Treatment of gastrointestinal stromal tumor after imatinib and sunitinib.

Purpose of review Tyrosine kinase inhibitors (TKIs), such as imatinib and sunitinib, have changed the outcome of patients with gastrointestinal stromal tumor (GIST) and prolonged survival by many-fold. Unfortunately, treatment failure and tumor progression seem inevitable over time and constitute an unresolved clinical challenge. This article reviews current efforts to overcome drug resistance and progression. Recent findings The major mechanism of resistance toward imatinib and sunitinib is the development of secondary resistance mutations in the kinase domain of KIT. Recent efforts aim at inhibitors with increased activity against resistance mutations or a broader spectrum of activity. Other strategies include indirect KIT inhibition by modulating KIT chaperone proteins or inhibition of KIT-dependent and independent signaling pathways. Summary dThe rapid improvement of our understanding of GIST biology as well as resistance mechanisms towards imatinib and sunitinib will greatly facilitate the development of novel treatment strategies. This article summarizes the results of recently reported third and fourth-line clinical trials in patients with resistant GIST and reviews data of important proof-of-concept studies.

Retrovirus-host interactions. The mouse mammary tumor virus model.

Mouse mammary tumor virus (MMTV) is a retrovirus which can induce mammary carcinomas in mice late in life by activation of proto-oncogenes after integration in their vicinity. Surprisingly, it requires a functional immune system to achieve efficient infection of the mammary gland. This requirement became clear when it was discovered that it has developed strategies to exploit the immune response. Instead of escaping immune detection, it induces a vigorous polyclonal T-B interaction which is required to induce a chronic infection. This is achieved by activating and then infecting antigen presenting cells (B cells), expressing a superantigen on their cell surface and triggering unlimited help by the large number of superantigen-specific T cells. The end result of this strong T-B interaction is the proliferation and differentiation of the infected B cells leading to their long term survival.

Involvement of microglia-neuron interactions in the tumor necrosis factor-alpha release, microglial activation, and neurodegeneration induced by trimethyltin.

Trimethyltin (TMT) is a neurotoxicant known to induce early microglial activation. The present study was undertaken to investigate the role played by these microglial cells in the TMT-induced neurotoxicity. The effects of TMT were investigated in monolayer cultures of isolated microglia or in neuron-enriched cultures and in neuron-microglia and astrocyte-microglia cocultures. The end points used were morphological criteria; evaluation of cell death and cell proliferation; and measurements of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and nitric oxide (NO) release in culture supernatant. The results showed that, in cultures of microglia, TMT (10(-6) M) caused, after a 5-day treatment, an increased release of TNF-alpha, without affecting microglial shape or cell viability. When microglia were cocultured with astrocytes, TNF-alpha release was decreased to undetectable levels. In contrast, in neuron-microglia cocultures, TNF-alpha levels were found to increase at lower concentrations of TMT (i.e., 10(-8) M). Moreover, at 10(-6) M of TMT, microglia displayed further morphological activation, as suggested by process retraction and by decrease in cell size. No morphological activation was observed in cultures of isolated microglial cells and in astrocyte-microglia cocultures. With regard to neurons, 10(-6) M of TMT induced about 30% of cell death, when applied to neuron-enriched cultures, whereas close to 100% of neuronal death was observed in neuron-microglia cocultures. In conclusion, whereas astrocytes may rather dampen the microglial activation by decreasing microglial TNF-alpha production, neuronal-microglial interactions lead to enhanced microglial activation. This microglial activation, in turn, exacerbates the neurotoxic effects of TMT. TNF-alpha may play a major role in such cell-cell communications.

Complete longitudinal analyses of the randomized, placebo-controlled, phase III trial of sunitinib in patients with gastrointestinal stromal tumor following imatinib failure.

