Targeting Akt in cancer therapy

Review the progression of ovarian clear cell carcinoma from the perspective of genomics and epigenomics

Ovarian clear cell carcinoma (OCCC) is a rare subtype of epithelial ovarian cancer with unique molecular characteristics, specific biological and clinical behavior, poor prognosis and high resistance to chemotherapy. Pushed by the development of genome-wide technologies, our knowledge about the molecular features of OCCC has been considerably advanced. Numerous studies are emerging as groundbreaking, and many of them are promising treatment strategies. In this article, we reviewed studies about the genomics and epigenetics of OCCC, including gene mutation, copy number variations, DNA methylation and histone modifications.

Paradoxical Behavior of Oncogenes Undermines the Somatic Mutation Theory

The currently accepted theory on the influence of DNA mutations on carcinogenesis (the Somatic Mutation Theory, SMT) is facing an increasing number of controversial results that undermine the explanatory power of mutated genes considered as "causative" factors. Intriguing results have demonstrated that several critical genes may act differently, as oncogenes or tumor suppressors, while phenotypic reversion of cancerous cells/tissues can be achieved by modifying the microenvironment, the mutations they are carrying notwithstanding. Furthermore, a high burden of mutations has been identified in many non-cancerous tissues without any apparent pathological consequence. All things considered, a relevant body of unexplained inconsistencies calls for an in depth rewiring of our theoretical models. Ignoring these paradoxes is no longer sustainable. By avoiding these conundrums, the scientific community will deprive itself of the opportunity to achieve real progress in this important biomedical field. To remedy this situation, we need to embrace new theoretical perspectives, taking the cell-microenvironment interplay as the privileged pathogenetic level of observation, and by assuming new explanatory models based on truly different premises. New theoretical frameworks dawned in the last two decades principally focus on the complex interaction between cells and their microenvironment, which is thought to be the critical level from which carcinogenesis arises. Indeed, both molecular and biophysical components of the stroma can dramatically drive cell fate commitment and cell outcome in opposite directions, even in the presence of the same stimulus. Therefore, such a novel approach can help in solving apparently inextricable paradoxes that are increasingly observed in cancer biology.

Cancer Therapy Challenge: It Is Time to Look in the "St. Patrick's Well" of the Nature

Cancer still remains a leading cause of death despite improvements in diagnosis, drug discovery and therapy approach. Therefore, there is a strong need to improve methodologies as well as to increase the number of approaches available. Natural compounds of different origins (i.e., from fungi, plants, microbes, etc.) represent an interesting approach for fighting cancer. In particular, synergistic strategies may represent an intriguing approach, combining natural compounds with classic chemotherapeutic drugs to increase therapeutic efficacy and lower the required drug concentrations. In this review, we focus primarily on those natural compounds utilized in synergistic approached to treating cancer, with particular attention to those compounds that have gained the most research interest.

Oncogene-independent resistance in Philadelphia chromosome - positive (Ph+) acute lymphoblastic leukemia (ALL) is mediated by activation of AKT/mTOR pathway

Tyrosine kinase inhibitors (TKIs) such as imatinib, nilotinib, dasatinib, and ponatinib have significantly improved the life expectancy of Philadelphia chromosome-positive (Ph⁺) acute lymphocytic leukemia (ALL) patients; however, resistance to TKIs remains a major clinical challenge. Point mutations in the tyrosine kinase domain (TKD) of BCR-ABL1 have emerged as the predominant cause of acquired resistance. In approximately 30% of patients, the mechanism of resistance to TKIs remains elusive. This study aimed to investigate mechanisms of nonmutational resistance in Ph⁺ ALL. Here we report the development of a nonmutational resistance cell line SupB15-RT; conferring resistance to approved ABL kinase inhibitors (AKIs) and allosteric inhibitors GNF-2, ABL001, and crizotinib, except for dasatinib (IC90 50nM), a multitarget kinase inhibitor. We found that the AKT/mTOR pathway is activated in these cells and their proliferation inhibited by Torin-1 with an IC50 of 24.7 nM. These observations were confirmed using 3 different ALL patient-derived long term cultures (PDLTCs): (1) HP (BCR-ABL1 negative), (2) PH (BCR-ABL1 positive and responsive to TKIs) and (3) BV (BCR-ABL1 positive and nonmutational resistant to TKIs). Furthermore, Torin-1 and NVP-BEZ235 induced apoptosis in PH and BV cells but not in HP cells.

Our experiments provide evidence of the involvement of AKT/mTOR pathway in the evolution of nonmutational resistance in Ph⁺ ALL which will assist in developing novel targeted therapy for Ph⁺ ALL patients with BCR-ABL1 independent nonmutational resistance.

Identification and Validation of SNP-Containing Genes With Prognostic Value in Gastric Cancer via Integrated Bioinformatics Analysis

Background

Gastric cancer is one of the most common malignancies worldwide. Although the diagnosis and treatment of this disease have substantially improved in recent years, the five-year survival rate of gastric cancer is still low due to local recurrence and distant metastasis. An in-depth study of the molecular pathogenesis of gastric cancer and related prognostic markers will help improve the quality of life and prognosis of patients with this disease. The purpose of this study was to identify and verify key SNPs in genes with prognostic value for gastric cancer.

Methods

SNP-related data from gastric cancer patients were obtained from The Cancer Genome Atlas (TCGA) database, and the functions and pathways of the mutated genes were analyzed using DAVID software. A protein-protein interaction (PPI) network was constructed using the STRING database and visualized by Cytoscape software, and molecular complex detection (MCODE) was used to screen the PPI network to extract important mutated genes. Ten hub genes were identified using cytoHubba, and the expression levels and the prognostic value of the central genes were determined by UALCAN and Kaplan-Meier Plotter. Finally, quantitative PCR and Western blotting were used to verify the expression of the hub genes in gastric cancer cells.

Results

From the database, 945 genes with mutations in more than 25 samples were identified. The PPI network had 360 nodes and 1616 edges. Finally, cytoHubba identified six key genes (TP53, HRAS, BRCA1, PIK3CA, AKT1, and SMARCA4), and their expression levels were closely related to the survival rate of gastric cancer patients.

Conclusion

Our results indicate that TP53, HRAS, BRCA1, PIK3CA, AKT1, and SMARCA4 may be key genes for the development and prognosis of gastric cancer. Our research provides an important bioinformatics foundation and related theoretical foundation for further exploring the molecular pathogenesis of gastric cancer and evaluating the prognosis of patients.

Malignant Pleural Mesothelioma Interactome with 364 Novel Protein-Protein Interactions

Malignant pleural mesothelioma (MPM) is an aggressive cancer affecting the outer lining of the lung, with a median survival of less than one year. We constructed an 'MPM interactome' with over 300 computationally predicted protein-protein interactions (PPIs) and over 2400 known PPIs of 62 literature-curated genes whose activity affects MPM. Known PPIs of the 62 MPM associated genes were derived from Biological General Repository for Interaction Datasets (BioGRID) and Human Protein Reference Database (HPRD). Novel PPIs were predicted by applying the HiPPIP algorithm, which computes features of protein pairs such as cellular localization, molecular function, biological process membership, genomic location of the gene, and gene expression in microarray experiments, and classifies the pairwise features as interacting or non-interacting based on a random forest model. We validated five novel predicted PPIs experimentally. The interactome is significantly enriched with genes differentially ex-pressed in MPM tumors compared with normal pleura and with other thoracic tumors, genes whose high expression has been correlated with unfavorable prognosis in lung cancer, genes differentially expressed on crocidolite exposure, and exosome-derived proteins identified from malignant mesothelioma cell lines. 28 of the interactors of MPM proteins are targets of 147 U.S. Food and Drug Administration (FDA)-approved drugs. By comparing disease-associated versus drug-induced differential expression profiles, we identified five potentially repurposable drugs, namely cabazitaxel, primaquine, pyrimethamine, trimethoprim and gliclazide. Preclinical studies may be con-ducted in vitro to validate these computational results. Interactome analysis of disease-associated genes is a powerful approach with high translational impact. It shows how MPM-associated genes identified by various high throughput studies are functionally linked, leading to clinically translatable results such as repurposed drugs. The PPIs are made available on a webserver with interactive user interface, visualization and advanced search capabilities.

