Usefulness of an RNA extraction-free test for the multiplexed detection of ALK, ROS1, and RET Gene Fusions in Real Life FFPE Specimens of Non-Small Cell Lung Cancers.

BACKGROUND: ALK, ROS1 and RET rearrangements occur, respectively, in 5%, 2%, and 1% non-small cell lung cancers (NSCLC). ALK and ROS1 fusion proteins detection by immunohistochemistry (IHC) has been validated for rapid patient screening, but ROS1 fusions need to be confirmed by another technique and no RET IHC test is available for clinical use. RESEARCH DESIGN AND METHODS: We report herein the usefulness of the HTG EdgeSeq Assay, an RNA extraction-free test combining a quantitative nuclease protection assay with NGS, for the detection of ALK, ROS1 and RET fusions from 'real-life' small NSCLC samples. A total of 203 FFPE samples were collected from 11 centers. They included 143 rearranged NSCLC (87 ALK, 39 ROS1, 17 RET) and 60 ALK-ROS1-RET negative controls. RESULTS: The assay had a specificity of 98% and a sensitivity for ALK, ROS1 and RET fusions of 80%, 94% and 100% respectively. Among the 19 HTG-assay false negative samples, the preanalytical conditions were identified as the major factors impacting the assay efficiency. CONCLUSIONS: Overall, the HTG EdgeSeq assay offers comparable sensitivities and specificity than other RNA sequencing techniques, with the advantage that it can be used on very small and old samples collected multicentrically.

Wholistic approach: Transcriptomic analysis and beyond using archival material for molecular diagnosis.

Many neoplasms remain unclassified after histopathological examination, which requires further molecular analysis. To this regard, mesenchymal neoplasms are particularly challenging due to the combination of their rarity and the large number of subtypes, and many entities still lack robust diagnostic hallmarks. RNA transcriptomic profiles have proven to be a reliable basis for the classification of previously unclassified tumors and notably for mesenchymal neoplasms. Using exome-based RNA capture sequencing on more than 5000 samples of archival material (formalin-fixed, paraffin-embedded), the combination of expression profiles analyzes (including several clustering methods), fusion genes, and small nucleotide variations has been developed at the Centre Léon Bérard (CLB) in Lyon for the molecular diagnosis of challenging neoplasms and the discovery of new entities. The molecular basis of the technique, the protocol, and the bioinformatics algorithms used are described herein, as well as its advantages and limitations.

Compound Clear Cell Sarcoma of the Skin-A Potential Diagnostic Pitfall: Report of a Series of 4 New Cases and a Review of the Literature.

The proliferation of cells with melanocytic lineage and a nested pattern has traditionally been regarded as a characteristic feature of a wide range of benign and malignant melanocytic proliferations. Herein, we report a series of 4 clear cell sarcomas, including 3 primary cutaneous and 1 metastatic to the skin, associated with a clear-cut intraepidermal proliferation of tumor cells representing a serious potential diagnostic pitfall. All patients were male individuals, aged from 17 to 71 years (mean: 42 y). The size of the tumors ranged from 8 to 55 mm (mean: 22.2 mm, median: 13 mm). Two tumors arose on a lower extremity and 1 each on the scalp and chest. Cutaneous metastasis developed on the limb proximal to the amputation site. Histologically, all tumors were variably circumscribed nodular or multinodular proliferations within the dermis, focally extending into the subcutis. They were composed of nests and fascicles of pale spindled and epithelioid cells with finely granular or pale cytoplasm, elongated nuclei with a single prominent nucleolus, featuring mild nuclear pleomorphism, and surrounded by delicate fibrous septa. Scattered wreath-like giant cells were present in all cases. Mitotic activity was low (mean and median: 3.5 mitoses/mm). The intraepidermal component consisted in all 4 cases of nests of tumor cells localized at the dermal-epidermal junction. Nests were well-defined and composed of spindled or epithelioid cells with irregular hyperchromatic nuclei, prominent nucleoli, and scant to moderately abundant eosinophilic to pale cytoplasm. Lentiginous proliferation of epithelioid tumor cells was coupled with focal upward migration of isolated tumor cells in a single case. By immunohistochemistry, all tumors were S100 protein, melan A, and HMB45 positive. By fluorescence in situ hybridization analysis, 3 tumors displayed rearrangements in the EWSR1 gene, whereas reverse transcriptase polymerase chain reaction confirmed EWSR1(e8)/ATF1(e4) translocation in the remaining case. In conclusion, an epidermal component in primary cutaneous clear cell sarcomas, or cutaneous metastasis of the tumor, is exceptional and represents a potential diagnostic pitfall. Careful attention to the salient morphologic features in the dermal component of the tumor, as well as confirmation of EWSR1 gene rearrangement by fluorescence in situ hybridization or reverse transcriptase polymerase chain reaction, is necessary for correct recognition of the tumor and to avoid erroneous diagnosis of a benign or malignant melanocytic proliferation.

