Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease, characterized by motor neuron (MN) death, for which there are no truly effective treatments. Here, we describe a new small molecule survival screen carried out using MNs from both wild-type and mutant SOD1 mouse embryonic stem cells. Among the hits we found, kenpaullone had a particularly impressive ability to prolong the healthy survival of both types of MNs that can be attributed to its dual inhibition of GSK-3 and HGK kinases. Furthermore, kenpaullone also strongly improved the survival of human MNs derived from ALS-patient-induced pluripotent stem cells and was more active than either of two compounds, olesoxime and dexpramipexole, that recently failed in ALS clinical trials. Our studies demonstrate the value of a stem cell approach to drug discovery and point to a new paradigm for identification and preclinical testing of future ALS therapeutics.

Kruppel-like factor 4 (KLF4) is highly expressed in more than 70% of breast cancers and functions as an oncogene. However, an exact mechanism by which KLF4 enhances tumorigenesis of breast cancer remains unknown. In this study, we show that KLF4 was highly expressed in cancer stem cell (CSC)-enriched populations in mouse primary mammary tumor and breast cancer cell lines. Knockdown of KLF4 in breast cancer cells (MCF-7 and MDA-MB-231) decreased the proportion of stem/progenitor cells as demonstrated by expression of stem cell surface markers such as aldehyde dehydrogenase 1, side population and by in vitro mammosphere assay. Consistently KLF4 overexpression led to an increase of the cancer stem cell population. KLF4 knockdown also suppressed cell migration and invasion in MCF-7 and MDA-MB-231 cells. Furthermore, knockdown of KLF4 reduced colony formation in vitro and inhibited tumorigenesis in immunocompromised non-obese diabetic/severe combined immunodeficiency mice, supporting an oncogenic role for KLF4 in breast cancer development. Further mechanistic studies revealed that the Notch signaling pathway was required for KLF4-mediated cell migration and invasion, but not for CSC maintenance. Taken together, our study provides evidence that KLF4 has a potent oncogenic role in mammary tumorigenesis likely by maintaining stem cell-like features and by promoting cell migration and invasion. Thus, targeting KLF4 may provide an effective therapeutic approach to suppress tumorigenicity in breast cancer.

Human neural progenitor cells provide a source for cell replacement therapy to treat neurodegenerative diseases. Therefore, there is great interest in mechanisms and tools to direct the fate of multipotent progenitor cells during their differentiation to increase the yield of a desired cell type. We tested small molecule inhibitors of glycogen synthase kinase-3 (GSK-3) for their functionality and their influence on neurogenesis using the human neural progenitor cell line ReNcell VM. Here we report the enhancement of neurogenesis of human neural progenitor cells by treatment with GSK-3 inhibitors. We tested different small molecule inhibitors of GSK-3 i.e. LiCl, sodium-valproate, kenpaullone, indirubin-3-monoxime and SB-216763 for their ability to inhibit GSK-3 in human neural progenitor cells. The highest in situ GSK-3 inhibitory effect of the drugs was found for kenpaullone and SB-216763. Accordingly, kenpaullone and SB-216763 were the only drugs tested in this study to stimulate the Wnt/β-catenin pathway that is antagonized by GSK-3. Analysis of human neural progenitor differentiation revealed an augmentation of neurogenesis by SB-216763 and kenpaullone, without changing cell cycle exit or cell survival. Small molecule inhibitors of GSK-3 enhance neurogenesis of human neural progenitor cells and may be used to direct the differentiation of neural stem and progenitor cells in therapeutic applications.