Biological properties of potent inhibitors of class I phosphatidylinositide 3-kinases: from PI-103 through PI-540, PI-620 to the oral agent GDC-0941

Unveiling the role of PIK3R1 in cancer: A comprehensive review of regulatory signaling and therapeutic implications

Phosphoinositide 3-kinase (PI3K) is responsible for phosphorylating phosphoinositides to generate secondary signaling molecules crucial for regulating various cellular processes, including cell growth, survival, and metabolism. The PI3K is a heterodimeric enzyme complex comprising of a catalytic subunit (p110α, p110β, or p110δ) and a regulatory subunit (p85). The binding of the regulatory subunit, p85, with the catalytic subunit, p110, forms an integral component of the PI3K enzyme. PIK3R1 (phosphoinositide-3-kinase regulatory subunit 1) belongs to class IA of the PI3K family. PIK3R1 exhibits structural complexity due to alternative splicing, giving rise to distinct isoforms, prominently p85α and p55α. While the primary p85α isoform comprises multiple domains, including Src homology 3 (SH3) domains, a Breakpoint Cluster Region Homology (BH) domain, and Src homology 2 (SH2) domains (iSH2 and nSH2), the shorter isoform, p55α, lacks certain domains present in p85α. In this review, we will highlight the intricate regulatory mechanisms governing PI3K signaling along with the impact of PIK3R1 alterations on cellular processes. We will further delve into the clinical significance of PIK3R1 mutations in various cancer types and their implications for prognosis and treatment outcomes. Additionally, we will discuss the evolving landscape of targeted therapies aimed at modulating PI3K-associated pathways. Overall, this review will provide insights into the dynamic interplay of PIK3R1 in cancer, fostering advancements in precision medicine and the development of targeted interventions.

Simultaneous inhibition of PI3K and PAK in preclinical models of neurofibromatosis type 2-related schwannomatosis

Neurofibromatosis Type 2 (NF2)-related schwannomatosis is a genetic disorder that causes development of multiple types of nervous system tumors. The primary and diagnostic tumor type is bilateral vestibular schwannoma. There is no cure or drug therapy for NF2. Recommended treatments include surgical resection and radiation, both of which can leave patients with severe neurological deficits or increase the risk of future malignant tumors. Results of our previous pilot high-throughput drug screen identified phosphoinositide 3-kinase (PI3K) inhibitors as strong candidates based on loss of viability of mouse merlin-deficient Schwann cells (MD-SCs). Here we used novel human schwannoma model cells to conduct combination drug screens. We identified a class I PI3K inhibitor, pictilisib and p21 activated kinase (PAK) inhibitor, PF-3758309 as the top combination due to high synergy in cell viability assays. Both single and combination therapies significantly reduced growth of mouse MD-SCs in an orthotopic allograft mouse model. The inhibitor combination promoted cell cycle arrest and apoptosis in mouse merlin-deficient Schwann (MD-SCs) cells and cell cycle arrest in human MD-SCs. This study identifies the PI3K and PAK pathways as potential targets for combination drug treatment of NF2-related schwannomatosis.

Advancements in dual-target inhibitors of PI3K for tumor therapy: Clinical progress, development strategies, prospects

Phosphoinositide 3-kinases (PI3Ks) modify lipids by the phosphorylation of inositol phospholipids at the 3'-OH position, thereby participating in signal transduction and exerting effects on various physiological processes such as cell growth, metabolism, and organism development. PI3K activation also drives cancer cell growth, survival, and metabolism, with genetic dysregulation of this pathway observed in diverse human cancers. Therefore, this target is considered a promising potential therapeutic target for various types of cancer. Currently, several selective PI3K inhibitors and one dual-target PI3K inhibitor have been approved and launched on the market. However, the majority of these inhibitors have faced revocation or voluntary withdrawal of indications due to concerns regarding their adverse effects. This article provides a comprehensive review of the structure and biological functions, and clinical status of PI3K inhibitors, with a specific emphasis on the development strategies and structure-activity relationships of dual-target PI3K inhibitors. The findings offer valuable insights and future directions for the development of highly promising dual-target drugs targeting PI3K.

The mTOR Signaling Pathway and mTOR Inhibitors in Cancer: Next-generation Inhibitors and Approaches

mTOR is a serine/threonine kinase that plays various roles in cell growth, proliferation, and metabolism. mTOR signaling in cancer becomes irregular. Therefore, drugs targeting mTOR have been developed. Although mTOR inhibitors rapamycin and rapamycin rapalogs (everolimus, rapamycin, temsirolimus, deforolimus, etc.) and new generation mTOR inhibitors (Rapalink, Dual PI3K/mTOR inhibitors, etc.) are used in cancer treatments, mTOR resistance mechanisms may inhibit the efficacy of these drugs. Therefore, new inhibition approaches are developed. Although these new inhibition approaches have not been widely investigated in cancer treatment, the use of nanoparticles has been evaluated as a new treatment option in a few types of cancer. This review outlines the functions of mTOR in the cancer process, its resistance mechanisms, and the efficiency of mTOR inhibitors in cancer treatment. Furthermore, it discusses the next-generation mTOR inhibitors and inhibition strategies created using nanoparticles. Since mTOR resistance mechanisms prevent the effects of mTOR inhibitors used in cancer treatments, new inhibition strategies should be developed. Inhibition approaches are created using nanoparticles, and one of them offers a promising treatment option with evidence supporting its effectiveness.

Discovery of novel potent PI3K/mTOR dual-target inhibitors based on scaffold hopping: Design, synthesis, and antiproliferative activity

The PI3K/AKT/mTOR pathway is one of the most common dysregulated signaling cascade responses in human cancers, playing a crucial role in cell proliferation and angiogenesis. Therefore, the development of anticancer drugs targeting the PI3K and mTOR pathways has become a research hotspot in cancer treatment. In this study, the PI3K selective inhibitor GDC-0941 was selected as a lead compound, and 28 thiophenyl-triazine derivatives with aromatic urea structures were synthesized based on scaffold hopping, serving as a novel class of PI3K/mTOR dual inhibitors. The most promising compound Y-2 was obtained through antiproliferative activity evaluation, kinase inhibition, and toxicity assays. The results showed that Y-2 demonstrated potential inhibitory effects on both PI3K kinase and mTOR kinase, with IC50 values of 171.4 and 10.2 nM, respectively. The inhibitory effect of Y-2 on mTOR kinase was 52 times greater than that of the positive drug GDC-0941. Subsequently, the antitumor activity of Y-2 was verified through pharmacological experiments such as AO staining, cell apoptosis, scratch assays, and cell colony formation. The antitumor mechanism of Y-2 was further investigated through JC-1 experiments, real-time quantitative PCR, and Western blot analysis. Based on the above experiments, Y-2 can be identified as a potent PI3K/mTOR dual inhibitor for cancer treatment.

The myocardium utilizes a platelet-derived growth factor receptor alpha (Pdgfra)-phosphoinositide 3-kinase (PI3K) signaling cascade to steer toward the midline during zebrafish heart tube formation

Coordinated cell movement is a fundamental process in organ formation. During heart development, bilateral myocardial precursors collectively move toward the midline (cardiac fusion) to form the primitive heart tube. Extrinsic influences such as the adjacent anterior endoderm are known to be required for cardiac fusion. We previously showed however, that the platelet-derived growth factor receptor alpha (Pdgfra) is also required for cardiac fusion (Bloomekatz et al., 2017). Nevertheless, an intrinsic mechanism that regulates myocardial movement has not been elucidated. Here, we show that the phosphoinositide 3-kinase (PI3K) intracellular signaling pathway has an essential intrinsic role in the myocardium directing movement toward the midline. In vivo imaging further reveals midline-oriented dynamic myocardial membrane protrusions that become unpolarized in PI3K-inhibited zebrafish embryos where myocardial movements are misdirected and slower. Moreover, we find that PI3K activity is dependent on and interacts with Pdgfra to regulate myocardial movement. Together our findings reveal an intrinsic myocardial steering mechanism that responds to extrinsic cues during the initiation of cardiac development.

