MK-2206, an allosteric Akt inhibitor, enhances antitumor efficacy by standard chemotherapeutic agents or molecular targeted drugs in vitro and in vivo

Systems pharmacology using mass spectrometry identifies critical response nodes in prostate cancer

In the United States alone one in five newly diagnosed cancers in men are prostate carcinomas (PCa). Androgen receptor (AR) status and the PI3K-AKT-mTOR signal transduction pathway are critical in PCa. After initial response to single drugs targeting these pathways resistance often emerges, indicating the need for combination therapy. Here, we address the question of efficacy of drug combinations and development of resistance mechanisms to targeted therapy by a systems pharmacology approach. We combine targeted perturbation with detailed observation of the molecular response by mass spectrometry. We hypothesize that the molecular short-term (24 h) response reveals details of how PCa cells adapt to counter the anti-proliferative drug effect. With focus on six drugs currently used in PCa treatment or targeting the PI3K-AKT-mTOR signal transduction pathway, we perturbed the LNCaP clone FGC cell line by a total of 21 treatment conditions using single and paired drug combinations. The molecular response was analyzed by the mass spectrometric quantification of 52 proteins. Analysis of the data revealed a pattern of strong responders, i.e., proteins that were consistently downregulated or upregulated across many of the perturbation conditions. The downregulated proteins, HN1, PAK1, and SPAG5, are potential early indicators of drug efficacy and point to previously less well-characterized response pathways in PCa cells. Some of the upregulated proteins such as 14-3-3 proteins and KLK2 may be useful early markers of adaptive response and indicate potential resistance pathways targetable as part of combination therapy to overcome drug resistance. The potential of 14-3-3ζ (YWHAZ) as a target is underscored by the independent observation, based on cancer genomics of surgical specimens, that its DNA copy number and transcript levels tend to increase with PCa disease progression. The combination of systematic drug perturbation combined with detailed observation of short-term molecular response using mass spectrometry is a potentially powerful tool to discover response markers and anti-resistance targets.

Metastatic prostate cancer is often treated with pharmacological agents to prevent the tumor from expanding; however, despite advances in drug development patients often die of the disease. An international research team lead by Ruedi Aebersold (ETH Zürich, Switzerland) and Chris Sander (Dana Faber Cancer Institute, Boston, USA) asked how prostate cancer cells adapt to pharmacological treatment on the molecular protein level and find a general response in their prostate cancer model. Next, they asked if similar changes are found in prostate cancer patients. Indeed, the same proteins upregulated in prostate cancer models are also upregulated in prostate cancer patients. Immediately, this has implications for patient treatment stratification and opens new avenues for drug developments in metastatic prostate cancer.

CK2 inhibition confers functional protection to young and aging axons against ischemia by differentially regulating the CDK5 and AKT signaling pathways

White matter (WM) is injured in most strokes, which contributes to functional deficits during recovery. Casein kinase 2 (CK2) is a protein kinase that is expressed in brain, including WM. To assess the impact of CK2 inhibition on axon recovery following oxygen glucose deprivation (OGD), mouse optic nerves (MONs), which are pure WM tracts, were subjected to OGD with or without the selective CK2 inhibitor CX-4945. CX-4945 application preserved axon function during OGD and promoted axon function recovery when applied before or after OGD. This protective effect of CK2 inhibition correlated with preservation of oligodendrocytes and conservation of axon structure and axonal mitochondria. To investigate the pertinent downstream signaling pathways, siRNA targeting the CK2α subunit identified CDK5 and AKT as downstream molecules. Consequently, MK-2206 and roscovitine, which are selective AKT and CDK5 inhibitors, respectively, protected young and aging WM function only when applied before OGD. However, a novel pan-AKT allosteric inhibitor, ARQ-092, which targets both the inactive and active conformations of AKT, conferred protection to young and aging axons when applied before or after OGD. These results suggest that AKT and CDK5 signaling contribute to the WM functional protection conferred by CK2 inhibition during ischemia, while inhibition of activated AKT signaling plays the primary role in post-ischemic protection conferred by CK2 inhibition in WM independent of age. CK2 inhibitors are currently being used in clinical trials for cancer patients; therefore, our results will provide rationale for repurposing these drugs as therapeutic options for stroke patients by adding novel targets.

microRNA-29a inhibition induces Gab1 upregulation to protect OB-6 human osteoblasts from hydrogen peroxide

The present study determines the role of the Gab1 in hydrogen peroxide (H₂O₂)-induced death of human osteoblasts. We show that Gab1 is required for H₂O₂-induced Akt activation to promote osteoblast survival. In OB-6 human osteoblasts, Gab1 silencing (by targeted-shRNA) or complete knockout (by CRISPR-Cas9 KO plasmid) largely attenuated Akt activation by H₂O₂. Gab1-depleted OB-6 cells were more vulnerable to H₂O₂. Conversely, forced over-expression of Gab1 by an adenovirus vector increased Akt activation to protect OB-6 cells from H₂O₂. Significantly, the anti-sense of microRNA-29a ("antagomiR-29a") induced Gab1 expression to facilitate H₂O₂-induced Akt activation, which protected OB-6 cells from apoptosis. AntagomiR-29a was however ineffective in Gab1-deficient and Akt-inhibited OB-6 cells. Forced over-expression of miR-29a induced Gab1 downregulation to inhibit H₂O₂-induced Akt activation, causing enhanced OB-6 cell death. miR-29a-induced actions were abolished by an adenovirus constitutively-active Akt1 (Ad-caAkt1) in OB-6 cells. Together, microRNA-29a inhibition induces Gab1 upregulation and Akt activation to protect OB-6 osteoblasts from H₂O₂.

AKT signalling selectively regulates PINK1 mitophagy in SHSY5Y cells and human iPSC-derived neurons

The discovery of mutations within genes associated with autosomal recessive Parkinson's disease allowed for the identification of PINK1/Parkin regulated mitophagy as an important pathway for the removal of damaged mitochondria. While recent studies suggest that AKT-dependent signalling regulates Parkin recruitment to depolarised mitochondria, little is known as to whether this can also regulate PINK1 mitochondrial accumulation and downstream mitophagy. Here, we demonstrate that inhibition of AKT signalling decreases endogenous PINK1 accumulation in response to mitochondria depolarisation, subsequent Parkin recruitment, phosphorylation of ubiquitin, and ultimately mitophagy. Conversely, we show that upon stimulation of AKT signalling via insulin, the mitophagy pathway is increased in SHSY5Y cells. These data suggest that AKT signalling is an upstream regulator of PINK1 accumulation on damaged mitochondria. Importantly, we show that the AKT pathway also regulates endogenous PINK1-dependent mitophagy in human iPSC-derived neurons.

