Research progresses in roles of LncRNA and its relationships with breast cancer

The roles of long noncoding RNAs in breast cancer metastasis

Breast cancer is the most significant threat to female health. Breast cancer metastasis is the major cause of mortality in breast cancer patients. To fully unravel the molecular mechanisms that underlie the breast cancer cell metastasis is critical for developing strategies to improve survival and prognosis in breast cancer patients. Recent studies have revealed that the long noncoding RNAs (lncRNAs) are involved in breast cancer metastasis through a variety of molecule mechanisms, though the precise functional details of these lncRNAs are yet to be clarified. In the present review, we focus on the functions of lncRNAs in breast cancer invasion and metastasis, with particular emphasis on the functional properties, the regulatory factors, the therapeutic promise, as well as the future challenges in studying these lncRNA.

Overexpression of long non-coding RNA MCM3AP-AS1 in breast cancer tissues compared to adjacent non-tumour tissues

BACKGROUND

Altered expression of several long non-coding RNAs (lncRNAs) has been described in numerous malignancies, including breast cancer, and some may have a role in carcinogenesis. We hypothesised differences in the expression of lncRNA MCM3AP-AS1 in breast cancer tissues compared to nearby healthy tissues and potential links with clinical features.

METHODS

We tested our hypothesis in 102 pairs of breast cancer tumours and adjacent non-tumour tissues from female patients. After RNA extraction, cDNA synthesis was performed for all specimens. The differential gene expression was assessed using Quantitative Real-Time PCR Technique.

RESULTS

There was a significant overexpression of the lncRNAs in tumour tissues as compared with their adjacent non-tumour tissues (P < 0.001). Expression was significantly linked with the tumour oestrogen receptor expression (P = 0.023) and tumour progesterone receptor expression (P < 0.001). ROC analysis showed an AUC of 0.67 (95% CI 0.60-0.75) (P < 0.001) with sensitivity and specificity of 58% and 76%, respectively.

CONCLUSION

The lncRNA MCM3AP-AS1 may be a novel breast cancer lncRNA with high expression levels in breast cancer patients' tissue. Further investigations are needed to confirm its uses as a potential molecular marker and therapeutic target.

Long Intergenic Non-Coding RNA LINC00922 Aggravates the Malignant Phenotype of Breast Cancer by Regulating the microRNA-424-5p/BDNF Axis

PURPOSE

Long intergenic non-coding RNA 922 (LINC00922) plays a critical role in the progression of lung cancer. In this study, we aimed to quantify LINC00922 expression in breast cancer and determine its influence on the malignant behavior of breast cancer cells in vitro and in vivo. We also investigated the mechanism by which LINC00922 affects the progression of breast cancer.

MATERIALS AND METHODS

Reverse transcription-quantitative polymerase chain reaction was performed to quantify LINC00922 expression in breast cancer tissues and cell lines. The cell counting kit-8 assay, flow cytometry, Transwell migration and invasion assays, and tumor model assays were performed to determine the effects of LINC00922 deficiency on breast cancer cell proliferation, apoptosis, migration and invasion in vitro, and tumor growth in vivo, respectively. Furthermore, bioinformatics analysis was performed to predict the potential target microRNA of LINC00922. The prediction was further evaluated using luciferase reporter and RNA immunoprecipitation assays.

RESULTS

LINC00922 was clearly overexpressed in breast cancer tissues and cell lines. LINC00922 depletion restricted breast cancer cell proliferation, migration, and invasion but induced cell apoptosis in vitro. Additionally, its knockdown evidently repressed tumor growth of breast cancer cells in vivo. Mechanistically, LINC00922 was demonstrated to serve as a molecular sponge for miR-424-5p in breast cancer cells. Furthermore, brain-derived neurotrophic factor (BDNF) was verified as a direct target of miR-424-5p in breast cancer cells, and BDNF expression was found to be positively regulated by LINC00922 through sponging miR-425-5p. Rescue experiments further revealed that the influences on breast cancer cell proliferation, apoptosis, migration, and invasion induced by LINC00922 silencing were abrogated by increasing the output of the miR-424-5p/BDNF axis.

CONCLUSION

The LINC00922/miR-424-5p/BDNF pathway is implicated in the acceleration of the malignant behavior of breast cancer cells. These findings suggest that this pathway is a promising novel molecular target in breast cancer therapy.

