Phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling is one of the most important intracellular pathways, which can be considered as a master regulator for cancer. Enormous efforts have been dedicated to the development of drugs targeting PI3K signaling, many of which are currently employed in clinical trials evaluation, and it is becoming increasingly clear that PI3K inhibitors are effective in inhibiting tumor progression. PI3K inhibitors are subdivided into dual PI3K/mTOR inhibitors, pan-PI3K inhibitors and isoform-specific inhibitors. In this review, we performed a critical review to summarize the role of the PI3K pathway in tumor development, recent PI3K inhibitors development based on clinical trials, and the mechanisms of resistance to PI3K inhibition.

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Targeting PI3K in cancer: mechanisms and advances in clinical trials

MicroRNAs (miRNAs) are endogenous ∼23 nt RNAs that play important gene-regulatory roles in animals and plants by pairing to the mRNAs of protein-coding genes to direct their posttranscriptional repression. This review outlines the current understanding of miRNA target recognition in animals and discusses the widespread impact of miRNAs on both the expression and evolution of protein-coding genes.

MicroRNAs: Target Recognition and Regulatory Functions

A polycistronic microRNA cluster, miR-17-92, is overexpressed in human lung cancers and enhances cell proliferation

Long non-coding (lnc) RNAs are non-coding RNAs longer than 200 nt. lncRNAs primarily interact with mRNA, DNA, protein, and miRNA and consequently regulate gene expression at the epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels in a variety of ways. They play important roles in biological processes such as chromatin remodeling, transcriptional activation, transcriptional interference, RNA processing, and mRNA translation. lncRNAs have important functions in plant growth and development; biotic and abiotic stress responses; and in regulation of cell differentiation, the cell cycle, and the occurrence of many diseases in humans and animals. In this review, we summarize the functions and mechanisms of lncRNAs in plants, humans, and animals at different regulatory levels.

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Mechanisms and Functions of Long Non-Coding RNAs at Multiple Regulatory Levels

Given that the PI3K/AKT pathway has manifested its compelling influence on multiple cellular process, we further review the roles of hyperactivation of PI3K/AKT pathway in various human cancers. We state the abnormalities of PI3K/AKT pathway in different cancers, which are closely related with tumorigenesis, proliferation, growth, apoptosis, invasion, metastasis, epithelial-mesenchymal transition, stem-like phenotype, immune microenvironment and drug resistance of cancer cells. In addition, we investigated the current clinical trials of inhibitors against PI3K/AKT pathway in cancers and found that the clinical efficacy of these inhibitors as monotherapy has so far been limited despite of the promising preclinical activity, which means combinations of targeted therapy may achieve better efficacies in cancers. In short, we hope to feature PI3K/AKT pathway in cancers to the clinic and bring the new promising to patients for targeted therapies.

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Role of PI3K/AKT pathway in cancer: the framework of malignant behavior.

Accumulating evidence suggests long noncoding RNAs (lncRNAs) play an important role in cancer progression. However, the function of lncRNA SNHG7 in colorectal cancer (CRC) remains unclear. In this study, SNHG7 expression was significantly upregulated in CRC tissues, especially in aggressive cases. In accordance, high level of SNHG7 was observed in CRC cell lines compared to normal colon cells. Furthermore, SNHG7 overexpression promoted the proliferation, migration, and invasion of CRC cell lines, while SNHG7 depletion inhibited invasion and cell viability in vitro. Mechanistically, knockdown of SNHG7 inhibited GALNT1 and EMT markers (E-cadherin and Vimentin). Importantly, SNHG7 directly interacted with miR-216b and downregulation of miR-216b reversed efficiently the suppression of GALNT1 induced by SNHG7 siRNA. Moreover, overexpression of SNHG7 significantly enhanced the tumorigenesis and liver metastasis of SW480 cells in vivo. SNHG7 positively regulated GALNT1 level through sponging miR-216b, and played an oncogenic role in CRC progression. Together, our study elucidated the role of SNHG7 as an miRNA sponge in CRC, and shed new light on lncRNA-directed diagnostics and therapeutics in CRC.

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LncRNA SNHG7 sponges miR-216b to promote proliferation and liver metastasis of colorectal cancer through upregulating GALNT1.

Colorectal cancer (CRC) arises in a multistep molecular network process, which is from either discrete genetic perturbation or epigenetic dysregulation. The long non-coding RNAs (lncRNAs), emerging as key molecules in human malignancy, has become one of the hot topics in RNA biology. Aberrant O-glycosylation is a well-described hallmark of many cancers. GALNT7 acts as a glycosyltransferase in protein O-glycosylation, involving in the occurrence and development of CRC. The microarrays were used to survey the lncRNA and mRNA expression profiles of primary CRC cell line SW480 and metastatic CRC cell line SW620. Cell proliferation, migration, invasion, and apoptosis were assayed. Xenograft mouse models were used to determine the role of lncRNA-SNHG7 in CRC in vivo. In addition, CNC analysis and competing endogenous analysis were used to detect differential SNHG7 and relational miRNAs expression in CRC cell lines. SNHG7 expression showed a high fold (SW620/SW480) in CRC microarrays. The CRC patients with high expression of SNHG7 had a significantly poor prognosis. Furthermore, SNHG7 promoted CRC cell proliferation, metastasis, mediated cell cycle, and inhibited apoptosis. SNHG7 and GALNT7 were observed for co-expression by CNC analysis, and a negative correlation of SNHG7 and miR-34a were found by competing endogenous RNA (ceRNA) analysis. Further results indicated that SNHG7 facilitated the proliferation and metastasis as a competing endogenous RNA to regulate GALNT7 expression by sponging miR-34a in CRC cell lines. SNHG7 also played the oncogenic role in regulating PI3K/Akt/mTOR pathway by competing endogenous miR-34a and GALNT7. The CRC-related SNHG7 and miR-34a might be implicated in CRC progression via GALNT7, suggesting the potential usage of SNHG7/miR-34a/GALNT7 axis in CRC treatment.