Filigree-like Rete Ridges, Lobulated Nests, Rosette-like Structures, and Exaggerated Maturation Characterize Spitz Tumors With NTRK1 Fusion.

Activating NTRK1 fusions have been described as oncogenic events across the spectrum of Spitz tumors. Herein we report a series of 38 Spitz tumors with NTRK1 fusion. These Spitz tumors have distinctive histopathologic features characterized by filigree-like rete ridges which are elongated, thin and branched, dermal melanocytes arranged in a rosette-like configuration, and marked diminishment of melanocyte size with descent into the dermis. These features are distinct from those of other genetically defined subtypes of Spitz tumors and can aid in microscopic diagnosis and help prioritize in case selection for molecular testing in the rare patients that need targeted therapy.

Alternative PDGFD rearrangements in dermatofibrosarcomas protuberans without PDGFB fusions.

Dermatofibrosarcoma protuberans is underlined by recurrent collagen type I alpha 1 chain-platelet-derived growth factor B chain (COL1A1-PDGFB) fusions but ~ 4% of typical dermatofibrosarcoma protuberans remain negative for this translocation in routine molecular screening. We investigated a series of 21 cases not associated with the pathognomonic COL1A1-PDGFB fusion on routine fluorescence in situ hybridization (FISH) testing. All cases displayed morphological and clinical features consistent with the diagnosis of dermatofibrosarcoma protuberans. RNA-sequencing analysis was successful in 20 cases. The classical COL1A1-PDGFB fusion was present in 40% of cases (n = 8/20), and subsequently confirmed with a COL1A1 break-apart FISH probe in all but one case (n = 7/8). 55% of cases (n = 11/20) displayed novel PDGFD rearrangements; PDGFD being fused either to the 5' part of COL6A3 (2q37.3) (n = 9/11) or EMILIN2 (18p11) (n = 2/11). All rearrangements led to in-frame fusion transcripts and were confirmed at genomic level by FISH and/or array-comparative genomic hybridization. PDGFD-rearranged dermatofibrosarcoma protuberans presented clinical outcomes similar to typical dermatofibrosarcoma protuberans. Notably, the two EMILIN2-PDGFD cases displayed fibrosarcomatous transformation and homozygous deletions of CDKN2A at genomic level. We report the first recurrent molecular variant of dermatofibrosarcoma protuberans involving PDGFD, which functionally mimic bona fide COL1A1-PDGFB fusions, leading presumably to a similar autocrine loop-stimulating PDGFRB. This study also emphasizes that COL1A1-PDGFB fusions can be cytogenetically cryptic on FISH testing in a subset of cases, thereby representing a diagnostic pitfall that pathologists should be aware of.

Precision diagnostics of Ewing's sarcoma by liquid biopsy: circulating EWS-FLI1 fusion transcripts.

