Characterization and assessment of the sensitivity and resistance of a newly established human gastrointestinal stromal tumour xenograft model to treatment with tyrosine kinase inhibitors

Abstract

BackgroundAcquired resistance to tyrosine kinase inhibitors (TKIs) in gastrointestinal stromal tumours (GISTs) is most commonly caused by secondary KIT or PDGFRA mutations. In this study we characterize a newly established GIST xenograft model, UZLX-GIST9, and evaluate the in vivo response of the model to standard TKIs (imatinib, sunitinib, and regorafenib).MethodsTumour fragments from a metastatic lesion of a GIST patient clinically progressing after treatment with imatinib, sunitinib and regorafenib were engrafted in a nude, immunodeficient mouse. Upon sequential passaging from mouse to mouse, tumour fragments were collected for histopathological and molecular characterization. The sensitivity of the model to treatment with TKIs was evaluated in 28 mice [passage 2 (n = 8), passage 4 (n = 20), 41 tumours]. Mice were grouped as follows: control (untreated), imatinib (50 mg/kg/BID), imatinib (100 mg/kg/BID), sunitinib (40 mg/kg/QD), and regorafenib (30 mg/kg/QD). After three weeks of oral treatment, tumours were collected for subsequent analysis. The efficacy of treatment was assessed by tumour volume, histopathology and Western immunoblotting.ResultsUZLX-GIST9 maintains the same typical morphological features and immunohistochemical characteristics as the original patient biopsy and expresses CD117 and DOG1. The KIT mutational profile (p.P577del + W557LfsX5+ D820G) remains the same as the original tissue sample originating from an intraspinal metastatic site. Three week treatment with different TKIs showed that the model is resistant to imatinib. Sunitinib induces tumour growth delay and regorafenib reduces the tumour burden by 30% as compared to control animals. While none of the TKIs had a significant effect on cell proliferation or cell survival, a remarkable increase of necrosis and significant reduction of microvessel density was observed under sunitinib and regorafenib. Western immunoblotting showed a mild reduction in KIT and AKT activation only in regorafenib treated tumours.ConclusionsWe established a novel human GIST xenograft, UZLX-GIST9, harbouring KIT exon 11 and 17 mutations and maintaining the pheno-and genotype of the original tumour. UZLX-GIST9 shows different levels of response to standard TKIs. This model will help to study TKI resistance and to explore novel treatment approaches for patients with TKI-resistant GIST.

Cabozantinib Is Active against Human Gastrointestinal Stromal Tumor Xenografts Carrying Different KIT Mutations

“…This could be due to the presence of a high rate of spontaneous apoptosis among the untreated control mice; therefore, the treatment effect could not be observed. Moreover, in experiments performed earlier by our group, treatment of UZLX-GIST9 or -GIST2 models with the angiogenesis inhibitor sunitinib showed an effect similar to that of cabozantinib on tumor volume and MVD but did not result in an increase of apoptotic activity, suggesting the antiangiogenic effects in these models may not induce apoptosis but rather necrosis and/or inhibition of proliferation (18,27). These observations support the investigation of cabozantinib in patients with GIST and suggest a potential advantage over imatinib.…”

“…Three PDX models, namely UZLX-GIST4 [passage (p) 21, KIT p.K558_G565delinsR; imatinibsensitive model], -GIST2 (p. 17, KIT p.A502_Y503dup; dosedependent resistance to imatinib), and -GIST9 (p. 6, KIT p.P577del;W557LfsX5;D820G; imatinib-and sunitinib-resistant) were used in the study. These models are characterized by human origin and stable morphological features and molecular characteristics similar to the original tumor as previously described (16)(17)(18).…”

Robust Activity of Avapritinib, Potent and Highly Selective Inhibitor of Mutated KIT, in Patient-derived Xenograft Models of Gastrointestinal Stromal Tumors

“…In the presented experiments, imatinib led to a significant tumor regression in UZLX-GIST3 KIT 11 and a dose-dependent effect on tumor volume in UZLX-GIST2B KIT 9 , as already observed in multiple studies, confirming once again the stable biological behavior of this model (13,17,18). These findings are also in line with the behavior of such tumors in the clinic; patients with KIT exon 9 mutations respond better to higher dose of imatinib, as confirmed by a clinical meta-analysis (21).…”

“…The dosing solutions of imatinib, sunitinib, and regorafenib (all from Sequoia Research) were prepared as described earlier (13). Avapritinib, provided by Blueprint Medicines, was dissolved in 0.5% carboxymethyl cellulose supplemented with 1% Tween 80.…”

A Case of Sinonasal Melanoma With Unusual Primary Exon 17 KIT D820G Mutation

“…16,17 In GIST, D820G mutation has been reported as a secondary gene mutation responsible for acquired resistance of neoplasm to imatinib. 15,18 This mutation has not been reported before in mucosal melanomas (Table 1).…”