Akt1/protein kinase B alpha is involved in gastric cancer progression and cell proliferation

Delivery of AKT1 phospho-forms to human cells reveals differential substrate selectivity

Protein kinase B (AKT1) is a serine/threonine kinase that regulates fundamental cellular processes, including cell survival, proliferation, and metabolism. AKT1 activity is controlled by two regulatory phosphorylation sites (Thr308, Ser473) that stimulate a downstream signaling cascade through phosphorylation of many target proteins. At either or both regulatory sites, hyperphosphorylation is associated with poor survival outcomes in many human cancers. Our previous biochemical and chemoproteomic studies showed that the phosphorylated forms of AKT1 have differential selectivity toward peptide substrates. Here, we investigated AKT1-dependent activity in human cells, using a cell-penetrating peptide (transactivator of transcription, TAT) to deliver inactive AKT1 or active phospho-variants to cells. We used enzyme engineering and genetic code expansion relying on a phosphoseryl-transfer RNA (tRNA) synthetase (SepRS) and tRNASep pair to produce TAT-tagged AKT1 with programmed phosphorylation at one or both key regulatory sites. We found that all TAT-tagged AKT1 variants were efficiently delivered into human embryonic kidney (HEK 293T) cells and that only the phosphorylated AKT1 (pAKT1) variants stimulated downstream signaling. All TAT-pAKT1 variants induced glycogen synthase kinase (GSK)-3α phosphorylation, as well as phosphorylation of ribosomal protein S6 at Ser240/244, demonstrating stimulation of downstream AKT1 signaling. Fascinatingly, only the AKT1 variants phosphorylated at S473 (TAT-pAKT1S473 or TAT-pAKT1T308,S473) were able to increase phospho-GSK-3β levels. Although each TAT-pAKT1 variant significantly stimulated cell proliferation, cells transduced with TAT-pAKT1T308 grew significantly faster than with the other pAKT1 variants. The data demonstrate differential activity of the AKT1 phospho-forms in modulating downstream signaling and proliferation in human cells.

Effects of catechin on the malignant biological behavior of gastric cancer cells through the PI3K/Akt signaling pathway

Catechin is a kind of flavonoids, mainly derived from the plant Camellia sinensis. It has a strong antioxidant effect, and it also has significant therapeutic effects on anti-cancer, anti-diabetes, and anti-infection. This study was intended to look at how catechin affected the malignant biological activity of gastric cancer cells. We used databases to predict the targets of catechin and the pathogenic targets of gastric cancer. Venn diagram was used to find the intersection genes, the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analyses were performed on intersection genes. Using the STRING database, the Protein-Protein Interaction (PPI) network was built. The top 8 genes were screened by Cytoscape 3.9.1, then their binding was verified by molecular docking. The proliferation ability, cell cycle, apoptosis and migration of gastric cancer cells were detected, as well as the protein expression levels of PI3K, p-AKT, and AKT and the mRNA expression levels of AKT1, VEGFA, EGFR, HRAS, and HSP90AA1 in gastric cancer cells. Our research revealed that different concentrations of catechin could effectively inhibit the proliferation and migration of gastric cancer cells, regulate the cell cycle, and promote the death of these cells, and it's possible that the PI3K/Akt pathway was crucial in mediating this impact. Moreover, adding the PI3K/Akt pathway agonist significantly reduced the promoting effect of catechin on the apoptosis of gastric cancer cells. This study suggested that catechin was a potential drug for the treatment of gastric cancer.

Integrating metabolomics, 16S rRNA sequencing, network pharmacology, and metorigin to explore the mechanism of Cinnamomi Cortex in treating chronic atrophic gastritis rats

BACKGROUND

Cinnamomi cortex called as Rougui (RG) in Chinese was a widely used food-medicine homology. RG has the potential to treat chronic atrophic gastritis (CAG), a disease with widespread impact in the Chinese population.

PURPOSE

This study aimed to explore its mechanism against CAG based on amalgamated strategies.

