Akt/PKB activation in gastric carcinomas correlates with clinicopathologic variables and prognosis

p70S6K/Akt dual inhibitor DIACC3010 is efficacious in preclinical models of gastric cancer alone and in combination with trastuzumab

The PI3K-Akt-mTOR (PAM) pathway is implicated in tumor progression in many tumor types, including metastatic gastric cancer (GC). The initial promise of PAM inhibitors has been unrealized in the clinic, presumably due, in part, to the up-regulation of Akt signaling that occurs when the pathway is inhibited. Here we present that DIACC3010 (formerly M2698), an inhibitor of two nodes in the PAM pathway, p70S6K and Akt 1/3, blocks the pathway in in vitro and in vivo preclinical models of GC while providing a mechanism that inhibits signaling from subsequent Akt up-regulation. Utilizing GC cell lines and xenograft models, we identified potential markers of DIACC3010-sensitivity in Her2-negative tumors, i.e., PIK3CA mutations, low basal pERK, and a group of differentially expressed genes (DEGs). The combination of DIACC3010 and trastuzumab was evaluated in Her2-positive cell lines and models. Potential biomarkers for the synergistic efficacy of the combination of DIACC3010 + trastuzumab also included DEGs as well as a lack of up-regulation of pERK. Of 27 GC patient-derived xenograft (PDX) models tested in BALB/c nu/nu mice, 59% were sensitive to DIACC3010 + trastuzumab. Of the 21 HER2-negative PDX models, DIACC3010 significantly inhibited the growth of 38%. Altogether, these results provide a path forward to validate the potential biomarkers of DIACC3010 sensitivity in GC and support clinical evaluation of DIACC3010 monotherapy and combination with trastuzumab in patients with HER2- negative and positive advanced GCs, respectively.

Dickkopf-related protein 1/cytoskeleton-associated protein 4 signaling activation by Helicobacter pylori-induced activator protein-1 promotes gastric tumorigenesis via the PI3K/AKT/mTOR pathway

BACKGROUND

Gastric cancer (GC) is a common malignant tumor with high incidence and mortality rates globally, especially in East Asian countries. Helicobacter pylori (H. pylori) infection is a significant and independent risk factor for GC. However, its underlying mechanism of action is not fully understood. Dickkopf-related protein (DKK) 1 is a Wnt signaling antagonist, and cytoskeleton-associated protein (CKAP) 4 is a newly identified DKK1 receptor. Recent studies found that the binding of DKK1 to CAKP4 mediated the procancer signaling of DKK1 inde-pendent of Wnt signaling. We hypothesize that H. pylori-induced activation of DKK1/CKAP4 signaling contributes to the initiation and progression of GC.

AIM

To investigate the interaction of H. pylori infection, DKK1 and CAKP4 in GC, as well as the underlying molecular mechanisms.

METHODS

RNA sequencing was used to identify differentially expressed genes (DEGs) between H. pylori-infected and uninfected primary GC cells. Gain- and loss-of-function experiments were performed to verify the H. pylori-induced upregulation of activator protein-1 (AP-1) in GC cells. A dual-luciferase reporter assay and co-immunoprecipitation were used to determine the binding of AP-1 to the DKK1 promoter and DKK1 to CKAP4. Western blotting and immunohistochemistry detected the expression of DKK1, CKAP4, and phos-phatidylinositol 3-kinase (PI3K) pathway-related proteins in GC cells and tissues. Functional experiments and tumorigenicity in nude mice detected malignant behavior of GC cells in vitro and in vivo.

RESULTS

We identified 32 DEGs between primary GC cells with and without H. pylori infection, including JUN, fos-like antigen-1 (FOSL1), and DKK1, and confirmed that the three proteins and CKAP4 were highly expressed in H. pylori-infected GC cells, H. pylori-infected gerbil gastric tissues, and human GC tissues. JUN and FOSL1 form AP-1 to transcriptionally activate DKK1 expression by binding to the DKK1 promoter. Activated DKK1 bound to CKAP4, but not the most common Wnt coreceptor low-density lipoprotein receptor-related protein 5/6, to promote GC cell growth, colony formation, migration, invasion, and xenograft tumor growth in nude mice. All these effects were driven by activation of the PI3K/AKT/mammalian target of rapamycin (mTOR) pathway. Targeting the PI3K signaling pathway by LY294002 inhibited DKK1-mediated CKAP4/PI3K signaling activity and the malignant behavior of GC cells.

CONCLUSION

H. pylori induces JUN and FOSL1 expression to form AP-1, which transcriptionally activates DKK1. Binding of DKK1 to KAKP4 contributes to gastric tumorigenesis via the PI3K/AKT/mTOR pathway.

miR-4742-5p promotes invasiveness of gastric cancer via targeting Rab43: An in vitro study

miRNA (miR)-4742-5p is a recently identified microRNA regarding progression and metastasis in gastric cancer (GC). However, the biological function of this novel miRNA is largely unknown. We identified that the miR-4742-5p expression level was variably increased in GC cell lines. Suppression of miR-4742-5p using miR-inhibitor reduced the proliferation, migration, and invasion of GC cells with high miR-4742-5p expression, whereas overexpression of miR-4742-5p-mimic enhanced the aforementioned properties in GC cells with low miR-4742-5p expression. miR-4742-5p expression induced the decreases of Zo-1 and E-cadherin expression as well as the increases of vimentin and N-cadherin expression, leading to epithelial-mesenchymal transition (EMT) of cancer cells. RNA sequencing results indicated Ras-related GTP-binding protein 43 (Rab43) as a potential target gene. We identified that the expression of Rab43 is associated with activation of AKT and nuclear factor-kappa B (NF-κB) which are key oncogenic pathways in cancer cells. Our results demonstrate a new component in GC progression, promising a potential therapeutic strategy.

Molecular target: pan-AKT in gastric cancer

The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signalling pathway is involved in multiple cellular processes, including cell survival, proliferation, differentiation, metabolism and cytoskeletal reorganisation. The downstream effectors of this PI3K pathway are also essential for maintaining physiologic homeostasis, commonly dysregulated in most solid tumours. AKT is the key regulator in PI3K/AKT/mTOR signalling, interacting with multiple intracellular molecules. AKT activation subsequently leads to a number of potential downstream effects, and its aberrant activation results in the pathogenesis of cancer. Accordingly, as an attractive therapeutic target for cancer treatment, several AKT inhibitors are currently under development and in multiple stages of clinical trials for various types of malignancy, including gastric cancer (GC). Therefore, the authors review the significance of AKT and recent studies on AKT inhibitors in GC, focusing on the scientific background with the potential to improve treatment outcomes.

Molecular Profiling Associated with Calcium/Calmodulin-Dependent Protein Kinase Kinase 2 (CAMKK2)-Mediated Carcinogenesis in Gastric Cancer

Gastric cancer is the fifth most common cancer and the third leading cause of cancer-related death worldwide. We showed previously that calcium/calmodulin-dependent protein kinase kinase 2 (CAMKK2), a serine-threonine kinase, is highly expressed in gastric cancer and leads to progression. In the present study, we identified the molecular networks involved in CAMKK2-mediated progression of gastric adenocarcinoma. Treatment of gastric cancer cell lines with a CAMKK2 inhibitor, STO-609, resulted in decreased cell migration, invasion, and colony-forming ability and a G1/S-phase arrest. In addition, tandem mass tag (TMT)-based quantitative proteomic analysis resulted in the identification of 7609 proteins, of which 219 proteins were found to be overexpressed and 718 downregulated (1.5-fold). Our data identified several key downregulated proteins involved in cell division and cell proliferation, which included DNA replication licensing factors, replication factor C, origin recognition complex, replication protein A and GINS, and mesenchymal markers, upon CAMKK2 inhibition. Immunoblotting and immunofluorescence results showed concordance with our mass spectroscopy data. Taken together, our study supports CAMKK2 as a novel therapeutic target in gastric cancer.

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

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

Prognostic value of the PIK3CA, AKT, and PTEN mutations in oral squamous cell carcinoma: literature review

Over 260,000 (2013) new oral squamous cell carcinoma (OSCC) cases are reported annually worldwide. Despite development in OSCC management, the outcome is still unsatisfactory. Identification of new molecular markers may be of use in prevention, prognosis, and choice of an appropriate therapy. The intracellular molecular signalling pathway of phosphatidyl-inositol-3-kinase is involved in the process of cell growth, differentiation, migration, and survival. The main components of this pathway: PIK3CA (phosphatidylinositol-4,5-bisphosphate-3-kinase catalytic subunit α), PTEN (phosphatase and tensin homologue deleted on chromosome 10), and AKT (serine-threonine kinase) are potential objects of research when introducing new therapeutic agents. The aim of this paper is to evaluate the PIK3CA, PTEN, and AKT gene mutations as prognostic factors in OSCC and to describe their role in aggressive disease progression. This is crucial for oral cancer biology understanding and for indicating which direction new clinical treatments should take.

