Present and future of PI3K pathway inhibition in cancer: perspectives and limitations

Prevalence and Prognostic Significance of PIK3CA Mutation and CNV Status and Phosphorylated AKT Expression in Patients With Cervical Cancer Treated With Primary Surgery

Currently, there are limited and conflicting reports on the prognostic utility of PIK3CA and associated pathway markers for cervical cancers treated with primary surgical management. Moreover, current studies are lacking complete characterization of adjuvant treatment with RT and/or chemotherapy. We aimed to document the prevalence, clinicopathologic, adjuvant treatment details, and prognostic value of PI3K/AKT pathway mutations and copy number variation and phosphorylated AKT status in patients with cervical cancers treated with primary surgery. A clinicopathologic review was performed on a retrospective cohort of 185 patients with cervical cancer, treated with primary surgery at a single tertiary institution. Next-generation sequencing and digital PCR was used to determine PI3K/AKT pathway mutational status and PIK3CA copy number variation, respectively, and fluorescent immunohistochemistry measured phosphorylated AKT expression. In all, 179 of 185 (96.8%) of tumors were successfully sequenced; 48 (26.8%) were positive for PI3K/AKT pathway mutations-the majority (n=37, 77.1%) PIK3CA mutations. PIK3CA mutation was associated with pathologically positive lymph nodes [12 (32%) vs. 22 (16%); P =0.022] and indication for postoperative chemoradiotherapy [17 (45.9%) vs. 32 (22.5%); P =0.004]. On multivariable analysis, PIK3CA status was not associated with overall survival ( P =0.103) or progression-free survival ( P =0.240) at 5 yrs, nor was PIK3CA copy number variation status. phosphorylated AKT ≤ median significantly predicted for progression-free survival [multivariable hazard ratio 0.39 (0.17-0.89; P =0.025)] but not overall survival ( P =0.087). The correlation of PIK3CA with pathologic positive lymph node status yet lack of association with survival outcomes may be due to the use of adjuvant postoperative therapy. PIK3CA assessment before radical hysterectomy may help identify patients with a higher risk of node-positive disease.

Design, Synthesis and Molecular Docking Studies of Pyrazoline Derivatives as PI3K Inhibitors

AIM

Design, synthesis and molecular docking studies of quinoline/naphthalene containing pyrazoline derivatives as PI3K inhibitors.

BACKGROUND

Phosphatidylinositol 3-kinases (PI3Ks) belong to the family of enzymes, which are associated with various cellular functions such as cell growth, proliferation, differentiation etc. Overexpression or any changes in these functions may result in various abnormalities, which in turn cause cancer.

OBJECTIVES

To perform synthesis and molecular docking studies of quinoline/naphthalene containing pyrazoline derivatives as PI3K inhibitors.

METHODS

2-Chloroquinoline-3-carbaldehyde was synthesized by a reaction of acetanilide and POCl3. The latter was reacted with substituted acetophenones to synthesize chalcones, which were reacted with substituted phenyl hydrazines to yield pyrazoline derivatives (Series I). Similarly, pchloro benzaldehyde was reacted with 2-acetonapthone to yield chalcone with substituted phenyl hydrazines to yield pyrazoline derivatives (Series II).

RESULTS

The synthetic compounds were subjected to molecular modelling experiments using Schrodinger 2016 software and evaluated in silico for their PI3K binding affinities. All the compounds had better docking scores than AMG-319 (-4.36 Kcal/mol) and comparable docking scores with PI-103 (-6.83 Kcal/mol).

CONCLUSION

Compounds 5 and 3 had the best docking scores (-7.85 and -7.17 Kcal/mol, respectively). The synthesized compounds have better docking scores than the reference drug AMG-319. As a result, they might be used as lead molecules in investigating PI3K inhibitors.

Inhibitors of the PI3K/AKT/mTOR pathway in human malignancies; trend of current clinical trials

The phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway regulates proliferation, survival and metabolism, and its dysregulation is one of the most frequent oncogenic events across human malignancies. Over the last two decades, there has been significant focus on the clinical development of PI3K pathway inhibitors. More than 40 different inhibitors of this axis have reached various stages of clinical trials, but only a few of them have been approved by the Food and Drug Administration (FDA) for cancer treatment. These clinical results, however, could be improved given the importance of PI3K signaling in cancer and its role in linking cancer growth with metabolism. In this systematic review, after a glance at PI3K/AKT/mTOR pathway and its different inhibitors, we retrieved registered clinical trials evaluating the efficacy and safety of PI3K/AKT/mTOR inhibitors on Clinicaltrials.gov. Following the extraction of the data, finally we analyzed 2250 included studies in multiple steps, beginning with an overview and moving on to the details about type of malignancies, inhibitors, and treatment strategies. We also took a closer look at more than 100 phase III-IV clinical trials to pinpoint promising therapies, hoping that presenting a comprehensive picture of current clinical trials casts a flash of light on what remains to be done in future clinical trials of PI3K/AKT/mTOR inhibitors in human malignancies.

Stellettin B Sensitizes Glioblastoma to DNA-Damaging Treatments by Suppressing PI3K-Mediated Homologous Recombination Repair

Glioblastoma (GBM) is the most aggressive type of cancer. Its current first-line postsurgery regimens are radiotherapy and temozolomide (TMZ) chemotherapy, both of which are DNA damage-inducing therapies but show very limited efficacy and a high risk of resistance. There is an urgent need to develop novel agents to sensitize GBM to DNA-damaging treatments. Here it is found that the triterpene compound stellettin B (STELB) greatly enhances the sensitivity of GBM to ionizing radiation and TMZ in vitro and in vivo. Mechanistically, STELB inhibits the expression of homologous recombination repair (HR) factors BRCA1/2 and RAD51 by promoting the degradation of PI3Kα through the ubiquitin-proteasome pathway; and the induced HR deficiency then leads to augmented DNA damage and cell death. It is further demonstrated that STELB has the potential to rapidly penetrate the blood-brain barrier to exert anti-GBM effects in the brain, based on zebrafish and nude mouse orthotopic xenograft tumor models. The study provides strong evidence that STELB represents a promising drug candidate to improve GBM therapy in combination with DNA-damaging treatments.

