Efficacy and safety of imatinib mesylate in advanced gastrointestinal stromal tumors

Overexpression of c-kit protein is an infrequent event in small cell carcinomas of the uterine cervix

Primary small cell carcinomas of the uterine cervix are uncommon but highly aggressive malignancies. The recent observations that c-kit proto-oncogene, a tyrosine kinase, is overexpressed in small cell lung cancers and that advanced c-kit-expressing gastrointestinal stromal tumors were successfully treated with a selective tyrosine kinase inhibitor STI-571 (Gleevec, imatinib mesylate) prompted us to investigate c-kit protein expression in cervical small cell carcinomas. Using a polyclonal antibody against c-kit protein (CD117), our immunohistochemical studies demonstrated a cytoplasmic staining in six of 22 cases (27%) of cervical small cell carcinoma. However, in five of these c-kit-positive cases, the immunoreactivity was focal and/or weak. Only one case (5%) exhibited a strong and diffuse staining pattern comparable to that seen in gastrointestinal stromal tumors. This was in contrast to small cell lung cancers where a positive staining for c-kit was observed in nine of 14 cases (64%) included in the study for comparison. Among them, five (36%) exhibited a strong and diffuse staining pattern. These results indicate that overexpression of c-kit protein is an infrequent event in small cell carcinomas of the uterine cervix. In comparison with small cell lung cancers, the findings presented in this report may reflect the difference in etiopathogenetic mechanisms underlying these two types of small cell carcinomas.

Toxidermie lichénoïde à l’imatinib (Glivec®)

INTRODUCTION

Imatinib (Glivec) is a new therapeutic molecule used for the treatment of chronic myeloid leukemia. Cutaneous side effects with this treatment are common but lichenoid drug eruption is exceptional. We report the first case with profuse cutaneous lichen.

CASE REPORT

A 52 year-old woman presented with a 5-year history of chronic myeloid leukemia. The different chemotherapies had failed (persisting polyadenopathies and splenomegalia). She was treated with imatinib (400 mg/day). Two months after the beginning of this treatment a disseminated cutaneous eruption appeared on the trunk, legs, arms and face without mucosal involvement and composed of dark purple, prurigenous, papules suggestive of lichen planus. The cutaneous biopsy confirmed the diagnosis of lichen planus. Suspension of the drug led to the complete regression of the eruption, without any other local treatment, within 2 months. Reintroduction of the drug led to the recurrence of the lesions.

DISCUSSION

Cutaneous reactions to imatinib are common and occur in 11 to 67 p. 100 of patients depending on the series. More severe cutaneous reactions have been described: exfoliating dermatites, generalized pustulosis, epidermal necrolysis. The aspect of profuse lichenoid eruption of the skin and the correlation with cutaneous lesions clinically and histologically evocative of lichen planus has not been described other than an isolated buccal involvement in a 72 year-old woman. In our patient, study of the imputability criteria is in favor of imatinib's responsibility.

C-KIT EXPRESSION IN SARCOMATOID RENAL CELL CARCINOMA: POTENTIAL THERAPY WITH IMATINIB

PURPOSE

Sarcomatoid (S) renal cell carcinoma (RCC) is an uncommon subtype of RCC with a poor prognosis because of its local aggressiveness and high metastatic rate. Currently, there is no specific, effective treatment for it. A relatively nontoxic tyrosine kinase inhibitor, imatinib (STI-571) has been approved as a target therapy in neoplasms that express c-Kit. We investigated c-Kit expression in this type of tumor, which to our knowledge has not been previously described.

MATERIALS AND METHODS

We reviewed 215 cases of RCC diagnosed at our department from 1995 to 2002. Of the cases 20 (9.3%) were SRCC. Formalin fixed, paraffin embedded material was available in 19 cases. We performed immunohistochemical staining against c-Kit using rabbit polyclonal antihuman antibody (CD117, Dako Corp., Carpinteria, California), diluted 1:100. Its expression was evaluated in the epithelial and the spindle components.

RESULTS

Two of the 20 SRCC cases (10%) showed no epithelial differentiation. The epithelial component was conventional RCC in 10 cases (50%), papillary RCC in 5 (25%) and chromophobe RCC in 3 (15%). A total of 16 cases (80%) presented at an advanced stage at diagnosis, namely T3 or T4 and/or metastatic disease. Immunohistochemical study showed positivity in the epithelial component only in the 3 chromophobe SRCCs. The sarcomatoid component was positive for c-Kit in 18 cases (94.7%).

CONCLUSIONS

High c-Kit expression in SRCC in our series and the existence of a target therapy, imatinib (STI-571), against cells that express this receptor open the possibility of using this treatment for these tumors, especially in cases of advanced disease.

Yersinia infection mimicking recurrence of gastrointestinal stromal tumor

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. So far, surgical resection has been the only curative treatment, but new options became available with the application of imatinib (Glivec) as a specific molecular inhibitor. Even after complete resection, GISTs have a high rate of recurrence and disease-linked mortality. Here we report on the case of a clinically well 57-year-old woman who presented to us 3 years after resection of a GIST of the small intestine. Abdominal ultrasound and CT scan showed intestinal wall thickening in the area of anastomosis and mesenteric lymphadenopathy, suggesting a recurrence of the primary GIST. However, serological testing was positive for yersinia antibodies. Surgical exploration revealed an asymptomatic infection with Yersinia enterocolitica serotype O9, proven by positive culture and histology, which showed no evidence of malignancy. Prognostic variables for GIST as well as diagnostic measures and limitations for yersiniosis are discussed. In the end, only surgical exploration and histological analysis could establish the final diagnosis. In conclusion, GISTs have a high likelihood of recurrence even after complete resection, but an asymptomatic infection such as yersiniosis must be considered as a differential diagnosis to GIST recurrence.

