factor receptor alpha (PDGFRa) oncogenic driver gene mutations, respond to tyrosine kinase inhibitors (TKIs) including imatinib, sunitinib, and regorafenib. However, most patients develop TKI resistance; therefore, novel agents are required. We established three TKI-resistant GIST patient-derived xenograft (PDX) models for effective drug development. These were PDX models harboring primary and secondary KIT and additional mutations; KIT exon 11 (p.Y570_L576del), KIT exon 17 (p.D816E), and PTEN (p.T321fs) mutations in GIST-RX1 from a patient who was unresponsive to imatinib, sunitinib, and sorafenib, and KIT exon 11 (p.K550_splice) and KIT exon 14 (p.T670I) mutations in GIST-RX2 and KIT exon 9 (p.502_503insYA) and KIT exon 17 (p.D820E) mutations in GIST-RX4 from patients with imatinib and imatinib/sunitinib resistance, respectively. The histological features and mutation statuses of GIST PDXs were consistent with those of the original patient tumors, and the models showed TKI sensitivity comparable to clinical responses. Imatinib inhibited the KIT pathway in imatinib-sensitive GIST-T1 but not GIST-RX1, RX2, and RX4. These GIST PDX models will be useful for studying TKI resistance mechanisms and evaluating novel targeted agents in GIST.
Project description:Most gastrointestinal stromal tumors (GISTs) contain KIT or PDGFRA kinase gain-of-function mutations, and therefore respond clinically to imatinib and other tyrosine kinase inhibitor (TKI) therapies. However, clinical progression subsequently results from selection of TKI-resistant clones, typically containing secondary mutations in the KIT kinase domain, which can be heterogeneous between and within GIST metastases in a given patient. TKI-resistant KIT oncoproteins require HSP90 chaperoning and are potently inactivated by HSP90 inhibitors, but clinical applications in GIST patients are constrained by the toxicity resulting from concomitant inactivation of various other HSP90 client proteins, beyond KIT and PDGFRA. To identify novel targets responsible for KIT oncoprotein function, we performed parallel genome-scale short hairpin RNA (shRNA)-mediated gene knockdowns in KIT-mutant GIST-T1 and GIST882. GIST cells were infected with a lentiviral shRNA pooled library targeting 11?194 human genes, and allowed to proliferate for 5-7 weeks, at which point assessment of relative hairpin abundance identified the HSP90 cofactor, CDC37, as one of the top six GIST-specific essential genes. Validations in treatment-naive (GIST-T1, GIST882) vs imatinib-resistant GISTs (GIST48, GIST430) demonstrated that: (1) CDC37 interacts with oncogenic KIT; (2) CDC37 regulates expression and activation of KIT and downstream signaling intermediates in GIST; and (3) unlike direct HSP90 inhibition, CDC37 knockdown accomplishes prolonged KIT inhibition (>20 days) in GIST. These studies highlight CDC37 as a key biologic vulnerability in both imatinib-sensitive and imatinib-resistant GIST. CDC37 targeting is expected to be selective for KIT/PDGFRA and a subset of other HSP90 clients, and thereby represents a promising strategy for inactivating the myriad KIT/PDGFRA oncoproteins in TKI-resistant GIST patients.
Project description:BACKGROUND:Gastrointestinal stromal tumors (GISTs) are the most frequently diagnosed mesenchymal neoplasms of the gastrointestinal tract. Despite their biological and clinical heterogeneity, the majority of these tumors are positive for the receptor tyrosine kinase KIT and are driven by KIT- or platelet-derived growth factor receptor alpha (PDGFRA)-activating mutations. There are still uncertainties regarding their clinical and molecular characterization and the optimal treatment regimens, making it difficult to establish a universal treatment algorithm for these tumors. SUMMARY:From a clinical perspective, the main difference between GISTs and other gastrointestinal neoplasms is that the benign or malignant behavior of GISTs cannot be predicted from histopathology, but instead relies on empirically established scoring systems. Clinical data suggest that malignant potential may be an inherent quality of some GISTs rather than a feature acquired by the tumor during disease progression. Thus, some patients may require prolonged anti-tumor treatment even after complete surgical removal of the tumor. KEY MESSAGE:Although GISTs are the most frequently occurring mesenchymal neoplasms in the gastrointestinal tract, no universal treatment algorithms exist. This paper reviews the current evidence that guides the management of GISTs. PRACTICAL IMPLICATIONS:The management of localized GISTs involves the use of surgical resection, with the inclusion of preoperative tyrosine kinase inhibitor treatment for locally advanced, primarily unresectable tumors and for resectable cases requiring extensive surgery. Imatinib is also indicated as adjuvant therapy after complete surgical removal of GISTs with a high estimated risk of recurrence unless specific mutations conferring imatinib resistance are present. The optimal duration of adjuvant treatment is still controversial. For patients with metastatic imatinib-sensitive GISTs, imatinib constitutes the first-line standard treatment. Molecular characterization of the tumor (with respect to the PDGFRA and KIT genes) is mandatory prior to imatinib therapy. Sunitinib and regorafenib are established as alternative treatments for patients demonstrating generalized disease progression on imatinib. New tyrosine kinase inhibitors such as ponatinib and crenolanib as well as drugs targeting alternative pathways are currently under investigation. Surgery and locally ablative treatments may be indicated in some metastatic patients.