Association between EGFR/KRAS mutation and expression of VEGFA, VEGFR and VEGFR2 in lung adenocarcinoma

Epidermal growth factor receptor (EGFR) and Kirsten rat sarcoma viral oncogene homolog (KRAS) are two of the most notable driver genes in lung cancer, whilst vascular endothelial growth factor (VEGF) signaling serves a critical function in tumor angiogenesis. However, few studies have focused on the potential connection between EGFR/KRAS mutational status, and VEGFA, VEGF receptor (VEGFR)1 and VEGFR2 expression in lung adenocarcinoma. EGFR (exon 19, 20 and 21) and KRAS (exon 2) mutations were detected using an amplification refractory mutation system technique, and the expression of VEGFA, VEGFR1 and VEGFR2 was analyzed using immunohistochemistry in 204 patients with lung adenocarcinoma. Associations between EGFR/KRAS mutational status and VEGFA, VEGFR1, and VEGFR2 expression was analyzed using Pearson χ² tests. It was revealed that EGFR 21 exon (P=0.033) and EGFR 20 exon (P=0.002) mutated tumors exhibited a significantly higher level of expression of VEGFA. EGFR 21 exon mutant tumors additionally demonstrated a significantly higher level of co-expression of VEGFA and VEGFR1 (P<0.001). EGFR 19 exon mutation was significantly associated with low levels of VEGFR1 (P=0.008). KRAS mutation was significantly associated with a high level of co-expression of VEGFA, VEGFR1 and VEGFR2 (P=0.035), but no such association with the individual expression of VEGFA, VEGFR1 or VEGFR2 was identified. However, neither KRAS or EGFR mutations exhibited an association with the expression of VEGFR2. The present study may help in the treatment of various patients with KRAS or subtype of EGFR mutation with anti-angiogenesis therapy.

(S)-crizotinib reduces gastric cancer growth through oxidative DNA damage and triggers pro-survival akt signal

Gastric cancer (GC), a common gastrointestinal malignancy worldwide, has poor prognosis and frequent recurrence. There is a great need to identify effective therapy for GC. Crizotinib is a multi-targeted, clinically available oral tyrosine kinase inhibitor approved for lung cancer, but its use for the highly heterogeneous disease of GC is unknown. The goal of this study was to investigate the anti-cancer mechanisms of the (S)-crizotinib in inhibiting GC growth. Human GC cell lines (SGC-7901 and BGC-823) and the (S)-crizotinib-resistant BGC-823/R were cultured for determining the effects of (S)-crizotinib on cell viability, apoptosis, oxidant generation, and cell cycle progression. Involvement of ROS, Akt signaling, MTH1, and DNA damage was tested with respective pharmacological blockade. The in vivo anti-tumor effects of (S)-crizotinib were determined using xenograft tumor mice. Results indicated that (S)-crizotinib decreased GC cell viability, induced growth arrest and apoptosis, and increased levels of γH2AX and Ser1981-phosphorylated ATM, which were inhibited by NAC. The anti-cancer mechanism of (S)-crizotinib was independent of MTH1. Moreover, ATM-activated Akt, a pro-survival signal, whose inhibition further enhanced (S)-crizotinib-induced inhibition of GC cell growth and tumor growth in xenograft mice, and re-sensitized resistant GC cells to (S)-crizotinib. (S)-crizotinib reduced GC cell and tumor growth through oxidative DNA damage mechanism and triggered pro-survival Akt signaling. We conclude that inclusion of Akt inhibition (to block the survival signaling) with (S)-crizotinib may provide an effective and novel combination therapy for GC in the clinical setting.

Inhibitor of apoptosis proteins (IAPs) mediate collagen type XI alpha 1-driven cisplatin resistance in ovarian cancer

Although, cisplatin resistance is a major challenge in the treatment of ovarian cancer, the precise mechanisms underlying cisplatin resistance are not fully understood. Collagen type XI alpha 1 (COL11A1), a gene encoding a minor fibrillar collagen of the extracellular matrix, is identified as one of the most upregulated genes in cisplatin-resistant ovarian cancer and recurrent ovarian cancer. However, the exact functions of COL11A1 in cisplatin resistance are unknown. Here we demonstrate that COL11A1 binds to integrin α1β1 and discoidin domain receptor 2 (DDR2) and activates downstream signaling pathways to inhibit cisplatin-induced apoptosis in ovarian cancer cells. Mechanistically, we show that COL11A1 activates Src-PI3K/Akt-NF-kB signaling to induce the expression of three inhibitor apoptosis proteins (IAPs), including XIAP, BIRC2, and BIRC3. Genetic and pharmacological inhibition of XIAP, BIRC2, and BIRC3 is sufficient to restore cisplatin-induced apoptosis in ovarian cancer cells in the presence of COL11A1 in ovarian cancer cells and xenograft mouse models, respectively. We also show that the components of COL11A1- integrin α1β1/DDR2- Src-PI3K/Akt-NF-kB-IAP signaling pathway serve as poor prognosis markers in ovarian cancer patients. Taken together, our results suggest novel mechanisms by which COL11A1 confers cisplatin resistance in ovarian cancer. Our study also uncovers IAPs as promising therapeutic targets to reduce cisplatin resistance in ovarian cancer, particularly in recurrent ovarian cancer expressing high levels of COL11A1.

Concurrent interactome and metabolome analysis reveals role of AKT1 in central carbon metabolism

Objective

Signal transduction not only initiates entry into the cell cycle, but also reprograms the cell’s metabolism. To control abnormalities in cell proliferation, both the aspects should be taken care of, thus pleiotropic signaling molecules are considered as crucial modulators. Considering this, we investigated the role of AKT1 in central carbon metabolism. The role of AKT1 has already been established in the process of cell cycle, but its contribution to the central carbon metabolism is sparsely studied.

Results

To address this, we combined the metabolomics and proteomics approaches. In accordance to our hypothesis, we found that the AKT1 kinase activity is regulating the levels of acetyl CoA through pyruvate dehydrogenase complex. Further, the decreased levels of acetyl CoA and dependency of acetyl CoA acetyl transferase protein on AKT1 kinase activity was also found to perturb the synthesis rate of palmitic acid which is a representative of fatty acid. This was analyzed in the present study using lipid labeling method through mass spectrometry.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3364-z) contains supplementary material, which is available to authorized users.

PI3K/AKT/mTOR pathway inhibitors inhibit the growth of melanoma cells with mTOR H2189Y mutations in vitro

mTOR is an important therapeutic target in many types of cancers. In melanoma, the mTOR nonsynonymous mutation rate is up to 10.4%. However, mTOR inhibitors have shown limited effects in clinical trials of melanoma. Because mTOR mutations are distributed, not selecting patients with specific mTOR mutations may be the main reason for therapeutic failures. Our previous research found that mutations in the mTOR P2213S and S2215Y kinase domains resulted in gain-of-function and were sensitive to specific inhibitors. The purpose of this study was to test the effect of heterozygous/homozygous H2189Y mutations on downstream pathways and sensitivity to inhibitors. mTOR kinase activity was analyzed by western blot and a K-LISA™ mTOR activity kit. The sensitivity of melanoma cells to inhibitors was tested by a proliferation assay. The expression of downstream pathway proteins was also analyzed by western blot. The results showed that heterozygous/homozygous H2189Y mutations were gain-of-function. The heterozygous H2189Y mutation was sensitive to the AKT inhibitor, AZD5363, and the phosphoinositide 3-kinase inhibitor, LY294002. The homozygous H2189Y mutation was sensitive to the mTOR inhibitor, everolimus, and the AKT inhibitors AZD5363 and MK-2206 2HCL,and the phosphoinositide 3-kinase inhibitor, LY294002. These results indicated that homozygous mutations in the kinase domain have a greater effect on protein function than heterozygous mutations. The mTOR kinase domain may play an important role in mTOR kinase activity and may be the target of selective inhibitors. Our study can facilitate the selection of appropriate inhibitors for patients in clinical trials.

