The interface between apoptosis (programmed cell death) and the cell cycle is essential to preserve homeostasis and genomic integrity. Here, we show that survivin, an inhibitor of apoptosis over-expressed in cancer, physically associates with the cyclindependent kinase p34 cdc2 on the mitotic apparatus, and is phosphorylated on Thr 34 by p34 cdc2 -cyclin B1, in vitro and in vivo. Loss of phosphorylation on Thr 34 resulted in dissociation of a survivincaspase-9 complex on the mitotic apparatus, and caspase-9-dependent apoptosis of cells traversing mitosis. These data identify survivin as a mitotic substrate of p34 cdc2 -cyclin B1 and suggest that survivin phosphorylation on Thr 34 may be required to preserve cell viability at cell division. Manipulation of this pathway may facilitate the elimination of cancer cells at mitosis.

A productive angiogenic response must couple to the survival machinery of endothelial cells to preserve the integrity of newly formed vessels. Angiopoietin-1 (Ang-1) is an endothelium-specific ligand essential for embryonic vascular stabilization, branching morphogenesis, and post-natal angiogenesis, but its contribution to endothelial cell survival has not been completely elucidated. Here we show that Ang-1 acting via the Tie 2 receptor induces phosphorylation of the survival serinethreonine kinase, Akt (or protein kinase B). This is associated with up-regulation of the apoptosis inhibitor, survivin, in endothelial cells and protection of endothelium from death-inducing stimuli. Moreover, dominant negative survivin negates the ability of Ang-1 to protect cells from undergoing apoptosis. The activation of antiapoptotic pathways mediated by Akt and survivin in endothelial cells may contribute to Ang-1 stabilization of vascular structures during angiogenesis, in vivo.During angiogenesis, endothelial cells receive cues from growth factors to initiate mitosis, migration, and organization of endothelial cells into primitive angiotubes and patent vascular networks (1, 2). These processes critically depend on preservation of endothelial cell viability. Disruption of endothelial cell-matrix contacts or interference with extracellular survival signals is sufficient to initiate caspase-dependent apoptosis in endothelium, culminating with rapid involution of vascular structures (3, 4). Unlike most angiogenic regulators, including fibroblast growth factor or vascular endothelial growth factor (VEGF), 1 angiopoietin-1 (Ang-1) does not stimulate endothelial cell growth but rather promotes stabilization of vascular networks and branching morphogenesis in vivo and in vitro (5-8). Little is known about the signaling requirements of these responses, and the mechanism(s) of Ang-1-induced cytoprotection are unknown (7, 9). The major goal of this paper was to elucidate a potential link between endothelial cell viability and maintenance of angiogenesis by examining the ability of Ang-1 to activate the antiapoptotic serine-threonine kinase, Akt (or protein kinase B). Moreover, we examined the relationship between Ang-1, Akt activation, and the expression of the anti-apoptotic genes, bcl-2 and survivin, in cultured microvascular endothelial cells (MVEC). MATERIALS AND METHODSCell Culture and Reagents-Bovine MVEC (Vec Technologies, Rensselaer, NY) were cultured in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum, L-glutamine, and antibiotics (penicillin and streptomycin). Cells (up to passage 12) were used for the experiments. In experiments examining endogenous survivin expression, human umbilical vein endothelial cells (HUVEC) were used, because the survivin antibody recognized human survivin better than bovine survivin. HUVEC were cultured on gelatin-coated tissue culture flasks in M199 medium containing 20% fetal bovine serum, 50 g/ml endothelial cell growth supplement (a commercial preparation that contains main...

Introduction Higher comorbidity and older age have been reported as correlates of poor outcomes in COVID‐19 patients worldwide; however, US data are scarce. We evaluated mortality predictors of COVID‐19 in a large cohort of hospitalized patients in the United States. Design Retrospective, multicenter cohort of inpatients diagnosed with COVID‐19 by RT‐PCR from 1 March to 17 April 2020 was performed, and outcome data evaluated from 1 March to 17 April 2020. Measures included demographics, comorbidities, clinical presentation, laboratory values and imaging on admission. Primary outcome was mortality. Secondary outcomes included length of stay, time to death and development of acute kidney injury in the first 48‐h. Results The 1305 patients were hospitalized during the evaluation period. Mean age was 61.0 ± 16.3, 53.8% were male and 66.1% African American. Mean BMI was 33.2 ± 8.8 kg m−2. Median Charlson Comorbidity Index (CCI) was 2 (1–4), and 72.6% of patients had at least one comorbidity, with hypertension (56.2%) and diabetes mellitus (30.1%) being the most prevalent. ACE‐I/ARB use and NSAIDs use were widely prevalent (43.3% and 35.7%, respectively). Mortality occurred in 200 (15.3%) of patients with median time of 10 (6–14) days. Age > 60 (aOR: 1.93, 95% CI: 1.26–2.94) and CCI > 3 (aOR: 2.71, 95% CI: 1.85–3.97) were independently associated with mortality by multivariate analyses. NSAIDs and ACE‐I/ARB use had no significant effects on renal failure in the first 48 h. Conclusion Advanced age and an increasing number of comorbidities are independent predictors of in‐hospital mortality for COVID‐19 patients. NSAIDs and ACE‐I/ARB use prior to admission is not associated with renal failure or increased mortality.

A checkpoint surveying the entry into mitosis responds to defects in spindle microtubule assembly/stability. This has been used to trigger apoptosis in cancer cells, but how the spindle checkpoint couples to the cell survival machinery has remained elusive. Here, we report that microtubule stabilization engenders a survival pathway that depends on elevated activity of p34(cdc2) kinase and increased expression of the apoptosis inhibitor and mitotic regulator, survivin. Pharmacologic, genetic, or molecular ablation of p34(cdc2) kinase after microtubule stabilization resulted in massive apoptosis independent of p53, suppression of tumor growth, and indefinite survival without toxicity in mice. By ablating this survival checkpoint, inhibitors of p34(cdc2) kinase could safely improve the efficacy of microtubule-stabilizing agents used to treat common cancers.