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

Abstract

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.

Prognostic profiling of the immune cell microenvironment in Ewing´s Sarcoma Family of Tumors

“…42 Tumor-associated macrophages are known to promote cancer cell proliferation, immunosuppression and angiogenesis supporting metastasis and progression and through differentiation to M2 type macrophages expressing anti-inflammatory cytokines (IL-10, TGFβ) that have an inhibitory effect on cytotoxic CD8 + T cells. 43 Interestingly, in the peripheral blood monocytosis and other changes in blood parameters are more commonly observed in ESFT patients with a poor prognosis, 44 a phenomenon that supports the systemic changes of immune cells and cytokines in ESFT patients. Our findings may encourage efforts to target macrophages in ESFT, as currently tested for other types of malignancies using macrophage ablation or restoring their immunostimulatory potential.…”

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

“…Several studies have focused on the identification of micrometastases and CTCs in PB or bone marrow through the detection of EWSR1/FLI1 or EWSR1/ERG fusion transcripts ( Table 3 ). 8 , 22 – 30 In his study, Dubois describes a novel method of detecting CTCs in patients with ES using flow cytometry with antibodies against CD99 and CD45 to provide an alternative strategy to detect circulating ES tumor cells.…”

“…This information is mandatory for the identification of therapeutic targets and resistance mechanisms in CTCs, as well as for the stratification of patients and real-time monitoring of systemic therapies. 22 – 30 , 34 …”

Release of circulating tumor cells and cell-free nucleic acids is an infrequent event in synovial sarcoma: liquid biopsy analysis of 15 patients diagnosed with synovial sarcoma

“…In contrast to carcinomas, few studies have investigated the identification of CTCs in sarcomas [ 14 ]. Among mesenchymal tumors, CTCs have been for the most part well-studied in Ewing’s sarcoma/peripheral neuroectodermal tumor (EWS/PNET) [ 15 – 18 ]. Regarding CTCs in SS, less data is available where investigators have identified the fusion gene product from the peripheral blood of affected patients.…”