17β-Estradiol treatment drives Sp1 to upregulate MALAT-1 expression and epigenetically affects physiological processes in U2OS cells

mTORC1 accelerates osteosarcoma progression via m6A-dependent stabilization of USP7 mRNA

Osteosarcoma (OS) is considered a sex steroid hormone-dependent bone tumor. The development and progression of OS are regulated by 17β-estradiol (E2). However, the detailed mechanisms of E2-modulated OS progression remained to be elucidated. Here, we found that E2-activated mammalian target of rapamycin (mTOR) signaling promoted N6-methyladenosine (m6A) modification through regulating WTAP. Inhibition of mTOR complex 1 (mTORC1) reversed E2-activated WTAP expression. Meanwhile, inhibition of mTORC1 suppressed OS cell proliferation and migration. Deficiency of TSC2 activated mTORC1 signaling and enhanced OS cell proliferation and migration, while abrogated by Rapamycin. Interestingly, mTOMC1 promoted mRNA stability of ubiquitin-specific protease 7 (USP7) through m6A modification. Loss of USP7 suppressed the proliferation, migration, and ASC specks, while promoted apoptosis of OS cells. USP7 interacted with NLRP3 and deubiquitinated NLRP3 through K48-ubiquitination. USP7 was upregulated and positive correlation with NLRP3 in OS patients with high level of E2. Loss of USP7 suppressed the progression of OS via inhibiting NLRP3 inflammasome signaling pathway. Our results demonstrated that E2-activtated mTORC1 promoted USP7 stability, which promoted OS cell proliferation and migration via upregulating NLRP3 expression and enhancing NLRP3 inflammasome signaling pathway. These results discover a novel mechanism of E2 regulating OS progression and provide a promising therapeutic target for OS progression.

Long noncoding RNA and phase separation in cellular stress response

Stress response is important for sensing and adapting to environmental changes. Recently, RNA-protein condensates, which are a type of membrane-less organelle formed by liquid-liquid phase separation, have been proposed to regulate the stress response. Because RNA-protein condensates are formed through interactions between positively charged proteins and negatively charged RNAs, the ratio of proteins to RNAs is critical for phase-separated condensate formation. In particular, long noncoding RNAs (lncRNAs) can efficiently nucleate phase-separated RNA-protein condensates because of their secondary structure and long length. Therefore, increased attention has been paid to lncRNAs because of their potential role as a regulator of biological condensates by phase separation under stress response. In this review, we summarize the current research on the involvement of lncRNAs in the formation of RNA-protein condensates under stress response. We also demonstrate that lncRNA-driven phase separation provides a useful basis to understanding the response to several kinds of cellular stresses.

ncRNAseq: simple modifications to RNA-seq library preparation allow recovery and analysis of mid-sized non-coding RNAs

Despite their abundance, mid-sized RNAs (30-300 nt) have not been extensively studied by high-throughput sequencing, mostly due to selective loss in library preparation. The authors propose simple and inexpensive modifications to the Illumina TruSeq protocol (ncRNAseq), allowing the capture and sequencing of mid-sized non-coding RNAs without detriment to the coverage of coding mRNAs. This protocol is coupled with a two-step alignment: a pre-alignment to a curated non-coding genome, passing only the non-mapping reads to a standard genomic alignment. ncRNAseq correctly assigns the highest read-numbers to established abundant non-coding RNAs and correctly identifies cytosolic and nuclear enrichment of known non-coding RNAs in two cell lines.

Osteosarcoma and Metastasis

Osteosarcoma is the most common primary bone malignancy in adolescents. Its high propensity to metastasize is the leading cause for treatment failure and poor prognosis. Although the research of osteosarcoma has greatly expanded in the past decades, the knowledge and new therapy strategies targeting metastatic progression remain sparse. The prognosis of patients with metastasis is still unsatisfactory. There is resonating urgency for a thorough and deeper understanding of molecular mechanisms underlying osteosarcoma to develop innovative therapies targeting metastasis. Toward the goal of elaborating the characteristics and biological behavior of metastatic osteosarcoma, it is essential to combine the diverse investigations that are performed at molecular, cellular, and animal levels from basic research to clinical translation spanning chemical, physical sciences, and biology. This review focuses on the metastatic process, regulatory networks involving key molecules and signaling pathways, the role of microenvironment, osteoclast, angiogenesis, metabolism, immunity, and noncoding RNAs in osteosarcoma metastasis. The aim of this review is to provide an overview of current research advances, with the hope to discovery druggable targets and promising therapy strategies for osteosarcoma metastasis and thus to overcome this clinical impasse.

