The cell biology behind the oncogenic PIP3 lipids

Design, synthesis, molecular modelling and biological evaluation of novel 6-amino-5-cyano-2-thiopyrimidine derivatives as potent anticancer agents against leukemia and apoptotic inducers

Herein, a novel series of 6-amino-5-cyano-2-thiopyrimidines and condensed pyrimidines analogues were prepared. All the synthesized compounds (1a-c, 2a-c, 3a-c, 4a-r and 5a-c) were evaluated for in vitro anticancer activity by the National Cancer Institute (NCI; MD, USA) against 60 cell lines. Compound 1c showed promising anticancer activity and was selected for the five-dose testing. Results demonstrated that compound 1c possessed broad spectrum anti-cancer activity against the nine cancerous subpanels tested with selectivity ratio ranging from 0.7 to 39 at the GI50 level with high selectivity towards leukaemia. Mechanistic studies showed that Compound 1c showed comparable activity to Duvelisib against PI3Kδ (IC50 = 0.0034 and 0.0025 μM, respectively) and arrested cell cycle at the S phase and displayed significant increase in the early and late apoptosis in HL60 and leukaemia SR cells. The necrosis percentage showed a significant increase from 1.13% to 3.41% in compound 1c treated HL60 cells as well as from 1.51% to 4.72% in compound 1c treated leukaemia SR cells. Also, compound 1c triggered apoptosis by activating caspase 3, Bax, P53 and suppressing Bcl2. Moreover, 1c revealed a good safety profile against human normal lung fibroblast cell line (WI-38 cells). Molecular analysis of Duvelisib and compound 1c in PI3K was performed. Finally, these results suggest that 2-thiopyrimidine derivative 1c might serve as a model for designing novel anticancer drugs in the future.

PI3Kα inhibitor GNE-493 triggers antitumor immunity in murine lung cancer by inducing immunogenic cell death and activating T cells

Phosphatidylinositol 3-kinase (PI3K) is frequently hyperactivated in cancer, playing pivotal roles in the pathophysiology of both malignant and immune cells. The impact of PI3K inhibitors on the tumor microenvironment (TME) within lung cancer remains largely unknown. In this study, we explored the regulatory effects of GNE-493, an innovative dual inhibitor of PI3K and mammalian target of rapamycin (mTOR), on the TME of lung cancer. First, through the analysis of The Cancer Genome Atlas-lung squamous cell carcinoma (LUSC) cohort, we found PIK3CA to be related to CD8 T cells, which may affect the overall survival rate of patients by affecting CD8 function. We herein demonstrated that GNE-493 can significantly inhibit tumor cell proliferation and promote cell apoptosis while increasing the expression of the immunogenic death-related molecules CRT and HSP70 using in vitro cell proliferation and apoptosis experiments on the murine KP lung cancer cell line and human A549 lung cancer cell line. Next, through the establishment of an orthotopic tumor model in vivo, it was found that after GNE-493 intervention, the infiltration of CD4+ and CD8+ T cells in mouse lung tumor was significantly increased, and the expression of CRT in tumors could be induced to increase. To explore the mechanisms underlying PI3K inhibition-induced changes in the TME, the gene expression differences of T cells in the control group versus GNE-493-treated KP tumors were analyzed by RNA-seq, and the main effector pathway of anti-tumor immunity was identified. The IFN/TNF family molecules were significantly upregulated after GNE-493 treatment. In summary, our findings indicate that GNE-493 promotes immunogenic cell death in lung cancer cells, and elucidates its regulatory impact on molecules associated with the adaptive immune response. Our study provides novel insights into how PI3K/mTOR inhibitors exert their activity by modulating the tumor-immune interaction.

