New transcriptional-based insights into the pathogenesis of desmoplastic small round cell tumors (DSRCTs)

To gain new insights into desmoplastic small round cell tumors (DSRCTs) by means of gene expression profiling (GEP). Formalin-fixed, paraffin-embedded surgical specimens obtained from seven pretreated DSRCT patients were interrogated using GEP complemented by immunohistochemistry, a cancer stem cell array, and miRNA in situ hybridisation, including the combined chimera modules miRNA-200/ZEB1 and miRNA-34/SLUG. The chimera modules divided the cases into three classes that respectively recapitulated the traits of mesenchymal epithelial reverse transition (MErT), epithelial mesenchymal transition (EMT), and hybrid/partial EMT. This indicates a close correlation between the reprogramming governed by EMT regulators and DSRCT biology, which was further confirmed by miRNA-21 and is consistent with the broad morphological spectrum of DSRCTs. Starting from the miRNA-200/ZEB1 axis, we also found that DSRCTs carry a signature of immunological ignorance that is not responsive to PD-L1 blockade. Evidence that the up-regulation of miRNA-200 and E-cadherin, and quite a high level of miRNA-21 expression segregate with the MErT supports the idea that, in addition to the hybrid/partial state, MErT is also enriched in stemness: the androgen-positive cases, whose stemness traits were confirmed by stem cell arrays, all fell into these two classes. Our findings also confirmed that tumoral cell PDGFRA expression correlates with desmoplasia, and demonstrated the co-expression of PDGFRA and ISLR/Meflin, another marker of pluripotency. Despite the limited number of cases, these findings provide unexpectedly relevant information concerning the pathogenesis of DSRCTs, and prove the validity of miRNA-based chimera circuit modelling in the clinico-pathological setting.

Epithelioid peritoneal mesothelioma: a hybrid phenotype within a mesenchymal-epithelial/epithelial-mesenchymal transition framework

The aim of this study was to reconsider the biological characteristics of epithelioid malignant peritoneal mesothelioma (E-MpM) in the light of new concepts about epithelial mesenchymal transition and mesenchymal epithelial reverse transition (EMT/MErT) and the role of epigenetic reprogramming in this context. To this end we profiled surgical specimens and derived cells cultures by a number of complementary approaches i.e. immunohistochemistry, immunofluorescence, in situ hybridization, biochemistry, pluripotent stem cell arrays, treatments with cytokines, growth factors and specific inhibitors.The analyses of the surgical specimens showed that i) EZH2 is expressed throughout the spectrum of MpM, ii) that E-MpM (including the high-grade undifferentiated form) are characterised by c-MYC and miRNA 17-5p expression, and iii) that progression to sarcomatoid MpM is dictated by EMT regulators. They also showed that E-MpM expressed c-MET and are enriched in E- and P-cadherins- and VEGFR2-expressing CSCs, thus strongly supporting a role for MErT reprogramming in endowing E-MpM tumour cells with stemness and plasticity, and hence with a drug resistant phenotype. The cell culture-based experiments confirmed the stemness traits and plasticity of E-MpM, and support the view that EZH2 is a druggable target in this tumor.

Sunitinib-induced morpho-functional changes and drug effectiveness in malignant solitary fibrous tumours

Sunitinib improves the outcomes of patients with solitary fibrous tumours (SFTs). The aim of this study was to investigate and contextualise sunitinib-induced morpho-functional changes in order to gain insights into the drug's mechanism of action.To this end, four surgical specimens obtained from two sunitinib-responsive patients with malignant SFT, and one primary cell culture obtained from fresh tumoral tissue and its stabilised cell line, were studied by means of immunohistochemistry, bright field in situ hybridisation, immunofluorescence/confocal microscopy, and biochemistry.The post-sunitinib surgical samples were characterised by two biologically relevant morpho-functional changes: clear areas and necrotic foci. The first were associated with the attenuation/loss of PDGFRB expression and decreased mTOR signalling, and corresponded to a pathological response. The second were associated with the over-expression of PDGFRB and VEGFA, strong mTOR signalling activation, and the appearance of HIF1α expression, hallmarks of pathological progression. The analysis clearly showed that sunitinib reduces the vascular supply network and inhibits tumoral cells. It also either induces autophagy, thus favouring drug response, or impairs autophagy as a result of lysosome sequestration, thus favouring disease progression. These distinct autophagic events were associated with different myeloid immune contextures. Finally, we also found that PDGFRB is one of the components of a complex that includes Beclin 1 and VPS34.The results of these tissue-based analyses provide new insights into sunitinib's mechanism of action in SFT patients.

Identification of SRF-E2F1 fusion transcript in EWSR-negative myoepithelioma of the soft tissue

Myoepithelial neoplasms (MN) are rare and not well-circumstanced entities displaying a heterogeneous spectrum of genetic abnormalities, including EWSR1, FUS and PLAG1 rearrangements. However, in the remaining MN no other fusion gene has been described and knowledge concerning secondary acquired molecular alterations is still poor. Therefore, we screened 5 cases of MN of the soft tissue by RNA sequencing with the aim of identifying novel fusion transcripts.

A novel SRF-E2F1 fusion was detected in two cases: one was negative for other fusions while the other showed also the presence of FUS-KLF17. The fusion was validated through independent techniques and, in both cases, SRF-E2F1 was detected only in a subclone of the tumoral mass. SRF-E2F1 maintained the coding frame, thus leading to the translation of a chimeric protein containing the DNA-binding domain of SRF and the trans-activation domain of E2F1. Moreover, ectopical expression of SRF-E2F1 demonstrated that the chimeric transcript is functionally active and could affect tumor growth.

Occurrence in two cases and biological relevance of the two genes involved suggest that the SRF-E2F1 fusion might become a helpful diagnostic tool. Further biologic studies are needed to better assess its role in MN biology.

Sirolimus in Advanced Epithelioid Hemangioendothelioma: A Retrospective Case-Series Analysis from the Italian Rare Cancer Network Database

BACKGROUND

The aim of this study was to report on sirolimus activity in a series of patients with hemangioendothelioma (HE) treated at the National Cancer Institute, Milan (Istituto Nazionale Tumori; INT) and within the Italian Rare Cancer Network ("Rete Tumori Rari"; RTR).

