CCAT1 promotes triple-negative breast cancer progression by suppressing miR-218/ZFX signaling

miR-218-5p and doxorubicin combination enhances anticancer activity in breast cancer cells through Parkin-dependent mitophagy inhibition

Breast Cancer (BC) is one of the most common tumours, and is known for its ability to develop resistance to chemotherapeutic treatments. Autophagy has been linked to chemotherapeutic response in several types of cancer, highlighting its contribution to this process. However, the role of mitophagy, a selective form of autophagy responsible for damaged mitochondria degradation, in the response to therapies in BC is still unclear. In order to address this point, we analysed the role of mitophagy in the treatment of the most common anticancer drug, doxorubicin (DXR), in different models of BC, such as a luminal A subtype-BC cell line MCF7 cells, cultured in 2-Dimension (2D) or in 3-Dimension (3D), and the triple negative BC (TNBC) cell line MDA-MB-231. Through a microarray analysis, we identified a relationship between mitophagy gene expressions related to the canonical PINK1/Parkin-mediated pathway and DXR treatment in BC cells. Afterwards, we demonstrated that the PINK1/Parkin-dependent mitophagy is indeed induced following DXR treatment and that exogenous expression of a small non-coding RNA, the miRNA-218-5p, known to target mRNA of Parkin, was sufficient to inhibit the DXR-mediated mitophagy in MCF7 and in MDA-MB-231 cells, thereby increasing their sensitivity to DXR. Considering the current challenges involved in BC refractory to treatment, our work could provide a promising approach to prevent tumour resistance and recurrence, potentially leading to the development of an innovative approach to combine mitophagy inhibition and chemotherapy.

Modulating the acetylation of α-tubulin by LncRNAs and microRNAs helps in the progression of cancer

Malignant tumor cells go through morphological and gene expression alterations, including rearrangement of cytoskeleton proteins that promote invasion and metastasis. Microtubules form a major cytoskeleton component that plays a significant role in regulating multiple cellular activities and function depending on the presence of posttranslational modification (PTM). Acetylation is a type of PTM that generally occurs in the lysine 40 region of α-tubulin and is known to be critically associated with cancer metastasis. Current evidence demonstrates that noncoding RNAs, such as long noncoding RNA (lncRNA) and microRNA (or miRNA), which are correlated with gene regulation modulate the expression of acetylated tubulin in the development and metastasis of cancer. This review provides an overview about the role of lncRNA and miRNA in regulation of tubulin acetylation in various types of cancer.

Expression and clinical significance of hypoxia-induced long non-coding RNA TCONS_I2_00001955 in breast cancer

BACKGROUND

Long non-coding RNAs (lncRNAs) have been found to play important roles in occurrence, development, and metastasis of various tumors. We aimed to screen long non-coding RNAs (lncRNAs) that promote invasion and metastasis of breast cancer cells under hypoxia, and investigate the relationship between lncRNA expression and clinicopathological features and prognosis in invasive breast cancer.

METHODS

LncRNA microarray was used to screen the differentially expressed lncRNAs in MCF7, MDA-MB-231, and SKBR3 breast cancer cell lines cultured under normoxia and hypoxia, respectively. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to verify the microarray results. CCK8 and Transwell experiments were performed to identify the lncRNA that promote proliferation, migration, and invasion of breast cancer cells. Expression of the lncRNA and HIF-1α in invasive breast cancer was detected by RNAscope and immunohistochemistry, respectively. Correlation between the lncRNA expression and baseline characteristics was analyzed. Prognostic value of the lncRNA was evaluated using univariate and multivariate Cox regression.

RESULTS

Expression of lncRNA TCONS_I2_00001955 in all the three breast cancer cells was increased under hypoxia. Overexpression of TCONS_I2_00001955 significantly enhanced proliferation, migration, and invasion of SKBR3 cells. Positive expression of TCONS_I2_00001955 was associated with recurrence, metastasis, and high expression of HIF-1α (P < 0.05), and it was an independent risk factor for poor disease-free survival of breast cancer.

CONCLUSION

Hypoxia-induced lncRNA TCONS_I2_00001955 was associated with aggressive feature and poor prognosis of breast cancer.

LINC02532 by Mediating miR-541-3p/HMGA1 Axis Exerts a Tumor Promoter in Breast cancer

The newly discovered LINC02532 is abnormally expressed in a variety of cancers and promotes cancer progression. The research proposed to discover the biological and molecular mechanisms of LINC02532 in breast cancer (BCa). In the resected BCa tissue samples and adjacent normal tissues, LINC02532, miR-541-3p, and High Mobility Group A1 (HMGA1) levels were determined. Cell function experiments were carried out on the premise of cell transfection with relevant plasmids. Based on that, the influence of LINC02532, miR-541-3p, and HMGA1 on MCF-7 cell activities (proliferation, migration, invasion, cell cycle, and apoptosis) was determined, as well as on EMT. Additionally, animal experiments were allowed to support cell experimental conclusions on LINC02532. Finally, the mechanistic network of LINC02532, miR-541-3p, and HMGA1 was identified. It was BCa tissues highly expressing LINC02532 and HMGA1, while lowly expressing miR-541-3p. Functionally, LINC02532 depletion repressed the activities and EMT process of MCF-7 cells. Silencing LINC02532 delayed tumor growth in mice. In terms of mechanism, LINC02532 mainly existed in the cytoplasm and could mediate HMGA1 expression by absorbing miR-541-3p. The findings offer new insights into the molecular mechanisms of LINC02532 in BCa and, more importantly, new strategies for the clinical treatment of BCa.

A conserved ZFX/WNT3 axis modulates the growth and imatinib response of chronic myeloid leukemia stem/progenitor cells

BACKGROUND

Zinc finger protein X-linked (ZFX) has been shown to promote the growth of tumor cells, including leukemic cells. However, the role of ZFX in the growth and drug response of chronic myeloid leukemia (CML) stem/progenitor cells remains unclear.

METHODS

Real-time quantitative PCR (RT-qPCR) and immunofluorescence were used to analyze the expression of ZFX and WNT3 in CML CD34+ cells compared with normal control cells. Short hairpin RNAs (shRNAs) and clustered regularly interspaced short palindromic repeats/dead CRISPR-associated protein 9 (CRISPR/dCas9) technologies were used to study the role of ZFX in growth and drug response of CML cells. Microarray data were generated to compare ZFX-silenced CML CD34+ cells with their controls. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were performed to study the molecular mechanisms of ZFX to regulate WNT3 expression. RT-qPCR and western blotting were used to study the effect of ZFX on β-catenin signaling.

RESULTS

We showed that ZFX expression was significantly higher in CML CD34+ cells than in control cells. Overexpression and gene silencing experiments indicated that ZFX promoted the in vitro growth of CML cells, conferred imatinib mesylate (IM) resistance to these cells, and enhanced BCR/ABL-induced malignant transformation. Microarray data and subsequent validation revealed that WNT3 transcription was conservatively regulated by ZFX. WNT3 was highly expressed in CML CD34+ cells, and WNT3 regulated the growth and IM response of these cells similarly to ZFX. Moreover, WNT3 overexpression partially rescued ZFX silencing-induced growth inhibition and IM hypersensitivity. ZFX silencing decreased WNT3/β-catenin signaling, including c-MYC and CCND1 expression.

CONCLUSION

The present study identified a novel ZFX/WNT3 axis that modulates the growth and IM response of CML stem/progenitor cells.

Long non-coding RNA colon cancer-associated transcript 1-Vimentin axis promoting the migration and invasion of HeLa cells

BACKGROUND

Long non-coding RNA colon cancer-associated transcript 1 (CCAT1) is involved in transforming multiple cancers into malignant cancer types. Previous studies underlining the mechanisms of the functions of CCAT1 primarily focused on its decoy for miRNAs (micro RNAs). However, the regulatory mechanism of CCAT1-protein interaction associated with tumor metastasis is still largely unknown. The present study aimed to identify proteome-wide CCAT1 partners and explored the CCAT1-protein interaction mediated tumor metastasis.

METHODS

CCAT1-proteins complexes were purified and identified using RNA antisense purification coupled with the mass spectrometry (RAP-MS) method. The database for annotation, visualization, and integrated discovery and database for eukaryotic RNA binding proteins (EuRBPDB) websites were used to bioinformatic analyzing CCAT1 binding proteins. RNA pull-down and RNA immunoprecipitation were used to validate CCAT1-Vimentin interaction. Transwell assay was used to evaluate the migration and invasion abilities of HeLa cells.