PURPOSE: To analyze final long-term survival and clinical outcomes from the randomized phase III study of sunitinib in gastrointestinal stromal tumor patients after imatinib failure; to assess correlative angiogenesis biomarkers with patient outcomes. EXPERIMENTAL DESIGN: Blinded sunitinib or placebo was given daily on a 4-week-on/2-week-off treatment schedule. Placebo-assigned patients could cross over to sunitinib at disease progression/study unblinding. Overall survival (OS) was analyzed using conventional statistical methods and the rank-preserving structural failure time (RPSFT) method to explore cross-over impact. Circulating levels of angiogenesis biomarkers were analyzed. RESULTS: In total, 243 patients were randomized to receive sunitinib and 118 to placebo, 103 of whom crossed over to open-label sunitinib. Conventional statistical analysis showed that OS converged in the sunitinib and placebo arms (median 72.7 vs. 64.9 weeks; HR, 0.876; P = 0.306) as expected, given the cross-over design. RPSFT analysis estimated median OS for placebo of 39.0 weeks (HR, 0.505, 95% CI, 0.262-1.134; P = 0.306). No new safety concerns emerged with extended sunitinib treatment. No consistent associations were found between the pharmacodynamics of angiogenesis-related plasma proteins during sunitinib treatment and clinical outcome. CONCLUSIONS: The cross-over design provided evidence of sunitinib clinical benefit based on prolonged time to tumor progression during the double-blind phase of this trial. As expected, following cross-over, there was no statistical difference in OS. RPSFT analysis modeled the absence of cross-over, estimating a substantial sunitinib OS benefit relative to placebo. Long-term sunitinib treatment was tolerated without new adverse events.

Diffusion-weighted magnetic resonance imaging in metastatic gastrointestinal stromal tumor (GIST): a pilot study on the assessment of treatment response in comparison with 18F-FDG PET/CT.

BACKGROUND: Diffusion-weighted magnetic resonance imaging (MRI) is increasingly being used for assessing the treatment succes in oncology, but the real clinical value needs to evaluated by comparison with other, already established, metabolic imaging techniques. PURPOSE: To prospectively evaluate the clinical potential of diffusion-weighted MRI with apparent diffusion coefficient (ADC) mapping for gastrointestinal stromal tumor (GIST) response to targeted therapy compared with 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). MATERIAL AND METHODS: Eight patients (mean age, 56 ± 11 years) known to have metastatic GIST underwent 18F-FDG PET/CT and MRI (T1Gd, DWI [b = 50,300,600], ADC mapping) simultaneously, before and after change in targeted therapy. MR and PET/CT examinations were first analyzed blindly. Second, PET/CT images were co-registered with T1Gd-MR images for lesion detection. Only 18F-FDG avid lesions were considered. Maximum standardized uptake value (SUVmax) and the corresponding minimum ADCmin were measured for the six largest lesions per patient, if any, on baseline and follow-up examinations. The relationship between changes in SUVmax and ADCmin was analyzed (Spearman's correlation). RESULTS: Twenty-four metastases (12 hepatic, 12 extra-hepatic) were compared on PET/CT and MR images. SUVmax decreased from 7.7 ± 8.1 g/mL to 5.5 ± 5.4 g/mL (P = 0.20), while ADCmin increased from 1.2 ± 0.3 × 10(-3)mm(2)/s to 1.5 ± 0.3 × 10(-3)mm(2)/s (P = 0.0002). There was a significant association between changes in SUVmax and ADCmin (rho = - 0.62, P = 0.0014), but not between changes in lesions size (P = 0.40). CONCLUSION: Changes in ADCmin correlated with the response of 18F-FDG avid GIST to targeted therapy. Thus, diffusion-weighted MRI may represent a radiation-free alternative for follow-up treatment for metastatic GIST patients.

Dissecting TCR-MHC/peptide complex interactions with A2/peptide multimers incorporating tumor antigen peptide variants: crucial role of interaction kinetics on functional outcomes.

Soluble peptide/MHC-class-I (pMHC) multimers have recently emerged as unique reagents for the study of specific interactions between the pMHC complex and the TCR. Here, we assessed the relative binding efficiency of a panel of multimers incorporating single-alanine-substituted variants of the tumor-antigen-derived peptide MAGE-A10(254-262) to specific CTL clones displaying different functional avidity. For each individual clone, the efficiency of binding of multimers incorporating MAGE-A10 peptide variants was, in most cases, in good although not linear correlation with the avidity of recognition of the corresponding variant. In addition, we observed two types of discrepancies between efficiency of recognition and multimer binding. First, for some peptide variants, efficient multimer binding was detected in the absence of measurable effector functions. Some of these peptide variants displayed antagonist activity. Second, when comparing different clones we found clear discrepancies between the dose of peptide required to obtain half-maximal lysis in CTL assays and the binding efficiency of the corresponding multimers. These discrepancies, however, were resolved when the differential stability of the TCR/pMHC complexes was determined. For individual clones, decreased recognition correlated with increased TCR/pMHC off-rate. TCR/pMHC complexes formed by antagonist ligands displayed off-rates faster than those of TCR/pMHC complexes formed with weak agonists. In addition, when comparing different clones, the efficiency of multimer staining correlated better with relative multimer off-rates than with half-maximal lysis values. Altogether, the data presented here reconcile and extend our previous results on the impact of the kinetics of interaction of TCR with pMHC complexes on multimer binding and underline the crucial role of TCR/pMHC off-rates for the functional outcome of such interactions.