Simultaneous Inhibition of PI3K and PAK in Preclinical Models of Neurofibromatosis Type 2-related Schwannomatosis

Neurofibromatosis Type 2 (NF2)-related schwannomatosis is a genetic disorder that causes development of multiple types of nervous system tumors. The primary and diagnostic tumor type is bilateral vestibular schwannoma. There is no cure or drug therapy for NF2. Recommended treatments include surgical resection and radiation, both of which can leave patients with severe neurological deficits or increase the risk of future malignant tumors. Results of our previous pilot high-throughput drug screen identified phosphoinositide 3-kinase (PI3K) inhibitors as strong candidates based on loss of viability of mouse merlin-deficient Schwann cells (MD-SCs). Here we used novel human schwannoma model cells to conduct combination drug screens. We identified a class I PI3K inhibitor, pictilisib and p21 activated kinase (PAK) inhibitor, PF-3758309 as the top combination due to high synergy in cell viability assays. Both single and combination therapies significantly reduced growth of mouse MD-SCs in an orthotopic allograft mouse model. The inhibitor combination promoted cell cycle arrest and apoptosis in mouse merlin-deficient Schwann (MD-SCs) cells and cell cycle arrest in human MD-SCs. This study identifies the PI3K and PAK pathways as potential targets for combination drug treatment of NF2-related schwannomatosis.

A Novel Dual PI3K/mTOR Inhibitor, XIN-10, for the Treatment of Cancer

An imbalance in PI3K/AKT/mTOR pathway signaling in humans often leads to cancer. Therefore, the investigation of anti-cancer medications that inhibit PI3K and mTOR has emerged as a significant area of research. The aim of this study was to explore the effect of XIN-10, a dual PI3K/mTOR inhibitor, on the growth as well as antiproliferation of tumor cells and to investigate the anti-tumor mechanism of XIN-10 by further exploration. We screened three cell lines for more in-depth exploration by MTT experiments. From the AO staining, cell cycle and apoptosis, we found that XIN-10 had a more obvious inhibitory effect on the MCF-7 breast cancer cell line and used this as a selection for more in-depth experiments. A series of in vitro and in vivo experiments showed that XIN-10 has superior antiproliferative activity compared with the positive drug GDC-0941. Meanwhile, through the results of protein blotting and PCR experiments, we concluded that XIN-10 can block the activation of the downstream pathway of mTOR by inhibiting the phosphorylation of AKT(S473) as well as having significant inhibitory effects on the gene exons of PI3K and mTOR. These results indicate that XIN-10 is a highly potent inhibitor with low toxicity and has a strong potential to be developed as a novel PI3Kα/mTOR dual inhibitor candidate for the treatment of positive breast cancer.

Distinct longevity mechanisms across and within species and their association with aging

Lifespan varies within and across species, but the general principles of its control remain unclear. Here, we conducted multi-tissue RNA-seq analyses across 41 mammalian species, identifying longevity signatures and examining their relationship with transcriptomic biomarkers of aging and established lifespan-extending interventions. An integrative analysis uncovered shared longevity mechanisms within and across species, including downregulated Igf1 and upregulated mitochondrial translation genes, and unique features, such as distinct regulation of the innate immune response and cellular respiration. Signatures of long-lived species were positively correlated with age-related changes and enriched for evolutionarily ancient essential genes, involved in proteolysis and PI3K-Akt signaling. Conversely, lifespan-extending interventions counteracted aging patterns and affected younger, mutable genes enriched for energy metabolism. The identified biomarkers revealed longevity interventions, including KU0063794, which extended mouse lifespan and healthspan. Overall, this study uncovers universal and distinct strategies of lifespan regulation within and across species and provides tools for discovering longevity interventions.

Recent advances in PI3K/PKB/mTOR inhibitors as new anticancer agents

The biochemical role of the PI3K/PKB/mTOR signalling pathway in cell-cycle regulation is now well known. During the onset and development of different forms of cancer it becomes overactive reducing apoptosis and allowing cell proliferation. Therefore, this pathway has become an important target for the treatment of various forms of malignant tumors, including breast cancer and follicular lymphoma. Recently, several more or less selective inhibitors targeting these proteins have been identified. In general, drugs that act on multiple targets within the entire pathway are more efficient than single targeting inhibitors. Multiple inhibitors exhibit high potency and limited drug resistance, resulting in promising anticancer agents. In this context, the present survey focuses on small molecule drugs capable of modulating the PI3K/PKB/mTOR signalling pathway, thus representing drugs or drug candidates to be used in the pharmacological treatment of different forms of cancer.

The myocardium utilizes Pdgfra-PI3K signaling to steer towards the midline during heart tube formation

Coordinated cell movement is a fundamental process in organ formation. During heart development, bilateral myocardial precursors collectively move towards the midline (cardiac fusion) to form the primitive heart tube. Along with extrinsic influences such as the adjacent anterior endoderm which are known to be required for cardiac fusion, we previously showed that the platelet-derived growth factor receptor alpha (Pdgfra) is also required. However, an intrinsic mechanism that regulates myocardial movement remains to be elucidated. Here, we uncover an essential intrinsic role in the myocardium for the phosphoinositide 3-kinase (PI3K) intracellular signaling pathway in directing myocardial movement towards the midline. In vivo imaging reveals that in PI3K-inhibited zebrafish embryos myocardial movements are misdirected and slower, while midline-oriented dynamic myocardial membrane protrusions become unpolarized. Moreover, PI3K activity is dependent on and genetically interacts with Pdgfra to regulate myocardial movement. Together our findings reveal an intrinsic myocardial steering mechanism that responds to extrinsic cues during the initiation of cardiac development.

Design, synthesis and pharmacological evaluation of 2-arylurea-1,3,5-triazine derivative (XIN-9): A novel potent dual PI3K/mTOR inhibitor for cancer therapy

Blocking the PI3K/AKT/mTOR pathway has been widely recognized as an attractive cancer therapeutic strategy because of its crucial role in cell growth and survival. In this study, a novel series of 2-arylurea-1,3,5-triazine derivatives had been synthesized and evaluated as highly potent PI3K and mTOR inhibitors. The new compounds exhibited cytotoxic activities against MCF-7, Hela and A549 cancer cell lines (IC₅₀ = 0.03-36.54 μM). The most promising compound XIN-9 exhibited potent inhibition against PI3K and mTOR kinase (IC₅₀ = 23.8 and 10.9 nM). Mechanistic study using real-time PCR revealed the ability of XIN-9 to inhibit PI3K and mTOR. In addition, compound XIN-9 arrested the cell cycle of MCF-7 cells at the G0/G1 phase. XIN-9 also caused a significant dose-dependent increase of early and late apoptotic events. Molecular docking analysis revealed a high binding affinity for XIN-9 toward PI3K and mTOR. Following in vitro studies, XIN-9 was further evaluated in MCF-7 xenograft models to show significant in vivo anticancer efficacies with tumor growth inhibitions of 41.67% (po, 75 mg/kg). Overall, this work indicated that compound XIN-9 represents a potential anticancer targeting PI3K/AKT/mTOR pathway.

Artificial intelligence to guide precision anticancer therapy with multitargeted kinase inhibitors

BACKGROUND

Vast amounts of rapidly accumulating biological data related to cancer and a remarkable progress in the field of artificial intelligence (AI) have paved the way for precision oncology. Our recent contribution to this area of research is CancerOmicsNet, an AI-based system to predict the therapeutic effects of multitargeted kinase inhibitors across various cancers. This approach was previously demonstrated to outperform other deep learning methods, graph kernel models, molecular docking, and drug binding pocket matching.

METHODS

CancerOmicsNet integrates multiple heterogeneous data by utilizing a deep graph learning model with sophisticated attention propagation mechanisms to extract highly predictive features from cancer-specific networks. The AI-based system was devised to provide more accurate and robust predictions than data-driven therapeutic discovery using gene signature reversion.

RESULTS

Selected CancerOmicsNet predictions obtained for "unseen" data are positively validated against the biomedical literature and by live-cell time course inhibition assays performed against breast, pancreatic, and prostate cancer cell lines. Encouragingly, six molecules exhibited dose-dependent antiproliferative activities, with pan-CDK inhibitor JNJ-7706621 and Src inhibitor PP1 being the most potent against the pancreatic cancer cell line Panc 04.03.

CONCLUSIONS

CancerOmicsNet is a promising AI-based platform to help guide the development of new approaches in precision oncology involving a variety of tumor types and therapeutics.

