Putative role of the mTOR/4E-BP1 signaling pathway in the carcinogenesis and progression of gastric cardiac adenocarcinoma

Long Non-Coding RNAs (lncRNAs) as Regulators of the PI3K/AKT/mTOR Pathway in Gastric Carcinoma

Gastric cancer (GC) represents ~10% of the global cancer-related deaths, increasingly affecting the younger population in active stages of life. The high mortality of GC is due to late diagnosis, the presence of metastasis and drug resistance development. Additionally, current clinical markers do not guide the patient management adequately, thereby new and more reliable biomarkers and therapeutic targets are still needed for this disease. RNA-seq technology has allowed the discovery of new types of RNA transcripts including long non-coding RNAs (lncRNAs), which are able to regulate the gene/protein expression of many signaling pathways (e.g., the PI3K/AKT/mTOR pathway) in cancer cells by diverse molecular mechanisms. In addition, these lncRNAs might also be proposed as promising diagnostic or prognostic biomarkers or as potential therapeutic targets in GC. This review describes important topics about some lncRNAs that have been described as regulators of the PI3K/AKT/mTOR signaling pathway, and hence, their potential oncogenic role in the development of this malignancy.

Mealworm Ethanol Extract Enhances Myogenic Differentiation and Alleviates Dexamethasone-Induced Muscle Atrophy in C2C12 Cells

Aging, and other disease-related muscle disorders are serious health problems. Dexamethasone (DEX), a synthetic glucocorticoid, can trigger skeletal muscle atrophy. This study examined the effects of mealworm (Tenebrio molitor larva) ethanol extract (TME) on C2C12 myoblast differentiation and DEX-induced myotube atrophy. TME induced myotube formation compared to the differentiation medium (DM) group. TME also significantly increased the mRNA expression of muscle creatine kinase (CKm) and myogenic regulatory factors (MRFs), such as myogenin (MyoG), myogenic factor (Myf)5, and MRF4 (Myf6). TME dramatically increased the muscle-specific protein, MyoG, compared to the control, whereas the expression of myogenic differentiation 1 (MyoD) remained unchanged. It also activated the mammalian target of rapamycin (mTOR) signaling pathway. In the DEX-induced muscle atrophy C2C12 model, TME reduced the gene expression of atrogin-1, muscle RING finger protein-1 (MuRF-1), and myostatin, which are involved in protein degradation in skeletal muscles. Furthermore, TME elevated the phosphorylation of forkhead box O3 (FoxO3α) and protein kinase B (Akt). These findings suggest that TME can enhance myotube hypertrophy by regulating the mTOR signaling pathway, and can rescue DEX-induced muscle atrophy by alleviating atrophic muscle markers mediated by Akt activation. Thus, TME can be a potential therapeutic agent for treating muscle weakness and atrophy.

Pharmacogenomic Testing to Guide Personalized Cancer Medicine Decisions in Private Oncology Practice: A Case Study

Innovative tumor profiling methodologies are utilized to elucidate the pharmacogenomic landscape of tumor cells in order to support the molecularly guided delivery of therapeutics. Indeed, improved clinical outcomes are achieved in oncology practice by providing the physicians with expert-guided, standardized, and easily interpretable knowledge, translated from molecular profiling analysis to support clinical decision-making. However, there is still limited utilization of the technology especially in small private oncology practices. In this work, we analyzed how molecularly guided interventions in 17 consented cancer patients led to an overall improvement of disease response rates in a private oncology center. The precision medicine strategy was based on the OncoDEEP™ profiling solutions and focused on finding clinically actionable relationships between tumor biomarkers and drug responses. The obtained data support the notion that (a) following the pharmacogenomic-derived recommendations favorably impacted cancer therapy progression, and (b) the earlier profiling followed by the delivery of molecularly targeted therapy led to more durable and improved pharmacological response rates. Moreover, we report the example of a patient with metastatic gastric adenocarcinoma who, based on the molecular profiling data, received an off-label therapy that resulted in a complete response and a current cancer-free maintenance status. Overall, our data provide a paradigm on how molecular tumor profiling can improve decision-making in the routine private oncology practice.

