Long non‑coding RNA SChLAP1 regulates the proliferation of triple negative breast cancer cells via the miR‑524‑5p/HMGA2 axis

The emerging role and mechanism of HMGA2 in breast cancer

High mobility group AT-hook 2 (HMGA2) is a member of the non-histone chromosomal high mobility group (HMG) protein family, which participate in embryonic development and other biological processes. HMGA2 overexpression is associated with breast cancer (BC) cell growth, proliferation, metastasis, and drug resistance. Furthermore, HMGA2 expression is positively associated with poor prognosis of patients with BC, and inhibiting HMGA2 signaling can stimulate BC cell progression and metastasis. In this review, we focus on HMGA2 expression changes in BC tissues and multiple BC cell lines. Wnt/β-catenin, STAT3, CNN6, and TRAIL-R2 proteins are upstream mediators of HMGA2 that can induce BC invasion and metastasis. Moreover, microRNAs (miRNAs) can suppress BC cell growth, invasion, and metastasis by inhibiting HMGA2 expression. Furthermore, long noncoding RNAs (LncRNAs) and circular RNAs (CircRNAs) mainly regulate HMGA2 mRNA and protein expression levels by sponging miRNAs, thereby promoting BC development. Additionally, certain small molecule inhibitors can suppress BC drug resistance by reducing HMGA2 expression. Finally, we summarize findings demonstrating that HMGA2 siRNA and HMGA2 siRNA-loaded nanoliposomes can suppress BC progression and metastasis.

LncRNA MCM3AP-AS1 promotes chemoresistance in triple-negative breast cancer through the miR-524-5p/RBM39 axis

Triple-negative breast cancer (TNBC) is the most lethal subtype of BC, with unfavorable treatment outcomes. Evidence suggests the engagement of lncRNA MCM3AP-AS1 in BC development. This study investigated the action of MCM3AP-AS1 in chemoresistance of TNBC cells. Drug-resistant TNBC cell lines SUM159PTR and MDA-MB-231R were constructed by exposure to increasing concentrations of doxorubicin/docetaxel (DOX/DXL). MCM3AP-AS1 and miR-524-5p expression levels were determined by RT-qPCR. RNA binding motif 39 (RBM39) level was measured using Western blot. Cell viability and apoptosis were assessed by CCK-8 assay and flow cytometry. The targeted binding of miR-524-5p with MCM3AP-AS1 or RBM39 was predicted by ECORI database and validated by dual-luciferase assays. The gain-and-loss of function assays were conducted in cells to investigate the interactions among MCM3AP-AS1, miR-524-5p, and RBM39. TNBC xenograft mouse models were established through subcutaneous injection of MCM3AP-AS1-silencing MDA-MB-231R cells and intraperitoneally administrated with DOX/DXL to verify the role of MCM3AP-AS1 in vivo. MCM3AP-AS1 was upregulated in drug-resistant TNBC cells, and MCM3AP-AS1 silencing could sensitize drug-resistant TNBC cells to chemotherapeutic drugs by promoting apoptosis. MCM3AP-AS1 targeted miR-524-5p. After DOX/DXL treatment, miR-524-5p inhibition partially reversed the effect of MCM3AP-AS1 silencing on inhibiting chemoresistance and promoting apoptosis of drug-resistant TNBC cells. miR-524-5p targeted RBM39. Silencing MCM3AP-AS1 promoted apoptosis via the miR-524-5p/RBM39 axis, thereby enhancing chemosensitivity of drug-resistant TNBC cells. MCM3AP-AS1 knockdown upregulated miR-524-5p, downregulated RBM39, and restrained tumor development in vivo. MCM3AP-AS1 silencing potentiates apoptosis of drug-resistant TNBC cells by upregulating miR-524-5p and downregulating RBM39, thereby suppressing chemoresistance in TNBC.

HMGA2 regulation by miRNAs in cancer: affecting cancer hallmarks and therapy response

High mobility group A 2 (HMGA2) is a protein that modulates the structure of chromatin in the nucleus. Importantly, aberrant expression of HMGA2 occurs during carcinogenesis, and this protein is an upstream mediator of cancer hallmarks including evasion of apoptosis, proliferation, invasion, metastasis, and therapy resistance. HMGA2 targets critical signaling pathways such as Wnt/β-catenin and mTOR in cancer cells. Therefore, suppression of HMGA2 function notably decreases cancer progression and improves outcome in patients. As HMGA2 is mainly oncogenic, targeting expression by non-coding RNAs (ncRNAs) is crucial to take into consideration since it affects HMGA2 function. MicroRNAs (miRNAs) belong to ncRNAs and are master regulators of vital cell processes, which affect all aspects of cancer hallmarks. Long ncRNAs (lncRNAs) and circular RNAs (circRNAs), other members of ncRNAs, are upstream mediators of miRNAs. The current review intends to discuss the importance of the miRNA/HMGA2 axis in modulation of various types of cancer, and mentions lncRNAs and circRNAs, which regulate this axis as upstream mediators. Finally, we discuss the effect of miRNAs and HMGA2 interactions on the response of cancer cells to therapy. Regarding the critical role of HMGA2 in regulation of critical signaling pathways in cancer cells, and considering the confirmed interaction between HMGA2 and one of the master regulators of cancer, miRNAs, targeting miRNA/HMGA2 axis in cancer therapy is promising and this could be the subject of future clinical trial experiments.