A phase II study of ET-743/trabectedin (`Yondelis') for patients with advanced gastrointestinal stromal tumours

Primary or secondary resistance to imatinib may occur in patients with gastrointestinal stromal tumours (GISTs) while these tumours have repeatedly been shown to be highly resistant to conventional doxorubicin- and ifosfamide-containing regimens. The investigation of new drugs is therefore warranted in GIST. A phase II study was conducted between May 1999 and November 2000 in eight centres of the EORTC STBSG group to establish the efficacy and safety of ET743 ('Yondelis') in GIST previously untreated with cytotoxic chemotherapy before the imatinib era. ET-743 was given was given at 1.5 mg/m(2) per course as a 24-h continuous intravenous infusion every 3 weeks. Twenty-eight patients were included, 16 males and 12 females. Median age was 54 years (range 25-73 years). Median performance status was 0 (range 0-1). 17 (63%), 4 (12%) and 7 (25%) patients, received 0-2, 3-5, and > or = 6 courses of ET-743, respectively. The best response was stable disease in 9 (33%) patients, and disease progression in 18 patients (67%), with a median time to disease progression and overall survival of 51 days and 589 days, respectively. The treatment was well tolerated: there were grades 3-4 neutropenia, thrombocytopenia, and transaminase increases in 13 (48%), 1 (4%) and 16 (59%) patients, respectively. There were no toxic deaths. ET-743 at this dose and schedule is not an effective treatment for advanced GIST.

Imatinib targets other than bcr/abl and their clinical relevance in myeloid disorders

Imatinib mesylate is a small molecule drug that in vitro inhibits the Abelson (Abl), Arg (abl-related gene), stem cell factor receptor (Kit), and platelet-derived growth factor receptor A and B (PDGFRA and PDGFRB) tyrosine kinases. The drug has acquired therapeutic relevance because of similar inhibitory activity against certain activating mutations of these molecular targets. The archetypical disease in this regard is chronic myeloid leukemia, where abl is constitutively activated by fusion with the bcr gene (bcr/abl). Similarly, the drug has now been shown to display equally impressive therapeutic activity in eosinophilia-associated chronic myeloproliferative disorders that are characterized by activating mutations of either the PDGFRB or the PDGFRA gene. The former usually results from translocations involving chromosome 5q31-33, and the latter usually results from an interstitial deletion involving chromosome 4q12 (FIP1L1-PDGFRA). In contrast, imatinib is ineffective, in vitro and in vivo, against the mastocytosis-associated c-kit D816V mutation. However, wild-type and other c-kit mutations might be vulnerable to the drug, as has been the case in gastrointestinal stomal cell tumors. Imatinib is considered investigational for the treatment of hematologic malignancies without a defined molecular drug target, such as polycythemia vera, myelofibrosis with myeloid metaplasia, and acute myeloid leukemia.

Imatinib Mesylate Efficiently Achieves Therapeutic Intratumor Concentrations in Vivo but Has Limited Activity in a Xenograft Model of Small Cell Lung Cancer

PURPOSE

Despite recent advances in cancer therapy, long-term survival in small cell lung cancer (SCLC) remains uncommon, underscoring the need for novel therapeutic approaches. Previous studies have identified constitutive expression of the receptor tyrosine kinase, c-Kit, and its ligand, stem cell factor, in a substantial proportion of SCLC specimens. The purpose of this study was to determine whether imatinib mesylate, an inhibitor of c-Kit, could achieve therapeutic concentrations in tumors and in brain (a frequent site of SCLC metastasis) and interfere with SCLC tumor growth in vivo.

EXPERIMENTAL DESIGN

Human SCLC tumor cell lines with constitutive c-kit expression and tyrosine phosphorylation (NCI-H209, NCI-H526, and NCI-H1607) were used to establish SCLC tumor xenografts in NCr nude (nu/nu)-immunodeficient mice. SCLC tumor-bearing mice were randomly assigned to imatinib or control (water) administered twice a day by oral gavage. Imatinib concentrations in plasma, brain, and tumor were quantitated and correlated with tumor response.

RESULTS

Therapeutic concentrations of imatinib were achieved in plasma and tumor xenografts but not in the brain. Imatinib blocked the constitutive activation of c-kit in SCLC tumor cell lines in vitro but had a negligible effect on SCLC xenograft growth in vivo.

CONCLUSIONS

Orally administered imatinib rapidly reaches therapeutic concentrations in SCLC xenografts, suggesting the feasibility of combining imatinib with other novel or traditional chemotherapeutic agents in SCLC or other solid tumors. The c-Kit signaling pathway does not appear to play a critical role in SCLC proliferation and viability in vivo, however, suggesting that imatinib is unlikely to be effective as monotherapy for SCLC.

Use of c-KIT/PDGFRA mutational analysis to predict the clinical response to imatinib in patients with advanced gastrointestinal stromal tumours entered on phase I and II studies of the EORTC Soft Tissue and Bone Sarcoma Group

Previous studies have shown that activating mutations of c-KIT/PDGFRA, potential therapeutic targets for imatinib mesylate, are implicated in the pathophysiology of gastrointestinal stromal tumours (GISTs). In this study, GISTs from 37 patients enrolled in an European Organisation for Research and Treatment of Cancer (EORTC) phase I/II clinical study of imatinib were examined for mutations of c-KIT/PDGFRA in order to explore whether the mutational status of the tumour predicts the clinical response to therapy. Mutations were screened by denaturing high-pressure liquid chromatography (DHPLC) and characterised by bi-directional DNA sequencing. Activating mutations of c-KIT or PDGFRA were found in 29 (78%) and 2 (6%) GISTs, respectively. Most c-KIT mutations involved exon 11 (n=24; 83%), all but one being an in-frame deletion; no isolated point mutations were found. The other c-KIT mutations included exon 9 AY 502-503 duplication (n=4; 14%) and exon 13 Lys-->Glu(642) missense mutation (n=1; 3%). Two tumours with no detectable c-KIT mutations demonstrated PDGFRA Asp-->Glu(842) amino acid substitutions. Patients with GISTs harbouring exon 11 mutations were more likely to achieve a partial response (PR) on imatinib therapy (83%) than all of the others (23%). The overall survival and progression-free survival rates for the entire group at 106 weeks were 78.3% and 46.9%, respectively. Based on a Kaplan-Meier analysis, patients with GISTs harbouring c-KIT mutations had longer median survival times and were less likely to progress than the other patients. These findings indicate that the mutational status of the c-KIT/PDGFRA oncoproteins could be useful to predict the clinical response of patients imatinib therapy.