Exploring Dysregulated Signaling Pathways in Cancer

Cancer cell biology takes advantage of identifying diverse cellular signaling pathways that are disrupted in cancer. Signaling pathways are an important means of communication from the exterior of cell to intracellular mediators, as well as intracellular interactions that govern diverse cellular processes. Oncogenic mutations or abnormal expression of signaling components disrupt the regulatory networks that govern cell function, thus enabling tumor cells to undergo dysregulated mitogenesis, to resist apoptosis, and to promote invasion to neighboring tissues. Unraveling of dysregulated signaling pathways may advance the understanding of tumor pathophysiology and lead to the improvement of targeted tumor therapy. In this review article, different signaling pathways and how their dysregulation contributes to the development of tumors have been discussed.

AMP-kinase inhibitor dorsomorphin reduces the proliferation and migration behavior of colorectal cancer cells by targeting the AKT/mTOR pathway

Colorectal cancer (CRC) is among the leading causes of cancer-related mortality, despite extensive efforts in the identification of new treatment options. Hence, there is a need for the development of novel agents with therapeutic potential in treatment of CRC. Dorsomorphin has demonstrated antiproliferative activity against different malignancies. Here we have investigated the pharmaceutical potential of dorsomorphin in two-dimensional and three-dimensional cell-culture models of CRC. The antiproliferative, antimigratory, apoptotic activity and effect of this agent on cell cycle was evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, wound healing assay, and flow cytometry, respectively, while the expression of genes involved in Wnt/Pi3K pathways was assessed at mRNA and/or proteins by reverse transcription polymerase chain reaction (RT-PCR) or western blot. Dorsomorphin inhibited CRC cell growth by modulating the cyclinD1, surviving and p-Akt. This agent was able to reduce the migratory behaviors of CRC cells, compared to control cells, through perturbation of E-cadherin. Also our data showed that dorsomorphin enhanced the percentage of the cells in sub-G1 and induced apoptosis in both late/early stages, as detected by annexin V. Also the regulatory effect of dorsomorphin on oxidant/antioxidant balance was assessed by cellular reactive oxygen species (ROS) generation. In particular, these data showed that dorsomorphin markedly increased the ROS production in CRC cells. Our finding demonstrated that dorsomorphin antagonizes cell growth and migration, through perturbation of Akt/mTOR/Wnt pathways in CRC, supporting further studies on the therapeutic potential of this novel anticancer agent in treatment of CRC.

Akt1 and Jak1 siRNA based silencing effects on the proliferation and apoptosis in head and neck squamous cell carcinoma

Based on Akt1 and Jak1 key roles in apoptosis and proliferation of many cancers, the aim of this study was to find a new gene therapy strategy by silencing of these main anti-apoptotic genes for HNSCC treatment. Cancerous HN5 and normal HUVEC cell lines were treated with Akt1 and Jak1 siRNAs alone or with each other combined with/without cisplatin. The MTS, flow cytometry, 4',6-diamidino-2-phenylindole staining, real-time PCR and ELISA methods were utilized in this study. The highest percentage of apoptosis was observed in the treatment of Jak1 siRNA/cisplatin group in cancerous HN5 cells (96.5%) where this treatment showed 12.84% apoptosis in normal HUVEC cell line. Cell viability reduced significantly to 64.57% after treatment with Akt1 siRNA in HN5 treated group. Knocking down Akt1 and Jak1 genes using siRNAs could increase levels of apoptosis and reduce proliferation rate in HNSCC indicating the powerful effects of these genes siRNAs with or without chemotherapeutic agents in HNSCC treatment. In conclusion, the combination of siRNA-mediated gene-silencing strategy can be considered as a valuable and safe approach for sensitizing cancer cells to chemotherapeutic agents thus proposed further studies regarding this issue to approve some siRNA based therapeutics for using in clinic.

Immunohistochemical assessment of growth factor signaling molecules: MAPK, Akt, and STAT3 pathways in oral epithelial precursor lesions and squamous cell carcinoma

Several growth factors and their receptors, such as epidermal growth factor receptor, have been studied as prognostic biomarkers for many epithelial malignancies. The signal transduction cascade of those receptors includes RAS/RAF/ERK, PI3K/Akt/mTOR, and STAT3 pathways. The aim of this study was to investigate the expression levels of several key proteins of those pathways in patients with oral squamous cell carcinoma (OSCC) and oral epithelial precursor lesions (OEPLs), and to correlate the expressions of these proteins with clinicopathologic features and prognosis. Fifteen leukoplakia (LP), 15 low-grade epithelial dysplasia, 15 high-grade epithelial dysplasia (HD), and 132 OSCC specimens were immunohistochemically examined for KRAS, HRAS, NRAS, BRAF, pERK1/2, pAkt, pmTOR, and pSTAT3 expression. Immunoreactivity for these molecules predominantly occurred in regions OEPL basal to prickle layers and in most OSCC cells. KRAS and NRAS expression was significantly lower in OSCC than in OEPLs, while pAkt and pmTOR showed higher expression in OSCC than in OEPLs. pERK1/2 expression was significantly higher in HD than in LP. In OSCC, KRAS and NRAS immunoreactivity was significantly higher in advanced age and male gender. In addition, higher immunoreactivity was shown in pERK1/2 in female gender and advanced TNM stage, pAkt in advanced T classification and cases without postoperative metastasis, pmTOR in advanced mode of invasion, and pSTAT3 in invasion depth. Correlations between these markers and clinicopathological variables were also noted. MAPK, Akt, and STAT3 pathways might play diverse roles in oral carcinogenesis.

mTOR Signaling in Cancer and mTOR Inhibitors in Solid Tumor Targeting Therapy

The mammalian or mechanistic target of rapamycin (mTOR) pathway plays a crucial role in regulation of cell survival, metabolism, growth and protein synthesis in response to upstream signals in both normal physiological and pathological conditions, especially in cancer. Aberrant mTOR signaling resulting from genetic alterations from different levels of the signal cascade is commonly observed in various types of cancers. Upon hyperactivation, mTOR signaling promotes cell proliferation and metabolism that contribute to tumor initiation and progression. In addition, mTOR also negatively regulates autophagy via different ways. We discuss mTOR signaling and its key upstream and downstream factors, the specific genetic changes in the mTOR pathway and the inhibitors of mTOR applied as therapeutic strategies in eight solid tumors. Although monotherapy and combination therapy with mTOR inhibitors have been extensively applied in preclinical and clinical trials in various cancer types, innovative therapies with better efficacy and less drug resistance are still in great need, and new biomarkers and deep sequencing technologies will facilitate these mTOR targeting drugs benefit the cancer patients in personalized therapy.

Zeylenone Induces Mitochondrial Apoptosis and Inhibits Migration and Invasion in Gastric Cancer

The mortality of gastric cancer (GC) is increasing due to its high rates of recurrence and metastasis. Zeylenone (Zey), a type of naturally occurring cyclohexene oxide, was demonstrated to be effective in cancer patients. The aim of this study is to explore the anti-cancer effect of Zey against gastric cancer both in vitro and in vivo, as well as the underlying mechanisms. We found that Zey inhibited gastric tumor growth, as demonstrated by in vitro gastric cancer cell lines and in a human gastric cancer xenograft mouse model. Furthermore, Zey induced substantial apoptosis through a mitochondrial apoptotic pathway, involving mitochondrial transmembrane potential loss, caspase-3 activation, anti-apoptotic protein downregulation, and pro-apoptotic protein upregulation. Notably, we revealed for the first time that Zey suppressed invasion and migration by wound healing and transwell chamber assays. Through Western blotting, we further explored the potential mechanism of Zey’s anti-cancer activity. We found that Zey downregulated the expression of matrix metalloproteinase 2/9 (MMP 2/9) and inhibited the phosphorylation of AKT and ERK. In short, Zey, which induced mitochondrial apoptosis and inhibited proliferation, migration, and invasion, may be developed as a novel drug for the treatment of gastric cancer.