BACKGROUND: Limited information is available on the applicative value of liquid biopsy (LB) in rare tumors, including Ewing's sarcoma (ES). The accepted precision diagnostics standards would greatly benefit from a non-invasive LB test monitoring pathognomonic gene rearrangements in the bloodstream. METHODS: Tissue and blood samples were collected from six and four ES patients, respectively. Plasma was cleared by two successive rounds of centrifugation and stored frozen until RNA extraction by the QIAmp CNA kit. RNA was retro-transcribed and subjected to real-time quantitative polymerase chain reaction (RT-qPCR) and digital polymerase chain reaction (dPCR). Reactions were set up using two custom primer sets identifying types 1 and 2 EWS-FLI1 fusion transcripts. RESULTS: The two prevalent types of EWS-FLI1 rearrangements could be identified using only two sets of polymerase chain reaction primers, regardless of patient-specific EWS-FLI1 DNA breakpoints. RT-qPCR and dPCR discriminated the two variants in five tumor tissue RNAs and in four circulating tumor RNAs (ctRNAs). Of note, EWS-FLI1 molecular diagnosis was possible using blood samples even when tumor tissue was not available. ctRNA levels correlated (p < 0.05) with volume-based positron emission tomography (PET) parameters (metabolic tumor volume and total lesion glycolysis), and allowed the fine tracking of disease course after surgery, during adjuvant as well as neoadjuvant chemotherapy, and at follow up in one patient. CONCLUSIONS: To our knowledge, this is one of the few single-marker LB assays in solid tumors specifically designed to detect rearranged RNAs in blood, and the first study describing EWS circulating tumor RNAs in ES patients. Altogether, our results support the idea that LB may have a considerable impact on ES patient monitoring and management.

A first-in-human study investigating biodistribution, safety and recommended dose of a new radiolabeled MAb targeting FZD10 in metastatic synovial sarcoma patients.

BACKGROUND: Synovial Sarcomas (SS) are rare tumors occurring predominantly in adolescent and young adults with a dismal prognosis in advanced phases. We report a first-in-human phase I of monoclonal antibody (OTSA-101) targeting FZD10, overexpressed in most SS but not present in normal tissues, labelled with radioisotopes and used as a molecular vehicle to specifically deliver radiation to FZD10 expressing SS lesions. METHODS: Patients with progressive advanced SS were included. In the first step of this trial, OTSA-101 in vivo bio-distribution and lesions uptake were evaluated by repeated whole body planar and SPECT-CT scintigraphies from H1 till H144 after IV injection of 187 MBq of 111In-OTSA-101. A 2D dosimetry study also evaluated the liver absorbed dose when using 90Y-OTSA-101. In the second step, those patients with significant tumor uptake were randomized between 370 MBq (Arm A) and 1110 MBq (Arm B) of 90Y-OTSA-101 for radionuclide therapy. RESULTS: From January 2012 to June 2015, 20 pts. (median age 43 years [21-67]) with advanced SS were enrolled. Even though 111In-OTSA-101 liver uptake appeared to be intense, estimated absorbed liver dose was less than 20 Gy for each patient. Tracer intensity was greater than mediastinum in 10 patients consistent with sufficient tumor uptake to proceed to treatment with 90Y-OTSA-101: 8 were randomized (Arm A: 3 patients and Arm B: 5 patients) and 2 were not randomized due to worsening PS. The most common Grade ≥ 3 AEs were reversible hematological disorders, which were more frequent in Arm B. No objective response was observed. Best response was stable disease in 3/8 patients lasting up to 21 weeks for 1 patient. CONCLUSIONS: Radioimmunotherapy targeting FZD10 is feasible in SS patients as all patients presented at least one lesion with 111In-OTSA-101 uptake. Tumor uptake was heterogeneous but sufficient to select 50% of pts. for 90Y-OTSA-101 treatment. The recommended activity for further clinical investigations is 1110 MBq of 90Y-OTSA-101. However, because of hematological toxicity, less energetic particle emitter radioisopotes such as Lutetium 177 may be a better option to wider the therapeutic index. TRIAL REGISTRATION: The study was registered on the NCT01469975 website with a registration code NCT01469975 on November the third, 2011.

Melanocytic Myxoid Spindle Cell Tumor With ALK Rearrangement (MMySTAR): Report of 4 Cases of a Nevus Variant With Potential Diagnostic Challenge.