Project description:The tyrosine kinase inhibitor (TKI) imatinib has radically changed the natural history of KIT-driven gastrointestinal stromal tumours (GISTs). Approved second-line and third-line medical therapies are represented by the TKIs sunitinib and regorafenib, respectively. While imatinib remains the cardinal drug for patients with GISTs, novel therapies are being developed and clinically tested to overcome the mechanisms of resistance after treatments with the approved TKI, or to treat subsets of GISTs driven by rarer molecular events. Here, we review the therapy of GISTs, with a particular focus on the newest drugs in advanced phases of clinical testing that might soon change the current therapeutic algorithm.
Project description:Gastrointestinal stromal tumors (GISTs) originate from interstitial cells of Cajal and account for over 5,000 newly diagnosed cases in the United States. The discovery of activated KIT and PDGFRA mutations and introduction of imatinib revolutionized the treatment strategy and opened up the new era of target therapy for solid tumors. Although surgery remains the primary modality of treatment for curative purpose, almost half of the patients experienced disease recurrence. Tailoring (neo)-adjuvant treatment with imatinib is ongoing to meet the need for an effective therapy. Currently, two drugs (sunitinib and regorafenib) have obtained Food and Drug Administration approval for GISTs after imatinib failure. However, most of the patients eventually progress due to primary or secondary resistance. Deeper understanding of the molecular mechanisms will guide us to develop personalized strategies in the future. Discussion in this review includes current standard management and the most recent advances and multiple ongoing clinical trials with different approaches. This review will provide further steps to be taken to conquer refractory disease.
Project description:Gastrointestinal stromal tumors (GISTs) are the most common sarcoma of the gastrointestinal tract, with transformation typically driven by activating mutations of c-KIT and less commonly platelet-derived growth factor receptor alpha (PDGFRA). Successful targeting of c-KIT and PDGFRA with imatinib, a tyrosine kinase inhibitor (TKI), has had a major impact in advanced GIST and as an adjuvant and neoadjuvant treatment. If treatment with imatinib fails, further lines of TKI therapy have a role, but disease response is usually only measured in months, so strategies to maximize the benefit from imatinib are paramount. Here, we provide an overview of the structure and signaling of c-KIT coupled with a review of the clinical trials of imatinib in GIST. In doing so, we make recommendations about the duration of imatinib therapy and suggest how best to utilize imatinib in order to improve patient outcomes in the future.
Project description:BACKGROUND:Gastrointestinal stromal tumors (GISTs) with different types of mutations exhibit different clinical characteristics and prognosis. This study aimed to evaluate the prognostic value of mutations in KIT and PDGFRA in a large-scale cohort of GIST patients with current therapy including surgery and imatinib. METHODS:A total of 1163 patients diagnosed with GISTs between January 2006 and December 2018 were enrolled in this study. Mutation analysis was performed for exons 9, 11, 13, and 17 of KIT and exons 12 and 18 of PDGFRA. Mutations were grouped into 12 categories according to the gene, exon, and involved codons; they were analyzed considering the clinical characteristics, disease-free survival (DFS), and overall survival (OS) of patients with GISTs. RESULTS:In low-risk GISTs, we identified two predictors of worse DFS: tumor origin in the rectum and KIT exon 11 deletion involving two or more codons. In high-risk GISTs treated with R0 resection and imatinib, patients with KIT exon 11 homozygous mutations and KIT intron 10/exon 11 junction deletions demonstrated the highest recurrence rate, indicating that these mutations can be independent prognostic factors of DFS. The presence of KIT exon 11 homozygous mutations also independently influenced OS. CONCLUSION:Low-incidence mutations such as KIT exon 11 homozygous mutations or intron 10/exon 11 junction deletions in GISTs should be carefully evaluated to explore novel treatment strategies, as tumors with these mutations have a high recurrence rate and a very poor prognosis after surgery followed by imatinib adjuvant treatment.
Project description:Gastrointestinal stromal tumors (GISTs) with no mutations in exons 9, 11, 13, and 17 of the KIT gene and exons 12, and 18 of the PDGFRA gene were defined as KIT/PDGFRA wild-type and they accounted for ~15-20% of GISTs. However, some KIT/PDGFRA wild-type GISTs with KIT mutations in other exons were occasionally reported. We therefore assessed GISTs to understand the whole genomic genotypes of KIT or PDGFRA genes in KIT/PDGFRA wild-type GISTs.A cohort of 185 KIT/PDGFRA wild-type GISTs from 1,080 cases was retrospectively assessed. Thirty-nine patients were excluded due to insufficiency of genomic DNA data or failure of library preparation, and 146 patients were analyzed by targeted next-generation sequencing (NGS) followed by validation.For hot spots in KIT and PDGFRA genes, 23 out of 146 KIT/PDGFRA wild-type cases carried mutations according to NGS; there were 19 KIT mutations and 4 PDGFRA mutations, and these were exclusive. Intratumoral KIT mutational heterogeneity was observed in 4 of 19 samples which potentially triggered mechanisms of polyclonal evolution and metastasis and drug sensitivity. Eleven patients treated with imatinib were evaluable for clinical response, and 2 of 3 patients with KIT mutations achieved partial response (PR), while only 1 of 8 patients without KIT mutations reached PR.NGS had the potential property to identify partial mutant tumors from a subset of GISTs regarded as KIT/PDGFRA wild-type tumors using Sanger sequencing, and provided a better understanding of KIT/PDGFRA genotypes as well as identified patients eligible for imatinib therapy.
