Evaluating Circulating Biomarkers for Diagnosis, Prognosis, and Tumor Monitoring in Pediatric Sarcomas: Recent Advances and Future Directions.

Pediatric sarcomas present a significant challenge in oncology. There is an urgent need for improved therapeutic strategies for high-risk patients and better management of long-term side effects for those who survive the disease. Liquid biopsy is emerging as a promising tool to optimize treatment in these patients by offering non-invasive, repeatable assessments of disease status. Circulating biomarkers can provide valuable insights into tumor genetics and treatment response, potentially facilitating early diagnosis and dynamic disease monitoring. This review examines the potential of liquid biopsies, focusing on circulating biomarkers in the most common pediatric sarcomas, i.e., osteosarcoma, Ewing sarcoma, and rhabdomyosarcoma. We also highlight the current research efforts and the necessary advancements required before these technologies can be widely adopted in clinical practice.

Whole-genome sequencing facilitates patient-specific quantitative PCR-based minimal residual disease monitoring in acute lymphoblastic leukaemia, neuroblastoma and Ewing sarcoma.

BACKGROUND: Minimal residual disease (MRD) measurement is a cornerstone of contemporary acute lymphoblastic leukaemia (ALL) treatment. The presence of immunoglobulin (Ig) and T cell receptor (TCR) gene recombinations in leukaemic clones allows widespread use of patient-specific, DNA-based MRD assays. In contrast, paediatric solid tumour MRD remains experimental and has focussed on generic assays targeting tumour-specific messenger RNA, methylated DNA or microRNA. METHODS: We examined the feasibility of using whole-genome sequencing (WGS) data to design tumour-specific polymerase chain reaction (PCR)-based MRD tests (WGS-MRD) in 18 children with high-risk relapsed cancer, including ALL, high-risk neuroblastoma (HR-NB) and Ewing sarcoma (EWS) (n = 6 each). RESULTS: Sensitive WGS-MRD assays were generated for each patient and allowed quantitation of 1 tumour cell per 10-4 (0.01%)-10-5 (0.001%) mononuclear cells. In ALL, WGS-MRD and Ig/TCR-MRD were highly concordant. WGS-MRD assays also showed good concordance between quantitative PCR and droplet digital PCR formats. In serial clinical samples, WGS-MRD correlated with disease course. In solid tumours, WGS-MRD assays were more sensitive than RNA-MRD assays. CONCLUSIONS: WGS facilitated the development of patient-specific MRD tests in ALL, HR-NB and EWS with potential clinical utility in monitoring treatment response. WGS data could be used to design patient-specific MRD assays in a broad range of tumours.

Prognostic value of detection of CD99+ , CD45- cells in peripheral blood by flow cytometry in children with Ewing sarcoma.

BACKGROUND: Early detection of metastasis and recurrence of Ewing sarcoma (ES) is important for early management. This work aimed to detect CD99+ , CD45- cells in peripheral blood by flow cytometry (FC) before and during chemotherapy and evaluate their prognostic significance. PROCEDURE: This prospective cohort study was carried out on 60 children newly diagnosed with ES at Children Cancer Hospital-Egypt 57357 and 40 healthy children control group. Detection of CD99+ , CD45- cells in peripheral blood was accomplished by FC at baseline before treatment and after five cycles of chemotherapy. Samples were classified as positive if they had more than the upper limit of cells observed in the control cases. Correlation between FC results and relapse and overall survival (OS) after one year was performed. RESULTS: Median percentage of CD99+ , CD45- cells was significantly increased in patients compared with controls (0.002% vs 0%, respectively, P < 0.001). Post-cycle 5 CD99+ , CD45- cells were increased in 12 patients, of them 11 patients' disease had either relapsed or progressed. Post-cycle 5 CD99+ ; CD45- cells had a 73.3% sensitivity and 97.8% specificity for predicting relapse or progression, whereas baseline only had 6.7% sensitivity and 77.8% specificity. The hazard ratio for mortality in the post-cycle 5 positive group was 18.4 [95% confidence interval (1.86 to 181.46)] times that of the negative group. One year OS was 91.67%. CONCLUSION: Post-cycle 5 CD99+ , CD45- cells in peripheral blood by FC is a strong predictor for relapse, progression, and mortality whereas baseline is a poor predictor in newly diagnosed patients with ES.