IL-17A promotes the invasion-metastasis cascade via the AKT pathway in hepatocellular carcinoma

We previously demonstrated that interleukin‐17A (IL‐17A) is associated with the progression of hepatocellular carcinoma (HCC). However, its role in the invasion–metastasis cascade of HCC and the efficacy of IL‐17A‐targeting therapeutics in HCC remain largely unknown. In this study, we found that IL‐17A promoted intrahepatic and pulmonary metastasesis of HCC cells in an orthotopic implant model. Moreover, our results showed that IL‐17A induced epithelial–mesenchymal transition (EMT) and promoted HCC cell colonization in vitro and in vivo, and the role of IL‐17A in invasion–metastasis was dependent on activation of the AKT pathway. Remarkably, combined therapy using both secukinumab and sorafenib has better inhibition on tumour growth and metastasis compared to sorafenib monotherapy. Additionally, the combination of intratumoral IL‐17A+ cells and E‐cadherin predicted the outcome of patients with HCC at an early stage after hepatectomy based on tissue microarray and immunohistochemistry. In conclusion, our studies reveal that IL‐17A induces early EMT and promotes late colonization of HCC metastasis by activating AKT signalling. Secukinumab is a promising candidate for clinical development in combination with sorafenib for the management of HCC.

Targeting the phosphatidylinositol 3-kinase/Akt/mechanistic target of rapamycin signaling pathway in B-lineage acute lymphoblastic leukemia: An update

Despite considerable progress in treatment protocols, B-lineage acute lymphoblastic leukemia (B-ALL) displays a poor prognosis in about 15-20% of pediatric cases and about 60% of adult patients. In addition, life-long irreversible late effects from chemo- and radiation therapy, including secondary malignancies, are a growing problem for leukemia survivors. Targeted therapy holds promising perspectives for cancer treatment as it may be more effective and have fewer side effects than conventional therapies. The phosphatidylinositol 3-phosphate kinase (PI3K)/Akt/mechanistic target of rapamycin (mTOR) signaling pathway is a key regulatory cascade which controls proliferation, survival and drug-resistance of cancer cells, and it is frequently upregulated in the different subtypes of B-ALL, where it plays important roles in the pathophysiology, maintenance and progression of the disease. Moreover, activation of this signaling cascade portends a poorer prognosis in both pediatric and adult B-ALL patients. Promising preclinical data on PI3K/Akt/mTOR inhibitors have documented their anticancer activity in B-ALL and some of these novel drugs have entered clinical trials as they could lead to a longer event-free survival and reduce therapy-associated toxicity for patients with B-ALL. This review highlights the current status of PI3K/Akt/mTOR inhibitors in B-ALL, with an emphasis on emerging evidence of the superior efficacy of synergistic combinations involving the use of traditional chemotherapeutics or other novel, targeted agents.

Activation of Akt characterizes estrogen receptor positive human breast cancers which respond to anthracyclines

Anthracyclines are key components of human breast cancer chemotherapy. Here, we explored the role of Akt signaling in anthracycline resistance.

The antitumor activity of doxorubicin and Akt inhibitor A-443654 alone or combined was examined in estrogen receptor (ER) positive and negative human breast cancer cell lines. Further, we examined mRNA changes induced by anthracyclines in locally advanced breast cancers biopsied before and after treatment in two clinical trials.

Doxorubicin increased Akt phosphorylation in ER positive MCF7 and T47D cell lines, with no effect in ER negative MDA-MB231 breast cancer cells. A-443654 was significantly more cytotoxic in doxorubicin-resistant compared to doxorubicin-naïve MCF7. This difference was not observed in MDA-MB231. Among 24 patients, AKT1 gene expression increased 24 hrs after the initial epirubicin exposure in ER positive tumors responding to therapy (n=6), as compared to ER positive non-responders (n=7) or ER negative tumors (n=11). In contrast, AKT1 mRNA changes after 16 weeks of doxorubicin were unrelated to clinical response and ER status (n=30).

In conclusion, rapid Akt activation was observed in ER positive breast cancers which responded to anthracyclines. Increased cytotoxicity of A-443654 in doxorubicin-resistant MCF7 cells indicates a possible role for Akt inhibitors in ER positive breast cancers where chemoresistance evolves.

Bufalin Enhances the Cytotoxity of Human Multiple Myeloma Cells H929 to AKT Inhibitor MK2206: The Role of Protein AKT Phosphorylation

This study was purposed to investigate bufalin combined with AKT inhibitor MK2206 on growth inhibition and apoptosis of multiple myeloma cell line H929. CCK-8 assay and Annexin/PI staining were used to access the effects of bufalin and MK2206 in single or in combination, on inhibition of proliferation and induction of apoptosis in H929 cells. The apoptotic cells markedly increased after treated with nM bufalin and μM MK2206, including caspase3 and PARP1 proteins activated. The difference was statistically significant (P < 0.05) when compared with these drugs in single use. The apoptosis associated proteins and AKT/p-AKT proteins were determined by Western blots. We confirmed that AKT performed contradictory results in H929 with the two agents, and concluded p-AKT was vital in the synergy. The underlying mechanisms warrant further investigation.

Discovery of chiral dihydropyridopyrimidinones as potent, selective and orally bioavailable inhibitors of AKT

During the course of our research efforts to develop potent and selective AKT inhibitors, we discovered enatiomerically pure substituted dihydropyridopyrimidinones (DHP) as potent inhibitors of protein kinase B/AKT with excellent selectivity against ROCK₂. A key challenge in this program was the poor physicochemical properties of the initial lead compound 5. Integration of structure-based drug design and physical properties-based design resulted in replacement of a highly hydrophobic poly fluorinated aryl ring by a simple trifluoromethyl that led to identification of compound 6 with much improved physicochemical properties. Subsequent SAR studies led to the synthesis of new pyran analog 7 with improved cell potency. Further optimization of pharmacokintetics properties by increasing permeability with appropriate fluorinated alkyl led to compound 8 as a potent, selective AKT inhibitors that blocks the phosphorylation of GSK3β in vivo and had robust, dose and concentration dependent efficacy in the U87MG tumor xenograft model.

microRNA-200a downregulation in human glioma leads to Gαi1 over-expression, Akt activation, and cell proliferation

We previously identified a pivotal role for G protein α inhibitory subunit 1 (Gαi1) in mediating PI3K-Akt signaling by receptor tyrosine kinases (RTKs). Here, we examined the expression and biological function of Gαi1 in human glioma. Gαi1 mRNA and protein expression were significantly upregulated in human glioma tissues, which correlated with downregulation of an anti-Gαi1 miRNA: microRNA-200a ("miR-200a"). Forced-expression of miR-200a in established (A172/U251MG lines) and primary (patient-derived) human glioma cells resulted in Gαi1 downregulation, Akt inactivation and proliferation inhibition. Reduction of Gαi1 expression by shRNA, dominant negative mutant interference, or complete Gαi1 depletion inhibited Akt activation and cell proliferation. Notably, miR-200a was unable to inhibit glioma cell proliferation when Gαi1 was silenced or mutated. Co-immunoprecipitation studies, in human glioma cells and tissues, show that Gαi1 forms a complex with multiple RTKs (EGFR, PDGFRα, and FGFR) and the adapter protein Gab1. In vivo, the growth of subcutaneous and orthotopic glioma xenografts in nude mice was largely inhibited by expression of Gαi1 shRNA or miRNA-200a. Collectively, miR-200a downregulation in human glioma leads to Gαi1 over-expression, Akt activation and glioma cell proliferation.