CYP2E1 changes the biological function of gastric cancer cells via the PI3K/Akt/mTOR signaling pathway

The present study investigated the role of cytochrome P450 family 2 subfamily E polypeptide 1 (CYP2E1) in the development and progression of gastric cancer (GC). The expression levels of CYP2E1 in MGC‑803 GC cells and normal GES‑1 cells were investigated via western blotting, and it was identified that the expression of CYP2E1 was different between GES‑1 and MGC‑803 cells. CYP2E1 was overexpressed in MGC‑803 cells using a lentiviral vector GV358. Cell Counting Kit‑8, flow cytometry, cell migration and Matrigel invasion assays suggested that overexpression of CYP2E1 promoted the proliferation and invasion, and inhibited the apoptosis of GC cells. The relationship between CYP2E1 expression and key signaling molecules in the PI3K/Akt/mTOR signaling pathway was assessed. Reverse transcription‑quantitative PCR analysis showed that mTOR mRNA expression was significantly increased after overexpression of CYP2E1 (P<0.05). Western blotting results showed that overexpression of CYP2E1 upregulated the expression of phosphorylated (p)‑Akt, p‑mTOR and p‑p70 ribosomal protein S6 kinase (P70S6K; Ser371) proteins (P<0.05). To further investigate the relationship between CYP2E1 and the PI3K/Akt/mTOR signaling pathway in GC cells, MGC‑803 cells were treated with the PI3K inhibitor LY294002, and changes in the expression levels of PI3K, AKT, mTOR, P70S6K and CYP2E1 were observed. The present results showed that LY294002 downregulated the expression of PI3K, CYP2E1, AKT, mTOR and P70S6K (P<0.05). Therefore, changes in the biological function of GC cells induced by CYP2E1 overexpression may be via the PI3K/Akt/mTOR signaling pathway.

eIF4E is a critical regulator of human papillomavirus (HPV)-immortalized cervical epithelial (H8) cell growth induced by nicotine

Tobacco smoke is known as a cofactor in the development of cervical precancer and cancer caused by human papillomavirus (HPV). The main component in cigarette smoke, nicotine, can be concentrated more strongly in cervical mucus than in blood and it has been implicated as a cocarcinogen that promotes a serial of cancers development through multiple prosurvival pathways. Although the mechanisms of nicotine-induced cell proliferation have been well studied in some epithelial cells, the molecular mechanism of its action in cervical epithelial cells is still unclear. The aims of this study were to investigate the detailed mechanism by which nicotine could induce cervical cancer growth. We found that nicotine simultaneously activates AKT/mTOR pathway in HPV-immortalized cervical epithelial (H8) cell line, followed by elevation of 4EBP1/eIF4E axis expression and its translational activity with dose-dependent and time-dependent manners. Besides, nicotine decreases eIF4E-4EBP1 binding activity in H8 cell line, which is associated with increased expression of phospho-4EBP1 at threonine 70. We therefore chose to evaluate whether this effect on eIF4E was involved in nicotine-induced proliferation. Remarkably, eIF4E knockdown by small interfering RNA diminishes its translation activity to the downstream targets including c-Myc, VEGF, CyclinD1 and Bcl-2. What is more, eIF4E knockdown inhibits cellular growth and colony formation after nicotine treatment. Note as well that eIF4E-specific siRNA could also suppress cell proliferation by decelerating the G0/G1-S transition of H8 cell treated with nicotine. Taken together, it can be concluded that nicotine promotes H8 cell proliferation by activating AKT/mTOR pathway, as well as 4EBP1/eIF4E axis and its translational activity. Furthermore, phosphorylation of 4EBP1 induced by nicotine has been shown to cause dissociation of 4EBP1/eIF4E and eIF4E may serve as a promising determinant of nicotine activity in vitro.

Hypermethylation of EIF4E promoter is associated with early onset of gastric cancer

Although gastric cancer (GC) in young adults (≤ 45 years) accounts for fewer than 10% of newly diagnosed cases, the young patients are more likely to have advanced disease at presentation compared with elderly patients. Previous studies have identified that the DNA methylation of genomes are different during aging. Our study aimed to explore the association between DNA methylation and the onset of GC. We applied Illumina HumanMethylation450 BeadChip to examine methylation expression profiles and compared methylation expression patterns in five early onset GC patients and seven elderly patients. Additionally, we evaluated the associations of methylation expression with different clinicopathological characteristics of GC. Our results showed that the pattern of genome-wide methylation expression was significantly different between early onset and elderly GC. The top 10 hypomethylation and hypermethylation CpG sites were selected for further analyses in The Cancer Genome Atlas (TCGA) database. We found that the hypermethylation of cg11037477, located at the promoter of EIF4E, was significantly associated with age at diagnosis and the expression of EIF4E. Besides, GC patients with high level of cg11037477 were more likely to have advance disease with T3/T4 invasion and III/IV stage. The cg11037477 hypermethylation and EIF4E down-expression were significantly related to poor survival of GC patients. Our study provides new insights into the molecular mechanism of early onset patients with GC and suggests that methylation of cg11037477 and expression of EIF4E may act as prognostic markers in GC.