Project description:BACKGROUND:Most patients with KIT-mutant gastrointestinal stromal tumours (GISTs) benefit from imatinib, but treatment resistance results from outgrowth of heterogeneous subclones with KIT secondary mutations. Once resistance emerges, targeting KIT with tyrosine kinase inhibitors (TKIs) sunitinib and regorafenib provides clinical benefit, albeit of limited duration. METHODS:We systematically explored GIST resistance mechanisms to KIT-inhibitor TKIs that are either approved or under investigation in clinical trials: the studies draw upon GIST models and clinical trial correlative science. We subsequently modelled in vitro a rapid TKI alternation approach against subclonal heterogeneity. RESULTS:Each of the KIT-inhibitor TKIs targets effectively only a subset of KIT secondary mutations in GIST. Regorafenib and sunitinib have complementary activity in that regorafenib primarily inhibits imatinib-resistance mutations in the activation loop, whereas sunitinib inhibits imatinib-resistance mutations in the ATP-binding pocket. We find that rapid alternation of sunitinib and regorafenib suppresses growth of polyclonal imatinib-resistant GIST more effectively than either agent as monotherapy. CONCLUSIONS:Our data highlight that heterogeneity of KIT secondary mutations is the main mechanism of tumour progression to KIT inhibitors in imatinib-resistant GIST patients. Therapeutic combinations of TKIs with complementary activity against resistant mutations may be useful to suppress growth of polyclonal imatinib-resistance in GIST.
Project description:In gastrointestinal muscles, v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (KIT) is predominantly expressed by interstitial cells of Cajal (ICC) and platelet-derived growth factor receptor-? (PDGFRA) polypeptide is expressed by so-called fibroblast-like cells. KIT and PDGFRA have been reported to be coexpressed in ICC precursors and gastrointestinal stromal tumors (GISTs), which originate from the ICC lineage. PDGFRA signaling has been proposed to stimulate growth of GISTs that express mutant KIT, but the effects and mechanisms of selective blockade of PDGFRA are unclear. We investigated whether inhibiting PDGFRA could reduce proliferation of GIST cells with mutant KIT via effects on the KIT-dependent transcription factor ETV1.We studied 53 gastric, small intestinal, rectal, or abdominal GISTs collected immediately after surgery or archived as fixed blocks at the Mayo Clinic and University of California, San Diego. In human GIST cells carrying imatinib-sensitive and imatinib-resistant mutations in KIT, PDGFRA was reduced by RNA interference (knockdown) or inhibited with crenolanib besylate (a selective inhibitor of PDGFRA and PDGFRB). Mouse ICC precursors were retrovirally transduced to overexpress wild-type Kit. Cell proliferation was analyzed by methyltetrazolium, 5-ethynyl-2'-deoxyuridine incorporation, and Ki-67 immunofluorescence assays; we also analyzed growth of xenograft tumors in mice. Gastric ICC and ICC precursors, and their PDGFRA(+) subsets, were analyzed by flow cytometry and immunohistochemistry in wild-type, Kit(+/copGFP), Pdgfra(+/eGFP), and NOD/ShiLtJ mice. Immunoblots were used to quantify protein expression and phosphorylation.KIT and PDGFRA were coexpressed in 3%-5% of mouse ICC, 35%-44% of ICC precursors, and most human GIST samples and cell lines. PDGFRA knockdown or inhibition with crenolanib efficiently reduced proliferation of imatinib-sensitive and imatinib-resistant KIT(+)ETV1(+)PDGFRA(+) GIST cells (50% maximal inhibitory concentration = 5-32 nM), but not of cells lacking KIT, ETV1, or PDGFRA (50% maximal inhibitory concentration >230 nM). Crenolanib inhibited phosphorylation of PDGFRA and PDGFRB, but not KIT. However, Kit overexpression sensitized mouse ICC precursors to crenolanib. ETV1 knockdown reduced KIT expression and GIST proliferation. Crenolanib down-regulated ETV1 by inhibiting extracellular-signal-regulated kinase (ERK)-dependent stabilization of ETV1 protein and also reduced expression of KIT and PDGFRA.In KIT-mutant GIST, inhibition of PDGFRA disrupts a KIT-ERK-ETV1-KIT signaling loop by inhibiting ERK activation. The PDGFRA inhibitor crenolanib might be used to treat patients with imatinib-resistant, KIT-mutant GIST.