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Although most small B-cell lymphomas (SBCLs) can be diagnosed using routine methods, challenges exist. For example, marginal zone lymphomas (MZLs) can be difficult to rule-in, in large part because no widely-used, sensitive, and specific biomarker is available for the marginal zone cell of origin. In this study, it was hypothesized that DNA methylation array profiling can assist with the classification of SBCLs, including MZLs. Extramedullary SBCLs, including challenging cases, were reviewed internally for pathology consensus and profiled. By combining the resulting array data set with data sets from other groups, a set of 26 informative probes was selected and used to train machine learning models to classify 4 common SBCLs: chronic lymphocytic leukemia/small lymphocytic lymphoma, follicular lymphoma, mantle cell lymphoma, and MZL. Prediction probability cutoff was used to separate classifiable from unclassifiable cases, and show that the trained model was able to classify 95% of independent test cases (n = 264/279). The concordance between model predictions and pathology diagnoses was 99.6% (n = 262/263) among classifiable test cases. One validation reference test case was reclassified based on model prediction. The model was also used to predict the diagnoses of two challenging SBCLs. Although the differential examined and data on difficult cases are limited, these results support accurate methylation-based classification of SBCLs. Furthermore, high specificities of predictions suggest that methylation signatures can be used to rule-in MZLs.

BackgroundGenetic testing for hereditary cancer susceptibility has advanced over time due to the discovery of new risk genes, improved technology and decreased cost. In the province of Ontario, testing eligibility criteria were initially developed to include hereditary breast, ovarian and colorectal cancer syndromes. The rapid evolution of genetic technologies has facilitated the ability to interrogate a large number of genes concurrently. This, coupled with new knowledge about risk genes, necessitated a coordinated approach to expanding the scope of genes and indications tested and synchronisation of access and test utilisation across the province as required in a publicly funded universal healthcare system.MethodsOntario Health—Cancer Care Ontario convened expert working groups to develop a standardised and comprehensive cancer gene list for adults and accompanying hereditary cancer testing (HCT) criteria using an evidence-based framework and broad laboratory and clinical genetics engagement.ResultsA standardised 76-cancer-gene panel, organised into 13 larger disease site panels and 25 single/small gene panels, was developed and endorsed by the working groups. Provincial genetic testing eligibility criteria were updated to align with the new panels and to guide clinical decision-making. In the first year following the implementation of these changes, 10 564 HCT panels were performed with an overall mutation detection rate of 12.2%.ConclusionUsing an evidence framework and broad clinical engagement to develop and endorse an updated guidance document, cancer genetic testing for adults in Ontario is now standardised and coordinated across the province.

When performing a genetic test the identification of a variation from the reference sequence is important but much work needs to be done before that identification can lead to a diagnosis. DNA variants require interpretations which ought to be thorough and require the reviewer to have expertise in medical genetics. Interpretations are exceedingly important, when performed incorrectly they can lead to false negatives or false positives. Variants not given the proper attention can be called uncertain when a more conclusive assessment could be given. Here we attempt to cover important areas relating to evidence utilized in DNA variant assessments from a medical genetics perspective. We hope to display that the phenotypes of the patient being tested as well as the phenotypes of the subjects behind much of the data in the assessment should always be considered.

Measurable (minimal) residual disease (MRD) is an established, key prognostic factor in adult B-cell acute lymphoblastic leukemia (B-ALL), and testing for MRD is known to be an important tool to help guide treatment decisions. The clinical value of MRD testing depends on the accuracy and reliability of results. Currently, there are no Canadian provincial or national guidelines for MRD testing in adult B-ALL, and consistent with the absence of such guidelines, there is no uniform Ontario MRD testing consensus. Moreover, there is great variability in Ontario in MRD testing with respect to where, when, and by which technique, MRD testing is performed, as well as in how the results are interpreted. To address these deficiencies, an expert multidisciplinary working group was convened to define consensus recommendations for improving the provision of such testing. The expert panel recommends that MRD testing should be implemented in a centralized manner to ensure expertise and accuracy in testing for this low volume indication, thereby to provide accurate, reliable results to clinicians and patients. All adult patients with B-ALL should receive MRD testing after induction chemotherapy. Philadelphia chromosome (Ph)-positive patients should have ongoing monitoring of MRD during treatment and thereafter, while samples from Ph-negative B-ALL patients should be tested at least once later during treatment, ideally at 12 to 16 weeks after treatment initiation. In Ph-negative adult B-ALL patients, standardized, ideally centralized, protocols must be used for MRD testing, including both flow cytometry and immunoglobulin (Ig) heavy chain and T-cell receptor (TCR) gene rearrangement analysis. For Ph-positive B-ALL patients, MRD testing using a standardized protocol for reverse transcription real-time quantitative PCR (RT-qPCR) for the BCR-ABL1 gene fusion transcript is recommended, with Ig/TCR gene rearrangement analysis done in parallel likely providing additional clinical information.