Computational study reveals substituted benzimidazole derivatives' binding selectivity to PI3Kδ and PI3Kγ

Phosphatidylinositol 3-kinase (PI3K) is a key regulatory kinase in the PI3K/AKT/mTOR signaling pathway, which is involved in the regulation of cell proliferation, differentiation, apoptosis, and angiogenesis. Class IA PI3K isoforms γ and δ share a highly homologous ATP binding site and are distinguished by only a few residues around the binding site. Subtype-selective inhibitors have been proven to have great advantages in tumor treatment. Preliminary studies have obtained PI3K inhibitors bearing a benzimidazole structural motif with a certain selectivity for PI3Kδ and PI3Kγ subtypes. On this basis, we investigated the selective inhibitory mechanism of PI3Kδ and PI3Kγ using four developed inhibitors via molecular docking, molecular dynamics, binding free energy calculations, and residue energy decomposition. This study could provide references for the further development of PI3K-isoform-selective inhibitors.

The PI3K/Akt/mTOR signaling pathway in gastric cancer; from oncogenic variations to the possibilities for pharmacologic interventions

Genetic and epigenetic alterations have been under concentrated investigations for many years in order to unearth the molecules regulating human cancer pathogenesis. However, the identification of a wide range of dysregulated genes and their protein products has raised a question regarding how the results of this large collection of alterations could converge into a formation of one malignancy. The answer may be found in the signaling cascades that regulate the survival and metabolism of the cells. Aberrancies of each participant molecule of such cascades may well result in augmented viability and unlimited proliferation of cancer cells. Among various signaling pathways, the phosphatidylinositol-3-kinase (PI3K) axis has been shown to be activated in about one-third of human cancers. One of the malignancies that is mostly affected by this axis is gastric cancer (GC), one of the most fatal cancers worldwide. In the present review, we aimed to illustrate the significance of the PI3K/Akt/mTOR axis in the pathogenesis of GC and also provided a wide perspective about the application of the inhibitors of this axis in the therapeutic strategies of this malignancy.

Structural basis for tailor-made selective PI3K α/β inhibitors: a computational perspective

PI3K α and β are Class IA PI3K isoforms that share a highly homologous ATP binding site, differing only in a few residues around the binding site.

Overcoming Wnt-β-catenin dependent anticancer therapy resistance in leukaemia stem cells

Leukaemia stem cells (LSCs) underlie cancer therapy resistance but targeting these cells remains difficult. The Wnt-β-catenin and PI3K-Akt pathways cooperate to promote tumorigenesis and resistance to therapy. In a mouse model in which both pathways are activated in stem and progenitor cells, LSCs expanded under chemotherapy-induced stress. Since Akt can activate β-catenin, inhibiting this interaction might target therapy-resistant LSCs. High-throughput screening identified doxorubicin (DXR) as an inhibitor of the Akt-β-catenin interaction at low doses. Here we repurposed DXR as a targeted inhibitor rather than a broadly cytotoxic chemotherapy. Targeted DXR reduced Akt-activated β-catenin levels in chemoresistant LSCs and reduced LSC tumorigenic activity. Mechanistically, β-catenin binds multiple immune-checkpoint gene loci, and targeted DXR treatment inhibited expression of multiple immune checkpoints specifically in LSCs, including PD-L1, TIM3 and CD24. Overall, LSCs exhibit distinct properties of immune resistance that are reduced by inhibiting Akt-activated β-catenin. These findings suggest a strategy for overcoming cancer therapy resistance and immune escape.

Supramolecular Polysaccharide Nanotheranostics that Inhibit Cancer Cells Growth and Monitor Targeted Therapy Response

Targeted anticancer therapies directed against specific molecular drivers of tumors are emerging as effective treatment strategies, however, monitoring their response is still challenging. Current clinical imaging techniques that measure either morphological or metabolic changes in the tumor are not always indicative of clinical outcome due to delayed or variable responses. Here, dual-stage polysaccharide-based supramolecular nanotheranostics (SPN) were designed that enable co-delivery of kinase inhibitor and an activatable imaging probe.

Methods: The SPNs were prepared by supramolecular assembly of two components, polysaccharide construct conjugated with kinase inhibitor-function activatable probe and kinase inhibitor- β-cyclodextrin conjugate. Physiochemical characterization of SPNs including size, stability, zeta potential and pH-responsiveness of the assembly was performed. The efficacy of SPNs in inducing cancer cell death by inhibition of kinase signaling and imaging the response was evaluated in murine BRAFV^600E melanoma (D4M) and triple-negative breast cancer (4T1) cell lines. Finally, the in vivo efficacy was investigated in D4M melanoma tumor model.

Results: The polysaccharide-constructs along with kinase inhibitor- β-cyclodextrin conjugates self-assemble to produce SPNs of around 200 nm in diameter and were stable for over a week under physiologically relevant conditions. The SPNs exhibited enhanced cytotoxic effect and significant inhibition of kinase signaling as compared to the free inhibitor. In vitro imaging studies confirmed their enzyme-activatable therapy response tracking abilities both in cancer cells and tumor spheroids. Furthermore, SPN treated mice exhibited better tumor growth inhibition as compared to the control groups and therapy response could be imaged at both early (24-48h) and later time points.

Conclusion: These findings demonstrate that the supramolecular polysaccharide nanotheranostics can not only inhibit kinase signaling pathway in aggressive tumor, but also monitor targeted therapy response early.