Ovalitenone Inhibits the Migration of Lung Cancer Cells via the Suppression of AKT/mTOR and Epithelial-to-Mesenchymal Transition

Cancer metastasis is the major cause of about 90% of cancer deaths. As epithelial-to-mesenchymal transition (EMT) is known for potentiating metastasis, this study aimed to elucidate the effect of ovalitenone on the suppression of EMT and metastasis-related behaviors, including cell movement and growth under detached conditions, and cancer stem cells (CSCs), of lung cancer cells. Methods: Cell viability and cell proliferation were determined by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazo-liumbromide (MTT) and colony formation assays. Cell migration and invasion were analyzed using a wound-healing assay and Boyden chamber assay, respectively. Anchorage-independent cell growth was determined. Cell protrusions (filopodia) were detected by phalloidin-rhodamine staining. Cancer stem cell phenotypes were assessed by spheroid formation. The proteins involved in cell migration and EMT were evaluated by Western blot analysis and immunofluorescence staining. Results: Ovalitenone was used at concentrations of 0–200 μM. While it caused no cytotoxic effects on lung cancer H460 and A549 cells, ovalitenone significantly suppressed anchorage-independent growth, CSC-like phenotypes, colony formation, and the ability of the cancer to migrate and invade cells. The anti-migration activity was confirmed by the reduction of filopodia in the cells treated with ovalitenone. Interestingly, we found that ovalitenone could significantly decrease the levels of N-cadherin, snail, and slug, while it increased E-cadherin, indicating EMT suppression. Additionally, the regulatory signaling of focal adhesion kinase (FAK), ATP-dependent tyrosine kinase (AKT), the mammalian target of rapamycin (mTOR), and cell division cycle 42 (Cdc42) was suppressed by ovalitenone. Conclusions: The results suggest that ovalitenone suppresses EMT via suppression of the AKT/mTOR signaling pathway. In addition, ovalitenone exhibited potential for the suppression of CSC phenotypes. These data reveal the anti-metastasis potential of the compound and support the development of ovalitenone treatment for lung cancer therapy.

UBE2T promotes proliferation, invasion and glycolysis of breast cancer cells by regualting the PI3K/AKT signaling pathway

PURPOSE

Breast cancer (BCa) is one of the most common gynecological malignancies. Ubiquitin-coupled enzyme E2T (UBE2T) has been demonstrated to play crucial roles in various tumors.

METHODS

UBE2T levels were detected using quantitative real time PCR and western blot. CCK-8 and colony formation assays were used to evaluate cell proliferation. A xenograft model was used to evaluate the effects of UBE2T on tumor growth in mice, and immunohistochemistry (IHC) assay was performed to detect the expression of UBE2T and Ki-67. Transwell assay was performed to determine cell migration and invasion. The ATP level, glucose consumption and lactate production were measured using the corresponding commercial kits. Western blot assay was used to detect the levels of epithelial-mesenchymal transformation (EMT), glycolytic and the PI3K/AKT pathway related proteins regulated by UBE2T.

RESULTS

Upregulation of UBE2T expression in human BCa tissues was found in human clinical BCa tissues and The Cancer Genome Atlas (TCGA) dataset. The expression of UBE2T was confirmed to be up-regulated in BCa cells compared to normal breast epithelial cell line (MCF-10A). Overexpression of UBE2T promoted proliferation, migration, invasion and glycolysis in BCa cells, while UBE2T knockdown showed the opposite results. Moreover, UBE2T knockdown suppressed tumor growth in mice. Further mechanism analysis shows that UBE2T participated in the regulation of BCa progression through affecting the PI3K/AKT signaling pathway.

CONCLUSION

UBE2T promoted proliferation, invasion and glycolysis through modulating PI3K/AKT signaling pathway in BCa, implying that UBE2T may provide a promising therapeutic target for the therapy of BCa.

An Update on Pharmacological Potential of Boswellic Acids against Chronic Diseases

Natural compounds, in recent years, have attracted significant attention for their use in the prevention and treatment of diverse chronic diseases as they are devoid of major toxicities. Boswellic acid (BA), a series of pentacyclic triterpene molecules, is isolated from the gum resin of Boswellia serrata and Boswellia carteri. It proved to be one such agent that has exhibited efficacy against various chronic diseases like arthritis, diabetes, asthma, cancer, inflammatory bowel disease, Parkinson’s disease, Alzheimer’s, etc. The molecular targets attributed to its wide range of biological activities include transcription factors, kinases, enzymes, receptors, growth factors, etc. The present review is an attempt to demonstrate the diverse pharmacological uses of BA, along with its underlying molecular mechanism of action against different ailments. Further, this review also discusses the roadblocks associated with the pharmacokinetics and bioavailability of this promising compound and strategies to overcome those limitations for developing it as an effective drug for the clinical management of chronic diseases.

Identification of repurposed protein kinase B binders from FDA-approved drug library: a hybrid-structure activity relationship and systems modeling based approach

Food and Drug Administration (FDA)-approved drugs may be repurposed against those diseases, for which their therapeutic action has not been described. The present study deals with repurposing FDA-approved drugs for selective targeting of protein kinase B (PKB/Akt) for anti-cancer activity, through a two-tier (Cell and Target) model hybridization protocol implemented with support vector machine-based learning method. The hybridization was done as per rules of reaction kinetics. The hybridization process was facilitated as a standalone application for free access at https://github.com/undwivedi/Akt-Selective.git. The selectivity of the ligands for PKB/Akt binding was also evaluated on the basis of mitophagy system model for anti-apoptotic activity. Screening of the FDA-approved drug library, using the developed H- SAR model, led to identification of four compounds (Cas nos. 94749-08-3, 57808-66-9, 62-13-5, 76-43-7), bearing the selectivity for PKB/Akt. Since, the identified compounds have already crossed the barriers of absorption, distribution, metabolism, excretion, toxicity in clinical trials, therefore are safe to be considered for repurposing individually or in combination with other drugs.Communicated by Ramaswamy H. Sarma.

Suppression of Cell Growth, Migration and Drug Resistance by Ethanolic Extract of Antrodia cinnamomea in Human Lung Cancer A549 Cells and C57BL/6J Allograft Tumor Model

The purpose of this study was to investigate the inhibitory activities of ethanolic extracts from Antrodia cinnamomea (EEAC) on lung cancer. Cell proliferation and cell cycle distribution were analyzed using (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay and flow cytometry, respectively. Wound-healing assay, Western blotting, and a murine tumor model were separately used to examine cell migration, protein expression, and tumor repression. Our results showed that EEAC induced cell cycle arrest at the G0/G1 phase resulting decreased cell viability in A549 cells. Moreover, EEAC up-regulated the growth-suppressing proteins, adenosine 5′-monophosphate-activated protein kinase (AMPK), p21 and p27, but down-regulated the growth-promoting proteins, protein kinase B (Akt), mammalian tarfet of rapamycin (mTOR), extracellular signal-regulating kinase 1/2 (ERK1/2), retinoblastoma protein (Rb), cyclin E, and cyclin D1. EEAC also inhibited A549 cell migration and reduced expression of gelatinases. In addition, our data showed that tumor growth was suppressed after treatment with EEAC in a murine allograft tumor model. Some bioactive compounds from EEAC, such as cordycepin and zhankuic acid A, were demonstrated to reduce the protein expressions of matrix metalloproteinase (MMP)-9 and cyclin D1 in A549 cells. Furthermore, EEAC enhanced chemosensitivity of A549 to paclitaxel by reducing the protein levels of caveolin-1. Our data suggests that EEAC has the potential to be an adjuvant medicine for the treatment of lung cancer.

