Early effects of imatinib mesylate on the expression of insulin-like growth factor binding protein-3 and positron emission tomography in patients with gastrointestinal stromal tumor

Gene expression analyses determine two different subpopulations in KIT-negative GIST-like (KNGL) patients

Introduction

There are limited findings available on KIT-negative GIST-like (KNGL) population. Also, KIT expression may be post-transcriptionally regulated by miRNA221 and miRNA222. Hence, the aim of this study is to characterize KNGL population, by differential gene expression, and to analyze miRNA221/222 expression and their prognostic value in KNGL patients.

Methods

KIT, PDGFRA, DOG1, IGF1R, MIR221 and MIR222 expression levels were determined by qRT-PCR. We also analyzed KIT and PDGFRA mutations, DOG1 expression, by immunohistochemistry, along with clinical and pathological data. Disease-free survival (DFS) and overall survival (OS) differences were calculated using Log-rank test.

Results

Hierarchical cluster analyses from gene expression data identified two groups: group I had KIT, DOG1 and PDGFRA overexpression and IGF1R underexpression and group II had overexpression of IGF1R and low expression of KIT, DOG1 and PDGFRA. Group II had a significant worse OS (p = 0.013) in all the series, and showed a tendency for worse OS (p = 0.11), when analyzed only the localized cases. MiRNA222 expression was significantly lower in a control subset of KIT-positive GIST (p < 0.001). OS was significantly worse in KNGL cases with higher expression of MIR221 (p = 0.028) or MIR222 (p = 0.014).

Conclusions

We identified two distinct KNGL subsets, with a different prognostic value. Increased levels of miRNA221/222, which are associated with worse OS, could explain the absence of KIT protein expression of most KNGL tumors.

GEIS guidelines for gastrointestinal sarcomas (GIST)

Gastrointestinal stromal sarcomas (GISTs) are the most common mesenchymal tumours originating in the digestive tract. They have a characteristic morphology, are generally positive for CD117 (c-kit) and are primarily caused by activating mutations in the KIT or PDGFRA genes(1). On rare occasions, they occur in extravisceral locations such as the omentum, mesentery, pelvis and retroperitoneum. GISTs have become a model of multidisciplinary work in oncology: the participation of several specialties (oncologists, pathologists, surgeons, molecular biologists, radiologists…) has forested advances in the understanding of this tumour and the consolidation of a targeted therapy, imatinib, as the first effective molecular treatment in solid tumours. Following its introduction, median survival of patients with advanced or metastatic GIST increased from 18 to more than 60months. Sunitinib and Regorafenib are two targeted agents with worldwide approval for second- and third-line treatment, respectively, in metastatic GIST.

Role of insulin-like growth factor-binding proteins in the pathophysiology and tumorigenesis of gastroesophageal cancers

The insulin family of proteins include insulin-like growth factor binding proteins (IGFBPs) that are classified into two groups based on their differential affinities to IGFs: IGF high-affinity binding proteins (IGFBP1-6) and IGF low-affinity IGFBP-related proteins (IGFBP-rP1-10). IGFBPs interact with many proteins, including their canonical ligands insulin-like growth factor 1 (IGF-I) and IGF-II. Together with insulin-like growth factor 1 (IGF1) receptor (IGF1R), IGF2R, and ligands (IGF1 and IGF2), IGFBPs participate in a complex signaling axis called IGF-IGFR-IGFBP. Numerous studies have demonstrated that the IGF-IGFR-IGFBP axis is relevant in gastrointestinal (GI) and other cancers. The presence of different IGFBPs have been reported in gastrointestinal cancers, including esophageal squamous cell carcinoma (ESCC), esophageal adenocarcinoma (EAD or EAC), and gastric adenocarcinoma (GAD or GAC). A literature-based survey clearly indicates that an urgent need exists for a focused review of the role of IGFBPs in gastrointestinal cancers. The aim of this review is to present the biochemical and molecular characteristics of IGFBPs with an emphasis specifically on the role of these proteins in the pathophysiology and tumorigenesis of gastroesophageal cancers.