Mangiferin prevents the growth of gastric carcinoma by blocking the PI3K-Akt signalling pathway

The aim of the present study was to investigate the effects of mangiferin on gastric carcinoma cells and to determine the possible mechanisms underlying such effects. The MTT assay was performed to evaluate the antiproliferative effect of mangiferin. Following treatment, apoptosis rates of SGC-7901 were established by flow cytometry and laser confocal microscopy, and western blot analysis was used to detect the expression of apoptosis-related proteins. The MTT assay showed that mangiferin inhibited the proliferation of SGC-7901 and BCG-823 cells in a dose-dependent and time-dependent manner. After SGC-7901 cells were exposed to mangiferin for 24, 48 and 72 h, the half-maximal inhibitory concentration values were 16.00, 8.63 and 4.79 µmol/l, respectively. SGC-7901 cell apoptosis induced by mangiferin was observed by Annexin V/PI doubling staining and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive staining. We found a significant decrease in Bcl-2, Bcl-xL and Mcl-1 expression and a significant increase in Bax, Bad and cleaved caspase-3 and caspase-9 expression in SGC-7901 cells by mangiferin treatment. Moreover, mangiferin significantly decreased the levels of p-PI3K, p-Akt and p-mTOR, but had no effects on those of PI3K, Akt and mTOR in epidermal growth factor-treated SGC-7901 cells. Interestingly, the proapoptotic effect of mangiferin on SGC-7901 cells was partially blocked by the Akt activator SC79, whereas LY294002 significantly increased mangiferin-induced apoptosis and growth inhibition. Taken together, our findings indicate that mangiferin effectively inhibits cell growth and induces apoptosis of gastric cancer cells through inhibiting the PI3K/Akt pathways with relative safety, and may be used as a novel chemotherapeutic agent against gastric cancer.

The Potential Role of Akt Phosphorylation in Human Cancers

Akt/protein kinase B (PKB) is a serine/threonine kinase which is implicated in mediating a variety of biological responses including cell growth, proliferation and survival. Akt is activated by phosphorylation on two critical residues, namely threonine 308 (Thr308) and serine 473 (Ser473). Several studies have found Akt2 to be amplified or overexpressed at the mRNA level in various tumor cell lines and in a number of human malignancies such as colon, pancreatic and breast cancers. Nevertheless, activation of Akt isoforms by phosphorylation appears to be more clinically significant than Akt2 amplification or overexpression. Many studies in the past 4–5 years have revealed a prognostic and/or predictive role of Akt phosphorylation in breast, prostate and non-small cell lung cancer. Several publications suggest a role of phosphorylated Akt also in endometrial, pancreatic, gastric, tongue and renal cancer. However, different types of assays were used in these studies. Before assessment of P-Akt can be incorporated into routine clinical practice, all aspects of the assay methodology will have to be standardized.

Positive prognostic value of HER2-HER3 co-expression and p-mTOR in gastric cancer patients

Background

The HER2-HER3 heterodimer significantly decreases survival in breast cancer patients. However, the prognostic value of HER2-HER3 overexpression remains unknown in gastric cancer (GC).

Methods

The expression levels of HER2, HER3, Akt, p-Akt, mTOR and p-mTOR were examined in specimens from 120 GC patients by immunohistochemistry and quantitative reverse transcription-PCR. The associations of HER proteins, PI3K/Akt/mTOR pathway-related proteins, clinicopathological features of GC, and overall survival (OS) were assessed. To comprehensively evaluate the prognostic values of pathway-related proteins, meta-analyses were conducted with STATA 11.0.

Results

HER2 overexpression was significantly associated with HER3 levels (P = 0.02). HER3 was highly expressed in gastric cancer tissues. High HER2 and HER3 levels were associated with elevated p-Akt and p-mTOR amounts (P < 0.05). Furthermore, HER2-HER3 co-expression was associated with high p-Akt and p-mTOR (P < 0.05) levels. Meanwhile, p-mTOR overexpression was tightly associated with differentiation, depth of invasion, lymph node metastasis, TNM stage and OS (P < 0.05). By meta-analyses, Akt, p-Akt, and mTOR levels were unrelated to clinicopathological characters. HER3 overexpression was associated with depth of invasion (OR = 2.39, 95%CI 1.62–3.54, P < 0.001) and lymph node metastasis (OR = 2.35, 95%CI 1.34–4.11, P = 0.003). Further, p-mTOR overexpression was associated with patient age, tumor location, depth of invasion (OR = 1.63, 95%CI 1.08–2.45, P = 0.02) and TNM stage (OR = 1.73, 95%CI 1.29–2.32, P < 0.001). In addition, HER2-HER3 overexpression corresponded to gradually shortened 5-year OS (P < 0.05), and significant relationships were shown among HER3, p-mTOR overexpression, and 1-, 3-, 5-year OS (P < 0.05).

Conclusions

HER2-HER3 co-expression may potentially enhance mTOR phosphorylation. HER2-HER3 co-expression and p-mTOR are both related to the prognosis of GC patients.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3851-y) contains supplementary material, which is available to authorized users.

Prognostic implications of phosphatidylinositol 3-kinase/AKT signaling pathway activation in gastric carcinomas

INTRODUCTION

Activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway plays a critical role in carcinogenesis and resistance to anticancer drugs. In this study, gastric carcinomas (GC) were investigated and statistical analyses were performed concerning the correlation between the clinicopathological features and activation of the PI3K/AKT pathway.

MATERIAL AND METHODS

Immunohistochemistry for p-AKT, p-mTOR and PTEN was performed in 239 GC and 200 non-neoplastic gastric tissues. The clinicopathological parameters were recorded from the medical charts. Statistical significance was defined by a p-value < 0.05.

RESULTS

High p-AKT expression was observed in 10% of the normal gastric tissue and in 90% of GC, and it was significantly associated with tumor size (p < 0.001), T3/T4 tumors (p < 0.001), and presence of metastases (p = 0.02). Similarly, p-mTOR positivity was found in GC cells, but not in the normal gastric mucosa, and was correlated with perineural invasion (p = 0.02) and T3/T4 tumors (p = 0.03). On the other hand, PTEN expression was weak and focal in the tumor cells, while in the normal gastric tissue this staining was strong and diffuse. Importantly, the expression of p-mTOR and PTEN was associated with overall survival.

CONCLUSIONS

The results of the present study, characterized by the loss of PTEN expression and higher expression of p-AKT and p-mTOR in the majority of tumor cells, apparently are implicated in the carcinogenesis and progression of GC. The identification of p-mTOR and PTEN expression as prognostic factors corroborates the identification and use of potential target drugs that could be more efficient for the treatment of these patients.

Targeting the AKT pathway: Repositioning HIV protease inhibitors as radiosensitizers

Cellular resistance in tumour cells to different therapeutic approaches has been a limiting factor in the curative treatment of cancer. Resistance to therapeutic radiation is a common phenomenon which significantly reduces treatment options and impacts survival. One of the mechanisms of acquiring resistance to ionizing radiation is the overexpression or activation of various oncogenes like the EGFR (epidermal growth factor receptor), RAS (rat sarcoma) oncogene or loss of PTEN (phosphatase and tensin homologue) which in turn activates the phosphatidyl inositol 3-kinase/protein kinase B (PI3-K)/AKT pathway responsible for radiation resistance in various tumours. Blocking the pathway enhances the radiation response both in vitro and in vivo. Due to the differential activation of this pathway (constitutively activated in tumour cells and not in the normal host cells), it is an excellent candidate target for molecular targeted therapy to enhance radiation sensitivity. In this regard, HIV protease inhibitors (HPIs) known to interfere with PI3-K/AKT signaling in tumour cells, have been shown to sensitize various tumour cells to radiation both in vitro and in vivo. As a result, HPIs are now being investigated as possible radiosensitizers along with various chemotherapeutic drugs. This review describes the mechanisms by which PI3-K/AKT pathway causes radioresistance and the role of HIV protease inhibitors especially nelfinavir as a potential candidate drug to target the AKT pathway for overcoming radioresistance and its use in various clinical trials for different malignancies.

p-Akt as a potential poor prognostic factor for gastric cancer: a systematic review and meta-analysis

To understand the relationship between p-Akt expression and the prognosis of patients with gastric cancer, we searched six databases, Pubmed, EMBASE, Cochrane Library, CNKI, Wanfang and CBM for relevant articles in order to conduct this metaanalysis. The pooled hazard ratios and corresponding 95%CI of overall survival were calculated to evaluate the prognostic value of p-Akt expression in patients with gastric cancer. With 2261 patients combined from 13 available studies, the pooled HR showed a poor prognosis in patients with gastric cancer in the univariate analysis (HR=1.88, 95%CI:1.45-2.43, P<0.00001), and the group "univariate analysis+estimate" (HR=1.41, 95%CI: 1.01-1.97, P=0.04), but not in multivariate analysis (HR=0.66, 95%CI: 0.29-1.52, P=0.33) and estimate (HR=1.13, 95%CI: 0.65-1.95, P=0.67). In conclusion, our results indicated that p-Akt was likely to be an indicator of poor prognosis in patients with gastric cancer.