Melanocytic tumors rarely display extensive dermal myxoid deposits except in the myxoid variant of melanoma. We describe in 4 patients the unusual association of morphologic and genetic features. All cases occurred in males and were located on the limbs or proximal girdle area. Age at diagnosis ranged from 8 to 47 years. Size ranged from 6 to 11 mm. Microscopic analysis showed compound, but mainly dermal melanocytic nevi, all presenting a deep dermal expansion with fascicules of amelanotic spindled cells floating in a myxoid background. Cytologic atypia and mitotic activity were low. The superficial portion was either of spitzoid or nevoid cytology with a limited junctional component. In the initial case, the dermal myxoid component was predominant with rare, barely visible, superficial melanocytic nests. This peculiar morphology was responsible for a delayed diagnostic, which required an extensive panel of antibodies ruling out most, potentially myxoid, soft tissue tumors. We later observed the presence of similar, but more limited, dermal morphologic features in 3 other cases. Immunohistochemistry in the deep myxoid areas was melanA, ALK, SOX10, and MiTF. Molecular studies confirmed the ALK rearrangement by an ALK break-apart fluorescence in situ hybridization technique and by RNA sequencing. The latter identified 4 different 5'-fusion partners. Two gene fusions were undescribed: FBXO28(e2)-ALK(e19) and NPAS2(e2)-ALK(e19), and 2 previously described: TPM3(e7)-ALK(e20) and PPFIBP1(e9)-ALK(e19). No relapse or metastatic evolution was seen during follow-up (3 to 24 mo). We denominated this potentially challenging new variant of compound nevus linked to a kinase fusion: Melanocytic Myxoid Spindle Cell Tumor with ALK Rearrangement.

Unclassified sclerosing malignant melanomas with AKAP9-BRAF gene fusion: a report of two cases and review of BRAF fusions in melanocytic tumors.

The current classification of melanocytic tumors includes clinical, pathological, and molecular data. A subset of lesions remains difficult to classify according to these complex multilayer schemes. We report two cases of deeply infiltrating melanomas with a sclerosing background. The first case occurred on the back of a middle-aged man appearing clinically as a dermatofibroma. The architectural and cytological aspects resembled those of a desmoplastic melanoma but the strong expression of both melanA and HMB45, two stainings usually reported as negative in this entity, raised the question of an alternate diagnosis. The second case was a large, slowly growing, perivulvar tumor in a middle-aged woman. The morphology was complex with a central junctional spitzoid pattern associating an epidermal hyperplasia with large nests of large spindled melanocytes. The dermal component was made of deeply invasive strands and nests of nevoid unpigmented melanocytes surrounded by fibrosis; a perineural invasion was present at the periphery of the lesion. In both cases, aCGH found, among many other anomalies, a chromosomal breakpoint at the BRAF locus. RNA sequencing identified in both an AKAP9-BRAF gene fusion. A complementary resection was performed and no relapses have been observed in the respectively 15 and 6 months of follow-up. Both of these melanomas remained unclassified. We further review the variety of melanocytic tumors associated with such BRAF fusions.

Detection of circulating tumor cells in liquid biopsy from Ewing sarcoma patients.

BACKGROUND: Circulating tumor cells (CTCs) analysis is a promising new diagnostic field to estimate risk and monitor treatment efficacy, metastatic relapse, and progression in cancer patients. The study aim was to isolate and characterize CTCs in blood samples of Ewing sarcoma (ES) patients exploiting two main characteristics: CD99 expression and presence of chromosomal translocations. MATERIALS AND METHODS: The method isolated CTCs from peripheral blood (PB) of ES patients. Cell-surface CD99 was a useful marker for CTCs determined using immunomagnetic separation with microbeads and CD99 monoclonal antibody. We tested sensitivity and specificity by detecting CTCs in blood collected from healthy donors and randomly during therapy from 18 ES patients. Evidence of CTCs was confirmed by detection of specific molecular markers using quantitative and digital reverse transcription-polymerase chain reaction targeting EWSR1/FLI1 type 1 and type 2 or EWSR1/ETS-related gene transcripts type 1 and type 9e. RESULTS: Feasibility of finding CTCs in PB of ES patients by immunoseparation with CD99 antibody and magnetic microbeads was demonstrated for the first time. At molecular analysis, three PB specimens tested positive for chimeric EWSR1/FLI1 type 2 and one PB for chimeric EWSR1/FLI1 type 2. CTCs detection was found above a limit of detection of 1 cell/mL of PB. CONCLUSION: CTCs in PB of ES patients can be identified by this method and in ES CTCs analysis can be used as a liquid biopsy approach for prognostic and predictive purposes. The potential clinical implications of CTCs in PB samples detected by the platform for CTC isolation with molecular confirmation during therapy require further evaluation.