Structural insights into the activation mechanism of phosphoinositide 3-kinase alpha

Phosphoinositide 3-kinases (PI3Ks) are lipid kinases known to regulate important cellular functions by phosphorylating the inositol ring of inositol-phospholipids (PtdIns) at 3' position. The PI3Kα is a heterodimer and the activation of the catalytic subunit (p110α) is regulated by its regulatory subunit (p85α). The current work deals with studying the activation mechanism of the PI3Kα using multi micro-second molecular dynamic simulations. Structural changes involved in activation mechanism is studied by gradually releasing the inhibitory effects of different domains of regulatory subunit namely, n-terminal SH2 (nSH2) and inter SH2 (iSH2). The observation shows that even in the presence of n-terminal and inter SH2 domain (niSH2) of regulatory subunit, the catalytic domain has some intrinsic activation activity and the presence of c-terminal SH2 (cSH2) domain may be required for complete inhibition. The release of nSH2 domain leads to loss of interactions between iSH2 domain (regulatory subunit) and C2 and kinase domain (catalytic subunit). The study shows that early events in the activation mechanism involve the movement of the ABD domain of the catalytic subunit along with the linker region between ABD and RBD region which may lead to movement of ABD closer to the CLobe of the kinase domain. This movement is essentially as it triggers the rearrangement of CLobe especially the catalytic loop and activation loop which bring catalytic important residues closer to ATP and PIP2(phosphatidylinositol-4,5-bisphosphate). Water mediated interaction analysis reveal that water may be playing an important role in the transfer of phosphate from ATP to PIP2. The study shows that initial signal for release of inhibitory effect of the regulatory subunit might be propagated through the linker region between ABD and RBD through allosteric effect to different regions of the protein. These understanding of early events during the activation mechanism may help in the design of better therapeutic targeting PI3K.

Therapeutic potential of anti-PIK3CG treatment for multiple myeloma via inhibiting c-Myc pathway

Multiple myeloma (MM) is a malignant plasma cell disease. The activity of PIK3CG (PI3K catalytic subunit γ) is regulated directly by G-protein-coupled receptor and has been confirmed to be highly expressed in MM cells. This study aimed to determine the effect of pharmacological inhibition of PIK3CG on MM. We found that different concentrations of the PIK3CG inhibitor AS-605240 could suppress the growth of MM cell lines and the expression of c-Myc. The combination of PIK3CG inhibitor and the chemotherapy Melphalan could effectively inhibit the proliferation and migration of MM cells, promote the cell apoptosis, and decrease the ratio of Bcl-2/Bax and the expression of vimentin. The expression of proto-oncogene c-Myc was decreased and the sensitivity of cells to chemotherapeutic drugs was enhanced. Collectively, PIK3CG regulates growth of MM via c-Myc pathway, thus emerging as a promising molecular targeted therapy.

Design, synthesis and evaluation of 2, 6, 8-substituted Imidazopyridine derivatives as potent PI3Kα inhibitors

Inhibition of PI3K pathway has become a desirable strategy for cancer treatment. In this work, a series of 2, 6, 8-substituted Imidazo[1,2-a]pyridine derivatives were designed and screened for their activities against PI3Kα and a panel of PI3Kα-addicted cancer cells. Among them, compound 35 was identified as a PI3Kα inhibitor with nanomolar potency as well as acceptable antiproliferative activity. Flow cytometry analysis confirmed 35 induced cell cycle arrest and apoptosis in T47D cells. In addition, it also showed desirable in vitro ADME properties. The design, synthesis, and SAR exploration of 35 are described within.

Anti-cancer effect of palmatine through inhibition of the PI3K/AKT pathway in canine mammary gland tumor CMT-U27 cells