/pdf/long-non-coding-rna-snhg7-acts-as-a-target-of-mir-34a-to-1wlpx9toux.pdf

Long non-coding RNA-SNHG7 acts as a target of miR-34a to increase GALNT7 level and regulate PI3K/Akt/mTOR pathway in colorectal cancer progression.

Accumulating evidences have revealed that dysregulated microRNAs (miRNAs) involve in the tumorigenesis, progression and even lead to poor prognosis of various carcinomas, including breast cancer MiRNA-106b-5p (miR-106b) and miRNA-93-5p (miR-93) levels were confirmed to be significantly upregulated in breast cancer clinical samples (n=36) and metastatic cell line (MDA-MB-231) compared with those in the paired adjacent tissues and normal breast epithelial cell line (MCF-10A) Moreover, further research stated that the capability of migration, invasion and proliferation changed along with the altered expression of miR-106b and miR-93 in breast cancer PTEN, the tumor-suppressor gene, was discovered to be reduced in breast cancer tissues or MDA-MB-231 cells with high levels of miR-106b and miR-93, which were inversely expressed in PTEN overexpression tissues or cells Based on the investigation, miR-106b and miR-93 induced the migration, invasion and proliferation and simultaneously enhanced the activity of phosphatidylinositol-3 kinase (PI3K)/Akt pathway of MCF-7 cells, which could be blocked by upregulation of PTEN Furthermore, suppression of PTEN reversed the function induced by anti-miR-106b and anti-miR-93 in MDA-MB-231 cells, indicating that PTEN was directly targeted by these miRNAs and acted as the potential therapeutic target for breast cancer therapy In short, reductive PTEN mediated by miR-106b and miR-93 promoted cell progression through PI3K/Akt pathway in breast cancer

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MiR-106b and miR-93 regulate cell progression by suppression of PTEN via PI3K/Akt pathway in breast cancer.

Osteoarthritis (OA) is a chronic joint disease and hard to cure at present. Accumulating evidence suggests long noncoding RNA-HOTAIR (lncRNA-HOTAIR) plays important role in OA progression. However, the underlying molecular mechanism of HOTAIR in OA progression has not been well elucidated. In the present study, we identified that HOTAIR level was upregulated in OA cartilage tissues. High expression of HOTAIR was correlated with modified Mankin scale, extracellular matrix (ECM) degradation and chondrocytes apoptosis. The expression of miR-17-5p was down-regulated, while alpha-1, 2 fucosyltransferase 2 (FUT2) was increased in OA progression. Luciferase reporter and RNA immunoprecipitation (RIP) assays indicated that HOTAIR could directly bind to miR-17-5p and indirectly upregulate FUT2 level. Functional investigation revealed HOTAIR and FUT2 aggravated ECM degradation and chondrocytes apoptosis, and this effect could be reversed by miR-17-5p. Altered FUT2 modulated the activity of wnt/β-catenin pathway and HOTAIR/miR-17-5p also mediated wnt/β-catenin pathway through FUT2. Collectively, our findings indicated that HOTAIR/miR-17-5p/FUT2 axis contributed to OA progression via wnt/β-catenin pathway, which might provide novel insights into the function of lncRNA-driven in OA.

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Long non-coding RNA HOTAIR promotes osteoarthritis progression via miR-17-5p/FUT2/β-catenin axis

Exosomes are vesicles of endocytic origin released by various cell types and emerging as important mediators in tumor cells. Human metastases-associated lung adenocarcinoma transcript 1 (MALAT1) is a long non-coding RNA known to promote cell proliferation, metastasis, and invasion in colorectal cancer (CRC). The expression of MALAT1 was analyzed in CRC using qRT-PCR. FUT4 and fucosylation levels were detected in CRC clinical samples and CRC cell lines by immunofluorescent staining, western blot and lectin blot analysis. CRC derived exosomes were isolated and used to examine their tumor-promoting effects in vitro and in vivo. The invasive and metastatic abilities of primary CRC cells were enhanced after exposure to exosomes derived from highly metastatic CRC cells, which increased the fucosyltransferase 4 (FUT4) levels and fucosylation not by directly transmitting FUT4 mRNA. Exosomal MALAT1 increased FUT4 expresssion via sponging miR-26a/26b. Furthermore, MALAT1/miR-26a/26b/FUT4 axis played an important role in exosome-mediated CRC progression. Exosomal MALAT1 also mediated FUT4-associated fucosylation and activated the PI3K/AKT/mTOR pathway. These data indicated that exosomal MALAT1 promoted the malignant behavior of CRC cells by sponging miR-26a/26b via regulating FUT4 and activating PI3K/Akt/mTOR pathway.

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Yujia Shan

Papers

LncRNA SNHG7 sponges miR-216b to promote proliferation and liver metastasis of colorectal cancer through upregulating GALNT1.

Long non-coding RNA-SNHG7 acts as a target of miR-34a to increase GALNT7 level and regulate PI3K/Akt/mTOR pathway in colorectal cancer progression.

MiR-106b and miR-93 regulate cell progression by suppression of PTEN via PI3K/Akt pathway in breast cancer.

Long non-coding RNA HOTAIR promotes osteoarthritis progression via miR-17-5p/FUT2/β-catenin axis

Exosomal MALAT1 sponges miR-26a/26b to promote the invasion and metastasis of colorectal cancer via FUT4 enhanced fucosylation and PI3K/Akt pathway.