Phosphatidylinositol 3-kinase (PI3K) inhibitors as cancer therapeutics

Blinatumomab: a bispecific T cell engager (BiTE) antibody against CD19/CD3 for refractory acute lymphoid leukemia

Targeted therapy has been the forefront of cancer treatment. Cancer immunotherapy is the most recent focus. In addition, novel immunotherapeutics targeting B cell receptor signaling (e.g., ibrutinib), T cell receptor ( e.g., CART19), and NK cells (e.g., AFM13) are being developed. This review summarized the new development in blinatumomab (MT103/MEDI-538), a first-in-class bispecific T engager (BiTE) antibody against CD19/CD3 in patients with relapsed/refractory precursor B cell acute lymphoid leukemia.

Palbociclib: a first-in-class CDK4/CDK6 inhibitor for the treatment of hormone-receptor positive advanced breast cancer

Palbociclib was approved by the FDA for use in combination with letrozole for the treatment of postmenopausal women with hormone-receptor-positive, HER2-negative advanced breast cancer as initial endocrine-based therapy. In addition, the combination of palbociclib with fulvestrant resulted in superior outcome than fulvestrant alone in those who had progressed during prior endocrine therapy. This research highlight summarized the current development of CDK4/CDK6 inhibitors and future directions in the treatment of advanced hormone-receptor-positive breast cancer.

GW5074 and PP2 kinase inhibitors implicate nontraditional c-Raf and Lyn function as drivers of retinoic acid-induced maturation

The multivariate nature of cancer necessitates multi-targeted therapy, and kinase inhibitors account for a vast majority of approved cancer therapeutics. While acute promyelocytic leukemia (APL) patients are highly responsive to retinoic acid (RA) therapy, kinase inhibitors have been gaining momentum as co-treatments with RA for non-APL acute myeloid leukemia (AML) differentiation therapies, especially as a means to treat relapsed or refractory AML patients. In this study GW5074 (a c-Raf inhibitor) and PP2 (a Src-family kinase inhibitor) enhanced RA-induced maturation of t(15;17)-negative myeloblastic leukemia cells and rescued response in RA-resistant cells. PD98059 (a MEK inhibitor) and Akti-1/2 (an Akt inhibitor) were less effective, but did tend to promote maturation-uncoupled G1/G0 arrest, while wortmannin (a PI3K inhibitor) did not enhance differentiation surface marker expression or growth arrest. PD98059 and Akti-1/2 did not enhance differentiation markers and have potential, antagonistic off-targets effects on the aryl hydrocarbon receptor (AhR), but neither could the AhR agonist 6-formylindolo(3,2-b)carbazole (FICZ) rescue differentiation events in the RA-resistant cells. GW5074 rescued early CD38 expression in RA-resistant cells exhibiting an early block in differentiation before CD38 expression, while for RA-resistant cells with differentiation blocked later, PP2 rescued the later differentiation marker CD11b; but surprisingly, the combination of the two was not synergistic. Kinases c-Raf, Src-family kinases Lyn and Fgr, and PI3K display highly correlated signaling changes during RA treatment, while activation of traditional downstream targets (Akt, MEK/ERK), and even the surface marker CD38, were poorly correlated with c-Raf or Lyn during differentiation. This suggests that an interrelated kinase module involving c-Raf, PI3K, Lyn and perhaps Fgr functions in a nontraditional way during RA-induced maturation or during rescue of RA induction therapy using inhibitor co-treatment in RA-resistant leukemia cells.

AFM13: a first-in-class tetravalent bispecific anti-CD30/CD16A antibody for NK cell-mediated immunotherapy

Monoclonal antibodies against CD20 molecule have been leading the revolution of lymphoma treatment. In addition to monoclonal antibodies against CD20 and CD30, novel agents of immunotherapeutics in clinical development are being developed and are rapidly migrating to clinical application. One area of active development is NK cell activators, such as AFM13. This review will highlight the latest development of AFM13 as the first-in-class tetravalent bispecific anti-CD30/CD16A antibody for NK cell-mediated immunotherapy.

Genetics and pharmacology of longevity: the road to therapeutics for healthy aging

Aging can be defined as the progressive decline in tissue and organismal function and the ability to respond to stress that occurs in association with homeostatic failure and the accumulation of molecular damage. Aging is the biggest risk factor for human disease and results in a wide range of aging pathologies. Although we do not completely understand the underlying molecular basis that drives the aging process, we have gained exceptional insights into the plasticity of life span and healthspan from the use of model organisms such as the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Single-gene mutations in key cellular pathways that regulate environmental sensing, and the response to stress, have been identified that prolong life span across evolution from yeast to mammals. These genetic manipulations also correlate with a delay in the onset of tissue and organismal dysfunction. While the molecular genetics of aging will remain a prosperous and attractive area of research in biogerontology, we are moving towards an era defined by the search for therapeutic drugs that promote healthy aging. Translational biogerontology will require incorporation of both therapeutic and pharmacological concepts. The use of model organisms will remain central to the quest for drug discovery, but as we uncover molecular processes regulated by repurposed drugs and polypharmacy, studies of pharmacodynamics and pharmacokinetics, drug-drug interactions, drug toxicity, and therapeutic index will slowly become more prevalent in aging research. As we move from genetics to pharmacology and therapeutics, studies will not only require demonstration of life span extension and an underlying molecular mechanism, but also the translational relevance for human health and disease prevention.