Canine mammary gland tumors (CMTs) are the most common and lethal cancers in female dogs. Dysregulated phosphoinositide 3-kinases (PI3K)/AKT pathway reportedly was involved in the growth and metastasis of CMTs. However, there are few studies on therapeutic strategies for targeting the PI3K pathway in CMTs. In this study, we aimed to determine whether palmatine, a natural isoquinoline alkaloid with anti-cancer properties, could inhibit the growth of CMTs and whether the inhibitory effect was mediated through the PI3K/AKT pathway. Our in vitro experiments on CMT-U27, a CMT cell line, showed that palmatine reduced cell proliferation and induced cell death. Western blotting results revealed that palmatine decreased the protein expression of PI3K, PTEN, AKT, and mechanistic target of rapamycin in the PI3K/AKT pathway, which was supported by the results of immunocytochemistry. Additionally, palmatine suppressed the migration and tube formation of canine aortic endothelial cells as well as the migration of CMT U27 cells. Our in vivo results showed that palmatine inhibited tumor growth in a CMT-U27 mouse xenograft model. We observed a decreased expression of proteins in the PI3K/AKT pathway in tumor tissues, similar to the in vitro results. Furthermore, palmatine significantly disrupted the tumor vasculature and inhibited metastasis to adjacent lymph nodes. In conclusion, our findings demonstrate that palmatine exerts anti-cancer effects against CMTs by inhibiting PI3K/AKT signaling pathway, suggesting that palmatine has potential as a canine-specific PI3K inhibitor for the treatment of CMTs.

PI3K signaling-regulated metabolic reprogramming: From mechanism to application

Oncogenic signaling involved in tumor metabolic reprogramming. Tumorigenesis was not only determined by the mutations or deletion of oncogenes but also accompanied by the reprogramming of cellular metabolism. Metabolic alterations play a crucial regulatory role in the development and progression of tumors. Oncogenic PI3K/AKT signaling mediates the metabolic switch in cancer cells and immune cells in the tumor microenvironment. PI3K/AKT and its downstream effector branch off and connect to multiple steps of metabolism, such as glucose, lipids, and amino acids. Thus, PI3K inhibitor could effectively regulate metabolic pathway and impede the oncogenic process and some key metabolic proteins or critical enzymes also constitute biomarkers for tumor diagnosis and treatment. In the current review, we summarize the significant effect of PI3K/AKT signaling toward tumor metabolism, it enables us to obtain the better understanding for this interaction and develop more effective therapeutic strategies targeting cancer cell metabolism.

The Effects of Cinobufagin on Hepatocellular Carcinoma Cells Enhanced by MRT68921, an Autophagy Inhibitor

Cinobufagin, a cardiotonic steroid derived from toad venom extracts, exhibits significant anticancer properties by inhibiting Na[Formula: see text]/K[Formula: see text]-ATPase in cancer cells. It is frequently used in clinical settings to treat advanced-stage cancer patients, improving their quality of life and survival time. However, its long-term use can result in multidrug resistance to other chemotherapy drugs, and the exact mechanism underlying this effect remains unknown. Therefore, this study explores the molecular mechanism underlying the anticancer effects of cinobufagin in hepatocellular carcinomas (HCCs), specifically in HepG2 and Huh-7 cells. As determined using transcriptome analysis, cinobufagin-triggered protective autophagy suppressed cell apoptosis in liver cancer HepG2 and Huh-7 cells by inhibiting the phosphoinositide-3-Kinase (PI3K)-AKT serine/threonine kinase (AKT)-mammalian target of rapamycin (mTOR) pathway. Cinobufagin-inhibited cell proliferation, induced apoptosis, and generated cell autophagy by upregulating the expression of MAP1 light chain 3 protein II, Beclin1, and autophagy-related protein 12-5. In addition, the autophagy inhibitor MRT68921 improved the antiproliferative and proapoptotic effects of cinobufagin in the studied cell lines. Overall, this study suggests that combining cinobufagin with an autophagy inhibitor can effectively treat HCC, providing a potential strategy for cancer therapy.

Effect of a high-fat meal on the relative bioavailability of HMPL-689 in Chinese healthy volunteers