Therapeutic targets in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common type of mesenchymal tumor of the gastrointestinal tract. The tumorigenesis of GISTs is driven by gain-of-function mutations in KIT or platelet-derived growth factor receptor α (PDGFRA), resulting in constitutive activation of the tyrosine kinase and its downstream signaling pathways. Oncogenic KIT or PDGFRA mutations are compelling therapeutic targets for the treatment of GISTs, and the KIT/PDGFRA inhibitor imatinib is the standard of care for patients with metastatic GISTs. However, most GIST patients develop clinical resistance to imatinib and other tyrosine kinase inhibitors. Five mechanisms of resistance have been characterized: (1) acquisition of a secondary point mutation in KIT or PDGFRA; (2) genomic amplification of KIT; (3) activation of an alternative receptor tyrosine kinase; (4) loss of KIT oncoprotein expression; and (5) wild-type GIST. Currently, sunitinib is used as a second-line treatment for patients after imatinib failure, and regorafenib has been approved for patients whose disease is progressing on both imatinib and sunitinib. Phase II/III trials are currently in progress to evaluate novel inhibitors and immunotherapies targeting KIT, its downstream effectors such as phosphatidylinositol 3-kinase, protein kinase B and mammalian target of rapamycin, heat shock protein 90, and histone deacetylase inhibitor. Other candidate targets have been identified, including ETV1, AXL, insulin-like growth factor 1 receptor, KRAS, FAS receptor, protein kinase c theta, ANO1 (DOG1), CDC37, and aurora kinase A. These candidates warrant clinical evaluation as novel therapeutic targets in GIST.

GEIS 2013 guidelines for gastrointestinal sarcomas (GIST)

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal soft tissue sarcoma of the gastrointestinal tract. Correct diagnosis with thorough use of pathologic and molecular tools of GIST mutations has been of the foremost importance. GIST are usually (95 %) KIT positive and harbor frequent KIT or platelet-derived growth factor receptor α-activating mutations. This deep molecular understanding has allowed the correct classification into risk groups with implications regarding prognosis, essential use in the development of targeted therapies and even response prediction to this drugs. Treatment has been evolving and an update to include lessons learned from recent trials in advanced disease as well as controversies in the adjuvant setting that are changing daily practice, is reviewed here. An effort from the Spanish Group for Sarcoma Research with investigators from the group has been undertaken to launch this third version of the GIST guidelines and provide a practical means for the different disciplines that treat this complex disease.

Recent advances in the molecular imaging of programmed cell death: part I--pathophysiology and radiotracers

In humans, apoptosis (programmed cell death) is the most common form of cell death after necrosis. Apoptosis is a series of genetically preprogrammed biochemical and morphologic energy-requiring events that, after a specific external or internal stimulus, results in the physiologic disappearance of a cell via its self-disintegration and packaging of its contents into membrane vesicles called apoptotic bodies. Apoptotic bodies can readily be ingested, with their nutrients and even organelles recycled by neighboring cells or phagocytes without local inflammation. In contrast, necrosis is characterized by the primary loss of plasma membrane integrity and the uncontrolled release of a cell's contents, often causing local inflammation, tissue damage, and scarring. Alternate forms of cell death also exist, associated with specific molecular mechanisms involving enzymes, organelles, genes, external stimuli, or blockade of normal cell proliferation. In this review we will briefly outline the molecular mechanisms of apoptosis that can be imaged with radiotracers now under development.

Gastrointestinal stromal tumors: Molecular pathogenesis and targeted therapy

The autophosphorylation of KIT protein, resulting from gain-of-function mutations of the c-kit or PDGFR gene, is the most important molecular mechanism involved in the pathogenesis of gastrointestinal stromal tumors (GISTs). Imatinib is a small molecule tyrosine kinase inhibitor and is effective in the treatment of GISTs. KIT is a convenient target in GISTs, and inhibition of this receptor with imatinib (Gleevec, STI571) in GISTs has shown dramatic efficacy. Unfortunately, resistance to imatinib is a significant clinical problem. Further understanding of the molecular pathogenesis of GISTs is therefore important and may lead to the identification of novel drug targets. This review will focus on recent advances in the understanding of molecular mechanisms involved in the pathogenesis of all types of GISTs. The molecular biological characteristics of each type of GISTs will also be discussed.