For Better or Worse: The Potential for Dose Limiting the On-Target Toxicity of PI 3-Kinase Inhibitors

The hyper-activation of the phosphoinositide (PI) 3-kinase signaling pathway is a hallmark of many cancers and overgrowth syndromes, and as a result, there has been intense interest in the development of drugs that target the various isoforms of PI 3-kinase. Given the key role PI 3-kinases play in many normal cell functions, there is significant potential for the disruption of essential cellular functions by PI 3-kinase inhibitors in normal tissues; so-called on-target drug toxicity. It is, therefore, no surprise that progress within the clinical development of PI 3-kinase inhibitors as single-agent anti-cancer therapies has been slowed by the difficulty of identifying a therapeutic window. The aim of this review is to place the cellular, tissue and whole-body effects of PI 3-kinase inhibition in the context of understanding the potential for dose limiting on-target toxicities and to introduce possible strategies to overcome these.

Joint action of miR-126 and MAPK/PI3K inhibitors against metastatic melanoma

Emerging data support the rationale of combined therapies in advanced melanoma. Specifically, the combined use of drugs with different mechanisms of action can reduce the probability of selecting resistant clones. To identify agents active against melanoma cells, we screened a library of 349 anti‐cancer compounds, currently in clinical use or trials, and selected PIK‐75, an inhibitor of the phosphatidylinositol 3‐kinase/protein kinase B (PI3K/AKT) pathway, as the ‘top active’ drug. PIK‐75 was then used alone or in combination with vemurafenib, the first BRAF inhibitor approved for patients with melanoma harboring BRAF mutations. We identified a combined dose of PIK‐75 and vemurafenib that inhibited both the PI3K/AKT and mitogen‐activated protein kinase pathways, thereby overcoming any compensatory activation. In view of the important tumor suppressor function induced by restoring expression of microRNA (miR)‐126 in metastatic melanoma cells, we examined whether miR‐126 has a synergistic role when included in a triple combination alongside PIK‐75 and vemurafenib. We found that enforced expression of miR‐126 (which alone can reduce tumorigenicity) significantly increased PIK‐75 activity when used as either a single agent or in combination with vemurafenib. Interestingly, PIK‐75 proved to be effective against early passage cell lines derived from patients’ biopsies and on melanoma cell lines resistant to either vemurafenib or dabrafenib, thus suggesting that it potentially has the capability to overcome drug resistance. Finally, the synergistic role played by miR‐126 in combination with vemurafenib and/or PIK‐75 was demonstrated in vivo in mouse xenograft models, in which tumor growth inhibition was associated with increased apoptosis. These results not only show the efficacy of PIK‐75 and vemurafenib co‐treatment but also indicate that restoration of miR‐126 expression in advanced melanoma can enhance their antitumor activity, which may possibly allow dose reduction to decrease adverse events without reducing the therapeutic benefits.

Introduction of pyrrolidineoxy or piperidineamino group at the 4-position of quinazoline leading to novel quinazoline-based phosphoinositide 3-kinase delta (PI3Kδ) inhibitors

Phosphoinositide 3-kinase Delta (PI3Kδ) plays a key role in B-cell signal transduction and inhibition of PI3Kδ was confirmed to have clinical benefit in certain types of activation of B-cell malignancies. Herein, we reported a novel series of 4-pyrrolidineoxy or 4-piperidineamino substituted quinazolines, showing potent PI3Kδ inhibitory activities. Among these compounds, 12d, 14b and 14c demonstrated higher potency against PI3Kδ with the half maximal inhibitory concentration (IC50) values of 4.5, 3.0, and 3.9 nM, respectively, which were comparable to idelalisib (IC50 = 2.7 nM). The further PI3K isoforms selectivity evaluation showed that compounds 12d, 14b and 14c have excellent PI3Kδ selectivity over PI3Kα, PI3Kβ, and PI3Kγ. Moreover, compounds 12d, 14b and 14c also displayed different anti-proliferative profiles against a panel of four human B cell lines including Ramos, Raji, RPMI-8226, and SU-DHL-6. The molecular docking simulation indicated several key hydrogen bonding interactions were formed. This study suggests the introduction of pyrrolidineoxy or piperidineamino groups into the 4-position of quinazoline leads to new potent and selective PI3Kδ inhibitors.

Identification of a Potent Phosphoinositide 3-Kinase Pan Inhibitor Displaying a Strategic Carboxylic Acid Group and Development of Its Prodrugs

Activation of the phosphoinositide 3-kinase (PI3K) pathway is a key signaling event in cancer, inflammation, and other proliferative diseases. PI3K inhibitors are already approved for some specific clinical indications, but their systemic on-target toxicity limits their larger use. In particular, whereas toxicity is tolerable in acute treatment of life-threatening diseases, this is less acceptable in chronic conditions. In the past, the strategy to overcome this drawback was to block selected isoforms mainly expressed in leukocytes, but redundancy within the PI3K family members challenges the effectiveness of this approach. On the other hand, decreasing exposure to selected target cells represents a so-far unexplored alternative to circumvent systemic toxicity. In this manuscript, we describe the generation of a library of triazolylquinolones and the development of the first prodrug pan-PI3K inhibitor.

Alternative splicing promotes tumour aggressiveness and drug resistance in African American prostate cancer

Clinical challenges exist in reducing prostate cancer (PCa) disparities. The RNA splicing landscape of PCa across racial populations has not been fully explored as a potential molecular mechanism contributing to race-related tumour aggressiveness. Here, we identify novel genome-wide, race-specific RNA splicing events as critical drivers of PCa aggressiveness and therapeutic resistance in African American (AA) men. AA-enriched splice variants of PIK3CD, FGFR3, TSC2 and RASGRP2 contribute to greater oncogenic potential compared with corresponding European American (EA)-expressing variants. Ectopic overexpression of the newly cloned AA-enriched variant, PIK3CD-S, in EA PCa cell lines enhances AKT/mTOR signalling and increases proliferative and invasive capacity in vitro and confers resistance to selective PI3Kδ inhibitor, CAL-101 (idelalisib), in mouse xenograft models. High PIK3CD-S expression in PCa specimens associates with poor survival. These results highlight the potential of RNA splice variants to serve as novel biomarkers and molecular targets for developmental therapeutics in aggressive PCa.