Curcuminoid EF24 enhances the anti-tumour activity of Akt inhibitor MK-2206 through ROS-mediated endoplasmic reticulum stress and mitochondrial dysfunction in gastric cancer

BACKGROUND AND PURPOSE

Gastric cancer is one of the leading causes of morbidity and mortality worldwide. Akt is an anti-apoptotic kinase that plays a dynamic role in cell survival and is implicated in the pathogenesis of gastric cancer. MK-2206, the first allosteric inhibitor of Akt, is in clinical trials for a number of cancers. Although preclinical studies showed promise, clinical trials reported it had no effect when given alone at tolerated doses. The aim of our study was to delineate the effects of MK-2206 on gastric cancer cells and explore the ability of combination treatments to enhance the anti-tumour activity of MK-2206.

EXPERIMENTAL APPROACH

SGC-7901, BGC-823 cells and immunodeficient mice were chosen as a model to study the treatment effects. Changes in cell viability, apoptosis and ROS, endoplasmic reticulum stress and mitochondrial dysfunction in the cells were analysed by MTT assays, ROS imaging and FACSCalibur, electron microscopy, JC-1 staining and western blotting.

KEY RESULTS

MK-2206 induced apoptotic cell death through the generation of ROS. We utilized ROS production to target gastric cancer cells by combining MK-2206 and an ROS inducer EF24. Our in vitro and in vivo xenograft studies showed that combined treatment with MK-2206 and EF24 synergistically induced apoptosis in gastric cancer cells and caused cell cycle arrest. These activities were mediated through ROS generation and the induction of endoplasmic reticulum stress and mitochondrial dysfunction.

CONCLUSION AND IMPLICATIONS

Targeting ROS generation by using a combination of an Akt inhibitor and EF24 could have potential as a therapy for gastric cancer.

Analysis of PIK3CA mutations and PI3K pathway proteins in advanced gastric cancer

BACKGROUND

Although surgery and chemotherapy have extended advanced gastric cancer patient survival, some patients still experience relapse and metastasis. We postulated that PI3K pathway proteins could be prognostic biomarkers for the advanced gastric cancer patients.

METHODS

A retrospective cohort of 160 advanced gastric cancer patients receiving potentially curative surgery with/without chemotherapy was investigated for PIK3CA mutation and PI3K pathway protein level in the context of overall survival and relapse-free survival.

RESULTS

Thirteen patients (13 of 111, 11.7%) had PIK3CA mutations in codon 545, whereas one patient (1 of 94, 1.1%) had a mutation in PIK3CA codon 1047. PI3K pathway protein immunohistochemistry demonstrated that phosphorylated AKT positive [p-AKT (+)] patients in the surgery-only group had a good prognosis in terms of overall survival and relapse-free survival. No significant association between PIK3CA mutations and PI3K pathway protein level was seen.

CONCLUSIONS

This study revealed that (1) PIK3CA hotspot mutations occurred with low frequency in gastric cancer; (2) PIK3CA hotspot mutations were not directly associated with PI3K pathway activation; and (3) p-AKT (+) may be a biomarker for better outcomes for gastric cancer patients undergoing gastrectomy regardless of the PIK3CA mutation status.

Targeting the Phosphatidylinositol-3-kinase Pathway in Gastric Cancer: Can Omics Improve Outcomes?

Phosphatidylinositol-3-kinase (PI3K) pathway signaling is an established oncogenic signal transduction pathway implicated in multiple malignancies. Therapeutic targeting of PI3K pathway components has improved outcomes in chronic lymphocytic leukemia, kidney cancer, breast cancer, and neuroendocrine tumors. Gastric cancers harbor some of the highest rates of oncogenic alterations in PI3K but attempts to translate this genomic observation have met with limited clinical success and novel approaches are needed. In the following review we discuss PI3K signaling, previous preclinical and clinical investigations in gastric cancer, and discuss future strategies aimed at overcoming resistance and improving efficacy. Identification and refinement of molecular tumor subtypes, development of predictive biomarkers along, and rational drug combination strategies are key to capitalizing on the therapeutic potential of PI3K pathway directed therapies in gastric cancers.

The roles of HOXB7 in promoting migration, invasion, and anti-apoptosis in gastric cancer

BACKGROUND AND AIM

The aim of this study was to compare HOXB7 expression level between gastric cancer and non-cancerous gastric tissues. Additionally, the functional effects of HOXB7, including its pro-migration or invasion and anti-apoptosis roles, were evaluated in gastric cancer cells.

METHODS

Both gene and protein expression levels of HOXB7 were examined in gastric cancer cell lines, and HOXB7 expression was compared between primary or metastatic gastric cancer tissues and chronic gastritis or intestinal metaplasia tissues. Functional studies included a wound healing assay, a Matrigel invasion assay, and an Annexin-V assay were performed, and Akt/PTEN activity was measured by western blotting.

RESULTS

Both gene and protein expression levels of HOXB7 could be clearly detected in various gastric cancer cell lines except MKN-28 cell. HOXB7 expression was significantly higher in primary or metastatic gastric cancer tissues than in chronic gastritis or intestinal metaplasia tissues. HOXB7 knockdown led to inhibition of cell invasion and migration, had an apoptotic effect, downregulated phosphor-Akt, and upregulated PTEN in AGS and SNU-638 cells. Reinforced expression of HOXB7 caused the opposite effects in MKN-28 and MKN-45 cells.

CONCLUSION

Our study suggests that HOXB7 has an oncogenic role in gastric cancer, which might be related to the modulation of Akt/PTEN activity to induce cell migration/invasion and anti-apoptotic effects.

Molecular mechanisms of chemoresistance in gastric cancer

Gastric cancer is the fourth most common cancer and the second leading cause of cancer deaths worldwide. Chemotherapy is one of the major treatments for gastric cancer, but drug resistance limits the effectiveness of chemotherapy, which results in treatment failure. Resistance to chemotherapy can be present intrinsically before the administration of chemotherapy or it can develop during chemotherapy. The mechanisms of chemotherapy resistance in gastric cancer are complex and multifactorial. A variety of factors have been demonstrated to be involved in chemoresistance, including the reduced intracellular concentrations of drugs, alterations in drug targets, the dysregulation of cell survival and death signaling pathways, and interactions between cancer cells and the tumor microenvironment. This review focuses on the molecular mechanisms of chemoresistance in gastric cancer and on recent studies that have sought to overcome the underlying mechanisms of chemoresistance.

MK-2206 co-treatment with 5-fluorouracil or doxorubicin enhances chemosensitivity and apoptosis in gastric cancer by attenuation of Akt phosphorylation

The anticancer effect of MK-2206, an Akt inhibitor, has been explored in some types of cancers, but its effect on gastric cancer is unclear. In this study, we aimed to investigate its anticancer effect in gastric cancer cells. Cell viability and colony formation assays showed that MK-2206 effectively inhibited the proliferation of SGC-7901 and MKN45 cells. The 50% inhibitory concentration values after 24, 48, and 72 hours' treatment were 22.92, 13.68, and 8.55 μM in SGC-7901 cells and 19.21, 13.10, and 9.11 μM in MKN45 cells, respectively. Treatment with MK-2206 induced apoptosis in SGC-7901 cells as indicated by flow cytometry assay. The combination indexes of MK-2206 and doxorubicin were 0.59 in SGC-7901 cells and 0.57 in MKN45 cells, whereas for 5-fluorouracil (5-FU) the indexes were 0.17 in SGC-7901 cells and 0.73 in MKN45 cells, indicating that MK-2206 could work synergistically with doxorubicin or 5-FU to inhibit cell growth. Furthermore, a small dose (1 μM) of MK-2206 co-treatment with doxorubicin or 5-FU was sufficient for complete inhibition of chemotherapeutic alteration of phosphorylated Akt expression and significant enhancement of pro-apoptosis effect through the activation of caspase pathway. Therefore, MK-2206 effectively inhibits gastric cancer cell growth by attenuation of Akt phosphorylation and synergistically enhances the antitumor effect of doxorubicin and 5-FU via caspase-dependent apoptosis.