Therapeutic potential of new B cell-targeted agents in the treatment of elderly and unfit patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL), the most common adult leukemia in the Western world, is primarily a disease of the elderly, with most patients ≥65 years of age and having at least one major comorbidity. Aggressive chemoimmunotherapy regimens recommended to achieve remission and improve survival in young, fit patients are often poorly tolerated in elderly and/or less physiologically fit (“unfit”) patients, necessitating alternative treatment options. Although patient age, fitness, and comorbidities are key considerations in the selection of a treatment regimen, historically, clinical trials have been limited to young, fit patients by virtue of the ethical concerns associated with potential end organ toxic effects that could worsen comorbidities. However, the availability of new therapies promises a shift to a research paradigm that encompasses the identification of optimal treatments for elderly and unfit patients. Anti-CD20 monoclonal antibody therapy, which overall has improved response rates and survival in patients with CLL, has only recently been evaluated elderly and unfit patients. B cell-targeted agents such as the Bruton’s tyrosine kinase inhibitor ibrutinib and the phosphatidylinositol 3-kinase inhibitor idelalisib are the first of a new generation of oral agents for CLL. Available clinical data suggest that these therapies have the potential to address the unmet need in elderly and unfit patients with CLL and result in clinical remission, and not merely symptom palliation and improved quality of life, which, by themselves, are also a reasonable goal.

GD2 ganglioside specific antibody treatment downregulates PI3K/Akt/mTOR signaling network in human neuroblastoma cell lines

Mechanisms leading to inhibitory effects of an anti-GD2 ganglioside (GD2) 14G2a mouse monoclonal antibody (mAb) and PI3K/Akt/mTOR pathway inhibitors on human neuroblastoma cell survival were studied in vitro. We have recently shown on IMR-32, CHP‑134, and LA-N-1 neuroblastoma cells that targeting GD2 with the mAb decreases cell viability of the cell lines. In this study we used cytotoxicity assays, proteomic arrays and immunoblotting to evaluate the response of the three cell lines to the anti‑GD2 14G2a mAb and specific PI3K/Akt/mTOR pathway inhibitors. We show here that the mAb modulates intracellular signal transduction through changes in several kinases and their substrates phosphorylation. More detailed analysis of the PI3K/Akt/mTOR pathway showed significant decrease in activity of Akt, mTOR, p70 S6 and 4E-BP1 proteins and transient increase in PTEN (a suppressor of the pathway), leading to inhibition of the signaling network responsible for stimulation of translation and proliferation. Additionally, combining the GD2-specific 14G2a mAb with an Akt inhibitor (perifosine), dual mTOR/PI3K inhibitors (BEZ-235 and SAR245409), and a pan-PI3K inhibitor (LY294002) was shown to enhance cytotoxic effects against IMR-32, CHP‑134 and LA-N-1 cells. Our study extends knowledge on mechanisms of action of the 14G2a mAb on the neuroblastoma cells. Also, it stresses the need for further delineation of molecular signal orchestration aimed at more reasonable selection of drugs to target key cellular pathways in quest for better cure for neuroblastoma patients.

Design and Validation of FRESH, a Drug Discovery Paradigm Resting on Robust Chemical Synthesis

A method capable of identifying novel synthetic targets for small molecule lead optimization has been developed. The FRESH (FRagment-based Exploitation of modular Synthesis by vHTS) approach relies on a multistep synthetic route to a target series of compounds devised by a close collaboration between synthetic and computational chemists. It combines compound library generation, quantitative structure-acitvity relationship construction, fragment processing, virtual high throughput screening and display of results within the Pipeline Pilot framework. Outcomes enumerate tailored selection of novel synthetic targets with improved potency and optimized physical properties for an emerging compound series. To validate the application of FRESH, three retrospective case studies have been performed to pinpoint reported potent analogues. One prospective case study was performed to demonstrate that FRESH is able to capture additional potent analogues.

Update on Head and Neck Cancer: Current Knowledge on Epidemiology, Risk Factors, Molecular Features and Novel Therapies

Tobacco use and alcohol consumption are the main risk factors associated with head and neck squamous cell carcinoma (SCC) development due to their cytotoxic and mutagenic effects on the exposed epithelia of the upper aerodigestive tract. Epstein-Barr virus (EBV) and high-risk human papillomaviruses (HPVs), both encoding viral oncoproteins able to interfere with cell cycle control, have been recognized as the etiological agents of nasopharynx carcinoma and a fraction of oropharyngeal carcinoma, respectively. Head and neck SCC is a deadly disease and despite innovative treatments represents a major challenge for patients. Recently, a number of genomic studies have highlighted the molecular heterogeneity of head and neck SCC based on methylation profiles, microRNA expression, mutated genes and new druggable pathways which may represent new targets for cancer-tailored therapies. To date, cetuximab is the only FDA-approved anti-epidermal growth factor receptor therapy for the treatment of head and neck SCC. In addition, a number of monoclonal antibodies targeting AKT, mTOR and PI3K pathways are under evaluation. Several therapeutic vaccines against HPV16 and EBV proteins are also under study. The purpose of this article is to review the epidemiology, pathogenesis and molecular features of head and neck SCC, with an emphasis on new therapies.

