Reducing sedated lumbar punctures in pediatric patients with acute lymphoblastic leukemia.

BACKGROUND: Sedation for lumbar punctures (LPs) in pediatric acute lymphoblastic leukemia (ALL) patients has been the standard for decades to reduce pain and anxiety. Recent studies on the potential long-term neurocognitive effects of cumulative propofol exposure have raised concerns about this practice. The recent pandemic introduced additional burdens to patients, with the requirement of a negative COVID-19 test prior to each sedated procedure. PROCEDURE: These factors prompted a quality improvement intervention at our institution where we aimed to reduce postinduction sedated LPs by 50%. Our intervention included patient and family education, followed by a simulation of the procedure for selected patients. Those converted to unsedated LPs were queried for their preference. Comparative cost, clinical time, and LP success rates were collected for sedated and unsedated LPs. RESULTS: Following the intervention, the percentage of LPs performed with sedation dropped from 100% to 48%. All LPs were successful using both techniques. Most patients who experienced the unsedated LP technique, and their guardians, strongly preferred this approach. Unsedated LPs significantly reduced clinical time (169 vs. 83 minutes) for families, decreased expenditures ($5736 reduction per procedure), and improved institutional opportunity cost due to a decrease in last-minute cancelations. CONCLUSION: We have shown that it is feasible to significantly reduce the use of sedation for LPs in patients with ALL, which has the potential to improve health and patient experience at a lower cost.

The translational repressor 4E-BP1 regulates RRM2 levels and functions as a tumor suppressor in Ewing sarcoma tumors.

Ribonucleotide reductase (RNR), which is a heterodimeric tetramer composed of RRM1 and RRM2 subunits, is the rate-limiting enzyme in the synthesis of deoxyribonucleoside triphosphates (dNTPs) and essential for both DNA replication and the repair of DNA damage. The activity of RNR is coordinated with the cell cycle and regulated by fluctuations in the level of the RRM2 subunit. Multiple cancer types, including Ewing sarcoma tumors, are sensitive to inhibitors of RNR or a reduction in the levels of either the RRM1 or RRM2 subunits of RNR. Here, we show that the expression of the RRM2 protein is dependent on active protein synthesis and that 4E-BP1, a repressor of cap-dependent protein translation, specifically regulates the level of the RRM2 protein. Furthermore, inhibition of mTORC1/2, but not mTORC1, activates 4E-BP1, inhibits protein synthesis, and reduces the level of the RRM2 protein in multiple sarcoma cell lines. This effect of mTORC1/2 inhibitors on protein synthesis and RRM2 levels was rescued in cell lines with the CRISPR/Cas9-mediated knockout of 4E-BP1. In addition, the inducible expression of a mutant 4E-BP1 protein that cannot be phosphorylated by mTOR blocked protein synthesis and inhibited the growth of Ewing sarcoma cells in vitro and in vivo in a xenograft. Overall, these results provide insight into the multifaceted regulation of RRM2 protein levels and identify a regulatory link between protein translation and DNA replication.

Eltrombopag inhibits the proliferation of Ewing sarcoma cells via iron chelation and impaired DNA replication.

BACKGROUND: The treatment of Ewing sarcoma, an aggressive bone and soft tissue sarcoma, is associated with suboptimal outcomes and significant side-effects. Consequently, there is an urgent need to identify novel therapies that will improve outcomes for children and adults with Ewing sarcoma tumors while also decreasing treatment-related toxicities. METHODS: We analyzed data from the PRISM drug repurposing screen, which tested the activity of 4518 drugs across 578 cancer cell lines, to identify drugs that selectively inhibit the growth of Ewing sarcoma cell lines. We then tested the effects of a top hit from the screen on cell proliferation, cell cycle progression, and activation of the DNA damage pathway using Ewing sarcoma cell lines. We also used a CRISPR/Cas9 gene knockout approach to investigate the role of Schlafen 11 (SLFN11), a restriction factor for DNA replication stress that is overexpressed in Ewing sarcoma tumors, in mediating the sensitivity of Ewing sarcoma cells to the drug. RESULTS: We found that eltrombopag, an FDA-approved thrombopoietin-receptor agonist (TPO-RA) that is currently being evaluated as a treatment for chemotherapy-induced thrombocytopenia, inhibits the growth of Ewing sarcoma cell lines in vitro in proliferation and colony formation assays. However, from a mechanistic standpoint, the thrombopoietin receptor is not expressed in Ewing sarcoma cells and we show that eltrombopag impairs DNA replication and causes DNA damage in Ewing sarcoma cells by chelating iron, a known "off-target" effect of the drug. We also found that the sensitivity of Ewing sarcoma cells to eltrombopag is mediated, in part, by SLFN11, which regulates the cellular response to DNA replication stress. CONCLUSIONS: Ewing sarcoma cell lines are sensitive to eltrombopag and this drug could improve outcomes for patients with Ewing sarcoma tumors by both targeting the tumor, via chelation of iron and inhibition of DNA replication, and reducing chemotherapy-induced thrombocytopenia, via stimulation of the thrombopoietin receptor.