Suppression of Estrogen Receptor Alpha Inhibits Cell Proliferation, Differentiation and Enhances the Chemosensitivity of P53-Positive U2OS Osteosarcoma Cell

Osteosarcoma is a highly malignant musculoskeletal tumor that is commonly noticed in adolescent children, young children, and elderly adults. Due to advances in surgery, chemotherapy and imaging technology, survival rates have improved to 70–80%, but chemical treatments do not enhance patient survival; in addition, the survival rate after chemical treatments is still low. The most obvious clinical feature of osteosarcoma is new bone formation, which is called “sun burst”. Estrogen receptor alpha (ERα) is an essential feature of osteogenesis and regulates cell growth in various tumors, including osteosarcoma. In this study, we sought to investigate the role of ERα in osteosarcoma and to determine if ERα can be used as a target to facilitate the chemosensitivity of osteosarcoma to current treatments. The growth rate of each cell clone was assayed by MTT and trypan blue cell counting, and cell cycle analysis was conducted by flow cytometry. Osteogenic differentiation was induced by osteogenic induction medium and quantified by ARS staining. The effects of ERα on the chemoresponse of OS cells treated with doxorubicin were evaluated by colony formation assay. Mechanistic studies were conducted by examining the levels of proteins by Western blot. The role of ERα on OS prognosis was investigated by an immunohistochemical analysis of OS tissue array. The results showed an impaired growth rate and a decreased osteogenesis ability in the ERα-silenced P53(+) OS cell line U2OS, but not in P53(−) SAOS2 cells, compared with the parental cell line. Cotreatment with tamoxifen, an estrogen receptor inhibitor, increased the sensitivity to doxorubicin, which decreased the colony formation of P53(+) U2OS cells. Cell cycle arrest in the S phase was observed in P53(+) U2OS cells cotreated with low doses of doxorubicin and tamoxifen, while increased levels of apoptosis factors indicated cell death. Moreover, patients with ER−/P53(+) U2OS showed better chemoresponse rates (necrosis rate > 90%) and impaired tumor sizes, which were compatible with the findings of basic research. Taken together, ERα may be a potential target of the current treatments for osteosarcoma that can control tumor growth and improve chemosensitivity. In addition, the expression of ERα in osteosarcoma can be a prognostic factor to predict the response to chemotherapy.

Regulatory Networks of LncRNA MALAT-1 in Cancer

Long noncoding (lnc)RNAs are a group of RNAs with a length greater than 200 nt that do not encode a protein but play an essential role in regulating the expression of target genes in normal biological contexts as well as pathologic processes including tumorigenesis. The lncRNA metastasis-associated lung adenocarcinoma transcript (MALAT)-1 has been widely studied in cancer. In this review, we describe the known functions of MALAT-1; its mechanisms of action; and associated signaling pathways and their clinical significance in different cancers. In most malignancies, including lung, colorectal, thyroid, and other cancers, MALAT-1 functions as an oncogene and is upregulated in tumors and tumor cell lines. MALAT-1 has a distinct mechanism of action in each cancer type and is thus at the center of large gene regulatory networks. Dysregulation of MALAT-1 affects cellular processes such as alternative splicing, epithelial–mesenchymal transition, apoptosis, and autophagy, which ultimately results in the abnormal cell proliferation, invasion, and migration that characterize cancers. In other malignancies, such as glioma and endometrial carcinoma, MALAT-1 functions as a tumor suppressor and thus forms additional regulatory networks. The current evidence indicates that MALAT-1 and its associated signaling pathways can serve as diagnostic or prognostic biomarker or therapeutic target in the treatment of many cancers.