Bufalin reverses intrinsic and acquired drug resistance to cisplatin through the AKT signaling pathway in gastric cancer cells

Cisplatin is the most common chemotherapeutic agent for gastric cancer (GC), however it activates AKT, which contributes to intrinsic and acquired resistance. Bufalin, a traditional Chinese medicine, shows significant anticancer activity by inhibiting the AKT pathway. It was therefore hypothesized that bufalin could counteract cisplatin resistance in GC cells. SGC7901, MKN‑45 and BGC823 human GC cells were cultured under normoxic and hypoxic conditions. Effects of cisplatin and bufalin on GC cells were measured by a cell counting kit, apoptosis was analyzed by flow cytometry, and immunoblotting was used to detect proteins associated with the AKT signaling pathway. It was demonstrated that bufalin synergized with cisplatin to inhibit proliferation and promote apoptosis of GC cells by diminishing the activation of cisplatin-induced AKT under normoxic and hypoxic conditions. Bufalin also inhibits cisplatin-activated molecules downstream of AKT that affect proliferation and apoptosis, including glycogen synthase kinase, mammalian target of rapamycin, ribosomal protein S6 Kinase and eukaryotic translation initiation factor-4E-binding protein-1. To investigate acquired cisplatin resistance, a cisplatin‑resistant cell line SGC7901‑CR was used. It was demonstrated that bufalin reversed acquired cisplatin resistance and significantly induced apoptosis through the AKT pathway. These results imply that bufalin could extend the therapeutic effect of cisplatin on GC cells when administered in combination.

Suppression of SHIP2 contributes to tumorigenesis and proliferation of gastric cancer cells via activation of Akt

BACKGROUND

The Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) is implicated in diabetes, arthrosclerosis, and cancer. However, the role of SHIP2 in human gastric cancer remains unclear.

METHODS

The expression levels of SHIP2 in gastric cancer tissues, a panel of gastric cancer cell lines, and normal gastric epithelial cells were analyzed by immunohistochemistry (IHC), Western blot, and real-time quantitative RT-PCR (qRT-PCR). Gastric cancer cells with either overexpressed SHIP2 or co-overexpressed SHIP2 and Akt were analyzed to determine cell proliferation, colony formation, apoptosis, cell migration, and invasion assays. Normal gastric epithelial cells with knockdown SHIP2 or co-knockdown SHIP2 and Akt were subjected by anchorage-independent growth assays. The effect of SHIP2 on tumor growth in vivo was detected by xenograft tumorigenesis assays.

RESULTS

SHIP2 was commonly downregulated in gastric cancer compared with normal gastric mucosa, and overexpression of SHIP2 inhibited cell proliferation, induced apoptosis, suppressed cell motility and invasion in gastric cancer cells in vitro, and retarded the growth of xenograft gastric tumors in vivo, while knockdown of SHIP2 in normal gastric epithelial cells promoted anchorage-independent growth. Moreover, overexpression of SHIP2 inactivated Akt, and upregulated p21, p27, and the pro-apoptotic protein Bim. Restoring Akt activation in gastric cancer cells largely blocked the inhibition of PI3K/Akt signaling by SHIP2 and reversed the inhibitory effect of SHIP2 on tumorigenesis and proliferation.

CONCLUSIONS

This study demonstrates, for the first time, that SHIP2 is frequently downregulated in gastric cancer, and reduced SHIP2 expression promotes tumorigenesis and proliferation of gastric cancer via activation of the PI3K/Akt signaling.

A Functional Polymorphism (rs2494752) in the AKT1 Promoter Region and Gastric Adenocarcinoma Risk in an Eastern Chinese Population

AKT is an important signal transduction protein that plays a crucial role in cancer development. Therefore, we evaluated associations between single nucleotide polymorphisms (SNPs) in the AKT promoter region and gastric cancer (GCa) risk in a case-control study of 1,110 GCa patients and 1,114 matched cancer-free controls. We genotyped five SNPs (AKT1 rs2494750G >C, AKT1 rs2494752A >G, AKT1 rs10138227C >T, AKT2 rs7254617G>A and AKT2 rs2304186G >T) located in the 5' upstream regulatory, first intron or promoter regions. In the logistic regression analysis, a significantly elevated GCa risk was associated with the rs2494752 AG/GG variant genotypes (adjusted odds ratio [OR] = 1.20, 95% confidence interval [CI] = 1.02-1.42) under a dominant genetic model, and this risk was more evident in subgroups of ever drinkers. The luciferase reporter assay showed that the rs2494752 G allele significantly increased luciferase activity. Our results suggest that the potentially functional AKT1 rs2494752 SNP may affect GCa susceptibility, likely by modulating the AKT1 promoter transcriptional activity. Larger, independent studies are warranted to validate our findings.

Silencing A7-nAChR levels increases the sensitivity of gastric cancer cells to ixabepilone treatment

Gastric cancer is an important health issue worldwide. Currently, improving the therapeutic efficacy of chemotherapy drugs is an important goal of cancer research. Alpha-7 nicotine acetylcholine receptor (A7-nAChR) is the key molecule that mediates gastric cancer progression, metastasis, and therapy responses; however, the role of A7-nAChR in the therapeutic efficacy of ixabepilone remains unclear. A7-nAChR expression was silenced by small interfering RNA (siRNA) technology. The cytotoxicity of ixabepilone was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and ixabepilone-induced apoptosis was analyzed by flow cytometry and annexin V/propidium iodide (PI) apoptotic assay. The expression patterns of anti-apoptotic proteins (AKT, phospho-AKT, Mcl-1, and Bcl-2) and pro-apoptotic proteins (Bad and Bax) were determined by western blot. Our study found that A7-nAChR knockdown (A7-nAChR-KD) AGS cells were more sensitive to ixabepilone administration than scrambled control AGS cells. We found that A7-nAChR knockdown enhanced ixabepilone-induced cell death as evidenced by the increased number of annexin V-positive (apoptotic) cells. After scrambled control and A7-nAChR-KD cells were treated with ixabepilone, we found that pAKT and AKT levels were significantly reduced in both groups of cells. The levels of Bcl-2 and the anti-apoptotic Mcl-1 isoform increased dramatically after ixabepilone treatment in scrambled control cells but not in A7-nAChR-KD cells. Bad and Bax levels did not change between the treatment group and vehicle group in both A7-nAChR-KD and scrambled control cells, whereas cleaved PARP levels dramatically increased in ixabepilone-treated A7-nAChR-KD cells. Our results demonstrated that knockdown of A7-nAChR enhanced the sensitivity of gastric cancer cells to ixabepilone administration. Thus, the A7-nAChR expression level in patients with gastric cancer may be a good indicator of ixabepilone sensitivity.

The forkhead transcription factor FOXO1 mediates cisplatin resistance in gastric cancer cells by activating phosphoinositide 3-kinase/Akt pathway

BACKGROUND

Cisplatin (CDDP) is one of the most important chemotherapeutic agents in the treatment of advanced gastric cancer, but its efficacy is limited by CDDP resistance. Because the transcription factor FOXO1 is related to chemoresistance in various cancer cells, we investigated the function of FOXO1 in CDDP resistance in human gastric cancer cells.

METHODS

Human gastric cancer cell lines MKN45 and SNU-601 were used. FOXO1 activation was modulated by transfection of FOXO1 AAA mutant gene or FOXO1 shRNA. The effects of FOXO1 on cell growth and CDDP cytotoxicity were assessed by crystal violet assay. Protein expressions of FOXO1, p110α, pAkt, and Akt were analyzed by Western blotting, and FOXO1 mRNA expression was evaluated by semiquantitative reverse transcription-polymerase chain reaction. FOXO1 activity was determined by luciferase reporter assay, and cell apoptosis was assessed by DAPI staining and Western blotting for PARP cleavage.

RESULTS

Cisplatin treatment induced FOXO1 expression and activation in both gastric cancer cell lines. FOXO1 overexpression increased the CDDP resistance without changes in cell growth, whereas FOXO1 silencing enhanced CDDP cytotoxicity along with apoptotic characteristics. Both constitutive and CDDP-induced FOXO1 activations were accompanied by an increase in p110α and pAkt expression. Furthermore, Akt inhibition by LY294002 treatment restored the CDDP cytotoxicity that was suppressed by FOXO1 overexpression.