The aim of this study was to investigate the effect of a high-fat meal on the single-dose pharmacokinetics (PK) and tolerability of HMPL-689 in Chinese healthy volunteers. In this study, 34 eligible male volunteers received a single 30-mg dose of HMPL-689 capsules following an overnight fast or a high-fat breakfast prior to dosing. Blood samples were collected at the designated time points for pharmacokinetic analysis. Safety and tolerability were assessed throughout the study. Total 32 healthy male volunteers were completed in the study. The GMRs of AUC_0-t , AUC_0-∞ , and C_max and their 90% CIs were 1.12 (1.09, 1.15), 1.12 (1.09, 1.15), and 0.64 (0.58, 0.70), respectively, in healthy male subjects after oral administration of HMPL-689 following intake of a high-fat diet versus under fasting state. The 90% CI of C_max GMR fell outside the acceptable equivalent range (0.8-1.25). In addition, the median T_max of HMPL-689 was 1.0 and 4.0 h under the fasting and the fed conditions. The study indicated that intake of a high-fat diet had an impact on the in vivo PK profile of HMPL-689 in healthy Chinese male subjects, which could obviously reduce the oral absorption rate of HMPL-689 and had little effect on the extent of oral absorption (AUC).

Lipid metabolism in cancer progression and therapeutic strategies

Dysregulated lipid metabolism represents an important metabolic alteration in cancer. Fatty acids, cholesterol, and phospholipid are the three most prevalent lipids that act as energy producers, signaling molecules, and source material for the biogenesis of cell membranes. The enhanced synthesis, storage, and uptake of lipids contribute to cancer progression. The rewiring of lipid metabolism in cancer has been linked to the activation of oncogenic signaling pathways and cross talk with the tumor microenvironment. The resulting activity favors the survival and proliferation of tumor cells in the harsh conditions within the tumor. Lipid metabolism also plays a vital role in tumor immunogenicity via effects on the function of the noncancer cells within the tumor microenvironment, especially immune‐associated cells. Targeting altered lipid metabolism pathways has shown potential as a promising anticancer therapy. Here, we review recent evidence implicating the contribution of lipid metabolic reprogramming in cancer to cancer progression, and discuss the molecular mechanisms underlying lipid metabolism rewiring in cancer, and potential therapeutic strategies directed toward lipid metabolism in cancer. This review sheds new light to fully understanding of the role of lipid metabolic reprogramming in the context of cancer and provides valuable clues on therapeutic strategies targeting lipid metabolism in cancer.

PIK3CA Mutations as a Molecular Target for Hormone Receptor-Positive, HER2-Negative Metastatic Breast Cancer

Despite the significant achievements in the diagnosis and treatment of metastatic breast cancer (MBC), this condition remains substantially an incurable disease. In recent years, several clinical studies have aimed to identify novel molecular targets, therapeutic strategies, and predictive biomarkers to improve the outcome of women with MBC. Overall, ~40% of hormone receptor (HR)+/HER2- MBC cases harbor alterations affecting the (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. This pathway is a major target in oncogenesis, as it regulates growth, proliferation, cell survival, and angiogenesis. Lately, the pharmacologic targeting of PIK3CA in HR+/HER2- MBC has shown significant benefits after the occurrence of endocrine therapy resistance. The orally available α-selective PIK3CA inhibitor, alpelisib, has been approved in this setting. To perform an optimal patients' selection for this drug, it is crucial to adopt a tailored methodology. Clinically relevant PIK3CA alterations may be detected in several biospecimens (e.g. tissue samples and liquid biopsy) using different techniques (e.g. real-time PCR and next-generation sequencing). In this study, we provide an overview of the role of PIK3CA in breast cancer and of the characterization of its mutational status for appropriate clinical management.

PI3K Driver Mutations: A Biophysical Membrane-Centric Perspective

Ras activates its effectors at the membrane. Active PI3Kα and its associated kinases/phosphatases assemble at membrane regions enriched in signaling lipids. In contrast, the Raf kinase domain extends into the cytoplasm and its assembly is away from the crowded membrane surface. Our structural membrane-centric outlook underscores the spatiotemporal principles of membrane and signaling lipids, which helps clarify PI3Kα activation. Here we focus on mechanisms of activation driven by PI3Kα driver mutations, spotlighting the PI3Kα double (multiple) activating mutations. Single mutations can be potent, but double mutations are stronger: their combination is specific, a single strong driver cannot fully activate PI3K, and two weak drivers may or may not do so. In contrast, two strong drivers may successfully activate PI3K, where one, for example, H1047R, modulates membrane interactions facilitating substrate binding at the active site (km) and the other, for example, E542K and E545K, reduces the transition state barrier (ka), releasing autoinhibition by nSH2. Although mostly unidentified, weak drivers are expected to be common, so we ask here how common double mutations are likely to be and why PI3Kα with double mutations responds effectively to inhibitors. We provide a structural view of hotspot and weak driver mutations in PI3Kα activation, explain their mechanisms, compare these with mechanisms of Raf activation, and point to targeting cell-specific, chromatin-accessible, and parallel (or redundant) pathways to thwart the expected emergence of drug resistance. Collectively, our biophysical outlook delineates activation and highlights the challenges of drug resistance.