RESULTS

RAP-MS method worked well by culturing cells with nucleoside analog 4-thiouridine, and cross-linking was performed using 365 nm wavelength ultraviolet. There were 631 proteins identified, out of which about 60% were RNA binding proteins recorded by the EuRBPDB database. Vimentin was one of the CCAT1 binding proteins and participated in the tumor metastasis pathway. Knocked down vimetin ( VIM ) and rescued the downregulation by overexpressing CCAT1 demonstrated that CCAT1 could enhance tumor migration and invasion abilities by stabilizing Vimentin protein.

CONCLUSION

CCAT1 may bind with and stabilize Vimentin protein, thus enhancing cancer cell migration and invasion abilities.

Role of long non-coding RNAs and TGF-β signaling in the regulation of breast cancer pathogenesis and therapeutic targets

The cytokine known as transforming growth factor (TGF) is essential for cell development, differentiation, and apoptosis in BC. TGF-β dysregulation can either promote or inhibit tumor development, and it is a key signaling pathway in BC spread. A recently identified family of ncRNAs known as lncRNAs has received a great deal of effort and is an important regulator of many cellular processes, including transcription of genes, chromatin remodeling, progression of the cell cycle, and posttranscriptional processing. Furthermore, both TGF-β signaling and lncRNAs serve as important early-stage biomarkers for BC diagnosis and prognosis and also play a significant role in BC drug resistance. According to recent studies, lncRNAs can regulate TGF-β by modulating its cofactors in BC. However, the particular functions of lncRNAs and the TGF-β pathway in controlling BC progression are not well understood yet. This review explores the lncRNAs' functional properties in BC as tumor suppressors or oncogenes in the regulation of genes, with a focus on dysregulated TGF-β signaling. Further, we emphasize the functional roles of lncRNAs and TGF-β pathway in the progression of BC to discover new treatment strategies and better comprehend the fundamental cellular pathways.

Tissue-Specific Tumour Suppressor and Oncogenic Activities of the Polycomb-like Protein MTF2

The Polycomb repressive complex 2 (PRC2) is a conserved chromatin-remodelling complex that catalyses the trimethylation of histone H3 lysine 27 (H3K27me3), a mark associated with gene silencing. PRC2 regulates chromatin structure and gene expression during organismal and tissue development and tissue homeostasis in the adult. PRC2 core subunits are associated with various accessory proteins that modulate its function and recruitment to target genes. The multimeric composition of accessory proteins results in two distinct variant complexes of PRC2, PRC2.1 and PRC2.2. Metal response element-binding transcription factor 2 (MTF2) is one of the Polycomb-like proteins (PCLs) that forms the PRC2.1 complex. MTF2 is highly conserved, and as an accessory subunit of PRC2, it has important roles in embryonic stem cell self-renewal and differentiation, development, and cancer progression. Here, we review the impact of MTF2 in PRC2 complex assembly, catalytic activity, and spatiotemporal function. The emerging paradoxical evidence suggesting that MTF2 has divergent roles as either a tumour suppressor or an oncogene in different tissues merits further investigations. Altogether, our review illuminates the context-dependent roles of MTF2 in Polycomb group (PcG) protein-mediated epigenetic regulation. Its impact on disease paves the way for a deeper understanding of epigenetic regulation and novel therapeutic strategies.

Exploiting Long Non-Coding RNAs and Circular RNAs as Pharmacological Targets in Triple-Negative Breast Cancer Treatment

Breast cancer is one of the most frequent causes of cancer death among women worldwide. In particular, triple-negative breast cancer (TNBC) represents the most aggressive breast cancer subtype because it is characterized by the absence of molecular targets, thus making it an orphan type of malignancy. The discovery of new molecular druggable targets is mandatory to improve treatment success. In that context, non-coding RNAs represent an opportunity for modulation of cancer. They are RNA molecules with apparently no protein coding potential, which have been already demonstrated to play pivotal roles within cells, being involved in different processes, such as proliferation, cell cycle regulation, apoptosis, migration, and diseases, including cancer. Accordingly, they could be used as targets for future TNBC personalized therapy. Moreover, the peculiar characteristics of non-coding RNAs make them reliable biomarkers to monitor cancer treatment, thus, to monitor recurrence or chemoresistance, which are the most challenging aspects in TNBC. In the present review, we focused on the oncogenic or oncosuppressor role of long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) mostly involved in TNBC, highlighting their mode of action and depicting their potential role as a biomarker and/or as targets of new non-coding RNA-based therapeutics.

Prospectives of mirna gene signaling pathway in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is one of the destructive breast cancer subtypes which cannot be treated by current therapies, which is characterized by the lack of estrogen (ER), Progesterone (PR), and Human epidermal receptor (HER2). The treatment for this chemotherapy or radiotherapy and surgery are such treatments and also novel biomarkers or treatment targets can quickly require to improve the outcome of the disease. MicroRNAs are the most popular and offer prospects for TNBC diagnosis and therapy. Some of the miRNAs implicated in THBCs are miR-17-5p, miR-221-3p, miR-26a, miR-136-5p, miR-1296, miR-145, miR-4306, miR-508-5p, miR-448, miR-539, miR-211-5p and miR-218. Potential MiRNAs and their signaling pathways that can be utilized for the diagnosis of TNBC are miR-155, miR-182-5p, miR-9-1-5p, miR-200b, miR-200a, miR-429, miR-195, miR-145-5p, miR-506, and miR-22-3p. miRNAs with known functions as tumor suppressors include miR-1-3p, miR-133a-3p, miR-655, miR-206, miR-136, miR-770, miR-148a, miR-197-3p, miR-137, and miR-127-3p. Analysis of genetic biomarkers, such as miRNAs in TNBC, upholds the pertinence in the diagnosis of the disease. The aim of the review was to clarify the different types of miRNAs characters in TNBC. Recent reports suggest an important role of miRNAs in tumor metastasis. We review here the important miRNAs and their signaling pathways implicated in the oncogenesis, progression, and metastasis of TNBCs.

Let-7a/cMyc/CCAT1/miR-17-5p Circuit Re-sensitizes Atezolizumab Resistance in Triple Negative Breast Cancer through Modulating PD-L1

BACKGROUND

Triple negative breast cancer (TNBC) is an immunogenically hot tumor. The immune checkpoint blockades (ICBs) have been recently emerged as promising therapeutic candidates for several malignancies including TNBC. Yet, the development of innate and/or adaptive resistance by TNBC patients towards ICBs such as programmed death-ligand 1 (PD-L1) inhibitors (e.g. Atezolizumab) shed the light on importance of identifying the underlying mechanisms regulating PD-L1 in TNBC. Recently, it was reported that non-coding RNAs (ncRNAs) perform a fundamental role in regulating PD-L1 expression in TNBC. Hence, this study aims to explore a novel ncRNA axis tuning PD-L1 in TNBC patients and investigate its possible involvement in fighting Atezolizumab resistance.

METHODS

In-silico screening was executed to identify ncRNAs that could potentially target PD-L1. Screening of PD-L1 and the nominated ncRNAs (miR-17-5p, let-7a and CCAT1 lncRNA) was performed in BC patients and cell lines. Ectopic expression and/or knockdown of respective ncRNAs were performed in MDA-MB-231. Cellular viability, migration and clonogenic capacities were evaluated using MTT, scratch assay and colony-forming assay, respectively.

RESULTS

PD-L1 was upregulated in BC patients, especially in TNBC patients. PD-L1 is positively associated with lymph node metastasis and high Ki-67 in recruited BC patients. Let-7a and miR-17-5p were nominated as potential regulators of PD-L1. Ectopic expression of let-7a and miR-17-5p caused a noticeable reduction in PD-L1 levels in TNBC cells. In order to investigate the whole ceRNA circuit regulating PD-L1 in TNBC, intensive bioinformatic studies were performed. The lncRNA, Colon Cancer-associated transcript 1 (CCAT1), was reported to target PD-L1 regulating miRNAs. Results showed that CCAT1 is an upregulated oncogenic lncRNA in TNBC patients and cell lines. CCAT1 siRNAs induced a noticeable reduction in PD-L1 levels and a marked increase in miR-17-5p level, building up a novel regulatory axis CCAT1/miR-17-5p/PD-L1 in TNBC cells that was tuned by the let-7a/c-Myc engine. On the functional level, co-treatment of CCAT-1 siRNAs and let-7a mimics efficiently relieved Atezolizumab resistance in MDA-MB-231 cells.