METHODS

We retrospectively reviewed patients with advanced and progressing epithelioid hemangioendothelioma (EHE) treated with sirolimus at the INT and/or within the RTR. Pathologic review and molecular analysis for WWTR1 rearrangement were performed. Sirolimus was administered until unacceptable toxicity or progression, with the dose being adjusted to reach target plasma levels of 15-20 ng/dL. Responses were assessed using the Response Evaluation Criteria In Solid Tumors (RECIST) criteria.

RESULTS

Since 2005, 18 patients (17 EHE, 1 retiform HE; 1 locally advanced, 17 metastatic; WWTR1 rearrangement: 16) have been identified, with 17/18 patients being evaluable for response. Mean sirolimus daily dose was 4.5 mg. According to RECIST, best responses in EHE were 1 partial response (PR), 12 stable disease (SD), and 3 progressive disease (PD); the patient with retiform HE also achieved a PR, lasting >2 years. Four patients with a reversed interval progression on interruption were observed. Median overall survival was 16 months, and median progression-free survival was 12 months (range 1-45), with four patients progression-free at 24 months. The clinical benefit (complete response [CR] + PR + SD >6 months) was 56 %. Seven patients receiving sirolimus experienced an increase in pleural/peritoneal effusion plus worsening of tumor-related symptoms; six of these patients died within 1-8 months from evidence of effusion progression, while a RECIST PD was assessed in two of seven patients.

CONCLUSIONS

A clinical benefit was achieved in 56 % of patients receiving sirolimus, which lasted >24 months in four patients. Most patients with pleural effusion did not benefit from sirolimus and had a poor outcome.

Evolution of Dermatofibrosarcoma Protuberans to DFSP-Derived Fibrosarcoma: An Event Marked by Epithelial-Mesenchymal Transition-like Process and 22q Loss

Dermatofibrosarcoma protuberans (DFSP) is a rare and indolent cutaneous sarcoma. At times, a fibrosarcomatous transformation marked by a more aggressive clinical behavior may be present. We investigated the natural history and the molecular bases of progression from classic DFSP to the fibrosarcomatous form (FS-DFSP), looking, retrospectively, at the outcome of all patients affected by primary DFSP treated at our institution from 1993 to 2012 and analyzing the molecular profile of 5 DFSPs and 5 FS-DFSPs by an integrated genomics approach (whole transcriptome sequencing, copy number analysis, FISH, qRT-PCR, IHC). The presence of fibrosarcomatous features was identified in 20 (7.6%) patients out of 263 DFSP. All cases were treated with macroscopic complete surgery. A local relapse occurred in 4 of 23 patients who received a microscopic marginal surgery (2 classic DFSP, 2 FS-DFSP), while metastasis affected 2 patients, both FS-DFSP (10% of FS-DFSP), being the first event. DFSP evolution to FS-DFSP was paralleled by a transcriptional reprogramming. The recurrent loss of chromosome 22q appeared to contribute to this phenomenon by promoting the expression of epigenetic regulators, such as EZH2. Loss of the p16/CDKN2A/INK4A locus at 9p was also observed in two FS-DFSP metastatic cases.

IMPLICATIONS

FS-DFSP is a rare subgroup among DFSP, with a 10% metastatic risk, that was independent from local recurrence and that was not observed in DFSP, that were all cured by wide surgery. Chromosome 22q deletion might play a role in FS-DFSP, and p16 loss may convey a poor outcome. EZH2 dysregulation was also found and represents a druggable target. Mol Cancer Res; 14(9); 820-9. ©2016 AACR.

Identification of a gene expression driven progression pathway in myxoid liposarcoma

Aim: to investigate the events involved in the progression of myxoid liposarcoma (MLS).

Gene expression profiling and immunohistochemical/biochemical analyses were applied to specimens representative of the opposite ends of the MLS spectrum: pure myxoid (ML) and pure round cell (RC) liposarcomas.

The analyses revealed the involvement of both coding and non coding RNAs (SNORDs located in DLK1-DIO3 region) and support a model of stepwise progression mainly driven by epigenetic changes involving tumour vascular supply and tumoral cellular component. In this model, a switch in the vascular landscape from a normal to a pro-angiogenic signature and the silencing of DLK1-DIO3 region mark the progression from ML to RC in concert with the acquisition by the latter of the over-expression of YY1/C-MYC/HDAC2, together with over-expression of genes involved in cell proliferation and stemness: MKNK2, MSX1 and TRIM71.

Taken together, these findings strongly suggest that to progress from ML to RC liposarcoma the cells have to overcome the epigenetic silencing restriction point in order to reset their new stem-like differentiation signature. Our findings provide a first attempt at identifying the missing links between ML and RC liposarcomas, that may also have broader applications in other clinico-pathological settings characterised by a spectrum of progression.

Efficacy and Biological Activity of Imatinib in Metastatic Dermatofibrosarcoma Protuberans (DFSP)

PURPOSE

To report on imatinib mesylate (IM) in patients with metastatic dermatofibrosarcoma protuberans (DFSP)/fibrosarcomatous (FS)-DFSP and on the impact of the treatment on tumor biology.

EXPERIMENTAL DESIGN

Ten consecutive patients treated with IM from 2007 to 2015 for a metastatic relapse from DFSP/FS-DFSP were identified. FISH analysis for COL1A1-PDGFB was performed. Two IM-treated and 4 naïve FS-DFSP were transcriptionally profiled by RNAseq on HiScanSQ platform. Differential gene expression was analyzed with edgeR (Bioconductor), followed by hierarchical clustering and Principal Component Analysis.

RESULTS

All cases featured fibrosarcomatous in the metastasis and retained the COL1A1-PDGFB. Best RECIST response was: 8 partial response, 1 stable disease, and 1 progressive disease. Median progression-free survival was 11 months. Five patients received surgery after IM and all relapsed. IM was restored in 4 patients with a new response. After IM, the most upregulated genes included those encoding for immunoglobulins and those affecting functions and differentiation of endothelial cells. Pathway enrichment analysis revealed upregulation in genes involved in antigen processing and presentation, natural killer-mediated cytotoxicity, and drug and xenobiotics metabolism. Conversely, a significant down-regulation of kinase signaling pathways was detected.

CONCLUSIONS

All metastatic cases were fibrosarcomatous. Most patients responded to IM, but PFS was shorter than reported in published series which included both DFSP and FS-DFSP. All patients operated after IM had a relapse, suggesting that IM cannot eradicate metastatic cases and that the role of surgery is limited. Transcriptional profile of naïve and posttreatment samples pointed the contribution of immune infiltrates in sustaining the response to IM.