The crosstalk between lncRNAs and the Hippo signalling pathway in cancer progression

LncRNAs play a pivotal role in the regulation of epigenetic modification, cell cycle, differentiation, proliferation, migration and other physiological activities. In particular, considerable studies have shown that the aberrant expression and dysregulation of lncRNAs are widely implicated in cancer initiation and progression by acting as tumour promoters or suppressors. Hippo signalling pathway has attracted researchers’ attention as one of the critical cancer‐related pathways in recent years. Increasing evidences have demonstrated that lncRNAs could interact with Hippo cascade and thereby contribute to acquisition of multiple malignant hallmarks, including proliferation, metastasis, relapse and resistance to anti‐cancer treatment. Specifically, Hippo signalling pathway is reported to modulate or be regulated by widespread lncRNAs. Intriguingly, certain lncRNAs could form a reciprocal feedback loop with Hippo signalling. More speculatively, lncRNAs related to Hippo pathway have been poised to become important putative biomarkers and therapeutic targets in human cancers. Herein, this review focuses on the crosstalk between lncRNAs and Hippo pathway in carcinogenesis, summarizes the comprehensive role of Hippo‐related lncRNAs in tumour progression and depicts their clinical diagnostic, prognostic or therapeutic potentials in tumours.

Long noncoding RNAs and their link to cancer

The central dogma of molecular biology, developed from the study of simple organisms such as Escherichia coli, has up until recently been that RNA functions mainly as an information intermediate between a DNA sequence (gene), localized in the cell nucleus, serving as a template for the transcription of messenger RNAs, which in turn translocate into the cytoplasm and act as blueprints for the translation of their encoded proteins. There are a number of classes of non-protein coding RNAs (ncRNAs) which are essential for gene expression to function. The specific number of ncRNAs within the human genome is unknown. ncRNAs are classified on the basis of their size. Transcripts shorter than 200 nucleotides, referred to as ncRNAs, which group includes miRNAs, siRNAs, piRNAs, etc, have been extensively studied. Whilst transcripts with a length ranging between 200 nt up to 100 kilobases, referred to as lncRNAs, make up the second group, and are recently receiving growing concerns. LncRNAs play important roles in a variety of biological processes, regulating physiological functions of organisms, including epigenetic control of gene regulation, transcription and post-transcription, affecting various aspects of cellular homeostasis, including proliferation, survival, migration and genomic stability. LncRNAs are also capable of tuning gene expression and impact cellular signalling cascades, play crucial roles in promoter-specific gene regulation, and X-chromosome inactivation. Furthermore, it has been reported that lncRNAs interact with DNA, RNA, and/or protein molecules, and regulate chromatin organisation, transcriptional and post-transcriptional regulation. Consequently, they are differentially expressed in tumours, and they are directly linked to the transformation of healthy cells into tumour cells. As a result of their key functions in a wide range of biological processes, lncRNAs are becoming rising stars in biology and medicine, possessing potential active roles in various oncologic diseases, representing a gold mine of potential new biomarkers and drug targets.

Long noncoding RNA HOST2, working as a competitive endogenous RNA, promotes STAT3-mediated cell proliferation and migration via decoying of let-7b in triple-negative breast cancer

Background

Human ovarian cancer specific transcript 2 (HOST2) is a long non-coding RNA (lncRNA) reported to be specifically high expressed in human ovarian cancer. However, the mechanism that how HOST2 regulates triple negative breast cancer (TNBC) need to be explored.

Methods

In this study, expression of HOST2 was determined in 40 TNBC patients and matched non-cancerous tissues by qRT-PCR and in situ hybridization (ISH) assay. The biological functions of HOST2 was measured by losing features. The effect of HOST2 on viability, proliferation and migration was evaluated by MTT, colony formation assay, EDU analysis, transwell invasion assay and nude mouse xenograft model. Fluorescence in situ hybridization (FISH), Luciferase report assay, RNA immunoprecipitation (RIP) assay and Western blot were fulfilled to measure molecular mechanisms.

Results

The results showed that HOST2 was up-regulated in BC tissues and cell lines. Clinical outcome analysis demonstrated that high expression of HOST2 was associated with poor prognosis of TNBC patients. Functional experiments illustrated that knockdown of HOST2 significantly suppressed TNBC cell proliferation and migration. Western blot assays, qRT-PCR assays, RIP assays and luciferase reporter assays revealed that HOST2 regulated STAT3 via crosstalk with let-7b. Depression of HOST2 suppressed STAT3-mediated proliferation and migration in TNBC cells. HOST2 could function as a decoy of let-7b to depress expression of STAT3.

Conclusions

HOST2 could function as a oncogene and promoted STAT3-mediated proliferation and migration through acting as a competing endogenous RNA, which might act as a potential biomarker for TNBC patients.