CONCLUSION

The present study revealed a novel PD-L1 regulatory axis via targeting let-7a/c-Myc/CCAT/miR-17-5p. Additionally, it sheds the light on the potential combinational role of CCAT-1 siRNAs and Let-7a mimics in relieving Atezolizumab resistance in TNBC patients.

New Biomarkers and Treatment Advances in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a specific subtype of breast cancer lacking hormone receptor expression and HER2 gene amplification. TNBC represents a heterogeneous subtype of breast cancer, characterized by poor prognosis, high invasiveness, high metastatic potential, and a tendency to relapse. In this review, the specific molecular subtypes and pathological aspects of triple-negative breast cancer are illustrated, with particular attention to the biomarker characteristics of TNBC, namely: regulators of cell proliferation and migration and angiogenesis, apoptosis-regulating proteins, regulators of DNA damage response, immune checkpoints, and epigenetic modifications. This paper also focuses on omics approaches to exploring TNBC, such as genomics to identify cancer-specific mutations, epigenomics to identify altered epigenetic landscapes in cancer cells, and transcriptomics to explore differential mRNA and protein expression. Moreover, updated neoadjuvant treatments for TNBC are also mentioned, underlining the role of immunotherapy and novel and targeted agents in the treatment of TNBC.

Tumor suppressor miR-218 directly targets epidermal growth factor receptor (EGFR) expression in triple-negative breast cancer, sensitizing cells to irradiation

PURPOSE

MicroRNA-218 (miR-218) is a key regulator of numerous processes relevant to tumor progression. In the present study, we aimed to characterize the relationship between miR-218 and the Epidermal Growth Factor Receptor (EGFR) as well as to understand downstream effects in triple-negative breast cancer (TNBC).

METHODS

We assessed miR-218 and EGFR expression in cell lines and publicly available primary breast cancer gene expression data. We then overexpressed miR-218 in two TNBC cell lines and investigated effects on EGFR and downstream mitogen-activated protein (MAP) kinase signaling. Luciferase reporter assay was used to characterize a direct binding interaction between miR-218 and EGFR mRNA. Digital holographic microscopy helped investigate cell migration and dry mass after miR-218 overexpression. Cell division and invasion were assessed microscopically, while radiation response after miR-218 overexpression alone or combined with additional EGFR knockdown was investigated via clonogenic assays.

RESULTS

We found an inverse correlation between EGFR expression and miR-218 levels in cell lines and primary breast cancer tissues. MiR-218 overexpression resulted in a downregulation of EGFR via direct binding of the mRNA. Activation of EGFR and downstream p44/42 MAPK signaling were reduced after pre-miR-218 transfection. Cell proliferation, motility and invasiveness were inhibited whereas cell death and mitotic catastrophe were upregulated in miR-218 overexpressing cells compared to controls. MiR-218 overexpressing and EGFR siRNA-treated cells were sensitized to irradiation, more than miR-218 overexpressing cells alone.

CONCLUSION

This study characterizes the antagonistic relationship between miR-218 and EGFR. It also demonstrates downstream functional effects of miR-218 overexpression, leading to anti-tumorigenic cellular changes.

Triple-negative Breast Cancer: Identification of circRNAs With Efficacy in Preclinical In Vivo Models

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with insufficient options for therapy. In order to identify new targets and treatment modalities we searched the literature for circular RNAs (circRNAs) which mediate efficacy in TNBC-related in vivo preclinical models. In addition to 5 down-regulated circRNAs which modulate tumor-suppressive pathways, we identified 15 up-regulated circRNAs. Down- and up-regulated refers to expression in corresponding non-transformed cells and tissues. The up-regulated circRNAs comprise five transmembrane receptors and secreted proteins as targets, five transcription factors and transcription-associated targets, four cell-cycle related circRNAs and one involved in paclitaxel resistance. In this review article we discuss drug-discovery related aspects and modalities of therapeutic intervention. Down-regulated circRNAs can be reconstituted by re-expression of corresponding circRNAs in tumor cells or up-regulation of corresponding targets. Up-regulated circRNAs can be inhibited by small-interfering RNA (siRNA) or short hairpin RNA (shRNA)-based approaches or inhibition of the corresponding targets with small molecules or antibody-related moieties.

Metformin and long non-coding RNAs in breast cancer

Breast cancer (BC) is the second most common cancer and cause of death in women. In recent years many studies investigated the association of long non-coding RNAs (lncRNAs), as novel genetic factors, on BC risk, survival, clinical and pathological features. Recent studies also investigated the roles of metformin treatment as the firstline treatment for type 2 diabetes (T2D) played in lncRNAs expression/regulation or BC incidence, outcome, mortality and survival, separately. This comprehensive study aimed to review lncRNAs associated with BC features and identify metformin-regulated lncRNAs and their mechanisms of action on BC or other types of cancers. Finally, metformin affects BC by regulating five BC-associated lncRNAs including GAS5, HOTAIR, MALAT1, and H19, by several molecular mechanisms have been described in this review. In addition, metformin action on other types of cancers by regulating ten lncRNAs including AC006160.1, Loc100506691, lncRNA-AF085935, SNHG7, HULC, UCA1, H19, MALAT1, AFAP1-AS1, AC026904.1 is described.

Recent Clinical Advances on Long Non-Coding RNAs in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a more aggressive type of breast cancer due to its heterogeneity and complex molecular mechanisms. TNBC has a high risk for metastasis, and it is difficult to manage clinical conditions of the patients. Various investigations are being conducted to overcome these challenges using RNA, DNA, and proteins for early diagnosis and treatment. Recently, long non-coding RNAs (lncRNAs) have emerged as a novel target to treat the multistep process of TNBC. LncRNAs regulate epigenetic expression levels, cell proliferation and apoptosis, and tumour invasiveness and metastasis. Thus, lncRNA-based early diagnosis and treatment options could be helpful, especially for patients with severe TNBC. lncRNAs are expressed in a highly specific manner in cells and tissues and are involved in TNBC progression and development. lncRNAs could be used as sensitive and specific targets for diagnosis, treatment, and monitoring of patients with TNBC. Therefore, the exploration of novel diagnostic and prognostic biomarkers is of extreme importance. Here, we discuss the molecular advances on lncRNA regulation of TNBC and lncRNA-based early diagnosis, treatment, and drug resistance.

Clinicopathological and prognostic value of long non-coding RNA CCAT1 expression in patients with digestive system cancer

Colon cancer associated transcript-1 (CCAT1) is known to play an important role in numerous types of human cancer, including bladder, prostate and ovarian cancer. However, a consistent perspective has not been established in digestive system cancer (DSC). To explore the prognostic value of CCAT1 in patients with DSC, a meta-analysis was performed. A systematic search of PubMed, Embase, Web of Science, China National Knowledge Infrastructure, Chinese Biological Medical Literature database, Cochrane Library and WanFang database was applied to select eligible articles. Pooled odds ratios (ORs) or hazard ratios (HRs) with corresponding 95% confidence intervals (CIs) were calculated to estimate the effects of CCAT1 on pathological or clinical features. A total of 1,719 patients from 12 eligible articles were enrolled in the meta-analysis. The results revealed that elevated CCAT1 expression was significantly related to larger tumor size (OR, 1.81; 95% CI, 1.31-2.48), poorer differentiation (OR, 0.45; 95% CI, 0.31-0.64), earlier lymph node metastasis (OR, 3.14; 95% CI, 2.34-4.22) and advanced TNM stage (OR, 3.08; 95% CI, 2.07-4.59). In addition, high CCAT1 expression predicted a poorer outcome for overall survival rate (HR, 2.37; 95% CI, 2.11-2.67) and recurrence-free survival rate (HR, 2.16, 95% CI, 1.31-3.57). High expression levels of CCAT1 were therefore related to unfavorable clinical outcomes of patients with DSC. These results demonstrated that CCAT1 could serve as a prognostic predictor in human DSC.