Quantification of Translocation-Specific ctDNA Provides an Integrating Parameter for Early Assessment of Treatment Response and Risk Stratification in Ewing Sarcoma.

PURPOSE: We evaluated the predictive and prognostic value of circulating tumor DNA (ctDNA) in patients with Ewing sarcoma (EWS) treated in the EWING2008 trial. EXPERIMENTAL DESIGN: Plasma samples from 102 patients with EWS enrolled in the EWING2008 trial were obtained before and during induction chemotherapy. Genomic EWSR1 fusion sequence spanning primers and probes were used for highly specific and sensitive quantification of the levels of ctDNA by digital droplet PCR. ctDNA levels were correlated to established clinical risk factors and outcome parameters. RESULTS: Pretreatment ctDNA copy numbers were correlated with event-free and overall survival. The reduction in ctDNA levels below the detection limit was observed in most cases after only two blocks of vincristine, ifosfamide, doxorubicin, and etoposide (VIDE) induction chemotherapy. The persistence of ctDNA after two VIDE blocks was a strong predictor of poor outcomes. ctDNA levels correlated well with most established clinical risk factors; an inverse correlation was found only for the histologic response to induction therapy. ctDNA levels did not provide simple representations of tumor volume, but integrated information from various tumor characteristics represented an independent EWS tumor marker with predictive and prognostic value. CONCLUSIONS: ctDNA copy number in the plasma of patients with EWS is a quantifiable parameter for early risk stratification and can be used as a dynamic noninvasive biomarker for early prediction of treatment response and outcome of patients.

Multimodal analysis of cell-free DNA whole-genome sequencing for pediatric cancers with low mutational burden.

Sequencing of cell-free DNA in the blood of cancer patients (liquid biopsy) provides attractive opportunities for early diagnosis, assessment of treatment response, and minimally invasive disease monitoring. To unlock liquid biopsy analysis for pediatric tumors with few genetic aberrations, we introduce an integrated genetic/epigenetic analysis method and demonstrate its utility on 241 deep whole-genome sequencing profiles of 95 patients with Ewing sarcoma and 31 patients with other pediatric sarcomas. Our method achieves sensitive detection and classification of circulating tumor DNA in peripheral blood independent of any genetic alterations. Moreover, we benchmark different metrics for cell-free DNA fragmentation analysis, and we introduce the LIQUORICE algorithm for detecting circulating tumor DNA based on cancer-specific chromatin signatures. Finally, we combine several fragmentation-based metrics into an integrated machine learning classifier for liquid biopsy analysis that exploits widespread epigenetic deregulation and is tailored to cancers with low mutation rates. Clinical associations highlight the potential value of cfDNA fragmentation patterns as prognostic biomarkers in Ewing sarcoma. In summary, our study provides a comprehensive analysis of circulating tumor DNA beyond recurrent genetic aberrations, and it renders the benefits of liquid biopsy more readily accessible for childhood cancers.

Circulating Plasma Tumor DNA Is Superior to Plasma Tumor RNA Detection in Ewing Sarcoma Patients: ptDNA and ptRNA in Ewing Sarcoma.

The detection of tumor-specific nucleic acids from blood increasingly is being used as a method of liquid biopsy and minimal residual disease detection. However, achieving high sensitivity and high specificity remains a challenge. Here, we perform a direct comparison of two droplet digital PCR (ddPCR)-based detection methods, circulating plasma tumor RNA and circulating plasma tumor DNA (ptDNA), in blood samples from newly diagnosed Ewing sarcoma patients. First, we developed three specific ddPCR-based assays to detect EWS-FLI1 or EWS-ERG fusion transcripts, which naturally showed superior sensitivity to DNA detection on in vitro control samples. Next, we identified the patient-specific EWS-FLI1 or EWS-ERG breakpoint from five patient tumor samples and designed ddPCR-based, patient-specific ptDNA assays for each patient. These patient-specific assays show that although plasma tumor RNA can be detected in select newly diagnosed patients, positive results are low and statistically unreliable compared with ptDNA assays, which reproducibly detect robust positive results across most patients. Furthermore, the unique disease biology of Ewing sarcoma enabled us to show that most cell-free RNA is not tumor-derived, although cell-free-DNA burden is affected strongly by tumor-derived DNA burden. Here, we conclude that, even with optimized highly sensitive and specific assays, tumor DNA detection is superior to RNA detection in Ewing sarcoma patients.

