Effects of wortmannin on glucose uptake and protein kinase C activity in rat adipocytes

Development of PI3K inhibitors: Advances in clinical trials and new strategies (Review)

Phosphatidylinositol 3-kinases (PI3Ks) are the family of vital lipid kinases widely distributed in mammalian cells. The overexpression of PI3Ks leads to hyperactivation of the PI3K/AKT/mTOR pathway, which is considered a pivotal pathway in the occurrence and development of tumors. Hence, PI3Ks are viewed as promising therapeutic targets for anti-cancer therapy. To date, some PI3K inhibitors have achieved desired therapeutic effect via inhibiting the activity of PI3Ks or reducing the level of PI3Ks in clinical trials, among which, Idelalisib, Alpelisib and Duvelisib have been approved by the FDA for treatment of ER⁺/HER2^- advanced metastatic breast cancer and refractory chronic lymphocytic leukemia (CLL) and small lymphocytic lymphomas (SLL). This review focuses on the latest advances of PI3K inhibitors with efficacious anticancer activity, which are classified into Pan-PI3K inhibitors, isoform-specific PI3K inhibitors and dual PI3K/mTOR inhibitors based on the isoform affinity. Their corresponding structure characteristics and structures-activity relationship (SAR), together with the progress in the clinical application are mainly discussed. Additionally, the new PI3K inhibitory strategy, such as PI3K degradation agent, for the design of potential PI3K candidates to overcome drug resistance is referred as well.

A Probabilistic Boolean Network Approach for the Analysis of Cancer-Specific Signalling: A Case Study of Deregulated PDGF Signalling in GIST

BACKGROUND

Signal transduction networks are increasingly studied with mathematical modelling approaches while each of them is suited for a particular problem. For the contextualisation and analysis of signalling networks with steady-state protein data, we identified probabilistic Boolean network (PBN) as a promising framework which could capture quantitative changes of molecular changes at steady-state with a minimal parameterisation.

RESULTS AND CONCLUSION

In our case study, we successfully applied the PBN approach to model and analyse the deregulated Platelet-Derived Growth Factor (PDGF) signalling pathway in Gastrointestinal Stromal Tumour (GIST). We experimentally determined a rich and accurate dataset of steady-state profiles of selected downstream kinases of PDGF-receptor-alpha mutants in combination with inhibitor treatments. Applying the tool optPBN, we fitted a literature-derived candidate network model to the training dataset consisting of single perturbation conditions. Model analysis suggested several important crosstalk interactions. The validity of these predictions was further investigated experimentally pointing to relevant ongoing crosstalk from PI3K to MAPK signalling in tumour cells. The refined model was evaluated with a validation dataset comprising multiple perturbation conditions. The model thereby showed excellent performance allowing to quantitatively predict the combinatorial responses from the individual treatment results in this cancer setting. The established optPBN pipeline is also widely applicable to gain a better understanding of other signalling networks at steady-state in a context-specific fashion.

Phosphatidylinositol 3-kinase and focal adhesion kinase are early signals in the growth factor-like responses to thrombospondin-1 seen in human vascular smooth muscle

Thrombospondin-1 (TSP-1) is a matricellular protein that is expressed in negligible amounts in normal blood vessels but is markedly upregulated in vascular injury. Although TSP-1 can act as a pleiotropic regulator for human vascular smooth muscle cells (HVSMCs), the intracellular signaling pathways stimulated by this protein remain obscure. In cultured HVSMCs derived from saphenous vein, TSP-1 induces tyrosine phosphorylation of a number of cellular proteins, with a complex temporal pattern of activation. Immunoprecipitation techniques have identified the early tyrosine-phosphorylated signals as being the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI 3-K) and focal adhesion kinase (FAK). Tyrosine phosphorylation of the p85 subunit of PI 3-K showed a biphasic response to TSP-1 stimulation, which corresponded to a biphasic activation of the lipid kinase. Treatment with both wortmannin and LY294002 inhibited PI 3-K activity of HVSMCs but did not affect tyrosine phosphorylation of the p85 regulatory subunit. TSP-1-stimulated FAK phosphorylation, however, was substantially reduced by these inhibitors, as was the TSP-1-induced chemotaxis of these cells. These results suggest that activation of PI 3-K is an early signal induced by TSP-1 and is critical for chemotaxis. Activation of this kinase precedes and may occur upstream from FAK phosphorylation, although the nature of the interaction between these 2 enzymes remains obscure.