BAY 1125976, a selective allosteric AKT1/2 inhibitor, exhibits high efficacy on AKT signaling-dependent tumor growth in mouse models

Phosphatidic acid as a cofactor of mTORC1 in platinum-based chemoresistance: Mechanisms and therapeutic potential

Platinum-based chemotherapeutics, such as cisplatin and carboplatin, are widely used to treat various malignancies. However, the development of chemoresistance remains a significant challenge, limiting their efficacy. This review explores the multifaceted mechanisms of platinum-based chemoresistance, with a particular focus on the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway, which plays a critical role in promoting tumor survival and resistance to platinum compounds. Additionally, we examined the role of phosphatidic acid (PA) and its synthesizing enzymes, phospholipase D (PLD) and lysophosphatidic acid acyltransferase (LPAAT), in the regulation of mTORC1 activity. Given the involvement of mTORC1 in chemoresistance, we evaluated the potential of mTOR inhibitors as a therapeutic strategy to overcome platinum resistance. Finally, we discuss combination therapies targeting the mTOR pathway alongside conventional chemotherapy to improve treatment outcomes. This review highlights the potential of targeting mTORC1 and related pathways to improve therapeutic strategies for chemoresistant cancers.

Discovery of novel Akt1 inhibitors by an ensemble-based virtual screening method, molecular dynamics simulation, and in vitro biological activity testing

Akt1, as an important member of the Akt family, plays a controlled role in cancer cell growth and survival. Inhibition of Akt1 activity can promote cancer cell apoptosis and inhibit tumor growth. Therefore, in this investigation, a multilayer virtual screening approach, including receptor-ligand interaction-based pharmacophore, 3D-QSAR, molecular docking, and deep learning methods, was utilized to construct a virtual screening platform for Akt1 inhibitors. 17 representative compounds with different scaffolds were identified as potential Akt1 inhibitors from three databases. Among these 17 compounds, the Hit9 exhibited the best inhibitory activity against Akt1 with inhibition rate of 33.08% at concentration of 1 μM. The molecular dynamics simulations revealed that Hit9 and Akt1 could form a compact and stable complex. Moreover, Hit9 interacted with some key residues by hydrophobic, electrostatic, and hydrogen bonding interactions and induced substantial conformation changes in the hinge region of the Akt1 active site. The average binding free energies for the Akt1-CQU, Akt1-Ipatasertib, and Akt1-Hit9 systems were - 34.44, - 63.37, and - 39.14 kJ mol-1, respectively. In summary, the results obtained in this investigation suggested that Hit9 with novel scaffold may be a promising lead compound for developing new Akt1 inhibitor for treatment of various cancers with Akt1 overexpressed.

Viral microRNA regulation of Akt is necessary for reactivation of Human Cytomegalovirus from latency in CD34+ hematopoietic progenitor cells and humanized mice

Human cytomegalovirus (HCMV) actively manipulates cellular signaling pathways to benefit viral replication. Phosphatidyl-inositol 3-kinase (PI3K)/Akt signaling is an important negative regulator of HCMV replication, and during lytic infection the virus utilizes pUL38 to limit Akt phosphorylation and activity. During latency, PI3K/Akt signaling also limits virus replication, but how this is overcome at the time of reactivation is unknown. Virally encoded microRNAs (miRNAs) are a key component of the virus arsenal used to alter signaling during latency and reactivation. In the present study we show that three HCMV miRNAs (miR-UL36, miR-UL112 and miR-UL148D) downregulate Akt expression and attenuate downstream signaling, resulting in the activation of FOXO3a and enhanced internal promoter-driven IE transcription. A virus lacking expression of all three miRNAs is unable to reactivate from latency both in CD34+ hematopoietic progenitor cells and in a humanized mouse model of HCMV infection, however downregulating Akt restores the ability of the mutant virus to replicate. These findings highlight the negative role Akt signaling plays in HCMV replication in lytic and latent infection and how the virus has evolved miRNA-mediated countermeasures to promote successful reactivation.

Ion channel P2X7 receptor in the progression of cancer

P2X7 receptor (P2X7) is a non-selective and ATP-sensitive ligand-gated cation channel. Studies have confirmed that it is expressed in a variety of cells and correlates with their function, frequently in immune cells and tumor cells. We found increased expression of this receptor in many tumor cells, and it has a role in tumor survival and progression. In immune cells, upregulation of the receptor has a double effect on tumor suppression as well as tumor promotion. This review describes the structure of P2X7 and its role in the tumor microenvironment and presents possible mechanisms of P2X7 in tumor invasion and metastasis. Understanding the potential of P2X7 for tumor treatment, we also present several therapeutic agents targeting P2X7 and their mechanisms of action. In conclusion, the study of P2X7 is an important guideline for the use of clinical tumor therapy and may be able to provide a new idea for tumor treatment, but considering the complexity of the biological effects of P2X7, the drugs should be used with caution in clinical practice.

LINC01060 knockdown inhibits osteosarcoma cell malignant behaviors in vitro and tumor growth and metastasis in vivo through the PI3K/Akt signaling

Despite its low frequency, osteosarcoma is one of the deadliest malignancies in children and adolescents. The phosphatidylinositol 3-kinase (PI3K)/Akt signaling activation and epithelial-to-mesenchymal transition (EMT) are critical issues during osteosarcoma development. This study found long intergenic non-protein coding RNA 1060 (LINC01060) to be an EMT-related long non-coding RNA (lncRNA) up-regulated in osteosarcoma; higher LINC01060 expression was linked to a worse prognosis in osteosarcoma patients. In vitro, knocking down LINC01060 significantly inhibits osteosarcoma cell malignant behaviors, including hyperproliferation, invasion, migration, and EMT. In vivo, LINC01060 knockdown inhibited tumor growth and metastasis, and suppressed PI3K and Akt phosphorylation. In osteosarcoma cells, Akt agonist SC79 exerted opposite effects to those of LINC01060 knockdown through the promotion of cell viability, cell migration, and cell invasion. Moreover, the Akt agonist SC79 partially eliminated LINC01060 knockdown effects on osteosarcoma cells, suggesting that LINC01060 exerts its effects through the PI3K/Akt signaling. Therefore, it is deduced that LINC01060 is overexpressed in osteosarcoma. In vitro, LINC01060 knockdown inhibits cancer cell malignant behaviors; in vivo, LINC01060 knockdown inhibits tumor development and metastasis. The PI3K/Akt signaling is involved in LINC01060 functions in osteosarcoma.