Key Immune Checkpoint PD-1/PD-L1 Signaling Pathway Components in the Blood Serum from Patients with Bone Tumors.

The levels of sPD-1 and sPD-L1 were analyzed in blood serum of 132 patients (age 14-70 years) with primary bone tumors: osteosarcoma (N=39), chondrosarcoma (N=42), Ewing sarcoma (N=9), chordoma (N=12), giant-cell bone tumor (GCBT) (N=16), benign neoplasms (N=14) and in and practically healthy subjects (age 19-58 years; N=27). sPD-L1 levels in all studied bone neoplasms were significantly higher than in the control. Serum sPD-1 level in GCBT patients was significantly higher than in the control, benign neoplasms, chondrosarcoma, and chordoma patients, but did not differ from osteosarcoma group. sPD-1 concentration in Ewing sarcoma was significantly higher than in chordoma and chondrosarcoma, but did not differ from the control. sPD-1 level in chondrosarcoma patients was also lower than in osteosarcoma, Ewing sarcoma, and in the control. Both sPD-1 and sPD-L1 concentrations were not significantly associated with the type of affected bone, process localization, disease stage, tumor histological grade, patients' age and sex. These results suggest the possibility of using these biological markers for preliminary assessment of the character of the process in the bone.

Early versus delayed administration of granulocyte-colony stimulating factor following chemotherapy in pediatric patients with Ewing sarcoma.

BACKGROUND: The optimal timing of initiating granulocyte-colony stimulating factor following chemotherapy in pediatric patients has not been clearly defined. This study aimed to compare the administration of granulocyte-colony stimulating factor on day 1 versus day 3 postchemotherapy in pediatric patients with Ewing sarcoma. METHOD: A retrospective study of pediatric patients with Ewing sarcoma who received granulocyte-colony stimulating factor following chemotherapy between January 2016 and September 2018 at a comprehensive cancer center. The institution's chemotherapy protocol for Ewing sarcoma was modified in April 2017 to include granulocyte-colony stimulating factor initiation on day 3 instead of day 1 post-chemotherapy. Febrile neutropenia requiring hospitalization, duration of hospital stay, and chemotherapy delay were compared for patients before and after the protocol change. RESULTS: Over the study period, 250 cycles were evaluated with day 1 granulocyte-colony stimulating factor and 221 cycles with day 3 granulocyte-colony stimulating factor. There were no differences between the day 1 and day 3 groups in the number of cycles associated with Febrile neutropenia requiring hospitalization (34 vs. 19, p = 0.086), and the length of Febrile neutropenia-related hospitalization (mean 4 ± 2.1 vs. 4.6 ± 1.8, p = 0.123). However, delay in chemotherapy due to neutropenia was reported in significantly more cycles in the day 1 group, compared to the day 3 group (37 vs. 16, p = 0.01). CONCLUSIONS: Febrile neutropenia resulting in hospital admission and the length of hospital stay was not different between pediatric patients with Ewing sarcoma who received granulocyte-colony stimulating factor on day 1 or day 3 post-chemotherapy. Chemotherapy delay due to neutropenia was higher in patients who received granulocyte-colony stimulating factor on day 1. Larger studies are required to fully determine the impact of delayed initiation of granulocyte-colony stimulating factor.

Pro-gastrin-releasing peptide as a marker for the Ewing sarcoma family of tumors.