Resistance to imatinib (Glivec): update on clinical mechanisms

Imatinib mesylate, an orally administered 2-phenylaminopyrimidine derivative that inhibits BCR/ABL tyrosine kinase activity, has shown great promise in the treatment of chronic myelogenous leukemia (CML). This small molecule, tyrosine kinase inhibitor, has also been shown to be effective against metastatic gastrointestinal stromal tumors (GISTs) expressing the stem cell factor (SCF) receptor kit. However, the threat of resistance in patients has prompted investigators to uncover the mechanisms whereby malignant cells develop resistance to imatinib, and has also led to the establishment of strategies designed to over-ride imatinib resistance. Here, we provide a comprehensive overview of the effectiveness of imatinib in the treatment of chronic, accelerated and blast crisis-phase CML, Philadelphia chromosome-positive (Ph+) acute lymphoid leukemia (ALL) and metastatic GIST. Established mechanisms of resistance to imatinib are discussed, as are novel therapeutic approaches to improving drug responsiveness by reversing development of imatinib resistance in patients.

Implications of PET based molecular imaging on the current and future practice of medicine

The last quarter century has witnessed the introduction of a variety of powerful techniques that have allowed visualization of organ structure and function with exquisite detail. This in turn has brought about a true revolution in the day-to-day practice of medicine. Structural imaging with x-ray computerized tomography and magnetic resonance imaging has added tremendously to many areas of medicine, including preoperative evaluation of patients. Many surgical procedures have been replaced by minimally invasive techniques, which have become a reality only because of the availability of modern imaging modalities. However, despite such accomplishments, structural imaging is quite insensitive for detecting early disease in which there often are no gross structural alterations in organ anatomy. Therefore, these modalities should be complemented by methodologies that can detect abnormalities at the molecular and cellular levels. The introduction of [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET) in 1976 as a molecular imaging technique clearly has shown the power of this approach for treating a multitude of serious disorders. The impact of FDG-PET has been particularly impressive in patients with cancer diagnosis, for whom it has become important in staging, monitoring response to treatment, and detecting recurrence. In this review, we emphasize the role of FDG-PET in the assessment of central nervous system maladies, malignant neoplastic processes, infectious and inflammatory diseases, and cardiovascular disorders. New radiotracers are being developed and promise to expand further the list of indications for PET. These include novel tracers for cancer diagnosis and treatment capable of detecting hypoxia and angiogenesis. Prospects for developing new tracers for imaging other organ diseases also appear very promising.

Female adnexal tumor of probable wolffian origin: a clinicopathological case report and a possible new treatment

Female adnexal tumors of probable wolffian origin (FATWOs) are rare tumors arising in the broad ligament from the remnants of the mesonephric duct. We report a case of recurrent disease. A 15-year-old girl who presented with a painful pelvic mass underwent a laparotomy with tumor resection. Pathology findings confirmed a FATWO. The tumor recurred within 2 years and was treated with multiple chemotherapy regimens, including a platinum-based drug, and surgery for progressive disease. The tumor was positive for c-kit oncogene (CD 117). Gleevac therapy, a tyrosine kinase inhibitor, was prescribed, and she developed severe persistent lower abdominal pain 2 months later. She underwent a hysterectomy and debulking of retroperitoneal masses. Pathology showed evidence of tumor necrosis, suggesting a possible beneficial effect, and she was recommenced on Gleevac in an effort to prevent recurrences. She is currently asymptomatic, without evidence of disease 10 months after surgery, continuing on Gleevac therapy. FATWOs are very rare tumors. Most cases are benign but have the potential to recur and metastasize. There is limited knowledge about the optimal treatment for this neoplasm. Our patient's favorable response to Gleevac therapy supports the concept of targeted molecular therapy in patients with c-kit-positive FATWO tumors.

Inhibition of fibroblast growth factor receptor 3 induces differentiation and apoptosis in t(4;14) myeloma

We have previously shown that dysregulation of fibroblast growth factor receptor 3 (FGFR3) by the t(4;14) translocation is a primary event in multiple myeloma (MM) and that activating mutations of FGFR3 are acquired in some cases. We describe here inhibition of wild-type (WT) and constitutively activated mutant FGFR3 autophosphorylation by the small molecule inhibitor, PD173074. Inhibition of FGFR3 in human myeloma cell lines was associated with decreased viability and tumor cell growth arrest. Further, morphologic, phenotypic, and functional changes typical of plasma cell (PC) differentiation, including increase in light-chain secretion and expression of CD31, were observed and this was followed by apoptosis. Finally, using a mouse model of FGFR3 myeloma, we demonstrate a delay in tumor progression and prolonged survival of mice treated with PD173074. These results indicate that inhibition of FGFR3, even in advanced disease associated with multiple genetic changes, may allow the cell to complete its developmental program and render it sensitive to apoptotic signals. In addition, this represents the validation of a therapeutic target in MM that may benefit patients who have a very poor prognosis with currently available treatments. (Blood. 2004;103:3521-3528)

Imatinib Attenuates Diabetes-Associated Atherosclerosis

OBJECTIVE

Diabetes is associated with accelerated atherosclerosis, the major factor contributing to increased mortality and morbidity in the diabetic population. The molecular mechanisms by which diabetes promotes atherosclerosis are not fully understood. Platelet-derived growth factor has been shown to play a major role in the pathology of vascular diseases, but whether it plays a role in atherosclerosis associated with diabetes remains unknown. The aims of this study were to assess whether platelet-derived growth factor-dependent pathways are involved in the development of diabetes-induced atherosclerosis and to determine the effects of platelet-derived growth factor receptor antagonism on this disorder.

METHODS AND RESULTS

Diabetes was induced by injection of streptozotocin in 6-week-old apolipoprotein E knockout mice. Diabetic animals received treatment with a tyrosine kinase inhibitor that inhibits platelet-derived growth factor action, imatinib (STI-571, 10 mg/kg per day), or no treatment for 20 weeks. Nondiabetic apolipoprotein E knockout mice served as controls. Induction of diabetes was associated with a 5-fold increase in plaque area in association with an increase in aortic platelet-derived growth factor-B expression and platelet-derived growth factor-beta receptor phosphorylation as well as other prosclerotic and proinflammatory cytokines. Imatinib treatment prevented the development of atherosclerotic lesions and diabetes-induced inflammatory cytokine overexpression in the aorta.

CONCLUSIONS

Tyrosine kinase inhibition with imatinib appears to be a novel therapeutic option to retard the development of atherosclerosis, specifically in the context of diabetes.