Solitary fibrous tumors: loss of chimeric protein expression and genomic instability mark dedifferentiation

Solitary fibrous tumors, which are characterized by their broad morphological spectrum and unpredictable behavior, are rare mesenchymal neoplasias that are currently divided into three main variants that have the NAB2-STAT6 gene fusion as their unifying molecular lesion: usual, malignant and dedifferentiated solitary fibrous tumors. The aims of this study were to validate molecular and immunohistochemical/biochemical approaches to diagnose the range of solitary fibrous tumors by focusing on the dedifferentiated variant, and to reveal the genetic events associated with dedifferentiation by integrating the findings of array comparative genomic hybridization. We studied 29 usual, malignant and dedifferentiated solitary fibrous tumors from 24 patients (including paired samples from five patients whose tumors progressed to the dedifferentiated form) by means of STAT6 immunohistochemistry and (when frozen material was available) reverse-transcriptase polymerase chain reaction and biochemistry. In addition, the array comparative genomic hybridization findings were used to profile 12 tumors from nine patients. The NAB2/STAT6 fusion was detected in all of the tumors, but immunohistochemistry and western blotting indicated that chimeric protein expression was atypical or absent in 9 out of 11 dedifferentiated tumors. The comparative genomic hybridization results revealed that the usual and malignant solitary fibrous tumors had a simple profile, whereas the genome of the dedifferentiated tumors was complex and unstable, and suggested that 13q and 17p deletions and TP53 mutations may be present in malignant lesions before the full expression of a dedifferentiated phenotype. Solitary fibrous tumor dedifferentiation is associated with the loss of chimeric oncoprotein expression, genomic instability, and cell decommitment and reprogramming. The assessment of dedifferentiated solitary fibrous tumors is based on the presence of the fusion transcripts and, in principle, negative STAT6 immunohistochemistry should not rule out a diagnosis of solitary fibrous tumor.

Melan-A/MART-1 immunity in a EWS-ATF1 translocated clear cell sarcoma patient treated with sunitinib: a case report

Background

Clear cell sarcoma (CCS), initially named malignant melanoma of soft parts, is an aggressive soft tissue sarcoma (STS) that, due to MITF activation, shares with melanoma the expression of melanocyte differentiation antigens. CCS is poorly sensitive to chemotherapy. Multi-kinase inhibitors have been used as therapeutic agents. In the case we report here, treatment with sunitinib induced a long-lasting clinical response that was associated with an immune activation directed against Melan-A/MART-1 antigen.

Case presentation

A 28 years old female patient with an advanced molecularly confirmed CCS resistant to conventional chemotherapy was started in January 2012 on sunitinib, 37.5 mg/day, with evidence of radiologic and metabolic response at the primary and metastatic sites of disease. Pathologic response and loss of the Melan-A/MART-1 antigen were evidenced on residual tumor removed in April 2012. Immunological monitoring performed on patient’s blood during pharmacological treatment revealed a systemic, Melan-A/MART-1 specific immunity and a low frequency of immunosuppressive cells. Sunitinib was restarted in May 2012, with a new response, and continued for 11 months although with repeatedly interruptions due to toxicity. Disease progression and new responses were documented at each treatment interruption and restart. Sunitinib was definitively interrupted in April 2013 for disease progression.

Conclusion

The analysis of this case proves that antigens expressed by CCS, as for melanoma, can be immunogenic in vivo and that tumor-antigen specific T cells may exert anti-tumor activity in CCS patient. Thus, manipulation of the immune response may have therapeutic potential for this STS subtype and immunotherapy approaches, can be promising therapeutic options for these patients.

Preclinical and clinical evidence of activity of pazopanib in solitary fibrous tumour

BACKGROUND

To explore the activity of pazopanib in solitary fibrous tumour (SFT).

PATIENTS AND METHODS

In a preclinical study, we compared the activity of pazopanib, sorafenib, sunitinib, regorafenib, axitinib and bevacizumab in a dedifferentiated-SFT (DSFT) xenotransplanted into Severe Combined Immunodeficiency (SCID) mice. Antiangiogenics were administered at their reported optimal doses when mean tumour volume (TV) was 80 mm(3). Drug activity was assessed as TV inhibition percentage (TVI%). From May 2012, six consecutive patients with advanced SFT received pazopanib, on a national name-based programme. In one case sunitinib was administered after pazopanib failure.

RESULTS

In the xenograft model, pazopanib showed the lowest antitumour activity (21%TVI), while regorafenib was the most active (95%TVI). Sorafenib, bevacizumab, sunitinib were markedly active (78/70/65%TVI). Axitinib was marginally active (51%TVI). In the retrospective case-series, three patients carried malignant-SFT (MSFT), three DSFT. Best Response Evaluation Criteria in Solid Tumour (RECIST) responses were: three stable disease (SD), all MSFT, three progressive disease (PD), all DSFT, corresponding to one partial response (PR), two SD, three PD by Choi criteria. Median-progression-free survival was 3 months (range 1-15). In one patient, sunitinib was started after pazopanib failure, with a response.

CONCLUSIONS

In dedifferentiated-SFT xenograft pazopanib induced a marginal antitumour activity, while regorafenib appeared the most active and promising agent. When administered in patients, pazopanib showed a modest activity in terms of tumour growth stabilisation, observed only in non-dedifferentiated cases.

Activity of sunitinib in extraskeletal myxoid chondrosarcoma

BACKGROUND

Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft tissue sarcoma, marked by NR4A3 rearrangement. Herein we report on the activity of sunitinib in a series of 10 patients, strengthening what initially observed in two cases.

PATIENTS AND METHODS

From July 2011, 10 patients with progressive metastatic translocated EMC have been consecutively treated with sunitinib 37.5mg/day, on a named-use basis. In an attempt to interpret the activity of sunitinib in EMC, genotype/phenotype correlations were carried out by fluorescence in situ hybridization (FISH) analyses. Moreover, transcriptome, immunohistochemical and biochemical analyses of a limited set of samples were performed focusing on some putative targets of sunitinib.

RESULTS

Eight of 10 patients are still on therapy. Six patients had a Response Evaluation Criteria in Solid Tumours (RECIST) partial response (PR), two were stable, two progressed. Positron emission tomography (PET) was consistent in 6/6 evaluable cases. One patient underwent surgery after sunitinib, with evidence of a pathologic response. At a median follow-up of 8.5 months (range 2-28), no secondary resistance was detected. Median progression free survival (PFS) has not been reached. Interestingly, all responsive cases turned out to express the typical EWSR1-NR4A3 fusion, while refractory cases carried the alternative TAF15-NR4A3 fusion. Among putative sunitinib targets, only RET was expressed and activated in analysed samples.