Despite continuing improvements in the management of classical Hodgkin lymphoma (cHL), relapse remains associated with a risk of lymphoma-related mortality. The biological composition of relapse tumour biopsies shows interpatient variability, which can be leveraged to design prognostic biomarkers. Here, we validated the RHL30 assay, a previously reported gene expression model in an independent cohort of 41 patients with relapsed cHL. Patients classified as high-risk by the RHL30 assay had inferior failure-free survival (FFS) after autologous stem cell transplantation (2-year FFS 41% vs. 92%, P = 0·035). The RHL30 model is a robust biomarker that risk-stratifies patients considered for autologous stem cell transplantation.

The number of druggable tumor-specific molecular aberrations has grown substantially in the past decade, with a significant survival benefit obtained from biomarker matching therapies in several cancer types. Molecular pathology has therefore become fundamental not only to inform on tumor diagnosis and prognosis but also to drive therapeutic decisions in daily practice. The introduction of next-generation sequencing technologies and the rising number of large-scale tumor molecular profiling programs across institutions worldwide have revolutionized the field of precision oncology. As comprehensive genomic analyses become increasingly available in both clinical and research settings, healthcare professionals are faced with the complex tasks of result interpretation and translation. This review summarizes the current and upcoming approaches to implement precision cancer medicine, highlighting the challenges and potential solutions to facilitate the interpretation and to maximize the clinical utility of molecular profiling results. We describe novel molecular characterization strategies beyond tumor DNA sequencing, such as transcriptomics, immunophenotyping, epigenetic profiling, and single-cell analyses. We also review current and potential applications of liquid biopsies to evaluate blood-based biomarkers, such as circulating tumor cells and circulating nucleic acids. Last, lessons learned from the existing limitations of genotype-derived therapies provide insights into ways to expand precision medicine beyond genomics.

e19303 Background: There is limited real-world evidence of impact of large clinical panel sequencing on treatment-matching for patients with advanced solid tumors. The province of Ontario has a single payer, publicly funded health care system. We linked genomic testing results from a prospective province-wide trial, OCTANE (Ontario-Wide Cancer TArgeted Nucleic Acid Evaluation), to administrative data to determine the feasibility of this approach for evaluating survival and the impact of sequencing on treatment matching. Methods: We linked all Ontario patients from Princess Margaret (PM) with panel testing results (tumor-only 555-gene panel) to province-wide administrative data on treatments and outcomes. Patients were recruited from August 2016 to August 2018. Only clinically actionable variants based upon OncoKB annotation (Level 1 and 2) were assessed for genotype-informed treatment matching. Results: All 888 eligible patients were successfully linked to administrative data. Mean age was 58 (±13) years, 635 (71.5%) were female. Most common disease sites were ovary (26.4%), uterus (14.0%), colorectal (11.8%) and breast (9.5%). Administrative data vital status was more complete than trial collected data with 262 of 476 deaths only recorded in administrative data. Median survival was 1.70 years (95% confidence interval 1.50-1.91). 247 (27.8%) had actionable mutations, most commonly PIK3CA (54.7%), BRCA1 (15.8%), BRCA2 (15.0%) and BRAF (8.9%). 37 (15.0%) and 42 (17.0%) patients with actionable mutations received targeted therapy within 6 and 12 months of test report date, respectively. Conclusions: This is the first known feasibility study of linked administrative data to measure outcomes of large clinical panel sequencing for patients with advanced solid tumors. Vital status was more complete with administrative data compared to trial-collected data, and treatment data was successfully linked. About one in twenty-one enrolled patients received genome-informed treatments within 12 months, or about one in six of all patients with actionable mutations. This may be due to short interval follow up, trial and drug access, successful standard of care treatments, early patient deterioration or limited alterations covered by the panel, among other causes.