In prostate cancer tumour aggressiveness can be related to race. Here, the authors identify an alternative RNA splice variant of PIK3CD as a potential mechanism to explain racial disparities in the incidence and aggressiveness of prostate cancer between African American and European American men.

Inhibition of Akt phosphorylation attenuates resistance to TNF-α cytotoxic effects in MCF-7 cells, but not in their doxorubicin resistant derivatives

Objective(s):

Acquisition of TNF-α resistance plays role in the onset and growth of malignant tumors. Previous studies have demonstrated that MCF-7 cell line and its doxorubicin resistant variant MCF-7/Adr are resistant against the cytotoxic effects of TNF-α. In this study, we investigated the role of Akt activation in resistance of MCF-7 and MCF-7/Adr against TNF-α cytotoxicity.

Materials and Methods:

The role of Akt activation in TNF-α cytotoxicity was investigated by MTT cell viability assay following treatment of the cells with the chemical inhibitor of Akt activation with or without TNF-α treatment. Phosphorylation of Akt at Ser473 before and after 72 hr TNF-α treatment was also determined by western blot.

Results:

TNF-α treatment led to enhancement of Akt Ser473 phosphorylation. Treatment of MCF-7 cells with TNF-α along with Akt-inhibitor agent, tricribine, attenuated Akt Ser473 phosphorylation and sensitized these cells to the cytotoxic effects of TNF-α in a dose and time dependent manner while tricribine treatment did not cause any significant cytotoxicity in MCF-7/Adr cells alone or in combination with TNF-α.

Conclusion:

These results demonstrate that Akt phosphorylation plays pivotal role in the resistance of MCF-7 cells against TNF-α-induced cytotoxicity while it might play no significant role in the resistance of MCF-7/Adr cells against TNF-α.

Molecular explorations of substituted 2-(4-phenylquinolin-2-yl) phenols as phosphoinositide 3-kinase inhibitors and anticancer agents

PURPOSE

Substituted 2-(4-phenylquinolin-2-yl) phenols (PQPDs) emerged as the inhibitors of phosphoinositide 3-kinase (PI3K) and anticancer agents.

METHOD

PI3K inhibition was assessed by competitive ELISA. Anticancer activity was evaluated against breast cancer (MCF-7), skin cancer (G-361), and colon cancer (HCT 116) cell lines.

RESULTS

In PI3 Kinase assay, PQPDs 4c, 4d, and 4k were inactive with IC₅₀ >5 µM. IC₅₀ for 4a, 4b, 4f-h, and 4j was ≥0.05 µM. Rest PQPDs IC₅₀ was <1.0 µM. Anticancer activity found selective toward breast cancer (MCF-7); 4a, 4b, and 4j were showed excellent inhibitory (73.95, 68.36, and 70.06%) and IC₅₀ 1.16 µM (4a), 2.07 µM (4b), 1.021 µM (4f) and 1.981 µM (4j) while the standard (Doxorubicin) found with IC₅₀ 1.812 µM (72% inhibition). PQPDs were docked into the active site of PI3 Kinase p110α (PDB ID: 2RD0). Docking results suggested the hydrophobic interactions in PI3K binding pocket conquered affinity of the most favorable binding ligands [4a, 4b: inhibitory constant (ki) = 53.33, 41.23 pM].

CONCLUSION

PI3K assay and cancer cell line experimental results ensured that the inhibitory and anticancer activity potentials of PQPDs are more selective toward breast cancer treatments. PQPDs 4a, 4b, 4f, 4g, and 4j were displayed potent PI3 Kinase and anticancer activities. SAR studies demonstrated PQPDs as the PI3K precise inhibitors with the impending to treat various cancers.

Evaluation of MicroRNAs Regulating Anoikis Pathways and Its Therapeutic Potential

Dysregulation of microRNAs (miRNAs) has been implicated in almost every known survival mechanisms utilized by cancer cells. One of such mechanisms, anoikis resistance, plays a pivotal role in enabling metastasis by allowing cancer cells to circumvent cell death induced by lack of attachment. Understanding how miRNAs regulate the various anoikis pathways has become the research question of increasing number of studies published in the past years. Through these studies, a growing list of miRNAs has been identified to be important players in promoting either anoikis or resistance to anoikis. In this review, we will be focusing on these miRNAs and how the findings from those studies can contribute to novel therapeutic strategies against cancer progression. We will be examining miRNAs that have been found to promote anoikis sensitivity in numerous cancer types followed by miRNAs that inhibit anoikis. In addition, we will also be taking a look at major signaling pathways involved in the action of the each of these miRNAs to gain a better understanding on how miRNAs regulate anoikis.

The Guareschi Pyridine Scaffold as a Valuable Platform for the Identification of Selective PI3K Inhibitors

A novel series of 4-aryl-3-cyano-2-(3-hydroxyphenyl)-6-morpholino-pyridines have been designed as potential phosphatidylinositol-3-kinase (PI3K) inhibitors. The compounds have been synthesized using the Guareschi reaction to prepare the key 4-aryl-3-cyano-2,6-dihydroxypyridine intermediate. A different selectivity according to the nature of the aryl group has been observed. Compound 9b is a selective inhibitor against the PI3Kα isoform, maintaining a good inhibitory activity. Docking studies were also performed in order to rationalize its profile of selectivity.