CONCLUSIONS

This report confirms the therapeutic activity of sunitinib in EMC. Genotype/phenotype analyses support a correlation between response and EWSR1-NR4A3 fusion. Involvement of RET deserves further investigation.

Anthracycline-based chemotherapy in extraskeletal myxoid chondrosarcoma: a retrospective study

BACKGROUND

Extraskeletal myxoid chondrosarcoma (EMC) is a rare subgroup within soft tissue sarcomas. Its sensitivity to chemotherapy is reported to be low.

METHODS

We retrospectively reviewed a series of 11 EMC patients treated as from 2001 within the Italian Rare Cancer Network (RCN) with anthracycline-based chemotherapy. Pathologic diagnosis was centrally reviewed in all cases and confirmed by the presence of the specific chromosomal rearrangements, involving the NR4A3 gene locus on chromosome 9.

RESULTS

Eleven patients treated with anthracycline-based chemotherapy were included (M/F: 9/2 - mean age: 52 years - site of primary: lower limb/other = 9/2 - metastatic = 11 - front line/ further line = 10/1 - anthracycline as single agent/ combined with ifosfamide = 1/10). Ten patients are evaluable for response. Overall, best response according to RECIST was: partial response (PR) = 4 (40 %), stable disease (SD) = 3, progressive disease (PD) = 3 cases. Median PFS was 8 (range 2-10) months.

CONCLUSIONS

By contrast to what reported so far, anthracycline-based chemotherapy is active in a distinct proportion of EMC patients.

Structured myeloid cells and anti-angiogenic therapy in alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma and the clinical management of patients with unresectable, metastatic disease is still challenging. ASPS expresses an array of potentially therapeutically targetable, angiogenesis-related molecules and, importantly, it has a distinctive angiogenic phenotype marked by a peculiar tumor-associated vasculature. Several studies, conducted in transgenic mouse models and in a large variety of human tumors of different histotype, clearly proved the substantial contribution of tumor-infiltrating myeloid cells, such as myeloid derived suppressor cells, monocytes and macrophages, in the formation and maintenance of abnormal blood vessels in tumors. By immunohistochemistry we thus explored the presence and the distribution of cells expressing myeloid markers in the inflammatory infiltrate of surgical treated metastatic ASPS. Indeed, we found that myeloid cells expressing CD14 and CD163 markers constitute the prominent cells in the inflammatory infiltrate of ASPS. These macrophage-like cells form a network surrounding the endothelial cells, or, interspersed in the tumor nest, they keep deep contact with tumor cells. In this commentary, we discussed our findings in relation to the recently published paper by Kummar and colleagues reporting the clinical and molecular results of a phase II clinical trial in patients with unresectable, metastatic ASPS treated with the anti-angiogenic drug cediranib, targeting the VEGFR-1,-2,-3 tyrosine kinases.

Phase II study on lapatinib in advanced EGFR-positive chordoma

BACKGROUND

To report on a prospective, investigator-driven, phase II study on lapatinib in epidermal growth factor receptor (EGFR)-positive advanced chordoma patients.

PATIENTS AND METHODS

From December 2009 to January 2012, 18 advanced progressing chordoma patients entered this study (median age: 61 years; disease extent: metastatic 72% and locally advanced 28%). Epidermal growth factor receptor (EGFR) expression and activation were evaluated by immunohistochemistry and/or phospho-arrays, real-time polimerase chain reaction, fluorescence immunostaining. Fluorescence in situ hybridization analysis was also carried out. Patients received lapatinib 1500 mg/day (mean dose intensity = 1282 mg/day), until progression or toxicity. The primary study end point was response rate (RR) as per Choi criteria. Secondary end points were RR by Response Evaluation Criteria in Solid Tumor (RECIST), overall survival, progression-free survival (PFS) and clinical benefit rate (CBR; RECIST complete response + partial response (PR) + stable disease (SD) ≥ 6 months).

RESULTS

All patients were evaluable for response. Six (33.3%) patients had PR and 7 (38.9%) SD, as their best Choi responses, corresponding to RECIST SD in all cases. Median PFS by Choi was 6 [interquartile (IQ) range 3-8] months. Median PFS by RECIST was 8 (IQ range 4-12) months, with a 22% CBR.

CONCLUSIONS

This phase II study showed a modest antitumor activity of lapatinib in chordoma. The clinical exploitation of EGFR targeting in chordoma needs to be further investigated, both clinically and preclinically. Clinical trial Registration No: EU Clinical Trials Register trial no. 2009-014456-29.

Sunitinib malate in solitary fibrous tumor (SFT)

BACKGROUND

To report on sunitinib activity in a retrospective series of 35 solitary fibrous tumor (SFT) treated at a single institution.

PATIENTS AND METHODS

From April 2008, 35 patients with progressive advanced SFT (male/female: 20/15; mean age: 58 years; meningeal/extrameningeal: 6/29; locally advanced/metastatic: 15/20; prior chemotherapy: 25) were treated, on an individual use basis, with continuous-dosing sunitinib 37.5 mg/day. Platelet-derived growth factor receptor beta (PDGFRB) and vascular endothelial growth factor receptor 2 (VEGFR2) status were assessed by immunohistochemistry and, in a subgroup of patients, by real time PCR.

RESULTS

Thirty-one patients were assessable for response by RECIST (one early death; three early interruptions). Best responses were 2 partial response (PR), 16 stable disease, 13 progressive disease. A <30% decrease in size was observed in three patients. Fourteen of 29 patients assessable by Choi criteria had a PR. Median progression-free survival by RECIST was 6 months (range 1-22). In two of six patients, resistance to sunitinib was overcome by increasing sunitinib to 50 mg/day. PDGFRB and/or VEGFR2 were positive in all cases and not predictive of response; a less aggressive morphology corresponded to an increased response rate (53% PR by Choi in the malignant SFT, 20% PR in the pleomorphic/dedifferentiated SFT).

CONCLUSIONS

Sunitinib is active in SFT. Response can be long-lasting.