Swelling-induced chloride current in glioblastoma proliferation, migration, and invasion

Glioblastoma (GBM) remains as the most common and aggressive brain tumor. The survival of GBM has been linked to the aberrant activation of swelling-induced chloride current I_Cl,swell . In this study, we investigated the effects of I_Cl,swell on cell viability, proliferation, and migration in the human GBM cell lines, U251 and U87, using a combination of patch clamp electrophysiology, MTT, colony formation, wound healing assays and Western immunoblotting. First, we showed that the specific inhibitor of I_Cl,swell , DCPIB, potently reduced the I_Cl,swell in U87 cells. Next, in both U87 and U251 cells, we found that DCPIB reduced GBM viability, proliferation, colony formation, migration, and invasion. In addition, our Western immunoblot assay showed that DCPIB-treated U251 cells had a reduction in JAK2, STAT3, and Akt phosphorylation, thus, suggesting that DCPIB potentially suppresses GBM functions through inhibition of the JAK2/STAT3 and PI3K/Akt signaling pathways. Therefore, the I_Cl,swell may be a potential drug target for GBM.

Identification of a RAC/AKT-like gene in Leishmania parasites as a putative therapeutic target in leishmaniasis

Background

Leishmaniasis is one of the world’s most neglected diseases caused by at least 20 different species of the protozoan parasite Leishmania. Although new drugs have become recently available, current therapy for leishmaniasis is still unsatisfactory. A subgroup of serine/threonine protein kinases named as related to A and C protein kinases (RAC), or protein kinase B (PKB)/AKT, has been identified in several organisms including Trypanosoma cruzi parasites. PKB/AKT plays a critical role in mammalian cell signaling promoting cell survival and is a major drug target in cancer therapy. However, the role of protozoan parasitic PKB/AKT remains to be elucidated.

Results

We have found that anti-human AKT antibodies recognized a protein of about 57 kDa in Leishmania spp. parasites. Anti-human phospho-AKT(Thr308) antibodies identified a protein in extracts from Leishmania spp. that was upregulated following parasite exposure to stressful conditions, such as nutrient deprivation or heat shock. Incubation of AKT inhibitor X with Leishmania spp. promastigotes under stressful conditions or with Leishmania-infected macrophages led to parasite cell death. We have identified and cloned a novel gene from Leishmania donovani named Ld-RAC/AKT-like gene, encoding a 510-amino acid protein of approximately 57.6 kDa that shows a 26.5% identity with mammalian AKT1. Ld-RAC/AKT-like protein contains major mammalian PKB/AKT hallmarks, including the typical pleckstrin, protein kinase and AGC kinase domains. Unlike mammalian AKT that contains key phosphorylation sites at Thr308 and Ser473 in the activation loop and hydrophobic motif, respectively, Ld-RAC/AKT-like protein has a Thr residue in both motifs. By domain sequence comparison, we classified AKT proteins from different origins in four major subcategories that included different parasites.

Conclusions

Our data suggest that Ld-RAC/AKT-like protein represents a Leishmania orthologue of mammalian AKT involved in parasite stress response and survival, and therefore could become a novel therapeutic and druggable target in leishmaniasis therapy. In addition, following comparative sequence analyses, we found the RAC/AKT-like proteins from Leishmania constitute a subgroup by themselves within a general AKT-like protein family.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2379-y) contains supplementary material, which is available to authorized users.

How Selective are Hsp90 Inhibitors for Cancer Cells over Normal Cells?

Selectively inhibiting target proteins in cancer cells over normal cells is one of the most critical features of a successful protein inhibitor for clinical applications. By evaluating and comparing the impact of a clinical N-terminal heat shock protein 90 (Hsp90) inhibitor, AUY922 (luminespib), on Hsp90 inhibition-associated cellular events in cancer cells versus normal cells, we found that it produces similar phenotype characteristics in both cell types, indicating that AUY922 is not selective for targeting Hsp90 in tumor cells. By comparison, the C-terminal Hsp90 modulator SM258 suppresses cell proliferation, triggers apoptosis, regulates the expression of Hsp90-associated heat shock proteins, and enhances the degradation of Hsp90's client proteins preferentially in cancer cells over normal cells. Our findings support a new paradigm that AUY922 is not tumor selective, whereas SM258 is more selective and likely acts through an Hsp90-dependent mechanism.

Development of Certain Protein Kinase Inhibitors with the Components from Traditional Chinese Medicine

Traditional Chinese medicines (TCMs) have been used in China for more than two thousand years, and some of them have been confirmed to be effective in cancer treatment. Protein kinases play critical roles in control of cell growth, proliferation, migration, survival, and angiogenesis and mediate their biological effects through their catalytic activity. In recent years, numerous protein kinase inhibitors have been developed and are being used clinically. Anticancer TCMs represent a large class of bioactive substances, and some of them display anticancer activity via inhibiting protein kinases to affect the phosphoinositide 3-kinase, serine/threonine-specific protein kinases, pechanistic target of rapamycin (PI3K/AKT/mTOR), P38, mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinases (ERK) pathways. In the present article, we comprehensively reviewed several components isolated from anticancer TCMs that exhibited significantly inhibitory activity toward a range of protein kinases. These components, which belong to diverse structural classes, are reviewed herein, based upon the kinases that they inhibit. The prospects and problems in development of the anticancer TCMs are also discussed.

MK-2206 sensitizes BRCA-deficient epithelial ovarian adenocarcinoma to cisplatin and olaparib

BACKGROUND

Platinum resistance is a major obstacle in the treatment of epithelial ovarian cancer (EOC). Activation of the AKT pathway promotes platinum resistance while inhibition of AKT sensitizes chemoresistant cells. Patients with BRCA mutant EOC, and thus a defect in the homologous recombination (HR) repair pathway, demonstrate greater clinical response to platinum and olaparib therapy than patients with BRCA wild-type EOC. MK-2206, an allosteric inhibitor of AKT phosphorylation, sensitizes a variety of cell types to various anticancer agents and is currently undergoing phase II trials as monotherapy for platinum-resistant ovarian, fallopian tube, and peritoneal cancer. This study examines the differential effects of AKT inhibition with cisplatin and olaparib therapy in BRCA1/2-deficient versus wild-type EOC.

METHODS

PEO1, a chemosensitive BRCA2-mutant serous ovarian adenocarcinoma, and PEO4, a reverted BRCA2-proficient line from the same patient after the development of chemotherapeutic resistance, were primarily used for the study. In PEO1, MK-2206 demonstrated moderate to strong synergism with cisplatin and olaparib at all doses, while demonstrating antagonism at all doses in PEO4.