NSK-01105, a novel sorafenib derivative, inhibits human prostate tumor growth via suppression of VEGFR2/EGFR-mediated angiogenesis

The purpose of this study is to investigate the anti-angiogenic activities of NSK-01105, a novel sorafenib derivative, in in vitro, ex vivo and in vivo models, and explore the potential mechanisms. NSK-01105 significantly inhibited vascular endothelial growth factor (VEGF)-induced migration and tube formation of human umbilical vein endothelial cells at non-cytotoxic concentrations as shown by wound-healing, transwell migration and endothelial cell tube formation assays, respectively. Cell viability and invasion of LNCaP and PC-3 cells were significantly inhibited by cytotoxicity assay and matrigel invasion assay. Furthermore, NSK-01105 also inhibited ex vivo angiogenesis in matrigel plug assay. Western blot analysis showed that NSK-01105 down-regulated VEGF-induced phosphorylation of VEGF receptor 2 (VEGFR2) and the activation of epidermal growth factor receptor (EGFR). Tumor volumes were significantly reduced by NSK-01105 at 60 mg/kg/day in both xenograft models. Immunohistochemical staining demonstrated a close association between inhibition of tumor growth and neovascularization. Collectively, our results suggest a role of NSK-01105 in treatment for human prostate tumors, and one of the potential mechanisms may be attributed to anti-angiogenic activities.

Structure and ligand-based design of mTOR and PI3-kinase inhibitors leading to the clinical candidates VS-5584 (SB2343) and SB2602

Phosphoinositide 3-kinases (PI3Ks) and the mammalian target of rapamycin (mTOR) act as critical effectors in a commonly deregulated cell signaling pathway in human cancers. The abnormal activation of the PI3K/mTOR pathway has been shown to play a role in initiation, progression, and metastasis of human tumors. Being one of the most frequently activated pathways in cancer, much effort has been directed toward inhibition of the PI3K/mTOR pathway as a novel oncology therapy. Previous work by a number of groups has revealed several selective PI3K and dual mTOR/PI3K inhibitors. However, there are few reports of therapeutic agents with a pan-PI3K/mTOR inhibitory profile within a narrow concentration range. We therefore initiated a drug discovery project with the aim of discovering dual mTOR/PI3K inhibitors which would equipotently inhibit the 4 isoforms of PI3K, α, β, γ, and δ, and mTOR a compelling profile for powerful blockage of the PI3K/mTOR pathway. A pharmacophore model was generated and used for designing a series of novel compounds, based on a purine scaffold, which potently inhibited mTOR and PI3Ks. These compounds contained a phenol headgroup essential for binding to the target proteins. Early efforts concentrated on finding replacements for the phenol as it was rapidly conjugated resulting in a short half-life in vivo. Compounds with a variety of headgroups were docked into the PI3Kα and mTOR ATP-binding sites, and aminopyrimidine and aminopyrazine were found to make excellent phenol replacements. Further structure guided optimization of side chains in the 8- and 9-positions of the purine resulted in potent inhibitors with good PKDM properties. As the PI3 kinases play a role in insulin signaling, it is believed that targeting mTOR selectively may give the benefit of blocking the AKT-pathway while avoiding the potential side effects associated with PI3K inhibition. As a result we designed a further series of selective mTOR kinase inhibitors. The project was successfully concluded by progressing both a dual mTOR/PI3K inhibitor, SB2343, and a selective mTOR inhibitor, SB2602, into preclinical development. SB2343 has since entered phase 1 clinical development as VS-5584.

TRAIL combinations: The new 'trail' for cancer therapy (Review)

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) therapy is anticipated to be one of the most effective cancer treatments. However, resistance to TRAIL therapy remains a challenge facing the development of anticancer strategies. To circumvent this problem, TRAIL combinations have been experimented with for over ten years to induce synergism or sensitize resistant cancer cells. By analyzing the signaling pathways triggered by these combinations, this review has defined a set of core targets for novel combinatorial treatments. The review suggests specific pathways to be targeted together with TRAIL for more efficient treatment, including cellular FLICE inhibitory protein and its downstream survival factors, the Bcl-2 family and other prominent targets. The suggested pathways provide new avenues for more effective TRAIL-based cancer therapy.

Methods to measure the enzymatic activity of PI3Ks

Phosphoinositide-3-kinase (PI3K) signaling has been implicated in a panoply of cellular responses including survival, proliferation, protein synthesis, migration, and vesicular trafficking. In addition, alterations in the enzymatic activity of PI3Ks have been involved in the pathogenesis of multiple diseases, ranging from cancer to chronic inflammation. The emerging interest in PI3K as a pharmacological target has prompted the development of several molecules with inhibitory activity. In this context, the quantification of the second messenger generated by PI3Ks, phosphoinositide-3-phosphate, offers an opportunity to directly test variations in the lipid kinase activity of PI3K in physiological as well as pathological conditions. Here, we will describe common methods to measure the lipid kinase activity of PI3K in vitro and new techniques to follow the production of phosphoinositide-3-phosphate in vivo. These methods are relevant to study the alterations of the PI3K systems at the interface between signaling and oncometabolism.

DW09849, a selective phosphatidylinositol 3-kinase (PI3K) inhibitor, prevents PI3K signaling and preferentially inhibits proliferation of cells containing the oncogenic mutation p110α (H1047R)

Phosphatidylinositol 3-kinase, α isoform (PI3Kα) plays essential roles in cell metabolism, growth, and proliferation and has been validated as a promising anticancer target. In an effort to search for new PI3Kα-selective inhibitors, DW series compounds were designed and synthesized aiming to reduce the off-target effects of their parent compound PIK-75 [2-methyl-5-nitro-1-benzenesulfonic acid 2-[(6-bromoimidazo[1,2-a]pyridin-3-yl)methylene]-1-methylhydrazide], which was reported to selectively target PI3Kα. A series of compounds named DW series potently inhibited the kinase activity of PI3Kα with little activity against PI3K-related protein kinases and a panel of 15 tyrosine kinases. Similar to PIK-75, DW series compounds were more potent to inhibit PI3Kα among four class I PI3K isoforms, whereas a representative compound DW09849 [(E)-N'-((6-bromoimidazo[1,2-a]pyridin-3-yl)methylene)-N-ethyl-2-methyl-5-nitrobenzohydrazide] displayed distinct binding mode compared with PIK-75. Although DW series compounds inhibited proliferation of rhabdomyosarcoma RH30 cells at elevated 50% inhibitory concentrations (IC50) in comparison with PIK-75, they were more selective than PIK-75 to inhibit PI3K signaling in the cellular context. In particular, DW09849 significantly and persistently blocked PI3K/protein kinase B signaling in RH30 cells, which consequently arrested RH30 cells in the G1 phase. Moreover, DW09849 selectively suppressed the proliferation and clonogenesis of transformed RK3E/HR cells harboring oncogenic mutation of p110α H1047R, as well as a panel of human breast cancer cells containing mutated PI3Kα, which is consistent with the finding that DW09849 demonstrated preference against H1047R mutated PI3Kα in molecular docking stimulation. These results suggest that DW series compounds, especially DW09849, selectively targeting PI3Kα with less off-target effects than PIK-75, provide new clues for the design and discovery of new specific PI3Kα inhibitors for cancer therapy.