MicroRNAs: A Link between Mammary Gland Development and Breast Cancer

Breast cancer is among the most common cancers in women, second to skin cancer. Mammary gland development can influence breast cancer development in later life. Processes such as proliferation, invasion, and migration during mammary gland development can often mirror processes found in breast cancer. MicroRNAs (miRNAs), small, non-coding RNAs, can repress post-transcriptional RNA expression and can regulate up to 80% of all genes. Expression of miRNAs play a key role in mammary gland development, and aberrant expression can initiate or promote breast cancer. Here, we review the role of miRNAs in mammary development and breast cancer, and potential parallel roles. A total of 32 miRNAs were found to be expressed in both mammary gland development and breast cancer. These miRNAs are involved in proliferation, metastasis, invasion, and apoptosis in both processes. Some miRNAs were found to have contradictory roles, possibly due to their ability to target many genes at once. Investigation of miRNAs and their role in mammary gland development may inform about their role in breast cancer. In particular, by studying miRNA in development, mechanisms and potential targets for breast cancer treatment may be elucidated.

Functional interplay between long non-coding RNAs and Breast CSCs

Breast cancer (BC) represents aggressive cancer affecting most women’s lives globally. Metastasis and recurrence are the two most common factors in a breast cancer patient's poor prognosis. Cancer stem cells (CSCs) are tumor cells that are able to self-renew and differentiate, which is a significant factor in metastasis and recurrence of cancer. Long non-coding RNAs (lncRNAs) describe a group of RNAs that are longer than 200 nucleotides and do not have the ability to code for proteins. Some of these lncRNAs can be mainly produced in various tissues and tumor forms. In the development and spread of malignancies, lncRNAs have a significant role in influencing multiple signaling pathways positively or negatively, making them promise useful diagnostic and prognostic markers in treating the disease and guiding clinical therapy. However, it is not well known how the interaction of lncRNAs with CSCs will affect cancer development and progression.

Here, in this review, we attempt to summarize recent findings that focus on lncRNAs affect cancer stem cell self-renewal and differentiation in breast cancer development and progression, as well as the strategies and challenges for overcoming lncRNA's therapeutic resistance.

Long non-coding RNA ANRIL promotes chemoresistance in triple-negative breast cancer via enhancing aerobic glycolysis

AIMS

lncRNA ANRIL expression is dysregulated in many human cancers and is thus a useful prognostic marker for cancer patients. However, whether ANRIL is involved in drug resistance in triple-negative breast cancer (TNBC) has not yet been investigated.

MAIN METHODS

A luciferase reporter assay was conducted to verify the binding between miR-125a and ANRIL. RT-PCR and western blotting were performed to detect the expression of miR-125a, ANRIL, and ENO1. Glycolysis stress was assessed using the Seahorse extracellular flux analyzer. Functional studies were performed using both in vitro and in vivo xenograft models.

KEY FINDINGS

ANRIL was markedly upregulated in both patients with TNBC and TNBC cell lines. Knockdown of ANRIL increased the cytotoxic effect of ADR and repressed cellular glycolytic activity in TNBC cells. Mechanistic analysis showed that ANRIL may act as a competing endogenous RNA of miR-125a to relieve the repressive effect of miR-125a on its target glycolytic enzyme enolase (ENO1). Notably, 2-deoxy-glucose attenuated ANRIL-induced increase in drug resistance in TNBC cells.

SIGNIFICANCE

These results indicate that knockdown of ANRIL plays an active role in overcoming drug resistance in TNBC by inhibiting glycolysis through the miR-125a/ENO1 pathway, which may be useful for the development of novel therapeutic targets for treating patients with TNBC, especially those with drug resistance.

The role of PI3K/AKT signaling pathway in gallbladder carcinoma

OBJECTIVES

The prognosis of gallbladder carcinoma (GBC) is poor, with a less than 5% five-year survival rate. Identifying the mechanisms underlying GBC occurrence and advancement is necessary to improve GBC patient prognosis and survival rates. The phosphatidylinositol 3-kinase (PI3K)/serine-threonine kinase (AKT) pathway is involved in cancer deterioration, tumor growth, cell proliferation, and distant metastasis. Studying the impacts of the PI3K/AKT pathway has resulted in the identification of key factors involved in GBC progression that might serve as therapeutic targets, promoting the development of new treatments.

METHODS

We reviewed recent literature exploring abnormal regulation of the PI3K/AKT pathway in gallbladder cancer, with a focus on abnormal RNA levels, protein level regulation, and drug treatment advances.

RESULTS

Further investigation of the regulation of small molecules and proteins by the PI3K/AKT pathway might ultimately provide new diagnostic or prognostic markers or cancer treatment targets. Recent studies have focused on RNA and proteins involved in the regulation of the cell cycle or cell movement in cancer progression via PI3K/AKT pathway, the use of anticancer drug combinations, or the anticancer effects of drugs not currently utilized for cancer treatment.

CONCLUSIONS

We herein review the known available molecules that affect the PI3K/AKT pathway in patients with GBC and the mechanisms of drug action associated with this pathway.

Role of microRNA/lncRNA Intertwined With the Wnt/β-Catenin Axis in Regulating the Pathogenesis of Triple-Negative Breast Cancer

Objective (s): In this mini-review, we aimed to discuss the Wnt/β-catenin signaling pathway modulation in triple-negative breast cancer, particularly the contribution of lncRNAs and miRNAs in its regulation and their possible entwining role in breast cancer pathogenesis, proliferation, migration, or malignancy.

Background: Malignant tumor formation is very high for breast cancer in women and is a leading cause of death all over the globe. Among breast cancer subtypes, triple-negative breast cancer is rife in premenopausal women, most invasive, and prone to metastasis. Complex pathways are involved in this cancer’s pathogenesis, advancement, and malignancy, including the Wnt/β-catenin signaling pathway. This pathway is conserved among vertebrates and is necessary for sustaining cell homeostasis. It is regulated by several elements such as transcription factors, enhancers, non-coding RNAs (lncRNAs and miRNAs), etc.

Methods: We evaluated lncRNAs and miRNAs differentially expressed in triple-negative breast cancer (TNBC) from the cDNA microarray data set literature survey. Using in silico analyses combined with a review of the current literature, we anticipated identifying lncRNAs and miRNAs that might modulate the Wnt/β-catenin signaling pathway.

Result: The miRNAs and lncRNAs specific to triple-negative breast cancer have been identified based on literature and database searches. Tumorigenesis, metastasis, and EMT were all given special attention. Apart from cross-talk being essential for TNBC tumorigenesis and treatment outcomes, our results indicated eight upregulated and seven downregulated miRNAs and 19 upregulated and three downregulated lncRNAs that can be used as predictive or diagnostic markers. This consolidated information could be useful in the clinic and provide a combined literature resource for TNBC researchers working on the Wnt/β-catenin miRNA/lncRNA axis.

Conclusion: In conclusion, because the Wnt pathway and miRNAs/lncRNAs can modulate TNBC, their intertwinement results in a cascade of complex reactions that affect TNBC and related processes. Their function in TNBC pathogenesis has been highlighted in molecular processes underlying the disease progression.

The functional significance and cross-talk of non-coding RNAs in triple negative and quadruple negative breast cancer

One of the leading causes of cancer-related deaths worldwide is breast cancer, among which triple-negative breast cancer (TNBC) is the most malignant and lethal subtype. This cancer accounts for 10-20% of all breast cancer deaths. Proliferation, tumorigenesis, and prognosis of TNBC are affected when the androgen receptor (AR) is not expressed, and it is classified as quadruple negative breast cancer (QNBC). Non-coding RNAs, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), play a significant role in tumorigenesis by virtue of their oncogenic and tumor-suppressive properties. To regulate tumorigenesis, miRNAs interact with their target mRNAs and modulate their expression, whereas lncRNAs can either act alone or interact with miRNAs or other molecules through various signaling pathways. Conversely, circRNAs regulate tumorigenesis by acting as miRNA sponges predominantly. Recently, non-coding RNAs were studied comprehensively for their roles in tumor proliferation, progression, and metastasis. As a result of existing studies and research progress, non-coding RNAs have been implicated in TNBC, necessitating their use as biomarkers for future diagnostic applications. In this review, the non-coding RNAs are explicitly implicated in the regulation of breast cancer, and their cross-talk between TNBC and QNBC is also discussed.