Cell-geometry-dependent changes in plasma membrane order direct stem cell signalling and fate

Cell size and shape affect cellular processes such as cell survival, growth and differentiation^1-4, thus establishing cell geometry as a fundamental regulator of cell physiology. The contributions of the cytoskeleton, specifically actomyosin tension, to these effects have been described, but the exact biophysical mechanisms that translate changes in cell geometry to changes in cell behaviour remain mostly unresolved. Using a variety of innovative materials techniques, we demonstrate that the nanostructure and lipid assembly within the cell plasma membrane are regulated by cell geometry in a ligand-independent manner. These biophysical changes trigger signalling events involving the serine/threonine kinase Akt/protein kinase B (PKB) that direct cell-geometry-dependent mesenchymal stem cell differentiation. Our study defines a central regulatory role by plasma membrane ordered lipid raft microdomains in modulating stem cell differentiation with potential translational applications.

Sei-1 promotes double minute chromosomes formation through activation of the PI3K/Akt/BRCA1-Abraxas pathway and induces double-strand breaks in NIH-3T3 fibroblasts

Sei-1 is a potential oncogene that plays an important role in promoting genomic instability. Double minute chromosomes (DMs) are hallmarks of gene amplification and contribute to tumorigenesis. Defects in the DNA double-strand break (DSB) repairing pathways can lead to gene amplification. To date, the mechanisms governing the formation of DMs induced by Sei-1 are not fully understood. We established DMs induced by Sei-1 in the NIH-3T3 cell line. RNA-sequencing was used to identify key characteristics of differentially expressed genes. Metaphase spreads were used to calculate DM numbers. Immunofluorescence was employed to detect γH2AX foci. Western blot and Akt pathway inhibition experiments were performed to reveal the role of the PI3K/Akt/BRCA1-Abraxas pathway in Sei-1-induced DMs. Luciferase reporter assay was employed to explore the regulatory mechanisms between Sei-1 and BRCA1. DM formation was associated with a deficiency in DSB repair. Based on this finding, activation of the PI3K/Akt/BRCA1-Abraxas pathway was found to increase the DM population with passage in vivo, and inhibition resulted in a reduction of DMs. Apart from this, it was shown for the first time that Sei-1 could directly regulate the expression of BRCA1. Our results suggest that the PI3K/Akt/BRCA1-Abraxas pathway is responsible for the formation of DMs induced by Sei-1.

PHLDA1 Mediates Drug Resistance in Receptor Tyrosine Kinase-Driven Cancer

Development of resistance causes failure of drugs targeting receptor tyrosine kinase (RTK) networks and represents a critical challenge for precision medicine. Here, we show that PHLDA1 downregulation is critical to acquisition and maintenance of drug resistance in RTK-driven cancer. Using fibroblast growth factor receptor (FGFR) inhibition in endometrial cancer cells, we identify an Akt-driven compensatory mechanism underpinned by downregulation of PHLDA1. We demonstrate broad clinical relevance of our findings, showing that PHLDA1 downregulation also occurs in response to RTK-targeted therapy in breast and renal cancer patients, as well as following trastuzumab treatment in HER2+ breast cancer cells. Crucially, knockdown of PHLDA1 alone was sufficient to confer de novo resistance to RTK inhibitors and induction of PHLDA1 expression re-sensitized drug-resistant cancer cells to targeted therapies, identifying PHLDA1 as a biomarker for drug response and highlighting the potential of PHLDA1 reactivation as a means of circumventing drug resistance.

Akt isoform specific effects in ovarian cancer progression

Ovarian cancer remains a significant therapeutic problem and novel, effective therapies are needed. Akt is a serine-threonine kinase that is overexpressed in numerous cancers, including ovarian. Mammalian cells express three Akt isoforms which are encoded by distinct genes. Although there are several Akt inhibitors in clinical trials, most indiscriminately target all isoforms. Current in vitro data and animal knockout experiments suggest that the Akt isoforms may have divergent roles. In this paper, we determined the isoform-specific functions of Akt in ovarian cancer cell proliferation in vitro and in ovarian cancer progression in vivo. For in vitro experiments, murine and human ovarian cancer cells were treated with Akt inhibitors and cell viability was assessed. We used two different in vivo approaches to identify the roles of Akt isoforms in ovarian cancer progression and their influence on the primary tumor and tumor microenvironment. In one experiment, wild-type C57Bl6 mice were orthotopically injected with ID8 cells with stable knockdown of Akt isoforms. In a separate experiment, mice null for Akt 1-3 were orthotopically injected with WT ID8 cells (Figure 1). Our data show that inhibition of Akt1 significantly reduced ovarian cancer cell proliferation and inhibited tumor progression in vivo. Conversely, disruption of Akt2 increased tumor growth. Inhibition of Akt3 had an intermediate phenotype, but also increased growth of ovarian cancer cells. These data suggest that there is minimal redundancy between the Akt isoforms in ovarian cancer progression. These findings have important implications in the design of Akt inhibitors for the effective treatment of ovarian cancer.

A-674563, a putative AKT1 inhibitor that also suppresses CDK2 activity, inhibits human NSCLC cell growth more effectively than the pan-AKT inhibitor, MK-2206

AKT is a serine-threonine kinase implicated in tumorigenesis as a central regulator of cellular growth, proliferation, survival, and metabolism. Activated AKT is commonly overexpressed in non-small cell lung cancer (NSCLC) and accordingly AKT inhibitors are under clinical investigation for NSCLC treatment. Thus far, the AKT inhibitors being evaluated broadly target all three (1–3) AKT isoforms but recent evidence suggests opposing roles in lung tumorigenesis where loss of Akt1 inhibits while the loss of Akt2 enhances lung tumor development. Based on these findings, we hypothesized that selective inhibition of AKT-1 would be a more effective therapeutic strategy than pan-AKT inhibition for NSCLC treatment. Using six NSCLC cell lines, we found that the AKT-1 inhibitor, A-674563, was significantly more effective at reducing NSCLC cell survival relative to the pan-AKT inhibitor MK-2206. Comparison of the downstream effects of the inhibitors suggests that altered cell cycle progression and off-target CDK2 inhibition are likely vital to the improved efficacy of A-674563 over MK-2206.

Icariside II activates EGFR-Akt-Nrf2 signaling and protects osteoblasts from dexamethasone

The potential effect of icariside II on dexamethasone-induced osteoblast cell damages was evaluated here. In MC3T3-E1 osteoblastic cells and the primary murine osteoblasts, co-treatment with icariside II dramatically attenuated dexamethasone- induced cell death and apoptosis. Icariside II activated Akt signaling, which is required for its actions in osteoblasts. Akt inhibitors (LY294002, perifosine and MK-2206) almost abolished icariside II-induced osteoblast cytoprotection against dexamethasone. Further studies showed that icariside II activated Nrf2 signaling, downstream of Akt, to inhibit dexamethasone-induced reactive oxygen species (ROS) production in MC3T3-E1 cells and primary osteoblasts. On the other hand, Nrf2 shRNA knockdown inhibited icariside II-induced anti-dexamethasone cytoprotection in MC3T3-E1 cells. Finally, we showed that icariside II induced heparin-binding EGF (HB-EGF) production and EGFR trans-activation in MC3T3-E1 cells. EGFR inhibition, via anti-HB-EGF antibody, EGFR inhibitor AG1478 or EGFR shRNA knockdown, almost blocked icariside II-induced Akt-Nrf2 activation in MC3T3-E1 cells. Collectively, we conclude that icariside II activates EGFR-Akt-Nrf2 signaling and protects osteoblasts from dexamethasone. Icariside II might have translational value for the treatment of dexamethasone-associated osteoporosis/osteonecrosis.