Extraskeletal myxoid chondrosarcoma: tumor response to sunitinib

Background

Extraskeletal myxoid chondrosarcoma (EMCS) is a rare soft tissue sarcoma of uncertain differentiation, characterized in most cases by a translocation that results in the fusion protein EWSR1-CHN (the latter even called NR4A3 or TEC). EMCS is marked by >40% incidence of metastases in spite of its indolent behaviour. It is generally resistant to conventional chemotherapy, and, to the best of our knowledge, no data have been reported to date about the activity of tirosin-kinase inhibitor (TKI) in this tumor. We report on two consecutive patients carrying an advanced EMCS treated with sunitinib.

Methods

Since July 2011, 2 patients with progressive pretreated metastatic EMCS (Patient1: woman, 58 years, PS1; Patient2: man, 63 years, PS1) have been treated with continuous SM 37.5 mg/day, on an individual use basis. Both patients are evaluable for response. In both cases diagnosis was confirmed by the presence of the typical EWSR1-CHN translocation.

Results

Both patients are still on treatment (11 and 8 months). Patient 1 got a RECIST response after 4 months from starting sunitinib, together with a complete response by PET. An interval progression was observed after stopping sunitinib for toxicity (abscess around previous femoral fixation), but response was restored after restarting sunitinib. Patient 2 had an initial tumor disease stabilization detected by CT scan at 3 months. Sunitinib was increased to 50 mg/day, with evidence of a dimensional response 3 months later.

Conclusions

Sunitinib showed antitumor activity in 2 patients with advanced EMCS. Further studies are needed to confirm these preliminary results.

Gastrointestinal stromal tumor of the rectum: results of surgical and multimodality therapy in the era of imatinib

BACKGROUND

The rectum is a rare site of gastrointestinal stromal tumor (GIST), and factors determining long-term outcome remain unclear. In a population study, we assessed the outcome of rectal GIST patients treated at two referral centers.

METHODS

A total of 39 patients diagnosed with rectal GIST between January 2002 and December 2010 were identified in prospective databases. Tumor and patient characteristics, treatment details, and outcome were evaluated. Median follow-up was 41 (3-110) months.

RESULTS

A male predominance was noticed (M/F = 29/10). Median age was 53 years (range, 32-80 years). The cohort included, of 39 patients, 12 low-risk, 26 high-risk, and 1 with M1 disease. Of 38 patients with nonmetastatic disease, 36 underwent surgery as transabdominal (15 of 36) or local (21 of 36) resection. There were 21 patients who received preoperative and/or postoperative imatinib treatment. Patients with preoperative imatinib (16 of 36) had a significantly higher rate of R0 resections (p = .02). Five patients developed local recurrences. All of them had undergone local tumor excision with positive margins and without perioperative imatinib. Also, five patients suffered from distant metastases. All belonged to the high-risk group and underwent tumor surgery (3 R0, 2 R1) without receiving perioperative imatinib. A total of three patients died of disease. Perioperative imatinib was associated with improved local disease-free, disease-free, and overall survival (p < .01, p < .01, and p = .03, respectively). Local disease-free survival was significantly improved by negative resection margins (p < .01).

CONCLUSIONS

Complete resection is recommended to achieve local disease control. Preoperative imatinib was associated with improved surgical margins. Perioperative imatinib was associated with improved local disease-free, disease-free, and overall survival.

Lapatinib in advanced chordoma: A phase II study

10026

Background: To report on a prospective Phase II, investigator-driven, collaborative study to explore the activity of lapatinib, a dual EGFR and ErbB2 inhibitor, in EGFR-positive advanced chordomas. Methods: From December 2009 to December 2011, 19 advanced progressing chordoma patients entered this study (mean age: 59 yrs – range = 35-75; PS: 0-3 - ≥2 = 52%; site: sacrum = 68%, spine = 21%, skull base = 11%; disease extent: metastatic = 68%, locally advanced = 32%). EGFR expression was evaluated by immunohistochemistry in all patients. EGFR activation was detected in 15 of 17 evaluable cases by phospho-arrays and/or real-time PCR and/or fluorescence immunostaining. EGFR FISH analysis showed high level of gene gain in 4. HerB2 status is under evaluation. Patients received lapatinib 1500 mg/day (dose intensity in excess of 1250 mg/day), until progression or toxicity. The primary study end-point was response rate (RR) as for Choi criteria extended to MRI. Secondary end-points were RR by RECIST, PFS by Choi, OS, clinical benefit rate (CBR) (CR+PR+SD≥6mos), correlation between EGFR status and response. Results: 16 pts are evaluable for response (3 too early); 4 patients are still on treatment. 3 patients (19%) had a partial response (PR) and 8 (50%) a stable disease (SD) as their best Choi response, corresponding to RECIST SD in all cases. The 3 cases with a PR by Choi had a minor decrease in size; another patient had a mixed response. The CBR was 19%. Median PFS as for Choi was 5.5 (range = 2-12+) months, with 1 patient being progression-free at 18 months. Toxicity was as expected. In one case treatment was interrupted due to side effects. No correlation was observed between EGFR expression/activation and response. Conclusions: This Phase II study showed a modest activity of lapatinib in chordoma. EGFR expression was not predictive of response. The clinical relevance of EGFR targeting in chordoma needs to be further investigated.

DHM simulation in virtual environments: a case-study on control room design

This paper will present the workflow developed for the application of serious games in the design of complex cooperative work settings. The project was based on ergonomic studies and development of a control room among participative design process. Our main concerns were the 3D human virtual representation acquired from 3D scanning, human interaction, workspace layout and equipment designed considering ergonomics standards. Using Unity3D platform to design the virtual environment, the virtual human model can be controlled by users on dynamic scenario in order to evaluate the new work settings and simulate work activities. The results obtained showed that this virtual technology can drastically change the design process by improving the level of interaction between final users and, managers and human factors team.

High CD133 expression levels in gastrointestinal stromal tumors

BACKGROUND

Gastrointestinal stromal tumours (GISTs) have activating KIT or PDGFRA gene mutations. Imatinib mesylate, which targets KIT and PDGFRA, is effective in treating GISTs, but 90% of GIST patients become imatinib-resistant as a result of acquiring secondary KIT mutations. Recent findings suggest that tumour growth can be driven by mutated self-renewing progenitors known as cancer stem cells (CSCs), which are believed to be present in all neoplastic proliferations and are thought to accumulate mutations. It is therefore possible that the acquisition of secondary KIT mutations during imatinib treatment may occur in putative GIST CSCs.

METHODS

Using flow cytometry, in vivo murine xenografts and molecular characterization, we tried to identify putative GIST CSCs by looking for the occurrence of common CSC markers such as KIT, CD133, CD90, CD44, and CD34 in 18 surgical samples obtained from nine untreated and nine imatinib-treated KIT-mutated GIST patients.