A Novel Prognostic Signature of Immune-Related Long Noncoding RNA Pairs for Tumor-Infiltrating Immune Cells and Drug Susceptibility in Breast Cancer

Prognostic signatures of specific immune-related long noncoding RNAs (irlncRNAs) have been elucidated with the development of immunotherapy for breast cancer, but the heterogeneity of gene expression in different patients still limits their effectiveness. We constructed a new prognostic signature based on the relative expression of differentially expressed irlncRNA (DEirlncRNA) pairs and analyzed its clinical application in 1069 patients from The Cancer Genome Atlas-Breast Cancer (TCGA-BRCA) containing 745 White patients, 180 Black and African American patients, 58 Asian patients, 181 stage I patients, 606 stage II patients, 240 stage III patients, and 20 stage IV patients. Data from TCGA-BRCA and ImmPort were used to screen DEirlncRNAs, and the DEirlncRNA pairs were established by cyclical single comparison of each DEirlncRNA. After the data optimization, we constructed a signature containing 24 DEirlncRNA pairs. Risk groups of this signature were defined using the cutoff value from the 10-year survival receiver operating characteristic curve, and Kaplan-Meier analysis verified its prognostic effectiveness. Furthermore, we confirmed this signature as an independent prognostic factor and confirmed its close association with traditional clinicopathological factors. Moreover, this risk signature was closely related to tumor-infiltrating immune cells and drug susceptibility. In short, we successfully constructed a risk signature of DEirlncRNA pairs, which might provide new insights for breast cancer precision therapy.

What is beyond LncRNAs in breast cancer: A special focus on colon cancer-associated Transcript-1 (CCAT-1)

Long non-coding RNAs (LncRNAs) play a vital role in the process of malignant transformation. In breast cancer (BC), lncRNAs field is currently under intensive investigations. Yet, the role of lncRNAs as promising diagnostic and/or prognostic biomarkers and as therapeutic target/tool among BC patients still needs a special focus from the biomedical scientists. In BC, triple negative breast cancer patients (TNBC) are the unlucky group as they are always represented with the worst prognosis and the highest mortality rates. For that reason, a special focus on TNBC and associated lncRNAs was addressed in this review. Colon cancer-associated transcript 1 (CCAT-1) is a newly discovered oncogenic lncRNA that has been emerged as a vital biomarker for diagnosis, prognosis and therapeutic interventions in multiple malignancies and showed differential expression among TNBC patients. In this review, the authors shed the light onto the general role of lncRNAs in BC and the specific functional activities, molecular mechanisms, competing endogenous ncRNA role of CCAT-1 in TNBC.

Long Noncoding RNAs Regulate the Radioresistance of Breast Cancer

Breast cancer (BRCA) has severely threatened women's health worldwide. Radiotherapy is a treatment for BRCA, which applies high doses of ionizing radiation to induce cancer cell death and reduce disease recurrence. Radioresistance is one of the most important elements that affect the therapeutic efficacy of radiotherapy. Long noncoding RNAs (lncRNAs) are suggested to dominate crucial roles in regulating the biological behavior of BRCA. Currently, some studies indicate that overexpression or inhibition of lncRNAs can greatly alter the radioresistance of BRCA. In this review, we summarized the knowledge on the classification and function of lncRNAs and the molecular mechanism of BRCA radioresistance, listed lncRNAs related to the BRCA radioresistance, highlighted their underlying mechanisms, and discussed the potential application of these lncRNAs in regulating BRCA radioresistance.

lncRNA and breast cancer: Progress from identifying mechanisms to challenges and opportunities of clinical treatment

Breast cancer is a malignant tumor that has a high mortality rate and mostly occurs in women. Although significant progress has been made in the implementation of personalized treatment strategies for molecular subtypes in breast cancer, the therapeutic response is often not satisfactory. Studies have reported that long non-coding RNAs (lncRNAs) are abnormally expressed in breast cancer and closely related to the occurrence and development of breast cancer. In addition, the high tissue and cell-type specificity makes lncRNAs particularly attractive as diagnostic biomarkers, prognostic factors, and specific therapeutic targets. Therefore, an in-depth understanding of the regulatory mechanisms of lncRNAs in breast cancer is essential for developing new treatment strategies. In this review, we systematically elucidate the general characteristics, potential mechanisms, and targeted therapy of lncRNAs and discuss the emerging functions of lncRNAs in breast cancer. Additionally, we also highlight the advantages and challenges of using lncRNAs as biomarkers for diagnosis or therapeutic targets for drug resistance in breast cancer and present future perspectives in clinical practice.

Long Non-Coding RNAs as Potential Diagnostic and Prognostic Biomarkers in Breast Cancer: Progress and Prospects

Breast cancer is the most common malignancy among women worldwide, excluding non-melanoma skin cancer. It is now well understood that breast cancer is a heterogeneous entity that exhibits distinctive histological and biological features, treatment responses and prognostic patterns. Therefore, the identification of novel ideal diagnostic and prognostic biomarkers is of utmost importance. Long non-coding RNAs (lncRNAs) are commonly defined as transcripts longer than 200 nucleotides that lack coding potential. Extensive research has shown that lncRNAs are involved in multiple human cancers, including breast cancer. LncRNAs with dysregulated expression can act as oncogenes or tumor-suppressor genes to regulate malignant transformation processes, such as proliferation, invasion, migration and drug resistance. Intriguingly, the expression profiles of lncRNAs tend to be highly cell-type-specific, tissue-specific, disease-specific or developmental stage-specific, which makes them suitable biomarkers for breast cancer diagnosis and prognosis.

Multifaceted roles of long non-coding RNAs in triple-negative breast cancer: biology and clinical applications

Triple-negative breast cancer (TNBC) is a heterogeneous breast cancer subtype that lacks targeted therapy due to the absence of estrogen, progesterone, and HER2 receptors. Moreover, TNBC was shown to have a poor prognosis, since it involves aggressive phenotypes that confer significant hindrance to therapeutic treatments. Recent state-of-the-art sequencing technologies have shed light on several long non-coding RNAs (lncRNAs), previously thought to have no biological function and were considered as genomic junk. LncRNAs are involved in various physiological as well as pathological conditions, and play a key role in drug resistance, gene expression, and epigenetic regulation. This review mainly focuses on exploring the multifunctional roles of candidate lncRNAs, and their strong association with TNBC development. We also summarise various emerging research findings that establish novel paradigms of lncRNAs function as oncogenes and/or tumor suppressors in TNBC development, suggesting their role as prospective therapeutic targets.

Circ_0000520 contributes to triple-negative breast cancer progression through mediating the miR-1296/ZFX axis

Background

Triple‐negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with a high incidence of local recurrence and metastasis. Circular RNAs (circRNAs) are implicated in the pathomechanism of TNBC. Here, we investigated the function of circ_0000520 in TNBC and its associated mechanism.

Methods

Reverse transcription quantitative polymerase chain reaction (RT‐qPCR) and Western blot assay were used to measure RNA and protein expression. Cell proliferation was analyzed by cell counting kit‐8 (CCK8) assay, flow cytometry and colony formation assay. Cell apoptosis was assessed by flow cytometry. Cell migration ability was analyzed by transwell migration and wound healing assays. Transwell invasion assay was conducted to analyze the invasion ability. Dual‐luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and RNA‐pulldown assay were performed to verify the interaction between microRNA‐1296 (miR‐1296) and circ_0000520 or zinc finger protein X‐linked (ZFX). Xenograft mice model was established to analyze the role of circ_0000520 in xenograft tumor growth in vivo.

Results

Circ_0000520 expression was upregulated in TNBC tissues and cell lines. Circ_0000520 knockdown suppressed the proliferation, migration, and invasion whereas induced the apoptosis of TNBC cells. miR‐1296 was verified as a target of circ_0000520, and circ_0000520 silencing‐mediated suppressive effects on the malignant potential of TNBC cells were partly overturned by miR‐1296 knockdown. miR‐1296 interacted with the 3′ untranslated region (3′UTR) of ZFX, and ZFX overexpression partly reversed miR‐1296 overexpression‐mediated effects in TNBC cells. Circ_0000520 absence reduced ZFX expression by upregulating miR‐1296 in TNBC cells. Circ_0000520 silencing suppressed xenograft tumor growth in vivo.