BACKGROUND: Pro-gastrin-releasing peptide (ProGRP) is an established tumor marker of small cell lung cancer. The purpose of this study was to determine if ProGRP could serve as a tumor marker for the Ewing sarcoma family of tumors (ESFTs). METHODS: Sixteen patients with ESFTs (mean age 32 years) were included in this study. As a control group, 42 patients with other tumor types that clinically or pathologically mimic ESFTs were also analyzed. Pre-treatment serum ProGRP and neuron-specific enolase (NSE) levels, the relationships between these levels, and tumor volume were investigated. In addition, serial changes in the serum or plasma ProGRP (6 patients) and NSE levels (5 patients) were measured over the course of treatment. RESULTS: Pre-treatment serum ProGRP levels were higher than the normal range in 8 of 16 patients; for these eight patients, ProGRP levels positively correlated with tumor volume (R = 0.99). In the control group, ProGRP levels were within the normal range, except for the two patients. Changes in ProGRP levels during treatment were consistent with tumor volume. Serum NSE levels were elevated in 14 of 16 patients with ESFTs and 8 of 42 patients with other tumor types. The range of NSE elevation was much smaller compared to that of ProGRP. Our data indicate that ProGRP is superior to NSE in terms of specificity. CONCLUSIONS: Serum ProGRP levels were elevated in half of the patients with ESFTs and reflected therapeutic response. ProGRP is a reliable tumor marker for the diagnosis of ESFTs and evaluation of treatment response.

Establishment of a Nomogram-Based Model for Predicting the Prognostic Value of Inflammatory Biomarkers and Preoperative D-Dimer Level in Spinal Ewing's Sarcoma Family Tumors: A Retrospective Study of 83 Patients.

BACKGROUND: Ewing's sarcoma family tumors (ESFTs) are the second most common malignancy in children and adolescents. The purpose of the present retrospective study was to evaluate the prognostic role of inflammatory biomarkers and preoperative D-dimer levels in patients with spinal ESFTs. METHODS: The neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, lymphocyte/monocyte ratio, albumin/globulin ratio, C-reactive protein/albumin ratio (CAR), preoperative D-dimer level, and clinical parameters were evaluated and analyzed. Univariate and multivariate analyses for disease-free survival (DFS) and overall survival (OS) were performed using the log-rank test and Cox regression analysis, respectively. The DFS and OS rates were calculated using the Kaplan-Meier method. Nomograms were established to predict DFS and OS quantitatively. RESULTS: The optimal cutoff values for D-dimer, neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, lymphocyte/monocyte ratio, CAR, and albumin/globulin ratio were 0.3, 3.2, 168, 2.2, 1.5, and 1.4, respectively. The patients were stratified into 2 groups according to the cutoff values. Multivariate analysis revealed that age, resection mode, and D-dimer level were favorable prognostic factors for DFS and OS (P < 0.05). Metastasis and CAR <1.5 were significantly associated with OS (P < 0.05). Nomograms with all significant factors were established to predict DFS and OS. CONCLUSIONS: Our results have indicated that the preoperative D-dimer level is an effective prognostic factor with discriminatory ability for DFS and OS, superior to other indicators. Also, CAR was favorable prognostic factor for OS. Nomograms of DFS and OS can be recommended as practical models to evaluate the prognosis for patients with spinal ESFTs.

Detection of circulating tumour DNA is associated with inferior outcomes in Ewing sarcoma and osteosarcoma: a report from the Children's Oncology Group.

BACKGROUND: New prognostic markers are needed to identify patients with Ewing sarcoma (EWS) and osteosarcoma unlikely to benefit from standard therapy. We describe the incidence and association with outcome of circulating tumour DNA (ctDNA) using next-generation sequencing (NGS) assays. METHODS: A NGS hybrid capture assay and an ultra-low-pass whole-genome sequencing assay were used to detect ctDNA in banked plasma from patients with EWS and osteosarcoma, respectively. Patients were coded as positive or negative for ctDNA and tested for association with clinical features and outcome. RESULTS: The analytic cohort included 94 patients with EWS (82% from initial diagnosis) and 72 patients with primary localised osteosarcoma (100% from initial diagnosis). ctDNA was detectable in 53% and 57% of newly diagnosed patients with EWS and osteosarcoma, respectively. Among patients with newly diagnosed localised EWS, detectable ctDNA was associated with inferior 3-year event-free survival (48.6% vs. 82.1%; p = 0.006) and overall survival (79.8% vs. 92.6%; p = 0.01). In both EWS and osteosarcoma, risk of event and death increased with ctDNA levels. CONCLUSIONS: NGS assays agnostic of primary tumour sequencing results detect ctDNA in half of the plasma samples from patients with newly diagnosed EWS and osteosarcoma. Detectable ctDNA is associated with inferior outcomes.