Long noncoding RNA LINC00963 promotes breast cancer progression by functioning as a molecular sponge for microRNA-625 and thereby upregulating HMGA1

Extensive research has shown that LINC00963 is aberrantly expressed in human cancers, and that dysregulation of LINC00963 is implicated in the initiation and progression of human cancers. The expression and functions of LINC00963 in breast cancer are still unclear. Our aims were to measure the expression of LINC00963 in breast cancer, determine its effects on malignant behaviors of tumor cells, and uncover the molecular events underlying the actions of LINC00963 in breast cancer. Herein, LINC00963 was found to be overexpressed in breast cancer samples, and its overexpression was correlated with lymph node metastasis, TNM stage and differentiation grade. Patients with breast cancer harboring higher LINC00963 expression showed shorter overall survival than did the patients with lower LINC00963 expression. Functional experiments revealed that depletion of LINC00963 inhibited breast cancer cell proliferation, migration, and invasion and facilitated apoptosis in vitro and impaired tumor growth in vivo. Mechanism investigation revealed that LINC00963 can interact with microRNA-625 (miR-625). LINC00963 worked as a competitive endogenous RNA for miR-625 to weaken the suppressive effect of miR-625 on high mobility group AT-hook 1 (HMGA1) in breast cancer cells. Furthermore, miR-625 inhibition and HMGA1 restoration both abrogated the effects of LINC00963 silencing on breast cancer cells. Our findings indicate that the LINC00963-miR-625-HMGA1 pathway plays an important role in the malignancy of breast cancer in vitro and in vivo. Hence, targeting this pathway may be a novel strategy against breast cancer.

lncRNA TCL6 correlates with immune cell infiltration and indicates worse survival in breast cancer

BACKGROUND

Long non-coding RNA (lncRNA) T-cell leukemia/lymphoma 6 (TCL6) has been reported as a potential tumor suppressor. However, its expression and function in breast cancer remain unknown. This study was performed to investigate the expression of lncRNA TCL6 in breast cancer and its clinical significance.

METHODS

The survival and clinical molecular roles of TCL6 in breast cancer were analyzed. The underlying mechanism modulated by TCL6 and its correlation with immune-infiltrating cells were investigated. Gene Expression Omnibus (GEO) datasets were further used to confirm the prognostic role of TCL6.

RESULTS

TCL6 low expression was not correlated with age, clinical stage, T stage, lymph node metastasis, distant metastasis, human epidermal growth factor 2 status, but was associated with estrogen receptor and progesterone receptor (PR) status and was an independent factor for worse survival (HR 1.876, P = 0.016). Specifically, low TCL6 expression correlated with worse prognosis in PR-negative patients. TCL6 could predict worse survival in luminal B breast cancer based on intrinsic subtypes. Immune-related pathways such as Janus kinase-signal transducer of activators of transcription were regulated by TCL6. Further finding revealed that TCL6 correlated with immune infiltrating cells such as B cells (r = 0.25, P < 0.001), CD8+ T cells (r = 0.23, P < 0.001), CD4+ T cells (r = 0.25, P < 0.001), neutrophils (r = 0.21, P < 0.001), and dendritic cells (r = 0.27, P < 0.001). TCL6 was also positively correlated with tumor-infiltrating lymphocytes infiltration and PD-1, PD-L1, PD-L2, and CTLA-4 immune checkpoint molecules (P < 0.001).

CONCLUSION

Our findings suggest that lncRNA TCL6 correlates with immune infiltration and may act as a useful prognostic molecular marker in breast cancer.

lncRNA PCAT-1 interacting with FZD6 contributes to the malignancy of acute myeloid leukemia cells through activating Wnt/β-catenin signaling pathway

Accumulating evidence has suggested the involvement of long noncoding RNAs (lncRNAs) on the acute myeloid leukemia (AML). Therefore, this study aimed to investigate the unknown function of lncRNA Prostate cancer-associated transcript-1 (PCAT-1) in AML cells. Our data found that PCAT-1 was highly expressed in AML-M1/2 and AML-M3 patients than normal controls and its expression was significantly up-regulated in AML cell lines Kasumi-6 and HL-60. The functional experiments demonstrated that knockdown of PCAT-1 remarkably inhibited proliferation, arrested cell cycle progression and triggered apoptosis of AML cells. Mechanistically, we revealed that PCAT-1 could directly interact with FZD6 protein to regulate its stability. Overexpression of FZD6 partly abolished the effects of PCAT-1 silencing on AML cells. Our integrated experiments then suggested that PCAT-1 could activate the Wnt/β-catenin signaling pathway in an FZD6-dependent manner. Taken together, the present study indicated that PCAT-1 interacting with FZD6 to activate Wnt/β-catenin signaling, which may play an important role in the pathogenesis of AML.

