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.

Background Gastric cancer (GC) is a deadly malignancy worldwide. In the past, it has been shown that cellular signaling pathway alterations play a crucial role in the development of GC. In particular, deregulation of the PI3K/AKT/mTOR pathway seems to affect multiple GC functions including growth, proliferation, metabolism, motility and angiogenesis. Targeting alterations in this pathway by microRNAs (miRNAs) represents a potential therapeutic strategy, especially in inhibitor-resistant tumors. The objective of this study was to evaluate the expression of 3 pre-selected miRNAs, miR-101-2, miR-125b-2 and miR-451a, in a series of primary GC tissues and matched non-GC tissues and in several GC-derived cell lines, and to subsequently evaluate the functional role of these miRNAs. Methods Twenty-five primary GC samples, 25 matched non-GC samples and 3 GC-derived cell lines, i.e., AGS, MKN28 and MKN45, were included in this study. miRNA and target gene expression levels were assessed by quantitative RT-PCR and western blotting, respectively. Subsequently, cell viability, clone formation, cell death, migration and invasion assays were performed on AGS cells. Results miR-101-2, miR-125b-2 and miR-451a were found to be down-regulated in the primary GC tissues and the GC-derived cell lines tested. MiRNA mimic transfections significantly reduced cell viability and colony formation, increased cell death and reduced cell migration and invasion in AGS cells. We also found that exogenous expression of miR-101-2, miR-125b-2 and miR-451a decreased the expression of their putative targets MTOR, PIK3CB and TSC1, respectively. Conclusions Our expression analyses and in vitro functional assays suggest that miR-101-2, miR-125b-2 and miR-451a act as potential tumor suppressors in primary GCs as well as in GC-derived AGS cells.

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.

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