Ewing sarcoma.

Ewing sarcoma is the second most frequent bone tumour of childhood and adolescence that can also arise in soft tissue. Ewing sarcoma is a highly aggressive cancer, with a survival of 70-80% for patients with standard-risk and localized disease and ~30% for those with metastatic disease. Treatment comprises local surgery, radiotherapy and polychemotherapy, which are associated with acute and chronic adverse effects that may compromise quality of life in survivors. Histologically, Ewing sarcomas are composed of small round cells expressing high levels of CD99. Genetically, they are characterized by balanced chromosomal translocations in which a member of the FET gene family is fused with an ETS transcription factor, with the most common fusion being EWSR1-FLI1 (85% of cases). Ewing sarcoma breakpoint region 1 protein (EWSR1)-Friend leukaemia integration 1 transcription factor (FLI1) is a tumour-specific chimeric transcription factor (EWSR1-FLI1) with neomorphic effects that massively rewires the transcriptome. Additionally, EWSR1-FLI1 reprogrammes the epigenome by inducing de novo enhancers at GGAA microsatellites and by altering the state of gene regulatory elements, creating a unique epigenetic signature. Additional mutations at diagnosis are rare and mainly involve STAG2, TP53 and CDKN2A deletions. Emerging studies on the molecular mechanisms of Ewing sarcoma hold promise for improvements in early detection, disease monitoring, lower treatment-related toxicity, overall survival and quality of life.

Genomic EWSR1 Fusion Sequence as Highly Sensitive and Dynamic Plasma Tumor Marker in Ewing Sarcoma.

PURPOSE: The application of the tumor-specific genomic fusion sequence as noninvasive biomarker for therapy monitoring in Ewing sarcoma (EwS) has been evaluated. EXPERIMENTAL DESIGN: EwS xenograft mouse models were used to explore detectability in small plasma volumes and correlation of genomic EWSR1-FLI1 copy numbers with tumor burden. Furthermore, 234 blood samples from 20 EwS patients were analyzed before and during multimodal treatment. EWSR1 fusion sequence levels in patients' plasma were quantified using droplet digital PCR and compared with tumor volumes calculated from MRI or CT imaging studies. RESULTS: Kinetics of EWSR1 fusion sequence copy numbers in the plasma are correlated with changes of the tumor volume in patients with localized and metastatic disease. The majority of patients showed a fast reduction of cell-free tumor DNA (ctDNA) during initial chemotherapy. Recurrence of increasing ctDNA levels signalized relapse development. CONCLUSIONS: Genomic fusion sequences represent promising noninvasive biomarkers for improved therapy monitoring in EwS. Until now, response assessment is largely based on MRI and CT imaging, implying restrictions on closely repeated performance and limitations on the differentiation between vital tumor and reactive stromal tissue. Particularly in patients with prognostic unfavorable disseminated disease, ctDNA is a valuable addition for the assessment of therapy response. Clin Cancer Res; 22(17); 4356-65. ©2016 AACR.

Highly personalized detection of minimal Ewing sarcoma disease burden from plasma tumor DNA.