METHODS

Network pharmacology was used to predict the potential effective components and the core targets of RG against CAG based on the comprehensive chemical characterization using UHPLC-Q/TOF MS (ultra high performance liquid chromatogramphy-quadrupole/time-of-flight mass spectrometry). The CAG animals model were further used to validate its pharmacodynamics, of which gut microbiota of caecal contents were analyzed by integrating metabolomics, 16S rRNA sequencing, Metorigin metabolite traceability analysis and molecular docking to explore its action mechanism.

RESULTS

Network pharmacology firstly predicted the efficacy of RG was attributed to four effective components and seven targets. Metabolomics of caecal contents in CAG rats revealed primary bile acid biosynthesis was its targeted metabolic pathway associated with the metabolism of gut microbiota coupled with Metorigin traceability analysis. 16S rRNA sequencing showed that RG treated CAG by regulating the imbalance of gut microbiota. Molecular docking further confirmed that the effective components of RG could intervene with potential targets, metorigin analysis pathway, and key enzymes of gut microbiota metabolic pathways.

CONCLUSION

Our results proved that RG exerted favorable effect on CAG. The four active ingredients (quercetin, kaempferol, oleic acid, and (-)-epicatechin) of RG were the key to exert drug effect, which could targeted the core target of CAG, primary bile acid biosynthesis and intestinal flora metabolic pathways.

Advancements and Obstacles of PARP Inhibitors in Gastric Cancer

Gastric cancer (GC) is a common and aggressive cancer of the digestive system, exhibiting high aggressiveness and significant heterogeneity. Despite advancements in improving survival rates over the past few decades, GC continues to carry a worrisome prognosis and notable mortality. As a result, there is an urgent need for novel therapeutic approaches to address GC. Recent targeted sequencing studies have revealed frequent mutations in DNA damage repair (DDR) pathway genes in many GC patients. These mutations lead to an increased reliance on poly (adenosine diphosphate-ribose) polymerase (PARP) for DNA repair, making PARP inhibitors (PARPi) a promising treatment option for GC. This article presents a comprehensive overview of the rationale and development of PARPi, highlighting its progress and challenges in both preclinical and clinical research for treating GC.

Molecular insights into the behavior of the allosteric and ATP-competitive inhibitors in interaction with AKT1 protein: A molecular dynamics study

AKT1 is a family of serine/threonine kinases that play a key role in regulating cell growth, proliferation, metabolism, and survival. Two significant classes of AKT1 inhibitors (allosteric and ATP-competitive) are used in clinical development, and both of them could be effective in specific conditions. In this study, we investigated the effect of several different inhibitors on two conformations of the AKT1 by computational approach. We studied the effects of four inhibitors, including MK-2206, Miransertib, Herbacetin, and Shogaol, on the inactive conformation of AKT1 protein and the effects of four inhibitors, Capivasertib, AT7867, Quercetin, and Oridonin molecules on the active conformation of AKT1 protein. The results of simulations showed that each inhibitor creates a stable complex with AKT1 protein, although AKT1/Shogaol and AKT1/AT7867 complexes showed less stability than other complexes. Based on RMSF calculations, the fluctuation of residues in the mentioned complexes is higher than in other complexes. As compared to other complexes in either of its two conformations, MK-2206 has a stronger binding free energy affinity in the inactive conformation, -203.446 kJ/mol. MM-PBSA calculations showed that the van der Waals interactions contribute more than the electrostatic interactions to the binding energy of inhibitors to AKT1 protein.

Systems Medicine Design based on Systems Biology Approaches and Deep Neural Network for Gastric Cancer

Gastric cancer (GC) is the third leading cause of cancer death in the world. It is associated with the stimulation of microenvironment, aberrant epigenetic modification, and chronic inflammation. However, few researches discuss the GC molecular progression mechanisms from the perspective of the system level. In this study, we proposed a systems medicine design procedure to identify essential biomarkers and find corresponding drugs for GC. At first, we did big database mining to construct candidate protein-protein interaction network (PPIN) and candidate gene regulation network (GRN). Second, by leveraging the next-generation sequencing (NGS) data, we performed system modeling and applied system identification and model selection to obtain real genome-wide genetic and epigenetic networks (GWGENs). To make the real GWGENs easy to analyze, the principal network projection method was used to extract the core signaling pathways denoted by KEGG pathways. Subsequently, based on the identified biomarkers, we trained a deep neural network of drug-target interaction (DeepDTI) with supervised learning and filtered our candidate drugs considering drug regulation ability and drug sensitivity. With the proposed systematic strategy, we not only shed the light on the progression of GC but also suggested potential multiple-molecule drugs efficiently.