Consensus report on the radiological management of patients with gastrointestinal stromal tumours (GIST): recommendations of the German GIST Imaging Working Group

The aim was to reach consensus in imaging for staging and follow-up as well as for therapy response assessment in patients with gastrointestinal stromal tumours (GIST). The German GIST Imaging Working Group was formed by 9 radiologists engaged in assessing patients with GIST treated with targeted therapy. The following topics were discussed: indication and optimal acquisition techniques of computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET)/CT; tumour response assessment considering response criteria and measurement techniques on CT, MRI and PET/CT; result interpretation; staging interval and pitfalls. Contrast-enhanced CT is the standard method for GIST imaging. MRI is the method of choice in case of liver-specific questions or contraindications to CT. PET/CT should be used for early response assessment or inconclusive results on morphologic imaging. All imaging techniques should be standardized allowing a reliable response assessment. Response has to be assessed with respect to lesion size, lesion density and appearance of new lesions. A critical issue is pseudoprogression due to myxoid degeneration or intratumoural haemorrhage. The management of patients with GIST receiving a targeted therapy requires a standardized algorithm for imaging and an appropriate response assessment with respect to changes in lesion size and density.

Multimodality molecular imaging of apoptosis in oncology

OBJECTIVE

The purposes of this review are to describe the signaling pathways of and the cellular changes that occur with apoptosis and other forms of cell death, summarize tracers and modalities used for imaging of apoptosis, delineate the relation between apoptosis and inhibition of protein translation, and describe spectroscopic technologies that entail high-frequency ultrasound and infrared and midinfrared light in characterizing the intracellular events of apoptosis.

CONCLUSION

Apoptosis is a highly orchestrated set of biochemical and morphologic cellular events. These events present many potential targets for the imaging of apoptosis in vivo. Imaging of apoptosis can facilitate early assessment of anticancer treatment before tumor shrinkage, which may increase the effectiveness of delivery of chemotherapy and radiation therapy and speed drug development.

Molecular basis for primary and secondary tyrosine kinase inhibitor resistance in gastrointestinal stromal tumor

Small molecule kinase inhibitors have irrevocably altered cancer treatment. March 2010 marks the 10th anniversary of using imatinib in gastrointestinal stromal tumors (GIST), a cardinal example of the utility of such targeted therapy in a solid tumor. Before imatinib, metastatic GIST was frustrating to treat due to its resistance to standard cytotoxic chemotherapy. Median survival for patients with metastatic GIST improved from 19 to 60 months with imatinib. In treating patients with GIST, two patterns of tyrosine kinase inhibitor resistance have been observed. In the first, ~9-14% of patients have progression within 3 months of starting imatinib. These patients are classified as having primary or early resistance. Median progression-free survival (PFS) on imatinib is approximately 24 months; patients with later progression are classified as having secondary or acquired resistance. Primary studies and a meta-analysis of studies of imatinib in GIST patients have identified prognostic features that contribute to treatment failure. One of the strongest predictors for success of therapy is KIT or PDGFRA mutational status. Patients with KIT exon 11 mutant GIST have better response rates, PFS, and overall survival compared to other mutations. A great deal has been learned in the last decade about sensitivity and resistance of GIST to imatinib; however, many unanswered questions remain about secondary resistance mechanisms and clinical management in the third- and fourth-line setting. This review will discuss the role of dose effects, and early and late resistance to imatinib and their clinical implications. Patients intolerant to imatinib (5%) and those who progress on imatinib are treated with sunitinib. The mechanism of resistance to sunitinib is unknown at this time but is also appears related to growth of clones with secondary mutations in KIT. Third- and fourth-line treatments of GIST and with future treatment strategies are also discussed.

Mechanisms of resistance to imatinib and sunitinib in gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST), the most common mesenchymal neoplasm of the GI tract and one of the most common sarcomas, is dependent on the expression of the mutated KIT or platelet-derived growth factor receptor in most cases. Imatinib mesylate potently abrogates the effects of KIT signaling by directly binding into the ATP-binding pocket of the kinase. It is becoming increasingly apparent that the binding affinity of imatinib for the receptor is dependent on the type and location of mutation. Within KIT, patients whose tumor has an exon 9 mutation are treated by many clinicians with higher doses of imatinib than those patients with mutations within exon 11. Additionally, there are over 400 unique mutations within exon 11 that may have distinctly different binding affinity for imatinib as well as other kinases. Secondary KIT mutations generally occur at a codon where imatinib binds resulting in KIT reactivation and resistance. Sunitinib malate, a second-generation KIT inhibitor is active in imatinib-resistant disease and is FDA-approved for use in this setting. In this review, we describe the biology of the genes and gene mutations responsible for GIST and discuss known and potential clinical implications.