CONCLUSION

FOXO1 inhibits CDDP-induced apoptosis in gastric cancer cells via activating PI3K/Akt pathway. Thus, FOXO1 may be an useful pharmacological indicator to predict CDDP efficacy in gastric cancer treatment.

The prognostic value of phosphorylated Akt in breast cancer: a systematic review

The prognostic value of phosphorylated Akt (pAkt) overexpression in breast cancer has been investigated by many studies with inconsistent results. This systematic review was conducted to evaluate the association of pAkt overexpression with breast cancer prognosis in terms of overall survival and disease-free survival. Three electronic databases (PubMed, EMBASE and Chinese Biomedical Literature Database) were comprehensively searched. Hazard ratios (HRs) with 95% confidence intervals (CIs) from different studies were combined using the random-effects model. In total, 33 studies with 9,836 patients were included for final analysis. The summary HR for overall survival and disease-free survival was 1.52 (95% CI: 1.29-1.78) and 1.28 (95% CI: 1.13-1.45), respectively, indicating higher risk of death and disease recurrence associated with pAkt overexpression. The results were robust in sensitivity analyses by omitting one study each time and by using the fixed-effects model instead. Subgroup and meta-regression analyses did not show that the prognostic effect of pAkt overexpression would change materially with such factors as population, status of hormone receptors, hormonal or trastuzumab treatment given, analyzing method (univariate versus multivariate) and methodological quality of the original studies. In conclusion, the available evidence suggests that pAkt overexpression is an adverse prognostic factor for breast cancer.

Attenuation of enoyl coenzyme A hydratase short chain 1 expression in gastric cancer cells inhibits cell proliferation and migration in vitro

Enoyl coenzyme A hydratase short chain 1 (ECHS1) is an important part of the mitochondrial fatty acid β-oxidation pathway. Altered ECHS1 expression has been implicated in cancer cell proliferation. This study assessed ECHS1 expression in human gastric cancer cell lines and investigated the effects of ECHS1 knockdown on gastric cancer cell proliferation and migration. The human gastric cancer cell lines SGC-7901, BGC-823 and MKN-28, and the immortalized human gastric epithelial mucosa GES-1 cell line were analyzed for ECHS1 protein levels using western blot. The effectiveness of ECHS1-RNA interference was also determined using western blot. Proliferation and migration of the siECHS1 cells were respectively measured with the CCK-8 and transwell assays. Phosphorylation of PKB and GSK3β was assessed using western blot. ECHS1 protein levels were significantly higher in poorly differentiated cells than in well-differentiated cells and immortalized gastric epithelial mucosa cells. Stable expression of ECHS1 shRNA was associated with an over 41% reduction in the ECHS1 protein levels of siECHS1 cells. Constitutive knockdown of the ECHS1 gene in siECHS1 cells was associated with significantly inhibited cell proliferation and migration. We also observed decreased levels of PKB and GSK3β phosphorylation in siECHS1 cells. ECHS1 expression is increased in human gastric cancer cells. Increased ECHS1 expression activates PKB and GSK3β by inducing the phosphorylation of the two kinases. ECHS1 may play important roles in gastric cancer cell proliferation and migration through PKB- and GSK3β-related signaling pathways.

The PI3K/AKT/mTOR pathway in the pathophysiology and treatment of pituitary adenomas

Pituitary adenomas are common intracranial neoplasms. Patients with these tumors exhibit a wide range of clinically challenging problems, stemming either from results of sellar mass effect in pituitary macroadenoma or the diverse effects of aberrant hormone production by adenoma cells. While some patients are cured/controlled by surgical resection and/or medical therapy, a proportion of patients exhibit tumors that are refractory to current modalities. New therapeutic approaches are needed for these patients. Activation of the AKT/phophotidylinositide-3-kinase pathway, including mTOR activation, is common in human neoplasia, and a number of therapeutic approaches are being employed to neutralize activation of this pathway in human cancer. This review examines the role of this pathway in pituitary tumors with respect to tumor biology and its potential role as a therapeutic target.

Akt and p53R2, partners that dictate the progression and invasiveness of cancer

The serine/threonine kinase or the so-called "Akt" is a key regulatory molecule of signaling pathway that regulates various cellular processes. Many intracellular proteins are involved in the activation or inhibition of Akt signaling and the hyperactivation of Akt signaling pathway is found to be frequently involved in various types of human cancers. Furthermore, while p53R2, a p53-inducible peptide involved in the synthesis of dNTPs normally works toward suppression of cancer through elimination of reactive oxygen species (ROS), inhibition of MAPK/ERK pathway and providing dNTPs for DNA repair, the overexpression of p53R2 is reported to be associated with cancer progression and resistance to therapy. In this review article, we will discuss the situation in which cancer cells with hyperactive PI3K/Akt signaling can recruit p53R2 in favor of cancer progression and resistance to therapy. In the hyperactive state of PI3K/Akt signaling (which happens in the absence of deactivation or excess of activation), p53R2 can be used by cancer cells to promote proliferation. Therefore, the hyperactivity of PI3K/Akt pathway and elevated levels of p53R2 can give rise to highly invasive cancers.

The Role of PI3K/Akt/mTOR Signaling in Gastric Carcinoma

The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is one of the key signaling pathways induced by various receptor-tyrosine kinases. Accumulating evidence shows that this pathway is an important promoter of cell growth, metabolism, survival, metastasis, and resistance to chemotherapy. Genetic alterations in the PI3K/Akt/mTOR pathway in gastric carcinoma have often been demonstrated. Many kinds of molecular targeting therapies are currently undergoing clinical testing in patients with solid tumors. However, with the exception of the ErbB2-targeting antibody, targeting agents, including PI3K/Akt/mTOR inhibitors, have not been approved for treatment of patients with gastric carcinoma. This review summarizes the current knowledge on PI3K/Akt/mTOR signaling in the pathogenesis of gastric carcinoma and the possible therapeutic targets for gastric carcinoma. Improved knowledge of the PI3K/Akt/mTOR pathway in gastric carcinoma will be useful in understanding the mechanisms of tumor development and for identifying ideal targets of anticancer therapy for gastric carcinoma.

MK-2206, an Akt inhibitor, enhances carboplatinum/paclitaxel efficacy in gastric cancer cell lines

BACKGROUND

Several molecularly-targeted agents are being evaluated in gastric cancer cell lines. In this study we evaluated the synergistic potential of MK-2206, an oral potent allosteric Akt inhibitor, in combination with chemotherapeutic agents in human gastric cancer cell lines.

MATERIALS AND METHODS

We evaluated effects of MK-2206 on cell growth and cell signaling using a panel of gastric cancer cell lines AGS, SNU-1 and SNU 16. The analysis of drug combinations was conducted by using CellTiter-Blue™ Cell Viability Assay which yielded the combination index (CI). MK-2206 and representative chemotherapy agent were further evaluated regarding their effects on Akt inhibition and downstream targets using western blots probed with the appropriate antibodies. We assessed the combination of MK-2206 and chemotherapy in three different treatment sequences.

RESULTS

We demonstrated in vitro synergistic efficacy of MK-2206 when combined with carboplatinum and paclitaxel in the three cell lines examined. Efficacy was dose dependent. We assessed the combination of MK-2206 and carboplatinum/paclitaxel in three different treatment sequences; 24 h of exposure to combination chemotherapy followed by a 48 h exposure to MK-2206 resulted in the highest synergistic antiproliferative effect in all cell lines. On the other hand, the reverse sequence (MK-2206 followed by chemotherapy) and the concurrent treatment schedule were slightly synergistic or additive as well. The effects of MK-2206 on p-Akt and other downstream targets was reported.

CONCLUSIONS

Our findings suggest that Akt inhibition augments the efficacy of existing gastric cancer therapeutics (carboplatinum and paclitaxel); thus, MK-2206 is a promising agent to treat gastric cancer patients who receive these cytotoxic agents. The magnitude of synergy depended on the treatment sequence; a schedule of MK-2206 dosed before or concurrently with chemotherapy was not as effective as being dosed after chemotherapy. Further experiments addressing MK-2206's mechanism of action in combination with chemotherapy are needed.