Discovery and development of small molecule SHIP phosphatase modulators

Inositol phospholipids play an important role in the transfer of signaling information across the cell membrane in eukaryotes. These signals are often governed by the phosphorylation patterns on the inositols, which are mediated by a number of inositol kinases and phosphatases. The src homology 2 (SH2) containing inositol 5-phosphatase (SHIP) plays a central role in these processes, influencing signals delivered through the PI3K/Akt/mTOR pathway. SHIP modulation by small molecules has been implicated as a treatment in a number of human disease states, including cancer, inflammatory diseases, diabetes, atherosclerosis, and Alzheimer's disease. In addition, alteration of SHIP phosphatase activity may provide a means to facilitate bone marrow transplantation and increase blood cell production. This review discusses the cellular signaling pathways and protein-protein interactions that provide the molecular basis for targeting the SHIP enzyme in these disease states. In addition, a comprehensive survey of small molecule modulators of SHIP1 and SHIP2 is provided, with a focus on the structure, potency, selectivity, and solubility properties of these compounds.

PI3K in cancer-stroma interactions: bad in seed and ugly in soil

Over the past decade the phosphoinositide-3 kinase (PI3K) signaling pathway emerged as an important player for tumor initiation and growth and, currently, PI3K inhibition constitutes a promising therapeutic approach for solid and hematological tumors. Beside its role in tumor cell evolution, PI3K signaling also provides integral functions for noncancerous cells that reside in healthy tissues surrounding the tumor, also referred as tumor microenvironment (TME). This review will address how PI3K signaling participates to the tumorigenic process and discuss the interaction between tumor cells and the surrounding TME, with particular focus on the role of PI3Ks in tumor-associated immune responses, tumor angiogenesis and metastasis formation.

Recent syntheses of PI3K/Akt/mTOR signaling pathway inhibitors

This review focuses on the syntheses of PI3K/Akt/mTOR inhibitors that have been reported outside of the patent literature in the last 5years but is largely centered on synthetic work reported in 2011 and 2012. While focused on syntheses of inhibitors, some information on in vitro and in vivo testing of compounds is also included. Many of these reported compounds are reversible, competitive adenosine triphosphate (ATP) binding inhibitors, so given the structural similarities of many of these compounds to the adenine core, this review presents recent work on inhibitors based on where the synthetic chemistry was started, that is, inhibitor syntheses which started with purines/pyrimidines are followed by inhibitor syntheses which began with pyridines, pyrazines, azoles, and triazines then moves to inhibitors which bear no structural resemblance to adenine: liphagal, wortmannin and quercetin analogs. The review then finishes with a short section on recent syntheses of phosphotidyl inositol (PI) analogs since competitive PI binding inhibitors represent an alternative to the competitive ATP binding inhibitors which have received the most attention.

Inhibition of the PI3 kinase cascade in corticolimbic circuit: temporal and differential effects on contextual fear and extinction

We studied the role of PI3K cascade in the basolateral amygdala (BLA) and the infralimbic region of the medial prefrontal cortex (IL-mPFC), in contextual fear learning and extinction in the rat. To that end, we micro-infused the phosphoinositide-3-kinase (PIK3) inhibitor LY294002 into either the mPFC or the BLA. Infusion of LY294002 into the BLA following fear conditioning was associated with enhanced freezing levels and impaired extinction in the subsequent sessions. Similarly, inhibition of PI3K in the BLA before the retrieval of fear memory was associated with impaired retrieval of the fear memory, which was expressed as reduced freezing levels that persisted over 2 d. In the IL-mPFC, only consolidation of fear extinction was impaired: micro-infusion of PI3K inhibitor following the retrieval of fear was associated with impaired extinction on the following days. These results indicate differences in the temporal parameters of the effects of PI3K inhibition in the IL-mPFC and in the BLA, which suggest differential involvement of these structures in long-term fear and in extinction of fear memory. Our findings provide additional evidence for the critical roles played by PI3K in intact formation of fear memory and in its extinction and add new evidence for a role of PI3K in consolidation of memory of extinction. Better understanding of the differential involvement of the PI3K cascade during acquisition and extinction of fear conditioning in the mPFC-amygdala circuit could potentially contribute to the understanding and treatment of anxiety disorders.