Targeting c-Kit mutations: basic science to novel therapies

The Kit receptor tyrosine kinase is a transmembrane receptor that is expressed in a variety of different tissues and mediates pleiotropic biological effects through its ligand stem cell factor (SCF). Sporadic mutations of Kit as well as autocrine/paracrine activation mechanisms of the SCF/Kit pathway have been implicated in a variety of malignancies, where its primary contribution to metastases is in enhancing tumor growth and reducing apoptosis. For example, Kit is frequently mutated and activated in gastrointestinal stromal tumors (GISTs) and there is ligand-mediated activation of Kit in some lung cancers. Kit is a convenient target in Kit-induced tumors and inhibition of this receptor with the small molecule drug Gleevec (imatinib mesylate, STI571) in GIST has shown dramatic efficacy. Unfortunately, past experience has demonstrated that chemotherapy of cancers with a single drug often leads to resistance of the cancer. Further understanding of the molecular mechanisms underlying Kit-mediated transformation is therefore important and may lead to the identification of further novel drug targets. These Kit-specific signaling pathways may then be targeted to overcome potential drug resistance. This review will focus on our understanding of the molecular mechanisms involved in transformation by Kit. The potential mechanisms by which Kit induces cellular transformation are described. We will also discuss the role and expression of Kit in various malignancies. Ultimately, the understanding of c-Kit biology, biochemistry, and mutational analysis will lead to better therapeutics.

Imatinib therapy for hypereosinophilic syndrome and eosinophilia-associated myeloproliferative disorders

A pathogenetic mutation, FIP1L1-PDGFRA, that results from an interstitial chromosome 4q12 deletion, leads to a constitutive activation of the platelet-derived growth factor receptor-alpha (PDGFRA) tyrosine kinase as well as a disease phenotype that mimics both the hypereosinophilic syndrome (HES) and systemic mast cell disease associated with eosinophilia (SMCD-eos). Complete remissions, in response to treatment with low-dose imatinib mesylate (100 mg/day or less) have now been documented in all cases of FIP1L1-PDGFRA(+) eosinophilic disorder as well as other eosinophilic disorders that carry activation mutations of the PDGFRB gene that is located on chromosome 5q33. Furthermore, response to therapy has been rapid (within days) and durable. Interestingly, imatinib mesylate treatment, at a higher dose level (400 mg/day), might induce either partial or short-lived complete remissions in HES that is not associated with the aforementioned PDGFR mutations. These observations make it necessary to re-examine current disease classification and treatment algorithms in eosinophilic disorders.

Advances in molecular carcinogenesis: current and future use of mouse models to screen and validate molecularly targeted anticancer drugs

Survival of patients with advanced solid tumors has not significantly improved over the past 30 years. Although molecularly targeted anticancer drugs offer promise, few drugs make it through the end of the Food and Drug Administration approval process. Animal models that more closely resemble human carcinogenesis may bridge the gap between preclinical success and benefits for patients. We discuss pros and cons of several mouse models, including genetically engineered mice that each represent different aspects of human cancer, and the screening of targeted drugs in these models.

Targeting of the VHL-hypoxia-inducible factor-hypoxia-induced gene pathway for renal cell carcinoma therapy

Treatment of advanced renal cancer has made little progress in the past 30 yr. Most clinical efforts have incorporated cytokine-based therapy. The presumption has been that the cytokines may trigger a host immune response against the renal cancer. Only IFN-alpha and high-dose IL-2 seemed to have positive effects on patient outcomes. IFN has prolonged the lives of patients by a few months, and high-dose IL-2 is capable of inducing very prolonged remissions (>5 yr) for a small number of patients. Nephrectomy in the presence of metastatic disease has been established as an effective procedure for select patients, providing palliation and prolonging survival. Finally, enthusiasm has focused on the use of nonmyeloablative allogeneic stem cell transplantation and donor leukocyte infusion for the induction of graft versus tumor effects. Early results are both provocative and promising. A number of agents that target the critical gene products downstream from pVHL and hypoxia-inducible factor-1, such as vascular endothelial growth factor, PDGF, EGF receptor, and TGF-alpha, have recently become available. The new agents are capable of inhibiting specific cellular targets, and the biologic characteristics of clear cell carcinoma of the kidney support their application. If the correct targets are carefully selected for inhibition in tumors in which the targets are present (clear cell histologic features and loss of VHL expression), then results should resemble those others have observed with targeted therapy, such as the use of STI-571 (Gleevec; Novartis Pharmaceuticals, East Hanover, NJ) for treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors or anti-HER2/neu (Herceptin; Genentech, South San Francisco, CA) for treatment of breast cancer.

CD44 loss in gastric stromal tumors as a prognostic marker

BACKGROUND

The adhesion molecule CD44 (CD44s; CD44H) and its isoforms (CD44v3-6 and v9) are preferentially expressed by different cell types. These transmembrane glycoproteins are involved in cell-cell and cell-matrix interactions and in cell trafficking and, thus, may play a role in tumor metastasis and/or local invasion. The expression pattern of CD44s and variant isoforms, particularly CD44v6 and CD44v9, of some neoplasms, including soft tissue tumors, correlates with clinical course and outcome. The clinical behavior of gastrointestinal stromal tumors (GIST) is site specific; however, other reliable predictors of clinical outcome have not been identified. Thus, the prognostic value of CD44s and isoform expression in GIST were evaluated by immunohistochemistry of tissue microarrays.

DESIGN

Paraffin-embedded formalin-fixed tissue cores (129: 103 GIST and 26 normal stomach smooth muscle) from 33 patients with clinical outcome data were collected and used for the construction of the tissue microarrays. One to five tissue cores from each patient specimen were evaluated (mean = 3 tissue cores/patient). Array slides were stained with anti-CD44s (CD44H) and with antibodies to v3, v4, v5, v6, and v9 isomers. CD44s and isoform expression and staining intensity were scored semiquantitatively without knowledge of patient identity or outcome: 0 = no; 1 = weak; 2 = moderate; 3 = moderate to strong; 4 = strong. The scores of multiple cores from the same GIST were averaged; the nonneoplastic smooth muscle was similarly graded. CD44s and isoform expression and intensity were compared with outcome.

