Regulation of reverse electron transfer at mitochondrial complex I by unconventional Notch action in cancer stem cells.

Metabolic flexibility is a hallmark of many cancers where mitochondrial respiration is critically involved, but the molecular underpinning of mitochondrial control of cancer metabolic reprogramming is poorly understood. Here, we show that reverse electron transfer (RET) through respiratory chain complex I (RC-I) is particularly active in brain cancer stem cells (CSCs). Although RET generates ROS, NAD+/NADH ratio turns out to be key in mediating RET effect on CSC proliferation, in part through the NAD+-dependent Sirtuin. Mechanistically, Notch acts in an unconventional manner to regulate RET by interacting with specific RC-I proteins containing electron-transporting Fe-S clusters and NAD(H)-binding sites. Genetic and pharmacological interference of Notch-mediated RET inhibited CSC growth in Drosophila brain tumor and mouse glioblastoma multiforme (GBM) models. Our results identify Notch as a regulator of RET and RET-induced NAD+/NADH balance, a critical mechanism of metabolic reprogramming and a metabolic vulnerability of cancer that may be exploited for therapeutic purposes.

Virtual Surgical Planning Decreases Operative Time for Isolated Single Suture and Multi-suture Craniosynostosis Repair.

BACKGROUND: Cranial vault reconstruction is a complex procedure due to the need for precise 3-dimensional outcomes. Traditionally, the process involves manual bending of calvarial bone and plates. With the advent of virtual surgical planning (VSP), this procedure can be streamlined. Despite the advantages documented in the literature, there have been no case-control studies comparing VSP to traditional open cranial vault reconstruction. METHODS: Data were retrospectively collected on patients who underwent craniosynostosis repair during a 7-year period. Information was collected on patient demographics, intraoperative and postoperative factors, and intraoperative surgical time. High-resolution computed tomography scans were used for preoperative planning with engineers when designing osteotomies, bone flaps, and final positioning guides. RESULTS: A total of 66 patients underwent open craniosynostosis reconstruction between 2010 and 2017. There were 35 control (non-VSP) and 28 VSP cases. No difference in age, gender ratios, or number of prior operations was found. Blood loss was similar between the 2 groups. The VSP group had more screws and an increased length of postoperative hospital stay. The length of the operation was shorter in the VSP group for single suture and for multiple suture operations. Operative time decreased as the attending surgeon increased familiarity with the technique. CONCLUSIONS: VSP is a valuable tool for craniosynostosis repair. We found VSP decreases surgical time and allows for improved preoperative planning. Although there have been studies on VSP, this is the first large case-control study to be performed on its use in cranial vault remodeling.

Incorporation of bone marrow-derived Flk-1-expressing CD34+ cells in the endothelium of tumor vessels in the mouse brain.

OBJECTIVE: Neoangiogenesis is a prerequisite for the full phenotypic expression and growth of a malignant tumor mass. It is believed to be triggered by tissue hypoxia and involves proliferation and sprouting of the preexisting vessels and the recruitment of endothelial progenitor cells from bone marrow. METHODS: A chimeric mouse model was used to examine the contribution of these progenitor cells to the neovasculature of brain tumor. T-cell knockout (RAG/KO5.2) mice were irradiated lethally, and their bone marrow was repopulated with T-cell depleted green fluorescent protein (GFP)-expressing bone marrow cells. RAG/RT-2 glioma cells were implanted into the striatum of the animals. Neovascular formation at various times of tumor growth was monitored together with the extent of incorporation of GFP+ bone marrow-derived cells within the vascular tree, in particular, cells carrying the endothelial progenitor markers CD34 and Flk-1. RESULTS: The recruitment of GFP+ cells to the growing tumor and their incorporation into the vascular network occurred during the period of increasing vascular density and preceded the expansion of the tumor. The number of marrow-derived cells with endothelial morphology and phenotype was small but significant (4% of all endothelial cells at Day 12); 54% of all tumor vessels contained at least one GFP+ cell. CONCLUSION: Our results suggest that bone marrow cells are recruited to newly formed and remodeled tumor vessels. Their recruitment may occur in response to signals from a highly proliferating milieu, and their role is to support the neovascular complex and to promote tumor growth.