Cutaneous Melanocytoma With CRTC1-TRIM11 Fusion: Report of 5 Cases Resembling Clear Cell Sarcoma.

We report 5 cases of primary intradermal nodular unpigmented tumors with a melanocytic immunophenotype associated with a novel CRTC1-TRIM11 fusion. Clinically, the cutaneous nodules were slowly growing in 3 women and 2 men (25 to 82 y old, median, 28 y) with no specific topography. Lesion size ranged from 4 to 12 mm (median, 5 mm). The tumors were strictly located in the dermis with a nodular pattern. The cells were arranged in confluent nests and fascicules. Central fibronecrotic areas were present in 2 cases. Cells were medium to large, sometimes multinucleated, and presented a spindled and epithelioid cytology with prominent nucleoli. Cytonuclear atypia was constant, and mitotic activity in hotspot areas ranged from 1 to 5/mm². Immunohistochemistry found a constant positivity with S100, MiTF, and Sox10, and a heterogenous staining by MelanA or HMB45. NTRK1 was strongly positive in 3 cases. In all cases, RNA sequencing found an invariable CRTC1(e1)-TRIM11(e2) fusion, confirmed by fluorescent in situ hybridization techniques with a TRIM11 break-apart probe. In 4/4 cases, nuclear TRIM11 expression was positive by immunohistochemistry. Fluorescent in situ hybridization techniques showed no rearrangement of NTRK1 or EWSR1, and array-comparative genomic hybridization displayed no alteration (1 case) or only a whole chromosome 7 gain (2 cases) when performed. No relapse or metastatic event was observed during follow-up [3 to 72 months (median, 14 mo)]. Cutaneous clear cell sarcoma was the main differential diagnosis. Overlapping morphologic features previously described in primary dermal melanomas and paraganglioma-like melanocytic tumors were present. The CRTC1-TRIM11 fusion appears to be specific of an unpigmented nodular tumor combining a melanocytic phenotype and low-grade tumor behavior.

Expression and role of TYRO3 and AXL as potential therapeutical targets in leiomyosarcoma.

BACKGROUND: Leiomyosarcoma (LMS) are 15% of adult sarcomas and remain seldom curable in metastatic phase. The TAM receptors and their ligands are overexpressed or activated in multiple malignancies, including LMS. METHODS: The TAM receptor and ligand expression was evaluated in LMS cell lines and 358 sarcoma samples by either gene expression or immunohistochemistry. TYRO3 and AXL were knocked down. Crizotinib and foretinib were investigated in vitro. RESULTS: High expression of TYRO3 and AXL was detected in LMS cell lines. TYRO3 or AXL gene knockdown reduced cell proliferation/colony formation. Crizotinib and foretinib decreased TYRO3 and AXL phosphorylation, apoptosis, G2/arrest and reduced colony formation. Immunohistochemistry performed in 107 sarcomas showed higher expression of TYRO3 and GAS6 in LMS vs other sarcomas and nuclear TYRO3 only in LMS. Microarray gene expression performed in 251 sarcomas revealed significantly higher expression of TYRO3 and GAS6 in LMS than other sarcomas. Leiomyosarcoma patients with high expression of GAS6 or PROS1 present a significantly worse PFS. CONCLUSIONS: Leiomyosarcoma patients, especially those whom develop metastasis, express higher levels of TYRO3 and GAS6. Crizotinib and foretinib showed effective antitumour activity in LMS through TYRO3 and AXL deactivation indicating that clinical trials using TYRO3 and AXL inhibitors are warranted in advanced LMS.

A novel regulation of PD-1 ligands on mesenchymal stromal cells through MMP-mediated proteolytic cleavage.