Mitomycin C treatment induces resistance and enhanced migration via phosphorylated Akt in aggressive lung cancer cells

Since 1984, mitomycin C (MMC) has been applied in the treatment of non-small-cell lung cancer (NSCLC). MMC-based chemotherapeutic regimens are still under consideration owing to the efficacy and low cost as compared with other second-line regimens in patients with advanced NSCLC. Hence, it is important to investigate whether MMC induces potential negative effects in NSCLC. Here, we found that the malignant lung cancer cells, CL1-2 and CL1-5, were more resistant to MMC than were the parental CL1-0 cells and pre-malignant CL1-1 cells. CL1-2 and CL1-5 cells consistently showed lower sub-G1 fractions post MMC treatment. DNA repair-related proteins were not induced more in CL1-5 than in CL1-0 cells, but the levels of endogenous and MMC-induced phosphorylated Akt (p-Akt) were higher in CL1-5 cells. Administering a p-Akt inhibitor reduced the MMC resistance, demonstrating that p-Akt is important in the MMC resistance of CL1-5 cells. Furthermore, we revealed that cell migration was enhanced by MMC but lowered by a p-Akt inhibitor in CL1-5 cells. This study suggests that in CL1-5 cells, the activity of p-Akt, rather than DNA repair mechanisms, may underlie the resistance to MMC and enhance the cells' migration abilities after MMC treatment.

PIM Kinases Are a Potential Prognostic Biomarker and Therapeutic Target in Neuroblastoma

The majority of high-risk neuroblastoma patients are refractory to, or relapse on, current treatment regimens, resulting in 5-year survival rates of less than 50%. This emphasizes the urgent need to identify novel therapeutic targets. Here, we report that high PIM kinase expression is correlated with poor overall survival. Treatment of neuroblastoma cell lines with the pan-PIM inhibitors AZD1208 or PIM-447 suppressed proliferation through inhibition of mTOR signaling. In a panel of neuroblastoma cell lines, we observed a marked binary response to PIM inhibition, suggesting that specific genetic lesions control responses to PIM inhibition. Using a genome-wide CRISPR-Cas9 genetic screen, we identified NF1 loss as the major resistance mechanism to PIM kinase inhibitors. Treatment with AZD1208 impaired the growth of NF1 wild-type xenografts, while NF1 knockout cells were insensitive. Thus, our data indicate that PIM inhibition may be a novel targeted therapy in NF1 wild-type neuroblastoma. Mol Cancer Ther; 17(4); 849-57. ©2018 AACR.

Kinase inhibitors as potential agents in the treatment of multiple myeloma

Recent years have witnessed a dramatic increase in the number of therapeutic options available for the treatment of multiple myeloma (MM) - from immunomodulating agents to proteasome inhibitors to histone deacetylase (HDAC) inhibitors and, most recently, monoclonal antibodies. Used in conjunction with autologous hematopoietic stem cell transplantation, these modalities have nearly doubled the disease's five-year survival rate over the last three decades to about 50%. In spite of these advances, MM still is considered incurable as resistance and relapse are common. While small molecule protein kinase inhibitors have made inroads in the therapy of a number of cancers, to date their application to MM has been less than successful. Focusing on MM, this review examines the roles played by a number of kinases in driving the malignant state and the rationale for target development in the design of a number of kinase inhibitors that have demonstrated anti-myeloma activity in both in vitro and in vivo xenograph models, as well as those that have entered clinical trials. Among the targets and their inhibitors examined are receptor and non-receptor tyrosine kinases, cell cycle control kinases, the PI3K/AKT/mTOR pathway kinases, protein kinase C, mitogen-activated protein kinase, glycogen synthase kinase, casein kinase, integrin-linked kinase, sphingosine kinase, and kinases involved in the unfolded protein response.

An automated epifluorescence microscopy imaging assay for the identification of phospho-AKT level modulators in breast cancer cells

AKT is an enzyme of the PI3K/pAKT pathway, regulating proliferation and cell survival. High basal levels of active, phosphorylated AKT (pAKT) are associated with tumor progression and therapeutic resistance in some breast cancer subtypes, including HER2 positive breast cancers. Various stimuli can increase pAKT levels and elevated basal pAKT levels are a feature of PTEN-deficient breast cancer cell lines. The aim of this study was to develop an assay able to identify modulators of pAKT levels using an automated epifluorescence microscope and high content analysis. To develop this assay, we used HCC-1569, a PTEN-deficient, HER2-overexpressing breast cancer cell line with elevated basal pAKT levels. HCC-1569 cells were treated with a selective pharmacological inhibitor of AKT (MK-2206) to reduce basal pAKT levels or EGF to increase pAKT levels. Immunofluorescence images were acquired using an automated epifluorescence microscope and integrated intensity of cytoplasmic pAKT staining was calculated using high content analysis software. Mean and median integrated cytoplasmic intensity were normalized using fold change and standard score to assess assay quality and to identify most robust data analysis. The highest z' factor was achieved for median data normalization using the standard score method (z' = 0.45). Using our developed assay we identified the calcium homeostasis regulating proteins TPRV6, STIM1 and TRPC1 as modulators of pAKT levels in HCC-1569 cells. Calcium signaling controls a diverse array of cellular processes and some calcium homeostasis regulating proteins are involved in modulating pAKT levels in cancer cells. Thus, these identified hits present promising targets for further assessment.

Healthy CD4+ T lymphocytes are not affected by targeted therapies against the PI3K/Akt/mTOR pathway in T-cell acute lymphoblastic leukemia

An attractive molecular target for novel anti-cancer therapies is the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway which is commonly deregulated in many types of cancer. Nevertheless, the effects of PI3K/Akt/mTOR inhibitors on T lymphocytes, a key component of immune responses, have been seldom explored. In this study we investigated the effects on human CD4+ T-cells of a panel of PI3K/Akt/mTOR inhibitors: BGT226, Torin-2, MK-2206, and ZSTK474. We also assessed their efficacy against two acute leukemia T cell lines. T lymphocytes were stimulated with phytohemagglutinin. Inhibitor effects on cell cycle and apoptosis were analyzed by flow cytometry, while cytotoxicity was assessed by MTT assays. In addition, the activation status of the pathway as well as induction of autophagy were analyzed by Western blotting. Quiescent healthy T lymphocytes were unaffected by the drugs whereas mitogen-stimulated lymphocytes as well as leukemic cell lines displayed a cell cycle block, caspase-dependent apoptosis, and dephosphorylation of key components of the signaling pathway. Autophagy was also induced in proliferating lymphocytes and in JURKAT and MOLT-4 cell lines. When autophagy was inhibited by 3-methyladenine or Bafilomycin A1, drug cytotoxicity was increased, indicating that autophagy is a protective mechanism. Therefore, our findings suggest that PI3K/Akt/mTOR inhibitors preserve lymphocyte viability. This is a valuable result to be taken into account when selecting drugs for targeted cancer therapy in order to minimize detrimental effects on immune function.

