Chloroquine activates the p53 pathway and induces apoptosis in human glioma cells

Glioblastoma is the most common malignant brain tumor in adults. The currently available treatments offer only a palliative survival advantage and the need for effective treatments remains an urgent priority. Activation of the p53 growth suppression/apoptotic pathway is one of the promising strategies in targeting glioma cells. We show that the quinoline derivative chloroquine activates the p53 pathway and suppresses growth of glioma cells in vitro and in vivo in an orthotopic (U87MG) human glioblastoma mouse model. Induction of apoptosis is one of the mechanisms underlying the effects of chloroquine on suppressing glioma cell growth and viability. siRNA-mediated downregulation of p53 in wild-type but not mutant p53 glioblastoma cells substantially impaired chloroquine-induced apoptosis. In addition to its p53-activating effects, chloroquine may also inhibit glioma cell growth via p53-independent mechanisms. Our results clarify the mechanistic basis underlying the antineoplastic effect of chloroquine and reveal its therapeutic potential as an adjunct to glioma chemotherapy

Revisiting adult neurogenesis and the role of erythropoietin for neuronal and oligodendroglial differentiation in the hippocampus

Recombinant human erythropoietin (EPO) improves cognitive performance in neuropsychiatric diseases ranging from schizophrenia and multiple sclerosis to major depression and bipolar disease. This consistent EPO effect on cognition is independent of its role in hematopoiesis. The cellular mechanisms of action in brain, however, have remained unclear. Here we studied healthy young mice and observed that 3-week EPO administration was associated with an increased number of pyramidal neurons and oligodendrocytes in the hippocampus of similar to 20%. Under constant cognitive challenge, neuron numbers remained elevated until >6 months of age. Surprisingly, this increase occurred in absence of altered cell proliferation or apoptosis. After feeding a $^{15}$N-leucine diet, we used nanoscopic secondary ion mass spectrometry, and found that in EPO-treated mice, an equivalent number of neurons was defined by elevated $^{15}$N-leucine incorporation. In EPO-treated NG2-Cre-ERT2 mice, we confirmed enhanced differentiation of preexisting oligodendrocyte precursors in the absence of elevated DNA synthesis. A corresponding analysis of the neuronal lineage awaits the identification of suitable neuronal markers. In cultured neurospheres, EPO reduced Sox9 and stimulated miR124, associated with advanced neuronal differentiation. We are discussing a resulting working model in which EPO drives the differentiation of non-dividing precursors in both (NG2+) oligodendroglial and neuronal lineages. As endogenous EPO expression is induced by brain injury, such a mechanism of adult neurogenesis may be relevant for central nervous system regeneration