Novel approaches in the management of pancreatic ductal adenocarcinoma: potential promises for the future

Despite a few breakthroughs in therapy for advanced disease in the recent years, pancreatic ductal adenocarcinoma continues to remain one of the most challenging human malignancies to treat. The overall prognosis for the majority of patients with pancreatic cancer is rather dismal, and therefore, more effective treatment options are being desperately sought. The practical goals of management are to improve the cure rates for patients with resectable disease, achieve a higher conversion rate of locally advanced tumor into potentially resectable disease, and finally, prolong the overall survival for those who develop metastatic disease. Our understanding of the complex genetic alterations, the implicated molecular pathways, and the role of desmoplastic stroma in pancreatic cancer tumorigenesis has increased several folds in the recent years. This has facilitated the development of novel therapeutic strategies against pancreatic cancer, some of which are currently under evaluation in ongoing preclinical and clinical studies. This review will summarize the existing treatment approaches for this devastating disease and also discuss the promising therapeutic approaches that are currently in different stages of clinical development.

Phosphatidylinositol-3-kinase as a putative target for anticancer action of clotrimazole

Clotrimazole (CTZ) has been proposed as an antitumoral agent because of its properties that inhibit glycolytic enzymes and detach them from the cytoskeleton. However, the broad effects of the drug, e.g., acting on different enzymes and pathways, indicate that CTZ might also affect several signaling pathways. In this study, we show that CTZ interferes with the human breast cancer cell line MCF-7 after a short incubation period (4 h), thereby diminishing cell viability, promoting apoptosis, depolarizing mitochondria, inhibiting key glycolytic regulatory enzymes, decreasing the intracellular ATP content, and permeating plasma membranes. CTZ treatment also interferes with autophagy. Moreover, when the incubation is performed under hypoxic conditions, certain effects of CTZ are enhanced, such as phosphatidylinositol-3-phosphate kinase (PI3K), which is inhibited upon CTZ treatment; this inhibition is potentiated under hypoxia. CTZ-induced PI3K inhibition is not caused by upstream effects of CTZ because the drug does not affect the interaction of the PI3K regulatory subunit and the insulin receptor substrate (IRS)-1. Additionally, CTZ directly inhibits human purified PI3K in a dose-dependent and reversible manner. Pharmacologic and in silico results suggest that CTZ may bind to the PI3K catalytic site. Therefore, we conclude that PI3K is a novel, putative target for the antitumoral effects of CTZ, interfering with autophagy, apoptosis, cell division and viability.

Alpha-enolase promotes cell glycolysis, growth, migration, and invasion in non-small cell lung cancer through FAK-mediated PI3K/AKT pathway

Background

During tumor formation and expansion, increasing glucose metabolism is necessary for unrestricted growth of tumor cells. Expression of key glycolytic enzyme alpha-enolase (ENO1) is controversial and its modulatory mechanisms are still unclear in non-small cell lung cancer (NSCLC).

Methods

The expression of ENO1 was examined in NSCLC and non-cancerous lung tissues, NSCLC cell lines, and immortalized human bronchial epithelial cell (HBE) by quantitative real-time reverse transcription PCR (qRT-PCR), immunohistochemistry, and Western blot, respectively. The effects and modulatory mechanisms of ENO1 on cell glycolysis, growth, migration, invasion, and in vivo tumorigenesis and metastasis in nude mice were also analyzed.

Results

ENO1 expression was increased in NSCLC tissues in comparison to non-cancerous lung tissues. Similarly, NSCLC cell lines A549 and SPCA-1 also express higher ENO1 than HBE cell line in both mRNA and protein levels. Overexpressed ENO1 significantly elevated NSCLC cell glycolysis, proliferation, clone formation, migration, and invasion in vitro, as well as tumorigenesis and metastasis in vivo by regulating the expression of glycolysis, cell cycle, and epithelial-mesenchymal transition (EMT)-associated genes. Conversely, ENO1 knockdown reversed these effects. More importantly, our further study revealed that stably upregulated ENO1 activated FAK/PI3K/AKT and its downstream signals to regulate the glycolysis, cell cycle, and EMT-associated genes.

Conclusion

This study showed that ENO1 is responsible for NSCLC proliferation and metastasis; thus, ENO1 might serve as a potential molecular therapeutic target for NSCLC treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0117-5) contains supplementary material, which is available to authorized users.

p85α is a microRNA target and affects chemosensitivity in pancreatic cancer

BACKGROUND

We previously identified a correlation between increased expression of the phosphoinositide 3-kinase (PI3K) regulatory subunit p85α and improved survival in human pancreatic ductal adenocarcinoma (PDAC). The purpose of this study was to investigate the impact of changes in p85α expression on response to chemotherapy and the regulation of p85α by microRNA-21 (miR-21).

MATERIALS AND METHODS

PDAC tumor cells overexpressing p85α were generated by viral transduction, and the effect of p85α overexpression on sensitivity to gemcitabine was tested by MTT assay. Primary human PDAC tumors were stained for p85α and miR-21 via immunohistochemistry and in situ hybridization, respectively. Additionally, PDAC cells were treated with miR-21 mimic, and changes in p85α and phospho-AKT were assessed by Western blot. Finally, a luciferase reporter assay system was used to test direct regulation of p85α by miR-21.