SC79 protects retinal pigment epithelium cells from UV radiation via activating Akt-Nrf2 signaling

Excessive Ultra-violet (UV) radiation causes oxidative damages and apoptosis in retinal pigment epithelium (RPE) cells. Here we tested the potential activity of SC79, a novel small molecule activator of Akt, against the process. We showed that SC79 activated Akt in primary and established (ARPE-19 line) RPE cells. It protected RPE cells from UV damages possibly via inhibiting cell apoptosis. Akt inhibition, via an Akt specific inhibitor (MK-2206) or Akt1 shRNA silence, almost abolished SC79-induced RPE cytoprotection. Further studies showed that SC79 activated Akt-dependent NF-E2-related factor 2 (Nrf2) signaling and inhibited UV-induced oxidative stress in RPE cells. Reversely, Nrf2 shRNA knockdown or S40T mutation attenuated SC79-induced anti-UV activity. For the in vivo studies, we showed that intravitreal injection of SC79 significantly protected mouse retina from light damages. Based on these results, we suggest that SC79 protects RPE cells from UV damages possibly via activating Akt-Nrf2 signaling axis.

PHLPP1 mediates melanoma metastasis suppression through repressing AKT2 activation

PI3K/AKT pathway activation is thought to be a driving force in metastatic melanomas. Members of the pleckstrin homology (PH) domain leucine-rich repeat protein Ser/Thr specific phosphatase family (PHLPP1 and PHLPP2) can regulate AKT activation. By dephosphorylating specific serine residues in the hydrophobic motif, PHLPP1 and PHLPP2 restrain AKT signalings, thereby regulating cell proliferation and survival. We here show that PHLPP1 expression was significantly downregulated or lost and correlated with metastatic potential in melanoma. Forcing expression of either PHLPP1 or PHLPP2 in melanoma cells inhibited cell proliferation, migration, and colony formation in soft agar; but PHLPP1 had the most profound inhibitory effect on metastasis. Moreover, expression of PH mutant forms of PHLPP1 continued to inhibit metastasis, whereas a phosphatase-dead C-terminal mutant did not. The introduction of activated PHLPP1-specific targets AKT2 or AKT3 also promoted melanoma metastasis, while the non-PHLPP1 target AKT1 did not. AKT2 and AKT3 could even rescue the PHLPP1-mediated inhibition of metastasis. An AKT inhibitor blocked the activity of AKT2 and inhibited AKT2-mediated tumor growth and metastasis in a preclinical mouse model. Our data demonstrate that PHLPP1 functions as a metastasis suppressor through its phosphatase activity, and suggest that PHLPP1 represents a novel diagnostic and therapeutic marker for metastatic melanoma.

Expanding primary cells from mucoepidermoid and other salivary gland neoplasms for genetic and chemosensitivity testing

Restricted availability of cell and animal models is a rate-limiting step for investigation of salivary gland neoplasm pathophysiology and therapeutic response. Conditionally reprogrammed cell (CRC) technology enables establishment of primary epithelial cell cultures from patient material. This study tested a translational workflow for acquisition, expansion and testing of CRC-derived primary cultures of salivary gland neoplasms from patients presenting to an academic surgical practice. Results showed that cultured cells were sufficient for epithelial cell-specific transcriptome characterization to detect candidate therapeutic pathways and fusion genes, and for screening for cancer risk-associated single nucleotide polymorphisms (SNPs) and driver gene mutations through exome sequencing. Focused study of primary cultures of a low-grade mucoepidermoid carcinoma demonstrated amphiregulin-mechanistic target of rapamycin-protein kinase B (AKT; AKT1) pathway activation, identified through bioinformatics and subsequently confirmed as present in primary tissue and preserved through different secondary 2D and 3D culture media and xenografts. Candidate therapeutic testing showed that the allosteric AKT inhibitor MK2206 reproducibly inhibited cell survival across different culture formats. By contrast, the cells appeared resistant to the adenosine triphosphate competitive AKT inhibitor GSK690693. Procedures employed here illustrate an approach for reproducibly obtaining material for pathophysiological studies of salivary gland neoplasms, and other less common epithelial cancer types, that can be executed without compromising pathological examination of patient specimens. The approach permits combined genetic and cell-based physiological and therapeutic investigations in addition to more traditional pathologic studies, and can be used to build sustainable bio-banks for future inquiries.This article has an associated First Person interview with the first author of the paper.

Targeting RAS-driven human cancer cells with antibodies to upregulated and essential cell-surface proteins

While there have been tremendous efforts to target oncogenic RAS signaling from inside the cell, little effort has focused on the cell-surface. Here, we used quantitative surface proteomics to reveal a signature of proteins that are upregulated on cells transformed with KRAS^G12V, and driven by MAPK pathway signaling. We next generated a toolkit of recombinant antibodies to seven of these RAS-induced proteins. We found that five of these proteins are broadly distributed on cancer cell lines harboring RAS mutations. In parallel, a cell-surface CRISPRi screen identified integrin and Wnt signaling proteins as critical to RAS-transformed cells. We show that antibodies targeting CDCP1, a protein common to our proteomics and CRISPRi datasets, can be leveraged to deliver cytotoxic and immunotherapeutic payloads to RAS-transformed cancer cells and report for RAS signaling status in vivo. Taken together, this work presents a technological platform for attacking RAS from outside the cell.

Crosstalk between the IGF-1R/AKT/mTORC1 pathway and the tumor suppressors p53 and p27 determines cisplatin sensitivity and limits the effectiveness of an IGF-1R pathway inhibitor

The insulin-like growth factor-1 receptor (IGF-1R) signaling pathway is aberrantly activated in multiple cancers and can promote proliferation and chemotherapy resistance. Multiple IGF-1R inhibitors have been developed as potential therapeutics. However, these inhibitors have failed to increase patient survival when given alone or in combination with chemotherapy agents. The reason(s) for the disappointing clinical effect of these inhibitors is not fully understood. Cisplatin (CP) activated the IGF-1R/AKT/mTORC1 pathway and stabilized p53 in osteosarcoma (OS) cells. p53 knockdown reduced IGF-1R/AKT/mTORC1 activation by CP, and IGF-1R inhibition reduced the accumulation of p53. These data demonstrate positive crosstalk between p53 and the IGF-1R/AKT/mTORC1 pathway in response to CP. Further studies showed the effect of IGF-1R inhibition on CP response is dependent on p53 status. In p53 wild-type cells treated with CP, IGF-1R inhibition increased p53s apoptotic function but reduced p53-dependent senescence, and had no effect on long term survival. In contrast, in p53-null/knockdown cells, IGF-1R inhibition reduced apoptosis in response to CP and increased long term survival. These effects were due to p27 since IGF-1R inhibition stabilized p27 in CP-treated cells, and p27 depletion restored apoptosis and reduced long term survival. Together, the results demonstrate 1) p53 expression determines the effect of IGF-1R inhibition on cancer cell CP response, and 2) crosstalk between the IGF-1R/AKT/mTORC1 pathway and p53 and p27 can reduce cancer cell responsiveness to chemotherapy and may ultimately limit the effectiveness of IGF-1R pathway inhibitors in the clinic.