Conclusions

Circ_0000520 contributed to TNBC development by binding to miR‐1296 to induce ZFX expression.

LncRNA CCAT1 sponges miR-218-5p to promote EMT, cellular migration and invasion of retinoblastoma by targeting MTF2

Retinoblastoma (RB) is the primary neoplasms of the retina that is most common in pediatrics age. Long non-coding RNAs (lncRNAs) has been noticed for strong relation to the occurrence and progress of retinoblastoma. Previously, we have demonstrated that lncRNA colon cancer-associated transcript 1 (CCAT1) in two RB cell lines SO-RB50 and Y79 was obviously overexpressed, and notably, lncRNA CCAT1 attenuated miR-218-5p expressionand induced proliferation, cell migration and invasion. But, how lncRNA CCAT1 acts in RB development and the potential molecular mechanisms remain to be determined. In this study, the expression levels of lncRNA CCAT1 and miR-218-5p were evaluated in RB tissues by Q-PCR, which established the results in the cell lines. Further, lncRNA CCAT1 was shown to promote epithelial-to-mesenchymal transition (EMT), cellular migration and invasion of RB cells by functional analysis of downregulation and overexpression of lncRNA CCAT1 with specific siRNA and pcDNA transfection. By performing bioinformatics and dual luciferase reporter assay, we verified the direct interaction between lncRNA CCAT1 and miR-218-5p. Besides, bioinformatics analysis indicated that metal regulatory transcription factor 2 (MTF2) might be a potent novel target for miR-218-5p, which was further validated with luciferase reporter assay, Q-PCR and also Western blot analysis. Functional analysis and rescue analysis showed that lncRNA CCAT1 via competitive binding to miR-218-5p to modulate MTF2 expression thus accelerate EMT, cell migration and invasion of RB. In conclusion, here we identified the lncRNA CCAT1/miR-218-5p/MTF2 axis in RB cell lines. Our investigations on the function of lncRNA CCAT1 and the roles of the related molecules hint a novel potential target fo RB therapy.

A representation learning model based on variational inference and graph autoencoder for predicting lncRNA-disease associations

Background

Numerous studies have demonstrated that long non-coding RNAs are related to plenty of human diseases. Therefore, it is crucial to predict potential lncRNA-disease associations for disease prognosis, diagnosis and therapy. Dozens of machine learning and deep learning algorithms have been adopted to this problem, yet it is still challenging to learn efficient low-dimensional representations from high-dimensional features of lncRNAs and diseases to predict unknown lncRNA-disease associations accurately.

Results

We proposed an end-to-end model, VGAELDA, which integrates variational inference and graph autoencoders for lncRNA-disease associations prediction. VGAELDA contains two kinds of graph autoencoders. Variational graph autoencoders (VGAE) infer representations from features of lncRNAs and diseases respectively, while graph autoencoders propagate labels via known lncRNA-disease associations. These two kinds of autoencoders are trained alternately by adopting variational expectation maximization algorithm. The integration of both the VGAE for graph representation learning, and the alternate training via variational inference, strengthens the capability of VGAELDA to capture efficient low-dimensional representations from high-dimensional features, and hence promotes the robustness and preciseness for predicting unknown lncRNA-disease associations. Further analysis illuminates that the designed co-training framework of lncRNA and disease for VGAELDA solves a geometric matrix completion problem for capturing efficient low-dimensional representations via a deep learning approach.

Conclusion

Cross validations and numerical experiments illustrate that VGAELDA outperforms the current state-of-the-art methods in lncRNA-disease association prediction. Case studies indicate that VGAELDA is capable of detecting potential lncRNA-disease associations. The source code and data are available at https://github.com/zhanglabNKU/VGAELDA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04073-z.

STAT3-induced HLA-F-AS1 promotes cell proliferation and stemness characteristics in triple negative breast cancer cells by upregulating TRABD

Breast cancer (BC) is one of the most common malignances and is a leading cause of cancer-related deaths in women globally. Triple negative breast cancer (TNBC) is a common subtype of BC. Emerging evidence has indicated the crucial roles of long noncoding RNAs (lncRNAs) in the tumorigenesis of TNBC. Our aim was to explore the role and regulatory mechanism of lncRNA HLA-F antisense RNA 1 (HLA-F-AS1) in TNBC cells. Cell counting kit-8 (CCK-8) assay, colony formation assay, flow cytometry analysis and western blot analysis were used to measure HLA-F-AS1-mediated cellular behaviors in TNBC. Xenograft tumor assay was applied to assess biological function of HLA-F-AS1 in vivo. Luciferase reporter assay and RNA pull down assay were used to verify the binding ability between molecules. Our findings demonstrated that HLA-F-AS1 expression was significantly upregulated in TNBC tissues and cells, and high level of HLA-F-AS1 indicated the poor prognosis of patients with TNBC. HLA-F-AS1 promoted TNBC progression by facilitating cell proliferation and stemness maintenance and inhibiting cell cycle arrest at G0/G1 stage and apoptosis in vitro as well as inducing tumor growth in vivo. HLA-F-AS1. In addition, signal transducer and activator of transcription 3 (STAT3) transcriptionally induced HLA-F-AS1 upregulation in TNBC cells via interacting with HLA-F-AS1 promoter. Moreover, HLA-F-AS1 acted as the molecular sponge of microRNA 541-3p (miR-541-3p) to elevate TRABD (TraB domain containing) expression in TNBC cells. Rescue experiments confirmed that the decrease of cell proliferation and stemness characteristics under silenced HLA-F-AS1 was rescued by TRABD overexpression in TNBC cells. In conclusion, STAT3-induced HLA-F-AS1 facilitates cell proliferation and stemness characteristics in TNBC by miR-541-3p-dependent upregulation of TRABD, which might provide a potential novel direction for the treatment of TNBC.

The role of EMT-related lncRNA in the process of triple-negative breast cancer metastasis

Triple-negative breast cancer (TNBC) is the most malignant and fatal subtype of breast cancer, which has characterized by negativity expression of ER, PR, and HER2. Metastasis is the main factor affecting the prognosis of TNBC, and the process of metastasis is related to abnormal activation of epithelial–mesenchymal transition (EMT). Recent studies have shown that long non-coding RNA (LncRNA) plays an important role in regulating the metastasis and invasion of TNBC. Therefore, based on the metastasis-related EMT signaling pathway, great efforts have confirmed that LncRNA is involved in the molecular mechanism of TNBC metastasis, which will provide new strategies to improve the treatment and prognosis of TNBC. In this review, we summarized many signal pathways related to EMT involved in the transfer process. The advances from the most recent studies of lncRNAs in the EMT-related signal pathways of TNBC metastasis. We also discussed the clinical research, application, and challenges of LncRNA in TNBC.

The long non-coding RNA landscape in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a type of breast cancer that has a higher risk of distant recurrence and metastasis, leading to a relatively aggressive biological behaviour and poor outcome. So far, the clinical management of TNBC is challenging because of its heterogeneity and paucity of specific targeted therapy. Recently, various studies have identified a lot of differently expressed long non-coding RNAs (lncRNAs) in TNBC. Those lncRNAs have been reported to play important roles in the multistep process of TNBC tumorigenesis. Here, we review the biological characteristics of lncRNAs, and present the current state of knowledge concerning the expression, function and regulation of lncRNAs in TNBC. Accumulating studies explored the potential lncRNAs-based therapeutics in TNBC, including the techniques of genetic modification using antisense oligonucleotides, locked nucleic acid and RNA nanotechnology. In current review, we also discuss the future prospects of studies about lncRNAs in TNBC and development of lncRNA-based strategies for clinical TNBC patients.

8q24.21 Locus: A Paradigm to Link Non-Coding RNAs, Genome Polymorphisms and Cancer

The majority of the human genome is comprised of non-protein-coding genes, but the relevance of non-coding RNAs in complex diseases has yet to be fully elucidated. One class of non-coding RNAs is long non-coding RNAs or lncRNAs, many of which have been identified to play a range of roles in transcription and translation. While the clinical importance of the majority of lncRNAs have yet to be identified, it is puzzling that a large number of disease-associated genetic variations are seen in lncRNA genes. The 8q24.21 locus is rich in lncRNAs and very few protein-coding genes are located in this region. Interestingly, the 8q24.21 region is also a hot spot for genetic variants associated with an increased risk of cancer. Research focusing on the lncRNAs in this area of the genome has indicated clinical relevance of lncRNAs in different cancers. In this review, we summarise the lncRNAs in the 8q24.21 region with respect to their role in cancer and discuss the potential impact of cancer-associated genetic polymorphisms on the function of lncRNAs in initiation and progression of cancer.