RESULTS

Higher p85α expression resulted in increased sensitivity to gemcitabine (P < 0.01), which correlated with decreased PI3K-AKT activation. Human tumors demonstrated an inverse correlation between miR-21 and p85α expression levels (r = -0.353, P < 0.001). In vitro, overexpression of miR-21 resulted in decreased levels of p85α and increased phosphorylation of AKT. Luciferase reporter assays confirmed the direct regulation of p85α by miR-21 (P < 0.01).

CONCLUSIONS

Our results demonstrate that p85α expression is a determinant of chemosensitivity in PDAC. Additionally, we provide novel evidence that miR-21 can influence PI3K-AKT signaling via its direct regulation of p85α. These data provide insight into potential mechanisms for the known relationship between increased p85α expression and improved survival in PDAC.

Novel ALK inhibitors in clinical use and development

Anaplastic lymphoma kinase 1 (ALK-1) is a member of the insulin receptor tyrosine kinase family. ALK-1 was initially found in anaplastic large cell lymphoma (ALCL). ALK mutations have also been implicated in the pathogenesis of non-small cell lung cancer (NSCLC) and other solid tumors. Multiple small molecule inhibitors with activity against ALK and related oncoproteins are under clinical development. Two of them, crizotinib and ceritinib, have been approved by FDA for treatment of locally advanced and metastatic NSCLC. More agents (alectinib, ASP3026, X396) with improved safety, selectivity, and potency are in the pipeline. Dual inhibitors targeting ALK and EGFRm (AP26113), TRK (TSR011), FAK (CEP-37440), or ROS1 (RXDX-101, PF-06463922) are under active clinical development.

Idelalisib- a PI3Kδ targeting agent for B-cell malignancies

Idelalisib, the first in-class phosphotidlyinositol 3-kinase delta (PI3Kδ) inhibitor, was approved by the US Food and Drug Administration in July 2014. It simultaneously received breakthrough therapy designation in combination with rituximab for the treatment of relapsed chronic lymphocytic leukemia (CLL) as well as accelerated approval as monotherapy for the treatment of relapsed follicular lymphoma and relapsed small lymphocytic lymphoma. In a pivotal phase III study of 220 patients with relapsed CLL, the overall response rate of patients who received rituximab plus idelalisib was 81%. The median progression-free survival (PFS) was 5 months with rituximab plus placebo group, but was not reached in the idelalisib arm. At 24 weeks, the PFS in patients receiving idelalisib was 93%. In a phase II trial of 125 patients with relapsed or refractory indolent non-Hodgkin lymphoma who received idelalisib 150 mg twice daily, the response rate was 57%. Complete response was seen in 6% of patients. The median duration of response was 12.5 months, and median PFS was 11 months. Idelalisib is a promising new therapy for relapsed indolent B-cell malignancies.

Novel agents and associated toxicities of inhibitors of the pi3k/Akt/mtor pathway for the treatment of breast cancer

The pi3k/Akt/mtor (phosphatidylinositol 3 kinase/ Akt/mammalian target of rapamycin) signalling pathway is an established driver of oncogenic activity in human malignancies. Therapeutic targeting of this pathway holds significant promise as a treatment strategy. Everolimus, an mtor inhibitor, is the first of this class of agents approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer. Everolimus has been associated with significant improvements in progression-free survival; however, it is also associated with increased toxicity related to its specific mechanism of action.

METHODS

A comprehensive review of the literature conducted using a focused medline search was combined with a search of current trials at http://ClinicalTrials.gov/. Summary tables of the toxicities of the various classes of pi3k/Akt/mtor inhibitors were created. A broad group of Canadian health care professionals was assembled to review the data and to produce expert opinion and summary recommendations for possible best practices in managing the adverse events associated with these pathway inhibitors.

RESULTS

Differing toxicities are associated with the various classes of pi3k/Akt/mtor pathway inhibitors. The most common unique adverse events observed in everolimus clinical trials in breast cancer include stomatitis (all grades: approximately 60%), noninfectious pneumonitis (15%), rash (40%), hyperglycemia (15%), and immunosuppression (40%). To minimize grades 3 and 4 toxicities and to attempt to attain optimal outcomes, effective management of those adverse events is critical. Management should be interdisciplinary and should use approaches that include education, early recognition, active intervention, and potentially prophylactic strategies.

DISCUSSION

Everolimus likely represents the first of many complex oral targeted therapies for the treatment of breast cancer. Using this agent as a template, it is essential to establish best practices involving and integrating multiple disciplines for the management of future pi3k/Akt/mtor signalling pathway inhibitors.

The oncofetal protein IMP3: a novel grading tool and predictor of poor clinical outcome in human gliomas

Morphologic criteria illustrated in WHO guidelines are the most significant prognostic factor in human gliomas, but novel biomarkers are needed to identify patients with a poorer outcome. The present study examined the expression of the oncofetal protein IMP3 in a series of 135 patients affected by high-grade (grade III and IV) gliomas, correlating the results with proliferative activity, molecular parameters, and clinical and follow-up data. Overall, IMP3 expression was higher in glioblastomas (68%) than in grade III tumors (20%, P < 0.0001), and IMP3-positive high-grade gliomas showed a shorter overall and disease-free survival than negative ones (P = 0.0002 and P = 0.006, resp.). IMP3 expression was significantly associated with the absence of mutations of IDH1 gene (P = 0.0001) and with the unmethylated phenotype of MGMT in high-grade gliomas (P = 0.004). High Ki67 levels were correlated with better prognosis in glioblastomas but IMP3 expression was not correlated with the proliferation index. These findings confirm the role of IMP3 as a marker of poor outcome, also in consideration of its association with IDH1 wild-type phenotype and MGMT unmethylated status. The data suggest that IMP3 staining could identify a subgroup of patients with poor prognosis and at risk of recurrence in high-grade gliomas.