RESULTS

Baseline phospho-AKT activity in untreated cells was upregulated in both BRCA1- and 2-deficient cell lines. MK-2206 prevented cisplatin- and olaparib-induced AKT activation in the BRCA2-deficient PEO1 cells. We propose that BRCA-deficient EOC cells upregulate baseline AKT activity to enhance survival in the absence of HR. Higher AKT activity is also required to withstand cytotoxic agent-induced DNA damage, leading to strong synergism between MK-2206 and cisplatin or olaparib therapy in BRCA-deficient cells.

CONCLUSIONS

MK-2206 shows promise as a chemosensitization agent in BRCA-deficient EOC and merits clinical investigation in this patient population.

Identification of phenotype-relevant differentially expressed genes in breast cancer demonstrates enhanced quantile discretization protocol's utility in multi-platform microarray data integration

Microarray for transcriptomics experiments often suffer from limited statistical power due to small sample size. Quantile discretization (QD) maps expression values for a sample into a series of equivalently sized 'bins' that represent a discrete numerical range, e.g. [Formula: see text]4 to [Formula: see text]4, which enables normalized data from multiple experiments and/or expression platforms to be combined for re-analysis. We found, however, that informal selection of bin numbers often resulted in loss of the underlying correlation structure in the data through assigning of the same numerical value to genes that are in reality expressed at significantly different levels within a sample. Here we report a procedure for determining an optimal bin number for dataset. Applying this to integrated public breast cancer datasets enabled statistical identification of several differentially expressed tumorigenesis-related genes that were not found when analyzing the individual datasets, and also several cancer biomarkers not previously indicated as having utility in the disease. Notably, differential modulation of translational control and protein synthesis via multiple pathways were found to potentially have central roles in breast cancer development and progression. These findings suggest that our protocol has significant utility in making meaningful novel biomedical discoveries by leveraging the large public expression data repositories.

Anti-cancer activity of withaferin A in B-cell lymphoma

Withaferin A (WA), a withanolide from the plant, Ashwagandha (Withania somnifera) used in Ayurvedic medicine, has been found to be valuable in the treatment of several medical ailments. WA has been found to have anticancer activity against various solid tumors, but its effects on hematological malignancies have not been studied in detail. WA strongly inhibited the survival of several human and murine B cell lymphoma cell lines. Additionally, in vivo studies with syngeneic-graft lymphoma cells suggest that WA inhibits the growth of tumor but does not affect other proliferative tissues. We demonstrate that WA inhibits the efficiency of NF-κB nuclear translocation in diffuse large B cell lymphomas and found that WA treatment resulted in a significant decrease in protein levels involved in B cell receptor signaling and cell cycle regulation. WA inhibited the activity of heat shock protein (Hsp) 90 as reflected by a sharp increase in Hsp70 expression levels. Hence, we propose that the anti-cancer effects of WA in lymphomas are likely due to its ability to inhibit Hsp90 function and subsequent reduction of critical kinases and cell cycle regulators that are clients of Hsp90.

FXYD5: Na(+)/K(+)-ATPase Regulator in Health and Disease

FXYD5 (Dysadherin, RIC) is a single span type I membrane protein that plays multiple roles in regulation of cellular functions. It is expressed in a variety of epithelial tissues and acts as an auxiliary subunit of the Na⁺/K⁺-ATPase. During the past decade, a correlation between enhanced expression of FXYD5 and tumor progression has been established for various tumor types. In this review, current knowledge on FXYD5 is discussed, including experimental data on the functional effects of FXYD5 on the Na⁺/K⁺-ATPase. FXYD5 modulates cellular junctions, influences chemokine production, and affects cell adhesion. The accumulated data may provide a basis for understanding the molecular mechanisms underlying FXYD5 mediated phenotypes.

Combining an Hsp70 inhibitor with either an N- or C-terminal Hsp90 inhibitor produces mechanistically distinct phenotypes

Blocking the function of both heat shock protein 90 and 70 (Hsp90 and Hsp70) simultaneously limits these chaperones' cytoprotective effects on cancer cells. The unique phenotype associated with modulating Hsp90's C-terminus, when used in combination with Hsp70 inhibitors, produces a synergistic and highly relevant dual chemotherapy regimen.

Exploitation of the ability of γ-tocopherol to facilitate membrane co-localization of Akt and PHLPP1 to develop PHLPP1-targeted Akt inhibitors

Previously, we reported that Akt inactivation by γ-tocopherol (2) in PTEN-negative prostate cancer cells resulted from its unique ability to facilitate membrane co-localization of Akt and PHLPP1 (PH domain leucine-rich repeat protein phosphatase isoform 1), a Ser473-specific Akt phosphatase, through pleckstrin homology (PH) domain binding. This finding provided a basis for exploiting 2 to develop a novel class of PHLPP1-targeted Akt inhibitors. Here, we used 3 (γ-VE5), a side chain-truncated 2 derivative, as a scaffold for lead optimization. The proof-of-concept of this structural optimization was obtained by 20, which exhibited higher antitumor efficacy than 3 in PTEN-negative cancer cells through PHLPP1-facilitated Akt inactivation. Like 3, 20 preferentially recognized the PH domains of Akt and PHLPP1, as its binding affinities for other PH domains, including those of ILK and PDK1, were an order-of-magnitude lower. Moreover, 20 was orally active in suppressing xenograft tumor growth in nude mice, which underlines the translational potential of this new class of Akt inhibitor in PTEN-deficient cancers.

Cytotoxicity of obacunone and obacunone glucoside in human prostate cancer cells involves Akt-mediated programmed cell death

Obacunone and obacunone glucoside (OG) are naturally occurring triterpenoids commonly found in citrus and other plants of the Rutaceae family. The current study reports the mechanism of cytotoxicity of citrus-derived obacunone and OG on human androgen-dependent prostate cancer LNCaP cells. Both limonoids exhibited time- and dose-dependent inhibition of cell proliferation, with more than 60% inhibition of cell viability at 100 μM, after 24 and 48 h. Analysis of fragmentation of DNA, activity of caspase-3, and cytosolic cytochrome-c in the cells treated with limonoids provided evidence for activation of programmed cell death by limonoids. Treatment of LNCaP cells with obacunone and OG resulted in dose-dependent changes in expression of proteins responsible for the induction of programmed cell death through the intrinsic pathway and down-regulation of Akt, a key molecule in cell signaling pathways. In addition, obacunone and OG also negatively regulated an inflammation-associated transcription factor, androgen receptor, and prostate-specific antigen, and activated proteins related to the cell cycle, confirming the ability of limonoids to induce cytotoxicity through multiple pathways. The results of this study provided, for the first time, an evidence of the cytotoxicity of obacunone and OG in androgen-dependent human prostate cancer cells.

Understanding cancer and the anticancer activities of naphthoquinones – a review

Naphthoquinone moieties are present in drugs such as doxorubicin which are used clinically to treat solid cancers.

Curcumin ameliorate DENA-induced HCC via modulating TGF-β, AKT, and caspase-3 expression in experimental rat model

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. In laboratory animal models, diethylnitrosamine (DENA) is a well-known agent that has a potent hepatocarcinogenic effect that is used to induce HCC. As curcumin has a potent anti-inflammatory effect with strong therapeutic potential against a variety of cancers, our present study aims to investigate its curative effects and the possible mechanisms of action against DENA-induced HCC in male rats. Investigation of biochemical and molecular parameters of HCC animal model liver showed an overexpression of TGF-β and Akt proteins accompanied with a significant reduction of the proapoptotic marker caspase-3. DENA-induced hepatic cellular injury resulted also in a significant increase in liver function marker enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lipid peroxides in this group. Curcumin treatment partially reversed DENA-induced damage as it reduced the overexpression of the angiogenic and anti-apoptotic factors TGF-β and Akt and improved caspase-3 expression. Also, it could partially normalize the serum values of liver marker enzymes and lipid peroxidation and improve liver architecture. Curcumin shows a unique chemotherapeutic effect in reversing DENA-induced HCC in rat model. This effect is possibly mediated through its proapoptotic, antioxidant, anti-angiogenic, as well as antimitotic effects. It interferes and modulates cell signaling pathways and hence turns death signals and apoptosis on within tumor cells.