Up-regulation of the PI3K/AKT and RHO/RAC/PAK signalling pathways in CHK1 inhibitor resistant Eµ-Myc lymphoma cells

The development of resistance and the activation of bypass pathway signalling represents a major problem for the clinical application of protein kinase inhibitors. While investigating the effect of either a c-Rel deletion or RelAT505A phosphosite knockin on the Eµ-Myc mouse model of B-cell lymphoma, we discovered that both NF-κB subunit mutations resulted in CHK1 inhibitor resistance, arising from either loss or alteration of CHK1 activity, respectively. However, since Eµ-Myc lymphomas depend on CHK1 activity to cope with high levels of DNA replication stress and consequent genomic instability, it was not clear how these mutant NF-κB subunit lymphomas were able to survive. To understand these survival mechanisms and to identify potential compensatory bypass signalling pathways in these lymphomas, we applied a multi-omics strategy. With c-Rel-/- Eµ-Myc lymphomas we observed high levels of Phosphatidyl-inositol 3-kinase (PI3K) and AKT pathway activation. Moreover, treatment with the PI3K inhibitor Pictilisib (GDC-0941) selectively inhibited the growth of reimplanted c-Rel-/- and RelAT505A, but not wild type (WT) Eµ-Myc lymphomas. We also observed up-regulation of a RHO/RAC pathway gene expression signature in both Eµ-Myc NF-κB subunit mutation models. Further investigation demonstrated activation of the RHO/RAC effector p21-activated kinase (PAK) 2. Here, the PAK inhibitor, PF-3758309 successfully overcame resistance of RelAT505A but not WT lymphomas. These findings demonstrate that up-regulation of multiple bypass pathways occurs in CHK1 inhibitor resistant Eµ-Myc lymphomas. Consequently, drugs targeting these pathways could potentially be used as either second line or combinatorial therapies to aid the successful clinical application of CHK1 inhibitors.

Discovery of 2-Methyl-2-(4-(2-methyl-8-(1H-pyrrolo[2,3-b]pyridin-6-yl)-1H-naphtho[1,2-d]imidazol-1-yl)phenyl)propanenitrile as a Novel PI3K/mTOR Inhibitor with Enhanced Antitumor Efficacy In Vitro and In Vivo

PI3K/Akt/mTOR signaling pathway is a validated drug target for cancer treatment that plays a critical role in controlling tumor growth, proliferation, and apoptosis. However, no FDA-approved PI3K/mTOR dual inhibitor exists. Thus, a candidate with a better curative effect and lower toxicity is still urgently needed. Herein, we design, synthesize, and evaluate compounds belonging to a novel series of 2-methyl-1H-imidazo[4,5-c]quinoline scaffold derivatives as PI3K/mTOR dual inhibitors. Among them, compound 8o was identified as a novel candidate with excellent kinase selectivity. It manifested remarkable antiproliferative activities against SW620 and HeLa cells. Western blot and immunohistochemical analysis results proved that 8o could regulate the PI3K/AKT/mTOR signaling pathway by inhibiting the phosphorylation of AKT and S6 proteins. Additionally, 8o presented a favorable pharmacokinetic property (oral bioavailability of 76.8%) and significant antitumor efficacy in vivo without obvious toxicity. Collectively, these results indicated that 8o is a promising agent for cancer treatment and merits further development.

Targeting PI3K/AKT/mTOR Signaling Pathway in Pancreatic Cancer: From Molecular to Clinical Aspects

Although pancreatic cancer (PC) was considered in the past an orphan cancer type due to its low incidence, it may become in the future one of the leading causes of cancer death. Pancreatic ductal adenocarcinoma (PDAC) is the most frequent type of PC, being a highly aggressive malignancy and having a 5-year survival rate of less than 10%. Non-modifiable (family history, age, genetic susceptibility) and modifiable (smoking, alcohol, acute and chronic pancreatitis, diabetes mellitus, intestinal microbiota) risk factors are involved in PC pathogenesis. Chronic inflammation induced by various factors plays crucial roles in PC development from initiation to metastasis. In multiple malignant conditions such as PC, cytokines, chemokines, and growth factors activate the class I phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) (PI3K/AKT/mTOR) signaling pathway, which plays key roles in cell growth, survival, proliferation, metabolism, and motility. Currently, mTOR, AKT, and PI3K inhibitors are used in clinical studies. Moreover, PI3K/mTOR dual inhibitors are being tested in vitro and in vivo with promising results for PC patients. The main aim of this review is to present PC incidence, risk factors, tumor microenvironment development, and PI3K/AKT/mTOR dysregulation and inhibitors used in clinical, in vivo, and in vitro studies.

GDC-0941 activates integrin linked kinase (ILK) expression to cause resistance to GDC-0941 in breast cancer by the tumor necrosis factor (TNF)-α signaling pathway

Breast cancer is characterized by high morbidity and mortality. GDC-0941 is a PI3K inhibitor with oncogenic effects in breast cancer. However, certain breast cancer cells are insensitive to GDC-0941. Hence, the mechanism of GDC-0941 in breast cancer resistance was investigated in this study. Breast cancer cell lines BT-474, MCF7, Hs-578-T, MDA-MB-231, MDA-MB-453, and MDA-MB-468 were cultured in different medium and then treated with 100 or 500 nM GDC-0941, 100 nM OSU-T315, or TNF-α antibody. Moreover, ILK and shILK were transfected into cells. The half maximal inhibitory concentrations (IC50) for GDC-0941 were detected using CCK-8 assay. The levels of ILK, AKT, PDK1, S6, and p70S6K expression were detected using western blotting and qPCR. In addition, the mouse model of breast cancer was constructed to measure the tumor size, volume, and weight. The results showed that GDC-0941 decreased cell survival rate, downregulated the phosphorylation of AKT, S6, and p70S6K, and promoted the expression of ILK, while it had little effect on PDK1 expression. GDC-0941 inhibited the increases in p-AKT, p-S6, and p-p70S6K caused by ILK overexpression and promoted ILK knockdown-induced reduction of p-AKT, p-S6, and p-p70S6K. In addition, the combination of OSU-T315 and GDC-0941 decreased p-AKT, p-S6, and p-p70S6K level, tumor volume, and tumor weight. GDC-0941 promoted ILK expression by upregulating TNF-α level. Taken together, GDC-0941 increased ILK level by upregulating TNF-α, thus affecting AKT expression and the sensitivity of breast cancer cells to GDC-0941.

Patient-specific Boolean models of signalling networks guide personalised treatments

Prostate cancer is the second most occurring cancer in men worldwide. To better understand the mechanisms of tumorigenesis and possible treatment responses, we developed a mathematical model of prostate cancer which considers the major signalling pathways known to be deregulated. We personalised this Boolean model to molecular data to reflect the heterogeneity and specific response to perturbations of cancer patients. A total of 488 prostate samples were used to build patient-specific models and compared to available clinical data. Additionally, eight prostate cell line-specific models were built to validate our approach with dose-response data of several drugs. The effects of single and combined drugs were tested in these models under different growth conditions. We identified 15 actionable points of interventions in one cell line-specific model whose inactivation hinders tumorigenesis. To validate these results, we tested nine small molecule inhibitors of five of those putative targets and found a dose-dependent effect on four of them, notably those targeting HSP90 and PI3K. These results highlight the predictive power of our personalised Boolean models and illustrate how they can be used for precision oncology.

Recent Advances of PI3 Kinase Inhibitors: Structure Anticancer Activity Relationship Studies

Phosphatidyl-inositol-3-kinase (PI3K) has emerged as a potential therapeutic target for the development of novel anticancer drugs. The dysregulation of PI3K has been associated with many human malignancies such as breast, colon, endometrial, brain, and prostate cancers. The PI3K kinases in their different isoforms namely α, β, δ, and γ, encode PIK3CA, PIK3CB, PIK3CD, and PIK3CG genes. Specific gene mutation or overexpression of the protein is responsible for therapeutic failure of current therapeutics. Recently, various PI3K signaling pathway inhibitors have been identified which showed promising therapeutic results by acting on specific isoforms of the kinase too. Several inhibitors containing medicinally privileged scaffolds like oxadiazole, pyrrolotriazine, quinazoline, quinazolinone, quinazoline-chalcone hybrids, quinazoline-sulfonamide, pyrazolochalcone, quinolone hydroxamic acid, benzofuropyridinone, imidazopyridine, benzoxazines, dibenzoxanthene, indoloderivatives, benzimidazole, and benzothiazine derivatives have been developed to target PI3K pathway and/or a specific isoform. The PI3K inhibitors which are under clinical trial studies include GDC-0032, INK1117 for PI3K-α, and AZD8186 for PI3K-β. This review primarily focuses on the structural insights and structure anticancer activity relationship studies of recent PI3K inhibitors including their clinical stages of development and therapeutic values.