Integrating Network Pharmacology and Experimental Verification to Explore the Pharmacological Mechanisms of Aloin Against Gastric Cancer

Purpose

This study was designed to evaluate the pharmacological mechanisms of Aloin against gastric cancer (GC) via network pharmacology analysis combined with experimental verification.

Methods

Using network pharmacology methods, the potential targets of Aloin and targets related to GC were screened from public databases. The protein–protein interaction (PPI) network, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed to predict the core targets and pathways of Aloin against GC. The expressions of major targets predicted by network pharmacology in normal stomach tissues and GC tissues and their relationships with overall survival of GC were searched in GEPIA, HPA and DriverDBv3 database. The results of network pharmacology analysis were verified by in vitro experiments.

Results

A total of 129 potential targets were retrieved by searching the intersection of Aloin and GC targets. PPI network analysis indicated that 10 targets, including AKT1 and CASP3, were hub genes. GO enrichment analysis involved 93 biological processes, 19 cellular components, and 37 molecular functions. KEGG enrichment analysis indicated that the anti-cancer effect of Aloin was mediated through multiple pathways, such as PI3K-AKT, FoxO and Ras signaling pathway. Among them, the PI3K-AKT signaling pathway, which contained the largest number of enriched genes, may play a greater role in the treatment of GC. The validation of key targets in GEPIA, HPA and DriverDBv3 database showed that the verification results for most core genes were consistent with this study. Then, the results of in vitro experiment indicated that Aloin could inhibit proliferation of NCI-N87 cells and induce cell apoptosis. The results also showed that Aloin could decrease the mRNA and protein expressions of PI3K and AKT, suggesting that Aloin can treat GC by inducing cell apoptosis and regulating the PI3K-AKT signaling pathway.

Conclusion

This study identified the potential targets of Aloin against GC using network pharmacology and in vitro verification, which provided a new understanding of the pharmacological mechanisms of Aloin in treatment of GC.

CRIP1 cooperates with BRCA2 to drive the nuclear enrichment of RAD51 and to facilitate homologous repair upon DNA damage induced by chemotherapy

Homologous recombination (HR) repair is an important determinant of chemosensitivity. However, the mechanisms underlying HR regulation remain largely unknown. Cysteine-rich intestinal protein 1 (CRIP1) is a member of the LIM/double-zinc finger protein family and is overexpressed and associated with prognosis in several tumor types. However, to date, the functional role of CRIP1 in cancer biology is poorly understood. Here we found that CRIP1 downregulation causes HR repair deficiency with concomitant increase in cell sensitivity to cisplatin, epirubicin, and the poly ADP-ribose polymerase (PARP) inhibitor olaparib in gastric cancer cells. Mechanistically, upon DNA damage, CRIP1 is deubiquitinated and upregulated by activated AKT signaling. CRIP1, in turn, promotes nuclear enrichment of RAD51, which is a prerequisite step for HR commencement, by stabilizing BRCA2 to counteract FBXO5-targeted RAD51 degradation and by binding to the core domain of RAD51 (RAD51184-257) in coordination with BRCA2, to facilitate nuclear export signal masking interactions between BRCA2 and RAD51. Moreover, through mass spectrometry screening, we found that KPNA4 is at least one of the carriers controlling the nucleo-cytoplasmic distribution of the CRIP1-BRCA2-RAD51 complex in response to chemotherapy. Consistent with these findings, RAD51 inhibitors block the CRIP1-mediated HR process, thereby restoring chemotherapy sensitivity of gastric cancer cells with high CRIP1 expression. Analysis of patient specimens revealed an abnormally high level of CRIP1 expression in GC tissues compared to that in the adjacent normal mucosa and a significant negative association between CRIP1 expression and survival time in patient cohorts with different types of solid tumors undergoing genotoxic treatments. In conclusion, our study suggests an essential function of CRIP1 in promoting HR repair and facilitating gastric cancer cell adaptation to genotoxic therapy.

