Oncogenic N-Ras Mitigates Oxidative Stress-Induced Apoptosis of Hematopoietic Stem Cells.

Leukemic relapse is believed to be driven by transformed hematopoietic stem cells (HSC) that harbor oncogenic mutations or have lost tumor suppressor function. Recent comprehensive sequencing studies have shown that mutations predicted to activate Ras signaling are highly prevalent in hematologic malignancies and, notably, in refractory and relapsed cases. To better understand what drives this clinical phenomenon, we expressed oncogenic NrasG12D within the hematopoietic system in mice and interrogated its effects on HSC survival. N-RasG12D conferred a survival benefit to HSCs and progenitors following metabolic and genotoxic stress. This effect was limited to HSCs and early progenitors and was independent of autophagy and cell proliferation. N-RasG12D-mediated HSC survival was not affected by inhibition of canonical Ras effectors such as MEK and PI3K. However, inhibition of the noncanonical Ras effector pathway protein kinase C (PKC) ameliorated the protective effects of N-RasG12D. Mechanistically, N-RasG12D lowered levels of reactive oxygen species (ROS), which correlated with reduced mitochondrial membrane potential and ATP levels. Inhibition of PKC restored the levels of ROS to that of control HSCs and abrogated the protective effects granted by N-RasG12D. Thus, N-RasG12D activation within HSCs promotes cell survival through the mitigation of ROS, and targeting this mechanism may represent a viable strategy to induce apoptosis during malignant transformation of HSCs. SIGNIFICANCE: Targeting oncogenic N-Ras-mediated reduction of ROS in hematopoietic stem cells through inhibition of the noncanonical Ras effector PKC may serve as a novel strategy for treatment of leukemia and other Ras-mutated cancers.

Fetal intervention for congenital chylothorax is associated with improved outcomes in early life.

BACKGROUND: Congenital chylothorax (CC) can have devastating consequences for neonates. We sought to determine the outcomes of cases treated at our institution and evaluate the role of fetal intervention. MATERIALS AND METHODS: With Institutional Review Board approval, patients treated at our institution 09/2006-04/2016 with CC were reviewed. History and outcomes were compared between patients undergoing fetal intervention (fetal group) and patients who did not (control group). RESULTS: Twenty-three patients were identified. Mean gestational age at birth was 35 wk. Overall mortality was 30% (7 patients). Nineteen patients (83%) were prenatally diagnosed, and 10 patients (43%) underwent fetal intervention. Birth weight was significantly lower in the fetal group compared to the control group (median interquartile range [IQR]; 2.5 [2.3-3.0] versus 3.3 [2.6-3.7] kg, P = 0.02). Apgar scores were significantly higher in the fetal group than the control group at 1 and 5 min (median [IQR]; 6 [4-8] versus 1 [1-2], P = 0.005 and 8 [7-9] versus 2 [2-6], P = 0.008, respectively). For those patients with prenatal diagnosis of CC and hydrops fetalis, thrombosis and lymphopenia were both improved in the fetal group (thrombosis 0% versus 40%, P = 0.03; lymphocyte nadir [median {IQR}] 1.5 [0.6-2.9] versus 0.1 [0.05-0.2], P = 0.02). Duration of support with mechanical ventilation was significantly shorter in the fetal group (median [IQR]; 1 [0-40] versus 41 [29-75] d, P = 0.04). CONCLUSIONS: Fetal intervention for CC is associated with improved Apgar scores and decreased ventilator days and complications in patients with hydrops fetalis. Fetuses with chylothorax, especially those with hydrops, should be referred to a fetal center for evaluation.