Wnt and PI3K/Akt/mTOR Survival Pathways as Therapeutic Targets in Glioblastoma

Glioblastoma (GBM) is a devastating type of brain tumor, and current therapeutic treatments, including surgery, chemotherapy, and radiation, are palliative at best. The design of effective and targeted chemotherapeutic strategies for the treatment of GBM require a thorough analysis of specific signaling pathways to identify those serving as drivers of GBM progression and invasion. The Wnt/β-catenin and PI3K/Akt/mTOR (PAM) signaling pathways are key regulators of important biological functions that include cell proliferation, epithelial–mesenchymal transition (EMT), metabolism, and angiogenesis. Targeting specific regulatory components of the Wnt/β-catenin and PAM pathways has the potential to disrupt critical brain tumor cell functions to achieve critical advancements in alternative GBM treatment strategies to enhance the survival rate of GBM patients. In this review, we emphasize the importance of the Wnt/β-catenin and PAM pathways for GBM invasion into brain tissue and explore their potential as therapeutic targets.

Ribosomal Protein S6: A Potential Therapeutic Target against Cancer?

Ribosomal protein S6 (RPS6) is a component of the 40S small ribosomal subunit and participates in the control of mRNA translation. Additionally, phospho (p)-RPS6 has been recognized as a surrogate marker for the activated PI3K/AKT/mTORC1 pathway, which occurs in many cancer types. However, downstream mechanisms regulated by RPS6 or p-RPS remains elusive, and the therapeutic implication of RPS6 is underappreciated despite an approximately half a century history of research on this protein. In addition, substantial evidence from RPS6 knockdown experiments suggests the potential role of RPS6 in maintaining cancer cell proliferation. This motivates us to investigate the current knowledge of RPS6 functions in cancer. In this review article, we reviewed the current information about the transcriptional regulation, upstream regulators, and extra-ribosomal roles of RPS6, with a focus on its involvement in cancer. We also discussed the therapeutic potential of RPS6 in cancer.

Narciclasine induces autophagy-mediated apoptosis in gastric cancer cells through the Akt/mTOR signaling pathway

Background

Gastric cancer is a common gastrointestinal cancer and currently has the third-highest mortality rate. Research shows that the natural compound narciclasine has a variety of biological activities. The present study aimed to investigate the effect of narciclasine on gastric cancer cells and its molecular mechanisms and determine whether this compound could be a novel therapy for gastric cancer.

Methods

MTT and clone assays were employed to detect the proliferation of gastric cancer cells. The cell apoptosis was detected by flow cytometry. The formation of autophagosomes and autophagosomal lysosomes was observed by transmission electron microscopy and laser confocal scanning microscopy. Western blotting was used to detect the expression of apoptosis, autophagy and Akt/mTOR pathway-related proteins.

Results

In this study, we found that narciclasine could inhibit the proliferation of gastric cancer cells and promote apoptosis in gastric cancer cells. Further experiments showed that narciclasine promoted the levels of autophagy proteins LC3-II, Atg-5 and Beclin-1, reduced the expression of the autophagy transporter p62, and increased autophagic flux. By using the autophagy inhibitors 3-MA and CQ, it was shown that narciclasine could induce autophagy-mediated apoptosis in gastric cancer cells. Finally, we found that narciclasine had no significant effects on the total content of Akt and mTOR in gastric cancer cells, and it involved autophagy in gastric cancer cells by reducing the phosphorylation level of p-Akt and p-mTOR.

Conclusions

Narciclasine can induce autophagy-dependent apoptosis in gastric cancer cells by inhibiting the phosphorylation level of Akt/mTOR and thus reduce the proliferation of gastric cancer cells.

Mapping of mTOR drug targets: Featured platforms for anti-cancer drug discovery

The mammalian/mechanistic target of rapamycin (mTOR) is a regulatory protein kinase involved in cell growth and proliferation. mTOR is usually assembled in two different complexes with different regulatory mechanisms, mTOR complex 1 (mTORC1) and mTORC2, which are involved in different functions such as cell proliferation and cytoskeleton assembly, respectively. In cancer cells, mTOR is hyperactivated in response to metabolic alterations and/or oncogenic signals to overcome the stressful microenvironments. Therefore, recent research progress for mTOR inhibition involves a variety of compounds that have been developed to disturb the metabolic processes of cancer cells through mTOR inhibition. In addition to competitive or allosteric inhibition, a new inhibition strategy that emerged mTOR complexes destabilization has recently been a concern. Here, we review the history of mTOR and its inhibition, along with the timeline of the mTOR inhibitors. We also introduce prospective drug targets to inhibit mTOR by disrupting the complexation of the components with peptides and small molecules.

Abbreviated Profile of Drugs (APOD): modeling drug safety profiles to prioritize investigational COVID-19 treatments

Safe and effective oral formulation of a drug, that is easy to store, transport, and administer, is imperative to reach the masses including those without adequate facilities and resources, in order to combat globally transmitted coronavirus disease 2019 (COVID-19). In this decision analytic modeling study, the safety of investigational COVID-19 drugs in clinical trials was assessed using the Abbreviated Profile of Drugs (APOD) methodology. The method was extensively tested for various unbiased datasets based on different criteria such as drugs recalled worldwide for failing to meet safety standards, organ-specific toxicities, cytochrome P450 inhibitors, and Food and Drug Administration (FDA) approved drugs with remarkable successes. Experimental validation of the predictions made by APOD were demonstrated by comparison with a progression of multiparametric optimization of a series of cancer drugs that led to a potent drug (GDC-0941) which went into the clinical development. The drugs were classified into three categories of safety profiles: strong, moderate and weak. A total of 3556 drugs available in public databases were examined. According to the results, drugs with strong safety profiles included molnupiravir (EIDD-2801), moderate safety profiles included dexamethasone, and weak safety profiles included lopinavir. In this analysis, the physicochemical-pharmacokinetic APOD fingerprint was associated with the drug safety profile of withdrawn, approved, as well as drugs in clinical trials and the APOD method facilitated decision-making and prioritization of the investigational treatments.

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Drugs with only strong and moderate safety profiles can be repurposed for COVID-19 or any other disease targets.

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The existing effective drugs with weak safety profiles can be modified into effective drugs with moderate/strong profiles.

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Unification, uniformity, and integration of drug properties by the APOD method represents an advancement in drug discovery.

New thieno[3,2-d]pyrimidine-based derivatives: Design, synthesis and biological evaluation as antiproliferative agents, EGFR and ARO inhibitors inducing apoptosis in breast cancer cells

An array of newly synthesized thieno[3,2-d]pyrimidine-based derivatives and thienotriazolopyrimidines hybridized with some pharmacophoric anticancer fragments were designed, synthesized and assessed for their in vitro antiproliferative activity against MCF-7 and MDA-MB-231 breast cancer cell lines using erlotinib and pictilisib as reference standards in the MTT assay. In general, many compounds were endowed with considerable antiproliferative activity (IC₅₀ = 0.43-1.31 µM). Some of the tested compounds, namely 3c, 5b, 5c, 9d, 10, 11b and 13 displayed remarkable antiproliferative activity against both cell lines. Meanwhile, compounds 2c-e, 3b, 4a, 5a, 9c and 15b showed noticeable selectivity against MCF-7 cells while compounds 2b, 3a, 4b, 6a-c, 7, 8, 9b and 12 exhibited considerable selectivity against MDA-MB-231 cells. Further mechanistic evidences for their anticancer activities were provided by screening the most potent compounds against MCF-7 and/or MDA-MB-231 cells for EGFR and ARO inhibitory activities using erlotinib and letrozole as reference standards respectively. Results proved that, in general, tested compounds were better EGFRIs than ARIs. In addition, significant overexpression in caspase-9 level in treated MCF-7 breast cell line samples was observed for all tested compounds with the 4-fluorophenylhydrazone derivative 2d exhibiting the highest activation. In treated MDA-MB-231 breast cell line samples, 11b was found to highly induce caspase-9 level thereby inducing apoptosis. Cell cycle analysis and Annexin V-FITC/PI assay were also assessed for active compounds where results indicated that all tested compounds induced preG1 apoptosis and cell cycle arrest at G2/M phase. Compound 9d, as an inhibitor of ARO, was observed to downregulate the downstream signaling proteins HSP27 and p-ERK in MCF-7 cells. Furthermore, compound 11b downregulated EGFR expression as well as the downstream signaling protein p-AKT. Docking experiments on EGFR and ARO enzymes supported their in vitro results. Thus, the thienotriazolopyrimidines 11b and 12 showing good EGFR inhibition and the thieno[3,2-d]-pyrimidine derivatives 3b and 9d, eliciting the best ARO inhibition activity, can be considered as new candidates as anti-breast cancer agents that necessitate further development.