Concepts of metastasis in flux: the stromal progression model.

The ability of tumor cells to leave a primary tumor, to disseminate through the body, and to ultimately seed new secondary tumors is universally agreed to be the basis for metastasis formation. An accurate description of the cellular and molecular mechanisms that underlie this multistep process would greatly facilitate the rational development of therapies that effectively allow metastatic disease to be controlled and treated. A number of disparate and sometimes conflicting hypotheses and models have been suggested to explain various aspects of the process, and no single concept explains the mechanism of metastasis in its entirety or encompasses all observations and experimental findings. The exciting progress made in metastasis research in recent years has refined existing ideas, as well as giving rise to new ones. In this review we survey some of the main theories that currently exist in the field, and show that significant convergence is emerging, allowing a synthesis of several models to give a more comprehensive overview of the process of metastasis. As a result we postulate a stromal progression model of metastasis. In this model, progressive modification of the tumor microenvironment is equally as important as genetic and epigenetic changes in tumor cells during primary tumor progression. Mutual regulatory interactions between stroma and tumor cells modify the stemness of the cells that drive tumor growth, in a manner that involves epithelial-mesenchymal and mesenchymal-epithelial-like transitions. Similar interactions need to be recapitulated at secondary sites for metastases to grow. Early disseminating tumor cells can progress at the secondary site in parallel to the primary tumor, both in terms of genetic changes, as well as progressive development of a metastatic stroma. Although this model brings together many ideas in the field, there remain nevertheless a number of major open questions, underscoring the need for further research to fully understand metastasis, and thereby identify new and effective ways of treating metastatic disease.

The tumor microenvironment and its contribution to tumor evolution toward metastasis.

Cancer cells acquire cell-autonomous capacities to undergo limitless proliferation and survival through the activation of oncogenes and inactivation of tumor suppressor genes. Nevertheless, the formation of a clinically relevant tumor requires support from the surrounding normal stroma, also referred to as the tumor microenvironment. Carcinoma-associated fibroblasts, leukocytes, bone marrow-derived cells, blood and lymphatic vascular endothelial cells present within the tumor microenvironment contribute to tumor progression. Recent evidence indicates that the microenvironment provides essential cues to the maintenance of cancer stem cells/cancer initiating cells and to promote the seeding of cancer cells at metastatic sites. Furthermore, inflammatory cells and immunomodulatory mediators present in the tumor microenvironment polarize host immune response toward specific phenotypes impacting tumor progression. A growing number of studies demonstrate a positive correlation between angiogenesis, carcinoma-associated fibroblasts, and inflammatory infiltrating cells and poor outcome, thereby emphasizing the clinical relevance of the tumor microenvironment to aggressive tumor progression. Thus, the dynamic and reciprocal interactions between tumor cells and cells of the tumor microenvironment orchestrate events critical to tumor evolution toward metastasis, and many cellular and molecular elements of the microenvironment are emerging as attractive targets for therapeutic strategies.

Interactions between Siglec-7/9 receptors and ligands influence NK cell-dependent tumor immunosurveillance.

Alteration of the surface glycosylation pattern on malignant cells potentially affects tumor immunity by directly influencing interactions with glycan-binding proteins (lectins) on the surface of immunomodulatory cells. The sialic acid-binding Ig-like lectins Siglec-7 and -9 are MHC class I-independent inhibitory receptors on human NK cells that recognize sialic acid-containing carbohydrates. Here, we found that the presence of Siglec-9 defined a subset of cytotoxic NK cells with a mature phenotype and enhanced chemotactic potential. Interestingly, this Siglec-9+ NK cell population was reduced in the peripheral blood of cancer patients. Broad analysis of primary tumor samples revealed that ligands of Siglec-7 and -9 were expressed on human cancer cells of different histological types. Expression of Siglec-7 and -9 ligands was associated with susceptibility of NK cell-sensitive tumor cells and, unexpectedly, of presumably NK cell-resistant tumor cells to NK cell-mediated cytotoxicity. Together, these observations have direct implications for NK cell-based therapies and highlight the requirement to consider both MHC class I haplotype and tumor-specific glycosylation.

Early prediction of response to sunitinib after imatinib failure by 18F-fluorodeoxyglucose positron emission tomography in patients with gastrointestinal stromal tumor.