The prognostic value of long noncoding RNA SNHG16 on clinical outcomes in human cancers: a systematic review and meta-analysis

BACKGROUND

Cancer has been a worldwide health problem with a high risk of morbidity and mortality, however ideal biomarkers for effective screening and diagnosis of cancer patients are still lacking. Small nucleolar RNA host gene 16 (SNHG16) is newly identified lncRNA with abnormal expression in several human malignancies. However, its prognostic value remains controversial. This meta-analysis aimed to synthesize available data to clarify the association between SNHG16 expression levels and clinical prognosis value in multiple cancers.

METHODS

Extensive literature retrieval was conducted to identify eligible studies, and data regarding SNHG16 expression levels on survival outcomes and clinicopathological features were extracted and pooled for calculation of the hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (CIs). Forest plots were applied to show the association between SNHG16 expression and survival prognosis. Additionally, The Cancer Genome Atlas (TCGA) dataset was screened and extracted for validation of the results in this meta-analysis.

RESULTS

A total of eight studies comprising 568 patients were included in the final meta-analysis according to the inclusion and exclusion criteria. In the pooled analysis, high SNHG16 expression significantly predicted worse overall survival (OS) in various cancers (HR = 1.87, 95% CI 1.54-2.26, P < 0.001), and recurrence-free survival (RFS) in bladder cancer (HR = 1.68, 95% CI 1.01-2.79, P = 0.045). Meanwhile, stratified analyses revealed that the survival analysis method, tumor type, sample size, and cut-off value did not alter the predictive value of SNHG16 for OS in cancer patients. In addition, compared to the low SNHG16 expression group, patients with high SNHG16 expression were more prone to worse clinicopathological features, such as larger tumor size, advanced clinical stage, lymph node metastasis (LNM) and distant metastasis (DM). Exploration of TCGA dataset further validated that the upregulated SNHG16 expression predicted unfavorable OS and disease-free survival (DFS) in cancer patients.

CONCLUSIONS

The present study implicated that aberrant expression of lncRNA SNHG16 was strongly associated with clinical survival outcomes in various cancers, and therefore might serve as a promising biomarker for predicting prognosis of human cancers.

Potential of epigenetic events in human thyroid cancer

Thyroid cancer remains the highest prevailing endocrine malignancy, and its incidence rate has progressively increased in the previous years. Above 95% of thyroid tumor are follicular cells types of carcinoma in which are considered invasive type of tumor. The pathogenesis and molecular mechanism of thyroid tumors are yet remains elucidated, in spite of activating RET, RAS and BRAF carcinogenesis have been well introduced. Nemours molecular alterations have been defined and have revealed promise for their diagnostic, prognostic and therapeutic capacity but still need further confirmation. Among different types of mechanisms, the current article reviews the importance of epigenetic modifications in thyroid cancer. Increasing data from previous reports demonstrate that acquired epigenetic abnormalities together with genetic changes plays an important role in alteration of gene expression patterns. Aberrant DNA methylation has been well known in the CpG regions and profile of microRNAs (mi-RNAs) expression also involved in cancer development. In addition, the gene expression through epigenetic control contribution to thyroid cancer is analyzed and it is semi considered in the clinic. However the epigenetic of the thyroid cancer is yet remains in its early stages, and it carries encouraging potential thyroid cancer detections in its early stages, assessment of prognosis and targeted cancer treatment.

Long noncoding RNA CASC11 promotes osteosarcoma metastasis by suppressing degradation of snail mRNA

Osteosarcoma (OS) is the most common primary bone tumor in adolescents. Dysregulation of long noncoding RNAs (lncRNAs) is associated with the cancer progression, of which cancer susceptibility candidate 11 (CASC11) has been indicated as an oncogene in several human cancers. However, the underlying mechanisms by which CASC11 contributes to OS metastasis remain undetermined. Here, we found that CASC11 expression in OS tissues was markedly higher than that in noncancerous tissues. Clinical association analysis revealed that high CASC11 expression correlated with clinical stage, distant metastasis and poor prognosis of OS patients. Gain- and loss-of-function assays demonstrated that CASC11 promoted migration, invasion, epithelial-mesenchymal transition (EMT) and metastasis of OS cells in vitro and in vivo. CASC11 associated with the EMT inducer Snail mRNA and increased its stability. Association of CASC11 with Snail mRNA blocked the repressing effect of miR-122, miR-145, miR-211, miR-34a and miR-137 on Snail. Moreover, CASC11-specific siRNAs significantly inhibit tumor metastasis in vivo. Taken together, our findings suggest that CASC11 may be a candidate prognostic biomarker and a novel therapeutic target for OS.