Alkylsulfonamide-containing quinazoline derivatives as potent and orally bioavailable PI3Ks inhibitors

Phosphoinositide 3-kinases (PI3Ks) are regarded as promising targets for treatment of various cancers due to their roles in regulating cell proliferation, differentiation, migration, and survival. Here we report our efforts to develop potent and orally bioavailable PI3K inhibitors for the treatment of cancers. The alkylsulfonamide-containing quinazoline derivatives A1–A18 significantly inhibited PI3Kα, and cell proliferation among HCT-116, MCF-7 and SU-DHL-6 cell lines. The optimal compound A1 displayed potent inhibitory activity against PI3Kα (IC₅₀ = 4.5 nM), PI3Kβ (IC₅₀ = 4.5 nM), PI3Kγ (IC₅₀ = 4.5 nM), PI3Kδ (IC₅₀ = 4.5 nM) and significantly inhibited the growth of HCT-116, MCF-7 and SU-DHL-6 cell lines with IC₅₀ values of 0.82 µM, 0.99 µM and 0.19 µM, respectively. Western blot analysis demonstrated A1 significantly suppressed the phosphorylation of AKT^S473 in a dose-dependent manner. Furthermore, A1 could markedly inhibit cancer growth at the dose of 25 mg/kg in nude mouse HCT-116 xenograft model in vivo without causing significant weight loss or toxicity.     

PLEKHS1 drives PI3Ks and remodels pathway homeostasis in PTEN-null prostate

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MET inhibition enhances PARP inhibitor efficacy in castration-resistant prostate cancer by suppressing the ATM/ATR and PI3K/AKT pathways

Up to 30% of patients with metastatic castration-resistant prostate cancer (CRPC) patients carry altered DNA damage response genes, enabling the use of poly adenosine diphosphate–ribose polymerase (PARP) inhibitors in advanced CRPC. The proto-oncogene mesenchymal–epithelial transition (MET) is crucial in the migration, proliferation, and invasion of tumour cells. Aberrant expression of MET and its ligand hepatocyte growth factor is associated with drug resistance in cancer therapy. Here, we found that MET was highly expressed in human CRPC tissues and overexpressed in DU145 and PC3 cells in a drug concentration-dependent manner and is closely related to sensitivity to PARP inhibitors. Combining the PARP inhibitor olaparib with the MET inhibitor crizotinib synergistically inhibited CRPC cell growth both in vivo and in vitro. Further analysis of the underlying molecular mechanism underlying the MET suppression-induced drug sensitivity revealed that olaparib and crizotinib could together downregulate the ATM/ATR signaling pathway, inducing apoptosis by inhibiting the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway, enhancing the olaparib-induced antitumour effect in DU145 and PC3 cells. In conclusion, we demonstrated that MET inhibition enhances sensitivity of CRPC to PARP inhibitors by suppressing the ATM/ATR and PI3K/AKT pathways and provides a novel, targeted therapy regimen for CRPC.     

Common mechanisms of PIKK regulation

Kinases in the phosphoinositide three-kinase-related kinase (PIKK) family include ATM (ataxia-telangiectasia mutated), ATR (ATM- and Rad3-related), DNA-PKcs (DNA-dependent protein kinase catalytic subunit), mTOR (mammalian target of rapamycin), and SMG1 (suppressor with morphological effect on genitalia family member). These atypical protein kinases regulate DNA damage responses, nutrient-dependent signaling, and nonsense-mediated mRNA decay. This review focuses on the mechanisms regulating the PIKK family with a strong emphasis on the DNA damage regulated kinases. We outline common regulatory themes and suggest how discoveries about the regulation of one PIKK can be informative for the other family members.     

Discovery of pyrazolopyrimidine derivatives as novel inhibitors of ataxia telangiectasia and rad3 related protein (ATR)

The ATR pathway is a critical mediator of the replication stress response in cells. In aberrantly proliferating cancer cells, this pathway can help maintain sufficient genomic integrity for cancer cell progression. Herein we describe the discovery of 19, a pyrazolopyrimidine-containing inhibitor of ATR via a strategic repurposing of compounds targeting PI3K.     