Pancreatic cancer intrinsic PI3Kα activity accelerates metastasis and rewires macrophage component

Pancreatic ductal adenocarcinoma (PDAC) patients frequently suffer from undetected micro-metastatic disease. This clinical situation would greatly benefit from additional investigation. Therefore, we set out to identify key signalling events that drive metastatic evolution from the pancreas. We searched for a gene signature that discriminate localised PDAC from confirmed metastatic PDAC and devised a preclinical protocol using circulating cell-free DNA (cfDNA) as an early biomarker of micro-metastatic disease to validate the identification of key signalling events. An unbiased approach identified, amongst actionable markers of disease progression, the PI3K pathway and a distinctive PI3Kα activation signature as predictive of PDAC aggressiveness and prognosis. Pharmacological or tumour-restricted genetic PI3Kα-selective inhibition prevented macro-metastatic evolution by hindering tumoural cell migratory behaviour independently of genetic alterations. We found that PI3Kα inhibition altered the quantity and the species composition of the produced lipid second messenger PIP3 , with a selective decrease of C36:2 PI-3,4,5-P3 . Tumoural PI3Kα inactivation prevented the accumulation of pro-tumoural CD206-positive macrophages in the tumour-adjacent tissue. Tumour cell-intrinsic PI3Kα promotes pro-metastatic features that could be pharmacologically targeted to delay macro-metastatic evolution.

Absorption, metabolism and excretion of pictilisib, a potent pan-class I phosphatidylinositol-3-Kinase (PI3K) inhibitor, in rats, dogs, and humans

The absorption, metabolism and excretion of pictilisib, a selective small molecule inhibitor of class 1 A phosphoinositide 3-kinase (PI3K), was characterized following a single oral administration of [¹⁴C]pictilisib in rats, dogs and humans at the target doses of 30 mg/kg, 5 mg/kg and 60 mg, respectively.Pictilisib was rapidly absorbed with T_max less than 2 h across species. In systemic circulation, pictilisib represented the predominant total radioactivity greater than 86.6% in all species.Total pictilisib and related radioactivity was recovered from urine and faeces in rats, dogs, and human at 98%, 80% and 95%, respectively, with less than 2% excreted in urine and the rest excreted into faeces.In rat and dog, more than 40% of drug-related radioactivity was excreted into the bile suggesting biliary excretion was the major route of excretion. Unchanged pictilisib was a minor component in rat and dog bile. The major metabolite in bile was O-glucuronide of oxidation on indazole moiety (M20, 21% of the dose) in rats and an oxidative piperazinyl ring-opened metabolite M7 (10.8% of the dose) in dogs.Oxidative glutathione (GSH) conjugates (M18, M19) were novel metabolites detected in rat bile, suggesting the potential generation of reactive intermediates from pictilisib. The structure of M18 was further confirmed by NMR to be a N-hydroxylated and GSH conjugated metabolite on the moiety of the indazole ring.

Targeting RTK-PI3K-mTOR Axis in Gliomas: An Update

Gliomas are the most common and challenging malignancies of the central nervous system (CNS), due to their infiltrative nature, tendency to recurrence, and poor response to treatments. Indeed, despite the advances in neurosurgical techniques and in radiation therapy, the modest effects of therapy are still challenging. Moreover, tumor recurrence is associated with the onset of therapy resistance; it is therefore critical to identify effective and well-tolerated pharmacological approaches capable of inducing durable responses in the appropriate patient groups. Molecular alterations of the RTK/PI3K/Akt/mTOR signaling pathway are typical hallmarks of glioma, and several clinical trials targeting one or more players of this axis have been launched, showing disappointing results so far, due to the scarce BBB permeability of certain compounds or to the occurrence of resistance/tolerance mechanisms. However, as RTK/PI3K/mTOR is one of the pivotal pathways regulating cell growth and survival in cancer biology, targeting still remains a strong rationale for developing strategies against gliomas. Future rigorous clinical studies, aimed at addressing the tumor heterogeneity, the interaction with the microenvironment, as well as diverse posology adjustments, are needed-which might unravel the therapeutic efficacy and response prediction of an RTK/PI3K/mTOR-based approach.

Construction and Validation of an Immune Infiltration-Related Gene Signature for the Prediction of Prognosis and Therapeutic Response in Breast Cancer

Breast cancer patients show significant heterogeneity in overall survival. Current assessment models are insufficient to accurately predict patient prognosis, and models for predicting treatment response are lacking. We evaluated the relationship between various immune cells and breast cancer and confirmed the association between immune infiltration and breast cancer progression. Different bioinformatics and statistical approaches were combined to construct a robust immune infiltration-related gene signature for predicting patient prognosis and responses to immunotherapy and chemotherapy. Our research found that a higher immune infiltration-related risk score (IRS) indicates that the patient has a worse prognosis and is not very sensitive to immunotherapy. In addition, a new nomogram was constructed based on the gene signature and clinicopathological features to improve the risk stratification and quantify the risk assessment of individual patients. Our study might contribute to the optimization of the risk stratification for survival and the personalized management of breast cancer.

Research update on the anticancer effects of buparlisib

Buparlisib is a highly efficient and selective PI3K inhibitor and a member of the 2,6-dimorpholinopyrimidine-derived family of compounds. It selectively inhibits four isomers of PI3K, PI3Kα, PI3Kβ, PI3Kγ and PI3Kδ, by competitively binding the lipid kinase domain on adenosine 5'-triphosphate (ATP), and serves an important role in inhibiting proliferation, promoting apoptosis and blocking angiogenesis, predominantly by antagonizing the PI3K/AKT pathway. Buparlisib has been confirmed to have a clinical effect in patients with solid tumors and hematological malignancies. A global, phase II clinical trial with buparlisib and paclitaxel in head and neck squamous cell carcinoma has now been completed, with a manageable safety profile. Buparlisib currently has fast-track status with the United States Food and Drug Administration. The present review examined the biochemical structure, pharmacokinetic characteristics, preclinical data and ongoing clinical studies of buparlisib. The various mechanisms of influence of buparlisib in tumors, particularly in preclinical research, were summarized, providing a theoretical basis and direction for basic research on and clinical treatment with buparlisib.

Applications of liquid biopsy in the Pharmacological Audit Trail for anticancer drug development

Anticancer drug development is a costly and protracted activity, and failure at late phases of clinical testing is common. We have previously proposed the Pharmacological Audit Trail (PhAT) intended to improve the efficiency of drug development, with a focus on the use of tumour tissue-based biomarkers. Blood-based 'liquid biopsy' approaches, such as targeted or whole-genome sequencing studies of plasma circulating cell-free tumour DNA (ctDNA) and circulating tumour cells (CTCs), are of increasing relevance to this drug development paradigm. Liquid biopsy assays can provide quantitative and qualitative data on prognostic, predictive, pharmacodynamic and clinical response biomarkers, and can also enable the characterization of disease evolution and resistance mechanisms. In this Perspective, we examine the promise of integrating liquid biopsy analyses into the PhAT, focusing on the current evidence, advances, limitations and challenges. We emphasize the continued importance of analytical validation and clinical qualification of circulating tumour biomarkers through prospective clinical trials.

Phosphoinositide 3-Kinase (PI3K) Reactive Oxygen Species (ROS)-Activated Prodrug in Combination with Anthracycline Impairs PI3K Signaling, Increases DNA Damage Response and Reduces Breast Cancer Cell Growth

RIDR-PI-103 is a novel reactive oxygen species (ROS)-induced drug release prodrug with a self-cyclizing moiety linked to a pan-PI3K inhibitor (PI-103). Under high ROS, PI-103 is released in a controlled manner to inhibit PI3K. The efficacy and bioavailability of RIDR-PI-103 in breast cancer remains unexplored. Cell viability of RIDR-PI-103 was assessed on breast cancer cells (MDA-MB-231, MDA-MB-361 and MDA-MB-453), non-tumorigenic MCF10A and fibroblasts. Matrigel colony formation, cell proliferation and migration assays examined the migratory properties of breast cancers upon treatment with RIDR-PI-103 and doxorubicin. Western blots determined the effect of doxorubicin ± RIDR-PI-103 on AKT activation and DNA damage response. Pharmacokinetic (PK) studies using C57BL/6J mice determined systemic exposure (plasma concentrations and overall area under the curve) and T1/2 of RIDR-PI-103. MDA-MB-453, MDA-MB-231 and MDA-MB-361 cells were sensitive to RIDR-PI-103 vs. MCF10A and normal fibroblast. Combination of doxorubicin and RIDR-PI-103 suppressed cancer cell growth and proliferation. Doxorubicin with RIDR-PI-103 inhibited p-AktS473, upregulated p-CHK1/2 and p-P53. PK studies showed that ~200 ng/mL (0.43 µM) RIDR-PI-103 is achievable in mice plasma with an initial dose of 20 mg/kg and a 10 h T1/2. (4) The prodrug RIDR-PI-103 could be a potential therapeutic for treatment of breast cancer patients.