The hepatitis B virus (HBV) HBx protein activates AKT to simultaneously regulate HBV replication and hepatocyte survival

Chronic infection with hepatitis B virus (HBV) is a risk factor for developing liver diseases such as hepatocellular carcinoma (HCC). HBx is a multifunctional protein encoded by the HBV genome; HBx stimulates HBV replication and is thought to play an important role in the development of HBV-associated HCC. HBx can activate the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway in some cell lines; however, whether HBx regulates PI3K/AKT signaling in normal hepatocytes has not been evaluated. In studies described here, we assessed HBx activation of PI3K/AKT signaling in an ex vivo model of cultured primary hepatocytes and determined how this HBx activity affects HBV replication. We report that HBx activates AKT in primary hepatocytes and that the activation of AKT decreases HBV replication and HBV mRNA and core protein levels. We show that the transcription factor hepatocyte nuclear factor 4α (HNF4α) is a target of HBx-regulated AKT, and we link HNF4α to HBx-regulated AKT modulation of HBV transcription and replication. Although we and others have shown that HBx stimulates and is likely required for HBV replication, we now report that HBx also activates signals that can diminish the overall level of HBV replication. While this may seem counterintuitive, we show that an important effect of HBx activation of AKT is inhibition of apoptosis. Consequently, our studies suggest that HBx balances HBV replication and cell survival by stimulating signaling pathways that enhance hepatocyte survival at the expense of higher levels of HBV replication.

IMPORTANCE

Chronic hepatitis B virus (HBV) infection is a common cause of the development of liver cancer. Regulation of cell signaling pathways by the HBV HBx protein is thought to influence the development of HBV-associated liver cancer. HBx stimulates, and may be essential for, HBV replication. We show that HBx activates AKT in hepatocytes to reduce HBV replication. While this seems contradictory to an essential role of HBx during HBV replication, HBx activation of AKT inhibits hepatocyte apoptosis, and this may facilitate persistent, noncytopathic HBV replication. AKT regulates HBV replication by reducing the activity of the transcription factor hepatocyte nuclear factor 4α (HNF4α). HBx activation of AKT may contribute to the development of liver cancer by facilitating persistent HBV replication, augmenting the dedifferentiation of hepatocytes by inhibiting HNF4α functions, and activating AKT-regulated oncogenic pathways. AKT-regulated factors may provide therapeutic targets for inhibiting HBV replication and the development of HBV-associated liver cancer.

MADD is a downstream target of PTEN in triggering apoptosis

Mitogen-activated kinase activating death domain containing protein (MADD) is abundantly expressed in cancer cells and necessary for maintaining cancer cell survival. However, this survival function of MADD is dependent upon its phosphorylation by protein kinase B (Akt). The tumour suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a lipid phosphatase that negatively regulates the phosphatidylinositol 3-kinase (PI3K)-Akt signaling pathway. The downstream targets of PTEN in triggering apoptosis have not yet been completely identified. Here, we report that MADD can act as a pro-apoptotic factor to initiate TRAIL-induced apoptosis when its phosphorylation is attenuated by PTEN. Our data show that tumor necrosis factor α-related apoptosis-inducing ligand (TRAIL) induced a reduction in MADD phosphorylation with a concomitant up-regulation of PTEN. Knock down of PTEN using a specific siRNA prevented TRAIL-induced reduction in pMADD levels. Surprisingly, Akt non-phosphorylated MADD translocated from the plasma membrane to cytoplasm where it bound to 14-3-3 and displaced 14-3-3 associated Bax, which translocated to mitochondria resulting in cytochrome c release. Taken together, our data reveal that PTEN can convey the death signal by preventing MADD phosphorylation by Akt.

Role of Akt in human malignant glioma: from oncogenesis to tumor aggressiveness

Gathering evidence has revealed that Akt signaling pathway plays an important role in glioma progression and aggressiveness. Among Akt kinases the most studied, Akt1, has been involved in many cellular processes that are in favor of cell malignancy. More recently, the actions of the two other isoforms, Akt2 and Akt3 have emerged in glioma. After a description of Akt pathway activation, we will explore the role of each isoform in malignant glioma that strengthens the current preclinical and clinical studies evaluating the impact of Akt pathway targeting in glioblastomas.

Beauvericin ameliorates experimental colitis by inhibiting activated T cells via downregulation of the PI3K/Akt signaling pathway

Crohn's disease is a common, chronic inflammatory bowel condition characterized by remission and relapse. Accumulating evidence indicates that activated T cells play an important role in this disease. In the present study, we aimed to examine the effect of beauvericin, a natural cyclic peptide, on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice, which mimics Crohn's disease. Beauvericin significantly reduced weight loss, diarrhea and mortality, accompanied with notable alleviation of macroscopic and microscopic signs. In addition, this compound decreased serum levels of tumor necrosis factor (TNF)-α and interferon (IFN)- γ in a concentration-dependent manner in mice with experimental colitis. These effects of beauvericin are attributed to its inhibition on activated T cells. Flow cytometry and immunoblot assay data showed that beauvericin suppressed T-cell proliferation, activation and IFN-γ-STAT1-T-bet signaling and subsequently led to apoptosis of activated T cells by suppressing Bcl-2 and phosphorylated Bad as well as increasing cleavage of caspase-3, -9, -12 and PARP. Furthermore, inhibition of PI3K/Akt signaling, which was an upstream regulator of cell activation and survival in activated T cells, contributed to the effect of beauvericin. Overall, these results supported beauvericin as a novel drug candidate for the treatment of colonic inflammation mainly by targeting PI3K/Akt in activated T cells.

AKT kinase pathway: a leading target in cancer research

AKT1, a serine/threonine-protein kinase also known as AKT kinase, is involved in the regulation of various signalling downstream pathways including metabolism, cell proliferation, survival, growth, and angiogenesis. The AKT kinases pathway stands among the most important components of cell proliferation mechanism. Several approaches have been implemented to design an efficient drug molecule to target AKT kinases, although the promising results have not been confirmed. In this paper we have documented the detailed molecular insight of AKT kinase protein and proposed a probable doxorubicin based approach in inhibiting miR-21 based cancer cell proliferation. Moreover, the inhibition of miR-21 activation by raising the FOXO3A concentration seems promising in reducing miR-21 mediated cancer activation in cell. Furthermore, the use of next generation sequencing and computational drug design approaches will greatly assist in designing a potent drug molecule against the associated cancer cases.

Induction of apoptosis and suppression of angiogenesis of hepatocellular carcinoma by HS-159, a novel phosphatidylinositol 3-kinase inhibitor

The phosphatidylinositol 3-kinase (PI3K) pathway plays a central role in cell proliferation and survival in human cancer and is emerging as an attractive therapeutic target. In this study, we synthesized a novel PI3Kα inhibitor, HS-159 [N-(5-(3-(3-cyanophenyl)imidazo[1,2-a]pyridin-6-yl)pyridin-3-yl)benzenesulfonamide] and evaluated its anticancer effects on Huh-7 human hepatocellular carcinoma (HCC) cells. HS-159 effectively inhibited the phosphorylation of downstream PI3K effectors such as Akt, mTOR and P70S6 kinases in a dose-dependent manner. This compound also induced apoptosis and increased the fraction of apoptotic cells in the sub-G1 phase as well as the levels of cleaved PARP, caspase-3 and -9. Furthermore, HS-159 decreased the expression of hypoxia inducible factor-1α and vascular endothelial growth factor which play important roles in angiogenesis. The anti-angiogenic effect of HS-159 was confirmed by the suppression of tube formation and migration of human umbilical vein endothelial cells in vitro. Collectively, our results demonstrate that HS-159 exhibited anticancer activities including the induction of apoptosis and inhibition of angiogenesis by blocking the PI3K/Akt pathway in Huh-7 cells. Therefore, we suggest that this drug may be potentially used for targeted HCC therapy.