PI3K和Akt蛋白在异丙肾上腺素所致大鼠心肌肥厚中的表达

目的研究异丙肾上腺素(ISO)致大鼠心肌肥厚中PI3K和Akt在心肌组织中的表达,为探讨心肌肥厚的信号转导机制和逆转心肌肥厚提供形态学资料.方法健康成年SD大鼠20只,随机分为实验组、对照组,每组10只.实验组给予异丙肾上腺素处理.1周后处死大鼠,取心肌组织,常规石蜡切片,HE染色,观察心肌组织的病理变化,测量心肌肥厚指标;免疫组织化学染色和免疫荧光染色,检测p-PI3K和p-Akt的表达及分布.结果实验组大鼠心肌肥厚指标与对照组相比均明显升高;免疫组织化学检测显示,实验组心肌组织p-PI3K和p-Akt蛋白表达面积和平均光密度较对照组高.免疫荧光检测实验组心肌组织p-PI3K和p-Akt蛋白表达较对照组高.结论小剂量持续给予 ISO 能建立大鼠心肌肥厚模型;p-PI3K和p-Akt蛋白表达均与心肌肥厚的发生和发展过程相关,PI3K/Akt信号通路激活,可能是导致心肌肥厚的机制之一.     

PI3K 抑制剂抗肿瘤临床研究进展

磷脂酰肌醇-3-激酶 (PI3K) 是一种胞内磷脂酰肌醇激酶,在介导细胞生长、发育、分裂、分化和凋亡等过程中发挥重要作用,因此 PI3K 抑制剂的开发已成为当前抗癌新药研究的热点之一。目前已有多个 PI3K 抑制剂进入临床研究阶段或已上市,其单用或与其他药物联 用的疗效和安全性有待进一步临床验证。综述 PI3K 抑制剂作为抗肿瘤药物的临床研究进展,为其进一步研究与应用提供参考。     

Class IA PI3Ks regulate subcellular and functional dynamics of IDO1

Knowledge of a protein’s spatial dynamics at the subcellular level is key to understanding its function(s), interactions, and associated intracellular events. Indoleamine 2,3‐dioxygenase 1 (IDO1) is a cytosolic enzyme that controls immune responses via tryptophan metabolism, mainly through its enzymic activity. When phosphorylated, however, IDO1 acts as a signaling molecule in plasmacytoid dendritic cells (pDCs), thus activating genomic effects, ultimately leading to long‐lasting immunosuppression. Whether the two activities—namely, the catalytic and signaling functions—are spatially segregated has been unclear. We found that, under conditions favoring signaling rather than catabolic events, IDO1 shifts from the cytosol to early endosomes. The event requires interaction with class IA phosphoinositide 3‐kinases (PI3Ks), which become activated, resulting in full expression of the immunoregulatory phenotype in vivo in pDCs as resulting from IDO1‐dependent signaling events. Thus, IDO1’s spatial dynamics meet the needs for short‐acting as well as durable mechanisms of immune suppression, both under acute and chronic inflammatory conditions. These data expand the theoretical basis for an IDO1‐centered therapy in inflammation and autoimmunity.     

Functions and regulation of human artemis in double strand break repair

Cells, which lacked the activity of the nuclease Artemis, retained approximately 10% of unrepaired double strand breaks (DSBs) at later timepoints after ionizing radiation. Ionizing radiation induced hyperphosphorylation of Artemis mainly by ATM and in ATM deficient cells to a minor extent by DNA PK. After induction of DSBs with modified ends by a high dose of calicheamicin gamma1, Artemis was phosphorylated by DNA PK. The type of calicheamicin gamma1-induced DSBs is likely to represent a subclass of DSBs induced by ionizing radiation. DNA PK-dependent phosphorylation of Artemis after treatment with DSB inducing agents increased the cellular retention of Artemis, maintained its interaction with DNA ends and activated its endonucleolytic activity. The following model is suggested: ATM-dependent phosphorylation of Artemis after ionizing radiation could prevent DNA PK-dependent phosphorylation and activation of undesired endonucleolytic activity at DSBs, which do not require endonucleolytic processing by Artemis. The Artemis:DNA PK complex could be involved in the repair of DSBs, which carry modified ends and are refractory to repair by otherwise lesion specific enzymes because of the presence of an inhibitory lesion in the opposite strand.     