LncRNA NEAT1 promotes gastric cancer progression via miR-1294/AKT1 axis

Long non-coding RNAs (lncRNAs) were reported to promote the development of gastric cancer (GC). Nuclear-enriched abundant transcript 1 (NEAT1) played a great role in diverse cancers, but the mechanism of NEAT1 in GC remains indistinct. NEAT1 and AKT1 were distinctly up-regulated and miR-1294 was down-regulated in GC tissues and cells. Cell proliferation and metastasis were refrained but apoptosis was promoted in GC cells after knockdown of NEAT1. NEAT1 negatively regulated miR-1294 expression, and the miR-1294 inhibitor reverted the si-NEAT1-induced effect on GC cells. NEAT1 modulated AKT1 expression through miR-1294, and the si-NEAT1-induced effect was relieved by AKT1. NEAT1 affected phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway via regulating miR-1294 and AKT1. NEAT1 could modulate cell proliferation, apoptosis, and metastasis in GC cells by regulating the PI3K/AKT/mTOR signaling pathway via the miR-1294/AKT1 axis, showing the great potential for NEAT1 as a valid biomarker in the progression and treatment of GC.

The unconventional role of Akt1 in the advanced cancers and in diabetes-promoted carcinogenesis

Decades of research have elucidated the critical role of Akt isoforms in cancer as pro-tumorigenic and metastatic regulators through their specific effects on the cancer cells, tumor endothelial cells and the stromal cells. The pro-cancerous role of Akt isoforms through enhanced cell proliferation and suppression of apoptosis in cancer cells and the cells in the tumor microenvironment is considered a dogma. Intriguingly, studies also indicate that the Akt pathway is essential to protect the endothelial-barrier and prevent aberrant vascular permeability, which is also integral to tumor perfusion and metastasis. To complicate this further, a flurry of recent reports strongly indicates the metastasis suppressive role of Akt, Akt1 in particular in various cancer types. These reports emanated from different laboratories have elegantly demonstrated the paradoxical effect of Akt1 on cancer cell epithelial-to-mesenchymal transition, invasion, tumor endothelial-barrier disruption, and cancer metastasis. Here, we emphasize on the specific role of Akt1 in mediating tumor cell-vasculature reciprocity during the advanced stages of cancers and discuss how Akt1 differentially regulates cancer metastasis through mechanisms distinct from its pro-tumorigenic effects. Since Akt is integral for insulin signaling, endothelial function, and metabolic regulation, we also attempt to shed some light on the specific effects of diabetes in modulating Akt pathway in the promotion of tumor growth and metastasis.

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.

The Inositide Signaling Pathway As a Target for Treating Gastric Cancer and Colorectal Cancer

Gastric cancer and colorectal cancer are the leading cause of cancer mortality and have a dismal prognosis. The introduction of biological agents to treat these cancers has resulted in improved outcomes, and combination chemotherapy with targeted agents and conventional chemotherapeutic agents is regarded as standard therapy. Additional newly clarified mechanisms of oncogenesis and resistance to targeted agents require the development of new biologic agents. Aberrant activation of the inositide signaling pathway by a loss of function PTEN mutation or gain of function mutation/amplification of PIK3CA is an oncogenic mechanism in gastric cancer and colorectal cancer. Clinical trials with biologic agents that target the inositide signaling pathway are being performed to further improve treatment outcomes of patients with advanced gastric cancer and metastatic colorectal cancer (CRC). In this review we summarize the inositide signaling pathway, the targeted agents that inhibit abnormal activation of this signaling pathway and the clinical trials currently being performed in patients with advanced or metastatic gastric cancer and metastatic CRC using these targeted agents.