Tumor-biopsy stratification based on mTOR-pathway activity and functional mutations in the upstream genes PIK3CA and PTEN

The mechanistic target of the rapamycin (mTOR) pathway is frequently activated in human cancers. Our objective was to evaluate relationships between mTOR-pathway activity and functional mutations in the upstream genes PIK3CA and PTEN in solid-tumor biopsies from a broad selection of cancer types. Formalin-fixed paraffin-embedded (FFPE) tumor samples were analyzed by immunohistochemistry (IHC) and next-generation sequencing (NGS). TOR-pathway activation was identified by expression (by IHC) of the downstream effector p-4E-BP1. Activating PIK3CA mutations and null PTEN mutations were identified by NGS, and for PTEN, confirmed by IHC. Overall, mTOR-pathway activation was identified in 444/538 (83%) samples representing 40 different cancer types. Functional mutations in either or both PIK3CA and PTEN genes were identified in 173/538 (32%) samples. PIK3CA mutations were identified in 60/538 (11%) samples, PTEN mutations were identified in 155/538 (29%) samples and mutations in both PIK3CA and PTEN were identified in 18/538 (3%) samples. Overall, mTOR-pathway activation was not significantly associated with the PIK3CA and PTEN genotypes. However, all 18 samples with both PIK3CA and PTEN mutations also displayed mTOR-pathway activation (χ²p=0.0471). Also, out of a total of 95 breast cancer samples, there were 5 breast-cancer samples which did not have mTOR-pathway activation, and all 5 (100%) of these had PIK3CA and PTEN mutations compared to 51/90 (57%) in the breast-cancer samples with mTOR-pathway activation (χ²p=0.0134). Finally, the percentages of PIK3CA mutations were higher in colorectal-cancer samples which had mTOR-pathway activation (9/27, 33%) than in colorectal-cancer samples without mTOR-pathway activation (6/44; 14%; χ² p=0.0484). Therefore, tumor-biopsy analyses based on combined mTOR-pathway biomarkers (and combined NGS and IHC assessments) could potentially provide treatment-informative stratification for particular cancer types.

Phosphorylated Mammalian Target of Rapamycin p-mTOR Is a Favorable Prognostic Factor than mTOR in Gastric Cancer

Aims

The mammalian target of rapamycin (mTOR) and phosphorylated mTOR (p-mTOR) occurring downstream in the PI3K/Akt/mTOR pathway, are regarded as potential prognostic markers for gastric cancer (GC). However, the prognostic value of mTOR/p-mTOR expression remains controversial. In this study, we determined the expression of mTOR, p-mTOR, p70S6k, and p-p70S6K in GC, and investigated the correlation between their overexpression, clinicopathological parameters, and overall survival (OS).

Methods

The expression of mTOR, p-mTOR, p70S6k, and p-p70S6K was examined in 120 GC patients by immunohistochemistry (IHC). The association of protein expression with clinicopathological features and OS was explored. The p-mTOR expression was detected in normal, adjacent, and GC tissues using Western blot. Eligible studies retrieved from PubMed, Ovid, Web of Science and Cochrane databases, were reviewed in this meta-analysis.

Results

IHC showed that the rates of expression of the signal transduction molecules mTOR, p-mTOR, p70S6k and p-p70S6K in GC were 60.8%, 54.2%, 53.3% and 53.3%, respectively. Overexpression of mTOR and p70S6K showed no significant association with clinical variables. Expression of p-mTOR was significantly associated with differentiation (P < 0.01), depth of invasion (P < 0.01), lymph node metastasis (P = 0.04) and TNM stage (P = 0.02). Expression of p-p70S6K was associated with differentiation (P = 0.006), depth of invasion (P < 0.001), and TNM stage (P = 0.02). In survival analysis, differentiation, depth of invasion, lymph node metastasis and TNM stage were not related to OS (all P > 0.05). Furthermore, p-mTOR and p-p70S6K expression, but not mTOR and p70S6K, were tightly associated with OS of GC patients (P = 0.006 and P < 0.001, respectively). In Western blot, p-mTOR was significantly higher in GC tissues than in normal and adjacent tissues. In the present meta-analysis, mTOR overexpression showed no relationship with any clinicopathological variables. However, p-mTOR was correlated with depth of invasion, and TNM stage (all P < 0.05), and its overexpression was associated with a shorter survival time (P < 0.001).

Conclusion

The results suggest that p-mTOR is a more valuable prognostic factor than mTOR in GC.