Hepatic vitamin A preloading reduces colorectal cancer metastatic multiplicity in a mouse xenograft model

Previous research in our laboratory showed that retinol inhibited all-trans retinoic acid (ATRA)-resistant human colon cancer cell invasion via a retinoic acid receptor-independent mechanism in vitro. The objective of the current study was to determine if dietary vitamin A supplementation inhibited metastasis of ATRA-resistant colon cancer cells in a nude mouse xenograft model. Female nude mice (BALB/cAnNCr-nu/nu, n = 14 per group) consumed a control diet (2,400 IU retinyl palmitate/kg diet) or a vitamin A supplemented diet (200,000 IU retinyl palmitate/kg diet) for 1 mo prior to tumor cell injection to preload the liver with vitamin A. HCT-116, ATRA-resistant, human colon cancer cells were intrasplenically injected. Mice continued to consume their respective diets for 5 wk following surgery. Consumption of supplemental vitamin A decreased hepatic metastatic multiplicity to 17% of control. Hepatic and splenic retinol and retinyl ester concentrations were significantly higher in the mice supplemented with vitamin A when compared to mice consuming the control diet. Supplemental vitamin A did not decrease body weight, feed intake, or cause toxicity. Thus, supplemental dietary vitamin A may decrease the overall number of hepatic metastasis resulting from colon cancer.

Regulation of SHP2 by PTEN/AKT/GSK-3β signaling facilitates IFN-γ resistance in hyperproliferating gastric cancer

Oncogenic activation accompanied by escape from immune surveillance, such as IFN-γ resistance, is critical for cancer cell growth and survival. In this study, we investigated the crosstalk signaling between IFN-γ resistance and signaling of hyperproliferation in gastric cancer cells. IFN-γ inhibited the cell growth of MKN45 cells but not hyperproliferating AGS cells. AGS cells did not respond to IFN-γ because of a decrease in STAT1 but not due to dysfunctional IFN-γ receptors. Signaling of PI3K/AKT, as well as MEK/ERK, was required for the hyperproliferation; notably, PI3K/AKT alone mediated the IFN-γ resistance. Aberrant Src homology-2 domain-containing phosphatase (SHP) 2 determined IFN-γ resistance but unexpectedly had no effects on hyperproliferation or ERK activation. In the IFN-γ resistant cells, inactivation of glycogen synthase kinase (GSK)-3β by PI3K/AKT was important for SHP2 activation but not for hyperproliferation. An imbalance of AKT/GSK-3β/SHP2 caused by a reduction of PTEN was important for the crosstalk between IFN-γ resistance and hyperproliferation. PI3K is constitutively expressed in AGS cells and immunohistochemical staining showed a correlation between hyperproliferation and expression of SHP2 and STAT1 in gastric tumors. These results demonstrate the effects of PTEN/AKT/GSK-3β/SHP2 signaling on IFN-γ resistance in hyperproliferating gastric cancer cells.

Constitutive activation of signal transducers and activators of transcription 3 correlates with better prognosis, cell proliferation and hypoxia-inducible factor-1α in human gastric cancer

OBJECTIVE

We aimed to investigate the biological significance of signal transducers and activators of transcription 3 (STAT3) in gastric carcinoma.

METHODS

Immunohistochemistry was performed on tissue array slides containing 285 gastric carcinoma specimens. The relationship between the nuclear expression of phospho-Tyr705-STAT3 (pSTAT3), an active form of STAT3, and prognosis, clinicopathological factors, proliferation, cell cycle regulators, apoptosis regulators, or angiogenesis-related proteins was evaluated.

RESULTS

In nonneoplastic gastric mucosa, pSTAT3 was observed primarily in the nuclei of cells in the proliferative zone and intestinal metaplasia. In gastric carcinomas, nuclear STAT3 activation was observed in 36% of cases and was positively correlated with the Ki-67 labeling index and earlier tumor stage, whereas it was inversely correlated with lymphatic metastasis and distant metastasis (p< 0.05). Moreover, survival analyses showed that pSTAT3 expression was an independent prognostic factor of good survival. In addition, the expression of nuclear pSTAT3 positively correlated with that of cyclin D1, p21, p27, hypoxia-inducible factor-1α, or vascular endothelial growth factor (p< 0.05).

CONCLUSIONS

STAT3 activation is an early event in gastric tumorigenesis and significantly correlates with better prognosis, proliferation and angiogenesis. Thus, STAT3 activation may be a valuable prognostic variable and therapeutic target in gastric carcinoma.

Clinical significance of expression of PTEN, Akt and pAkt in hepatocellular carcinoma

AIM: To explore the expression of phosphatase and tensin homology deleted on chromosome ten (PTEN), Akt and pAkt proteins in hepatocellular carcinoma (HCC) and to elucidate their clinical significance.

METHODS: Immunohistochemical analysis was performed to detect the expression of PTEN, Akt and pAkt proteins in 78 specimens of hepatocellular carcinoma and 21 specimens of normal liver tissues. The relationship of their expression with clinicopathological and prognostic parameters was analyzed.

RESULTS: The rate of PTEN overexpression was significantly lower in HCC than in normal liver tissue (42.3% vs 90.5%, P < 0.05), while the rates of Akt and pAkt overexpression were significantly higher in HCC than in normal liver tissue (66.7% vs 33.3%; 43.6% vs 9.5%, both P < 0.05). PTEN expression was correlated with tumor size, cancer embolus of the portal vein, tumor invasion, lymph node metastasis and TNM stage. Akt and pAkt expression was correlated with tumor size, invasion, lymph node metastasis and TNM stage. PTEN expression was negatively correlated with Akt (r = -0.385, P = 0.000) and pAkt (r =- 0.334, P = 0.003) expression in HCC. Patients with low PTEN expression or high Akt and pAkt expression had a significantly worse survival time than those with high PTEN expression or low Akt and pAkt expression (P = 0.000). A multivariate analysis based on the COX regression model demonstrated that TNM stage and pAkt expression were independent prognostic factors for HCC.

CONCLUSION: The expression of PTEN, Akt and pAkt proteins is closely related to the malignant biological behavior of HCC. pAkt can be used as a key factor for predicting prognosis in HCC patients.

Akt signalling in health and disease

Akt (also known as protein kinase B or PKB) comprises three closely related isoforms Akt1, Akt2 and Akt3 (or PKBα/β/γ respectively). We have a very good understanding of the mechanisms by which Akt isoforms are activated by growth factors and other extracellular stimuli as well as by oncogenic mutations in key upstream regulatory proteins including Ras, PI3-kinase subunits and PTEN. There are also an ever increasing number of Akt substrates being identified that play a role in the regulation of the diverse array of biological effects of activated Akt; this includes the regulation of cell proliferation, survival and metabolism. Dysregulation of Akt leads to diseases of major unmet medical need such as cancer, diabetes, cardiovascular and neurological diseases. As a result there has been substantial investment in the development of small molecular Akt inhibitors that act competitively with ATP or phospholipid binding, or allosterically. In this review we will briefly discuss our current understanding of how Akt isoforms are regulated, the substrate proteins they phosphorylate and how this integrates with the role of Akt in disease. We will furthermore discuss the types of Akt inhibitors that have been developed and are in clinical trials for human cancer, as well as speculate on potential on-target toxicities, such as disturbances of heart and vascular function, metabolism, memory and mood, which should be monitored very carefully during clinical trial.

Prognostic value of co-expression of STAT3, mTOR and EGFR in gastric cancer

Signal transducer and activator of transcription 3 (STAT3), the mammalian target of rapamycin (mTOR) and epidermal growth factor receptor (EGFR), proteins that mediate intracellular signaling related to cell growth, proliferation and differentiation, have received considerable interest as possible targets for cancer treatment. We examined whether the expression of STAT3, mTOR and EGFR correlates with clinicopathological features and patient outcome in gastric cancer. Tumor samples were obtained from 126 patients with gastric adenocarcinomas who underwent a radical gastrectomy between 1999 and 2002. The expression of phosphorylated STAT3 (p-STAT3), p-mTOR and EGFR was analyzed by immunohistochemical staining. The relations of these to clinicopathological factors and outcomes were assessed. The expression of p-STAT3 p-mTOR and EGFR positively correlated with the following variables related to tumor progression: the depth of tumor invasion (T1 vs. T2-4; p<0.001, p=0.036 and p<0.001, respectively), lymph node involvement (p=0.008, p=0.027 and p=0.007) and tumor stage (I vs. II-IV; p<0.001, p=0.041 and p<0.001). The expression of p-STAT3 and EGFR was significantly related to distant metastasis and recurrence (p=0.001 and p=0.039), as well as significantly poorer disease-specific survival (DSS; p=0.0018 and p=0.026). The expression of p-STAT3 was a marginally non-significant prognostic factor for DSS (hazard ratio=2.0, 95% CI 0.91-4.5, p=0.082). Increasing expression of p-STAT3, p-mTOR and EGFR was associated with progressively worse DSS. Interactions among p-STAT3, p-mTOR and EGFR may play an important role in tumor progression and outcomes in patients with gastric cancer.