β-hydroxyisovaleryl-shikonin induces human cervical cancer cell apoptosis via PI3K/AKT/mTOR signaling

The present study aimed to investigate the inhibitory ability of β-hydroxyisovaleryl-shikonin (β-HIVS) on the proliferation of human cervical cancer HeLa cells and to identify the mechanism of this effect. The HeLa cells were treated with β-HIVS and the inhibition of cell growth was detected by an MTT assay. Flow cytometry was performed to analyze the apoptosis rate and cell cycle distribution of HeLa cells. Reverse transcription-polymerase chain reaction and western blot analysis were used to examine the expression of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway proteins. The results revealed that β-HIVS inhibited HeLa cell proliferation in a dose- and time-dependent manner. With the administration of increasing concentrations of β-HIVS, the apoptotic rate of HeLa cells was also increased. The cell cycle was slightly arrested at the S phase, with ~6% of cells in this phase, subsequent to treatment with 10 µM β-HIVS. In addition, β-HIVS markedly reduced the expression levels of PI3K, AKT, mTOR and 70-kDa ribosomal protein S6 kinase in HeLa cells. β-HIVS promoted cervical cancer cell apoptosis by inhibiting the PI3K/AKT/mTOR signaling pathway and suppressing downstream gene expression. The present study is expected to lead to the development of molecular targeted therapy for this signaling pathway as a novel method of cervical cancer treatment.

Phase 2 study of MK-2206, an allosteric inhibitor of AKT, as second-line therapy for advanced gastric and gastroesophageal junction cancer: A SWOG cooperative group trial (S1005)

BACKGROUND

The AKT inhibitor MK-2206 at a dose of 60 mg every other day was evaluated in gastric/gastroesophageal junction cancers.

METHODS

Patients who had progressed after first-line treatment were eligible. Pertinent eligibility criteria included adequate organ function, a fasting serum glucose level ≤ 150 mg/dL, and less than grade 2 malabsorption or chronic diarrhea. MK-2206 was given orally (60 evaluable patients required). The primary endpoint was overall survival, and a median survival of 6.5 months (power, 89%; significance level, 0.07) was considered encouraging for further investigation.

RESULTS

Seventy patients were included in the final analyses. The median age was 59.8 years (range, 30.4-86.7 years); 70% were male, 89% were white, and 7% were Asian. There were 2 deaths possibly related to the study drug (cardiac arrest and respiratory failure). Grade 4 adverse events included hyperglycemia, anemia, and lung infection (1 each). Grade 3 adverse events occurred in < 5% of patients except for fatigue (6%). Other adverse events (all grades) included anemia (17%), anorexia (30%), diarrhea (26%), fatigue (50%), hyperglycemia (30%), nausea (40%), vomiting (22%), dry skin (19%), maculopapular rash (30%), and acneiform rash (13%). The response rate was 1%, the median progression-free survival was 1.8 months (95% confidence interval, 1.7-1.8 months), and the median overall survival was 5.1 months (95% confidence interval, 3.7-9.4 months)

CONCLUSIONS

MK-2206 as second-line therapy was well tolerated by an unselected group of patients with gastric/gastroesophageal junction cancers, but it did not have sufficient activity (response rate, 1%; overall survival, 5.1 months) to warrant further testing in this population.

Effect of orexin A on apoptosis in BGC-823 gastric cancer cells via OX1R through the AKT signaling pathway

Orexins are a class of peptides involved in the regulation of food intake, energy homeostasis, the sleep‑wake cycle and gastrointestinal function. Recent studies have demonstrated that orexin A may influence apoptosis and proliferation in numerous types of cancer cells. However, the effect of orexin A on gastric cancer cells and its mechanisms of action remain elusive. In the present study, BGC‑823 gastric cancer cells were treated with orexin A (10‑10‑10‑6 M) in vitro and the expression levels of orexin receptor 1 (OX1R) protein in cells was then determined. The proliferation, viability and apoptosis of BGC‑823 cells were detected. In addition, BGC‑823 cells were treated with AKT inhibitor PF‑04691502 or OX1R‑specific antagonist SB334867 in combination with orexin A, in order to examine the activation of AKT and caspase‑3. The results showed that orexin A (10‑10‑10‑6 M) stimulated the OX1R protein expression in BGC‑823 cells, which improved the proliferation and viability of the cells as well as protected them from apoptosis. Phosphorylated AKT protein was significantly increased in BGC‑823 cells following treatment with orexin A. Moreover, 10‑8 M orexin A reduced the proapoptotic activity of caspase‑3 (by ≤30%). The OX1R antagonist SB334867 (10‑6 M) and AKT antagonist PF‑04691502 (10‑6 M), when used individually or in combination, abolished the effect of orexin A (10‑8 M) on BGC-823 cells. In conclusion, the results of the present study demonstrated that orexin A inhibited gastric cancer cell apoptosis via OX1R through the AKT signaling pathway.

