LncRNA NRON promotes tumorigenesis by enhancing MDM2 activity toward tumor suppressor substrates

Kaempferol targets Src to exert its chemopreventive effects on mammary tumorigenesis via regulation of the PI3K/AKT pathway

BACKGROUND

Breast cancer (BC) is a prevalent malignancy that poses significant risks to the health of women worldwide. The incidence and mortality rates of BC continue to be high, despite improvements in diagnosis and treatment, indicating a need for novel prevention strategies. Kaempferol (KAM) is a common dietary flavonoid with known antitumour properties, but its role in the chemoprevention of BC and the underlying mechanisms largely unexplored.

PURPOSE

This study aimed to evaluate the chemopreventive effects of KAM on carcinogen-induced BC in vivo and in vitro and to elucidate the underlying molecular mechanisms.

METHODS

In this study, we used an N-methyl-N-nitrosourea (NMU)-induced rat model of BC and 17β-oestradiol (E2)-treated MCF-10A cells to evaluate the chemopreventive effects of KAM on mammary tumorigenesis. The antioxidant capacity of KAM was assessed by measuring oxidative damage marker levels and antioxidant enzyme expression. Flow cytometry and Hoechst 33258 staining were utilized to analyse cell cycle distribution and apoptosis. The core target of KAM was identified by network pharmacology and validated by molecular docking, MD simulation, CESTA, and BLI. KEGG enrichment analysis, molecular biology tests and the application of specific protein inhibitors were conducted to elucidate the molecular mechanisms modulated by KAM.

RESULTS

In vivo, KAM inhibited the progression of mammary tumours and delayed pathological changes in the morphological structure of mammary gland cells to varying degrees. In vitro, KAM reduced cell viability, migration, and anchorage-independent growth while triggering cell cycle arrest and apoptosis in E2-treated MCF-10A cells. Furthermore, KAM increased cellular antioxidant capacity and attenuated E2-induced oxidative stress. Mechanistically, KAM directly interacted with Src and inhibited its phosphorylation, thus leading to PI3K/AKT pathway inhibition. Notably, the inhibition of E2-induced cell migration and anchorage-independent growth in vitro by Src- or PI3K/AKT pathway-specific inhibitors was not further enhanced when the cells were cultured with KAM.

CONCLUSION

In summary, KAM targets the Src-mediated PI3K/AKT pathway to reduce oxidative stress and facilitate apoptosis and cell cycle arrest, thereby inhibiting mammary tumorigenesis. Our study is the first to identify Src kinase as a direct target of KAM in mammary tumorigenesis. These findings give significant perspectives on the potential application of KAM in BC chemoprevention.

AKT1E17K-Interacting lncRNA SVIL-AS1 Promotes AKT1 Oncogenic Functions by Preferentially Blocking AKT1E17K Dephosphorylation

AKT1E17K is a gain-of-function mutation that constitutively activates the PI3K-AKT pathway. However, how AKT1E17K is regulated in cancer pathogenesis remains elusive. Here, RNA immunoprecipitation sequencing (RIP-seq) is performed to interrogate the AKT1E17K-interacting lncRNAs and identify that SVIL-AS1 preferentially binds to AKT1E17K rather than AKT1WT proteins. It is found that SVIL-AS1 enhances AKT1 phosphorylation and downstream signaling. SVIL-AS1 knockdown dramatically inhibits the growth of AKT1E17K cells in vitro and in vivo. Notably, AKT1 and SVIL-AS1 interaction is AKT1 phosphorylation-dependent. SVIL-AS1 also interacts with PPP2R2A, a subunit of phosphatase PP2A holoenzyme, and blocks the binding of PPP2R2A to AKT1E17K to prevent AKT1 dephosphorylation. Moreover, AKT1E17K cells are not effectively inhibited by the allosteric AKT inhibitor, whereas silencing SVIL-AS1 sensitizes AKT1E17K cells to AKT1 allosteric inhibitor, as well as the PI3Kα inhibitor. In breast cancer tissues, SVIL-AS1 is highly expressed and associated with p-AKT1 level and poor prognosis of patients. Together, the findings discover a novel lncRNA regulator of mutant oncoprotein which preferentially prevents AKT1E17K dephosphorylation. Targeting SVIL-AS1 may help to improve the responses to inhibitors of the PI3K-AKT pathway, especially in AKT1E17K mutant tumors.

Long Non-Coding RNAs: Key Regulators of Tumor Epithelial/Mesenchymal Plasticity and Cancer Stemness

Long non-coding RNAs (lncRNAs) are a class of non-coding RNA molecules with transcripts longer than 200 bp, which were initially thought to be noise from genomic transcription without biological function. However, since the discovery of H19 in 1980 and Xist in 1990, increasing evidence has shown that lncRNAs regulate gene expression at epigenetic, transcriptional, and post-transcriptional levels through specific regulatory actions and are involved in the development of cancer and other diseases. Despite many lncRNAs being expressed at lower levels than those of protein-coding genes with less sequence conservation across species, lncRNAs have become an intense area of RNA research. They exert diverse biological functions such as inducing chromatin remodeling, recruiting transcriptional machinery, acting as competitive endogenous RNAs for microRNAs, and modulating protein-protein interactions. Epithelial-mesenchymal transition (EMT) is a developmental process, associated with embryonic development, wound healing, and cancer progression. In the context of oncogenesis, the EMT program is transiently activated and confers migratory/invasive and cancer stem cell (CSC) properties to tumor cells, which are crucial for malignant progression, metastasis, and therapeutic resistance. Accumulating evidence has revealed that lncRNAs play crucial roles in the regulation of tumor epithelial/mesenchymal plasticity (EMP) and cancer stemness. Here, we summarize the emerging roles and molecular mechanisms of lncRNAs in regulating tumor cell EMP and their effects on tumor initiation and progression through regulation of CSCs. We also discuss the potential of lncRNAs as diagnostic and prognostic biomarkers and therapeutic targets.

Nanotherapeutic approaches for delivery of long non-coding RNAs: an updated review with emphasis on cancer

The long noncoding RNAs (lncRNAs) comprise a wide range of RNA species whose length exceeds 200 nucleotides, which regulate the expression of genes and cellular functions in a wide range of organisms. Several diseases, including malignancy, have been associated with lncRNA dysregulation. Due to their functions in cancer development and progression, lncRNAs have emerged as promising biomarkers and therapeutic targets in cancer diagnosis and treatment. Several studies have investigated the anti-cancer properties of lncRNAs; however, only a few lncRNAs have been found to exhibit tumor suppressor properties. Furthermore, their length and poor stability make them difficult to synthesize. Thus, to overcome the instability of lncRNAs, poor specificity, and their off-target effects, researchers have constructed nanocarriers that encapsulate lncRNAs. Recently, translational medicine research has focused on delivering lncRNAs into tumor cells, including cancer cells, through nano-drug delivery systems in vivo. The developed nanocarriers can protect, target, and release lncRNAs under controlled conditions without appreciable adverse effects. To deliver lncRNAs to cancer cells, various nanocarriers, such as exosomes, microbubbles, polymer nanoparticles, 1,2-dioleyl-3-trimethylammoniumpropane chloride nanocarriers, and virus-like particles, have been successfully developed. Despite this, every nanocarrier has its own advantages and disadvantages when it comes to delivering nucleic acids effectively and safely. This article examines the current status of nanocarriers for lncRNA delivery in cancer therapy, focusing on their potential to enhance cancer treatment.