RESULTS

The 33 patients with gastric GIST, 0.8 to 30 cm in size, were followed for 1 to 111 months with a median follow-up of 7 months (mean 17.5 months). The overall median survival was 25 months. Nine of the 33 (27%) patients had metastases, 9 (27%) had recurrent disease, and 9 (27%) died of disease (9-111 months; mean 39 months; median 23 months). All 18 patients with GIST CD44s expression > 2+ were alive at last follow-up (1-62 months; median 3.5 months; mean 11 months). More than half (53%) of patients with GIST CD44s expression < or = 2+ died (9-111 months; median 23 months; mean 38 months); the median follow-up of the surviving patients with CD44 expression < or = 2 was 5 months (2-22 months; mean 6.5 months; log rank P = 0.07). The majority of tumors were variably positive CD44v3 and CD44v4, but there was minimal staining (number of cases and/or expression level) with antibodies directed against the v5, v6, and v9 isomers.

CONCLUSION

These preliminary results suggest that although gastric GISTs variably express CD44s and variants, only the expression of CD44s correlates with clinical outcome with loss of CD44s positivity correlating with poor clinical outcome.

The Met kinase inhibitor SU11274 exhibits a selective inhibition pattern toward different receptor mutated variants

Point mutations constitute a major mode of oncogenic activation of the Met receptor tyrosine kinase. Met is aberrantly activated in many types of human malignancies and its deregulated activity is correlated with aggressive tumor traits such as abnormal proliferation and survival, leading to tumor growth, local invasion and metastasis. Here we report that the Met kinase inhibitor SU11274 differentially affects the kinase activity and subsequent signaling of various mutant forms of Met. Two Met variants tested, M1268T and H1112Y, were potently inhibited by 2 microM SU11274, while two other variants, L1213V and Y1248H, remained resistant under similar experimental conditions. Inhibition of the kinase altered cell proliferation, morphology and motility, while cells containing resistant mutants appeared unaffected by the compound. The basis for the sensitivity or resistance to SU11274 is discussed in terms of the position of the mutations predicted from a homology model.

Determination of imatinib (Gleevec®) in human plasma by solid-phase extraction–liquid chromatography–ultraviolet absorbance detection

A sensitive HPLC method has been developed for the assay of imatinib in human plasma, by off-line solid-phase extraction followed by HPLC coupled with UV-Diode Array Detection. Plasma (750 microl), with clozapine added as internal standard, is diluted 3 + 1 with water and subjected to a solid-phase extraction on a C18 cartridge. After matrix components elimination with 2000 microl of water (in two aliquots of 1000 microl), imatinib is eluted with 3 x 500 microl MeOH. The resulting eluate is evaporated under nitrogen at room temperature and is reconstituted in 180 microl 50% methanol. A 50 microl volume is injected onto a Nucleosil 100-5 microm C18 AB column. Imatinib is analyzed using a gradient elution program with solvent mixture constituted of methanol and water containing both 0.05% ammonium acetate. Imatinib is detected by UV at 261 nm. The calibration curves are linear between 0.1 and 10 microg/ml. The limit of quantification and detection are 0.05 and 0.01 microg/ml, respectively. The mean absolute recovery of imatinib is 96%. The method is precise with mean inter-day CVs within 1.1-2.4%, and accurate (range of inter-day deviations -0.6 to +0.7%). The method has been validated and is currently being applied in a clinical study assessing the imatinib plasma concentration variability in a population of chronic myeloid leukemia- and gastro-intestinal stromal tumor-patients.

Tyrosine kinase receptors as attractive targets of cancer therapy

Receptor tyrosine kinases (RTKs) are the main mediators of the signaling network that transmit extracellular signals into the cell, and control cellular differentiation and proliferation. Recent and rapid advances in our understanding of cellular signaling by receptor tyrosine kinases, in normal and malignant cells, have brought to light the potential of RTKs as selective anti-cancer targets. Their activity is normally tightly controlled and regulated. Overexpression of RTK proteins or functional alterations caused by mutations in the corresponding genes or abnormal stimulation by autocrine growth factor loops contribute to constitutive RTK signaling, resulting in dysregulated cell growth and cancer. The mechanisms of uncontrolled RTK signaling that leads to cancer has provided the rationale for anti-RTK drug development. Herceptin, Gleevec, and Iressa are the first examples of drugs which have successfully translated basic research on oncogenes into cancer therapeutics. RTKs can be viewed as multifunctional targets, and strategies towards the prevention and inhibition of RTK signaling include antibodies, antagonist ligands, small molecule inhibitors of protein kinase activity, and inhibitors of protein-protein interactions. Progresses in the field of rational drug design and computational chemistry will vastly benefit from the availability of increasing structural knowledge of both the kinase domains and the ligand-binding sites of these receptors.

Update on the management of connective tissue malignancies

Approximately 11,000 new cases of connective tissue malignancies are anticipated in 2004. These diseases can be divided into soft-tissue sarcomas, sarcomas of bone, and gastrointestinal stromal tumors. Optimal management of these diseases requires a multidisciplinary team with expertise in surgery, pathology, radiotherapy, and chemotherapy. Over half of patients with stage III soft tissue and bone sarcomas are cured, as are some patients with metastatic disease. Imatinib mesylate has been an important advance in the treatment of gastrointestinal stromal tumors.

Complete remission of TEL-PDGFRB-induced myeloproliferative disease in mice by receptor tyrosine kinase inhibitor SU11657

The TEL-PDGFRB fusion oncogene is associated with chronic myelomonocytic leukemia (CMML) and results in the expression of a constitutively active tyrosine kinase. SU11657 is a multitargeted selective inhibitor of class III/V receptor tyrosine kinases, including the platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) receptors KIT and FLT3. SU11657 inhibited TEL/PDGFbetaR kinase activity at nanomolar concentrations and inhibited TELPDGFRB-mediated factor-independent growth in myeloblastic 32D cells. Daily oral administration of SU11657 at 40 mg/kg suppressed myeloproliferation and significantly prolonged survival in TELPDGFRB mice treated prior to disease development, as well as in those with large tumor burdens. Our findings suggest that SU11657 or similar agents may have therapeutic potential in humans with hematologic malignancies expressing PDGFR fusion oncogenes.