PI3K inhibition as a novel therapeutic strategy for neoadjuvant chemoradiotherapy resistant oesophageal adenocarcinoma

OBJECTIVE

Neoadjuvant chemoradiotherapy (neo-CRT) prior to surgery is the standard of care for oesophageal adenocarcinoma (OAC) patients. Unfortunately, most patients fail to respond to treatment. MiR-187 was previously shown to be downregulated in neo-CRT non-responders, whist in vitro miR-187 overexpression enhanced radiosensitivity and upregulated PTEN. This study evaluates the role of miR-187 and downstream PI3K signalling in radiation response in OAC.

METHODS

The effect of miR-187 overexpression on downstream PI3K signalling was evaluated in OAC cell lines by qPCR and Western blotting. PTEN expression was analysed in OAC pre-treatment biopsies of neo-CRT responders and non-responders. Pharmacological inhibition of PI3K using GDC-0941 was evaluated in combination with radiotherapy in two-dimensional and three-dimensional OAC models in vitro and as a single agent in vivo. Radiation response in vitro was assessed via clonogenic assay.

RESULTS

PTEN expression was significantly decreased in neo-CRT non-responders. MiR-187 overexpression significantly upregulated PTEN expression and inhibited downstream PI3K signalling in vitro. GDC-0941 significantly reduced viability and enhanced radiation response in vitro and led to tumour growth inhibition as a single agent in vivo.

CONCLUSION

Targeting of PI3K signalling is a promising therapeutic strategy for OAC patients who have repressed miR-187 expression and do not respond to conventional neo-CRT.

ADVANCES IN KNOWLEDGE

This is the first study evaluating the effect of PI3K inhibition on radiosensitivity in OAC, with a particular focus on patients that do not respond to neo-CRT. We have shown for the first time that targeting of PI3K signalling is a promising alternative therapeutic strategy for OAC patients who do not respond to conventional neo-CRT.

Dual Kinase Targeting in Leukemia

Pharmacological cancer therapy is often based on the concurrent inhibition of different survival pathways to improve treatment outcomes and to reduce the risk of relapses. While this strategy is traditionally pursued only through the co-administration of several drugs, the recent development of multi-targeting drugs (i.e., compounds intrinsically able to simultaneously target several macromolecules involved in cancer onset) has had a dramatic impact on cancer treatment. This review focuses on the most recent developments in dual-kinase inhibitors used in acute myeloid leukemia (AML), chronic myelogenous leukemia (CML), and lymphoid tumors, giving details on preclinical studies as well as ongoing clinical trials. A brief overview of dual-targeting inhibitors (kinase/histone deacetylase (HDAC) and kinase/tubulin polymerization inhibitors) applied to leukemia is also given. Finally, the very recently developed Proteolysis Targeting Chimeras (PROTAC)-based kinase inhibitors are presented.

Genomic and pathological heterogeneity in clinically diagnosed small cell lung cancer in never/light smokers identifies therapeutically targetable alterations

Small-cell lung cancer (SCLC) occurs infrequently in never/former light smokers. We sought to study this rare clinical subset through next-generation sequencing (NGS) and by characterizing a representative patient-derived model. We performed targeted NGS, as well as comprehensive pathological evaluation, in 11 never/former light smokers with clinically diagnosed SCLC. We established a patient-derived model from one such patient (DFCI168) harboring an NRAS^Q61K mutation and characterized the sensitivity of this model to MEK and TORC1/2 inhibitors. Despite the clinical diagnosis of SCLC, the majority (8/11) of cases were either of nonpulmonary origin or of mixed histology and included atypical carcinoid (n = 1), mixed non-small-cell lung carcinoma and SCLC (n = 4), unspecified poorly differentiated carcinoma (n = 1), or small-cell carcinoma from different origins (n = 2). RB1 and TP53 mutations were found in four and five cases, respectively. Predicted driver mutations were detected in EGFR (n = 2), NRAS (n = 1), KRAS (n = 1), BRCA1 (n = 1), and ATM (n = 1), and one case harbored a TMPRSS2-ERG fusion. DFCI168 (NRAS^Q61K ) exhibited marked sensitivity to MEK inhibitors in vitro and in vivo. The combination of MEK and mTORC1/2 inhibitors synergized to prevent compensatory mTOR activation, resulting in prolonged growth inhibition in this model and in three other NRAS mutant lung cancer cell lines. SCLC in never/former light smokers is rare and is potentially a distinct disease entity comprised of oncogenic driver mutation-harboring carcinomas morphologically and/or clinically mimicking SCLC. Comprehensive pathologic review integrated with genomic profiling is critical in refining the diagnosis and in identifying potential therapeutic options.

Inhibition of class I PI3K enhances chaperone-mediated autophagy

Chaperone-mediated autophagy (CMA) is the most selective form of lysosomal proteolysis, where individual peptides, recognized by a consensus motif, are translocated directly across the lysosomal membrane. CMA regulates the abundance of many disease-related proteins, with causative roles in neoplasia, neurodegeneration, hepatosteatosis, and other pathologies relevant to human health and aging. At the lysosomal membrane, CMA is inhibited by Akt-dependent phosphorylation of the CMA regulator GFAP. The INS-PI3K-PDPK1 pathway regulates Akt, but its role in CMA is unclear. Here, we report that inhibition of class I PI3K or PDPK1 activates CMA. In contrast, selective inhibition of class III PI3Ks does not activate CMA. Isolated liver lysosomes from mice treated with either of two orally bioavailable class I PI3K inhibitors, pictilisib or buparlisib, display elevated CMA activity, and decreased phosphorylation of lysosomal GFAP, with no change in macroautophagy. The findings of this study represent an important first step in repurposing class I PI3K inhibitors to modulate CMA in vivo.

Identification of a potent and selective phosphatidylinositol 3-kinase δ inhibitor for the treatment of non-Hodgkin's lymphoma

PI3Kδ has proved to be an effective target for anti-lymphoma drugs. However, the application of current approved PI3Kδ inhibitors has been greatly limited due to their specific immune-mediated toxicity and increased risk of infection, it is necessary to develop more PI3Kδ inhibitors with new scaffold. In this study, SAR study with respect to piperazinone-containing purine derivatives led to the discovery of a potent and selective PI3Kδ inhibitor, 4-(cyclobutanecarbonyl)-1-((2-(2-ethyl-1H-benzo[d]imidazol-1-yl)-9-methyl-6-morpholino-9H-purin-8-yl)methyl)piperazin-2-one (WNY1613). WNY1613 exhibits good antiproliferative activity against a panel of non-Hodgkin's lymphoma (NHL) cell lines by inducing cancer cell apoptosis and inhibiting the phosphorylation of PI3K and MAPK downstream components. In addition, it can also prevent the tumor growth in both SU-DHL-6 and JEKO-1 xenograft models without observable toxicity. WNY1613 thus could be developed as a promising candidate for the treatment of NHL after subsequent extensive pharmacodynamics and pharmacokinetics investigation.

Dual inhibitors of histone deacetylases and other cancer-related targets: A pharmacological perspective

Epigenetic enzymes histone deacetylases (HDACs) are clinically validated anticancer drug targets which have been studied intensively in the past few decades. Although several drugs have been approved in this field, they are still limited to a subset of hematological malignancies (in particular T-cell lymphomas), with therapeutic potential not fully realized and the drug-resistance occurred after a certain period of use. To maximize the therapeutic potential of these classes of anticancer drugs, and to extend their application to solid tumors, numerous combination therapies containing an HDACi and an anticancer agent from other mechanisms are currently ongoing in clinical trials. Recently, dual targeting strategy comprising the HDACs component has emerged as an alternative approach for combination therapies. In this perspective, we intend to gather all HDACs-containing dual inhibitors related to cancer therapy published in literature since 2015, classify them into five categories based on targets' biological functions, and discuss the rationale why dual acting agents should work better than combinatorial therapies using two separate drugs. The article discusses the pharmacological aspects of these dual inhibitors, including in vitro biological activities, pharmacokinetic studies, in vivo efficacy studies, as well as available clinical trials. The review of the current status and advances should provide better analysis for future opportunities and challenges of this field.