Inhibitors of phosphoinositide 3-kinase (PI3K) and phosphoinositide 3-kinase-related protein kinase family (PIKK)

Phosphoinositide 3-kinases (PI3K) and phosphoinositide 3-kinase-related protein kinases (PIKK) are two structurally related families of kinases that play vital roles in cell growth and DNA damage repair. Dysfunction of PIKK members and aberrant stimulation of the PI3K/AKT/mTOR signalling pathway are linked to a plethora of diseases including cancer. In recent decades, numerous inhibitors related to the PI3K/AKT/mTOR signalling have made great strides in cancer treatment, like copanlisib and sirolimus. Notably, most of the PIKK inhibitors (such as VX-970 and M3814) related to DNA damage response have also shown good efficacy in clinical trials. However, these drugs still require a suitable combination therapy to overcome drug resistance or improve antitumor activity. Based on the aforementioned facts, we summarised the efficacy of PIKK, PI3K, and AKT inhibitors in the therapy of human malignancies and the resistance mechanisms of targeted therapy, in order to provide deeper insights into cancer treatment.

Exploring the role of PI3K/AKT/mTOR inhibitors in hormone-related cancers: A focus on breast and prostate cancer

Breast cancer (BC) and prostate cancer (PC) are at the top of the list when it comes to the most common types of cancers worldwide. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway is important, in that it strongly influences the development and progression of these tumors. Previous studies have emphasized the key role of inhibitors of the PIK3/AKT/mTOR signaling pathway in the treatment of BC and PC, and it remains to be a crucial method of treatment. In this review, the inhibitors of these signaling pathways are compared, as well as their effectiveness in therapy and potential as therapeutic agents. The use of these inhibitors as polytherapy is evaluated, especially with the use of hormonal therapy, which has shown promising results.

Pleckstrin Homology [PH] domain, structure, mechanism, and contribution to human disease

The pleckstrin homology [PH] domain is a structural fold found in more than 250 proteins making it the 11th most common domain in the human proteome. 25% of family members have more than one PH domain and some PH domains are split by one, or several other, protein domains although still folding to give functioning PH domains. We review mechanisms of PH domain activity, the role PH domain mutation plays in human disease including cancer, hyperproliferation, neurodegeneration, inflammation, and infection, and discuss pharmacotherapeutic approaches to regulate PH domain activity for the treatment of human disease. Almost half PH domain family members bind phosphatidylinositols [PIs] that attach the host protein to cell membranes where they interact with other membrane proteins to give signaling complexes or cytoskeleton scaffold platforms. A PH domain in its native state may fold over other protein domains thereby preventing substrate access to a catalytic site or binding with other proteins. The resulting autoinhibition can be released by PI binding to the PH domain, or by protein phosphorylation thus providing fine tuning of the cellular control of PH domain protein activity. For many years the PH domain was thought to be undruggable until high-resolution structures of human PH domains allowed structure-based design of novel inhibitors that selectively bind the PH domain. Allosteric inhibitors of the Akt1 PH domain have already been tested in cancer patients and for proteus syndrome, with several other PH domain inhibitors in preclinical development for treatment of other human diseases.

Enhanced compound-protein binding affinity prediction by representing protein multimodal information via a coevolutionary strategy

Due to the lack of a method to efficiently represent the multimodal information of a protein, including its structure and sequence information, predicting compound-protein binding affinity (CPA) still suffers from low accuracy when applying machine-learning methods. To overcome this limitation, in a novel end-to-end architecture (named FeatNN), we develop a coevolutionary strategy to jointly represent the structure and sequence features of proteins and ultimately optimize the mathematical models for predicting CPA. Furthermore, from the perspective of data-driven approach, we proposed a rational method that can utilize both high- and low-quality databases to optimize the accuracy and generalization ability of FeatNN in CPA prediction tasks. Notably, we visually interpret the feature interaction process between sequence and structure in the rationally designed architecture. As a result, FeatNN considerably outperforms the state-of-the-art (SOTA) baseline in virtual drug evaluation tasks, indicating the feasibility of this approach for practical use. FeatNN provides an outstanding method for higher CPA prediction accuracy and better generalization ability by efficiently representing multimodal information of proteins via a coevolutionary strategy.

An advanced molecular medicine case report of a rare human tumor using genomics, pathomics, and radiomics

Background: Pulmonary Sclerosing Pneumocytoma (PSP) is a rare tumor of the lung with a low malignant potential that primarily affects females. Initial studies of PSP focused primarily on analyzing features uncovered using conventional X-ray or CT imaging. In recent years, because of the widespread use of next-generation sequencing (NGS), the study of PSP at the molecular-level has emerged. Methods: Analytical approaches involving genomics, radiomics, and pathomics were performed. Genomics studies involved both DNA and RNA analyses. DNA analyses included the patient's tumor and germline tissues and involved targeted panel sequencing and copy number analyses. RNA analyses included tumor and adjacent normal tissues and involved studies covering expressed mutations, differential gene expression, gene fusions and molecular pathways. Radiomics approaches were utilized on clinical imaging studies and pathomics techniques were applied to tumor whole slide images. Results: A comprehensive molecular profiling endeavor involving over 50 genomic analyses corresponding to 16 sequencing datasets of this rare neoplasm of the lung were generated along with detailed radiomic and pathomic analyses to reveal insights into the etiology and molecular behavior of the patient's tumor. Driving mutations (AKT1) and compromised tumor suppression pathways (TP53) were revealed. To ensure the accuracy and reproducibility of this study, a software infrastructure and methodology known as NPARS, which encapsulates NGS and associated data, open-source software libraries and tools including versions, and reporting features for large and complex genomic studies was used. Conclusion: Moving beyond descriptive analyses towards more functional understandings of tumor etiology, behavior, and improved therapeutic predictability requires a spectrum of quantitative molecular medicine approaches and integrations. To-date this is the most comprehensive study of a patient with PSP, which is a rare tumor of the lung. Detailed radiomic, pathomic and genomic molecular profiling approaches were performed to reveal insights regarding the etiology and molecular behavior. In the event of recurrence, a rational therapy plan is proposed based on the uncovered molecular findings.

Addressing the Reciprocal Crosstalk between the AR and the PI3K/AKT/mTOR Signaling Pathways for Prostate Cancer Treatment

The reduction in androgen synthesis and the blockade of the androgen receptor (AR) function by chemical castration and AR signaling inhibitors represent the main treatment lines for the initial stages of prostate cancer. Unfortunately, resistance mechanisms ultimately develop due to alterations in the AR pathway, such as gene amplification or mutations, and also the emergence of alternative pathways that render the tumor less or, more rarely, completely independent of androgen activation. An essential oncogenic axis activated in prostate cancer is the phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, as evidenced by the frequent alterations of the negative regulator phosphatase and tensin homolog (PTEN) and by the activating mutations in PI3K subunits. Additionally, crosstalk and reciprocal feedback loops between androgen signaling and the PI3K/AKT/mTOR signaling cascade that activate pro-survival signals and play an essential role in disease recurrence and progression have been evidenced. Inhibitors addressing different players of the PI3K/AKT/mTOR pathway have been evaluated in the clinic. Only a limited benefit has been reported in prostate cancer up to now due to the associated side effects, so novel combination approaches and biomarkers predictive of patient response are urgently needed. Here, we reviewed recent data on the crosstalk between AR signaling and the PI3K/AKT/mTOR pathway, the selective inhibitors identified, and the most advanced clinical studies, with a focus on combination treatments. A deeper understanding of the complex molecular mechanisms involved in disease progression and treatment resistance is essential to further guide therapeutic approaches with improved outcomes.