Structural Features that Distinguish Inactive and Active PI3K Lipid Kinases

PI3K lipid kinases signal through the PI3K/Akt pathway, regulating cell growth and proliferation. While the structural features that distinguish between the active and inactive states of protein kinases are well established, that has not been the case for lipid kinases, and neither was the structural mechanism controlling the switch between the two states. Class I PI3Ks are obligate heterodimers with catalytic and regulatory subunits. Here, we analyze PI3K crystal structures. Structures with the nSH2 (inactive state) are featured by collapsed activation loop (a-loop) and an IN kinase domain helix 11 (kα11). In the active state, the a-loop is extended and kα11 in the OUT conformation. Our analysis suggests that the nSH2 domain in the regulatory subunit regulates activation, catalysis and autoinhibition through the a-loop. Inhibition, activation and catalytic scenarios are shared by class IA PI3Ks; the activation is mimicked by oncogenic mutations and the inhibition offers an allosteric inhibitor strategy.

PI3K inhibitors: review and new strategies

The search is on for effective specific inhibitors for PI3Kα mutants. PI3Kα, a critical lipid kinase, has two subunits, catalytic and inhibitory. PIK3CA, the gene that encodes the p110α catalytic subunit is a highly mutated protein in cancer. Dysregulation of PI3Kα signalling is commonly associated with tumorigenesis and drug resistance. Despite its vast importance, only recently the FDA approved the first drug (alpelisib by Novartis) for breast cancer. A second (GDC0077), classified as PI3Kα isoform-specific, is undergoing clinical trials. Not surprisingly, these ATP-competitive drugs commonly elicit severe concentration-dependent side effects. Here we briefly review PI3Kα mutations, focus on PI3K drug repertoire and propose new, to-date unexplored PI3Kα therapeutic strategies. These include (1) an allosteric and orthosteric inhibitor combination and (2) taking advantage of allosteric rescue mutations to guide drug discovery.

Overexpression of PTEN may increase the effect of pemetrexed on A549 cells via inhibition of the PI3K/AKT/mTOR pathway and carbohydrate metabolism

Lung cancer is one of the leading causes of tumor-associated mortality, and >75% of patients with lung cancer have non-small cell lung cancer (NSCLC). Pemetrexed, a folate antagonist, is a first-line chemotherapy drug for NSCLC that is administered alone or in combination with cisplatin. The present study established in vitro cell models of PTEN inhibition and overexpression, and the effects of the treatment with pemetrexed were investigated in these cell models. Result from the present study demonstrated that treatment with pemetrexed suppressed lung cancer cell proliferation, inhibited mRNA and protein expression levels of anti-apoptotic Bcl2, and increased the mRNA and the protein expression levels of pro-apoptotic p53 and apoptosis regulator BAX. The present study suggested that pemetrexed regulated apoptosis via the inhibition of the mTOR/PI3K/AKT signaling pathway. Additionally, cellular processes associated with the aerobic oxidation of carbohydrates were identified to be significantly inhibited. The present findings suggested that treatment with pemetrexed may exhibit synergistic effects with PTEN on lung cancer cells via the inhibition of the PI3K/AKT/mTOR signaling pathway and through carbohydrate metabolism, and treatment with pemetrexed combined with PTEN overexpression may represent a novel therapeutic strategy for the treatment of NSCLC.