RESULTS

The results indicated the homogeneous and previously unreported expression of CD133 (18/18), CD90 (15/16), and CD44 (12/14), together with KIT (18/18) and CD34 (13/18). This profile is similar to that identified in bone marrow mesenchymal progenitors and does not seem to be significantly modified by imatinib as only marginal changes in KIT and CD133 expression (P ≤ 0.05, Mann-Whitney test) were found in the treated samples.

CONCLUSIONS

These findings suggest that GISTs are a clonal expansion of quite primitive cells that strictly depend on KIT oncogenic addiction, and have no cancer/stem cell component that can be detected by means of the antigens used in this study.

Role of EGFR family receptors in proliferation of squamous carcinoma cells induced by wound healing fluids of head and neck cancer patients

BACKGROUND

Mounting evidence suggests that recurrence of resected head and neck squamous cell carcinomas (HNSCCs) is due to the outgrowth of unrecognized residual tumor cells as well as to the premalignant and/or precursor-field epithelial cells. We studied the impact of processes triggered by HNSCC surgery in stimulating both residual tumor cells [demonstrated to overexpress epidermal growth factor receptor (EGFR)], and premalignant cells surrounding the resected lesion.

PATIENTS AND METHODS

EGFR expression/activation by immunohistochemistry/biochemistry and gene status by FISH were investigated in 23 primary HNSCCs and surrounding tissues. The ability to induce cell proliferation of wound healing drainages collected from 12 relapsed and 11 not relapsed patients was evaluated by a colorimetric assay in squamous cell carcinoma cell lines A431 (carrying EGFR amplification) and CAL27 (carrying three EGFR copies) in the presence/absence of EGFR therapeutic inhibitors.

RESULTS

Primary tumors showed intermediate/high EGFR expression (91%), EGFR phosphorylation and EGFR-positive FISH (35%). Normal, metaplastic and dysplastic epithelium surrounding the resected tumor displayed EGFR overexpression. EGFR activation and gene amplification were observed in normal and dysplastic epithelium, respectively. Each tested wound healing drainage induced the cells to proliferate and the proliferation was significantly higher in relapsed compared with not relapsed HNSCC patients (P = 0.02 and P = 0.03). Anti-EGFR treatments inhibited the drainage-induced proliferation, with the highest inhibitory efficiency by cetuximab on A431 cells, while CAL27 cell growth was more efficiently inhibited by tyrosine kinase inhibitors.

CONCLUSIONS

Surgery could favor the proliferation of cells showing EGFR overexpression/activation/amplification such as residual tumor cells and/or precursor-field epithelial cells already present after surgery. Treatment with anti-EGFR reagents inhibits wound-induced stimulation, according to the EGFR family status.

Imatinib response in two GIST patients carrying two hitherto functionally uncharacterized PDGFRA mutations: an imaging, biochemical and molecular modeling study

Beside the well known "in vivo" and "in vitro" Imatinib resistant D842V mutation in PDGFRA receptor, very few are the information concerning the "in vivo" Imatinib activity with respect to the other PDGFRA mutations for which only "in vitro" data are available. Two patients carrying PDGFRA mutations in exons 18 (involving residues DIMH842-845) and 12 (V561D), respectively, were treated with Imatinib at a dose of 400 mg/day. According to Response Evaluation Criteria in Solid Tumors criteria, after a median treatment of 7 months both patients showed clinical partial response, and underwent surgery of the minimal residual disease. Tumor response was confirmed pathologically. In both patients, analyses of PDGFRA performed on pre- and/or post-treatment material were compared to affinity data of the mutated receptor towards the inhibitor. Molecular modeling evidence was found to be consistent with sensitivity of mutated PDGFRA receptors to Imatinib. Thus, the "in vivo" evidence that these two mutations of PDGFRA are sensitive to Imatinib was confirmed by a multidimensional approach comprising "in silico" experiments that, in association to molecular and biochemical analyses, constitutes a powerful tool to predict Imatinib sensitivity, clinically beneficial in the treatment of these tumors with molecularly targeted therapies.

Sunitinib in advanced alveolar soft part sarcoma: evidence of a direct antitumor effect

BACKGROUND

The purpose of this study was to confirm sunitinib activity in alveolar soft part sarcoma (ASPS) and to report on new insights into the molecular bases thereof.

PATIENTS AND METHODS

From July 2007, nine patients with progressive metastatic ASPS received sunitinib 37.5 mg/day, within a named use program. Cryopreserved material was available for five naive patients, among whom three received sunitinib. Immunofluorescence (IF)/confocal microscopy, biochemical, and molecular/cytogenetic analyses were carried out, complemented by antiproliferative and activation assays in a short-term culture derived from one case.

RESULTS

All patients were eligible for response. Best RECIST response was partial response in five cases, stable disease in three, and progression in one. The median progression-free survival was 17 months. Positron emission tomography results were consistent. Two cases of interval progressions were recorded. Antiproliferative assays and biochemistry on short-term culture showed that sunitinib is able to markedly impair ASPS cells growth and switch-off PDGFRB. IF/confocal microscopy demonstrated coexpression and physical association between PDGFRB/vascular endothelial growth factor receptor 2 (VEGFR2) and RET/VEGFR2 in ASPS cells, which was validated by biochemistry. PDGFRB, RET, and MET ligand-dependent activation was confirmed.

CONCLUSIONS

We confirm the clinical efficacy of sunitinib in ASPS, mediated by PDGFRB, VEGFR2, and RET, which are all expressed in tumor cells. A direct antitumor effect was shown in a short-term cell culture.