Whether fibroblasts regulate immune response is a crucial issue in the modulation of inflammatory responses. Herein, we demonstrate that foreskin fibroblasts (FFs) potently inhibit CD3+ T cell proliferation through a mechanism involving early apoptosis of activated T cells. Using blocking antibodies, we demonstrate that the inhibition of T cell proliferation occurs through cell-to-cell interactions implicating PD-1 receptor expressed on T cells and its ligands, PD-L1 and PD-L2, on fibroblasts. Dual PD-1 ligand neutralization is required to abrogate (i) binding of the PD-1-Fc fusion protein, (ii) early apoptosis of T cells, and (iii) inhibition of T cell proliferation. Of utmost importance, we provide the first evidence that PD-1 ligand expression is regulated through proteolytic cleavage by endogenous matrix metalloproteinases (MMPs) without transcriptional alteration during culture-time. Using (i) different purified enzymatic activities, (ii) MMP-specific inhibitors, and (iii) recombinant human MMP-9 and MMP-13, we demonstrated that in contrast to CD80/CD86, PD-L1 was selectively cleaved by MMP-13, while PD-L2 was sensitive to broader MMP activities. Their cleavage by exogenous MMP-9 and MMP-13 with loss of PD-1 binding domain resulted in the reversion of apoptotic signals on mitogen-activated CD3+ T cells. We suggest that MMP-dependent cleavage of PD-1 ligands on fibroblasts may limit their immunosuppressive capacity and thus contribute to the exacerbation of inflammation in tissues. In contrast, carcinoma-associated fibroblasts appear PD-1 ligand-depleted through MMP activity that may impair physical deletion of exhausted defective memory T cells through apoptosis and facilitate their regulatory functions. These observations should be considered when using the powerful PD-1/PD-L1 blocking immunotherapies.

Clinical effect of molecular methods in sarcoma diagnosis (GENSARC): a prospective, multicentre, observational study.

BACKGROUND: Advances in molecular genetics of sarcoma have enabled the identification of type-specific aberrations. We aimed to assess the clinical effect of systematic implementation of molecular assays to improve sarcoma misdiagnosis. METHODS: In this multicentre, observational study, we recruited patients from 32 centres of the French Sarcoma Group/Reference Network in Pathology of Sarcomas. Eligibility criteria included: biopsy or surgical resection; suspicion of: dermatofibrosarcoma protuberans (cohort 1), dedifferentiated liposarcoma (cohort 2), Ewing's sarcoma family of tumours (cohort 3), synovial sarcoma (cohort 4), alveolar rhabdomyosarcoma (cohort 5), and myxoid or round cell liposarcoma (cohort 6); review by one sarcoma-expert pathologist; availability of frozen material (except for cohort 1 of patients with dermatofibrosarcoma protuberans because anti-CD34 immunohistochemistry is performed on paraffin-embedded tissue); and patient information. For each case, the pathologist made one primary diagnosis followed by up to two differential diagnoses, based on histological characteristics only. Each diagnosis was classified as certain, probable, or possible. For each case to determine the molecular classification, we did fluorescence in-situ hybridisation on paraffin-embedded samples. We also did comparative genomic hybridisation and quantitative PCR (cohort 2) or reverse transcriptase PCR (cohorts 3-6) on frozen and paraffin-embedded samples. We made a final diagnosis based on the molecular results. The clinical effect of diagnosis correction was assessed by a board of experts. FINDING: Between June 22, 2009, and Oct 30, 2012, 395 patients were enrolled in the study, of which 384 were eligible for inclusion. The diagnosis was eventually modified by molecular genetics for 53 patients: eight (16%) of 50 patients with dermatofibrosarcoma (cohort 1), seven (23%) of 30 patients with dedifferentiated liposarcoma (cohort 2), 13 (12%) of 112 with Ewing's sarcoma family of tumours (cohort 3), 16 (16%) of 97 patients with synovial sarcoma (cohort 4), seven (15%) of 46 patients with alveolar rhabdomyosarcoma (cohort 5), and two (4%) of 49 patients with myxoid or round cell liposarcoma (cohort 6), with an effect on primary management or prognosis assessment in 45 cases. INTERPRETATION: Molecular genetic testing should be mandatory for diagnostic accuracy of sarcoma and appropriate clinical management, even when histological diagnosis is made by pathologist experts in this field. FUNDING: French National Cancer Institute and Nice University Hospital.

KIT exon 10 variant (c.1621 A > C) single nucleotide polymorphism as predictor of GIST patient outcome.