3562 Background: Next generation sequencing targeted panels increasingly inform clinical decisions, but may miss actionable findings detectable by whole exome sequencing (WES) and RNA-seq. There has been no direct comparison of WES plus RNA-seq against targeted panel sequencing to determine its added utility. To address this, we performed WES and RNA-seq analysis in a cohort of 100 patients with no actionable findings on prior panel sequencing. Methods: Ontario-wide Cancer Targeted Nucleic Acid Evaluation (OCTANE; NCT02906943) has sequenced 2,106 patients using a 161-gene Oncomine or 555-gene Hi5 panel. 100 patients (98 Hi5, 2 Oncomine) were chosen for further sequencing. Tumor (100x coverage) and normal (50x) exomes and tumor transcriptomes were sequenced on Illumina HiSeq2500 or NextSeq550. Interpretation included knowledgebase annotation (e.g. OncoKB, CIViC), mutation signatures, homologous recombination deficiency (HRD) scores, gene expression, and pathway analysis. Findings were deemed “actionable” if they could directly inform management or trial eligibility. Results: WES and RNA-seq identified one or more novel actionable findings in 38 patients. Of these, the main actionable finding was tumor mutation burden (TMB), mutation signature, or HRD score in 19 (50%), a copy number variant in 16 (42%), a fusion in 2 (5%), and a point mutation in 1 (2.6%). WES identified a MALAT1-GLI1 fusion in a cancer of unknown primary (CUP) whose transcriptome was consistent with gastric cancer, together suggesting the diagnosis of a rare gastroblastoma. To date, two cases have received exome-supported targeted therapy: (1) a metastatic high grade serous ovarian cancer, HRD-high, treated with olaparib then cisplatin for a combined 15 months, and (2) a metastatic neuroendocrine rectal tumor with RICTOR amplification treated with everolimus starting in Dec 2016 until last follow-up in Sep 2019. Of 62 patients with no actionable finding, expanded sequencing identified one or more known cancer drivers in 25 (40%): 17 CNVs, 3 fusions, and 5 point mutations or indels. In 16 patients, an oncogenic variant found on panel was not captured by WES, and may represent artifacts, germline mutations, or subclonal/localized variants. Conclusions: WES and RNA-seq expanded detection of actionable biomarkers and oncogenic mutations, especially CNV, TMB/signatures, and HRD. Two cases have undergone exome-supported targeted treatment. We performed the first WES of a rare gastroblastoma, originally a CUP but reclassified by expanded fusion detection and RNA-seq.

Immunohistochemistry (IHC) for mismatch repair (MMR) proteins is used to identify MMR status: being diffusely positive (intact/retained nuclear staining) or showing loss of nuclear tumour staining (MMR protein deficient). Four colonic adenocarcinomas and a gastric adenocarcinoma with associated dysplasia that displayed heterogenous IHC staining patterns in at least one of the four MMR proteins were characterised by next‐generation sequencing (NGS). In order to examine a potential molecular mechanism for these staining patterns, the respective areas were macrodissected, analysed for microsatellite instability (MSI) and investigated by NGS and multiplex ligation‐dependent probe amplification (MLPA) analysis of MLH1, MSH2, MSH6 and PMS2 genes, including MLH1 methylation analysis. One colonic adenocarcinoma showed heterogenous MSH6 IHC staining and molecular analysis demonstrated increasing allelic burden of two MSH6 frameshift variants (c.3261delC and c.3261dupC) in areas with MSH6 protein loss compared to areas where MSH6 was retained. Two colonic adenocarcinomas with heterogenous MLH1 staining showed no differences in sequence variants. In one of these cases, however, MLH1 was hypermethylated in the area of MLH1 loss. Another colon carcinoma with heterogenous PMS2 staining (but with retained MSH6) showed both MSH6 c.3261dupC and 3260_3261dupCC where PMS2 protein was lost and only c.3261dupC where PMS2 was retained. The gastric carcinoma showed complete loss of MSH6 in dysplastic foci, while the underlying invasive carcinoma showed retention of MSH6. Both these areas, however, were MSI‐high and showed the same MSH6 variant: c.3261delC. The gastric dysplasia additionally showed MSH6 c.3261dupC. In four of the five cases where MMR protein was lost, these areas were MSI‐high. Heterogenous MMR IHC (focal and/or zonal within the same tumour or between invasive and dysplastic preinvasive areas) is not always due to artefact and is invariably related to MSI‐high status in the areas of loss. An interesting aspect to this study is the presence of MSH6 somatic mutations irrespective of whether MSH6 IHC staining was intact or lost.