Sunitinib malate and figitumumab in solitary fibrous tumor: patterns and molecular bases of tumor response

Antiangiogenic treatment activity has been reported in solitary fibrous tumor (SFT), a rare and little chemosensitive sarcoma. We explored the activity of sunitinib malate (SM) in SFT and studied receptor tyrosine kinase (RTK) activation profile. Eleven patients with progressive metastatic SFT resistant to chemotherapy were treated with continuous-dosing 37.5 mg/d SM on a named-use basis. One of them also received the insulin-like growth factor I receptor (IGFIR) inhibitor figitumumab after developing secondary resistance to SM. Besides, biochemical, molecular, and fluorescence in situ hybridization analyses were done in eight naïve SFTs whose cryopreserved material was available to clarify RTK upstream and downstream signaling. In two cases treated with SM and belonging to the naïve series, both pretreatment and posttreatment samples were available. Ten patients were evaluable for response to SM. The best response according to the Choi criteria was six partial response (all with Response Evaluation Criteria in Solid Tumors stable disease), one stable disease, and three progressive disease. Responses lasted >6 months in five patients. The eight naïve samples showed high expression/phosphorylation of PDGFRB, epidermal growth factor receptor, and IGFIR/IR, in the presence of their cognate ligands. Downstream pathways revealed expression/activation of Akt, extracellular signal-regulated kinase 1-2 and, closely related to SFT subtypes, of S6 and 4E-BP1. In two patients, whose pretreatment and posttreatment clinical and molecular status were available, biochemical data confirmed the activity of SM, although they also suggested a possible time-dependent shift of dominant RTK from PDGFRB to IGFIR/insulin receptor. A Response Evaluation Criteria in Solid Tumors partial response to figitumumab corroborated these findings. SM has antitumor activity in SFT, possibly through a PDGFRB-mediated mechanism, but treatments with IGFIR/insulin receptor and possibly epidermal growth factor receptor inhibitors are worth testing.

Functional mapping of receptor tyrosine kinases in myxoid liposarcoma

PURPOSE

The aim of this study was to analyze receptor tyrosine kinases (RTK) and their downstream signaling activation profile in myxoid liposarcomas (MLS) by investigating 14 molecularly profiled tumors: 7 naive and 7 treated with conventional chemotherapy/radiotherapy or the new drug trabectedin.

EXPERIMENTAL DESIGN

Frozen and matched formalin-fixed, paraffin-embedded material from surgical specimens were analyzed using biochemical, molecular, and molecular/cytogenetic approaches, complemented by immunohistochemistry and confocal microscopy.

RESULTS

In the absence of any RTK and downstream effector deregulation, the naive cases revealed epidermal growth factor receptor, platelet-derived growth factor receptor B, RET, and MET activation sustained by autocrine/paracrine loops, and RTK cross-talk as a result of heterodimerization. Interestingly, RET and MET activation seems to play a major role in the pathogenesis of MLS by involving different targets through different mechanisms. RET activation (which may activate MET) involves the tumoral vascular component by means of RET/MET cross-talk and VEGFA (vascular endothelial growth factor A)/GFRalpha3 (glial cell-derived neurotrophic factor family receptor alpha3)/artemin-mediated signaling as revealed by VEGF receptor 2/RET coimmunoprecipitation. MET activation involves the cellular tumor component by means of a direct ligand-dependent loop and indirect GFRalpha3 (RET coreceptor)/artemin-mediated signaling. About downstream signaling, the association of AKT activation with the round cell variant is interesting. No relevant changes in the original RTK activation profiles were observed in the posttreatment cases, a finding that is in keeping with the nontargeted treatments used.

CONCLUSIONS

These findings highlight the particular cell-specific activation profile of RET/GFRalpha3 and MET in MLS, and the close correlation between AKT activation and the round cell variant, thus opening up new therapeutic perspectives for MET/AKT inhibitors and antagonistic small molecules binding GFRalpha3.

Analysis of receptor tyrosine kinases (RTKs) and downstream pathways in chordomas

We have previously demonstrated that chordomas express activated platelet-derived growth factor receptor (PDGFRB) and that treatment with imatinib, which is capable of switching off the activation of various receptor tyrosine kinases (RTKs) including PDGFRB, benefits a number of patients. The aim of this study was to identify the possible presence of other activated RTKs and their downstream signaling effectors. Cryopreserved material from 22 naïve sporadic chordomas was investigated for the presence of activated RTKs and their cognate ligands and downstream signaling effectors by means of human phospho-RTK antibody arrays, Western blotting, and molecular analysis; immunohistochemistry and fluorescence in situ hybridization were used to analyze the corresponding formalin-fixed and paraffin-embedded samples. We detected activated PDGFRB, FLT3, and colony stimulating factor 1 receptor (CSF1R) of the PDGFR family and highly phosphorylated EGFR, HER2/neu, and (to a lesser extent) HER4 of the EGFR family. The detection of PDGFRB/PDGFB confirmed our previous data. The presence of activated EGFR was paralleled by the finding of high levels of epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha) and PDGFB co-expression and PDGFRB co-immunoprecipitation. Of the downstream effectors, the PI3K/AKT and RAS/MAPK pathways were both activated, thus leading to the phosphorylation of mammalian target of rapamycin (mTOR) and 4E-BP1 among the regulators involved in translational control. Taken together, our results (i) provide a rationale for tailored treatments targeting upstream activated receptors, including the PDGFR and EGFR families; (ii) support the idea that a combination of upstream antagonists and mTOR inhibitors enhances the control of tumor growth; and (iii) indicate that the 4E-BP1/eIF4E pathway is a major regulator of protein synthesis in chordoma.

Evaluation of the antitumor activity of sunitinib malate (SM) in solitary fibrous tumor (SFT)

10571

Background: SFT is a rare soft tissue tumor, with an unpredictable metastatic potential. When medical therapy is needed, cytotoxic chemotherapy is poorly active in this sarcoma subtype, but the activity of bevacizumab + temozolomide was recently reported. We explored the activity of SM in SFT, given the vascular pattern of this tumor and our preliminary observations about RTK activation (with upregulation of the PDGFR family, VEGFR and EGFR). Methods: From April 2008, 5 patients with progressive metastatic SFT resistant to conventional chemotherapy (male/female: 3/2 - mean-age: 58 years - PS: 0–3 - site: peritoneum 3, pleura 1, bladder 1) have been treated with continuous-dosing SM 37.5 mg/day, on an individual use basis. All patients were evaluated for response at least once, while 2 more patients are now starting therapy. RTK biochemical analysis was performed in 3 patients of this series, in addition to a group of other patients with malignant SFT whose cryopreserved material was available. Results: Between 3 weeks and 3 months, 4 in 5 patients had a tumor response according to Choi's criteria (all with RECIST stable disease) . The other patient stopped therapy for progression after 3 weeks and died 2 weeks later. Baseline PET was negative in 4 out of 5 patients. One responsive patient stopped therapy after 3 weeks for side effects and depression. The remaining 3 responsive patients are currently on treatment, although one had a focal progression after 9 months. In two, surgery of residual disease is planned, and downstream RTK signaling analysis will be performed on the specimen. Conclusions: SM has antitumor activity in SFT. This might help address an unmet clinical need in a rare sarcoma subtype. Biomolecular assessments are ongoing.