Cytotoxic effects of bromelain in human gastrointestinal carcinoma cell lines (MKN45, KATO-III, HT29-5F12, and HT29-5M21)

Background

Bromelain is a pineapple stem extract with a variety of therapeutic benefits arising from interaction with a number of different biological processes. Several preclinical studies and anecdotal clinical observations have reported the anticancer properties of bromelain. In the present study, we investigated the cytotoxic effects of bromelain in four human cancer cell lines of gastrointestinal origin and the mechanisms involved.

Methods

The gastric carcinoma cell lines (KATO-III and MKN45) and two chemoresistant subpopulations of the HT29 colon adenocarcinoma cell line (HT29-5M21 and HT29-5F12) were treated with a range of concentrations of bromelain, as well as with cisplatin as a positive control. The effect of bromelain on the growth and proliferation of cancer cells was determined using a sulforhodamine B assay after 72 hours of treatment. Expression of apoptosis-associated proteins in MKN45 cells treated with bromelain was analyzed by Western blotting.

Results

Data from our sulforhodamine B assay showed that bromelain inhibited proliferation of HT29-5F12, HT29-5M21, MKN45, and KATO-III cells, with respective half maximal inhibitory concentration values of 29, 34, 94, and 142 μg/mL. Analyzing the expression of proapoptotic and antiapoptotic proteins in bromelain-treated MKN45 cells, we observed activation of the caspase system, cleavage of PARP and p53, overexpression of cytochrome C, attenuation of phospho-Akt and Bcl2, and removal of MUC1. Apart from the caspase-dependent apoptosis observed, emergence of cleaved p53 supports a direct, extranuclear apoptotic function of p53. Moreover, interrupted Akt signaling and attenuation of Bcl2 and MUC1 oncoproteins suggest impaired survival of cancer cells.

Conclusion

Our findings collectively indicate that bromelain exerts cytotoxic effects in a panel of human gastric and colon carcinoma cells. Our study of MKN45 cells implicated different mechanisms in bromelain-induced cell death. While promoting apoptosis with involvement of the caspase system and extranuclear p53, bromelain also appears to impair cancer cell survival by blocking the Akt pathway and attenuating Bcl2 and MUC1 oncoproteins.

SZ-685C exhibits potent anticancer activity in both radiosensitive and radioresistant NPC cells through the miR-205-PTEN-Akt pathway

Radioresistance is a major obstacle to the treatment of human nasopharyngeal carcinoma (NPC). Emerging evidence has demonstrated that miRNAs are involved in cancer therapy resistance. Our research group established the radioresistant NPC cell line CNE2R derived from the CNE2 cell line, and demonstrated that irradiation-induced miR-205 determined the resistance of NPC through directly targeting PTEN. However, specific inhibitors targeting miRNAs are largely undetermined. SZ-685C was expected to abrogate the radioresistance of CNE2 cells through the miR-205‑PTEN-Akt pathway. SZ-685C exhibited a similar cytotoxic effect on both cell lines, and we demonstrated that both intrinsic and extrinsic pathways were activated by SZ-685C in the cell lines. Importantly, the miR-205-PTEN-Akt pathway was the key cell signaling pathway activated in the CNE2R cells upon SZ-685C treatment; however, the Stat3-Jab1-p27 pathway might participate in the pro-apoptotic effect in CNE2 cells but not in CNE2R cells. SZ-685C is a promising anticancer agent for treatment of NPC, and it exhibited pro-apoptotic activity in both radiosensitive and radioresistant NPC cells. Although the mechanisms between the two cell lines were not identical, the pro-apoptotic effects were similar between the two cell lines.

Investigation of radiation-induced transcriptome profile of radioresistant non-small cell lung cancer A549 cells using RNA-seq

Radioresistance is a main impediment to effective radiotherapy for non-small cell lung cancer (NSCLC). Despite several experimental and clinical studies of resistance to radiation, the precise mechanism of radioresistance in NSCLC cells and tissues still remains unclear. This result could be explained by limitation of previous researches such as a partial understanding of the cellular radioresistance mechanism at a single molecule level. In this study, we aimed to investigate extensive radiation responses in radioresistant NSCLC cells and to identify radioresistance-associating factors. For the first time, using RNA-seq, a massive sequencing-based approach, we examined whole-transcriptome alteration in radioresistant NSCLC A549 cells under irradiation, and verified significant radiation-altered genes and their chromosome distribution patterns. Also, bioinformatic approaches (GO analysis and IPA) were performed to characterize the radiation responses in radioresistant A549 cells. We found that epithelial–mesenchymal transition (EMT), migration and inflammatory processes could be meaningfully related to regulation of radiation responses in radioresistant A549 cells. Based on the results of bioinformatic analysis for the radiation-induced transcriptome alteration, we selected seven significant radiation-altered genes (SESN2, FN1, TRAF4, CDKN1A, COX-2, DDB2 and FDXR) and then compared radiation effects in two types of NSCLC cells with different radiosensitivity (radioresistant A549 cells and radiosensitive NCI-H460 cells). Interestingly, under irradiation, COX-2 showed the most significant difference in mRNA and protein expression between A549 and NCI-H460 cells. IR-induced increase of COX-2 expression was appeared only in radioresistant A549 cells. Collectively, we suggest that COX-2 (also known as prostaglandin-endoperoxide synthase 2 (PTGS2)) could have possibility as a putative biomarker for radioresistance in NSCLC cells.

Gan-Lu-Yin Inhibits Proliferation and Migration of Murine WEHI-3 Leukemia Cells and Tumor Growth in BALB/C Allograft Tumor Model

The aim of this study was to explore the antitumor effect of Gan-Lu-Yin (GLY), a traditional Chinese herbal formula, on leukemia. Ethanolic extract of GLY was applied to evaluate its regulatory mechanisms in proliferation, migration, and differentiation of WEHI-3 leukemic cells as well as antitumor effect on BALB/c mice model. The results showed that GLY markedly reduced cell proliferation and migration with induced differentiation of WEHI-3 cells. The expression level of phosphorylated FAK, Akt, ERK1/2, and Rb was decreased p21 expression while level was increased in WEHI-3 treated with GLY. The results of cell cycle analysis revealed that GLY treatment could markedly induce G1 phase arrest and decrease cell population in S phase. Moreover, experimental results demonstrated that GLY decreased the protein expression and enzyme activity of MMP-2 and MMP-9. GLY treatment also reduced WEHI-3 leukemic infiltration in liver and spleen and tumor growth in animal model. Accordingly, GLY demonstrated an inhibitory effect on tumor growth with a regulatory mechanism partially through inhibiting FAK, Akt, and ERK expression in WEHI-3 cells. GLY may provide a promising antileukemic approach in the clinical application.

Perifosine induces cell apoptosis in human osteosarcoma cells: new implication for osteosarcoma therapy?