BACKGROUND: Tumor genotype plays a crucial role in clinical management of GIST. Whether genetic polymorphism of KIT may influence GIST patient outcome is unclear. METHODS: We investigated the biological and clinical significance of the presence of KIT exon 10 variant (c.1621 A > C), KIT (L541), in a transfected cell line (3 T3 L541) and in two retrospectively collected series of 109 GIST patients in total. The control group consisted of 60 healthy donors collected at the French department of blood transfusion. RESULTS: In the 3 T3 L541 cell line, KIT(L541) protein exhibited a spontaneous phosphorylation status comparable to that of wild-type KIT but displayed a phosphorylation pattern of AKT and ERK1/2 that was found similar to that of the classical mutated forms of the KIT receptor. Of 109 patients enrolled in this retrospective translational research study, 24 (22%) harboured KIT (L541), similarly to the control group of healthy donors (n = 10 of 60, 17%). A higher prevalence of the variant KIT (L541) was observed in patients with metastatic status at diagnosis (KIT (L541) correlated nine of 22 versus 15 of 87, p = 0.02). In addition, patients with KIT (L541) and localized GIST had a higher rate of relapse at 5 years and lower relapse free survival at 5 years in univariate, as well as in multivariate analysis. Response rate and duration of response to imatinib was similar in KIT (L541) and KIT (M541) patients. CONCLUSION: KIT (L541) genotype is associated with a higher risk of metastasis at diagnosis and a higher risk of relapse in GIST patients.

Prediction of desmoid tumor progression using miRNA expression profiling.

Desmoid tumor is a rare connective tissue tumor with locoregional aggressiveness but unpredictable behavior. The miRNA profile was ascertained for 26 patients included in the Desminib phase II trial and an independent validation cohort of 15 patients. Predictive and prognostic supervised analysis on the Desminib cohort failed to identify miRNAs differentially expressed between progressive and non-progressive patients under imatinib treatment or between progressive and non-progressive patients after discontinuation of imatinib. However, an unsupervised hierarchical clustering of the Desminib cohort identified two groups (A and B) of 13 patients each, where only the number of previous lines of treatment before inclusion in the study differed significantly between the two groups. Time to progression after discontinuation of imatinib was longer in group B than in group A. Fifteen miRNAs were highly statistically differentially expressed between groups A and B, targeting more than 3000 genes, including AGO1, BCL2, CDK6, SMAD4, PTEN, CCND1, VEGFA, and RB1. These results were confirmed in the independent validation cohort: hierarchical clustering of these 15 miRNAs identified two groups, in which time to recurrence was statistically different (28.8 months vs 68.8 months). These results provide the first indication of the prognostic value of miRNA expression profiling with a possible direct impact on patient management. A more precise miRNA signature must now be determined to select patients who would not benefit from surgical resection of their tumor and who ought to be monitored without treatment.

Impact of KIT exon 10 M541L allelic variant on the response to imatinib in aggressive fibromatosis: analysis of the desminib series by competitive allele specific Taqman PCR technology.

BACKGROUND: Aggressive fibromatosis (AF) is a rare fibroblastic proliferative disease with a locally aggressive behavior and no distant metastasis, characterized by driver mutations in CTNNB1 or the APC gene. When progressive and/or symptomatic AF is not amenable to local management, a variety of medical treatments may be efficient, including imatinib mesylate. The phase II "Desminib trial" included 40 patients with AF to evaluate the toxicity and efficacy of imatinib resulting in a 65% tumor control rate at 1 year. We investigated a potential predictive value of KIT exon 10 M541L variant (KITL541) on this prospective series. METHODS: DNA was extracted in sufficient quantity from 33 patients included in the Desminib trial. The detection of KITL541 was performed by Competitive Allele-Specific Taqman® PCR technology. Chi-2 analyses were performed to search for a correlation between KIT status and tumor response. Progression free (PFS) and overall survival (OS) were compared by log-rank test after Kaplan-Meier analysis. RESULTS: In 6 out of 33 cases (18%), the technique failed to determine the mutational status; 5 patients (19%) harboured KITL541 and 22 patients (81%) were classified as KIT wild type. Compared with total cohort, KITL541 frequency did not distinguish between different clinical characteristics. In the KITL541 and the KITWT subgroups, the tumor control rate at 1 year was 100% and 68%, respectively (p = 0.316). The median PFS of patients harboring KITL541 or not is 29.9 and 24.5 months, respectively (p = 0.616), and the median OS is not reached, in any of the groups. CONCLUSION: Our results do not support a predictive effect of KITL541 on the efficacy of imatinib for patients with AF.

