Induction of the long noncoding RNA NBR2 from the bidirectional BRCA1 promoter under hypoxic conditions

LncRNA MALAT1 Expression Regulates Breast Cancer Progression via PI3K/AKT/mTOR Pathway Modulation

Breast cancer is a significant health challenge for women globally, including the Pakistani population. Numerous pathways and small molecules like noncoding ribonucleotides are implicated in breast cancer development and progression. Among these, lncRNAs, have garnered considerable attention due to their role in breast cancer tumorigenesis and metastasis. In the current study involving 52 mammary tumor samples from the Pakistani population, the expression of lncRNA MALAT1 (metastasis associated lung adenocarcinoma transcript 1) was studied via RT-PCR (Real-Time polymerase chain reaction). In addition, PI3K/AKT/mTOR pathway expression was also assessed through RT-PCR and immunohistochemistry in breast cancer patient samples. The study also investigated the cross-talk of lncRNA MALAT1 and PI3K pathway genes by inhibiting it with PI3K inhibitor (LY294002) in MDA-MB-231 cell line. Furthermore, lncRNA MALAT1 was silenced in MDA-MB-231 cells using siRNA to determine its impact on breast cancer proliferation and metastasis. The results revealed an upregulated expression of MALAT1 and PI3K/AKT/mTOR pathway genes in grade II and III breast tissue samples before chemotherapy. The proliferation, growth, and invasion of breast cancer cells were significantly reduced upon MALAT1 silencing in MDA-MB-231. Further, its downregulation substantially reduced the PI3K pathway expression levels at mRNA and protein levels. In conclusion, the current study suggests that MALAT1 could serve as a therapeutic target for breast cancer, underscoring its role in breast cancer proliferation and metastasis. Moreover, the study proposes a mechanism of action of MALAT1, demonstrating that its inhibition can reduce the expression of the PI3K/AKT/mTOR axis. These findings emphasize the potential significance of targeting MALAT1 as a therapeutic strategy for breast cancer, and further exploration of this interaction is warranted to gain deeper insight into the molecular mechanism of this lncRNA.

Brca1 Is Regulated by the Transcription Factor Gata3, and Its Silencing Promotes Neural Differentiation in Retinal Neurons

Previous studies have indicated that Brca1 (Breast cancer suppressor gene 1) plays an important role in neural development and degenerative diseases. However, the bioactivity and regulatory mechanism of Brca1 expression in retinal neurocytes remain unclear. In the present study, our data indicated that Brca1 maintains the state of neuronal precursor cells. Brca1 silencing induces differentiation in 661W cells. Nestin, a marker of precursor cells, was significantly decreased in parallel with Brca1 silencing in 661W cells, whereas Map2 (Microtubule associated protein 2), a marker of differentiated neurons, was significantly increased. Neurite outgrowth was increased by ~4.0-fold in Brca1-silenced cells. Moreover, DNA affinity purification assays and ChIP assays demonstrated that Gata3 (GATA binding protein 3) regulates Brca1 transcription in 661W cells. Silencing or overexpressing Gata3 could significantly regulate the expression of Brca1 and affect its promoter inducibility. Furthermore, the expression of Gata3 generally occurred in parallel with that of Brca1 in developing mouse retinas. Both Gata3 and Brca1 are expressed in the neonatal mouse retina but are developmentally silenced with age. Exogenous Gata3 significantly inhibited neural activity by decreasing synaptophysin and neurite outgrowth. Thus, this study demonstrated that Brca1 is transcriptionally regulated by Gata3. Brca1/Gata3 silencing is involved in neuronal differentiation and maturation.

Long Non-Coding RNA Neighbor of BRCA1 Gene 2: A Crucial Regulator in Cancer Biology

Long non-coding RNAs (lncRNAs) are involved in fundamental biochemical and cellular processes. The neighbor of BRCA1 gene 2 (NBR2) is a long intergenic non-coding RNA (lincRNA) whose gene locus is adjacent to the tumor suppressor gene breast cancer susceptibility gene 1 (BRCA1). In human cancers, NBR2 expression is dysregulated and correlates with clinical outcomes. Moreover, NBR2 is crucial for glucose metabolism and affects the proliferation, survival, metastasis, and therapeutic resistance in different types of cancer. Here, we review the precise molecular mechanisms underlying NBR2-induced changes in cancer. In addition, the potential application of NBR2 in the diagnosis and treatment of cancer is also discussed, as well as the challenges of exploiting NBR2 for cancer intervention.

Long intergenic non-protein coding RNA 00475 silencing acts as a tumor suppressor in glioma under hypoxic condition by impairing microRNA-449b-5p-dependent AGAP2 up-regulation

Objective

Long non-coding RNAs have been demonstrated to be involved in the progression of a variety of cancers, including glioma. Through microarray analyses, long intergenic non-protein coding RNA 00475 (LINC00475) was identified in the glioma development. However, its potential role remains incompletely understood. This study aimed to elucidate the effect of LINC00475 on the development of glioma under hypoxic conditions.

Methods

Glioma cells underwent hypoxic treatment and were collected. The functional role of LINC00475 and AGAP2 in glioma was determined using ectopic expression, depletion, and reporter assay experiments. Then, the expression of LINC00475, microRNA (miR)-449b-5p, AGAP2, FAK, and HIF-1α was determined. In addition, cell migration and invasion were examined. Finally, a tumor xenograft was carried out in nude mice to explore the role of LINC00475 on oxidation in vivo.