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Oncogenic and ligand-dependent activation of KIT/PDGFRA in surgical samples of imatinib-treated gastrointestinal stromal tumours (GISTs)

As the range of receptor tyrosine kinase (RTK) inhibitors widens, a detailed understanding of the activating mechanisms of KIT/platelet-derived growth factor receptor (PDGFR)A and the related downstream pathways involved in the development and maintenance of GISTs is becoming increasingly important. We analysed areas with different histological response ratios in surgical specimens taken from imatinib-treated and untreated GIST patients in order to investigate KIT and PDGFRA expression/activation, the presence of their cognate ligands and the activation of downstream signalling, by means of biochemistry, immunohistochemistry and flow cytometry. All of the cases showed KIT and PDGFRA co-expression. In addition to the oncogenic activation of mutated receptors, activation of wild-type KIT and wild-type PDGFRA, sustained by heterodimerization and an autocrine-paracrine loop, was demonstrated by the presence of their specific ligands, stem cell factor (SCF) and PDGFA. To confirm RTK activation further, all of the samples (including those with the highest regression ratios) were investigated for downstream effectors, and all proved to have activated downstream signalling. The results show that after the mutated receptors are switched off, heterologous wild-type receptors become important in imatinib-treated GISTs as a means of maintaining signalling activation. Taken together, our findings suggest that drugs targeting wild-type receptors should be tested in imatinib-treated GIST patients.

Cyclooxygenase-2 and platelet-derived growth factor receptors as potential targets in treating aggressive fibromatosis

PURPOSE

To explore the molecular bases of potential new pharmacologic targets in aggressive fibromatosis (desmoid tumor).

EXPERIMENTAL DESIGN

Tumor specimens from 14 patients surgically treated for aggressive fibromatosis (6 familial adenomatous polyposis and 8 sporadic cases), analyzed for adenomatous polyposis coli (APC) and CTNNB1 (beta-catenin) mutations, were further investigated for beta-catenin, cyclooxygenase-2 (COX-2), platelet-derived growth factor (PDGF) receptor alpha (PDGFRA)/PDGF receptor beta (PDGFRB), their cognate ligands (PDGFA and PDGFB), and KIT using a comprehensive immunohistochemical, biochemical, molecular, and cytogenetic approach.

RESULTS

No CTNNB1 (beta-catenin) mutations were found in the familial adenomatous polyposis patients, but previously reported activating mutations were found in six of the eight sporadic patients. All of the cases carrying an altered WNT pathway showed nuclear and cytoplasmic immunoreactivity for beta-catenin, whereas beta-catenin expression was restricted to the cytoplasm in the sporadic patients lacking CTNNB1 mutations. COX-2 protein and mRNA overexpression was detected in all 14 cases, together with the expression and phosphorylation of PDGFRA and PDGFRB, which in turn paralleled the presence of their cognate ligands. No PDGFRB mutations were found. The results are consistent with PDGFRA and PDGFRB activation sustained by an autocrine/paracrine loop.

CONCLUSIONS

Aggressive fibromatosis is characterized by WNT/oncogene pathway alterations triggering COX-2-mediated constitutive coactivation of PDGFRA and PDGFRB, and may therefore benefit from combined nonsteroidal anti-inflammatory drug + tyrosine kinase inhibitor treatment.

Evidence for activation of KIT, PDGFRalpha, and PDGFRbeta receptors in the Ewing sarcoma family of tumors

BACKGROUND

The Ewing sarcoma family of tumors (ESFT) is one of the most common malignant neoplasms of children and adolescents, characterized by nonrandom translocations involving the Ewing sarcoma (EWS) gene. Over the years the adoption of intensive multimodality treatment approaches has led to a gradual improvement in the survival of patients with ESFT. The prognosis is still unsatisfactory for high-risk patients, however, and novel therapeutic approaches are desirable. The aim of the study was to investigate the expression/activation of KIT, PDGFRalpha, and PDGFRbeta receptor tyrosine kinases (RTKs) as potential therapeutic targets in ESFT.

METHODS

RNA and proteins were extracted from 20 frozen ESFT specimens to ascertain the state activation of KIT, PDGFRalpha, and PDGFRbeta.

RESULTS

No mutations were found, whereas the cognate ligands were detected in all cases by polymerase chain reaction (PCR). The expression and activation of KIT, PDGFRalpha, and PDGFRbeta were confirmed by quantitative PCR, immunohistochemistry, and immunoprecipitation and/or Western blot analysis. In particular, when compared with a protein pool obtained from normal adult tissues, PDGFRbeta showed a greater protein expression and/or a stronger phosphorylation signal.

CONCLUSIONS

The results are consistent with an autocrine/paracrine loop activation of the KIT, PDGFRalpha, and PDGFRbeta receptors and suggest a rationale for the use of RTK inhibitors, either alone or in combination with chemotherapy.

Analysis of potential receptor tyrosine kinase targets in intimal and mural sarcomas

Primary sarcomas of the great vessels are very rare neoplasms and only a few cases have been reported. They are divided into the two broad categories of intimal or luminal and mural sarcomas. We analysed eight advanced high-grade sarcomas originating from major vessels (seven intimal and one mural sarcoma) by means of immunohistochemistry and FISH analysis for PDGFRA, PDGFRB, EGFR and KIT receptor tyrosine kinases (RTKs), together with immunoprecipitation/western blotting, sequencing of the corresponding genes, and the search for cognate ligands. The intimal sarcomas showed a wide spectrum of morphologies and immunophenotypes, whereas the mural sarcoma had common leiomyosarcomatous features. Regardless of their category, all of the cases had a PDGFRA-deregulated cytogenetic profile mainly consisting of an amplification cluster; five were also polysomic for PDGFRB, whereas three showed disomy. Six cases had a deregulated EGFR gene, and c-Kit gene status was similar to that of PDGFRA. In one case, biochemical analysis revealed the presence of activated and highly expressed PDGFRA, PDGFRB and EGFR, whereas KIT was expressed at reference level. Sequencing of the corresponding genes revealed no activating mutations in any of the analysed receptors. The cognate ligands were detected in all cases. In predictive terms, the evidence of gene amplification/high polysomy of several RTKs, together with PDGFRA, PDGFRB and EGFR expression and phosphorylation, suggests that these tumours may be sensitive to RTK-inhibiting treatments.