MicroRNAs and the PTEN/PI3K/Akt pathway in gastric cancer

Gastric carcinogenesis arises from complicated interactions among host, environmental and bacterial factors, which cause genetic and epigenetic dysregulation of oncogenic and tumor-suppressive genes. MicroRNAs (miRNAs), a class of small non-coding RNAs that post-transcriptionally regulate 30% human genes, may serve as oncogenes or tumor-suppressors in malignancies, including gastric cancer (GC). Although miRNA dysregulation commonly exists in GC, exact roles miRNAs serve in the pathogenesis and promotion of this tumor remain undetermined. Recently, results of previous studies regarding mechanisms underlying miRNAs generally converged on pathways critical in cellular processes, including cell proliferation, apoptosis and invasion, among which phosphatase and tensin homolog (PTEN)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling is a fundamental one, with frequent oncogenic alterations in GC. Therefore, in the present review, the disorder and function of miRNAs and PTEN/PI3K/Akt signaling in GC are discussed. Additionally, how miRNAs transduce their effects by regulating this pathway, particularly in GC stem cells and the tumor microenvironment, and two novel hypotheses significant in carcinogenesis, tumor progression and recurrence, are discussed. Furthermore, the roles of miRNAs and the PTEN/PI3K/Akt pathway in target therapies against this lethal disease are outlined.