Biochemical, biological and structural properties of romidepsin (FK228) and its analogs as novel HDAC/PI3K dual inhibitors

Romidepsin (FK228, depsipeptide) is a potent histone deacetylase (HDAC) inhibitor that has FDA approval for the treatment of cutaneous and peripheral T-cell lymphomas. We have previously reported that FK228 and its analogs have an additional activity as phosphatidylinositol 3-kinase (PI3K) inhibitors, and are defined as HDAC/PI3K dual inhibitors. Because a combination of an HDAC inhibitor and a PI3K inhibitor induces apoptosis in human cancer cells in a synergistic manner, development of an HDAC/PI3K dual inhibitor will provide an attractive novel drug for cancer therapy. Using structure-based optimization of the analogs, FK-A11 was identified as the most potent analog. FK-A11 inhibited phosphorylation of AKT and accelerated histone acetylation at lower concentrations, resulting in stronger cytotoxic effects than FK228 and the other analogs in human cancer cells. In this study, we have characterized the biochemical, biological and structural properties of FK228 analogs as PI3K inhibitors. First, FK-A11 is an ATP competitive PI3K inhibitor. Second, FK-A11 is a pan-p110 isoform inhibitor. Third, FK-A11 selectively inhibits PI3K among 22 common cellular kinases. Fourth, conformational changes of FK228 analogs by reduction of an internal disulfide bond have no effect on PI3K inhibitory activity, unlike HDAC inhibitory activity. Finally, molecular modeling of PI3K-FK228 analogs and analyses of the binding affinities identified the structure that defines potency for PI3K inhibitory activity. These results prove our concept that a series of FK228 analogs are HDAC/PI3K dual inhibitors. These findings should help in the development of FK228 analogs as novel HDAC/PI3K dual inhibitors.

Differential regulatory functions of three classes of phosphatidylinositol and phosphoinositide 3-kinases in autophagy

Autophagy is an evolutionarily conserved and exquisitely regulated self-eating cellular process with important biological functions. Phosphatidylinositol 3-kinases (PtdIns3Ks) and phosphoinositide 3-kinases (PI3Ks) are involved in the autophagic process. Here we aim to recapitulate how 3 classes of these lipid kinases differentially regulate autophagy. Generally, activation of the class I PI3K suppresses autophagy, via the well-established PI3K-AKT-MTOR (mechanistic target of rapamycin) complex 1 (MTORC1) pathway. In contrast, the class III PtdIns3K catalytic subunit PIK3C3/Vps34 forms a protein complex with BECN1 and PIK3R4 and produces phosphatidylinositol 3-phosphate (PtdIns3P), which is required for the initiation and progression of autophagy. The class II enzyme emerged only recently as an alternative source of PtdIns3P and autophagic initiator. However, the orthodox paradigm is challenged by findings that the PIK3CB catalytic subunit of class I PI3K acts as a positive regulator of autophagy, and PIK3C3 was thought to be an amino acid sensor for MTOR, which curbs autophagy. At present, a number of PtdIns3K and PI3K inhibitors, including specific PIK3C3 inhibitors, have been developed for suppression of autophagy and for clinical applications in autophagy-related human diseases.

Anti-angiogenic activity of macrolactin A and its succinyl derivative is mediated through inhibition of class I PI3K activity and its signaling

In the current study, macrolactin compounds, macrolactin A (MA) and 7-O-succinyl macrolactin A (SMA), were investigated for their anti-angiogenic activities and action mechanism. MA and SMA inhibited in vitro and in vivo angiogenesis induced by three different classes of pro-angiogenic factors, VEGF, IL-8, and TNF-α. SMA exhibited stronger anti-angiogenic activity than MA, and such anti-angiogenic activity of SMA was consistently observed in MDA-MB-231 human breast cancer cell-inoculated CAM assay showing dose-dependent suppression of tumor growth and tumor-induced angiogenesis. In an in vitro PI3K competitive activity assay, SMA induced concentration-dependent inhibition of class I PI3K isoforms, p110α, p110β, p110δ, and p110γ. In addition, non-receptor tyrosine kinase c-Src, which is involved in the activation of PI3K heterodimer, was suppressed by MA and SMA. Correspondingly, MA and SMA significantly inhibited the stimulus-induced phosphorylation of Akt, mTOR, p70S6K, and ribosomal S6 in human umbilical vein endothelial cells (HUVECs). At the same time, the stimulus-induced production of reactive oxygen species (ROS) and activation of NF-κB were significantly suppressed by MA and SMA. Moreover, the macrolactins suppressed NF-κB-regulated HSP90 protein expression, which stabilizes phosphorylated Akt and NADPH oxidase. Suppression of NF-κB in macrolactin-treated HUVECs with concurrent inhibition of rS6 indicates that MAs effectively block angiogenesis through down-regulation of genes related to angiogenesis at both transcriptional and translational levels. Taken together, the results demonstrate that anti-angiogenic effect of MA and SMA is mediated through inhibition of PI3K/Akt and NADPH oxidase-derived ROS/NF-κB signaling pathways. These results further indicate that MA and SMA may be applicable for treatment of various diseases associated with angiogenesis.