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.

PIK3CA mutations in breast cancer: A Tunisian series

BACKGROUND

The aim of this study was to analyze PIK3CA mutations in exons 9 and 20 in breast cancers (BCs) and their association with clinicopathological characteristics.

METHODS

Mutational analysis of PIK3CA exon 9 and 20 was performed by Sanger sequencing in 54 primary BCs of Tunisian women. The associations of PIK3CA mutations with clinicopathological characteristics were analyzed.

RESULTS

Fifteen exon 9 and exon 20 PIK3CA variants were identified in 33/54 cases (61%). PIK3CA mutations including pathogenic (class 5/Tier I) or likely pathogenic (class 4/Tier II) occurred in 24/54 cases (44%): 17/24 cases (71%) in exon 9, 5/24 cases (21%) in exon 20 and 2/24 cases (8%) in both exons. Of these 24 cases, 18 (75%) carried at least one of the three hot spot mutations: E545K (in 8 cases), H1047R (in 4 cases), E542K (in 3 cases), E545K/E542K (in one case), E545K/H1047R (in one case) and P539R/H1047R (in one case). Pathogenic PIK3CA mutations were associated with negative lymph node status (p = 0.027). Age distribution, histological SBR tumor grading, estrogen and progesterone receptors, human epidermal growth factor receptor 2, and molecular classification were not correlated with PIK3CA mutations (p > 0.05).

CONCLUSION

The frequency of somatic PIK3CA mutations in BCs of Tunisian women is slightly higher than that of BCs of Caucasian women and more observed in exon 9 than in exon 20. PIK3CA mutated status is associated with negative lymph node status. These data need to be confirmed in larger series.

Targeting the PI3K/AKT/mTOR Signaling Pathway in the Treatment of Human Diseases: Current Status, Trends, and Solutions

The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is one of the most important intracellular pathways involved in cell proliferation, growth, differentiation, and survival. Therefore, this route is a prospective biological target for treating various human diseases, such as tumors, neurodegenerative diseases, pulmonary fibrosis, and diabetes. An increasing number of clinical studies emphasize the necessity of developing novel molecules targeting the PI3K/AKT/mTOR pathway. This review focuses on recent advances in ATP-competitive inhibitors, allosteric inhibitors, covalent inhibitors, and proteolysis-targeting chimeras against the PI3K/AKT/mTOR pathway, and highlights possible solutions for overcoming the toxicities and acquired drug resistance of currently available drugs. We also provide recommendations for the future design and development of promising drugs targeting this pathway.

Akt: a key transducer in cancer

Growth factor signaling plays a pivotal role in diverse biological functions, such as cell growth, apoptosis, senescence, and migration and its deregulation has been linked to various human diseases. Akt kinase is a central player transmitting extracellular clues to various cellular compartments, in turn executing these biological processes. Since the discovery of Akt three decades ago, the tremendous progress towards identifying its upstream regulators and downstream effectors and its roles in cancer has been made, offering novel paradigms and therapeutic strategies for targeting human diseases and cancers with deregulated Akt activation. Unraveling the molecular mechanisms for Akt signaling networks paves the way for developing selective inhibitors targeting Akt and its signaling regulation for the management of human diseases including cancer.

Identification and development of a subtype-selective allosteric AKT inhibitor suitable for clinical development

The serine/threonine protein kinase AKT plays a pivotal role within the PI3K pathway in regulating cellular proliferation and apoptotic cellular functions, and AKT hyper-activation via gene amplification and/or mutation has been implicated in multiple human malignancies. There are 3 AKT isoenzymes (AKT1-3) which mediate critical, non-redundant functions. We present the discovery and development of ALM301, a novel, allosteric, sub-type selective inhibitor of AKT1/2. ALM301 binds in an allosteric pocket created by the combined movement of the PH domain and the catalytic domain, resulting in a DFG out conformation. ALM301 was shown to be highly selective against a panel of over 450 kinases and potently inhibited cellular proliferation. These effects were particularly pronounced in MCF-7 cells containing a PI3KCA mutation. Subsequent cellular downstream pathway analysis in this sensitive cell line revealed potent inhibition of pAKT signalling up to 48 h post dosing. ALM301 treatment was well tolerated in an MCF-7 xenograft model and led to a dose-dependent reduction in tumour growth. Enhanced efficacy was observed in combination with tamoxifen. In summary, ALM301 is a highly specific AKT 1/2 inhibitor with an excellent pharmacological profile suitable for further clinical development.

Analysis of the epidermal growth factor receptor/phosphoinositide-dependent protein kinase-1 axis in tumor of the external auditory canal in response to epidermal growth factor stimulation

Objectives

The epidermal growth factor receptor (EGFR) is related to the invasion and metastasis of external auditory canal (EAC) squamous cell carcinoma (SCC). The phosphoinositide-dependent protein kinase-1 (PDPK1) accelerates tumor cell growth through anti-apoptotic signaling under the influence of downstream EGFR-mediated signaling pathways. In this study, we investigated the EGFR/PDPK1 axis in the EAC under EGF stimulation.

Methods

We confirmed EGFR and PDPK1 expression in human EACSCC specimens immunohistochemically. We next transfected the EGF expression vector in the mouse EAC and then conducted a PDPK1 inhibitory experiment. Immunohistochemical analysis was performed in the mouse EAC, using anti-EGF, anti-EGFR, anti-PDPK1, and anti-Ki67 antibodies. Immunohistochemical analysis of cleaved caspase-3 and terminal deoxy(d)-UTP nick end labeling (TUNEL) detection assays were also performed for the assessment of apoptosis in the inhibitory experiment.

Results

Immunohistochemical analysis revealed overexpression and colocalization of EGFR and PDPK1 in human EACSCC specimens. The growth of a protuberant tumor was observed in the mouse EAC in which EGF expression vector was transfected, and EGF, EGFR, PDPK1, and Ki67 labeling indexes (LIs) were significantly increased. PDPK1 inhibition then induced normal epithelial appearance in the EAC. Moreover, EGF, EGFR, PDPK1, and Ki67 LIs were decreased, and cleaved caspase-3 and TUNEL LIs were increased in the EAC.

Conclusion

We demonstrated the possibility that PDPK1 plays an important role in EACSCC.Level of Evidence: NA.

Role of PI3K/Akt/mTOR pathway in mediating endocrine resistance: concept to clinic

The majority of breast cancers express the estrogen receptor (ER) and for this group of patients, endocrine therapy is the cornerstone of systemic treatment. However, drug resistance is common and a focus for breast cancer preclinical and clinical research. Over the past 2 decades, the PI3K/Akt/mTOR axis has emerged as an important driver of treatment failure, and inhibitors of mTOR and PI3K are now licensed for the treatment of women with advanced ER-positive breast cancer who have relapsed on first-line hormonal therapy. This review presents the preclinical and clinical data that led to this new treatment paradigm and discusses future directions.