BACKGROUND: Even though virtually all patients with Ewing sarcoma achieve a radiographic complete response, up to 30% of patients who present with localized disease and up to 90% of those who present with metastases experience a metastatic disease recurrence, highlighting the inability to identify patients with residual disease at the end of therapy. Up to 95% of Ewing sarcomas carry a driving EWS-ETS translocation that has an intronic breakpoint that is specific to each tumor, and the authors developed a system to quantitatively detect the specific breakpoint DNA fragment in patient plasma. METHODS: The authors used a long-range multiplex polymerase chain reaction (PCR) technique to identify tumor-specific EWS-ETS breakpoints in Ewing sarcoma cell lines, patient-derived xenografts, and patient tumors, and this sequence was used to design tumor-specific primer sets to detect plasma tumor DNA (ptDNA) by droplet digital PCR in xenograft-bearing mice and patients. RESULTS: Tumor-specific breakpoint DNA fragments were detected in the plasma of xenograft-bearing mice, and the signal correlated with tumor burden during primary tumor growth, after surgical resection, and at the time of metastatic disease recurrence. Furthermore, the authors were able to detect the specific breakpoint in plasma DNA obtained from 3 patients with Ewing sarcoma and in 2 patients the authors were able to detect ptDNA when there was radiographically undetectable disease present. CONCLUSIONS: The use of droplet digital PCR to detect tumor-specific EWS-ETS fusion gene breakpoint ptDNA fragments can be developed into a highly personalized biomarker of disease recurrence that can be optimized in animal studies for ultimate use in patients. Cancer 2016;122:3015-3023. © 2016 American Cancer Society.

ProGRP is a possible tumor marker for patients with Ewing sarcoma.

We analyzed serum ProGRP levels in patients with Ewing sarcoma, and found that 5 out of 9 patients had elevated levels; the values range equally with those of patients with limited disease of small-cell lung carcinoma. Serum ProGRP levels in patients with bone and soft tissue malignancies other than Ewing sarcoma are not elevated. Immunohistochemical studies demonstrated that ProGRP-like immunoreactivities were detected in Ewing sarcoma tissues obtained from 2 patients with elevated serum ProGRP levels, suggesting that ProGRP is a product of tumor cells of Ewing sarcoma. These results indicate that serum ProGRP could serve as a specific tumor marker for Ewing sarcoma. Since ProGRP is a major hormonal product of tumor cells of small-cell lung carcinoma, a typical neuroendocrine carcinoma, it is reasonable to postulate that the present study provides an evidence for Ewing sarcoma to possess neuroendocrine differentiation.

Systemic levels of neuropeptide Y and dipeptidyl peptidase activity in patients with Ewing sarcoma--associations with tumor phenotype and survival.

BACKGROUND: Ewing sarcoma (ES) is driven by fusion of the Ewing sarcoma breakpoint region 1 gene (EWSR1) with an E26 transformation-specific (ETS) transcription factor (EWS-ETS), most often the Friend leukemia integration 1 transcription factor (FLI1). Neuropeptide Y (NPY) is an EWS-FLI1 transcriptional target; it is highly expressed in ES and exerts opposing effects, ranging from ES cell death to angiogenesis and cancer stem cell propagation. The functions of NPY are regulated by dipeptidyl peptidase IV (DPPIV), a hypoxia-inducible enzyme that cleaves the peptide and activates its growth-promoting actions. The objective of this study was to determine the clinically relevant functions of NPY by identifying the associations between patients' ES phenotype and their NPY concentrations and DPP activity. METHODS: NPY concentrations and DPP activity were measured in serum samples from 223 patients with localized ES and 9 patients with metastatic ES provided by the Children's Oncology Group. RESULTS: Serum NPY levels were elevated in ES patients compared with the levels in a healthy control group and an osteosarcoma patient population, and the elevated levels were independent of EWS-ETS translocation type. Significantly higher NPY concentrations were detected in patients with ES who had tumors of pelvic and bone origin. A similar trend was observed in patients with metastatic ES. There was no effect of NPY on survival in patients with localized ES. DPP activity in sera from patients with ES did not differ significantly from that in healthy controls and patients with osteosarcoma. However, high DPP levels were associated with improved survival. CONCLUSIONS: Systemic NPY levels are elevated in patients with ES, and these high levels are associated with unfavorable disease features. DPPIV in serum samples from patients with ES is derived from nontumor sources, and its high activity is correlated with improved survival.

Circulating miR-125b as a biomarker of Ewing's sarcoma in Chinese children.