Subversion of cellular stress responses by poxviruses

Cellular stress responses are powerful mechanisms that prevent and cope with the accumulation of macromolecular damage in the cells and also boost host defenses against pathogens. Cells can initiate either protective or destructive stress responses depending, to a large extent, on the nature and duration of the stressing stimulus as well as the cell type. The productive replication of a virus within a given cell places inordinate stress on the metabolism machinery of the host and, to assure the continuity of its replication, many viruses have developed ways to modulate the cell stress responses. Poxviruses are among the viruses that have evolved a large number of strategies to manipulate host stress responses in order to control cell fate and enhance their replicative success. Remarkably, nearly every step of the stress responses that is mounted during infection can be targeted by virally encoded functions. The fine-tuned interactions between poxviruses and the host stress responses has aided virologists to understand specific aspects of viral replication; has helped cell biologists to evaluate the role of stress signaling in the uninfected cell; and has tipped immunologists on how these signals contribute to alert the cells against pathogen invasion and boost subsequent immune responses. This review discusses the diverse strategies that poxviruses use to subvert host cell stress responses.

A critical evaluation of PI3K inhibition in Glioblastoma and Neuroblastoma therapy

Members of the PI3K/Akt/mTor signaling cascade are among the most frequently altered proteins in cancer, yet the therapeutic application of pharmacological inhibitors of this signaling network, either as monotherapy or in combination therapy (CT) has so far not been particularly successful. In this review we will focus on the role of PI3K/Akt/mTOR in two distinct tumors, Glioblastoma multiforme (GBM), an adult brain tumor which frequently exhibits PTEN inactivation, and Neuroblastoma (NB), a childhood malignancy that affects the central nervous system and does not harbor any classic alterations in PI3K/Akt signaling. We will argue that inhibitors of PI3K/Akt signaling can be components for potentially promising new CTs in both tumor entities, but further understanding of the signal cascade's complexity is essential for successful implementation of these CTs. Importantly, failure to do this might lead to severe adverse effects, such as treatment failure and enhanced therapy resistance.

A critical evaluation of PI3K inhibition in Glioblastoma and Neuroblastoma therapy

Members of the PI3K/Akt/mTor signaling cascade are among the most frequently altered proteins in cancer, yet the therapeutic application of pharmacological inhibitors of this signaling network, either as monotherapy or in combination therapy (CT) has so far not been particularly successful. In this review we will focus on the role of PI3K/Akt/mTOR in two distinct tumors, Glioblastoma multiforme (GBM), an adult brain tumor which frequently exhibits PTEN inactivation, and Neuroblastoma (NB), a childhood malignancy that affects the central nervous system and does not harbor any classic alterations in PI3K/Akt signaling. We will argue that inhibitors of PI3K/Akt signaling can be components for potentially promising new CTs in both tumor entities, but further understanding of the signal cascade's complexity is essential for successful implementation of these CTs. Importantly, failure to do this might lead to severe adverse effects, such as treatment failure and enhanced therapy resistance.

A framework for genomic biomarker actionability and its use in clinical decision making

The increasing scope and availability of genetic testing options for patients suffering from cancer has raised questions about how to use results of molecular diagnostics to inform patient care. For some biomarkers (e.g. BRAF mutations in melanoma), standards exist that outline treatments for individuals harboring aberrations in the biomarker; however for the vast majority of genomic abnormalities, few guidelines exist. Clinical decision making and the therapeutic approach for a patient with a given cancer characterized by aberrations in different genes may be aided by the use of a biomarker actionability framework that provides levels of evidence regarding whether and how a molecular abnormality can be considered a therapeutically relevant biomarker. A gene may be considered theoretically actionable if it has a basis of actionability, such that clinically available drugs can target a gene product that drives the cancer or is differentially expressed in tumor versus normal elements. Herein, we discuss a possible framework for developing guidelines for actionability, as they relate to genomically-based cancer therapeutics.

Selective inhibitors of nuclear export (SINE)--a novel class of anti-cancer agents

Dysregulation of the nucleo-cytoplasmic transport of proteins plays an important role in carcinogenesis. The nuclear export of proteins depends on the activity of transport proteins, exportins. Exportins belong to the karyopherin β superfamily. Exportin-1 (XPO1), also known as chromosomal region maintenance 1 (CRM1), mediates transport of around 220 proteins. In this review, we summarized the development of a new class of antitumor drugs, collectively known as selective inhibitors of nuclear export (SINE). KPT-330 (selinexor) as an oral agent is showing activities in early clinical trials in both solid tumors and hematological malignancies.