PURPOSE: Positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) was used to evaluate treatment response in patients with gastrointestinal stromal tumors (GIST) after administration of sunitinib, a multitargeted tyrosine kinase inhibitor, after imatinib failure. PATIENTS AND METHODS: Tumor metabolism was assessed with FDG-PET before and after the first 4 weeks of sunitinib therapy in 23 patients who received one to 12 cycles of sunitinib therapy (4 weeks of 50 mg/d, 2 weeks off). Treatment response was expressed as the percent change in maximal standardized uptake values (SUV). The primary end point of time to tumor progression was compared with early PET results on the basis of traditional Response Evaluation Criteria in Solid Tumors (RECIST) criteria. RESULTS: Progression-free survival (PFS) was correlated with early FDG-PET metabolic response (P < .0001). Using -25% and +25% thresholds for SUV variations from baseline, early FDG-PET response was stratified in metabolic partial response, metabolically stable disease, or metabolically progressive disease; median PFS rates were 29, 16, and 4 weeks, respectively. Similarly, when a single FDG-PET positive/negative was considered after 4 weeks of sunitinib, the median PFS was 29 weeks for SUVs less than 8 g/mL versus 4 weeks for SUVs of 8 g/mL or greater (P < .0001). None of the patients with metabolically progressive disease subsequently responded according to RECIST criteria. Multivariate analysis showed shorter PFS in patients who had higher residual SUVs (P < .0001), primary resistance to imatinib (P = .024), or nongastric GIST (P = .002), regardless of the mutational status of the KIT and PDGFRA genes. CONCLUSION: Week 4 FDG-PET is useful for early assessment of treatment response and for the prediction of clinical outcome. Thus, it offers opportunities to individualize and optimize patient therapy.

Comparative study of the different degrees of risk of gastrointestinal stromal tumor

OBJECTIVE: To evaluate the applicability of the main categories of risk and morphological factors in the prognosis of gastrointestinal stromal tumors. METHODS: we retrospectively studied fifty-four cases of GIST, assessing the main prognostic factors of this neoplasis: risk levels, topography, size, mitotic index, necrosis, histological subtype and immunophenotype. We also verified their association and the reduction of overall survival. RESULTS: Univariate analysis showed that tumors with mitoses number greater than 5 per 50CGA (high-power fields), the presence of necrosis and a high risk for both the systems proposed by Fletcher and Miettinen had a significant association with reduced survival (p = 0.00001, 0.0056, 0.03 and 0.009, respectively). The remaining analyzed factors (size, histological subtype, topography and immunophenotype) had no such association. Multivariate analysis (Jacard index) showed that the Miettinen degree of risk was the one that best correlated with prognosis. CONCLUSION: the risk criteria of Fletcher and Miettinen are important in assessing the prognosis of patients with gastrointestinal stromal tumors, especially the latter, which adds to the mitotic index and the presence of tumor necrosis.

Treatment of gastrointestinal stromal tumor (GIST) during bariatric surgery

The gastrointestinal stromal tumor (GIST) is a rare mesenchymal tumor. One should pay special attention when the GIST comes in obese patients during surgery. The laparoscopic resections with standard techniques, such as gastric bypass, have been described with good results. However, GIST resection associated sleeve gastrectomy for the treatment of obesity is rare, but can be done safely, depending on the location of the tumor.

Perivascular epithelioid cell tumor of the liver coexisting with a gastrointestinal stromal tumor

Approximately 10% of patients with gastrointestinal stromal tumors (GIST) develop other neoplasms, either synchronously or metachronously. In this report we describe coexistence of a gastrointestinal stromal tumor and a hepatic perivascular epithelioid cell tumor (PEComa) in a 51-year-old woman with no evidence of tuberous sclerosis. A subcapsular hepatic nodule (0.8 cm in diameter) was found during surgery for symptomatic gastric neoplasm (15 cm in diameter) arising from the lesser curvature. Both tumors revealed histomorphological and immunohistochemical features confirming a diagnosis of a small incidental hepatic PEComa and a high risky extramural gastric GIST, respectively. The patient remained disease-free 25 mo after surgery with no evidence of tumor recurrence or new neoplasms. To our knowledge, this is the first report of PEComa in a patient with GIST. Hepatic lesions detected synchronously or metachronously in patients with GISTs may represent histogenetically distinct lesions and should be sampled to confirm or exclude metastatic GISTs. (C) 2008 WJG. All rights reserved.

Genomics and proteomics approaches to the study of cancer-stroma interactions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)