Small is beautiful: insulin-like growth factors and their role in growth, development, and cancer

Insulin-like growth factors were discovered more than 50 years ago as mediators of growth hormone that effect growth and differentiation of bone and skeletal muscle. Interest of the role of insulin-like growth factors in cancer reached a peak in the 1990s, and then waned until the availability in the past 5 years of monoclonal antibodies and small molecules that block the insulin-like growth factor 1 receptor. In this article, we review the history of insulin-like growth factors and their role in growth, development, organism survival, and in cancer, both epithelial cancers and sarcomas. Recent developments regarding phase I to II clinical trials of such agents are discussed, as well as potential studies to consider in the future, given the lack of efficacy of one such monoclonal antibody in combination with cytotoxic chemotherapy in a first-line study in metastatic non-small-cell lung adenocarcinoma. Greater success with these agents clinically is expected when combining the agents with inhibitors of other cell signaling pathways in which cross-resistance has been observed.

Synergistic induction of apoptosis by the Bcl-2 inhibitor ABT-737 and imatinib mesylate in gastrointestinal stromal tumor cells

BACKGROUND

Although imatinib mesylate has revolutionized the management of patients with gastrointestinal stromal tumor (GIST), resistance and progression almost inevitably develop with long-term monotherapy. To enhance imatinib-induced cytotoxicity and overcome imatinib-resistance in GIST cells, we examined the antitumor effects of the pro-apoptotic Bcl-2/Bcl-x(L) inhibitor ABT-737, alone and in combination with imatinib.

METHODS

We treated imatinib-sensitive, GIST-T1 and GIST882, and imatinib-resistant cells with ABT-737 alone and with imatinib. We determined the anti-proliferative and apoptotic effects by cell viability assay, flow cytometric apoptosis and cell cycle analysis, immunoblotting, and nuclear morphology. Synergism was determined by isobologram analysis.

RESULTS

The IC(50) of single-agent ABT-737 at 72 h was 10 μM in imatinib-sensitive GIST-T1 and GIST882 cells, and 1 μM in imatinib-resistant GIST48IM cells. ABT-737 and imatinib combined synergistically in a time- and dose-dependent manner to inhibit the proliferation and induce apoptosis of all GIST cells, as evidenced by cell viability and apoptosis assays, caspase activation, PARP cleavage, and morphologic changes. Isobologram analyses revealed strongly synergistic drug interactions, with combination indices <0.5 for most ABT-737/imatinib combinations. Thus, clinically relevant in vitro concentrations of ABT-737 have single-agent antitumor activity and are synergistic in combination with imatinib.

CONCLUSION

We provide the first preclinical evidence that Bcl-2/Bcl-x(L) inhibition with ABT-737 synergistically enhances imatinib-induced cytotoxicity via apoptosis, and that direct engagement of apoptotic cell death may be an effective approach to circumvent imatinib-resistance in GIST.

Neoadjuvant and adjuvant imatinib treatment in gastrointestinal stromal tumor: current status and recent developments

PURPOSE OF REVIEW

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract and is a paradigm of targeted therapy for solid tumors. Elucidation of the biology of GIST enabled use of imatinib, which revolutionized the prognosis of advanced GIST. Whereas surgical resection continues to be the standard of care for primary GIST, judicious and individualized use of adjuvant and neoadjuvant imatinib may enhance the potential for cure in select patients.

RECENT FINDINGS

Prospective trials utilizing adjuvant and neoadjuvant imatinib have established the safety and efficacy of these modalities adjunct to surgical resection. Correlative tissue studies derived from these trials have examined gene expression patterns, metabolic and radiographic response, and apoptosis during the first few days of imatinib therapy. As appropriate use of adjuvant and neoadjuvant imatinib requires proper patient selection, development of a predictive nomogram, and advances in mutational analysis represent progress toward individualized care.

SUMMARY

Imatinib is well tolerated and beneficial as adjuvant and neoadjuvant therapy, but its utility in these settings continues to be refined. The greatest benefit will derive from an individualized approach that considers multiple patient, drug, and tumor characteristics to assess risk and likelihood of benefit for each patient.