A chemical biology approach identified PI3K as a potential therapeutic target for neurofibromatosis type 2

Mutations in the merlin tumor suppressor gene cause Neurofibromatosis type 2 (NF2), which is a disease characterized by development of multiple benign tumors in the nervous system. The current standard of care for NF2 calls for surgical resection of the characteristic tumors, often with devastating neurological consequences. There are currently no approved non-surgical therapies for NF2. In an attempt to identify much needed targets and therapeutically active compounds for NF2 treatment, we employed a chemical biology approach using ultra-high-throughput screening. To support this goal, we created a merlin-null mouse Schwann cell (MSC) line to screen for compounds that selectively decrease their viability and proliferation. We optimized conditions for 384-well plate assays and executed a proof-of-concept screen of the Library of Pharmacologically Active Compounds. Further confirmatory and selectivity assays identified phosphatidylinositol 3-kinase (PI3K) as a potential NF2 drug target. Notably, loss of merlin function is associated with activation of the PI3K/Akt pathway in human schwannomas. We report that AS605240, a PI3K inhibitor, decreased merlin-null MSC viability in a dose-dependent manner without significantly decreasing viability of control Schwann cells. AS605240 exerted its action on merlin-null MSCs by promoting caspase-dependent apoptosis and inducing autophagy. Additional PI3K inhibitors tested also decreased viability of merlin-null MSCs in a dose-dependent manner. In summary, our chemical genomic screen and subsequent hit validation studies have identified PI3K as potential target for NF2 therapy.

Inhibition of the PI3K/Akt/mTOR signaling pathway in diffuse large B-cell lymphoma: current knowledge and clinical significance

Diffuse large B-cell lymphoma (DLBCL) is one of the most common non-Hodgkin lymphomas in adults. The disease is very heterogeneous in its presentation, that is DLBCL patients may differ from each other not only in regard to histology of tissue infiltration, clinical course or response to treatment, but also in respect to diversity in gene expression profiling. A growing body of knowledge on the biology of DLBCL, including abnormalities in intracellular signaling, has allowed the development of new treatment strategies, specifically directed against lymphoma cells. The phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway plays an important role in controlling proliferation and survival of tumor cells in various types of malignancies, including DLBCL, and therefore it may be a promising target for therapeutic intervention. Currently, novel anticancer drugs are undergoing assessment in different phases of clinical trials in aggressive lymphomas, with promising outcomes. In this review we present a state of art review on various classes of small molecule inhibitors selectively involving PI3K/Akt/mTOR pathway and their clinical potential in this disease.

Probing SH2-domains using Inhibitor Affinity Purification (IAP)

BACKGROUND

Many human diseases are correlated with the dysregulation of signal transduction processes. One of the most important protein interaction domains in the context of signal transduction is the Src homology 2 (SH2) domain that binds phosphotyrosine residues. Hence, appropriate methods for the investigation of SH2 proteins are indispensable in diagnostics and medicinal chemistry. Therefore, an affinity resin for the enrichment of all SH2 proteins in one experiment would be desirable. However, current methods are unable to address all SH2 proteins simultaneously with a single compound or a small array of compounds.

RESULTS

In order to overcome these limitations for the investigation of this particular protein family in future experiments, a dipeptide-derived probe has been designed, synthesized and evaluated. This probe successfully enriched 22 SH2 proteins from mixed cell lysates which contained 50 SH2 proteins. Further characterization of the SH2 binding properties of the probe using depletion and competition experiments indicated its ability to enrich complexes consisting of SH2 domain bearing regulatory PI3K subunits and catalytic phosphoinositide 3-kinase (PI3K) subunits that have no SH2 domain.

CONCLUSION

The results make this probe a promising starting point for the development of a mixed affinity resin with complete SH2 protein coverage. Moreover, the additional findings render it a valuable tool for the evaluation of PI3K complex interrupting inhibitors.

Anticancer activity of HS-527, a novel inhibitor targeting PI3-kinase in human pancreatic cancer cells

Pancreatic cancer is known to have low 5-year survival rate and poor response to treatment. In this study, we synthesized HS-527, a new PI3-kinase inhibitor, and investigated not only its anticancer activity, but also its mechanism of action in pancreatic cancer cells. HS-527 had higher specificity for PI3K than other kinases and inhibited PI3K/Akt signaling pathway by down-regulating Akt and P70S6K. And HS-527 inhibited the cell growth and proliferation of the pancreatic cancer in a time- and dose-dependent manner, with greater activity than gemcitabine. Even HS-527 showed lower cytotoxicity than gemcitabine in normal cells. When treated with HS-527, the cancer cells appeared apoptotic, increasing the expression of cleaved PARP, cleaved caspase-3, and Bax. Furthermore, HS-527 showed an anti-angiogenic activity by decreasing the expression of HIF-1α and VEGF, and inhibited the migration of endothelial cells, and the formation of new blood vessel in mouse Matrigel plug assay. In this study, we found that HS-527 showed anti-cancer activity through an inhibition of the PI3K/Akt pathway in pancreatic cancer cells, suggesting that HS-527 could be used as a promising therapeutic agent for pancreatic cancer.

CEPP regimen (cyclophosphamide, etoposide, procarbazine and prednisone) as initial treatment for Hodgkin lymphoma patients presenting with severe abnormal liver function

ABVD regimen (doxorubicin, bleomycin, vinblastine and dacarbazine) remains the most commonly used front-line therapy for Hodgkin lymphoma. However, atypical and extranodal presentations present challenges to initial therapy, especially in the presence of renal and liver failure. We hereby present two cases of young male patients with atypical presentation of Hodgkin lymphoma with severe abnormal liver function. Patients showed excellent response to cyclophosphamide, etoposide, procarbazine and prednisone (CEPP regimen).