Molecular response of gastrointestinal stromal tumour after treatment with tyrosine kinase inhibitor imatinib mesylate

Bleeding from the tumour site is not uncommon during the treatment of gastrointestinal stromal tumours with imatinib mesylate. It might represent an early reaction of highly vascularised tumour tissue to receptor blockade. Although often requiring emergency surgery, this is not necessarily a deleterious sign. Slow tumour regression and cystic tissue alteration may follow. Using immunohistochemistry and consecutive resection specimens, it was shown that the number of mitoses decreased significantly and MIB-1 as a marker of cell proliferation could no longer be detected. In the few tumour cells still present, the magnitude of expression of the pathognomonic marker CD117 remained unchanged. Decreases in the size of tumours responding to imatinib mesylate cannot be expected to meet the World Health Organisation or RECIST (response evaluation criteria in solid tumours) criteria. This underlines the necessity of functional imaging by positron emission tomography, contrast enhanced magnetic resonance imaging, or magnetic resonance spectroscopy to assess the response to treatment.

Gastrointestinal stromal tumors (GISTs)

PURPOSE OF REVIEW

Gastrointestinal stromal tumors (GISTs) have recently been the subject of considerable clinical and experimental interest. This focus is based on the recognition that GISTs characteristically have uncontrolled activation of the KIT protein, a transmembrane tyrosine kinase receptor involved in cell survival, development, and proliferation. The clinical application of imatinib mesylate, a selective inhibitor of the KIT kinase activity, has provided a novel molecularly targeted therapy for these tumors. This review summarizes publications from the last year regarding these tumors.

RECENT FINDINGS

Recent studies have focused on imaging, the identification of prognostic factors and molecular events, and the role of systemic therapy in the treatment of these tumors. Emerging data suggest that the combination of endoscopic ultrasound and fine-needle aspiration analysis for KIT expression may be useful in separating these lesions from other submucosal lesions of the gastrointestinal tract. The benefits and limitations of computed tomography and positron emission tomography in identifying, staging, and evaluating the response to therapy of these lesions have been more clearly defined. Although tumor size and the number of mitoses remain the best prognostic markers, several studies reported provocative data using other markers such as Ki-67, p53, and alterations in p16. Mutational analysis of the KIT oncoprotein continues to be the subject of considerable interest in relation to both prognosis and resistance to therapy. Finally, a series of new studies have confirmed the benefits and better defined the results of therapy with imatinib mesylate. There is increasing interest in expanding the role of this agent into the adjuvant setting and in combining such therapy with reoperation for responsive disease.

SUMMARY

In the past year there have been significant developments in our understanding of GISTs and their response to therapy. Many questions remain unanswered and new issues have arisen as the benefits of imatinib mesylate therapy are revealed. There is considerable optimism that the targeted molecular approach being applied to the treatment of GISTs will serve as a model for the development of similar approaches to other more common tumors.

KIT mutations are common in testicular seminomas

Expression of KIT tyrosine kinase is critical for normal germ cell development and is observed in the majority of seminomas. Activating mutations in KIT are common in gastrointestinal stromal tumors and mastocytosis. In this study we examined the frequency and spectrum of KIT mutations in 54 testicular seminomas, 1 ovarian dysgerminoma and 37 non-seminomatous germ cell tumors (NSGCT). Fourteen seminomas (25.9%) contained exon 17 point mutations including D816V (6 cases), D816H (3 cases), Y823D (2 cases), and single examples of Y823C, N822K, and T801I. No KIT mutations were found in the ovarian dysgerminoma or the NSGCTs. In transient transfection assays, mutant isoforms D816V, D816H, Y823D, and N822K were constitutively phosphorylated in the absence of the natural ligand for KIT, stem cell factor (SCF). In contrast, activation of T801I and wild-type KIT required SCF. Mutants N822K and Y823D were inhibited by imatinib mesylate (Gleevec, previously STI571) whereas D816V and D816H were both resistant to imatinib mesylate. Biochemical evidence of KIT activation, as assessed by KIT phosphorylation and KIT association with phosphatidylinositol (PI) 3-kinase in tumor cell lysates, was largely confined to seminomas with a genomic KIT mutation. These findings suggest that activating KIT mutations may contribute to tumorigenesis in a subset of seminomas, but are not involved in NSGCT.

Cancer treatment with kinase inhibitors: what have we learnt from imatinib?

Over the past few years, a number of anticancer drugs have been developed that specifically target kinases known to be oncogenic. The leading drug in this area is imatinib mesylate, which targets ABL, KIT and PDGFR. It has been remarkably effective in the treatment of chronic myeloid leukaemia, although resistance remains a significant problem. From the imatinib experience in this setting, we present some principles of kinase inhibition that may have more general applicability in targeted anticancer therapy. It is clear that the identification of appropriate targets (activated kinases) and monitoring levels of response (to recognise emerging resistance) are essential to optimise clinical management.

Pleomorphic Characteristics of a Germ-Line KIT Mutation in a Large Kindred with Gastrointestinal Stromal Tumors, Hyperpigmentation, and Dysphagia

PURPOSE

Somatic mutations that result in the activation of the growth factor receptor KIT are commonly found in gastrointestinal stromal tumors (GISTs). Six families have been reported in which a germ-line mutation in KIT is associated with an autosomal dominant predisposition to the development of GISTs. Hyperpigmentation, urticaria pigmentosa, and dysphagia have been described in some, but not all, families. Preliminary correlations between the site of mutation and the clinical phenotype have been proposed, but the strength of these associations is not defined.

DESIGN

A large kindred with multiple GISTs, hyperpigmentation, and dysphagia was identified after the index case presented with multiple GISTs. A germ-line mutation in KIT (W557R) was identified in an affected cousin, after which a large family meeting was held and testing offered. Clinical data were obtained by interview and, whenever possible, medical record documentation.

RESULTS

To date, 19 individuals have been tested, and the mutation has been shown to cosegregate with the syndrome. The phenotypic expression, however, is variable. GISTs, often presenting as upper gastrointestinal bleeding, and hyperpigmentation are common, but not diagnosed in all documented or obligate carriers. Dysphagia is a less prevalent complaint. The diagnosis of GISTs appears to be made at a younger age in more recent generations. Metastatic disease is uncommon.