A mass spectrometry-based proteome map of drug action in lung cancer cell lines

Mass spectrometry-based discovery proteomics is an essential tool for the proximal readout of cellular drug action. Here, we apply a robust proteomic workflow to rapidly profile the proteomes of five lung cancer cell lines in response to more than 50 drugs. Integration of millions of quantitative protein-drug associations substantially improved the mechanism of action (MoA) deconvolution of single compounds. For example, MoA specificity increased after removal of proteins that frequently responded to drugs and the aggregation of proteome changes across cell lines resolved compound effects on proteostasis. We leveraged these findings to demonstrate efficient target identification of chemical protein degraders. Aggregating drug response across cell lines also revealed that one-quarter of compounds modulated the abundance of one of their known protein targets. Finally, the proteomic data led us to discover that inhibition of mitochondrial function is an off-target mechanism of the MAP2K1/2 inhibitor PD184352 and that the ALK inhibitor ceritinib modulates autophagy.

A PI3K- and GTPase-independent Rac1-mTOR mechanism mediates MET-driven anchorage-independent cell growth but not migration

Receptor tyrosine kinases (RTKs) are often overexpressed or mutated in cancers and drive tumor growth and metastasis. In the current model of RTK signaling, including that of MET, downstream phosphatidylinositol 3-kinase (PI3K) mediates both cell proliferation and cell migration, whereas the small guanosine triphosphatase (GTPase) Rac1 mediates cell migration. However, in cultured NIH3T3 and glioblastoma cells, we found that class I PI3K mediated oncogenic MET-induced cell migration but not anchorage-independent growth. In contrast, Rac1 regulated both processes in distinct ways. Downstream of PI3K, Rac1 mediated cell migration through its GTPase activity, whereas independently of PI3K, Rac1 mediated anchorage-independent growth in a GTPase-independent manner through an adaptor function. Through its RKR motif, Rac1 formed a complex with the kinase mTOR to promote its translocation to the plasma membrane, where its activity promoted anchorage-independent growth of the cell cultures. Inhibiting mTOR with rapamycin suppressed the growth of subcutaneous MET-mutant cell grafts in mice, including that of MET inhibitor-resistant cells. These findings reveal a GTPase-independent role for Rac1 in mediating a PI3K-independent MET-to-mTOR pathway and suggest alternative or combined strategies that might overcome resistance to RTK inhibitors in patients with cancer.

GDC-0941 and CXCL8 (3-72) K11R/G31P combination therapy confers enhanced efficacy against breast cancer

Aim: Herein is presented the combined effect of PI3K inhibitor (GDC-0941) and CXCR1/2 analogue (G31P) in breast cancer. Materials & methods: Breast cancer cell lines and xenograft model were employed to test the efficacy of the combination therapy. Results: GDC-0941+G31P treatment substantially inhibited multiplication of all the breast cancer cell lines used in this study (BT474, HCC1954 and 4T1). Even though single therapies caused a meaningful S-phase cell cycle arrest, the inhibition effect was more potent with the combined treatment. Similarly, enhanced apoptosis accompanied GDC-0941+G31P treatment. Furthermore, the migration ability of the breast cancer cell lines were significantly curtailed by the combination therapy compared with the single treatments. Conclusion: The findings suggest that combination treatment involving PI3K inhibitor and CXCR1/2 analogue (G31P) could be a potent therapeutic option for breast cancer treatment.

Novel HSP90-PI3K Dual Inhibitor Suppresses Melanoma Cell Proliferation by Interfering with HSP90-EGFR Interaction and Downstream Signaling Pathways

Melanoma is the deadliest form of skin cancer, and its incidence has continuously increased over the past 20 years. Therefore, the discovery of a novel targeted therapeutic strategy for melanoma is urgently needed. In our study, MTT-based cell proliferation assay, cell cycle, and apoptosis assays through flow cytometry, protein immunoblotting, protein immunoprecipitation, designing of melanoma xenograft models, and immunohistochemical/immunofluorescent assays were carried out to determine the detailed molecular mechanisms of a novel HSP90-PI3K dual inhibitor. Our compound, named DHP1808, was found to suppress A375 cell proliferation through apoptosis induction by activating the Fas/FasL signaling pathway; it also induced cell-cycle arrest and inhibited the cell migration and invasion of A375 cells by interfering with Hsp90-EGFR interactions and downstream signaling pathways. Our results indicate that DHP1808 could be a promising lead compound for the Hsp90/PI3K dual inhibitor.

Synthesis and biological evaluation of 6-phenylpurine linked hydroxamates as novel histone deacetylase inhibitors

A series of 6-phenylpurine based hydroxamates have been designed, synthesized and evaluated. Compound 3b and its analogs are potent histone deacetylase (HDAC) but weak PI3K/mTOR inhibitors. These compounds demonstrated broad anti-cancer activities against 38 cancer cell lines with leukemia, lymphoma, and the majority of liver cancer cell lines exhibiting the most sensitivity towards these compounds. Compound 3b demonstrated modulation of HDAC targets in vitro in a dose-dependent manner. It has good in vitro ADME profile that translated into a greatly improved pharmacokinetic profile. 3b also demonstrated modulation of HDACs in tumors in a PC-3 xenograft model. It was further evaluated in combination therapies in vitro. It exhibited additive or synergistic growth inhibition effect in HepG2 cells when combined with a number of approved drugs such as sorafenib, sunitinib, and erlotinib. Hence, 3b has the potential to be combined with the above to treat advanced liver cancer. As such, current data warrant further evaluation, optimization, and subsequent in vivo validation of the potential combination therapies.

Synthesis and Evaluation of Novel 2H-Benzo[e]-[1,2,4]thiadiazine 1,1-Dioxide Derivatives as PI3Kδ Inhibitors

In previous work, we applied the rotation-limiting strategy and introduced a substituent at the 3-position of the pyrazolo [3,4-d]pyrimidin-4-amine as the affinity element to interact with the deeper hydrophobic pocket, discovered a series of novel quinazolinones as potent PI3Kδ inhibitors. Among them, the indole derivative 3 is one of the most selective PI3Kδ inhibitors and the 3,4-dimethoxyphenyl derivative 4 is a potent and selective dual PI3Kδ/γ inhibitor. In this study, we replaced the carbonyl group in the quinazolinone core with a sulfonyl group, designed a series of novel 2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide derivatives as PI3Kδ inhibitors. After the reduction of nitro group in N-(2,6-dimethylphenyl)-2-nitrobenzenesulfonamide 5 and N-(2,6-dimethylphenyl)-2-nitro-5-fluorobenzenesulfonamide 6, the resulting 2-aminobenzenesulfonamides were reacted with trimethyl orthoacetate to give the 3-methyl-2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide derivatives. After bromination of the 3-methyl group, the nucleophilic substitution with the 3-iodo-1H-pyrazolo[3,4-d]pyrimidin-4-amine provided the respective iodide derivatives, which were further reacted with a series of arylboronic acids via Suzuki coupling to furnish the 2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide derivatives 15a-J and 16a-d. In agreement with the quinazolinone derivatives, the introduction of a 5-indolyl or 3,4-dimethoxyphenyl at the affinity pocket generated the most potent analogues 15a and 15b with the IC₅₀ values of 217 to 266 nM, respectively. In comparison with the quinazolinone lead compounds 3 and 4, these 2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide derivatives exhibited much decreased PI3Kδ inhibitory potency, but maintained the high selectivity over other PI3K isoforms. Unlike the quinazolinone lead compound 4 that was a dual PI3Kδ/γ inhibitor, the benzthiadiazine 1,1-dioxide 15b with the same 3,4-dimethoxyphenyl moiety was more than 21-fold selective over PI3Kγ. Moreover, the introducing of a fluorine atom at the 7-position of the 2H-benzo[e][1,2,4]thiadiazine 1,1-dioxide core, in general, was not favored for the PI3Kδ inhibitory activity. In agreement with their high PI3Kδ selectivity, 15a and 15b significantly inhibited the SU-DHL-6 cell proliferation.