Results

LINC00475 was identified to be overexpressed in hypoxic glioma samples, which was further observed to bind to and down-regulate miR-449b-5p, and negatively targeted AGAP2. Moreover, we also revealed a positive correlation between LINC00475 and AGAP2 expression in glioma. In addition, silencing of LINC00475 decreased the extent of FAK phosphorylation and reduced the expression of HIF-1α and AGAP2. It was also observed that LINC00475 silencing suppressed glioma cell proliferation, migration, and invasion, and promoted cell apoptosis. Moreover, oxidation of nude mice was promoted by LINC00475 silencing.

Conclusion

Taken together, LINC00475 silencing exerted an inhibitory effect on glioma under hypoxic conditions by down-regulating AGAP2 via up-regulation of miR-449b-5p.

LncRNA NBR2 inhibits epithelial-mesenchymal transition by regulating Notch1 signaling in osteosarcoma cells

Long noncoding RNAs (lncRNAs) have been identified to have increasingly important roles in tumorigenesis, and they may serve as novel biomarkers for cancer therapy. Recent studies have demonstrated that lncRNA NBR2 (neighbor of BRCA1 gene 2), a novel identified lncRNA, is decreased in several cancers; however, the role of NBR2 in the development of osteosarcoma has not been elucidated. In our study, we found that NBR2 expression was downregulated in osteosarcoma tissues, and osteosarcoma cases with lower NBR2 expression exhibited a shorter overall survival time compared with those with higher NBR2 expression. NBR2 overexpression inhibited osteosarcoma cell proliferation, invasion, and migration but did not increase apoptosis. Furthermore, RNA-binding protein immunoprecipitation assays confirmed that NBR2 directly binds to Notch1 protein. Furthermore, overexpression of Notch1 in NBR2-overexpressing osteosarcoma cells reversed the effects of NBR2 on cell proliferation, invasion, migration, and epithelial-mesenchymal transition. The in vivo results showed that NBR2 overexpression inhibited tumor growth in nude mice that were inoculated with osteosarcoma cells. NBR2 overexpression also suppressed the messenger RNA (mRNA) expression of Notch1, N-cadherin, and vimentin and increased the mRNA expression of E-cadherin in the tumor tissues. These data indicated that NBR2 served as a tumor suppressor gene in osteosarcoma and inhibited osteosarcoma cell proliferation, invasion, and migration. The current study provides a novel insight and treatment strategy for osteosarcoma.

The Many Faces of Long Noncoding RNAs in Cancer

SIGNIFICANCE

The emerging connections between an increasing number of long noncoding RNAs (lncRNAs) and oncogenic hallmarks provide a new twist to tumor complexity. Recent Advances: In the present review, we highlight specific lncRNAs that have been studied in relation to tumorigenesis, either as participants in the neoplastic process or as markers of pathway activity or drug response. These transcripts are typically deregulated by oncogenic or tumor-suppressing signals or respond to microenvironmental conditions such as hypoxia.

CRITICAL ISSUES

Among these transcripts are lncRNAs sufficiently divergent between mouse and human genomes that may contribute to biological differences between species.

FUTURE DIRECTIONS

From a translational standpoint, knowledge about primate-specific lncRNAs may help explain the reason behind the failure to reproduce the results from mouse cancer models in human cell-based systems. Antioxid. Redox Signal. 29, 922-935.

The hypoxia-responsive long non-coding RNAs may impact on the tumor biology and subsequent management of breast cancer

Long non-coding RNAs (lncRNAs) are DNA transcripts longer than 200 nucleotides without protein-coding potential. As they are key regulators of gene expression at chromatic, transcriptional and posttranscriptional level, they play important role in various biological and pathological processes. Dysregulation of lncRNAs has been observed in several diseases including cancer. Breast cancer is heterogeneous disease with many molecular subtypes specific in different prognosis and treatment responses. Hypoxia, a common micro-environmental feature of rapidly growing tumour is associated with metastases, recurrences and resistance to therapy. Aberrant expression of hypoxia related lncRNAs significantly correlates with poor outcomes in cancer patients, as the lncRNAs play an important regulatory role in the breast cancer-cell survival. Thus, a better understanding of lncRNAs role in the hypoxic conditions of breast cancer is crucial for precise understanding of the tumorigenesis, disease features and poor clinical outcome, especially in highly aggressive breast cancer subtypes (HER2-positive and triple-negative types). Moreover, lncRNAs may represent tumour marker predicting prognosis and therapeutic targets improving precise and personalized therapy for better patient´s survival. In this review, we summarize the recent information on lncRNAs in breast cancer with special focus on the hypoxia-responsive lncRNAs and their potential impact on the prognosis, therapy algorithms and individual outcomes. Presented data helps in better understanding of the specific mechanisms predicting new therapeutic agents and strategies for the pharmacological intervention.

Long non-coding RNA and tumor hypoxia: new players ushered toward an old arena

Hypoxia is a classic feature of the tumor microenvironment with a profound impact on cancer progression and therapeutic response. Activation of complex hypoxia pathways orchestrated by the transcription factor HIF (hypoxia-inducible factor) contributes to aggressive phenotypes and metastasis in numerous cancers. Over the past few decades, exponentially growing research indicated the importance of the non-coding genome in hypoxic tumor regions. Recently, key roles of long non coding RNAs (lncRNAs) in hypoxia-driven cancer progression have begun to emerge. These hypoxia-responsive lncRNAs (HRLs) play pivotal roles in regulating hypoxic gene expression at chromatic, transcriptional, and post-transcriptional levels by acting as effectors of the indirect response to HIF or direct modulators of the HIF-transcriptional cascade. Notably, the aberrant expression of HRLs significantly correlates with poor outcomes in cancer patients, showing promise for future utility as a tumor marker or therapeutic target. Here we address the latest advances made toward understanding the functional relevance of HRLs, the involvement of these transcripts in hypoxia response and the underlying action mechanisms, highlighting their specific roles in HIF-1 signaling regulation and hypoxia-associated malignant transformation.