Despite the advances of adjuvant chemotherapy and significant improvement of survival, the prognosis for patients with osteosarcoma is generally poor. The search for more effective anti-osteosarcoma agents is necessary and urgent. Here we report that perifosine induces cell apoptosis and growth inhibition in cultured human osteosarcoma cells. Perifosine blocks Akt/mTOR complex 1 (mTORC1) signaling, while promoting caspase-3, c-Jun N-terminal kinases (JNK), and p53 activation. Further, perifosine inhibits survivin expression probably by disrupting its association with heat shock protein-90 (HSP-90). These signaling changes together were responsible for a marked increase of osteosarcoma cell apoptosis and growth inhibition. Finally, we found that a low dose of perifosine enhanced etoposide- or doxorubicin-induced anti-OS cells activity. The results together suggest that perifosine might be used as a novel and effective anti-osteosarcoma agent.

Autocrine human GH promotes radioresistance in mammary and endometrial carcinoma cells

Although recent advances in breast cancer treatment regimes have improved patient prognosis, resistance to breast cancer therapies, such as radiotherapy, is still a major clinical challenge. In the current study, we have investigated the role of autocrine human GH (hGH) in resistance to ionising radiation (IR)-based therapy. Cell viability and total cell number assays demonstrated that autocrine hGH promoted cell regrowth in the mammary carcinoma cell lines, MDA-MB-435S and T47D, and the endometrial carcinoma cell line, RL95-2, following treatment with IR. In addition, autocrine hGH enhanced MDA-MB-435S and T47D cell clonogenic survival following radiation exposure. The enhanced clonogenic survival afforded by autocrine hGH was mediated by JAK2 and Src kinases. Investigation into the DNA repair capacity demonstrated that autocrine hGH reduced IR-induced DNA damage in MDA-MB-435S and T47D cells. Functional antagonism of hGH increased RL95-2 sensitivity to IR in cell viability and total cell number assays, reduced clonogenic survival and enhanced the induction of DNA damage. Thus, autocrine hGH reduced sensitivity to treatment with IR in mammary and endometrial carcinoma cell lines in vitro, while functional antagonism of hGH sensitised endometrial carcinoma cells to IR. Functional antagonism of hGH, used in conjunction with radiotherapy, may therefore enhance treatment efficacy and improve the prognosis of patients with breast and endometrial cancer.

Current treatment of cutaneous squamous cancer and molecular strategies for its sensitization to new target-based drugs

INTRODUCTION

Cutaneous squamous cell carcinoma (cSCC) is considered one of the most common skin malignancy with a relatively high risk of metastasis occurrence.

AREAS COVERED

We discuss the pathogenetic mechanisms of cSCC and the main therapeutic strategies available for the treatment of cSCC.

EXPERT OPINION

Chemotherapy and biological therapy with Interferon α (IFN-α) and cis retinoic acid are active but give limited results. Recently, strategies based on the use of molecularly target-based agents (MTA) have been used with promising results. Based on the available findings, we hypothesize that SCC cells can develop survival and resistance mechanisms to MTAs. The detection of these mechanisms could be useful in designing strategies able to overcome the latter and to potentiate the anticancer activity of MTAs. We describe the example of the EGF-dependent survival pathway elicited by IFN-α and the different strategies to abrogate this survival pathway. Other strategies to potentiate the antitumor activity of cytotoxic agents such as docetaxel or cisplatin are also discussed. Illuminating examples are the inhibition of multichaperone activity or the inactivation of the proteasome. In conclusion, a new dawn based upon the rationale use of MTAs is rising up in the treatment of advanced cSCC.

Combined inhibition of p38 and Akt signaling pathways abrogates cyclosporine A-mediated pathogenesis of aggressive skin SCCs

Non-melanoma skin cancers (NMSCs) are the most common neoplasm in organ transplant recipients (OTRs). These cancers are more invasive and metastatic as compared to those developed in normal cohorts. Previously, we have shown that immunosuppressive drug, cyclosporine A (CsA) directly alters tumor phenotype of cutaneous squamous cell carcinomas (SCCs) by activating TGF-β and TAK1/TAB1 signaling pathways. Here, we identified novel molecular targets for the therapeutic intervention of these SCCs. We observed that combined blockade of Akt and p38 kinases-dependent signaling pathways in CsA-promoted human epidermoid carcinoma A431 xenograft tumors abrogated their growth by more than 90%. This diminution in tumor growth was accompanied by a significant decrease in proliferation and an increase in apoptosis. The residual tumors following the combined treatment with Akt inhibitor triciribine and p38 inhibitors SB-203580 showed significantly diminished expression of phosphorylated Akt and p38 and these tumors were less invasive and highly differentiated. Diminished tumor invasiveness was associated with the reduced epithelial-mesenchymal transition as ascertained by the enhanced E-cadherin and reduced vimentin and N-cadherin expression. Consistently, these tumors also manifested reduced MMP-2/9. The decreased p-Akt expression was accompanied by a significant reduction in p-mTOR. These data provide first important combinatorial pharmacological approach to block the pathogenesis of CsA-induced highly aggressive cutaneous neoplasm in OTRs.

Deguelin, a natural rotenoid, inhibits mouse myeloma cell growth in vitro via induction of apoptosis

Deguelin is a naturally occurring rotenoid with strong cancer chemopreventive and antitumor activities. In the present study, we investigated the antitumor activity of deguelin against MPC-11 murine myeloma cells and the possible mechanism of action in vitro. Our results revealed that deguelin inhibited the proliferation of MPC-11 cells in a concentration- and time-dependent manner and caused the apoptotic death of MPC-11 cells. Following exposure to deguelin, the phosphorylation of Akt was decreased. The inhibition of cell growth may be associated with decreased levels of phosphorylated Akt. Deguelin-induced apoptosis was characterized by the upregulation of Bax, downregulation of Bcl-2 and activation of caspase-3. In conclusion, deguelin inhibits murine myeloma cell proliferation by inducing apoptosis via regulation of the Bax/Bcl-2 ratio and by inhibition of the activation of Akt. Its potential as an anticancer agent against multiple myeloma warrants further investigation.

Dysadherin expression promotes the motility and survival of human breast cancer cells by AKT activation

High dysadherin expression has been recognized as a biological predictor of metastasis and poor prognosis for many different cancer types; however, the molecular mechanisms of how dysadherin affects cancer progression are still poorly understood. In this study, we examined whether AKT signaling could link dysadherin expression with downstream events that promote the metastatic potential of human breast cancer cells. Immunohistochemical analysis of breast cancer tissues showed that dysadherin expression was highly associated with elevated expression of phospho-AKT. The introduction of dysadherin cDNA into BT-474, MCF-7 and T-47D breast cancer cell lines enhanced their levels of AKT phosphorylation, while knockdown of dysadherin in MDA-MB-231 and Hs578T breast cancer cell lines suppressed AKT phosphorylation. Treatment with the AKT inhibitor triciribine suppressed dysadherin-mediated pro-metastatic effects, including epithelial-mesenchymal transition, cell motility and drug resistance. These findings suggest that dysadherin might contribute to breast cancer progression through AKT activation.