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.

PTHrP drives breast tumor initiation, progression, and metastasis in mice and is a potential therapy target

Parathyroid hormone-related protein (PTHrP) is a secreted factor expressed in almost all normal fetal and adult tissues. It is involved in a wide range of developmental and physiological processes, including serum calcium regulation. PTHrP is also associated with the progression of skeletal metastases, and its dysregulated expression in advanced cancers causes malignancy-associated hypercalcemia. Although PTHrP is frequently expressed by breast tumors and other solid cancers, its effects on tumor progression are unclear. Here, we demonstrate in mice pleiotropic involvement of PTHrP in key steps of breast cancer - it influences the initiation and progression of primary tumors and metastases. Pthrp ablation in the mammary epithelium of the PyMT-MMTV breast cancer mouse model caused a delay in primary tumor initiation, inhibited tumor progression, and reduced metastasis to distal sites. Mechanistically, it reduced expression of molecular markers of cell proliferation (Ki67) and angiogenesis (factor VIII), antiapoptotic factor Bcl-2, cell-cycle progression regulator cyclin D1, and survival factor AKT1. PTHrP also influenced expression of the adhesion factor CXCR4, and coexpression of PTHrP and CXCR4 was crucial for metastatic spread. Importantly, PTHrP-specific neutralizing antibodies slowed the progression and metastasis of human breast cancer xenografts. Our data identify what we believe to be new functions for PTHrP in several key steps of breast cancer and suggest that PTHrP may constitute a novel target for therapeutic intervention.

BCL2L10 protein regulates apoptosis/proliferation through differential pathways in gastric cancer cells

The reason for and consequences of BCL2L10 down-regulation in gastric carcinoma are poorly understood. Our aim was to investigate the function of the protein BCL2L10 in gastric carcinoma. We investigated BCL2L10 expression using quantitative real-time PCR and immunoblotting. The methylation status of the BCL2L10 gene promoter was examined by bisulphite sequencing in fresh gastric normal and carcinoma tissues. We studied apoptosis and proliferation regulation in gastric cancer cell lines using flow cytometry, fluorescence staining, murine xenografting and immunoblotting. Pathway inhibitors were applied to confirm the major pathways involved in apoptosis or proliferation regulation. We observed significant correlations between lower BCL2L10 expression and CpG island hypermethylation of the BCL2L10 gene promoter in gastric carcinoma, apoptosis induced by over-expressed BCL2L10 through mitochondrial pathways, and proliferation accelerated by BCL2L10 siRNA via the PI3K-Akt signalling pathway in gastric cancer cell lines. The pro-apoptotic effect of BCL2L10 and growth promotion by BCL2L10 siRNA in gastric cancer cells suggest that it may be a tumour suppressor.

Novel expression patterns of PI3K/Akt/mTOR signaling pathway components in colorectal cancer

BACKGROUND

The phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway plays a critical role in the growth and progression of colorectal cancer (CRC). The purpose of our study was 2-fold: (1) to determine the expression levels of several key components of this pathway, including p85alpha, Akt1, Akt2, p-mTOR(Ser2448), and p-p70S6K(Thr389) in CRCs; and (2) to correlate the expression of these proteins with cancer stage and location (left versus right side).

STUDY DESIGN

Immunohistochemistry for p85alpha, Akt1, Akt2, p-mTOR(Ser2448), and p-p70S6K(Thr389) was performed on normal colon and CRCs from 154 patients.