Incidental non-secreting adrenal masses in cancer patients: intra-individual comparison of 18F-fluorodeoxyglucose positron emission tomography/computed tomography with computed tomography and shift magnetic resonance imaging

The ability of integrated (18)F-fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) to distinguish between benign and malignant incidental non-secreting adrenal masses was evaluated in cancer patients. Results were compared with those of CT and shift magnetic resonance imaging (MRI). A total of 1832 cancer patients who had undergone FDG PET/CT scans were retrospectively evaluated. Visual interpretation, tumour maximum standardized uptake value (SUV(max)), liver SUV(max) and tumour/liver SUV(max) ratios were correlated with the findings of CT, shift MRI and final diagnosis (based on biopsy or clinical/radiological follow-up). A total of 109 adrenal masses were found: 49 were malignant and 60 were benign on final diagnosis. A tumour/liver SUV(max) ratio threshold of 1.0 was more accurate in differentiating the tumour type than tumour SUV(max) or visual interpretation alone. Diagnostic accuracy of CT and shift MRI (92 - 97%) was similar to that for FDG PET/CT (94 - 97%). In conclusion, FDG PET/CT accurately characterizes adrenal tumours, with excellent sensitivity and specificity. Use of 1.0 as the threshold for the tumour/liver SUV(max) ratio seems to be promising for distinguishing benign from malignant adrenal masses in cancer patients.

Imaging the molecular signatures of apoptosis and injury with radiolabeled annexin V

Annexin V is a ubiquitous intracellular protein in humans that has a variety of intriguing characteristics, including a nanomolar affinity for the membrane-bound constitutive anionic phospholipid known as phosphatidylserine (PS). PS is selectively expressed on the surface of apoptotic or physiologically stressed cells. As such, radiolabeled forms of annexin V have been used in both animal models and human Phase I and Phase II trials to determine if this tracer can be employed as an early surrogate marker of therapeutic efficacy in NSCLC and non-Hodgkin's lymphoma. Many other pulmonary imaging applications of radiolabeled annexin V are also possible, including the detection and monitoring of active pulmonary inflammation and other pathophysiologic stressors in a variety of diseases. In this article, the salient molecular features of apoptosis (and other forms of cell death) that permits imaging with radiolabeled annexin V will be discussed. The latest results from Phase II imaging trials with NSCLC and non-Hodgkin's lymphoma will be also be detailed. Finally, the potential future application of this tracer for the imaging of other pulmonary pathologies will be outlined.

Insulin-like growth factor binding protein-3 has dual effects on gastrointestinal stromal tumor cell viability and sensitivity to the anti-tumor effects of imatinib mesylate in vitro

Background

Imatinib mesylate has significantly improved survival and quality of life of patients with gastrointestinal stromal tumors (GISTs). However, the molecular mechanism through which imatinib exerts its anti-tumor effects is not clear. Previously, we found up-regulation of insulin-like growth factor binding protein-3 (IGFBP3) expression in imatinib-responsive GIST cells and tumor samples. Because IGFBP3 regulates cell proliferation and survival and mediates the anti-tumor effects of a number of anti-cancer agents through both IGF-dependent and IGF-independent mechanisms, we hypothesized that IGFBP3 mediates GIST cell response to imatinib. To test this hypothesis, we manipulated IGFBP3 levels in two imatinib-responsive GIST cell lines and observed cell viability after drug treatment.

Results

In the GIST882 cell line, imatinib treatment induced endogenous IGFBP3 expression, and IGFBP3 down-modulation by neutralization or RNA interference resulted in partial resistance to imatinib. In contrast, IGFBP3 overexpression in GIST-T1, which had no detectable endogenous IGFBP3 expression after imatinib, had no effect on imatinib-induced loss of viability. Furthermore, both the loss of IGFBP3 in GIST882 cells and the overexpression of IGFBP3 in GIST-T1 cells was cytotoxic, demonstrating that IGFBP3 has opposing effects on GIST cell viability.

Conclusion

This data demonstrates that IGFBP3 has dual, opposing roles in modulating GIST cell viability and response to imatinib in vitro. These preliminary findings suggest that there may be some clinical benefits to IGFBP3 therapy in GIST patients, but further studies are needed to better characterize the functions of IGFBP3 in GIST.