Different sensitivity of germinal center B cell-like diffuse large B cell lymphoma cells towards ibrutinib treatment

Background

Although rituximab in the combination of CHOP chemotherapy has been widely used as the standard treatment for several kinds of B-cell non-Hodgkin lymphoma (B-NHL), a great number of B-NHL patients treated with this immunotherapy still develop primary and secondary resistance. Recently Bruton’s tyrosine kinase (Btk) inhibitor ibrutinib showed promising therapeutic effect in relapsed/refractory CLL and B-cell NHL, which provided essential alternatives for these patients.

Methods

The proliferation and apoptosis induction of tumor cells were measured by cell viability assay and Annexin-V staining. Western Blotting analysis and real-time PCR were used to detect the expression level of target proteins and chemokines production.

Results

We demonstrated that ibrutinib inhibited the proliferation and induced apoptosis of GCB-DLBCL cell lines through suppression of BCR signaling pathway and activation of caspase-3. Furthermore, the chemokines CCL3 and CCL4 production from tumor cells were also found to be attenuated by ibrutinib treatment. But different cell lines exhibited distinct sensitivity after ibrutinib treatment. Interestingly, the decreasing level of p-ERK after ibrutinib treatment, but not the basal expression level of Btk, correlated with different drug sensitivity.

Conclusions

Ibrutinib could be a potentially useful therapy for GCB-DLBCL and the decreasing level of p-ERK could become a useful biomarker to predict related therapeutic response.

Neuron-specific regulation of class I PI3K catalytic subunits and their dysfunction in brain disorders

The phosphoinositide 3-kinase (PI3K) complex plays important roles in virtually all cells of the body. The enzymatic activity of PI3K to phosphorylate phosphoinositides in the membrane is mediated by a group of catalytic and regulatory subunits. Among those, the class I catalytic subunits, p110α, p110β, p110γ, and p110δ, have recently drawn attention in the neuroscience field due to their specific dysregulation in diverse brain disorders. While in non-neuronal cells these catalytic subunits may have partially redundant functions, there is increasing evidence that in neurons their roles are more specialized, and confined to distinct receptor-dependent pathways. This review will summarize the emerging role of class I PI3K catalytic subunits in neurotransmitter-regulated neuronal signaling, and their dysfunction in a variety of neurological diseases, including fragile X syndrome, schizophrenia, and epilepsy. We will discuss recent literature describing the use of PI3K subunit-selective inhibitors to rescue brain disease-associated phenotypes in in vitro and animal models. These studies give rise to the exciting prospect that these drugs, originally designed for cancer treatment, may be repurposed as therapeutic drugs for brain disorders in the future.

Ibrutinib for B cell malignancies

Research over the role of Bruton’s agammaglobulinemia tyrosine kinase (BTK) in B-lymphocyte development, differentiation, signaling and survival has led to better understanding of the pathogenesis of B-cell malignancies. Down-regulation of BTK activity is an attractive novel strategy for treating patients with B-cell malignancies. Ibrutinib (PCI-32765), a potent inhibitor of BTK induces impressive responses in B-cell malignancies through irreversible bond with cysteine-481 in the active site of BTK (TH/SH1 domain) and inhibits BTK phosphorylation on Tyr²²³. This review discussed in details the role of BTK in B-cell signaling, molecular interactions between B cell lymphoma/leukemia cells and their microenvironment. Clinical trials of the novel BTK inhibitor, ibrutinib (PCI-32765), in B cell malignancies were summarized.

Identification of a promising PI3K inhibitor for the treatment of multiple myeloma through the structural optimization

BACKGROUND

We previously reported a PI3K inhibitor S14161 which displays a promising preclinical activity against multiple myeloma (MM) and leukemia, but the chiral structure and poor solubility prevent its further application.

METHODS

Six S14161 analogs were designed based on the structure-activity relationship; activity of the compounds in terms of cell death and inhibition of PI3K were analyzed by flow cytometry and Western blotting, respectively; anti-myeloma activity in vivo was performed on two independent xenograft models.

RESULTS

Among the six analogs, BENC-511 was one of the most potent compounds which significantly inhibited PI3K activity and induced MM cell apoptosis. BENC-511 was able to inactivate PI3K and its downstream signals AKT, mTOR, p70S6K, and 4E-BP1 at 1 μM but had no effects on their total protein expression. Consistent with its effects on PI3K activity, BENC-511 induced MM cell apoptosis which was evidenced by the cleavage of Caspase-3 and PARP. Notably, addition of insulin-like growth factor 1 and interleukin-6, two important triggers for PI3K activation in MM cells, partly blocked BENC-511-induced MM cell death, which further demonstrated that PI3K signaling pathway was critical for the anti-myeloma activity of BENC-511. Moreover, BENC-511 also showed potent oral activity against myeloma in vivo. Oral administration of BENC-511 decreased tumor growth up to 80% within 3 weeks in two independent MM xenograft models at a dose of 50 mg/kg body weight, but presented minimal toxicity. Suppression of BENC-511 on MM tumor growth was associated with decreased PI3K/AKT activity and increased cell apoptosis.

CONCLUSIONS

Because of its potent anti-MM activity, low toxicity (LD50 oral >1.5 g/kg), and easy synthesis, BENC-511 could be developed as a promising agent for the treatment of MM via suppressing the PI3K/AKT signaling pathway.