RESULTS

All proteins investigated were significantly overexpressed in CRCs compared with matched normal colonic tissue from the same patient (p < 0.0001). PI3K pathway component proteins were moderately correlated across normal and malignant colon tissues; correlations tended to be stronger in normal tissues as compared with the same correlations in cancers. Expression levels of p85alpha were significantly higher in stage IV cancers than in stage I to III cancers (p = 0.0005). p85alpha expression was also significantly increased in the adjacent normal colonic mucosa of patients with stage IV CRC compared with earlier stages (p = 0.003). Finally, expression of Akt1, Akt2, and p-p70S6K(Thr389) was higher in left-sided CRCs compared with CRCs in the right colon (p = 0.007, p = 0.0008, and p = 0.04, respectively).

CONCLUSIONS

The PI3K/Akt/mTOR pathway components, p85alpha, Akt1, Akt2, p-mTOR(Ser2448), and p-p70S6K(Thr389) are highly overexpressed in CRCs, providing the rationale for targeting this pathway therapeutically in CRC patients. The increased expression of p85alpha in the adjacent normal mucosa of stage IV patients suggests an important field defect, which may contribute to the growth and progression of these cancers.

Expression of p-Akt and COX-2 in Gastric Adenocarcinomas and Adenovirus Mediated Akt1 and COX-2 ShRNA Suppresses SGC-7901 Gastric Adenocarcinoma and U251 Glioma Cell Growth In Vitro and In Vivo

Cyclooxygenase-2 (COX-2) and Protein kinase B (PKB/Akt) play a crucial role in the formation of many malignant tumors and have been shown to be the important therapeutic targets. In the present study, we examined immunohistochemical expression of phosphorylated Akt (p-Akt) and COX-2 in 45 gastric adenocarcinomas with different tumor grades. Then, adenovirus-mediated small hairpin RNA (shRNA) expression vectors rAd5-Akt1+COX-2 (rAd5-A+C) that target sequences of human COX-2 and Akt1 were used to examine the inhibitory effects on cell proliferation, invasion and apoptosis in SGC7901 gastric adenocarcinoma and U251 glioma cells. Cell growth was inhibited by over 70%, as indicated by a MTT assay, and was accompanied by G1/G0 phase arrest in the rAd5-A+C treated group, indicating poor cell growth activities. The number of cells invading through the matrigel in the rAd5-A+C treated group was significantly decreased (36.2±3.1) compared with that of the control group SGC7901 (105.0±4.0) and the nonsense sequence group rAd5-HK (102.5±6.4). In addition, the tumor volumes in the SGC7901 subcutaneous nude mouse model treated with rAd5-A+C was significantly smaller than those of the control group and nonsense sequence group rAd5-HK. When COX-2 and Akt1 were dramatically downregulated, Ki-67, CyclinD1, MMP-2, MMP-9 and Bcl-2 were also downregulated. Our results demonstrated that p-Akt and COX-2 were overexpressed in gastric adenocarcinomas and their expression levels were elevated with the ascending order of tumor malignancy; rAd5-A+C targeting COX-2 and Akt1 down-regulated their expression significantly in a sequence-specific manner, exerting inhibitory effects on SGC7901 and U251 cell proliferation, invasion and apoptosis. In conclusion, our data suggest a novel mechanism for the regulation of malignant tumor cell growth and provide evidence for combined gene therapy for malignant tumors.

Gastric cancer in the era of molecularly targeted agents: current drug development strategies

Gastric cancer is the second most common cause of cancer death worldwide with approximately one million cases diagnosed annually. Despite considerable improvements in surgical techniques, innovations in clinical diagnostics and the development of new chemotherapy regimens, the clinical outcome for patients with advanced gastric cancer and cancer of the GEJ is generally poor with 5-year survival rates ranging between 5 and 15%. The understanding of cancer relevant events has resulted in new therapeutic strategies, particularly in developing of new molecular targeted agents. These agents have the ability to target a variety of cancer relevant receptors and downstream pathways including the epidermal growth factor receptor (EGFR), the vascular endothelial growth factor receptor (VEGFR), the insulin-like growth factor receptor (IGFR), the c-Met pathway, cell-cycle pathways, and down-stream signalling pathways such as the Akt-PI3k-mTOR pathway. In the era of new molecularly targeted agents this review focuses on recent developments of targeting relevant pathways involved in gastric cancer and cancer of the GEJ.