Calycosin induces apoptosis in osteosarcoma cell line via ERβ‑mediated PI3K/Akt signaling pathways

Previous studies have shown that calycosin, a natural phytoestrogen which is structurally similar to estrogen, inhibits proliferation and induces apoptosis in estrogen-dependent cancer types via the estrogen receptor (ER)β-induced inhibition of PI3K/Akt. Therefore, the aims of the present study were to investigate the effects of calycosin on human osteosarcoma (OS), and to examine the molecular mechanisms associated with ERβ. Human OS MG-63 cells were treated with various concentrations of calycosin, and MTT and flow cytometry assays were used to assess the effects of calycosin on cellular proliferation and apoptosis. In addition, protein expression levels of ERβ, phosphorylated (p)-PI3K, p-Akt, cleaved poly (ADP-ribose) polymerase 1 (PARP) and cleaved caspase-3 were evaluated by western blot analysis. The present results suggested that calycosin inhibited proliferation and induced apoptosis in MG-63 cells. Furthermore, increased ERβ expression was detected in OS MG-63 cells treated with calycosin, and an ERβ inhibitor (PHTPP) reversed calycosin-induced cytotoxicity and apoptosis. Moreover, phosphorylation levels of PI3K and Akt were significantly downregulated after calycosin treatment, whereas PHTPP reversed their phosphorylation. ERβ-mediated PI3K/Akt downstream signaling pathways were found to influence the activity of poly (ADP-ribose) polymerase 1 and caspase-3. Thus, the present results indicated that calycosin inhibited proliferation and induced apoptosis in OS MG-63 cells, and that these effects were mediated by ERβ-dependent inhibition of the PI3K/Akt pathways.

Metastasis Associated Lung Adenocarcinoma Transcript 1: An update on expression pattern and functions in carcinogenesis

The Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1) is among long non-coding RNAs (lncRNAs) which has disapproved the old term of "junk DNA" which was used for majority of human genome which are not transcribed to proteins. An extensive portion of literature points to the fundamental role of this lncRNA in tumorigenesis process of diverse cancers ranging from solid tumors to leukemia. Being firstly identified in lung cancer, it has prognostic and diagnostic values in several cancer types. Consistent with the proposed oncogenic roles for this lncRNA, most of studies have shown up-regulation of MALAT1 in malignant tissues compared with non-malignant/normal tissues of the same source. However, few studies have shown down-regulation of MALAT1 in breast cancer, endometrial cancer, colorectal cancer and glioma. In the current study, we have conducted a comprehensive literature search and provided an up-date on the role of MALAT1 in cancer biology. Our investigation underscores a potential role as a diagnostic/prognostic marker and a putative therapeutic target for MALAT1.

Estradiol promotes EMT in endometriosis via MALAT1/miR200s sponge function

Endometriosis is an estrogen-dependent benign gynecological disease that shares some common features of malignancy. Epithelial-mesenchymal transition (EMT) has been recognized as a core mechanism of endometriosis. MALAT1 is widely known as EMT promoter, while miR200 family members (miR200s) are considered as EMT inhibitors. Previous studies have reported that MALAT1 upregulation and miR200s downregulation are observed in endometriosis. MiR200c has been regarded as the strongest member of miR200s to interact with MALAT1. However, whether MALAT1/miR200c regulates EMT remains largely unclear. In this study, the roles of miR200s and MALAT1 in ectopic endometrium were investigated. Additionally, the effects of E2 on EMT and MALAT1/miR200s were examined in both EECs and Ishikawa cells. Notably, E2 could upregulate MALAT1 and downregulate miR200s expression levels and induce EMT in EECs and Ishikawa cells. PHTPP, an ERβ antagonist, could reverse the effect of E2. Overexpression of miR200c and knockdown of MALAT1 significantly inhibited E2-mediated EMT, suggesting that both miR200c and MALAT1 are involved in the E2-induced EMT process in endometriosis. In addition, a reciprocal inhibition was found between miR200s and MALAT1. Therefore, the role of MALAT1/miR200c in EMT is influenced by the presence of estrogen during endometriosis development.