High density DNA array analysis reveals distinct genomic profiles in a subset of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) generally harbor activating mutations in KIT or platelet-derived growth facter receptor (PDGFRA). Mutations in these receptor tyrosine kinases lead to dysregulation of downstream signaling pathways that contribute to GIST pathogenesis. GISTs with KIT or PDGFRA mutations also undergo secondary cytogenetic alterations that may indicate the involvement of additional genes important in tumor progression. Approximately 10-15% of adult and 85% of pediatric GISTs do not have mutations in KIT or in PDGFRA. Most mutant adult GISTs display large-scale genomic alterations, but little is known about the mutation-negative tumors. Using genome-wide DNA arrays, we investigated genomic imbalances in a set of 31 GISTs, including 10 KIT/PDGFRA mutation-negative tumors from nine adults and one pediatric case and 21 mutant tumors. Although all 21 mutant GISTs exhibited multiple copy number aberrations, notably losses, eight of the 10 KIT/PDGFRA mutation-negative GISTs exhibited few or no genomic alterations. One KIT/PDGFRA mutation-negative tumor exhibiting numerous genomic changes was found to harbor an alternate activating mutation, in the serine-threonine kinase BRAF. The only other mutation-negative GIST with significant chromosomal imbalances was a recurrent metastatic tumor found to harbor a homozygous deletion in chromosome arm 9p. Similar findings in several KIT-mutant GISTs identified a minimal overlapping region of deletion of approximately 0.28 Mbp in 9p21.3 that includes only the CDKN2A/2B genes, which encode inhibitors of cell-cycle kinases. These results suggest that GISTs without activating kinase mutations, whether pediatric or adult, generally exhibit a much lower level of cytogenetic progression than that observed in mutant GISTs.

Sunitinib treatment in pediatric patients with advanced GIST following failure of imatinib

BACKGROUND

Sunitinib inhibits KIT and other members of the split-kinase-domain family of receptor tyrosine kinases. Sunitinib prolongs survival in adult patients with imatinib-resistant gastrointestinal stromal tumor (GIST). We report the experience with sunitinib in pediatric patients with advanced GIST following failure of imatinib.

PROCEDURE

Sunitinib therapy was provided through a treatment-use protocol. Patients were 10-17 years old at enrollment. All patients had GIST resistant to imatinib therapy. Sunitinib was administered daily for 4 weeks in 6-week treatment cycles. KIT and platelet-derived growth factor receptor alpha (PDGFRA) genotyping of tumor tissue were performed.

RESULTS

One patient achieved a partial response, five patients had stable disease and one patient had progressive disease on sunitinib. The duration of disease stabilization was between 7 and 21+ months, with a mean of 15 months. Time to tumor progression was longer on sunitinib than on prior imatinib treatment for five of six patients. Two patients experienced grade 3 adverse events. All other adverse events were grade 1-2. None of the five patients tested had mutations in KIT or PDGFRA.

CONCLUSION

Sunitinib treatment was associated with substantial initial antitumor activity and acceptable tolerability in this group of pediatric patients with imatinib-resistant GIST.

Insulin-like growth factors and insulin-like growth factor-binding proteins in relation to disease status and incidence of hypoglycaemia in patients with a gastrointestinal stromal tumour

OBJECTIVE

Patients with a gastrointestinal stromal tumour (GIST) suffering from non-islet cell tumour-induced hypoglycaemia (NICTH), being associated with increased plasma levels of pro-insulin-like growth factor (IGF)-IIE[68-88], have been reported occasionally. We studied the clinical relevance of pro-IGF-IIE[68-88] and other IGF-related proteins in GIST patients.

PATIENTS AND METHODS

Twenty-four patients were included. Plasma samples were collected before 1 week and median 5 months after start of treatment with imatinib, and levels of IGF-I, total IGF-II, pro-IGF-IIE[68-88], insulin-like growth factor-binding protein (IGFBP)-2, -3 and -6 were determined. GIST specimens from 17 patients and tumour cyst fluid from two patients were analysed for IGF-II and IGFBP-2.

RESULTS

Before treatment and/or during follow-up, 3 of 24 (13%) patients showed increased plasma levels of pro-IGF-IIE[68-88]. All three developed NICTH. Overall, patients with metastatic disease, elevated serum lactate dehydrogenase activity or total tumour size >12 cm had the highest pro-IGF-IIE[68-88] levels. Most patients had increased plasma IGFBP-2 levels and these levels were significantly higher in patients with progressive disease. (Pro-)IGF-II was expressed in 82% of GISTs and IGFBP-2 only in one case.

CONCLUSION

We identified pro-IGF-IIE[68-88] as a marker that may be used in the surveillance of GIST.