Craniosynostosis is a clinically and genetically heterogeneous condition. Knowledge of the specific genetic diagnosis in patients presenting with this condition is important for surgical and medical management. The most common single gene causes of syndromic craniosynostosis are mutations in FGFR1, FGFR2, FGFR3, TWIST1, and EFNB1. Recently, a new single gene cause of craniosynostosis was published, together with phenotype data that highlight the clinical importance of making this specific molecular diagnosis. Phenotypic features of "ERF-related craniosynostosis" include sagittal or multiple-suture synostosis, Chiari malformation, and language delay. In order to determine the contribution of ERF mutations to genetically undiagnosed patients with craniosynostosis, we sequenced the coding regions of ERF in 40 patients with multi-suture or sagittal suture synostosis. We identified heterozygous ERF mutations in two individuals (5%). One mutation positive individual had pansynostosis, while the second had bilateral coronal and metopic synostosis. Both presented in infancy or childhood (age 3 months, and 6 years 9 months, respectively). One had CNS abnormalities including Chiari I malformation. Dysmorphic features included hypertelorism, proptosis, depressed nasal bridge, and retrognathia, in keeping with previously reported cases. The individuals did not require repeated cranial surgeries. ERF-related craniosynostosis should be suspected in patients presenting with multiple suture or sagittal synostosis.

Migration of smooth muscle cells from the arterial media to the intima is central to several vascular pathologies including restenosis. This study demonstrates that, like directional migration of other cells, smooth muscle migration is accompanied by a dramatic, polarized reorganization of the cell cytoskeleton that is accompanied by activation of the Rho GTPase Cdc42 and inactivation of glycogen synthase kinase-3β. We also show, for the first time, that signals generated at the posterior–lateral aspects of wound edge cells by the cell–cell adhesion molecule N-cadherin are required for polarization and rapid migration of vascular smooth muscle. Importantly, when a cohort of migrating smooth muscle cells encounter CHO cells or the A10 smooth muscle cell line, neither of which expresses N-cadherin, polarity is only slightly suppressed. However, when smooth muscle cells encounter stably transfected, N-cadherin–expressing A10 cells or (N-cadherin–expressing) vascular endothelium, they rapidly lose their polarized phenotype. The latter finding indicates that endothelial signaling to innermost smooth muscle cells via N-cadherin may be critical to normal vessel wall stability. We infer that asymmetrical distribution of N-cadherin is necessary for the establishment of cell polarity during migration and that N-cadherin ligation is highly effective in abrogating polarized migration. Finally, we showed that endothelial cell polarity does not depend on N-cadherin; therefore, this molecule may be an attractive target for therapies to prevent restenosis without suppressing endothelial repair and risking late thrombosis.

Insulin-like growth factor-I (IGF-I) is elevated in human fibrotic lung diseases and in animal models of pulmonary fibrosis, implicating IGF-I in the pathogenesis of fibrotic lung disease. We questioned whether IGF-I protein levels were enhanced in fibroproliferative acute respiratory distress syndrome (FP-ARDS). Serial lung tissue sections from a biopsy database were immunohistochemically stained for IGF-I, IGF-I receptor, CD68, alpha-smooth muscle actin, collagens I and III, and proliferating cell nuclear antigen. Our results show enhanced staining of IGF-I and IGF-I receptor, collagens I and III, smooth muscle actin, CD68, and proliferating cell nuclear antigen in FP-ARDS compared with control lung sections. In FP-ARDS specimens, prominent staining of IGF-I and IGF-I receptor was seen in alveolar and interstitial macrophages as well as in a variety of mesenchymal cells. There was a correlation between IGF-I staining and CD68-positive cells, suggesting macrophages as a potential source of the IGF-I protein present in lungs. IGF-I also correlated with enhanced collagen I, collagen III, and proliferating cell nuclear antigen immunoreactivity, suggesting that IGF-I may play a role in the extracellular matrix protein deposition and cellular proliferation seen in the lungs of individuals with FP-ARDS. Our results indicate that IGF-I is increased in FP-ARDS and may be an important mediator in the progression of acute lung injury to FP-ARDS.