The PI3K/Akt/mTOR pathway in lung cancer; oncogenic alterations, therapeutic opportunities, challenges, and a glance at the application of nanoparticles

•

Lung cancer is the most common and deadliest human malignancies.

•

The alterations of PI3K/Akt/mTOR pathway are related to lung cancer progression.

•

PI3K axis regulates proliferation, apoptosis, metastasis, and EMT of lung cancer.

•

Agents inhibiting components of PI3K axis diminish lung tumor growth and invasion.

•

Low efficacy and off-target toxicity could be improved by nanoparticle application.

Lung cancer is the leading cause of cancer-related mortality worldwide. Although the PI3K/Akt/mTOR signaling pathway has recently been considered as one of the most altered molecular pathways in this malignancy, few articles reviewed the task. In this review, we aim to summarize the original data obtained from international research laboratories on the oncogenic alterations in each component of the PI3K/Akt/mTOR pathway in lung cancer. This review also responds to questions on how aberrant activation in this axis contributes to uncontrolled growth, drug resistance, sustained angiogenesis, as well as tissue invasion and metastatic spread. Besides, we provide a special focus on pharmacologic inhibitors of the PI3K/Akt/mTOR axis, either as monotherapy or in a combined-modal strategy, in the context of lung cancer. Despite promising outcomes achieved by using these agents, however, the presence of drug resistance as well as treatment-related adverse events is the other side of the coin. The last section allocates a general overview of the challenges associated with the inhibitors of the PI3K pathway in lung cancer patients. Finally, we comment on the future research aspects, especially in which nano-based drug delivery strategies might increase the efficacy of the therapy in this malignancy.

Antibody-mediated procoagulant platelet formation in COVID-19 is AKT dependent

BACKGROUND

Thromboembolic events are frequently reported in patients infected with the SARS-CoV-2. Recently, we observed that platelets from patients with severe COVID-19 infection express procoagulant phenotype. The molecular mechanisms that induce the generation of procoagulant platelets in COVID-19 patients are not completely understood.

OBJECTIVES

In this study, we investigated the role of AKT (also known as Protein Kinase B), which is the major downstream effector of PI3K (phosphoinositid-3-kinase) (PI3K/AKT) signaling pathway in platelets from patients with COVID-19.

PATIENTS AND METHODS

Platelets, Sera and IgG from COVID-19 patients who were admitted to the intensive care unit (ICU) were analyzed by flow cytometry as well as western blot and adhesion assays.

RESULTS

Platelets from COVID-19 patients showed significantly higher levels of phosphorylated AKT, which was correlated with CD62p expression and phosphatidylserine (PS) externalization. In addition, healthy platelets incubated with sera or IgGs from ICU COVID-19 patients induced phosphorylation of PI3K and AKT and were dependent on Fc-gamma-RIIA (FcγRIIA). In contrast, ICU COVID-19 sera mediated generation of procoagulant platelets was not dependent on GPIIb/IIIa. Interestingly, the inhibition of phosphorylation of both proteins AKT and PI3K prevented the generation of procoagulant platelets.

CONCLUSIONS

Our study shows that pAKT/AKT signaling pathway is associated with the formation of procoagulant platelets in severe COVID-19 patients without integrin GPIIb/IIIa engagement. The inhibition of PI3K/AKT phosphorylation might represent a promising strategy to reduce the risk for thrombosis in patients with severe COVID-19.

AKT Isoforms as a Target in Cancer and Immunotherapy

Over the past years, targeted therapies have received tremendous attention in cancer therapy. One of the most frequently targeted pathways is the PI3K/AKT/mTOR signaling pathway that regulates crucial cellular processes including proliferation, survival, and migration. In a wide variety of cancer entities, the PI3K/AKT/mTOR signaling pathway was found to be a critical driver of disease progression, indicating a noteworthy target in cancer therapy. This chapter focuses on targeted therapies against AKT, which is a key enzyme within the PI3K/AKT/mTOR pathway. Although the three different isoforms of AKT, namely AKT1, AKT2, and AKT3, have a high homology, the isoforms exhibit different biological functions. Recently, direct inhibitors against all AKT isoforms as well as selective inhibitors against specific AKT isoforms have been extensively investigated in preclinical work as well as in clinical trials to attenuate proliferation of cancer cells. While no AKT inhibitor has been approved by the FDA for cancer therapy to date, AKT still plays a crucial role in a variety of treatment strategies including immune checkpoint inhibition. In this chapter, we summarize the status of AKT inhibitors either targeting all or specific AKT isoforms. Furthermore, we explain the role of AKT signaling in direct inhibition of tumor cell growth as well as in immune cells and immune checkpoint inhibition.

Endophytic actinobacteria of Hymenachne amplexicaulis from the Brazilian Pantanal wetland produce compounds with antibacterial and antitumor activities

The increase in the number of deaths from infections caused by multidrug-resistant bacteria and cancer diseases highlights the need for new molecules with biological activity. Actinobacteria represent a potential source of new compounds, as these microorganisms have already produced a great diversity of clinically employed antibiotics. Endophytes from unexplored biomes, such as the Pantanal (the largest wetland in the world), can be a source of new molecules. Hymenachne amplexicaulis is among the unexplored native plants of the Pantanal in terms of its endophytic community. This plant is considered a weed in other countries due to its ability to adapt and compete with native plants, and there is evidence to suggest that the endophytic community of H. amplexicaulis plays an important role in this competitiveness. To explore its therapeutic potential, the present study isolated, identified (using partial sequence of the 16S rDNA) and bioprospected H. amplexicaulis endophytic actinobacteria. Ten isolates belonging to the genera Streptomyces, Microbispora, Leifsonia, and Verrucosispora were obtained from root fragments. The susceptibility profile of the isolates to the different classes of antibiotics was evaluated, with 80 % of the isolates showing resistance to the antibiotics Nalidixic Acid, Ampicillin, Chloramphenicol, Oxacillin, and Rifampicin. To assess antibacterial and antitumor activities, methanolic extracts were obtained by fermentation in SG culture medium at 36 °C at 180 rpm for 10 days. The extract produced from the S. albidoflavus CMRP4854 isolate was the only one to show activity against the Gram-negative bacterium Acinetobacter baumanii. Due to the great clinical importance of this pathogen and the difficulty in obtaining active compounds against it, the CMRP4854 isolate should be further investigated for the identification of active compounds and mode of action. We also emphasize the results obtained by the extract of the isolates Streptomyces albidoflavus CMRP4852 and Verrucosispora sp. CMRP4860 that presented antibacterial effect against Methicilin-resistant Staphylococcus aureus (MRSA) (MIC: 1.5 μg/mL and 13 μg/mL, respectively) and Vancomycin-resistant Enterococcus (VRE) (MIC: 40 μg/mL for both extracts). Extracts (200 μg/mL) of these two endophytes also showed selective cytotoxicity action against murine B16-F10 melanoma cells. However, the CMRP4852 extract also affected the density of normal cells. Due to these results, the crude extract of isolate CMRP4860 Verrucosispora sp., which was the only one that presented cytotoxicity and reduced cell density only in tumor cells, was selected for subsequent analysis involving scale-up fermentation of the CMRP4860 resulting in 9 fractions that were tested against both bacteria and tumor cells, with particular fractions showing promise and meriting further investigation. Taken together, the results of this study not only show for the first time that the endophytic community of H. amplexicaulis actinobacteria can produce secondary metabolites that potentially possess important antibacterial and cytotoxic properties, but also reinforce the pressing need to conserve biomes such as the Brazilian Pantanal.