Molecular imaging of therapeutic response to epidermal growth factor receptor blockade in colorectal cancer

PURPOSE

To evaluate noninvasive molecular imaging methods as correlative biomarkers of therapeutic efficacy of cetuximab in human colorectal cancer cell line xenografts grown in athymic nude mice. The correlation between molecular imaging and immunohistochemical analysis to quantify epidermal growth factor (EGF) binding, apoptosis, and proliferation was evaluated in treated and untreated tumor-bearing cohorts.

EXPERIMENTAL DESIGN

Optical imaging probes targeting EGF receptor (EGFR) expression (NIR800-EGF) and apoptosis (NIR700-Annexin V) were synthesized and evaluated in vitro and in vivo. Proliferation was assessed by 3'-[18F]fluoro-3'-deoxythymidine ([18F]FLT) positron emission tomography. Assessment of inhibition of EGFR signaling by cetuximab was accomplished by concomitant imaging of NIR800-EGF, NIR700-Annexin V, and [18F]FLT in cetuximab-sensitive (DiFi) and insensitive (HCT-116) human colorectal cancer cell line xenografts. Imaging results were validated by measurement of tumor size and immunohistochemical analysis of total and phosphorylated EGFR, caspase-3, and Ki-67 immediately following in vivo imaging.

RESULTS

NIR800-EGF accumulation in tumors reflected relative EGFR expression and EGFR occupancy by cetuximab. NIR700-Annexin V accumulation correlated with cetuximab-induced apoptosis as assessed by immunohistochemical staining of caspase-3. No significant difference in tumor proliferation was noted between treated and untreated animals by [18F]FLT positron emission tomography or Ki-67 immunohistochemistry.

CONCLUSIONS

Molecular imaging can accurately assess EGF binding, proliferation, and apoptosis in human colorectal cancer xenografts. These imaging approaches may prove useful for serial, noninvasive monitoring of the biological effects of EGFR inhibition in preclinical studies. It is anticipated that these assays can be adapted for clinical use.

A randomized, phase II study of preoperative plus postoperative imatinib in GIST: evidence of rapid radiographic response and temporal induction of tumor cell apoptosis

Gastrointestinal stromal tumor (GIST) is the most common sarcoma arising in the gastrointestinal (GI) tract. Imatinib mesylate (imatinib) is efficacious in treating advanced and metastatic GIST. Patients undergoing resection of GIST realize a highly variable median disease-free survival (DFS). In the absence of prospective data, we conducted a randomized, phase II study to assess the safety and efficacy of preoperative and postoperative imatinib for the treatment of GIST. Nineteen GIST patients undergoing surgical resection were randomized to receive 3, 5, or 7 days of preoperative imatinib (600 mg daily). Patients received postoperative imatinib for 2 years. Perioperative adverse events were compared with those in an imatinib-naïve historical control. The efficacy of imatinib was assessed by ¹⁸fluorodeoxyglucose positron emission tomography (¹⁸FDG-PET), dynamic computed tomography (dCT), terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and DFS. Imatinib did not affect surgical morbidity as compared with an imatinib-naïve cohort (p ≥ 0.1). Most patients responded to preoperative imatinib by ¹⁸FDG-PET and dCT (69% and 71%, respectively). Tumor cell apoptosis increased by an average of 12% (range 0–33%) and correlated with the duration of preoperative imatinib (p = 0.04). Median DFS of patients treated with surgery and imatinib was 46 months (range 10–46 months). Tumor size was a predictor of recurrence after postoperative imatinib (p = 0.02). Imatinib appears to be safe and may be considered for patients undergoing surgical resection of their GIST. Radiographic response and tumor cell apoptosis occur within the first week of imatinib therapy.

The insulin-like growth factor system as a potential therapeutic target in gastrointestinal stromal tumors

The majority of gastrointestinal stromal tumors (GISTs) are characterized by oncogenic gain-of-function mutations in the receptor tyrosine kinase (RTK) c-KIT with a minority in PDGFRalpha. Therapy for GISTs has been revolutionized by the use of the selective tyrosine kinase inhibitor imatinib mesylate (IM). For the subset (approximately 10-15%) of GISTs that lack oncogenic mutations in these receptors, the genetic changes driving tumorigenesis are unknown. We recently reported that the gene encoding the insulin-like growth factor 1 receptor (IGF-1R) is amplified in a subset of GISTs, and the IGF-1R protein is overexpressed in wild-type and pediatric GISTs. In this report we present a more complete picture of the involvement of components of the insulin-like growth factor-signaling pathway in the pathogenesis of GISTs. We also discuss how the IGF pathway may provide additional molecular targets for the treatment of GISTs that respond poorly to IM therapy.