Identification and validation of endocrine resistance-related and immune-related long non-coding RNA (lncRNA) signatures for predicting endocrinotherapy response and prognosis in breast cancer

Background

Endocrine resistance remains a major challenge in breast cancer (BRCA). Increasing evidence has revealed that long non-coding RNA (lncRNA) are closely implicated in tumorigenesis, drug resistance, and the immune-related pathways of cancer. However, the immune-related lncRNA remains to be thoroughly investigated in predicting the endocrine therapeutic response and prognosis of BRCA.

Methods

Based on the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases, and calculating the correlation of lncRNAs with immune-related genes obtained from ImmPort and InnateDB databases, we finally obtained endocrine resistance-related and immune-related long non-coding RNAs (ERIR-lncRNAs). Univariate Cox and least absolute shrinkage and selection operator (LASSO) Cox regression were performed to screen prognosis-associated ERIR-lncRNAs and establish signatures, using 2 separate datasets from GEO for external validation. Principal component analysis (PCA), Kaplan-Meier analysis, receiver operating characteristic (ROC) curves, and multivariate Cox regression were performed to demonstrate the robustness and predictability of the signature. We investigated tumor immune infiltration and tumor mutation burden (TMB) between high- and low-risk groups, and the role of key lncRNAs in endocrine resistant breast cancer was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR), Cell Counting Kit 8 (CCK 8) and transwell assays.

Results

A total of 781 endocrine resistance related lncRNAs were identified, of which 12 lncRNAs were associated with immunity. Then, three ERIR-lncRNAs with prognostic relevance were screened to successfully construct the risk signature. Compared to sensitive patients, the endocrine resistant patients had higher risk scores in both the training and validation sets (P<0.05). The high-risk group had significantly shorter survival times (P<0.001) with area under the curve (AUC) values of 0.710, 0.649, and 0.672 at 1, 3, and 5 years. Univariate and multivariate Cox regression indicated that our signature was an independent prognostic factor (P<0.001). Through immune infiltration analysis, it was revealed that the high-risk scores were associated with T follicular helper (Tfh) differentiation and exhibited a pro-tumor phenomenon with the Th1/Th2 balance shifting toward Th2. The key lncRNAs promote cell proliferation and migration as confirmed by qRT-PCR, CCK-8 and transwell assays.

Conclusions

The ERIR-lncRNA signature is valuable in predicting endocrine therapeutic response and prognosis of BRCA, revealing a potential relationship between endocrine resistance and TME.

Long Noncoding RNA Mediated Regulation in Human Embryogenesis, Pluripotency, and Reproduction

Long noncoding RNAs (lncRNAs), a class of noncoding RNAs with more than 200 bp in length, are produced by pervasive transcription in mammalian genomes and regulate gene expression through various action mechanisms. Accumulating data indicate that lncRNAs mediate essential biological functions in human development, including early embryogenesis, induction of pluripotency, and germ cell development. Comprehensive analysis of sequencing data highlights that lncRNAs are expressed in a stage-specific and human/primate-specific pattern during early human development. They contribute to cell fate determination through interacting with almost all classes of cellular biomolecules, including proteins, DNA, mRNAs, and microRNAs. Furthermore, the expression of a few of lncRNAs is highly associated with the pathogenesis and progression of many reproductive diseases, suggesting that they could serve as candidate biomarkers for diagnosis or novel targets for treatment. Here, we review research on lncRNAs and their roles in embryogenesis, pluripotency, and reproduction. We aim to identify the underlying molecular mechanisms essential for human development and provide novel insight into the causes and treatments of human reproductive diseases.

Whole-genome-scale identification of novel non-protein-coding RNAs controlling cell proliferation and survival through a functional forward genetics strategy

Identification of cell fate-controlling lncRNAs is essential to our understanding of molecular cell biology. Here we present a human genome-scale forward-genetics approach for the identification of lncRNAs based on gene function. This approach can identify genes that play a causal role, and immediately distinguish them from those that are differentially expressed but do not affect cell function. Our genome-scale library plus next-generation-sequencing and bioinformatic approach, radically upscales the breadth and rate of functional ncRNA discovery. Human gDNA was digested to produce a lentiviral expression library containing inserts in both sense and anti-sense orientation. The library was used to transduce human Jurkat T-leukaemic cells. Cell populations were selected using continuous culture ± anti-FAS IgM, and sequencing used to identify sequences controlling cell proliferation. This strategy resulted in the identification of thousands of new sequences based solely on their function including many ncRNAs previously identified as being able to modulate cell survival or to act as key cancer regulators such as AC084816.1*, AC097103.2, AC087473.1, CASC15*, DLEU1*, ENTPD1-AS1*, HULC*, MIRLET7BHG*, PCAT-1, SChLAP1, and TP53TG1. Independent validation confirmed 4 out of 5 sequences that were identified by this strategy, conferred a striking resistance to anti-FAS IgM-induced apoptosis.