Detailed role of microRNA-mediated regulation of PI3K/AKT axis in human tumors

The regulation of signal transmission and biological processes, such as cell proliferation, apoptosis, metabolism, migration, and angiogenesis are greatly influenced by the PI3K/AKT signaling pathway. Highly conserved endogenous non-protein-coding RNAs known as microRNAs (miRNAs) have the ability to regulate gene expression by inhibiting mRNA translation or mRNA degradation. MiRNAs serve key role in PI3K/AKT pathway as upstream or downstream target, and aberrant activation of this pathway contributes to the development of cancers. A growing body of research shows that miRNAs can control the PI3K/AKT pathway to control the biological processes within cells. The expression of genes linked to cancers can be controlled by the miRNA/PI3K/AKT axis, which in turn controls the development of cancer. There is also a strong correlation between the expression of miRNAs linked to the PI3K/AKT pathway and numerous clinical traits. Moreover, PI3K/AKT pathway-associated miRNAs are potential biomarkers for cancer diagnosis, therapy, and prognostic evaluation. The role and clinical applications of the PI3K/AKT pathway and miRNA/PI3K/AKT axis in the emergence of cancers are reviewed in this article.     

Inhibition of glycolytic metabolism in glioblastoma cells by Pt3glc combinated with PI3K inhibitor via SIRT3-mediated mitochondrial and PI3K/Akt–MAPK pathway

Glioblastoma multiforme (GBM) is the most malignant and aggressive glioma with abnormal expression of genes that mediate glycolytic metabolism and tumor cell growth. Petunidin-3-O-glucoside (Pt3glc) is a kind of anthocyanin in the red grape and derived beverages, representing the most common naturally occurring anthocyanins with a reduced incidence of cancer and heart diseases. In this study, whether Pt3glc could effectively regulate glycolysis to inhibit GBM cell was investigated by using the DBTRG-05MG cell lines. Notably, Pt3glc displayed potent antiproliferative activity and significantly changed the protein levels related to both glycolytic metabolism and GBM cell survival. The expression of the proapoptotic protein Bcl-2-associated X protein was increased with concomitant reduction on the levels of the antiapoptotic protein B-cell lymphoma 2 and caspase-3 activity. Furthermore, the levels of survival signaling proteins, such as protein kinase B (Akt) and phospho-Akt (Scr473), extracellular signal-regulated kinase (ERK) and phospho-ERK, were significantly decreased by Pt3glc in combination with the phosphoinositide 3-kinase (PI3K) inhibitor of LY294002. Most importantly, the levels of Sirtuin 3 (SIRT3) and phosphorylated p53 were also downregulated, indicating that Pt3glc combinated with PI3K inhibitor could induce GBM cell death may act via the SIRT3/p53-mediated mitochondrial and PI3K/Akt-ERK pathways. Our findings thus provide rational evidence that the combination of Pt3glc with PI3K inhibitor, which target alternative pathways in GBM cells, may be a useful adjuvant therapy in glioblastoma treatment.     

Discovery and biological activity of a novel class I PI3K inhibitor, CH5132799

Phosphatidylinositol 3-kinase (PI3K) is a lipid kinase and a promising therapeutic target for cancer. Using structure-based drug design (SBDD), we have identified novel PI3K inhibitors with a dihydropyrrolopyrimidine skeleton. Metabolic stability of the first lead series was drastically improved by replacing phenol with aminopyrimidine moiety. CH5132799, a novel class I PI3K inhibitor, exhibited a strong inhibitory activity especially against PI3Kα (IC₅₀ = 0.014 μM). In human tumor cell lines with PI3K pathway activation, CH5132799 showed potent antiproliferative activity. CH5132799 is orally available and showed significant antitumor activity in PI3K pathway-activated human cancer xenograft models in mice.     

PI3K-Akt pathway: Its functions and alterations in human cancer

Phosphatidylinositol-3-kinase (PI3K) is a lipid kinase and generates phosphatidylinositol-3,4,5-trisphosphate (PI(3, 4, 5)P3). PI(3, 4, 5)P3 is a second messenger essential for the translocation of Akt to the plasma membrane where it is phosphorylated and activated by phosphoinositide-dependent kinase (PDK) 1 and PDK2. Activation of Akt plays a pivotal role in fundamental cellular functions such as cell proliferation and survival by phosphorylating a variety of substrates. In recent years, it has been reported that alterations to the PI3K-Akt signaling pathway are frequent in human cancer. Constitutive activation of the PI3K-Akt pathway occurs due to amplification of the PIK3C gene encoding PI3K or the Akt gene, or as a result of mutations in components of the pathway, for example PTEN (phosphatase and tensin homologue deleted on chromosome 10), which inhibit the activation of Akt. Several small molecules designed to specifically target PI3K-Akt have been developed, and induced cell cycle arrest or apoptosis in human cancer cells in vitro and in vivo . Moreover, the combination of an inhibitor with various cytotoxic agents enhances the anti-tumor efficacy. Therefore, specific inhibition of the activation of Akt may be a valid approach to treating human malignancies and overcoming the resistance of cancer cells to radiation or chemotherapy.     