LncRNA ZFAS1 inhibits triple-negative breast cancer by targeting STAT3

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer with fewer treatment options than other types of invasive breast cancer due to the loss of the estrogen, progesterone receptors and low levels of the HER2 protein, resulting in a poor prognosis for these patients. Here, we found that the expression of the lncRNA, ZFAS1, was significantly downregulated (∼3.0-fold) in blood samples of TNBC patients (n=40) compared to matched healthy controls (n=40). Functionally, silencing of ZFAS1 promoted cell proliferation and colonization of human MDA-MB-231 TNBC cells by inhibiting the expression levels of the cyclin-dependent kinase (CDK) inhibitors p21 (CDKN1A) and p27 (CDKN1B) compared to the scrambled siRNA control cells. Further, we found that downregulation of ZFAS1 led to decreased protein levels of the epithelial markers, E-cadherin, Claudin-1, and Zo-1, with increased protein levels of the mesenchymal markers, Slug and ZEB1. In addition, by utilizing the bioinformatic tools such as RAID v2.0 (RNA Interactome Database Version 2.0), AnnoLnc (Annotate human lncRNA database), and GEPIA (Gene Expression Profiling Interactive Analysis), we identified a strong negative correlation between ZFAS1 and signal transducer and activator of transcription 3 (STAT3) gene expression (R = -0.11, p-value = 0.0002). Further, we observed that decreased ZFAS1 expression significantly (p < 0.05) increased STAT3 and phosphorylated STAT3 (at Ser727 residue) protein levels in TNBC cells. The composite data indicate that ZFAS1 may function as a tumor-suppressor lncRNA with potential as a diagnostic/prognostic marker and may offer a new target for the treatment of TNBC patients.

Silencing long noncoding RNA colon cancer-associated transcript-1 upregulates microRNA-34a-5p to promote proliferation and differentiation of osteoblasts in osteoporosis

Long noncoding RNAs (lncRNAs) have been revealed to be related to multiple physiological and pathology processes such as development, carcinogenesis, and osteogenesis. It is reported that lncRNAs might exert function in osteoblast differentiation and bone formation. Here, we determined this study to clarify whether lncRNA CCAT1 could regulate osteoblast proliferation and differentiation in ovariectomized rats with osteoporosis. The osteoporosis models were established by bilateral ovariectomy and treated with CCAT1 siRNAs to discuss the effect of CCAT1 on pathological changes and osteocyte apoptosis in ovariectomized rats with osteoporosis. The osteoblasts from ovariectomized rats were cultured in vitro, which were then treated with CCAT1 siRNAs to explore the role of CCAT1 in osteoblast proliferation and differentiation. Moreover, the relationships among CCAT1, miR-34a-5p, and SMURF2 were confirmed. CCAT1 and SMURF2 were amplified while miR-34a-5p expression was inhibited in bone tissues and osteoblasts of ovariectomized rats with osteoporosis. Inhibited CCAT1 improved pathology and restricted osteocyte apoptosis of bone tissues in ovariectomized rats with osteoporosis in vivo, and also enhanced differentiation, mineralization abilities, and proliferation, and suppressed apoptosis of osteoblasts from ovariectomized rats in vitro through upregulating miR-34a-5p expression. LncRNA CCAT1 could competitively bind with miR-34a-5p to prevent the degradation of its target gene SMURF2. Results of this research suggested that the CCAT1 inhibits the proliferation and differentiation of osteoblasts in rats with osteoporosis by binding to miR-34a-5p, providing novel biomarkers for osteoporosis treatment.

Long non-coding RNA CCAT1 sponges miR-490 to enhance cell proliferation and migration of non-small cell lung cancer

Background

Non‐small cell lung cancer (NSCLC) accounts for 85% of lung cancer which is the most frequently diagnosed malignancy in China. Colon cancer associated transcript 1 (CCAT1) acts as an oncogene in enhancing tumor progression. However, the effects of CCAT1 in NSCLC remain unclear. The purpose of this study was to explore the role of CCAT1 in NSCLC.

Methods

Wound healing and transwell assays were performed to measure cell migration. RT‐qPCR was employed to calculate the mRNA level of CCAT1 and miR‐490.

Results

High expression of CCAT1 was observed in NSCLC tissues and cells, with low expression of miR‐490. CCAT1 promoted the proliferation and metastasis of H1299 and A549 cells, while miR‐490 had the opposite effect. CCAT1 could specifically bind to miR‐490 and regulate its expression. MiR‐490 partially reversed the inhibitory effect of CCAT1 on cell proliferation and metastasis.

Conclusions

The CCAT1/miR‐490 molecular axis has been shown to be important for the treatment of NSCLC.

Adsorption of miR-218 by lncRNA HOTAIR regulates PDE7A and affects glioma cell proliferation, invasion, and apoptosis

OBJECTIVE

To evaluate the role of targeted adsorption of miR-218 by long-chain non-coding RNAHOTAIR to regulate PDE7A on glioma cell proliferation, invasion, and apoptosis.

METHODS

The expressions of lncRNA HOTAIR, miR-218, and PDE7A in glioma tissues and normal parcancer tissues, NHA and glioma cell lines were determined, and correlations among the three genes were analyzed. The subcellular localization of lncRNA HOTAIR was determined by fluorescent in situ hybridization. Dual-luciferase reporter assay was used to validate the targeted relationship between lncRNA HOTAIR/miR-218/PDE7A. Glioma cells were grouped to receive intervention of lncRNA HOTAIR or miR-218. MTT, transwell, and flow cytometry were performed to determine the proliferation, invasion, and apoptosis of cells.

RESULTS

Compared with the normal tissues and cells, the expression of lncRNA HOTAIR was increased while miR-218 was suppressed in glioma tissues samples and cells (all P<0.05). Inhibition of lncRNA HOTAIR expression, was able to induce apoptosis and suppress the proliferation and invasion of cells (all P<0.05). LncRNA HOTAIR is mainly localized in the cytoplasm, and is able to adsorb miR-218 as ceRNA. The effect of knockdown of HOTAIR on glioma cells could be partially rescued by miR-218 inhibitor. The expression of PDE7A was enhanced in glioma tissues and cells compared to normal tissues and cells (all P<0.05), which positively correlated with the expression of HOTAIR (r=0.546, P<0.05) and negatively correlated with the expression of miR-218 (r=0.363, P<0.05). The targeted relationship between miR-218 and PDE7A was validated: Overexpression of miR-218 was able to suppress the proliferation and invasion of glioma cells and restrain apoptosis compared to the miR-NC group (all P<0.05). The effect of miR-218 on glioma cells could be partially rescued by PDE7A.

CONCLUSION

lncRNA HOTAIR can adsorb miR-218 to regulate expression of PDE7A and promote the malignant biologic behavior of glioma cells.

Long Non-coding RNA Colon Cancer-Associated Transcript-1 Promotes Migration, Invasion, and Epithelial Mesenchymal Transition of Lung Adenocarcinoma by Suppressing miR-219-1

Previous evidence suggests that long non-coding colon cancer-associated transcript-1(CCAT1) plays a pivotal role in the progression of a variety of tumors. However, little is known about its role in lung adenocarcinoma (LAD). In this study, we found LAD tissue samples had a higher expression of CCAT1 but a lower expression of miR-219-1 compared to their adjacent non-tumor tissues. CCAT1 negatively regulated the expression of miR-219-1. miR-219-1 suppressed the proliferation of A549 and H1299 cells. Knockdown of CCAT1 inhibited the proliferation, migration, and invasion of A549 and H1299 cells, which were reversed by the miR-219-1 inhibitor. CCAT1 knockdown increased the expression of E-cadherin but decreased the expressions of N-cadherin and vimentin, which were restored by the miR-219-1 inhibitor. In vivo, knockdown of CCAT1 suppressed the tumor growth of LAD xenografts, which were rescued by the inhibition of miR-219-1. In summary, our findings suggested that CCAT1 promotes the progression of LAD via sponging miR-219-1, providing a potential therapeutic target for LAD.