CONCLUSIONS

A germ-line mutation in KIT resulting in an amino acid substitution in the juxtamembrane region is associated with a syndrome of GIST, hyperpigmentation, and dysphagia, although the prominence of each component varies.

Combination of rapamycin and protein tyrosine kinase (PTK) inhibitors for the treatment of leukemias caused by oncogenic PTKs

Abnormal protein tyrosine kinases (PTKs) cause many human leukemias. For example, BCR/ABL causes chronic myelogenous leukemia (CML), whereas FLT3 mutations contribute to the pathogenesis of acute myelogenous leukemia. The ABL inhibitor Imatinib (Gleevec, STI571) has remarkable efficacy for treating chronic phase CML, and FLT3 inhibitors (e.g., PKC412) show similar promise in preclinical studies. However, resistance to PTK inhibitors is a major emerging problem that may limit long-term therapeutic efficacy. Development of rational combination therapies will probably be required to effect cures of these and other neoplastic disorders. Here, we report that the mTOR inhibitor rapamycin synergizes with Imatinib against BCR/ABL-transformed myeloid and lymphoid cells and increases survival in a murine CML model. Rapamycin/Imatinib combinations also inhibit Imatinib-resistant mutants of BCR/ABL, and rapamycin plus PKC412 synergistically inhibits cells expressing PKC412-sensitive or -resistant leukemogenic FLT3 mutants. Biochemical analyses raise the possibility that inhibition of 4E-BP1 phosphorylation may be particularly important for the synergistic effects of PTK inhibitor/rapamycin combinations. Addition of a mitogen-activated protein kinase kinase inhibitor to rapamycin or rapamycin plus PTK inhibitor further increases efficacy. Our results suggest that simultaneous targeting of more than one signaling pathway required by leukemogenic PTKs may improve the treatment of primary and relapsed CML and/or acute myelogenous leukemia caused by FLT3 mutations. Similar strategies may be useful for treating solid tumors associated with mutant and/or overexpressed PTKs.

Tyrosine kinase inhibitor as a therapeutic drug for chronic myelogenous leukemia and gastrointestinal stromal tumor

The Philadelphia chromosome found in leukemia cells of chronic myelogenous leukemia (CML) patients is produced by translocation between chromosomes 9 and 22, resulting in expression of a chimera protein of Bcr and Abl kinase in the cytoplasm. Bcr-Abl kinase attracted oncology researchers as a molecular target for CML therapy, and a variety of small Abl kinase inhibitors were synthesized. STI571 (imatinib mesylate) was produced by modification of 2-phenylaminopyrimidine, a core structure of protein kinase C inhibitor, to improve selectivity, stability, solubility, and bioavailability. STI571 competitively binds to the ATP binding site of Bcr-Abl kinase and inhibits Abl tyrosine kinase activity. STI571 showed significant efficacy in the clinical study with CML patients at all stages: chronic phase, accelerated phase, and blast crisis. More than 90% of the patients showed good hematologic response to STI571. STI571 is also a potent inhibitor of a receptor-type c-Kit tyrosine kinase. Therefore, STI571 was examined for therapeutic efficacy against malignant Gastro-Intestinal Stromal Tumors (GIST), which are mainly caused by aberrant expression of a mutated c-Kit that is constitutively active without binding of a ligand, stem cell factor (SCF). More than a half of the metastatic GIST patients enrolled in the clinical study responded to STI571. Thus, STI571 is now used as a therapeutic drug for both CML and GIST in more than 80 countries worldwide. Certain point mutations in the ATP binding site were found to be a cause of resistance to STI571 in both Bcr-Abl and c-Kit kinases. Therefore, it would be better to make a precise therapeutic strategy with STI571 based on the gene analysis data. It is also expected that it will be possible to design an inhibitor to overcome such resistance by using the structural information on the mutants.

Targeting PDGF receptors in cancer--rationales and proof of concept clinical trials

The platelet-derived growth factors (PDGF) are a pleotrophic family of peptide growth factors that signal through cell surface, tyrosine kinase receptors (PDGFR) and stimulate various cellular functions including growth, proliferation, and differentiation. To date, PDGF expression has been demonstrated in a number of different solid tumors, from glioblastomas to prostate carcinomas. In these various tumor types, the biologic role of PDGF signaling can vary from autocrine stimulation of cancer cell growth to subtler paracrine interactions involving adjacent stroma and vasculature. The tyrosine kinase inhibitor imatinib mesylate (formerly STI571, Gleevec, Novartis Pharmaceuticals Corp, East Hanover, NJ) blocks activity of the Bcr-Abl oncoprotein and the cell surface tyrosine kinase receptor c-Kit, and as such was recently approved for several indications in the treatment on chronic myeloid leukemia and gastrointestinal stromal tumors. In both of these examples the target protein was identified by an oncogenic, activating mutation. Imatinib mesylate is also a potent inhibitor of PDGFR kinase and is currently being evaluated for the treatment of chronic myelomonocytic leukemia and glioblastoma multiforme, based upon evidence in these diseases of activating mutations in PDGFR. However, the PDGF pathway may represent a therapeutic target in other solid tumors in which it is not part of the oncogenic transformation. In order to investigate the potential biologic implications of inhibiting PDGFR in these tumor types, clinical trials that investigate both established clinical endpoints of response and benefit, as well as surrogate endpoints that describe the biologic significance of PDGF inhibition in vivo are needed.

Malignant gastrointestinal stromal tumor originating in the lesser omentum, complicated by rapidly progressive glomerulonephritis and gastric carcinoma

A 69-year-old man was admitted with a large elastic mass in the upper abdomen. Computed tomography revealed a massive tumor in contact with the liver and gastrointestinal endoscopy revealed a gastric adenocarcinoma. He developed acute renal failure with massive proteinuria and died with a marked enlargement of the tumor. Autopsy revealed a tumor located in the lesser omentum. The tumor was considered to be a Gastrointestinal Stromal Tumor (GIST) because it was positive for c-kit. In addition, crescent formations and immune complexes in glomeruli were observed. We report the first case of GIST complicated by rapidly progressive glomerulonephritis and gastric carcinoma.

