Design,Synthesis and Biological Evaluation of Novel Pyrazolo[1,2,4]triazolopyrimidine Derivatives as Potential Anticancer Agents

Three novel pyrazolo-[4,3-e][1,2,4]triazolopyrimidine derivatives (1, 2, and 3) were designed, synthesized, and evaluated for their in vitro biological activity. All three compounds exhibited different levels of cytotoxicity against cervical and breast cancer cell lines. However, compound 1 showed the best antiproliferative activity against all tested tumor cell lines, including HCC1937 and HeLa cells, which express high levels of wild-type epidermal growth factor receptor (EGFR). Western blot analyses demonstrated that compound 1 inhibited the activation of EGFR, protein kinase B (Akt), and extracellular signal-regulated kinase (Erk)1/2 in breast and cervical cancer cells at concentrations of 7 and 11 µM, respectively. The results from docking experiments with EGFR suggested the binding of compound 1 at the ATP binding site of EGFR. Furthermore, the crystal structure of compound 3 (7-(4-bromophenyl)-9-(pyridin-4-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine) was determined by single crystal X-ray analysis. Our work represents a promising starting point for the development of a new series of compounds targeting EGFR.     

Visualization of lipid-receptor interactions on single cells by time-resolved imaging fluorescence microscopy

The physical interaction between plasma-membrane lipids and the epidermal growth factor (EGF)-receptor was investigated on single A431 human epidermoid carcinoma cells by monitoring fluorescence resonance energy transfer (FRET) between exogeneously added fluorescein-EGF (donor) and 2-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine (Bodipy-PC, acceptor) using donor-photobleaching FRET-microscopy. The measured mean FRET-efficiency of 13% is indicative of such a physical interaction and exemplifies the great potential and sensitivity of time-resolved imaging fluorescence microscopy techniques for the study of lipid-receptor interactions on single cells.     

Modelling study of protein kinase inhibitors: Binding mode of staurosporine and origin of the selectivity of CGP 52411

Summary A model for the binding mode of the potent protein kinase inhibitor staurosporine is proposed. Using the information provided by the crystal structure of the cyclic-AMP-dependent protein kinase, it is suggested that staurosporine, despite a seemingly unrelated chemical structure, exploits the same key hydrogen-bond interactions as ATP, the cofactor of the protein kinases, in its binding mode. The structure-activity relationships of the inhibitor and a docking analysis give strong support to this protein tyrosine kinase is rationalized on the basis of the model. It is proposed that this selectivity originates in the occupancy, by one of the anilino moieties of the inhibitor, of the region of the enzyme cleft that normally binds the ribose ring of ATP, which appears to possess a marked lipophilic character in this kinase.