VS-5584, a novel and highly selective PI3K/mTOR kinase inhibitor for the treatment of cancer

Dysregulation of the PI3K/mTOR pathway, either through amplifications, deletions, or as a direct result of mutations, has been closely linked to the development and progression of a wide range of cancers. Moreover, this pathway activation is a poor prognostic marker for many tumor types and confers resistance to various cancer therapies. Here, we describe VS-5584, a novel, low-molecular weight compound with equivalent potent activity against mTOR (IC(50) = 37 nmol/L) and all class I phosphoinositide 3-kinase (PI3K) isoforms IC(50): PI3Kα = 16 nmol/L; PI3Kβ = 68 nmol/L; PI3Kγ = 25 nmol/L; PI3Kδ = 42 nmol/L, without relevant activity on 400 lipid and protein kinases. VS-5584 shows robust modulation of cellular PI3K/mTOR pathways, inhibiting phosphorylation of substrates downstream of PI3K and mTORC1/2. A large human cancer cell line panel screen (436 lines) revealed broad antiproliferative sensitivity and that cells harboring mutations in PI3KCA are generally more sensitive toward VS-5584 treatment. VS-5584 exhibits favorable pharmacokinetic properties after oral dosing in mice and is well tolerated. VS-5584 induces long-lasting and dose-dependent inhibition of PI3K/mTOR signaling in tumor tissue, leading to tumor growth inhibition in various rapalog-sensitive and -resistant human xenograft models. Furthermore, VS-5584 is synergistic with an EGF receptor inhibitor in a gastric tumor model. The unique selectivity profile and favorable pharmacologic and pharmaceutical properties of VS-5584 and its efficacy in a wide range of human tumor models supports further investigations of VS-5584 in clinical trials.

Both osteopontin-c and osteopontin-b splicing isoforms exert pro-tumorigenic roles in prostate cancer cells

BACKGROUND

Alternative splicing of the osteopontin (opn, spp1) gene generates three protein splicing isoforms (OPN-SI), designated as OPNa, OPNb, and OPNc, which have demonstrated specific roles in different tumor models. This work aims to investigate the roles of each OPN-SI in prostate cancer (PCa) progression by using in vivo and in vitro functional assays.

METHODS

The expression levels of OPN-SI in prostate cell lines were analyzed by qRT-PCR. PC-3 was stably transfected with expression vectors containing OPNa, OPNb, and OPNc, as well as empty vector controls. PC-3 cells overexpressing each construct were analyzed for in vivo tumor growth and in relation to different aspects mimicking tumor progression, such as cell proliferation, migration, invasion, and soft agar colony formation.

RESULTS

OPN-SI are overexpressed in PCa as compared to non-tumoral prostate cell lines. OPNc and OPNb overexpressing cells significantly activated enhanced xenograft tumor growth and PC-3 proliferation, migration, invasion, and soft agar colony formation, as well as the expression of MMP-2, MMP-9, and VEGF. These isoforms also support sustained proliferative survival. We found that both OPNc and OPNb pro-tumorigenic roles are mainly mediated through PI3K signaling. Inhibition of this pathway by using LY294002 specifically inhibited tumor progression features evoked by OPNc and OPNb overexpression.

CONCLUSIONS

Our data provide evidence that both OPNc and OPNb splicing isoforms promote distinct aspects of PCa progression by inducing PI3K signaling. These data give support to strategies aiming to downregulate OPNc and OPNb expression as an approach to inhibit PCa progression.

PIK3CA exon 20 mutations are associated with poor prognosis in breast cancer patients

OBJECTIVES

The phosphatidylinositol 3-kinase/AKT axis is an important cell-signaling pathway that mediates cell proliferation and survival, two biological processes that regulate malignant cell growth. The phosphatidylinositol 3-kinase CA gene encodes the p110α subunit of the phosphatidylinositol 3-kinase protein. There are phosphatidylinositol 3-kinase CA mutations in several types of human tumors, and they are frequently observed in breast cancer. However, these mutations have not been investigated in Brazilian breast cancer patients.

METHODS

PCR-SSCP and direct DNA sequencing were performed to identify phosphatidylinositol 3-kinaseCA exon 9 and exon 20 mutations in 86 patients with sporadic breast cancer. The relationships between PIK3CA mutations and patient clinicopathological characteristics and survival were analyzed. The presence of the TP53 mutation was also examined.

RESULTS

Twenty-three (27%) of the 86 primary breast tumors contained PIK3CA mutations. In exons 9 and 20, we identified the hotspot mutations E542K, E545K, and H1047R, and we identified two new missense mutations (I1022V and L1028S) and one nonsense (R992X) mutation. Phosphatidylinositol 3-kinase CA exon 20 mutations were associated with poor overall survival and TP53 gene mutations.

CONCLUSIONS

Phosphatidylinositol 3-kinase CA mutations are common in tumors in Brazilian breast cancer patients, and phosphatidylinositol 3-kinase CA and TP53 mutations are not mutually exclusive. Phosphatidylinositol 3-kinase CA exon 20 mutations are associated with poor survival, and they may be useful biomarkers for identifying breast cancer patients with aggressive tumors and for predicting the response to treatment with PI3K pathway inhibitors.

Preclinical assessment of the absorption and disposition of the phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor GDC-0980 and prediction of its pharmacokinetics and efficacy in human

(S)-1-{4-[2-(2-Amino-pyrimidin-5-yl)-7-methyl-4-morpholin-4-yl-thieno[3,2-d]pyrimidin-6-ylmethyl]-piperazin-1-yl}-2-hydroxy-propan-1-one (GDC-0980) is a potent and selective inhibitor of phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin, two key components of the PI3K pathway, the deregulation of which is associated with the development of many cancers. The objectives of these studies were to characterize the absorption and disposition of GDC-0980 and assess its efficacy in an MCF7-neo/HER2 human breast cancer xenograft model in immunocompromised mice. Studies in parental Madin-Darby canine kidney cells indicated that GDC-0980 had high permeability (P(app) = 18 × 10⁻⁶ cm/s), suggesting good absorption potential. However, it was found to be a P-glycoprotein and breast cancer resistance protein substrate in transfected cells and in knockout mice studies. Plasma protein binding was low, with the fraction unbound ranging from 29 to 52% across species. GDC-0980 hepatic clearance (CL) was predicted to be low in all of the species tested from hepatocyte incubations. The plasma CL of GDC-0980 was low in mouse (6.30 ml · min⁻¹ · kg⁻¹), rat (15.4 ml · min⁻¹ · kg⁻¹), and dog (6.37 ml · min⁻¹ · kg⁻¹) and moderate in cynomolgus monkey (18.9 ml · min⁻¹ · kg⁻¹). Oral bioavailability ranged from 14.4% in monkey to 125% in dog. Predicted human plasma CL and volume of distribution using allometry were 5.1 ml · min⁻¹ · kg⁻¹ and 1.8 l/kg, respectively. Parameters estimated from the pharmacokinetic/pharmacodynamic modeling of the MCF7-neo/HER2 xenograft data indicated that the GDC-0980 plasma concentration required for tumor stasis was approximately 0.5 μM. These parameters, combined with the predicted human pharmacokinetic profile, suggested that 55 mg once daily may be a clinically efficacious dose. GDC-0980 preclinical characterization and the predictions of its human properties supported its clinical development; it is currently in Phase II clinical trials.

