Glioblastoma is the most prevalent and aggressive type of brain tumor, with less than one year survival after diagnosis. Current glioma cell models are inadequate, which limits drug-discovery efforts. Recently, novel adherent glioma neural stem (GNS) cells preserving features of the original tumors have been derived by scientists at the Wellcome Trust Centre for Stem Cell Research at the University of Cambridge.
“GNS cells are the gold standard for screening,” explained Davide Danovi, M.D., Ph.D. He has taken forward this work developing a live image-based chemical-screening platform to follow in real time, through pictures, the response of GNS cells to drugs. A library containing 450 known drugs was screened for proof of principle and a cluster of compounds showed cytotoxic effect, with two compounds showing specificity to GNS.
Now further improvements to the stringency of the assay allow identification of drugs presenting with a cytostatic—not just a cytotoxic—effect on the GNS cells. Compounds specifically affecting GNS cells (including compounds promoting arrest or differentiation) are promising therapeutic leads for glioblastoma.
There has been a great deal of interest in iPSCs recently. Chickfumi Yokoyama, Ph.D., CEO of ReproCell, described the use of iPSCs for cardiotoxicity screening. His company has a strong collaboration with Norio Nakatsuji’s lab at Kyoto University.
Cardiotoxicity is a significant cause of pre- and postapproval failure, and the current hERG assay is limited. ReproCell’s new QTempo assay may help overcome some of these limitations. It uses beating human cardiomyocytes and focuses upon multi-ion channel analysis. This assay is able to detect changes in the beating rate of cardiomyocytes on exposure to drug compounds, according to Dr. Yokoyama. QTempo is also being compared with hERG and in vivo testing. In other developments, ReproCell has used Cellartis’ hESCs and monkey embryonic stem cells to assess the electrophysiological impact of known compounds.
ReproCell is also working on neural stem cells and has obtained Alzheimer disease-specific neurons by differentiation of hESCs.
Finally, suppliers are gearing up to meet the stem cell challenge. Rick Ryan, Ph.D., vp of drug discovery and development and leader of the stem cell initiative at Millipore, spoke about how his company is addressing the needs for routine use of stem cells in drug discovery. To this end, Millipore is integrating the capabilities of its research and bioprocessing divisions. This way it will be able to focus upon validating the use of stem cells for targeted drug discovery applications and also scaling up production.
“We believe there is a basic need for industrializing this solution,” Dr. Ryan said. He listed the areas where more work is needed: cGMP media and growth factors, bioreactors, cell characterization, and purification technologies. Bioprocessing needs include reproducibility, validated scale-up, and cGMP compliance. Millipore is already looking at an integrated cell-processing solution, he said. This includes research on microcarriers and harvesting enzymes for 3-D cell culture in bioreactors, as well as process monitoring and downstream processing for large-scale manufacturing of stem cells.
According to Dr. Ryan, the Millipore stem cell portfolio currently includes human mesenchymal, neural, and embryonic stem cells; mouse embryonic stem cells; and technologies for reprogramming somatic cells into iPSCs. Dr. Ryan also noted that primary hepatocytes used currently in toxicity testing have significant limitations. Millipore is seeking to address these issues through a combination of stem cell biology and production capability.