Application of PI3K/Akt and COX-2 signal pathway blockage in treatment of gastric carcinoma

The abnormal alternation of phosphatidylinositol-3-kinase/Protein Kinase B (PI3K/PKB) and cyclooxygenase-2 (COX-2) signal pathways plays an important role in emergence and development of tumors, which also contributes to a series of biological processes and exerts a tremendous influence on treatment and prognosis of tumors. This review investigates PI3K/Akt and COX-2 signal pathways blockage and their mechanism, and provided a original direction for molecular target therapy of diverse tumors including gastric carcinoma.

Akt regulates drug-induced cell death through Bcl-w downregulation

Akt is a serine threonine kinase with a major role in transducing survival signals and regulating proteins involved in apoptosis. To find new interactors of Akt involved in cell survival, we performed a two-hybrid screening in yeast using human full-length Akt c-DNA as bait and a murine c-DNA library as prey. Among the 80 clones obtained, two were identified as Bcl-w. Bcl-w is a member of the Bcl-2 family that is essential for the regulation of cellular survival, and that is up-regulated in different human tumors, such as gastric and colorectal carcinomas. Direct interaction of Bcl-w with Akt was confirmed by immunoprecipitation assays. Subsequently, we addressed the function of this interaction: by interfering with the activity or amount of Akt, we have demonstrated that Akt modulates the amount of Bcl-w protein. We have found that inhibition of Akt activity may promote apoptosis through the downregulation of Bcl-w protein and the consequential reduction in interaction of Bcl-w with pro-apoptotic members of the Bcl-2 family. Our data provide evidence that Bcl-w is a new member of the Akt pathway and that Akt may induce anti-apoptotic signals at least in part through the regulation of the amount and activity of Bcl-w.

Akt2 overexpression plays a critical role in the establishment of colorectal cancer metastasis

Colorectal cancer is the second leading cause of cancer-related deaths in the United States. Understanding the distinct genetic and epigenetic changes contributing to the establishment and growth of metastatic lesions is crucial for the development of novel therapeutic strategies. In a search for key regulators of colorectal cancer metastasis establishment, we have found that the serine/threonine kinase Akt2, a known proto-oncogene, is highly expressed in late-stage colorectal cancer and metastatic tumors. Suppression of Akt2 expression in highly metastatic colorectal carcinoma cells inhibits their ability to metastasize in an experimental liver metastasis model. Overexpression of wild-type Akt1 did not restore metastatic potential in cells with downregulated Akt2, thus suggesting non-redundant roles for the individual Akt isoforms. In contrast, Akt2 overexpression in wild-type PTEN expressing SW480 colorectal cancer cells led to the formation of micrometastases; however, loss of PTEN is required for sustained formation of overt metastasis. Finally, we found that the consequence of PTEN loss and Akt2 overexpression function synergistically to promote metastasis. These results support a role for Akt2 overexpression in metastatic colorectal cancer and establish a mechanistic link between Akt2 overexpression and PTEN mutation in metastatic tumor establishment and growth. Taken together, these data suggest that Akt family members have distinct functional roles in tumor progression and that selective targeting of the PI3K/Akt2 pathway may provide a novel treatment strategy for colorectal cancer metastasis.

Activated Akt as an indicator of prognosis in gastric cancer

The immunohistochemical expression of phosphorylated (activated) Akt (pAkt) in 50 advanced gastric carcinomas has been analyzed and the results correlated with age, sex, location in the stomach, histotype, stage, survival, mitotic and apoptotic index, some cell cycle regulators (cyclin D1, cyclin E, p34/cdc2, p27/kip1), and cell proliferation. There was a statistically significant direct correlation between pAkt expression (both cytoplasmatic and nuclear) and depth of infiltration of the tumor, number of infiltrated lymph nodes and p34/cdc2 expression, and between prevalently nuclear pAkt and cyclin D1 and cyclin E. Conversely, there was a significant inverse correlation between nuclear pAkt and apoptotic index and between cytoplasmatic and nuclear pAkt and patient survival. No correlation was found between pAkt and sex, age, tumor location, histotype, mitotic index, and cell proliferation. These findings suggest that pAkt may be considered an indicator of tumor progression and patient survival in gastric cancer.