Previous studies indicated that microRNA-125b (miR-125b) has an important role in the progression of Ewing's sarcoma (ES). The purpose of the current study was to examine expression changes of miR-125b in the serum of ES patients and evaluate if the expression level of miR-125b could serve as a new biomarker for ES. This study was performed on patients who underwent surgical resection at our hospital between 2005 and 2013 after an initial diagnosis of ES. We measured serum miR-125b levels in 63 patients with ES and 126 healthy control patients using a real-time quantitative reverse transcriptase-PCR (qRT-PCR) method. Expression levels of serum miR-125b were distinctly decreased in ES patients when compared with healthy controls (P < 0.001). ES cases that had a poor response to chemotherapy presented a significant down-regulation of miR-125b (P = 0.001). The ROC curve showed that the serum miR-125b could serve as a valuable biomarker for differentiating ES patients from healthy controls with an AUC of 0.879 (95%CI = 0.817-0.924; P < 0.001). At a cut-off value of 2.203 for miR-125b, the sensitivity was 72.8% and the specificity was 87.2% in discriminating ES from the controls. Our results indicate that serum miR- 125b may serve as a useful noninvasive biomarker for ES.

Gene expression profiling of peripheral blood cells: new insights into Ewing sarcoma biology and clinical applications.

Ewing sarcoma (ES) is a group of highly aggressive small round cell tumors of bone or soft tissue with high metastatic potential and low cure rate. ES tumors are associated with a rapid osteolysis and necrosis. The currently accepted clinical prognostic parameters do not accurately predict survival of high-risk patients. Moreover, neither the subtype of EWS-FLI1/ERG in the tumor, nor the detection of fusion transcripts in the peripheral blood (PB) samples, has prognostic value in ES patients. We evaluated the prevalence of circulating tumor cells (CTCs) in 34 adult ES patients. Since CTCs were confirmed in only small subset of patients, we further explored the expression profiles of PB leukocytes using a panel of genes associated with immune system status and increased tumor invasiveness. Moreover, we analyzed the alterations of the routine blood tests in the examined cohort of patients and correlated our findings with the clinical outcome. A uniform decrease in ZAP70 expression in PB cells among all ES patients, as compared to healthy individuals, was observed. Monocytosis and the abnormal expression of CDH2 and CDT2 genes in the PB cells significantly correlated with poor prognosis in ES patients. Our study supports the previously proposed hypothesis of systemic nature of ES. Based on the PB cell expression profiles, we propose a mechanism by which immune system may be involved in intensification of osteoclastogenesis and disease progression in ES patients. Moreover, we demonstrate the prognostic value of molecular PB testing at the time of routine histopathological diagnosis.

Common Ewing sarcoma-associated antigens fail to induce natural T cell responses in both patients and healthy individuals.

Disseminated or relapsed Ewing sarcoma (EwS) has remained fatal in the majority of patients. A promising approach to preventing relapse after conventional therapy is to establish tumor antigen-specific immune control. Efficient and specific T cell memory against the tumor depends on the expansion of rare T cells with native specificity against target antigens overexpressed by the tumor. Candidate antigens in EwS include six-transmembrane epithelial antigen of the prostate-1 (STEAP1), and the human cancer/testis antigens X-antigen family member 1 (XAGE1) and preferentially expressed antigen in melanoma (PRAME). Here, we screened normal donors and EwS patients for the presence of circulating T cells reactive with overlapping peptide libraries of these antigens by IFN-γ Elispot analysis. The majority of 22 healthy donors lacked detectable memory T cell responses against STEAP1, XAGE1 and PRAME. Moreover, ex vivo detection of T cells specific for these antigens in both blood and bone marrow were limited to a minority of EwS patients and required nonspecific T cell prestimulation. Cytotoxic T cells specific for the tumor-associated antigens were efficiently and reliably generated by in vitro priming using professional antigen-presenting cells and optimized cytokine stimulation; however, these T cells failed to interact with native antigen processed by target cells and with EwS cells expressing the antigen. We conclude that EwS-associated antigens fail to induce efficient T cell receptor (TCR)-mediated antitumor immune responses even under optimized conditions. Strategies based on TCR engineering could provide a more effective means to manipulating T cell immunity toward targeted elimination of tumor cells.