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Protein-kinase inhibitors are among the most advanced compounds in development using the new drug discovery paradigm of developing smallmolecule drugs against specific molecular targets in cancer. After treatment with a cyclin dependent kinase CDK2 inhibitor in monkey, histopathological analysis of the eye showed specific cellular damage in the photoreceptor layer. Since this CDK2 inhibitor showed activity also on other CDKs, in order to investigate the mechanism of toxicity of this compound, we isolated cones and rods from the retina of normal monkey and humans by Laser Capture Microdissection. Using Real-Time PCR we first measured the expression of cyclin dependent protein-kinases (CDK)1, 2, 4, 5, Glycogen synthase kinase 3β (GSK3β) and microtubule associated protein TAU. We additionally verified the presence of these proteins in monkey eye sections by immuno-histochemistry and immunofluorescence analysis and afterwards quantified GSK3β, phospho-GSK3β and TAU by Reverse Phase Protein Microarrays. With this work we demonstrate how complementary gene expression and protein-based technologies constitute a powerful tool for the understanding of the molecular mechanism of a CDK2 inhibitor induced toxicity. Moreover, this investigative approach is helpful to better understand and characterize the mechanism of species-specific toxicities and further support a rational, molecular mechanism-based safety assessment in humans.

The effects of Vaccinium myrtillue anthocyanosides, substances which demonstrated significant effect on the formation of new capillaries in experimental animals, and of dexamethasone were evaluated on cell cultures derived from umbilical vein. According to Shearn et al, pure endothelial cell suspensions were grown as primary and passed cell cultures. In the same way suspensions of highly contaminated specimens containing both ri broblasts and smooth muscle cells together with endothelial cells were cultured. Both types of culture were exposed to different concentrations of the two stimulants. In pure endothelial cell cultures, dexamethasone enhanced cell spreading as well as protein content. Anthocyanosides demonstrated a positive effect on cell proliferation and protein content. In different cell type cultures, dexamethasone stimulated the proliferation of endothelium more actively than other cells, while anthocyanoside s showed a stimulating activity on all different cellular types.

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