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Ewing's sarcoma family of tumors (ESFT) refers to aggressive malignancies which frequently harbor characteristic EWS-FLI1 or EWS-ERG genomic fusions. Here, we report that these fusion products interact with the DNA damage response protein and transcriptional coregulator PARP-1. ESFT cells, primary tumor xenografts, and tumor metastases were all highly sensitive to PARP1 inhibition. Addition of a PARP1 inhibitor to the second-line chemotherapeutic agent temozolamide resulted in complete responses of all treated tumors in an EWS-FLI1–driven mouse xenograft model of ESFT. Mechanistic investigations revealed that DNA damage induced by expression of EWS-FLI1 or EWS-ERG fusion genes was potentiated by PARP1 inhibition in ESFT cell lines. Notably, EWS-FLI1 fusion genes acted in a positive feedback loop to maintain the expression of PARP1, which was required for EWS-FLI–mediated transcription, thereby enforcing oncogene-dependent sensitivity to PARP-1 inhibition. Together, our findings offer a strong preclinical rationale to target the EWS-FLI1:PARP1 intersection as a therapeutic strategy to improve the treatment of ESFTs. Cancer Res; 72(7); 1608–13. ©2012 AACR.

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Ewing's sarcoma family of tumors (ESFT) refers to aggressive malignancies which frequently harbor characteristic EWS-FLI1 or EWS-ERG genomic fusions. Here, we report that these fusion products interact with the DNA damage response protein and transcriptional coregulator PARP-1. ESFT cells, primary tumor xenografts, and tumor metastases were all highly sensitive to PARP1 inhibition. Addition of a PARP1 inhibitor to the second-line chemotherapeutic agent temozolamide resulted in complete responses of all treated tumors in an EWS-FLI1–driven mouse xenograft model of ESFT. Mechanistic investigations revealed that DNA damage induced by expression of EWS-FLI1 or EWS-ERG fusion genes was potentiated by PARP1 inhibition in ESFT cell lines. Notably, EWS-FLI1 fusion genes acted in a positive feedback loop to maintain the expression of PARP1, which was required for EWS-FLI–mediated transcription, thereby enforcing oncogene-dependent sensitivity to PARP-1 inhibition. Together, our findings offer a strong preclinical rationale to target the EWS-FLI1:PARP1 intersection as a therapeutic strategy to improve the treatment of ESFTs. Cancer Res; 72(7); 1608–13. ©2012 AACR.

Objective To identify characteristics of pediatric sickle cell disease (SCD) hospitalizations and to examine admission demographics and medical expenditures. Methods Admissions with SCD were identified from the 2009 and 2012 releases of the Healthcare and Cost Utilization Project's Kids Inpatient Database. Disease-specific secondary diagnoses including acute chest syndrome (ACS), vaso-occlusive pain crisis (VOC), splenic sequestration, and stroke/transient ischemic attack were analyzed for patient and hospital demographics. Analytical endpoints included total healthcare expenditures and mortality. Results We reviewed 75,234 inpatient hospitalizations with a diagnosis of SCD. Over $900,000,000 was spent annually in associated healthcare expenditure. The median length of hospitalization stay (LOS) for all admissions was 3 days (interquartile range [IQR] 2–5 days). VOC was the most frequent secondary diagnosis, recording 48,698 total hospitalizations and a median LOS of 3 days (IQR 2–6 days). Of the 8,490 hospitalizations with ACS, the infant population had a significantly higher mortality rate compared to other age groups (2% vs. 0.3%, P < 0.001). Cerebral vascular accidents incurred the second highest median hospitalization cost ($18,956), behind ACS ($22,631). A high proportion of Caucasian patients died during hospitalization for VOC (0.4% vs. 0.1%, P = 0.014) and ACS (4% vs. 0.2%, P < 0.001) when compared to non-Caucasians. Conclusion Inpatient hospitalizations for secondary manifestations of pediatric SCD were associated with significant healthcare expenditures. Patients with an increased statistical risk for death during hospitalization included Caucasians with SCD complications of ACS and VOC, and patients

The Ewing's sarcoma family of tumors (ESFTs) are aggressive malignancies which frequently harbor EWS-FLI1 or EWS-ERG genomic fusions. Here, we demonstrate that these fusion products interact with, and depend on, poly (ADP-ribose) polymerase 1 (PARP1), a DNA damage response protein and transcriptional co-regulator. This interaction occurs in a DNA-independent manner. ESFT cell lines and xenografts are preferentially sensitive to PARP1 inhibition, and the addition of a PARP1 inhibitor to the second-line chemotherapeutic agent temozolamide resulted in complete response of all treated tumors in an EWS-FLI1 ESFT xenograft model. PARP inhibition blocked Ewing's cell line, but not control osteosarcoma or rhabdomyosarcoma cell line invasion, as well as the formation of lung metastasis in a xenograft model of ESFT. Mechanistically, the EWS-FLI1 and EWS-ERG fusions induce DNA damage, which is potentiated by PARP1 inhibition in ESFT cell lines. In a positive feedback loop, EWS-FLI1 fusions maintain the expression of PARP1 by direct regulation of the PARP1 promoter. This regulation is independently supported by a gene expression array data set of 20 ESFT patient tumors (Spearman r = 0.8165). Finally, because front-line therapy for this disease includes an intense regimen of five cytotoxic chemotherapy agents from which patients can quickly relapse with even more aggressive disease, we studied the effect of PARP inhibition in two Ewing's sarcoma cell line models derived after patient relapse. Importantly, these two cell lines maintained a preferential sensitivity to PARP1 inhibition despite their general chemoresistance. These findings suggest that targeting the EWS-FLI1: PARP1 interaction axis is a promising therapeutic strategy for the Ewing's sarcoma family of tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4681. doi:1538-7445.AM2012-4681