Danon disease is a rare X-linked disorder comprising hypertrophic cardiomyopathy, skeletal myopathy, intellectual disability, and retinopathy; mutations of the lysosome-associated membrane protein gene LAMP2 are responsible. Most affected persons exhibit "private" point mutations; small locus rearrangements have recently been reported in four cases. Here, we describe the clinical, pathologic, and molecular features of a male proband and his affected mother with Danon disease and a small LAMP2 microduplication. The proband presented at age 12 years with exercise intolerance, hypertrophic cardiomyopathy, and increased creatine kinase. Endomyocardial biopsy findings were nonspecific, showing myocyte hypertrophy and reactive mitochondrial changes. Quadriceps muscle biopsy demonstrated the characteristic autophagic vacuoles with sarcolemma-like features. LAMP2 tissue immunostaining was absent; however, LAMP2 sequencing was normal. Deletion/duplication testing by multiplex ligation-dependent probe amplification (MLPA) assay revealed a 1.5kb microduplication containing LAMP2 exons 4 and 5. RT-PCR studies were consistent with the inclusion of these two duplicated exons in the final spliced transcript, resulting in a frameshift. The proband's mother, who had died following cardiac transplantation due to suspected myocarditis at age 35, was reviewed and was shown to be affected upon immunostaining of banked myocardial tissue. This case constitutes the second report of a pathogenic microduplication in Danon disease, and illustrates a number of potential diagnostic pitfalls. Firstly, given the imperfect sensitivity of LAMP2 sequencing, tissue immunostaining and/or MLPA should be considered as a diagnostic adjunct in the workup for this disorder. Secondly, the pathological findings in myocardium may be falsely indicative of relatively common conditions such as myocarditis.

The extracellular matrix signals and regulates the behavior of vascular cells during the pathogenesis of atherosclerosis. Type VIII collagen, a short chain collagen, is scarcely present in normal arteries, but is dramatically upregulated in atherosclerosis and after other types of vascular injury. Cell culture studies have revealed that this protein supports smooth muscle cell (SMC) adhesion and stimulates migration, however little is known about the signaling or the mechanisms by which this occurs. SMCs isolated from wild-type C57BL/6 and type VIII collagen deficient mice were studied using assays to measure chemotactic and haptotactic migration, and remodeling and contraction of 3-dimensional type I collagen gels. Col8 −/− SMCs exhibited impairments in migration, and a strongly adhesive phenotype with prominent stress fibers, stable microtubules and pronounced central basal focal adhesions. The addition of exogenous type VIII collagen to the Col8 −/− SMCs rescued the impairments in migration, and restored cytoskeletal architecture so that it was similar to Col8 +/+ cells. We measured elevated levels of active GTP-RhoA in the Col8 −/− cells, and this too was reversed by treatment with exogenous type VIII collagen. We showed that type VIII collagen normally suppresses RhoA activation through a beta-1 integrin dependent mechanism. MMP-2 levels were reduced in the Col8 −/− SMCs, and knockdown of MMP-2 in Col8 +/+ SMCs partially recapitulated the decreases in migration and 3D gel contraction seen in Col8 −/− cells, showing that type VIII collagen-stimulated migration was dependent on MMP-2. Inhibition of Rho restored MMP-2 activity in the Col8 −/− cells, and partially rescued migration, demonstrating that the elevations in RhoA activity were responsible for the suppression of migration of these cells. In conclusion, we have shown that type VIII collagen signals through beta-1 integrin receptors to suppress RhoA, allowing optimal configuration of the cytoskeleton, and the stimulation of MMP-2-dependent cell migration.

Cadherins aggregate and stabilize cell–cell junctions through interactions with adjacent cells. In addition, N-cadherin and E-cadherin concentrate at free edges or at the lamellipodia of migrating cells and are found within large vesicles called macropinosomes, which develop from membrane ruffles. The binding properties of cadherins have not previously been associated with the localization of cadherins at membrane ruffles; however, we report that the dorsal, ventral and lateral membrane contacts that occur as a result of the overlap of membrane ruffles aggregate N-cadherin, and that both N-cadherin and E-cadherin promote macropinosome closure and fluid-phase uptake in macropinosomes. These data reveal a previously unsuspected function for cadherin-mediated cell–cell adhesion molecules in the closure of cell-autonomous membrane contacts at membrane ruffles, resulting in macropinocytosis.