Impact of molecular analysis on the final sarcoma diagnosis: a study on 763 cases collected during a European epidemiological study.

Sarcomas are rare, heterogenous, and often difficult to classify. A large proportion of sarcomas are associated with specific molecular genetic lesions such as translocations, mutations, and amplifications, which are helpful in the diagnosis of individual cases. However, the exact impact of molecular genetics on the final diagnosis of sarcomas is unknown. In this study, all soft tissue and visceral sarcomas arising in patients living in 3 European regions in 2 countries (representing 13 million inhabitants) were collected and reviewed during 2 consecutive years. A molecular analysis was performed for all suspicions of sarcomas with specific genetic lesions [mutations of KIT/PDGFRA in gastrointestinal stromal tumors (GISTs), reciprocal translocation, or amplification of MDM2 in atypical lipomatous tumors, well-differentiated liposarcoma-dedifferentiated liposarcoma (ALT/WDLPS-DDLPS)]. To evaluate the impact of molecular tests, a premolecular analysis diagnosis was proposed with 3 categories of certainty: certain, probable, or possible. A molecular analysis was performed in 763/1484 tumors corresponding to 295 cases in which GIST was suspected, 248 sarcomas with a suspicion of translocation, and 220 cases in which ALT/WDLPS-DDLPS was suspected. Molecular analysis was found to be useful (confirms a probable diagnosis) in 11 (4%) GISTs, 62 (26%) suspicions of translocation, and 66 (31%) suspicions of ALT/WDLPS-DDLPS; and necessary (allows a possible diagnosis) in 2 (<1%) GISTs, 31 (12%) suspicions of translocation, and 19 (9%) suspicions of ALT/WDLPS-DDLPS. This study performed in an epidemiological setting demonstrates the significant impact of molecular analysis on the final sarcoma diagnosis and favors such an analysis on any tumor with a suspicion of a specific genomic abnormality and for which the diagnosis is uncertain.

Gene expression patterns of hemizygous and heterozygous KIT mutations suggest distinct oncogenic pathways: a study in NIH3T3 cell lines and GIST samples.

OBJECTIVE: Most gain of function mutations of tyrosine kinase receptors in human tumours are hemizygous. Gastrointestinal stromal tumours (GIST) with homozygous mutations have a worse prognosis. We aimed to identify genes differentially regulated by hemizygous and heterozygous KIT mutations. MATERIALS AND METHODS: Expression of 94 genes and 384 miRNA was analysed with low density arrays in five NIH3T3 cell lines expressing the full-length human KIT cDNA wild-type (WT), hemizygous KIT mutation with del557-558 (D6) or del564-581 (D54) and heterozygous WT/D6 or WT/D54. Expression of 5 of these genes and 384 miRNA was then analysed in GISTs samples. RESULTS: Unsupervised and supervised hierarchical clustering of the mRNA and miRNA profiles showed that heterozygous mutants clustered with KIT WT expressing cells while hemizygous mutants were distinct. Among hemizygous cells, D6 and D54 expressing cells clustered separately. Most deregulated genes have been reported as potentially implicated in cancer and severals, as ANXA8 and FBN1, are highlighted by both, mRNA and miRNA analyses. MiRNA and mRNA analyses in GISTs samples confirmed that their expressions varied according to the mutation of the alleles. Interestingly, RGS16, a membrane protein of the regulator of G protein family, correlate with the subcellular localization of KIT mutants and might be responsible for regulation of the PI3K/AKT signalling pathway. CONCLUSION: Patterns of mRNA and miRNA expression in cells and tumours depend on heterozygous/hemizygous status of KIT mutations, and deletion/presence of TYR568 & TYR570 residues. Thus each mutation of KIT may drive specific oncogenic pathways.