The transcription factor RUNX2 regulates receptor tyrosine kinase expression in melanoma

Receptor tyrosine kinases-based autocrine loops largely contribute to activate the MAPK and PI3K/AKT pathways in melanoma. However, the molecular mechanisms involved in generating these autocrine loops are still largely unknown. In the present study, we examine the role of the transcription factor RUNX2 in the regulation of receptor tyrosine kinase (RTK) expression in melanoma. We have demonstrated that RUNX2-deficient melanoma cells display a significant decrease in three receptor tyrosine kinases, EGFR, IGF-1R and PDGFRβ. In addition, we found co-expression of RUNX2 and another RTK, AXL, in both melanoma cells and melanoma patient samples. We observed a decrease in phosphoAKT2 (S474) and phosphoAKT (T308) levels when RUNX2 knock down resulted in significant RTK down regulation. Finally, we showed a dramatic up regulation of RUNX2 expression with concomitant up-regulation of EGFR, IGF-1R and AXL in melanoma cells resistant to the BRAF V600E inhibitor PLX4720. Taken together, our results strongly suggest that RUNX2 might be a key player in RTK-based autocrine loops and a mediator of resistance to BRAF V600E inhibitors involving RTK up regulation in melanoma.

Foxo-dependent Par-4 Upregulation Prevents Long-term Survival of Residual Cells Following PI3K-Akt Inhibition

Tumor recurrence is a leading cause of death and is thought to arise from a population of residual cells that survive treatment. These residual cancer cells can persist, locally or at distant sites, for years or decades. Therefore, understanding the pathways that regulate residual cancer cell survival may suggest opportunities for targeting these cells to prevent recurrence. Previously, it was observed that the proapoptotic protein (PAWR/Par-4) negatively regulates residual cell survival and recurrence in mice and humans. However, the mechanistic underpinnings on how Par-4 expression is regulated are unclear. Here, it is demonstrated that Par-4 is transcriptionally upregulated following treatment with multiple drugs targeting the PI3K-Akt-mTOR signaling pathway, and identify the Forkhead family of transcription factors as mediators of this upregulation. Mechanistically, Foxo3a directly binds to the Par-4 promoter and activates its transcription following inhibition of the PI3K-Akt pathway. This Foxo-dependent Par-4 upregulation limits the long-term survival of residual cells following treatment with therapeutics that target the PI3K-Akt pathway. Taken together, these results indicate that residual breast cancer tumor cell survival and recurrence requires circumventing Foxo-driven Par-4 upregulation and suggest that approaches to enforce Par-4 expression may prevent residual cell survival and recurrence. Mol Cancer Res; 16(4); 599-609. ©2018 AACR.

Progress with covalent small-molecule kinase inhibitors

With reduced risk of toxicity and high selectivity, covalent small-molecule kinase inhibitors (CSKIs) have emerged rapidly. Through the lens of structural system pharmacology, here we review this rapid progress by considering design strategies and the challenges and opportunities offered by current CSKIs.

Dual inhibition of AKT/FLT3-ITD by A674563 overcomes FLT3 ligand-induced drug resistance in FLT3-ITD positive AML

The FLT3-ITD mutation is one of the most prevalent oncogenic mutations in AML. Several FLT3 kinase inhibitors have shown impressive activity in clinical evaluation, however clinical responses are usually transient and clinical effects are rapidly lost due to drug resistance. One of the resistance mechanisms in the AML refractory patients involves FLT3-ligand induced reactivation of AKT and/or ERK signaling via FLT3 wt kinase. Via a screen of numerous AKT kinase inhibitors, we identified the well-established orally available AKT inhibitor, A674563, as a dual suppressor of AKT and FLT3-ITD. A674563 suppressed FLT3-ITD positive AML both in vitro and in vivo. More importantly, compared to other FLT3 inhibitors, A674563 is able to overcome FLT3 ligand-induced drug resistance through simultaneous inhibition of FLT3-ITD- and AKT-mediated signaling. Our findings suggest that A674563 might be a potential drug candidate for overcoming FLT3 ligand-mediated drug resistance in FLT3-ITD positive AML.

Calcineurin complex isolated from T-cell acute lymphoblastic leukemia (T-ALL) cells identifies new signaling pathways including mTOR/AKT/S6K whose inhibition synergize with calcineurin inhibition to promote T-ALL cell death

Calcineurin (Cn) is a calcium activated protein phosphatase involved in many aspects of normal T cell physiology, however the role of Cn and/or its downstream targets in leukemogenesis are still ill-defined. In order to identify putative downstream targets/effectors involved in the pro-oncogenic activity of Cn in T-cell acute lymphoblastic leukemia (T-ALL) we used tandem affinity chromatography, followed by mass spectrometry to purify novel Cn-interacting partners. We found the Cn-interacting proteins to be part of numerous cellular signaling pathways including eIF2 signaling and mTOR signaling. Coherently, modulation of Cn activity in T-ALL cells determined alterations in the phosphorylation status of key molecules implicated in protein translation such as eIF-2α and ribosomal protein S6. Joint targeting of PI3K-mTOR, eIF-2α and 14-3-3 signaling pathways with Cn unveiled novel synergistic pro-apoptotic drug combinations. Further analysis disclosed that the synergistic interaction between PI3K-mTOR and Cn inhibitors was prevalently due to AKT inhibition. Finally, we showed that the synergistic pro-apoptotic response determined by jointly targeting AKT and Cn pathways was linked to down-modulation of key anti-apoptotic proteins including Mcl-1, Claspin and XIAP. In conclusion, we identify AKT inhibition as a novel promising drug combination to potentiate the pro-apoptotic effects of Cn inhibitors.

Mechanism of activation of SGK3 by growth factors via the Class 1 and Class 3 PI3Ks

Derailment of the PI3K-AGC protein kinase signalling network contributes to many human diseases including cancer. Recent work has revealed that the poorly studied AGC kinase family member, SGK3, promotes resistance to cancer therapies that target the Class 1 PI3K pathway, by substituting for loss of Akt kinase activity. SGK3 is recruited and activated at endosomes, by virtue of its phox homology domain binding to PtdIns(3)P. Here, we demonstrate that endogenous SGK3 is rapidly activated by growth factors such as IGF1, through pathways involving both Class 1 and Class 3 PI3Ks. We provide evidence that IGF1 enhances endosomal PtdIns(3)P levels via a pathway involving the UV-RAG complex of hVPS34 Class 3 PI3K. Our data point towards IGF1-induced activation of Class 1 PI3K stimulating SGK3 through enhanced production of PtdIns(3)P resulting from the dephosphorylation of PtdIns(3,4,5)P₃ Our findings are also consistent with activation of Class 1 PI3K promoting mTORC2 phosphorylation of SGK3 and with oncogenic Ras-activating SGK3 solely through the Class 1 PI3K pathway. Our results highlight the versatility of upstream pathways that activate SGK3 and help explain how SGK3 substitutes for Akt following inhibition of Class 1 PI3K/Akt pathways. They also illustrate robustness of SGK3 activity that can remain active and counteract physiological conditions or stresses where either Class 1 or Class 3 PI3K pathways are inhibited.

Alphavirus-induced hyperactivation of PI3K/AKT directs pro-viral metabolic changes

Virus reprogramming of cellular metabolism is recognised as a critical determinant for viral growth. While most viruses appear to activate central energy metabolism, different viruses have been shown to rely on alternative mechanisms of metabolic activation. Whether related viruses exploit conserved mechanisms and induce similar metabolic changes is currently unclear. In this work we investigate how two alphaviruses, Semliki Forest virus and Ross River virus, reprogram host metabolism and define the molecular mechanisms responsible. We demonstrate that in both cases the presence of a YXXM motif in the viral protein nsP3 is necessary for binding to the PI3K regulatory subunit p85 and for activating AKT. This leads to an increase in glucose metabolism towards the synthesis of fatty acids, although additional mechanisms of metabolic activation appear to be involved in Ross River virus infection. Importantly, a Ross River virus mutant that fails to activate AKT has an attenuated phenotype in vivo, suggesting that viral activation of PI3K/AKT contributes to virulence and disease.