Reciprocal regulation of Notch and PI3K/Akt signalling in T-ALL cells in vitro

Notch signalling plays an important role in hematopoiesis and in the pathogenesis of T-ALL. Notch is known to interact with Ras and PTEN/PI3K (phosphoinositide-3 kinase)/Akt pathways. We investigated the interaction of Notch with these pathways and the possible reciprocal regulation of these signalling systems in T-ALL cells in vitro. Our analyses indicate that the PI3K/Akt pathway is constitutively active in the four T-ALL cell lines tested. Akt phosphorylation was not altered by the sequestration of growth factors, that is, Akt activation seems to be less dependent on but not completely independent of growth factors, possibly being not subject to negative feedback regulation. PTEN expression was not detected in 3/4 cell lines tested, suggesting the loss of PTEN-mediated Akt activation. Inhibition of the PI3K/Akt pathway arrests growth and enhances apoptosis, but with no modulation of expression of Bax-alpha and Bcl-2 proteins. We analysed the relationship between Notch-1 and the PI3K/Akt signalling and show that inhibition of the Akt pathway changes Notch expression; Notch-1 protein decreased in all the cell lines upon treatment with the inhibitor. Our studies strongly suggest that Notch signalling interacts with PI3K/Akt signalling and further that this occurs in the absence of PTEN expression. The consequences of this to the signalling outcome are yet unclear, but we have uncovered a significant inverse relationship between Notch and PI3K/Akt pathway, which leads us to postulate the operation of a reciprocal regulatory loop between Notch and Ras-PI3K/Akt in the pathogenesis of T-ALL.     

Study on improving the selectivity of compounds that inhibit two PI3Ks (gamma and delta)

A desirable characteristic of PI3K inhibitors is their selectivity. Up to now, there has been no report that describes the 3 D-structure differences between two PI3Ks (δ and γ) and applies them to designing selective compounds. In the present study, we used an approach combining protein-structure modeling, GRID/PCA (Principal Component Analysis) and docking methods to investigate the detail interactions of the two PI3Ks with various chemical groups. At first, we constructed a 3 D-model of the PI3Kδ catalytic subunit with the program Modeller7.0 based on the high resolution X-ray structure of the PI3Kγ catalytic subunit, and then employed GRID and PCA to reveal the most relevant structural and physicochemical differences between the two PI3Ks related to their selectivity. As a result, the analysis unveiled the most important regions on the two PI3Ks that should be taken into account for the design of selective inhibitors. Finally, based on activity data of 10 PI3Kδ-selective compounds, a docking study validated the results of the GRID/PCA method, which suggested that the approach could provide clear guidelines for selective drug design.     

PI3K‐p110‐alpha‐subtype signalling mediates survival,proliferation and neurogenesis of cortical progenitor cells via activation of mTORC2

Development of the cerebral cortex is controlled by growth factors among which transforming growth factor beta (TGFβ) and insulin‐like growth factor 1 (IGF1) have a central role. The TGFβ‐ and IGF1‐pathways cross‐talk and share signalling molecules, but in the central nervous system putative points of intersection remain unknown. We studied the biological effects and down‐stream molecules of TGFβ and IGF1 in cells derived from the mouse cerebral cortex at two developmental time points, E13.5 and E16.5. IGF1 induces PI3K, AKT and the mammalian target of rapamycin complexes (mTORC1/mTORC2) primarily in E13.5‐derived cells, resulting in proliferation, survival and neuronal differentiation, but has small impact on E16.5‐derived cells. TGFβ has little effect at E13.5. It does not activate the PI3K‐ and mTOR‐signalling network directly, but requires its activity to mediate neuronal differentiation specifically at E16.5. Our data indicate a central role of mTORC2 in survival, proliferation as well as neuronal differentiation of E16.5‐derived cortical cells. mTORC2 promotes these cellular processes and is under control of PI3K‐p110‐alpha signalling. PI3K‐p110‐beta signalling activates mTORC2 in E16.5‐derived cells but it does not influence cell survival, proliferation and differentiation. This finding indicates that different mTORC2 subtypes may be implicated in cortical development and that these subtypes are under control of different PI3K isoforms.