Insulin-like growth factor 1 receptor is a potential therapeutic target for gastrointestinal stromal tumors

A subset of gastrointestinal stromal tumors (GISTs) lack gain-of-function mutations in c-KIT and PDGFRalpha. These so-called wild-type (WT) GISTs tend to be less responsive to imatinib-based therapies and have a poor prognosis. We identified amplification of IGF1R in a SNP analysis of GIST and thus studied its potential as a therapeutic target in WT and mutant GIST. Expression of IGF1R and downstream effectors in clinical GIST samples was examined by using immunoblots and immunohistochemistry. The roles of IGF1R signaling in GIST and viability were analyzed by using NVP-AEW541, an inhibitor of IGF1R, alone and in combination with imatinib, or via siRNA silencing of IGF1R. IGF1R was strongly overexpressed, and IGF1R amplification was detected at a significantly higher frequency in WT GISTs, including a pediatric WT GIST, compared with mutant GISTs (P = 0.0173 and P = 0.0163, respectively). Inhibition of IGF1R activity in vitro with NVP-AEW541 or down-regulation of expression with siIGF1R led to cytotoxicity and induced apoptosis in GIST cell lines via AKT and MAPK signaling. Combination of NVP-AEW541 and imatinib in GIST cell lines induced a strong cytotoxicity response. Our results reveal that IGF1R is amplified and the protein is overexpressed in WT and pediatric GISTs. We also demonstrate that the aberrant expression of IGF1R may be associated with oncogenesis in WT GISTs and suggest an alternative and/or complementary therapeutic regimen in the clinical management of all GISTs, especially in a subset of tumors that respond less favorably to imatinib-based therapy.

Tumour necrosis factor-induced gene expression in human marrow stroma: clues to the pathophysiology of MDS?

Aberrant regulation of the tumour necrosis factor alpha gene (TNF) and stroma-derived signals are involved in the pathophysiology of myelodysplasia. Therefore, KG1a, a myeloid leukaemia cell line, was exposed to Tnf in the absence or presence of either HS-5 or HS-27a cells, two human stroma cell lines. While KG1a cells were resistant to Tnf-induced apoptosis in the absence of stroma cells, Tnf-promoted apoptosis of KG1a cells in co-culture experiments with stroma cells. To investigate the Tnf-induced signals from the stroma cells, we examined expression changes in HS-5 and HS-27a cells after Tnf exposure. DNA microarray studies found both discordant and concordant Tnf-induced expression responses in the two stroma cell lines. Tnf promoted an increased mRNA expression of pro-inflammatory cytokines [e.g. interleukin (IL)6, IL8 and IL32]. At the same time, Tnf decreased the mRNA expression of anti-apoptotic genes (e.g. BCL2L1) and increased the mRNA expression of pro-apoptotic genes (e.g. BID). Overall, the results suggested that Tnf induced a complex set of pro-inflammatory and pro-apoptotic signals in stroma cells that promote apoptosis in malignant myeloid clones. Additional studies will be required to determine which of these signals are critical for the induction of apoptosis in the malignant clones. Those insights, in turn, may point the way to novel therapeutic approaches.

KIT Mutations in GIST

Most gastrointestinal stromal tumors (GISTs) contain oncogenic KIT or PDGFRA receptor tyrosine kinase mutations. These rare neoplasms are remarkably sensitive to the KIT and PDGFRA kinase inhibitors imatinib (also known as Gleevec) and sunitinib (Sutent), which have recently been approved as the standard therapeutic courses for patients with inoperable GIST. However, most GIST patients eventually develop clinical resistance to imatinib and sunitinib. Imatinib and sunitinib resistance generally result from secondary mutations in the KIT and/or PDGFRA kinase domains. Preclinical studies suggest that imatinib and sunitinib resistant mutations can be treated using more potent kinase inhibitors, such as nilotinib, which inactivate the mutant kinase proteins. Alternately, the mutant kinase proteins can be targeted using HSP90 inhibitors, which result in degradation of activated KIT and/or PDGFRA, or using KIT transcriptional repressors, such as flavopiridol.