Combating TKI resistance in CML by inhibiting the PI3K/Akt/mTOR pathway in combination with TKIs: a review

Chronic myeloid leukemia (CML), a myeloproliferative hematopoietic cancer, is caused by a genetic translocation between chromosomes 9 and 22. This translocation produces a small Philadelphia chromosome, which contains the Bcr-Abl oncogene. The Bcr-Abl oncogene encodes the BCR-ABL protein, upregulates various signaling pathways (JAK-STAT, MAPK/ERK, and PI3K/Akt/mTOR), and out of which the specifically highly active pathway is the PI3K/Akt/mTOR pathway. Among early treatments for CML, tyrosine kinase inhibitors (TKIs) were found to be the most effective, but drug resistance against kinase inhibitors led to the discovery of novel alternative therapies. At this point, the PI3K/Akt/mTOR pathway components became new targets due to stimulation of this pathway in TKIs-resistant CML patients. The current review article deals with reviewing the scientific literature on the PI3K/Akt/mTOR pathway inhibitors listed in the National Cancer Institute (NCI) drug dictionary and proved effective against multiple cancers. And out of those enlisted inhibitors, the US FDA has also approved some PI3K inhibitors (Idelalisib, Copanlisib, and Duvelisib) and mTOR inhibitors (Everolimus, Sirolimus, and Temsirolimus) for cancer therapy. So far, several inhibitors have been tested, and further investigations are still ongoing. Even in Imatinib, Nilotinib, and Ponatinib-resistant CML cells, a dual PI3K/mTOR inhibitor, BEZ235, showed antiproliferative activity. Therefore, by considering the literature data of these reviews and further examining some of the reported inhibitors, which proved effective against the PI3K/Akt/mTOR signaling pathway in multiple cancers, may improve the therapeutic approaches towards TKI-resistant CML cells where the respective signaling pathway gets upregulated.

Biological Role of AKT and Regulation of AKT Signaling Pathway by Thymoquinone: Perspectives in Cancer Therapeutics

BACKGROUND

AKT/PKB is an important enzyme with numerous biological functions, and its overexpression is related to carcinogenesis. AKT stimulates different signaling pathways that are downstream of activated tyrosine kinases and phosphatidylinositol 3-kinase, hence functions as an important target for anti-cancer drugs.

OBJECTIVE

In this review article, we have interpreted the role of AKT signaling pathway in cancer and the natural inhibitory effect of Thymoquinone (TQ) in AKT and its possible mechanisms.

METHOD

We have collected the updated information and data on AKT, its role in cancer and the inhibitory effect of TQ in AKT signaling pathway from Google Scholar, PubMed, Web of Science, Elsevier, Scopus, and many more.

RESULTS

Many drugs are already developed, which can target AKT, but very few among them have passed clinical trials. TQ is a natural compound, mainly found in black cumin, which has been found to have potential anti-cancer activities. TQ targets numerous signaling pathways, including AKT, in different cancers. In fact, many studies revealed that AKT is one of the major targets of TQ. The preclinical success of TQ suggests its clinical studies on cancer.

CONCLUSION

This review article summarizes the role of AKT in carcinogenesis, its potent inhibitors in clinical trials, and how TQ acts as an inhibitor of AKT and TQ's future as a cancer therapeutic drug.

Inositol Polyphosphate-Based Compounds as Inhibitors of Phosphoinositide 3-Kinase-Dependent Signaling

Signaling pathways regulated by the phosphoinositide 3-kinase (PI3K) enzymes have a well-established role in cancer development and progression. Over the past 30 years, the therapeutic potential of targeting this pathway has been well recognized, and this has led to the development of a multitude of drugs, some of which have progressed into clinical trials, with few of them currently approved for use in specific cancer settings. While many inhibitors compete with ATP, hence preventing the catalytic activity of the kinases directly, a deep understanding of the mechanisms of PI3K-dependent activation of its downstream effectors led to the development of additional strategies to prevent the initiation of this signaling pathway. This review summarizes previously published studies that led to the identification of inositol polyphosphates as promising parent molecules to design novel inhibitors of PI3K-dependent signals. We focus our attention on the inhibition of protein-membrane interactions mediated by binding of pleckstrin homology domains and phosphoinositides that we proposed 20 years ago as a novel therapeutic strategy.

Avoiding or Co-Opting ATP Inhibition: Overview of Type III, IV, V, and VI Kinase Inhibitors

As described in the previous chapter, most kinase inhibitors that have been developed for use in the clinic act by blocking ATP binding; however, there is growing interest in identifying compounds that target kinase activities and functions without interfering with the conserved features of the ATP-binding site. This chapter will highlight alternative approaches that exploit unique kinase structural features that are being targeted to identify more selective and potent inhibitors. The figure below, adapted from (Sammons et al., Molecular Carcinogenesis 58:1551–1570, 2019), provides a graphical description of the various approaches to manipulate kinase activity. In addition to the type I and II inhibitors, type III kinase inhibitors have been identified to target sites adjacent to the ATP-binding site in the catalytic domain. New information on kinase structure and substrate-binding sites has enabled the identification of type IV kinase inhibitor compounds that target regions outside the catalytic domain. The combination of targeting unique allosteric sites outside the catalytic domain with ATP-targeted compounds has yielded a number of novel bivalent type V kinase inhibitors. Finally, emerging interest in the development of irreversible compounds that form selective covalent interactions with key amino acids involved in kinase functions comprise the class of type VI kinase inhibitors.

The molecular mechanism behind protein kinase B natural mutant E17K affecting the allosteric inhibitor sensitivity: a molecular dynamics simulation study

Glu17Lys (E17K) is one of the natural variants of Akt1, which is associated with multiple human cancers. This mutation is also indicated to affect the sensitivity of certain allosteric inhibitors. In order to explain the molecular mechanism that E17K mutation of Akt1 affects the sensitivity of allosteric inhibitors, we performed molecular dynamics simulations on Akt1 to its allosteric inhibitors for both wild type and E17K. We analyzed the simulated data in terms of structural stability, hydrogen bond formation, π-π interactions, binding free energy etc. We found that E17K substitution will affect the interaction of K297 residues with allosteric inhibitors, which was a key residue in allosteric inhibitors binding. This will eventually lead to allosteric inhibitors leaving the binding site in the E17K system. Our results can provide a theoretical basis for the design of novel allosteric inhibitors targeting E17K mutants in the future.Communicated by Ramaswamy H. Sarma.