DC120, a novel and potent inhibitor of AKT kinase, induces tumor cell apoptosis and suppresses tumor growth

Protein kinase B/AKT kinase is the core component of the phosphatidylinositol 3-kinase/AKT signaling pathway, which is frequently hyperactivated in human cancers. We designed and synthesized a series of 2-pyrimidyl-5-amidothiazole compounds based on the ATP binding site of AKT, and the most potent compound, (S)-N-(1-amino-3-(2,4-dichlorophenyl)propan-2-yl)-2-(2-(methylamino)pyrimidin-4-yl)thiazole-5-carboxamide (DC120), was identified to inhibit AKT activity in vitro with an EC(50) of 153 nM by a fluorescence resonance energy transfer-based Z'-LYTE assay. The antitumor effect of DC120 was tested on human CNE2 and MDA-MB-453 cell lines and the CNE2 xenograft model. The results showed that DC120 could obviously inhibit the proliferation of CNE2 and MDA-MB-453 cells via induction of apoptosis, with the evidence of increases in sub-G(1) and annexin V-positive cells, characteristic morphologic changes of apoptosis in the nucleus, and cleaved caspase-3. Further study showed that MDA-MB-453 cells transfected with constitutively activated AKT1 were more sensitive to DC120,whereas CNE2 cells with knockdown of AKT1 expression by short hairpin RNA were more resistant to DC120. Of more importance, DC120 partially attenuated the phosphorylation levels of forkhead transcription factor (FKHR), FKHRL1, glycogen synthase kinase 3β, and mammalian target of rapamycin in a dose-dependent and time-dependent fashion and led to an increase in the nuclear accumulation of exogenous FKHR in cancer cells. In addition, DC120 at 20 mg/kg/day inhibited the CNE2 xenograft tumor growth with a treated group/control group ratio of 38.1%, accompanied by increasing terminal deoxynucleotidyl transferasedUTP nick-end labeling-positive cells in the tumor sample. In addition, DC120 induced a feedback loop to activate the mitogen-activated protein kinase pathway and treatment with mitogen-activated protein kinase kinase inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(methylthio)butadiene (U0126) and DC120 synergistically induced cancer cell apoptosis. These data provide validation for the development of DC120 to treat cancers displaying elevated levels of AKT.

Akt: a double-edged sword in cell proliferation and genome stability

The Akt family of serine/threonine protein kinases are key regulators of multiple aspects of cell behaviour, including proliferation, survival, metabolism, and tumorigenesis. Growth-factor-activated Akt signalling promotes progression through normal, unperturbed cell cycles by acting on diverse downstream factors involved in controlling the G1/S and G2/M transitions. Remarkably, several recent studies have also implicated Akt in modulating DNA damage responses and genome stability. High Akt activity can suppress ATR/Chk1 signalling and homologous recombination repair (HRR) via direct phosphorylation of Chk1 or TopBP1 or, indirectly, by inhibiting recruitment of double-strand break (DSB) resection factors, such as RPA, Brca1, and Rad51, to sites of damage. Loss of checkpoint and/or HRR proficiency is therefore a potential cause of genomic instability in tumor cells with high Akt. Conversely, Akt is activated by DNA double-strand breaks (DSBs) in a DNA-PK- or ATM/ATR-dependent manner and in some circumstances can contribute to radioresistance by stimulating DNA repair by nonhomologous end joining (NHEJ). Akt therefore modifies both the response to and repair of genotoxic damage in complex ways that are likely to have important consequences for the therapy of tumors with deregulation of the PI3K-Akt-PTEN pathway.

Emerging treatment options for the treatment of neuroblastoma: potential role of perifosine

Achieving a cure for high-risk neuroblastoma, the most common extracranial solid tumor in children, remains a formidable task despite the recent addition of antibody-mediated anti-GD2 immunotherapy to established multimodality therapy. The PI3K/Akt pathway is a pivotal signaling pathway utilized by a plethora of receptor tyrosine kinases that contribute to the aggressive phenotype of high-risk neuroblastoma. Akt is aberrantly activated in high-risk neuroblastoma and is therefore an attractive therapeutic target. Perifosine is the best-characterized Akt inhibitor in preclinical studies and in clinical trials in adults, although safety in children is not yet confirmed. It is a synthetic third-generation alkylphospholipid with good oral bioavailability and modest side effects. Perifosine targets the lipid-binding PH domain of Akt and inhibits the translocation of Akt to the cell membrane, an essential step for Akt activation. It decreases Akt phosphorylation and increases caspase-dependent apoptosis in neuroblastoma cell lines, inhibits growth of neuroblastoma xenografts, and overcomes RTK/ligand-mediated chemoresistance. It is currently being studied in two Phase I clinical trials in children with recurrent or refractory solid tumors including neuroblastoma. In the single agent trial (ClinicalTrials.gov identifier NCT00776867), maximum tolerated dose has not yet been reached and pharmacokinetic data has been accrued. In the second study (ClinicalTrials.gov identifier NCT01049841), patients are treated with a combination of perifosine and the mTOR-inhibitor temsirolimus based on preclinical data showing synergy of the two agents, and the premise that direct Akt inhibition may overcome Akt activation secondary to mTOR inhibition. Based on results from adult trials, it is unlikely that perifosine alone will produce dramatic therapeutic effects against high-risk neuroblastoma. However, given the recent encouraging early-phase combination therapy results in adults with multiple myeloma and colorectal carcinoma, rational perifosine-containing combination regimens hold promise for neuroblastoma therapy. These will be explored after safety in children is established in Phase I studies.

Bmi-1 induces radioresistance in MCF-7 mammary carcinoma cells

Bmi-1, a member of the polycomb family, it is involved in self renewal of stem cells and functions as an oncogene in many malignant human cancer types. Recent studies have demonstrated that Bmi-1 is a predictive factor for poor patient prognosis. However, the underlying mechanisms of radioresistance mediated by Bmi-1 are poorly understood. In this study, the dose-survival relationship was analyzed using a clonogenic survival assay and combined radiation treatment with Bmi-1 overexpression or silencing. DNA double-strand break (DSB) and repair was assessed by immunofluorescence staining of γH2AX foci. In addition, mitochondrial membrane potential was detected between Bmi-1 knockdown and control MCF-7 cells after irradiation. Apoptosis and cell cycle were evaluated by flow cytometry. We found that exposure of MCF-7 cells overexpressing Bmi-1 to ionizing radiation resulted in dramatically enhanced survival relative to control cells, whereas cells with silenced Bmi-1 showed markedly reduced survival. Bmi-1 inhibition significantly increased DSBs and decreased DSB repair. Furthermore, Bmi-1 knockdown induced loss of mitochondrial membrane potential and enhanced apoptosis by up-regulating p53, p21, Bax expression and down-regulating p-AKT and Bcl-2 expression. These results indicate that Bmi-1 may play an important role in radiosensitivity, and the suppression of its expression might be a potential therapeutic target for breast cancer.

The Akt signaling pathway: an emerging therapeutic target in malignant melanoma

Studies using cultured melanoma cells and patient tumor biopsies have demonstrated deregulated PI3 kinase-Akt3 pathway activity in ~70% of melanomas. Furthermore, targeting Akt3 and downstream PRAS40 has been shown to inhibit melanoma tumor development in mice. Although these preclinical studies and several other reports using small interfering RNAs and pharmacological agents targeting key members of this pathway have been shown to retard melanoma development, analysis of early Phase I and Phase II clinical trials using pharmacological agents to target this pathway demonstrate the need for (1) selection of patients whose tumors have PI3 kinase-Akt pathway deregulation, (2) further optimization of therapeutic agents for increased potency and reduced toxicity, (3) the identification of additional targets in the same pathway or in other signaling cascades that synergistically inhibit the growth and progression of melanoma, and (4) better methods for targeted delivery of pharmaceutical agents inhibiting this pathway. In this review we discuss key potential targets in PI3K-Akt3 signaling, the status of pharmacological agents targeting these proteins, drugs under clinical development, and strategies to improve the efficacy of therapeutic agents targeting this pathway.