Arteries display highly directional growth and remodeling that are specific to increases in the mechanical loads imposed on them by blood pressure, blood flow, and lengthwise tensile forces that are transmitted from the tissues to which they are attached. This study examined the effect of mechanical forces on the direction in which mitosis delivers daughter cells, as a mechanism for directional growth. Lateral forces were imposed on surface integrins of cultured endothelial cells by seeding the cells with arginine-glycine-aspartate peptide–coated magnetic microspheres and applying a magnetic field. Video images revealed that the mitotic axis of dividing cells became highly biased in the direction of applied force. Distribution of cortactin, which participates in polarized mitoses driven by other stimuli, was highly sensitive to mechanical loading and interfering with cortactin function arrested cell growth. Smooth muscle cell mitoses also proved to be sensitive to mechanical force: when lengthwise force imposed on rabbit carotid arteries was altered by excision of a vessel segment and reanastomosis of the cut ends, direction of mitosis was dramatically altered. These findings indicate that influences of mechanical force can modulate the manner in which mitosis of vascular cells contributes to reorganization of arterial wall tissue.

Objective— Smooth muscle cell migration is critical to neointimal formation after arterial injury. The purpose of this study was to elucidate the regulation and functional significance of cell-cell adhesion via adherens junctions during this process. Methods and Results— Using balloon catheter injury of rat carotid artery, we showed that neointimal formation is accompanied by dramatic but transient upregulation of intimal N-cadherin and associated catenins, proteins that mediate adhesion at adherens junctions. Upregulation was demonstrated by immunofluorescence microscopy and by immunoblotting, and it coincided with evidence of phenotypic modulation of smooth muscle cells. Similar upregulation was observed when postconfluent cultures of porcine aortic smooth muscle cells were subjected to linear denuding injuries. Furthermore, treatment of wounded cultures with a blocking antibody against the extracellular domain of the N-cadherin protein significantly suppressed the repair of wounds. Conclusions— N-cadherin and associated proteins are dynamically regulated during neointimal formation and provide evidence that this regulation is important for migratory repair. Therefore, N-cadherin may provide a novel target for therapies that are directed toward intimal proliferative disorders, including restenosis and vascular bypass graft failure.

disease. Clinical improvements observed consist of improved muscle function and regression of rest pain or angina. However, direct evidence for improved vascularization, as evaluated by angiography, is weak. We here report an unexpected effect that occurred in ischaemic hind limb muscle of mice treated with intramuscular adenoviral gene transfer of VEGF-A, namely the increase of myoglobin. Myoglobin is a hemecontaining protein, expressed in cardiomyocytes and skeletal myocytes, that ameliorates oxygen storage in and supply to muscle cells. Both the number of myoglobin-stained muscle fibers and active myoglobin concentration were increased in calf muscle of Ad.VEGFversus Ad.LacZ-treated mice (18±4.3 versus 7.0±4.1% and 64±6.8 versus 43±3.9 mg myoglobin/ mg dry-weight respectively, N = 6). Another effect of Ad.VEGF treatment was an increase of capillaries (409±74 vs. 185±24 capillaries/mm2, N = 6), however no increase of collateral arteries was observed as compared to Ad.LacZ (angiographic Rentrop scores 1.9±0.4 versus 1.9±0.3, N = 6). To study whether VEGF can act directly on muscle cells to enhance myoglobin expression, we performed an experiment with VEGF protein in differentiated murine C2C12 myoblasts in culture. Indeed, a 3-fold increase of myoglobin mRNA was shown in VEGFversus PBS-treated myoblasts, using Real Time RT-PCR analysis. In addition, co-expression of VEGF and myoglobin was observed in ischaemic muscle tissue of 15 limb amputation patients, suggesting a correlation between both proteins. Moreover, an increased level of ischaemia was correlated with an increase in both VEGF and myoglobin expression (Signs-test p = .018 and .047 respectively). In conclusion, VEGF (gene) therapy results in enhanced myoglobin expression in skeletal muscle in vitro and in vivo. Furthermore, we show correlated expression of VEGF and myoglobin in muscle from limb amputation patients. The increased myoglobin expression in VEGF-treated muscle implies an improved muscle oxygenation, which may, partly, explain the previously observed clinical improvements, such as regression of claudication or angina, in VEGF-treated patients. Poster Abstracts / Cardiovascu S134