The c-Myc/AKT1/TBX3 Axis Is Important to Target in the Treatment of Embryonal Rhabdomyosarcoma

Rhabdomyosarcoma is a highly aggressive malignant cancer that arises from skeletal muscle progenitor cells and is the third most common solid tumour in children. Despite significant advances, rhabdomyosarcoma still presents a therapeutic challenge, and while targeted therapy has shown promise, there are limited options because the molecular drivers of rhabdomyosarcoma are poorly understood. We previously reported that the T-box transcription factor 3 (TBX3), which has been identified as a druggable target in many cancers, is overexpressed in rhabdomyosarcoma patient samples and cell lines. To identify new molecular therapeutic targets to treat rhabdomyosarcoma, this study investigates the potential oncogenic role(s) for TBX3 and the factors responsible for upregulating it in this cancer. To this end, rhabdomyosarcoma cell culture models in which TBX3 was either stably knocked down or overexpressed were established and the impact on key hallmarks of cancer were examined using growth curves, soft agar and scratch motility assays, as well as tumour-forming ability in nude mice. Our data show that TBX3 promotes substrate-dependent and -independent proliferation, migration and tumour formation. We further reveal that TBX3 is upregulated by c-Myc transcriptionally and AKT1 post-translationally. This study identifies c-Myc/AKT1/TBX3 as an important axis that could be targeted for the treatment of rhabdomyosarcoma.

Phase 1 Dose Escalation Study of the Allosteric AKT Inhibitor BAY 1125976 in Advanced Solid Cancer-Lack of Association between Activating AKT Mutation and AKT Inhibition-Derived Efficacy

This open-label, phase I first-in-human study (NCT01915576) of BAY 1125976, a highly specific and potent allosteric inhibitor of AKT1/2, aimed to evaluate the safety, pharmacokinetics, and maximum tolerated dose of BAY 1125976 in patients with advanced solid tumors. Oral dose escalation was investigated with a continuous once daily (QD) treatment (21 days/cycle) and a twice daily (BID) schedule. A dose expansion in 28 patients with hormone receptor-positive metastatic breast cancer, including nine patients harboring the AKT1E17K mutation, was performed at the recommended phase 2 dose (R2D) of 60 mg BID. Dose-limiting toxicities (Grades 3-4) were increased in transaminases, γ-glutamyltransferase (γ-GT), and alkaline phosphatase in four patients in both schedules and stomach pain in one patient. Of the 78 patients enrolled, one patient had a partial response, 30 had stable disease, and 38 had progressive disease. The clinical benefit rate was 27.9% among 43 patients treated at the R2D. AKT1E17K mutation status was not associated with tumor response. Genetic analyses revealed additional mutations that could promote tumor cell growth despite the inhibition of AKT1/2. BAY 1125976 was well tolerated and inhibited AKT1/2 signaling but did not lead to radiologic or clinical tumor responses. Thus, the refinement of a selection of biomarkers for AKT inhibitors is needed to improve their monotherapy activity.

Targeting AKT for cancer therapy

Introduction: Targeted therapies in cancer aim to inhibit specific molecular targets responsible for enhanced tumor growth. AKT/PKB (protein kinase B) is a serine threonine kinase involved in several critical cellular pathways, including survival, proliferation, invasion, apoptosis, and angiogenesis. Although phosphatidylinositol-3 kinase (PI3K) is the key regulator of AKT activation, numerous stimuli and kinases initiate pro-proliferative AKT signaling which results in the activation of AKT pathway to drive cellular growth and survival. Activating mutations and amplification of components of the AKT pathway are implicated in the pathogenesis of many cancers including breast and ovarian. Given its importance, AKT, it has been validated as a promising therapeutic target.Areas covered: This article summarizes AKT's biological function and different classes of AKT inhibitors as anticancer agents. We also explore the efficacy of AKT inhibitors as monotherapies and in combination with cytotoxic and other targeted therapies.Expert opinion: The complex mechanism following AKT inhibition requires the addition of other therapies to prevent resistance and improve clinical response. Further studies are necessary to determine additional rational combinations that can enhance efficacy of AKT inhibitors, potentially by targeting compensatory mechanisms, and/or enhancing apoptosis. The identification of biomarkers of response is essential for the development of successful therapeutics.

The Novel ATR Inhibitor BAY 1895344 Is Efficacious as Monotherapy and Combined with DNA Damage-Inducing or Repair-Compromising Therapies in Preclinical Cancer Models

The DNA damage response (DDR) secures the integrity of the genome of eukaryotic cells. DDR deficiencies can promote tumorigenesis but concurrently may increase dependence on alternative repair pathways. The ataxia telangiectasia and Rad3-related (ATR) kinase plays a central role in the DDR by activating essential signaling pathways of DNA damage repair. Here, we studied the effect of the novel selective ATR kinase inhibitor BAY 1895344 on tumor cell growth and viability. Potent antiproliferative activity was demonstrated in a broad spectrum of human tumor cell lines. BAY 1895344 exhibited strong monotherapy efficacy in cancer xenograft models that carry DNA damage repair deficiencies. The combination of BAY 1895344 with DNA damage-inducing chemotherapy or external beam radiotherapy (EBRT) showed synergistic antitumor activity. Combination treatment with BAY 1895344 and DDR inhibitors achieved strong synergistic antiproliferative activity in vitro, and combined inhibition of ATR and PARP signaling using olaparib demonstrated synergistic antitumor activity in vivo Furthermore, the combination of BAY 1895344 with the novel, nonsteroidal androgen receptor antagonist darolutamide resulted in significantly improved antitumor efficacy compared with respective single-agent treatments in hormone-dependent prostate cancer, and addition of EBRT resulted in even further enhanced antitumor efficacy. Thus, the ATR inhibitor BAY 1895344 may provide new therapeutic options for the treatment of cancers with certain DDR deficiencies in monotherapy and in combination with DNA damage-inducing or DNA repair-compromising cancer therapies by improving their efficacy.

Recent nanotechnological interventions targeting PI3K/Akt/mTOR pathway: A focus on breast cancer

Breast cancer is the major cause of deaths in women worldwide. Detection and treatment of breast cancer at earlier stages of the disease has shown encouraging results. Modern genomic technologies facilitated several therapeutic options however the diagnosis of the disease at an advanced stage claim more deaths. Therefore more research directed towards genomics and proteomics into this area may lead to novel biomarkers thereby enhancing the survival rates in breast cancer patients. Phosphoinositide-3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway was shown to be hyperactivated in most of the breast carcinomas resulting in excessive growth, proliferation, and tumor development. Development of nanotechnology has provided many interesting avenues to target the PI3K/Akt/mTOR pathway both at the pre-clinical and clinical stages. Therefore, the current review summarizes the underlying mechanism and the importance of targeting PI3K/Akt/mTOR pathway, novel biomarkers and use of nanotechnological interventions in breast cancer.