New frontiers in the treatment of liposarcoma, a therapeutically resistant malignant cohort

The adipogenic origin-derived liposarcoma (LPS) family is the most common soft tissue sarcoma histological subtype. This group is composed of three categories as per the 2002 WHO guidelines: (1) well-differentiated and dedifferentiated liposarcoma (WDLPS/DDLPS); (2) myxoid and round cell liposarcoma (MLS and RCL); and (3) pleomorphic liposarcoma (PLS). While clustered together, these histological subtypes are widely diverse in their clinical, pathological, and molecular characteristics. In general, surgery still remains the mainstay of LPS therapy and the only approach offering the potential of cure. Effective therapeutic strategies for locally advanced and metastatic disease are currently lacking and are crucially needed. With the current gradually increasing knowledge of LPS genetic- and epigenetic-associated deregulations, the ultimate goal is to develop drugs that can specifically eliminate LPS cells while sparing normal tissues. This tumor-tailored target-orientated approach will hopefully result in a significant improvement in the outcome of patients suffering from these poor prognosis malignancies.

Phosphorylated AKT expression is associated with PIK3CA mutation, low stage, and favorable outcome in 717 colorectal cancers

BACKGROUND

AKT (AKT1, AKT2, and AKT3) was a downstream effector of phosphatidylinositide-3-kinase (PI3K) and played crucial roles in protein synthesis, cellular metabolism, survival, and proliferation. The PI3K/AKT pathway was commonly activated in human cancers and was recognized as a potential target for anticancer therapy. Nonetheless, clinical, molecular, or prognostic features of AKT-activated colon cancer remained uncertain.

METHODS

Using a database of 717 colon and rectal cancers in the Nurses' Health Study and the Health Professionals Follow-up Study, Ser473 phosphorylated AKT (p-AKT) expression was detected in 448 (62%) tumors by immunohistochemistry. Cox proportional hazards model was used to compute mortality hazards ratio (HR), adjusting for clinical and tumoral features, including PIK3CA, KRAS, BRAF, microsatellite instability (MSI), CpG island methylator phenotype (CIMP), LINE-1 methylation, TP53 (p53), and FASN (fatty acid synthase).

RESULTS

Tumor p-AKT expression was associated with PIK3CA mutation (odds ratio [OR], 1.77; 95% confidence interval [CI], 1.12-2.80; P = .015). p-AKT expression was significantly associated with longer colorectal cancer-specific survival in Kaplan-Meier analysis (log-rank P = .0005), univariate Cox regression (HR, 0.62; 95% CI, 0.47-0.82; P = .0006) and multivariate analysis (adjusted HR, 0.75; 95% CI, 0.56-0.99; P = .048) adjusting for clinical and molecular variables including PIK3CA, MSI, CIMP and LINE-1 hypomethylation. p-AKT expression was inversely associated with high stage (III-IV) (adjusted OR, 0.63; 95% CI, 0.45-0.88, P = .0071).

CONCLUSIONS

p-AKT expression in colorectal cancer is associated with low stage and good prognosis. p-AKT may serve as a tissue biomarker to identify patients with superior prognosis and a possible therapeutic target (analogous to estrogen receptor ESR1 in breast cancer).

In vitro and in vivo inhibition of neuroblastoma tumor cell growth by AKT inhibitor perifosine

BACKGROUND

Activated AKT is a marker of decreased event-free or overall survival in neuroblastoma (NB) patients. The aim of this study was to investigate the effect of perifosine, a nontoxic AKT inhibitor, as a single agent on NB cell growth in vitro and in vivo.

METHODS

Four human NB cell lines (AS, NGP, BE2, and KCNR) were treated with increasing concentrations of perifosine, and a quantitative analysis of cell death (apoptosis) was performed by using MTS and caspase-3/7 activity assays. Survival of mice carrying xenograft NB tumors that were treated with perifosine (n = 6-7 mice per group) was compared with that of untreated mice (n = 7 mice per group) using Kaplan-Meier analysis. Tumor volumes were calculated to determine the effect of perifosine on NB tumor growth. Phosphorylation of AKT and expression of cleaved caspase-3 were measured in proteins from the tumors. All statistical tests were two-sided.

RESULTS

Perifosine, at 30 muM concentration, decreased AKT phosphorylation and increased apoptosis in all four NB cell lines in vitro. Perifosine-treated mice bearing xenograft NB tumors had longer survival than untreated mice (untreated vs treated, median survival: AS, 13 days, 95% confidence interval [CI] = 11 to 16 days vs not reached, P = .003; NGP, 22 days, 95% CI = 20 to 26 days vs not reached, P = .013; BE2, 24 days, 95% CI = 21 to 27 days vs not reached, P < .001; and KCNR, 18 days, 95% CI = 18 to 21 days vs not reached, P < .001). Perifosine treatment induced regression in AS tumors, growth inhibition in BE2 tumors, and slower growth in NGP and KCNR tumors. Inhibition of AKT phosphorylation and induction of caspase-dependent apoptosis were noted in tumors of perifosine-treated mice in all four in vivo NB tumor models.

CONCLUSIONS

Perifosine inhibited the activation of AKT and was an effective cytotoxic agent in NB cells in vitro and in vivo. Our study supports the future clinical evaluation of perifosine for the treatment of NB tumors.

Rapamycin enhances chemotherapy-induced cytotoxicity by inhibiting the expressions of TS and ERK in gastric cancer cells

We have previously reported the synergistic cytotoxic effects of Docetaxel (TXT) and S-1 in gastric cancer in vitro and in vivo, and the combination regimen is now under phase III clinical trail. In this study, to elucidate whether the rapamycin, the inhibitor of the mTOR (mammalian target of rapamaycin), can enhance the potentiation of TXT and 5-fluorouracil (5-Fu) in gastric carcinoma cells. Rapamycin inhibited the growth of TMK-1, MKN-28, MKN-45 and MKN-74 cell lines by MTT assay, and it demonstrated the cytostatic effects as G1 arrest shown by flowcytometry. However, the cytotoxic effects of 5-Fu, TXT and cisplatin were enhanced by 2 to 4 times with the concomitant administration of rapamycin. To clarify the mechanism of the potentiation, the expression changes of the enzymes relating DNA metabolism and cell growth signal transduction pathways were examined by western blot analysis. Interestingly, the expression of thymidilate synthase was markedly decreased by the administration of rapamycin in TMK-1 cells in a time- and dose-dependent manner. Moreover, rapamycin decreased the phosphorylation of 4E-BP1, the phosphorylation of ERK1/2 and enhanced the phosphorylation of c-Jun NH2-terminal kinase, and the activation of caspase of apoptotic pathways in combination with TXT. These results strongly indicate that the mTOR inhibitor can enhance the potentiation of TXT and 5-Fu or S-1 and can serve as a new therapeutic tool for advanced and recurrent gastric cancer patients.

Higher pAkt expression predicts a significant worse prognosis in glioblastomas

phosphorylated-Akt (pAkt) plays an important role in tumorigenesis through promotion of cell survival by inhibiting apoptosis and mediating cell proliferation. Higher expression of pAkt has been reported to be associated with an unfavorable prognosis in several malignant tumors. In this study, the prognostic value of pAkt expression was investigated in glioblastomas by using immunohistochemical methods. Tissue sections obtained from 64 patients with glioblastoma were evaluated. The mean and median follow-up period was 16.2 +/- 12.4 and 12 months, respectively (range: from 1 to 62 months). pAkt expression levels were determined by immunohistochemical staining and evaluated for cell positivity. Positive staining was defined when more than 50% of the tumor cells were stained in each section. The correlation between expression of pAkt and overall survival rate was assessed. Glioblastomas showed either or both cytoplasmic and nuclear positive findings for pAkt. A total of 29.7% (19/64) of tissue specimens had greater than 50% positivity. The median survival periods of the patients with pAkt positive and negative tumor were 10 and 14 months, respectively. Two years overall survival rate of the pAkt positive and negative patients were 0% and 24.4%, respectively. Survival rate of the patients with pAkt positive tumor was significantly lower than that of the patients with pAkt negative tumors (p = 0.004). Multivariate analysis showed that extent of surgery was the strongest factor for survival (p = 0.01) and the pAkt expression was the secondly strongest factor (p = 0.06). These results suggest that the higher expression of pAkt the poorer prognosis in patients with glioblastoma.