Truncated protein tyrosine phosphatase receptor type O suppresses AKT signaling through IQ motif containing GTPase activating protein 1 and confers sensitivity to bortezomib in multiple myeloma

Proteasome inhibitors are an important part of our chemotherapeutic armamentarium against multiple myeloma, but the vast majority of patients eventually develop drug-resistant disease through incompletely understood mechanisms. Comparison of gene expression profiles (GEPs) of bortezomib-resistant (BR) myeloma cell lines with their drug-naïve counterparts revealed decreased expression of truncated Protein tyrosine phosphatase receptor-type O (PTPROt) in BR cells. Over-expression of wild-type PTPROt in drug-naïve and BR cells reduced myeloma cell proliferation, induced apoptosis, and sensitized cells to bortezomib and to alkylating agents. PTPROt expression reduced AKT phosphorylation and activity, and sensitized to pharmacologic AKT pathway inhibitors, but this was not the case for a substrate-trapping catalytic domain-inactivating mutant. Co-immunoprecipitation and mass spectrometry studies identified IQ motif containing GTPase activating protein 1 (IQGAP1) as a PTPROt binding partner, and PTPROt reduced tyrosine phosphorylation of IQGAP1, providing a link to AKT activity. Analysis of clinically annotated GEP databases identified high PTPROt expression as being related to an increased likelihood of achieving complete remission with bortezomib therapy, while low expression was linked to a greater likelihood of disease progression. Finally, high PTPROt expression associated with prolonged median overall survival in patients receiving bortezomib-based therapy in the front-line or relapsed and/or refractory settings. Taken together, these data identify PTPROt suppression as a novel mechanism of myeloma resistance to bortezomib in myeloma cell lines, and also support the possibility that PTPROt expression could be used as a biomarker to predict outcomes with bortezomib, and by which to select patients for therapy with AKT inhibitors.

Network dynamics-based cancer panel stratification for systemic prediction of anticancer drug response

Cancer is a complex disease involving multiple genomic alterations that disrupt the dynamic response of signaling networks. The heterogeneous nature of cancer, which results in highly variable drug response, is a major obstacle to developing effective cancer therapy. Previous studies of cancer therapeutic response mostly focus on static analysis of genome-wide alterations, thus they are unable to unravel the dynamic, network-specific origin of variation. Here we present a network dynamics-based approach to integrate cancer genomics with dynamics of biological network for drug response prediction and design of drug combination. We select the p53 network as an example and analyze its cancer-specific state transition dynamics under distinct anticancer drug treatments by attractor landscape analysis. Our results not only enable stratification of cancer into distinct drug response groups, but also reveal network-specific drug targets that maximize p53 network-mediated cell death, providing a basis to design combinatorial therapeutic strategies for distinct cancer genomic subtypes.

Genomic alterations underlie the variability of drug responses between cancers, but our mechanistic understanding is limited. Here the authors use the p53 network to study how rewiring of signalling networks by genomic alterations impact their dynamic response to pharmacological perturbation.

Delineating the distinct role of AKT in mediating cell survival and proliferation induced by CD154 and IL-4/IL-21 in chronic lymphocytic leukemia

The functional significance of AKT in chronic lymphocytic leukemia (CLL) remains unclear. Given the importance of non-malignant T cells in regulating clonal expansion in CLL, we investigated the role of AKT in T cell-mediated cytoprotection and proliferation using an established co-culture system in which primary CLL cells were incubated on a monolayer of transfected mouse fibroblasts expressing human CD40L (CD154). Stimulation of CLL cells via CD40 induced activation of AKT, which was closely associated with downregulation of its negative regulator PTEN, and protected CLL cells from killing by bendamustine. This cytoprotective effect of CD40 stimulation was prevented by a selective inhibitor of AKT. Stimulation of CLL cells with CD154 + IL-4 or IL-21 induced proliferation detected as reduced fluorescence of cells pre-stained with CFSE. AKT inhibition produced a significant, consistent reduction in proliferation induced by CD154 + IL-4 and a reduction in proliferation induced by CD154 + IL-21 in most but not all cases. In contrast, AKT inhibition had no effect on the proliferation of normal B cells induced by CD154 + IL-4 or IL-21. These findings indicate that AKT contributes in a significant way to T-cell mediated survival and proliferation signalling in CLL and support the clinical evaluation of AKT inhibitors in this disease.

R-Ras-Akt axis induces endothelial lumenogenesis and regulates the patency of regenerating vasculature

The formation of endothelial lumen is fundamental to angiogenesis and essential to the oxygenation of hypoxic tissues. The molecular mechanism underlying this important process remains obscure. Here, we show that Akt activation by a Ras homolog, R-Ras, stabilizes the microtubule cytoskeleton in endothelial cells leading to endothelial lumenogenesis. The activation of Akt by the potent angiogenic factor VEGF-A does not strongly stabilize microtubules or sufficiently promote lumen formation, hence demonstrating a distinct role for the R-Ras-Akt axis. We show in mice that this pathway is important for the lumenization of new capillaries and microvessels developing in ischemic muscles to allow sufficient tissue reperfusion after ischemic injury. Our work identifies a role for Akt in lumenogenesis and the significance of the R-Ras-Akt signaling for the patency of regenerating blood vessels.

Formation of the vascular lumen initiates the blood flow and it is crucial for tissue homeostasis. Here, Li et. al show that the R-Ras-Akt signaling axis is crucial for reparative angiogenesis in mice because it stabilizes the microtubule cytoskeleton in endothelial cells to promote endothelial lumen formation.

In-vitro and in-vivo combined effect of ARQ 092, an AKT inhibitor, with ARQ 087, a FGFR inhibitor

The PI3K/AKT pathway plays an important role in the initiation and progression of cancer, and the drug development efforts targeting this pathway with therapeutic interventions have been advanced by academic and industrial groups. However, the clinical outcome is moderate. Combination of inhibition of PI3K/AKT and other targeted agents became a feasible approach. In this study we assessed the combined effect of ARQ 092, a pan-AKT inhibitor, and ARQ 087, a pan-FGFR inhibitor, in vitro and in vivo. In a panel of 45 cancer cell lines, on 24% (11 out of 45) the compounds showed synergistic effect, on 62% (28 out of 45) additive, and on 13% (6 out of 45) antagonistic. The highest percentage of synergism was found on endometrial and ovarian cancer cell lines. Mutational analysis revealed that PIK3CA/PIK3R1 mutations and aberrant activation of FGFR2 predicted synergism, whereas Ras mutations showed a reverse correlation. Pathway analysis revealed that a combination of ARQ 092 and ARQ 087 enhanced the inhibition of both the AKT and FGFR pathways in cell lines in which synergistic effects were found (AN3CA and IGROV-1). Cell cycle arrest and apoptotic response occurred only in AN3CA cell, and was not seen in IGROV-1 cells. Furthermore, enhanced antitumor activity was observed in mouse models with endometrial cancer cell line and patient-derived tumors when ARQ 092 and ARQ 087 were combined. These results from in-vitro and in-vivo studies provide a strong rationale in treating endometrial and other cancers with the activated PI3K/AKT and FGFR pathways.