Anti-inflammatory functions of the CDC25 phosphatase inhibitor BN82002 via targeting AKT2

This study presents BN82002 as an anti-inflammatory drug candidate. It was found that BN82002 inhibited the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) in RAW 264.7 cells and peritoneal macrophages that were activated by toll-like receptor (TLR) 4 ligand, lipopolysaccharide (LPS). BN82002 dose-dependently down-regulated mRNA levels of nitric oxide synthase, tumor necrosis factor-α, and cyclooxygenase-2. The nuclear translocation of nuclear factor (NF)-κB (p65 and p50) was also blocked by BN82002 in RAW265.7 cells stimulated by LPS. According to reporter gene assay performed with NF-κB construct, BN82002 clearly reduced increased level of luciferase activity mediated by transcription factor NF-κB in LPS-treated RAW264.7 cells and in MyD88- and AKT2-overexpressing HEK293 cells. However, BN82002 did not inhibit NF-κB activity in AKT1- or IKKβ-overexpressing HEK293 cells. NF-κB upstream signaling events specifically targeted AKT2 but had no effect on AKT1. The specific target of BN82002 was Tyr-178 in AKT2. BN82002 bound to Tyr-178 and interrupted the kinase activity of AKT2, according to a cellular thermal shift assay analysis of the interaction of BN82002 with AKT2 and an AKT2 mutant (Tyr-178 mutated to Ala; AKT2 Y178A). These results suggest that BN82002 could reduce inflammatory pathway by controlling NF-κB pathway and specifically targeting AKT2.

Structural and chemical insights into the covalent-allosteric inhibition of the protein kinase Akt

The Ser/Thr kinase Akt (Protein Kinase B/PKB) is a master switch in cellular signal transduction pathways. Its downstream signaling influences cell proliferation, cell growth, and apoptosis, rendering Akt a prominent drug target. The unique activation mechanism of Akt involves a change of the relative orientation of its N-terminal pleckstrin homology (PH) and the kinase domain and makes this kinase suitable for highly specific allosteric modulation. Here we present a unique set of crystal structures of covalent-allosteric interdomain inhibitors in complex with full-length Akt and report the structure-based design, synthesis, biological and pharmacological evaluation of a focused library of these innovative inhibitors.

Highly-expressed P2X7 receptor promotes growth and metastasis of human HOS/MNNG osteosarcoma cells via PI3K/Akt/GSK3β/β-catenin and mTOR/HIF1α/VEGF signaling

The P2X7 receptor, an ATP‐gated ion channel, is critical for cancer cell growth, invasiveness, and angiogenesis. Previous studies indicate that P2X7 regulates osteoblast proliferation and osteodeposition and that high P2X7 expression has a pro‐growth effect in osteosarcoma. However, how it functions in osteosarcoma cell growth and metastasis is not clear. Thus, we elucidated molecular mechanisms of P2X7‐dependent positive regulation of osteosarcoma cell proliferation, invasion, migration, epithelial to mesenchymal transition (EMT), and angiogenesis using in vitro and in vivo models. We confirm that P2X7 is highly‐expressed in human osteosarcoma tumor tissues and HOS/MNNG, MG63, U2OS, SW1353 and SAOS‐2 cell lines. P2X7 receptor stimulation enhanced HOS/MNNG and SAOS‐2 cell proliferation, migration and invasion; but knockdown of P2X7 expression or receptor inhibition had opposite effects. P2X7 positively regulated glycogen content, epithelial to mesenchymal transition and stemness of HOS/MNNG cells. P2X7 activation promoted PI3K/Akt/GSK3β/β‐catenin and mTOR/HIF1α/VEGF signaling, thereby mediating pro‐tumor effects of osteosarcoma cells. Consistent with data from in vitro experiments, systemic administration of P2X7 agonist induced tumor growth, metastasis and tumor‐associated bone destruction in osteosarcoma‐bearing nude mice, whereas a P2X7 antagonist reversed these effects. Thus, the P2X7 receptor participates in regulation of osteosarcoma growth and metastasis and we offer evidence that P2X7 may be a promising therapeutic target for treating osteosarcoma.

What's new?

The ATP‐gated ion channel receptor P2X7 is increasingly recognized as a tumor‐promoting factor. In this study, P2X7 was found to be overexpressed in human osteosarcoma tissues and cells, with its activation enhancing osteosarcoma cell proliferation, migration, and invasion. P2X7 activation further induced epithelial‐mesenchymal transition (EMT), affected the stemness of osteosarcoma cells, and augmented angiogenesis. Experiments in mice showed that P2X7 also induces osteosarcoma‐associated bone destruction. Opposing effects were observed upon P2X7 inhibition. P2X7 activity was influenced in part by PI3K/Akt/GSK3β/β‐catenin and mTOR/HIF1α/VEGF signaling pathways. The data identify P2X7 as a target for the development of novel therapeutics against osteosarcoma.

AKT as a Therapeutic Target for Cancer

Many cellular processes in cancer are attributed to kinase signaling networks. V-akt murine thymoma viral oncogene homolog (AKT) plays a major role in the PI3K/AKT signaling pathways. AKT is activated by PI3K or phosphoinositide-dependent kinases (PDK) as well as growth factors, inflammation, and DNA damage. Signal transduction occurs through downstream effectors such as mTOR, glycogen synthase kinase 3 beta (GSK3β), or forkhead box protein O1 (FOXO1). The abnormal overexpression or activation of AKT has been observed in many cancers, including ovarian, lung, and pancreatic cancers, and is associated with increased cancer cell proliferation and survival. Therefore, targeting AKT could provide an important approach for cancer prevention and therapy. In this review, we discuss the rationale for targeting AKT and also provide details regarding synthetic and natural AKT-targeting compounds and their associated studies.

Allosteric Regulation of Protein Kinases Downstream of PI3-Kinase Signalling

Allostery is a basic principle that enables proteins to process and transmit cellular information. Protein kinases evolved allosteric mechanisms to transduce cellular signals to downstream signalling components or effector molecules. Protein kinases catalyse the transfer of the terminal phosphate from ATP to protein substrates upon specific stimuli. Protein kinases are targets for the development of small molecule inhibitors for the treatment of human diseases. Drug development has focussed on ATP-binding site, while there is increase interest in the development of drugs targeting alternative sites, i.e. allosteric sites. Here, we review the mechanism of regulation of protein kinases, which often involve the allosteric modulation of the ATP-binding site, enhancing or inhibiting activity. We exemplify the molecular mechanism of allostery in protein kinases downstream of PI3-kinase signalling with a focus on phosphoinositide-dependent protein kinase 1 (PDK1), a model kinase where small compounds can allosterically modulate the conformation of the kinase bidirectionally.