M2 macrophage-induced lncRNA PCAT6 facilitates tumorigenesis and angiogenesis of triple-negative breast cancer through modulation of VEGFR2

As a common female malignancy, triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancers (BC). This study further studied the role of long noncoding RNA (lncRNA) prostate cancer-associated transcript 6 (PCAT6) in TNBC. Functional assays, including EdU, wound healing, transwell, and immunofluorescence staining, revealed the effect of PCAT6 on cell proliferation, migration, and EMT process. The tube-formation assay disclosed the function of PCAT6 on angiogenesis. In vivo assays were also established to explore the impact of PCAT6 on tumor growth and microangiogenesis. The results revealed that PCAT6 boosted TNBC cell proliferation, migration, and angiogenesis both in vitro and in vivo. Then, this study unveiled that M2 macrophage secreted VEGF to stimulate the upregulation of PCAT6, thus promoting angiogenesis in TNBC. Next, through bioinformatics analysis and mechanism assays, we identified that PCAT6 positively regulated VEGFR2 expression via ceRNA pattern and then participated in VEGFR/AKT/mTOR signaling pathway to accelerate angiogenesis. Moreover, PCAT6 bound USP14, a deubiquitinase, to induce the deubiquitination of VEGFR2. On the whole, M2 macrophage-induced upregulation of PCAT6 facilitates TNBC tumorigenesis through modulation of VEGFR2 expression via ceRNA and deubiquitination patterns.

A bioinformatics approach to identify novel long, non-coding RNAs in breast cancer cell lines from an existing RNA-sequencing dataset

Breast cancer research has traditionally centred on genomic alterations, hormone receptor status and changes in cancer-related proteins to provide new avenues for targeted therapies. Due to advances in next generation sequencing technologies, there has been the emergence of long, non-coding RNAs (lncRNAs) as regulators of normal cellular events, with links to various disease states, including breast cancer. Here we describe our bioinformatic analyses of a previously published RNA sequencing (RNA-seq) dataset to identify lncRNAs with altered expression levels in a subset of breast cancer cell lines. Using a previously published RNA-seq dataset of 675 cancer cell lines, a subset of 18 cell lines was selected for our analyses that included 16 breast cancer lines, one ductal carcinoma in situ line and one normal-like breast epithelial cell line. Principal component analysis demonstrated correlation with well-established categorisation methods of breast cancer (i.e. luminal A/B, HER2 enriched and basal-like A/B). Through detailed comparison of differentially expressed lncRNAs in each breast cancer sub-type with normal-like breast epithelial cells, we identified 15 lncRNAs with consistently altered expression, including three uncharacterised lncRNAs. Utilising data from The Cancer Genome Atlas (TCGA) and The Genotype Tissue Expression (GETx) project via Gene Expression Profiling Interactive Analysis (GEPIA2), we assessed clinical relevance of several identified lncRNAs with invasive breast cancer. Lastly, we determined the relative expression level of six lncRNAs across a spectrum of breast cancer cell lines to experimentally confirm the findings of our bioinformatic analyses. Overall, we show that the use of existing RNA-seq datasets, if re-analysed with modern bioinformatic tools, can provide a valuable resource to identify lncRNAs that could have important biological roles in oncogenesis and tumour progression.

Long noncoding RNA UCA1 promotes cell growth, migration, and invasion by targeting miR-143-3p in oral squamous cell carcinoma

BACKGROUND

The long noncoding RNA (lncRNA) urothelial carcinoma-associated 1 (UCA1) is dysregulated in many types of tumors; however, its role in oral squamous cell carcinoma (OSCC) remains unclear. This study aims to determine the effect of lncRNA UCA1 on OSCC.

METHODS

Fifty-six paired OSCC and adjacent nontumorous tissues were collected and the levels of UCA1, miR-143-3p, and MYO6 in the tissues were evaluated by qRT-PCR. In in vitro experiments, cell viability, migration, and invasion were measured by, respectively, performing CCK-8, wound healing, and transwell assays. The target relationships among UCA1, miR-143-3p, and MYO6 were verified by dual-luciferase assay. Western blot and immunohistochemistry were carried out to determine the protein levels. Xenograft mouse model was established to explore the effects of UCA1 in vivo.

RESULTS

Levels of UCA1 and MYO6 were increased significantly in OSCC, while the level of miR-143-3p was decreased compared with the adjacent nontumorous tissues. UCA1 promoted OSCC cell growth, migration, and invasion both in vitro and in vivo, while miR-143-3p reversed the progression. MYO6 was validated as a target for miR-143-3p, and MYO6 overexpression reversed the effects of miR-143-3p mimic on OSCC cells.

CONCLUSION

LncRNA UCA1 contributes to the proliferation and metastasis of OSCC cells by targeting miR-143-3p and upregulating its downstream gene MYO6. UCA1 could serve as a promising novel target therapy for treatment of OSCC.

Systematic characterization of non-coding RNAs in triple-negative breast cancer

Triple‐negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer with negativity for oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor (HER2). Non‐coding RNAs (ncRNAs) make up most of the transcriptome and are widely present in eukaryotic cells. In recent years, emerging evidence suggests that ncRNAs, mainly microRNAs (miRNAs), long ncRNAs (lncRNAs) and circular RNAs (circRNAs), play prominent roles in the tumorigenesis and development of TNBC, but the functions of most ncRNAs have not been fully described. In this review, we systematically elucidate the general characteristics and biogenesis of miRNAs, lncRNAs and circRNAs, discuss the emerging functions of these ncRNAs in TNBC and present future perspectives in clinical practice.

The Missing Lnc: The Potential of Targeting Triple-Negative Breast Cancer and Cancer Stem Cells by Inhibiting Long Non-Coding RNAs

Treatment decisions for breast cancer are based on staging and hormone receptor expression and include chemotherapies and endocrine therapy. While effective in many cases, some breast cancers are resistant to therapy, metastasize and recur, leading to eventual death. Higher percentages of tumor-initiating cancer stem cells (CSCs) may contribute to the increased aggressiveness, chemoresistance, and worse outcomes among breast cancer. This may be particularly true in triple-negative breast cancers (TNBCs) which have higher percentages of CSCs and are associated with worse outcomes. In recent years, increasing numbers of long non-coding RNAs (lncRNAs) have been identified as playing an important role in breast cancer progression and some of these have been specifically associated within the CSC populations of breast cancers. LncRNAs are non-protein-coding transcripts greater than 200 nucleotides which can have critical functions in gene expression regulation. The preclinical evidence regarding lncRNA antagonists for the treatment of cancer is promising and therefore, presents a potential novel approach for treating breast cancer and targeting therapy-resistant CSCs within these tumors. Herein, we summarize the lncRNAs that have been identified as functionally relevant in breast CSCs. Furthermore, our review of the literature and analysis of patient datasets has revealed that many of these breast CSC-associated lncRNAs are also enriched in TNBC. Together, this suggests that these lncRNAs may be playing a particularly important role in TNBC. Thus, certain breast cancer-promoting/CSC-associated lncRNAs could be targeted in the treatment of TNBCs and the CSCs within these tumors should be susceptible to anti-lncRNA therapy.

The network of non-coding RNAs and their molecular targets in breast cancer

Background

Non-coding RNAs are now recognized as fundamental components of the cellular processes. Non-coding RNAs are composed of different classes, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Their detailed roles in breast cancer are still under scrutiny.

Main body

We systematically reviewed from recent literature the many functional and physical interactions of non-coding RNAs in breast cancer. We used a data driven approach to establish the network of direct, and indirect, interactions. Human curation was essential to de-convolute and critically assess the experimental approaches in the reviewed articles. To enrol the scientific papers in our article cohort, due to the short time span (shorter than 5 years) we considered the journal impact factor rather than the citation number.

The outcome of our work is the formal establishment of different sub-networks composed by non-coding RNAs and coding genes with validated relations in human breast cancer. This review describes in a concise and unbiased fashion the core of our current knowledge on the role of lncRNAs, miRNAs and other non-coding RNAs in breast cancer.

Conclusions

A number of coding/non-coding gene interactions have been investigated in breast cancer during recent years and their full extent is still being established. Here, we have unveiled some of the most important networks embracing those interactions, and described their involvement in cancer development and in its malignant progression.