Preclinical Evaluation of a Fluorine-18 (18F)-Labeled Phosphatidylinositol 3-Kinase Inhibitor for Breast Cancer Imaging

Breast cancer is one of the commonest malignancies in women, especially in middle-aged and elderly women. Abnormal activation of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKt/mTOR) pathway has been found to be involved in breast cancer proliferation. Pictilisib (GDC-0941) is a potent inhibitor of PI3K with high affinity and is undergoing phase 2 clinical trials. In this study, we aimed to develop a noninvasive PI3K radiotracer to help determine the mechanism of the PI3K/AKt/mTOR pathway to aid in diagnosis. We designed a new ¹⁸F-radiolabeled radiotracer based on the structure of pictilisib, to evaluate noninvasively abnormal activation of the PI3K/AKT/mTOR pathway. To increase the water solubility, and to decrease hepatobiliary and gastrointestinal uptake of the tracer, pictilisib was modified with triethylene glycol di(p-toluenesulfonate) (TsO-PEG₃-OTs) to obtain TsO-PEG₃-GDC-0941 as the precursor for ¹⁸F labeling. A nonradiolabeled reference compound [¹⁹F]-PEG₃-GDC-0941 was also prepared. Breast cancer cell lines, MCF-7 and MDA-MB-231, were used as high- and low-expression PI3K models, respectively. PET imaging and ex vivo biodistribution assays of [¹⁸F]-PEG₃-GDC-0941 in MCF-7 and MDA-MB-231 xenografts were also performed, and the results were compared. The precursor compound and reference standard compound were successfully synthesized and identified using NMR and mass spectroscopy. The ¹⁸F radiolabeling was achieved with a high yield (61 ± 1%) at a high molar activity (2100 ± 100 MBq/mg). MicroPET images and biodistribution studies showed a higher uptake of the radiotracer in MCF-7 tumors than in MDA-MB-231 tumors (7.56 ± 1.01%ID/g vs 4.07 ± 0.68%ID/g, 1 h postinjection). Additionally, the MCF-7 tumor uptake was significantly decreased when a blocking dose of GDC-0941 was coinjected, indicating high specificity. The liver was found to be the major excretory organ with 5.82 ± 0.88%ID/g at 30 min postinjection for MCF-7 mice. This radiotracer holds great potential for patient screening, diagnosis, and therapy prediction of PI3K-related diseases.

Differences in Signaling Patterns on PI3K Inhibition Reveal Context Specificity in KRAS-Mutant Cancers

It is increasingly appreciated that drug response to different cancers driven by the same oncogene is different and may relate to differences in rewiring of signal transduction. We aimed to study differences in dynamic signaling changes within mutant KRAS (KRAS MT), non-small cell lung cancer (NSCLC), colorectal cancer, and pancreatic ductal adenocarcinoma (PDAC) cells. We used an antibody-based phosphoproteomic platform to study changes in 50 phosphoproteins caused by seven targeted anticancer drugs in a panel of 30 KRAS MT cell lines and cancer cells isolated from 10 patients with KRAS MT cancers. We report for the first time significant differences in dynamic signaling between colorectal cancer and NSCLC cell lines exposed to clinically relevant equimolar concentrations of the pan-PI3K inhibitor pictilisib including a lack of reduction of p-AKTser473 in colorectal cancer cell lines (P = 0.037) and lack of compensatory increase in p-MEK in NSCLC cell lines (P = 0.036). Differences in rewiring of signal transduction between tumor types driven by KRAS MT cancers exist and influence response to combination therapy using targeted agents.

Impact of Inadequate Methods and Data Analysis on Reproducibility

Failure to reproduce results of articles is recognized, but the causes, and therefore solutions, are not. One possibility is that deficits in quality of the work result in varying or inconclusive results. Erythropoiesis-stimulating agents have been used to treat anemia in patients with cancer, but there are concerns that erythropoiesis-stimulating agents might stimulate Epo receptors on tumor cells (Epo receptor-cancer hypothesis). Articles have been published on the topic, but the data and conclusions conflict, making them suitable for examination of a relationship between quality and reproducibility. Comprehensive literature searches were performed, and 280 relevant articles were identified. Numerous conflicts between and within these articles were apparent. The incidence of faults in quality parameters was high, including absence of adequate controls (90% of articles), inadequate validation of reagents and methods (87% of articles), and inadequate or improper statistical methods (84% of articles) with questionable interpretation of the data (81% of articles). This resulted in false-positive/negative data that varied with the reagents and methods used. The low quality of evidence may explain the poor reproducibility of Epo receptor-cancer articles.

Low-dose triple drug combination targeting the PI3K/AKT/mTOR pathway and the MAPK pathway is an effective approach in ovarian clear cell carcinoma

Advanced stage ovarian clear cell carcinoma (OCCC) is poorly responsive to platinum-based chemotherapy and has an unfavorable prognosis. Previous studies revealed heterogeneous mutations in PI3K/AKT/mTOR and MAPK pathway nodules converging in mTORC1/2 activation. Here, we aimed to identify an effective low-dose combination of PI3K/AKT/mTOR pathway and MAPK pathway inhibitors simultaneously targeting key kinases in OCCC to preclude single-inhibitor initiated pathway rewiring and limit toxicity. Small molecule inhibitors of mTORC1/2, PI3K and MEK1/2 were combined at monotherapy IC₂₀ doses in a panel of genetically diverse OCCC cell lines (n = 7) to determine an optimal low-dose combination. The IC₂₀ dose triple combination reduced kinase activity in PI3K/AKT/mTOR and MAPK pathways, prevented single-inhibitor induced feedback mechanisms and inhibited short and long-term proliferation in all seven cell lines. Finally, this low-dose triple drug combination treatment significantly reduced tumor growth in two genetically characterized OCCC patient-derived xenograft (PDX) models without resulting in weight loss in these mice. The effectiveness and tolerability of this combined therapy in PDX models warrants clinical exploration of this treatment strategy for OCCC and might be applicable to other cancer types with a similar genetic background.

Revisiting mTOR inhibitors as anticancer agents

The mammalian target of rapamycin (mTOR) is a highly conserved serine/threonine kinase that regulates a variety of cellular processes, influencing diverse pathological conditions including a variety of cancers. Accordingly, therapies that target mTOR as anticancer agents benefit patients in various clinical settings. It is therefore important to fully investigate mTOR signaling at a molecular level and corresponding mTOR inhibitors to identify additional clinical opportunities of targeting mTOR in cancers. In this review, we introduce the function and regulation of the mTOR signaling pathway and organize and summarize the different roles of mTOR in cancers and a variety of mTOR inhibitors that can be used as anticancer agents. This article aims to enlighten and guide the development of mTOR-targeted anticancer agents in the future.

Dissecting mechanisms of resistance to targeted drug combination therapy in human colorectal cancer

Genomic alterations in cancer cells result in vulnerabilities that clinicians can exploit using molecularly targeted drugs, guided by knowledge of the tumour genotype. However, the selective activity of these drugs exerts an evolutionary pressure on cancers that can result in the outgrowth of resistant clones. Use of rational drug combinations can overcome resistance to targeted drugs, but resistance may eventually develop to combinatorial therapies. We selected MAPK- and PI3K-pathway inhibition in colorectal cancer as a model system to dissect out mechanisms of resistance. We focused on these signalling pathways because they are frequently activated in colorectal tumours, have well-characterised mutations and are clinically relevant. By treating a panel of 47 human colorectal cancer cell lines with a combination of MEK- and PI3K-inhibitors, we observe a synergistic inhibition of growth in almost all cell lines. Cells with KRAS mutations are less sensitive to PI3K inhibition, but are particularly sensitive to the combined treatment. Colorectal cancer cell lines with inherent or acquired resistance to monotherapy do not show a synergistic response to the combination treatment. Cells that acquire resistance to an MEK-PI3K inhibitor combination treatment still respond to an ERK-PI3K inhibitor regimen, but subsequently also acquire resistance to this combination treatment. Importantly, the mechanisms of resistance to MEK and PI3K inhibitors observed, MEK1/2 mutation or loss of PTEN, are similar to those detected in the clinic. ERK inhibitors may have clinical utility in overcoming resistance to MEK inhibitor regimes; however, we find a recurrent active site mutation of ERK2 that drives resistance to ERK inhibitors in mono- or combined regimens, suggesting that resistance will remain a hurdle. Importantly, we find that the addition of low concentrations of the BCL2-family inhibitor navitoclax to the MEK-PI3K inhibitor regimen improves the synergistic interaction and blocks the acquisition of resistance.