The Akt pathway in oncology therapy and beyond (Review)

Protein kinase B (Akt), similar to many other protein kinases, is at the crossroads of cell death and survival, playing a pivotal role in multiple interconnected cell signaling mechanisms implicated in cell metabolism, growth and division, apoptosis suppression and angiogenesis. Akt protein kinase displays important metabolic effects, among which are glucose uptake in muscle and fat cells or the suppression of neuronal cell death. Disruptions in the Akt-regulated pathways are associated with cancer, diabetes, cardiovascular and neurological diseases. The regulation of the Akt signaling pathway renders Akt a valuable therapeutic target. The discovery process of Akt inhibitors using various strategies has led to the identification of inhibitors with great selectivity, low side-effects and toxicity. The usefulness of Akt emerges beyond cancer therapy and extends to other major diseases, such as diabetes, heart diseases, or neurodegeneration. This review presents key features of Akt structure and functions, and presents the progress of Akt inhibitors in regards to drug development, and their preclinical and clinical activity in regards to therapeutic efficacy and safety for patients.

Mechanisms of resistance in estrogen receptor positive breast cancer: overcoming resistance to tamoxifen/aromatase inhibitors

Several mechanisms of resistance have been identified, underscoring the complex nature of estrogen receptor (ER) signaling and the many connections between this pathway and other essential signaling pathways in breast cancer cells. Many therapeutic targets of cell signaling and cell cycle pathways have met success with endocrine therapy and remain an ongoing area of investigation. This review focuses on two major pathways that have recently emerged as important opportunities for therapeutic intervention in endocrine resistant breast tumors: PI3K/AKT/mTOR cell signaling and cyclinD1/cyclin-dependent kinase 4/6 cell cycle pathways. Additionally, we highlight individual and combination strategies in current clinical trials that target these pathways and others under investigation for the treatment of ER positive breast cancer.

Targeting the PI3K pathway in cancer: are we making headway?

The PI3K-AKT-mTOR pathway is one of the most frequently dysregulated pathways in cancer and, consequently, more than 40 compounds that target key components of this signalling network have been tested in clinical trials involving patients with a range of different cancers. The clinical development of many of these agents, however, has not advanced to late-phase randomized trials, and the antitumour activity of those that have been evaluated in comparative prospective studies has typically been limited, or toxicities were found to be prohibitive. Nevertheless, the mTOR inhibitors temsirolimus and everolimus and the PI3K inhibitors idelalisib and copanlisib have been approved by the FDA for clinical use in the treatment of a number of different cancers. Novel compounds with greater potency and selectivity, as well as improved therapeutic indices owing to reduced risks of toxicity, are clearly required. In addition, biomarkers that are predictive of a response, such as PIK3CA mutations for inhibitors of the PI3K catalytic subunit α isoform, must be identified and analytically and clinically validated. Finally, considering that oncogenic activation of the PI3K-AKT-mTOR pathway often occurs alongside pro-tumorigenic aberrations in other signalling networks, rational combinations are also needed to optimize the effectiveness of treatment. Herein, we review the current experience with anticancer therapies that target the PI3K-AKT-mTOR pathway.

Identification of 4-phenylquinolin-2(1H)-one as a specific allosteric inhibitor of Akt

Akt plays a major role in tumorigenesis and the development of specific Akt inhibitors as effective cancer therapeutics has been challenging. Here, we report the identification of a highly specific allosteric inhibitor of Akt through a FRET-based high-throughput screening, and characterization of its inhibitory mechanism. Out of 373,868 compounds screened, 4-phenylquinolin-2(1H)-one specifically decreased Akt phosphorylation at both T308 and S473, and inhibited Akt kinase activity (IC50 = 6 µM) and downstream signaling. 4-Phenylquinolin-2(1H)-one did not alter the activity of upstream kinases including PI3K, PDK1, and mTORC2 as well as closely related kinases that affect cell proliferation and survival such as SGK1, PKA, PKC, or ERK1/2. This compound inhibited the proliferation of cancer cells but displayed less toxicity compared to inhibitors of PI3K or mTOR. Kinase profiling efforts revealed that 4-phenylquinolin-2(1H)-one does not bind to the kinase active site of over 380 human kinases including Akt. However, 4-phenylquinolin-2(1H)-one interacted with the PH domain of Akt, apparently inducing a conformation that hinders S473 and T308 phosphorylation by mTORC2 and PDK1. In conclusion, we demonstrate that 4-phenylquinolin-2(1H)-one is an exquisitely selective Akt inhibitor with a distinctive molecular mechanism, and a promising lead compound for further optimization toward the development of novel cancer therapeutics.

Withaferin A Inhibits Prostate Carcinogenesis in a PTEN-deficient Mouse Model of Prostate Cancer

We recently demonstrated that AKT activation plays a role in prostate cancer progression and inhibits the pro-apoptotic function of FOXO3a and Par-4. AKT inhibition and Par-4 induction suppressed prostate cancer progression in preclinical models. Here, we investigate the chemopreventive effect of the phytonutrient Withaferin A (WA) on AKT-driven prostate tumorigenesis in a Pten conditional knockout (Pten-KO) mouse model of prostate cancer. Oral WA treatment was carried out at two different doses (3 and 5 mg/kg) and compared to vehicle over 45 weeks. Oral administration of WA for 45 weeks effectively inhibited primary tumor growth in comparison to vehicle controls. Pathological analysis showed the complete absence of metastatic lesions in organs from WA-treated mice, whereas discrete metastasis to the lungs was observed in control tumors. Immunohistochemical analysis revealed the down-regulation of pAKT expression and epithelial-to-mesenchymal transition markers, such as β-catenin and N-cadherin, in WA-treated tumors in comparison to controls. This result corroborates our previous findings from both cell culture and xenograft models of prostate cancer. Our findings demonstrate that the daily administration of a phytonutrient that targets AKT activation provides a safe and effective treatment for prostate cancer in a mouse model with strong potential for translation to human disease.

Recent progress towards clinically relevant ATP-competitive Akt inhibitors

The frequency of PI3K/Akt/mTOR (PAM) Pathway mutations in human cancers sparked interest to determine if the pathway is druggable. The modest clinical benefit observed with mTOR rapalogs (temsirolimus and everolimus) provided further motivation to identify additional nodes of pathway inhibition that lead to improved clinical benefit. Akt is a central signaling node of the PAM pathway and could be an ideal target for improved pathway inhibition. Furthermore, inhibitors of Akt may be especially beneficial in tumors with Akt1 mutations. Recently, multiple ATP-competitive Akt inhibitors have been identified and are currently in clinical development. This review details the medicinal chemistry efforts towards identification of these molecules, highlights relevant preclinical data supporting clinical evaluation, and summarizes current clinical development plans.

Maximising the potential of AKT inhibitors as anti-cancer treatments

PI3K/AKT signalling is commonly disrupted in human cancers, with AKT being a central component of the pathway, influencing multiple processes that are directly involved in tumourigenesis. Targeting AKT is therefore a highly attractive anti-cancer strategy with multiple AKT inhibitors now in various stages of clinical development. In this review, we summarise the role and regulation of AKT signalling in normal cellular physiology. We highlight the mechanisms by which AKT signalling can be hyperactivated in cancers and discuss the past, present and future clinical strategies for AKT inhibition in oncology.