Simultaneous inhibition of pan-phosphatidylinositol-3-kinases and MEK as a potential therapeutic strategy in peripheral T-cell lymphomas

Peripheral T-cell lymphomas are very aggressive hematologic malignancies for which there is no targeted therapy. New, rational approaches are necessary to improve the very poor outcome in these patients. Phosphatidylinositol-3-kinase is one of the most important pathways in cell survival and proliferation. We hypothesized that phosphatidylinositol-3-kinase inhibitors could be rationally selected drugs for treating peripheral T-cell lymphomas. Several phosphatidylinositol-3-kinase isoforms were inhibited genetically (using small interfering RNA) and pharmacologically (with CAL-101 and GDC-0941 compounds) in a panel of six peripheral and cutaneous T-cell lymphoma cell lines. Cell viability was measured by intracellular ATP content; apoptosis and cell cycle changes were checked by flow cytometry. Pharmacodynamic biomarkers were assessed by western blot. The PIK3CD gene, which encodes the δ isoform of phosphatidylinositol-3-kinase, was overexpressed in cell lines and primary samples, and correlated with survival pathways. However, neither genetic nor specific pharmacological inhibition of phosphatidylinositol-3-kinase δ affected cell survival. In contrast, the pan-phosphatidylinositol-3-kinase inhibitor GDC-0941 arrested all T-cell lymphoma cell lines in the G1 phase and induced apoptosis in a subset of them. We identified phospho-GSK3β and phospho-p70S6K as potential biomarkers of phosphatidylinositol-3-kinase inhibitors. Interestingly, an increase in ERK phosphorylation was observed in some GDC -0941-treated T-cell lymphoma cell lines, suggesting the presence of a combination of phosphatidylinositol-3-kinase and MEK inhibitors. A highly synergistic effect was found between the two inhibitors, with the combination enhancing cell cycle arrest at G0/G1 in all T-cell lymphoma cell lines, and reducing cell viability in primary tumor T cells ex vivo. These results suggest that the combined treatment of pan-phosphatidylinositol-3-kinase + MEK inhibitors could be more effective than single phosphatidylinositol-3-kinase inhibitor treatment, and therefore, that this combination could be of therapeutic value for treating peripheral and cutaneous T-cell lymphomas.

Attenuation of TORC1 signaling delays replicative and oncogenic RAS-induced senescence

Numerous stimuli, including oncogenic signaling, DNA damage or eroded telomeres trigger proliferative arrest, termed cellular senescence. Accumulating evidence suggests that cellular senescence is a potent barrier to tumorigenesis in vivo, however oncogene induced senescence can also promote cellular transformation. Several oncogenes, whose overexpression results in cellular senescence, converge on the TOR (target of rapamycin) pathway. We therefore examined whether attenuation of TOR results in delay or reversal of cellular senescence. By using primary human fibroblasts undergoing either replicative or oncogenic RAS-induced senescence, we demonstrated that senescence can be delayed, and some aspects of senescence can be reversed by inhibition of TOR, using either the TOR inhibitor rapamycin or by depletion of TORC1 (TOR Complex 1). Depletion of TORC2 fails to affect the course of replicative or RAS-induced senescence. Overexpression of REDD1 (Regulated in DNA Damage Response and Development), a negative regulator of TORC1, delays the onset of replicative senescence. These results indicate that TORC1 is an integral component of the signaling pathway that mediates cellular senescence.

Butein induces apoptosis and inhibits prostate tumor growth in vitro and in vivo

AIM

Prostate cancer (PCa) is one of the most common cancers in men in the United States with similar trends worldwide. For several reasons, it is an ideal candidate disease for intervention with dietary botanical antioxidants. Indeed, many botanical antioxidants are showing promise for chemoprevention of PCa. Here, we determined the effect of an antioxidant butein (3,4,2',4'-tetrahydroxychalone) on cell growth, apoptosis, and signaling pathways in human PCa cells in-vitro and on tumor growth in athymic nude mice.

RESULTS

Treatment with butein (10-30 μM; 48 h) caused a decrease in viability of PCa cells but had only a minimal effect on normal prostate epithelial cells. In butein-treated cells, there was a marked decrease in the protein expression of cyclins D1, D2, and E and cdks 2, 4, and 6 with concomitant induction of WAF1/p21 and KIP1/p27. Treatment of cells with butein caused inhibition of (i) phosphatidylinositol 3-kinase (p85 and p110), (ii) phosphorylation of Akt at both Ser(473) and Thr(308), (iii) nuclear factor-kappa B (NF-κB) and IκB kinaseα, (iv) degradation and phosphorylation of IκBα, (v) NF-κB DNA-binding activity, (vi) induction of apoptosis, and (vii) Poly (ADP-ribose) polymerase cleavage with activation of caspases-3, -8, and -9. Pretreatment of cells with caspase inhibitor (Z-VAD-FMK) blocked butein-induced activation of caspases. In athymic nude mice implanted with human PCa cells, butein caused a significant inhibition of tumor growth with a decrease in the serum prostate-specific antigen levels.

INNOVATION

For the first time, we have shown that butein caused inhibition of prostate tumor growth in-vivo.

CONCLUSION

We suggest that butein could be developed as an agent against PCa. Antioxid. Redox Signal. 16, 1195-1204.