The Gene Expression Status of the PI3K/AKT/mTOR Pathway in Gastric Cancer Tissues and Cell Lines

The PI3K/AKT/mTOR pathway plays a crucial role in the regulation of multiple cellular functions including cell growth, proliferation, metabolism and angiogenesis. Emerging evidence has shown that deregulation of this pathway has a role promoting gastric cancer (GC). The aim was to assess the expression of genes involved in this pathway by qPCR in 23 tumor and 23 non-tumor gastric mucosa samples from advanced GC patients, and in AGS, MKN28 and MKN45 gastric cancer cell lines. Results showed a slight overexpression of PIK3CA, PIK3CB, AKT1, MTOR, RPS6KB1, EIF4EBP1 and EIF4E genes, and a slightly decreased PTEN and TSC1 expression. In AGS, MKN28 and MKN45 cells a significant gene overexpression of PIK3CA, PIK3CB, AKT1, MTOR, RPS6KB1 and EIF4E, and a significant repression of PTEN gene expression were observed. Immunoblotting showed that PI3K-β, AKT, p-AKT, PTEN, mTOR, p-mTOR, P70S6K1, p-P70S6K1, 4E-BP1, p-4E-BP1, eIF4E and p-eIF4E proteins were present in cell lines at different levels, confirming activation of this pathway in vitro. This is the first time this extensive panel of 9 genes within PI3K/AKT/mTOR pathway has been studied in GC to clarify the biological role of this pathway in GC and develop new strategies for this malignancy.

Integrin β6 can be translationally regulated by eukaryotic initiation factor 4E: Contributing to colonic tumor malignancy

It is well known that both eukaryotic initiation factor 4E (eIF4E) and integrin αvβ6 can contribute to malignant behavior of colon cancer. We have found that integrin αvβ6 and eIF4E were co-expressed and positively correlated in colon cancer tissues. Recently, deregulation of the protein synthesis apparatus has begun to gain attention as a major participant in cancer development and progression. However, the regulation of integrin β6 expression at translational level has never been investigated before. In present study, gene-silencing technique for eIF4E by small interfering RNA (siRNA) was used in all the subsequent experiments, in order to investigate whether eIF4E could translationally regulate expression of integrin β6 in colon cancer SW480 and HT-29 cell lines. Additionally, the subsequent effects of eIF4E knockdown on cellular malignant behavior were observed. siRNA in SW480 and HT-29 transfectants. Subsequently, protein expression of β6 was markedly suppressed, while mRNA expression of β6 showed no significant variation before and after eIF4E RNA interfering. Therefore, it could be seen that eIF4E could upregulate the expression of β6, without effect on β6 mRNA expression. More importantly, after treated with eIF4E siRNA, cellular migratory capacity on fibronectin of HT-29 and β6-transfected SW480 as well as their survival to 5-FU was decreased distinctly. Expression of integrin β6 could be translationally regulated by eIF4E, which subsequently contributed to tumor malignancy through enhancing cellular migration, survival, anti-apoptosis, and chemoresistance of colon cancer in vitro. Thus, targeting eIF4E in integrin αvβ6 expressing tumors can be a potential therapeutic strategy for patients with colon cancer.

The PI3K/AKT/mTOR pathway is activated in gastric cancer with potential prognostic and predictive significance

Signaling pathway alterations are important in the development of gastric cancer (GC). Deregulation of the PI3K/AKT/mTOR pathway plays a crucial role in the regulation of multiple cellular functions including cell growth, proliferation, metabolism, and angiogenesis. Our goal was to assess expression of proteins involved in the PI3K/AKT/mTOR pathway by immunohistochemistry (IHC) in tumor and nontumor gastric mucosa from patients with advanced GC. We evaluated 71 tumor and 71 nontumor gastric mucosa samples from advanced GC patients, selected from Hernán Henríquez Aravena Hospital (Temuco, Chile). The targets studied were PI3K, AKT, p-AKT, PTEN, mTOR, p-mTOR, P70S6K1, p-P70S6K1, 4E-BP1, p-4E-BP1, eIF4E, and p-eIF4E. Expression data were correlated with clinicomorphological data. Descriptive and analytical statistics were used (95 % confidence interval, p < 0.05). For survival analyses, the Kaplan-Meier method and the log-rank test were used. PI3K, AKT, p-AKT, p-mTOR, p-4E-BP1, P70S6K1, p-P70S6K1, eIF-4E, and p-eIF-4E proteins were significantly overexpressed in tumor tissue. Conversely, PTEN was underexpressed in tumor tissue, notably in pT3-pT4 tumors (p = 0.02) and tumors with lymph node metastases (p < 0.001). P70S6K1 expression was associated with pT3-pT4 tumors (p = 0.03). Moreover, PI3K (p = 0.004), AKT (p = 0.01), p-AKT (p = 0.01), P70S6K1 (p = 0.04), p-P70S6K1 (p = 0.001), and eIF-4E (p = 0.004) were overexpressed in tumors with lymph node metastases. Low expression of 4E-BP1 was associated with poor overall survival (p = 0.03). Our results suggest that the PI3K/AKT/mTOR pathway is activated in GC, with overexpression in tumor tissue of most of the studied proteins (total and phosphorylated). These might be considered as target for specific targeted therapy in GC.