Molecular therapeutics: promise and challenges

The ability to analyze the genetic and epigenetic aberrations present in a particular patient's tumor on a global basis is rapidly maturing. The emerging fields of functional genomics and functional proteomics offer the opportunity to translate these advances into a full comprehension of the pathophysiology of cancer. Linking these approaches to chemical genomics and molecular therapeutics should provide an expanding repertoire of targeted therapeutics for clinical evaluation. Novel clinical trial designs that can determine the efficacy of targeted therapeutics in patients selected for aberrations in the target are needed to evaluate the wealth of new drugs becoming available. The promise of these technologies and advances in our understanding of cancer is immense, making it our responsibility to see them to fruition. These technologies should lead to a new era of individualized molecular medicine, wherein we will treat each patient with a "prescription" based on the genetic changes in each patient's tumor and their own genetic make-up, resulting in more effective and less toxic therapy.

Gastrointestinal stromal tumors respond to tyrosine kinase-targeted therapy

Gastrointestinal stromal tumors (GISTs) are rare tumors of the wall of the stomach and small bowel, and also occasionally arise in the mesentery, omentum, or retroperitoneum. The incidence of GIST in the United States is approximately 500 to 750 patients per 100,000 people. GISTs often present late in their clinical course unless they are the cause of gastrointestinal bleeding or perforation. Surgical resection is the standard of care for primary GIST. However, there is a high risk of recurrence in the peritoneum and liver. For metastatic GIST, imatinib mesylate is the standard of care. Two phase III studies presented in 2003 in abstract form show slightly different results. In the US study, 400 mg/d was found to be equivalent to 800 mg/d with respect to response, progression-free survival, and overall survival at 12 months. In the European/Australasian study, the response rate was the same with either dosage, but progression-free survival was better with 800 mg/d compared with 400 mg/d. Overall survival data for the latter study were too immature for analysis as of May 2003. Adjuvant or neoadjuvant therapy with imatinib is the topic of at least three studies through the American College of Surgeons Oncology Group and Radiation Therapy Oncology Group and the American College of Radiology Imaging Network. Every effort to enroll eligible patients on these studies should be made. New treatments for metastatic disease under investigation include a tyrosine kinase inhibitor with an expanded panel of targets compared with imatinib (SU011248), and the addition of a mammalian target of rapamycin (mTOR) inhibitor and the rapamycin derivative RAD001 to imatinib. Given the finding of a specific molecular defect to exploit, GISTs have gone from an orphan disease to a proving ground for tyrosine kinase-targeted therapy.

Targeted treatment of hypereosinophilic syndromes and chronic eosinophilic leukemias with imatinib mesylate

Idiopathic hypereosinophilic syndrome (HES) and chronic eosinophilia leukemia (CEL) represent the most recent additions to the list of molecularly defined chronic myeloproliferative disorders. Beginning with the observation that imatinib mesylate (Gleevec) could elicit rapid and complete hematologic remissions in a proportion of patients with HES, a reverse bedside-to-bench translational research effort led to the discovery of FIP1L1-PDGFRA, a novel fusion gene on chromosome 4q12 whose product is an imatinib-sensitive protein tyrosine kinase. FIP1L1-PDGFRA is the first description of a gain-of-function fusion gene derived from an interstitial chromosomal deletion rather than a reciprocal translocation. Empiric use of imatinib in HES and CEL provides a dramatic example of how the development of targeted therapeutics can provide tremendous insight into the molecular etiology of what appear to be a diverse and otherwise indecipherable collection of diseases. In this review, we discuss the role of imatinib in HES/CEL and other malignancies characterized by constitutively activated tyrosine kinases, and examine molecular features of the FIP1L1-PDGFRA fusion.

The significance of myelosuppression during therapy with imatinib mesylate in patients with chronic myelogenous leukemia in chronic phase

BACKGROUND

Imatinib mesylate induces high rates of hematologic and cytogenetic response in patients with chronic myelogenous leukemia (CML). During therapy with imatinib, up to 45% of patients with CML reportedly experience myelosuppression > or = Grade 3, requiring interruption of therapy and/or dose reductions. The significance of myelosuppression for response to imatinib is unknown.

METHODS

The authors analyzed 143 patients with late chronic-phase CML who were treated with imatinib after failing interferon. Univariate and multivariate analyses were performed to determine patient characteristics that were correlated with myelosuppression response and the association between myelosuppression and cytogenetic response.

RESULTS

Neutropenia > or = Grade 3 (according to National Cancer Institute Common Toxicity Criteria) occurred in 64 patients (45%), and thrombocytopenia > or = Grade 3 occurred in 31 patients (22%). Any myelosuppression > or = Grade 3 was associated with a lower rate of major (P = 0.04) or complete (P = 0.01) cytogenetic responses. This was more pronounced with myelosuppression that lasted > 2 weeks. The major cytogenetic response rate was 58% with Grade > or = 3 myelosuppression compared with a rate of 75% without Grade > or =3 myelosuppression (P = 0.03); the complete cytogenetic response rates were 36% and 63%, respectively (P = 0.001). In a multivariate analysis, pretreatment platelet count, imatinib dose reductions, and duration of myelosuppression were associated significantly with response.

CONCLUSIONS

Myelosuppression is an independent adverse factor for achieving cytogenetic response with imatinib in patients with CML. Intervention with hematopoietic growth factors in patients with CML who are treated with imatinib should be investigated.

Gastrointestinal stromal tumours and their response to treatment with the tyrosine kinase inhibitor imatinib

Gastrointestinal stromal tumours (GISTs), the most common mesenchymal tumours of the digestive tract, are largely resistant to chemo- and radiotherapy. They are currently defined by their overexpression of the KIT receptor tyrosine kinase (CD117), a member of the family of receptor tyrosine kinases (RTKs), and exhibit KIT mutations in more than 85% of cases. Additionally, in more than one-third of KIT wild-type GISTs, mutations of platelet-derived growth factor receptor alpha (PDGF-R alpha), which also belongs to the family of RTKs, were recently found. Since these data indicate that uncontrolled RTK signalling may be implicated in the pathogenesis of GISTs, RTKs and the activated downstream signalling cascades are attractive targets in the therapy of these tumours. Imatinib is a small-molecule inhibitor that selectively blocks the activity of the PDGF-R, ABL and KIT receptor tyrosine kinases by competitive binding to the adenosine triphosphate binding site of their catalytic domains. We herein review the molecular pathological, preclinical and clinical data that identify imatinib as a valuable new agent in the treatment of GISTs.