Estrogen receptor β upregulated by lncRNA-H19 to promote cancer stem-like properties in papillary thyroid carcinoma

Estrogen receptor β (ERβ) plays critical roles in thyroid cancer progression. However, its role in thyroid cancer stem cell maintenance remains elusive. Here, we report that ERβ is overexpressed in papillary thyroid cancer stem cells (PTCSCs), whereas ablation of ERβ decreases stemness-related factors expression, diminishes ALDH⁺ cell populations, and suppresses sphere formation ability and tumor growth. Screening estrogen-responsive lncRNAs in PTC spheroid cells, we find that lncRNA-H19 is highly expressed in PTCSCs and PTC tissue specimens, which is correlated with poor overall survival. Mechanistically, estradiol (E2) significantly promotes H19 transcription via ERβ and elevates H19 expression. Silencing of H19 inhibits E2-induced sphere formation ability. Furthermore, H19 acting as a competitive endogenous RNA sequesters miRNA-3126-5p to reciprocally release ERβ expression. ERβ depletion reverses H19-induced stem-like properties upon E2 treatment. Appropriately, ERβ is upregulated in PTC tissue specimens. Notably, aspirin attenuates E2-induced cancer stem-like traits through decreasing both H19 and ERβ expression. Collectively, our findings reveal that ERβ-H19 positive feedback loop has a compelling role in PTCSC maintenance under E2 treatment and provides a potential therapeutic targeting strategy for PTC.

Emerging roles of long non-coding RNAs in the toxicology of environmental chemicals

Environmental chemicals (ECs) are drawing great attention to their effects on health and their toxicological mechanisms are being investigated. Long non-coding RNA (lncRNA) is a class of RNA with more than 200 nucleotides and does not have protein coding potential. Recently, it is emerging as a star molecule that participates in a wide range of physiological and pathological processes. It has been reported to be abnormally expressed in diseases. As an epigenetic factor, lncRNAs play an important role in the response of organisms to environmental stress. Their roles in the toxicity of ECs are being identified. Altered expression profiles of lncRNAs have been explored after exposure to ECs. Various kinds of ECs are reported to disturb the expression of lncRNAs in vitro and in vivo. Then, dysregulated lncRNAs can affect the expression of target genes directly or indirectly via regulating the level of microRNAs. The network among lncRNAs, microRNAs and mRNAs can initiate or impede specific signaling pathway and lead to adverse outcome upon exposure to ECs. Recovery of the lncRNAs level by overexpression or knockdown technology diminished the effect induced by ECs. In the review, biological roles of lncRNAs are depicted. The lncRNAs involved in the toxicology are summarized. Types of ECs that have been reported to affect the expression of lncRNAs are categorized. The interaction between various types of ECs and lncRNAs is discussed.

High N-Acetyltransferase 1 Expression Is Associated with Estrogen Receptor Expression in Breast Tumors, but Is not Under Direct Regulation by Estradiol, 5α-androstane-3β,17β-Diol, or Dihydrotestosterone in Breast Cancer Cells

N-acetyltransferase 1 (NAT1) is an enzyme that metabolizes carcinogens, which suggests a potential role in breast carcinogenesis. High NAT1 expression in breast tumors is associated with estrogen receptor α (ERα+) and the luminal subtype. We report that NAT1 mRNA transcript, protein, and enzyme activity were higher in human breast tumors with high expression of ERα/ESR1 compared with normal breast tissue. There was a strong correlation between NATb promoter and NAT1 protein expression/enzyme activity. High NAT1 expression in tumors was not the result of adipocytes, as evidenced by low perilipin (PLIN) expression. ESR1, NAT1, and XBP1 expression were associated in tumor biopsies. Direct regulation of NAT1 transcription by estradiol (E₂) was investigated in ERα (+) MCF-7 and T47D breast cancer cells. E₂ did not increase NAT1 transcript expression but increased progesterone receptor expression in a dose-dependent manner. Likewise, NAT1 transcript levels were not increased by dihydrotestosterone (DHT) or 5α-androstane-3β, (3β-adiol) 17β-diol. Dithiothreitol increased levels of the activated, spliced XBP1 in ERα (+) MCF-7 and T47D breast cancer cells but did not affect NAT1 or ESR1 expression. We conclude that NAT1 expression is not directly regulated by E₂, DHT, 3β-adiol, or dithiothreitol despite high NAT1 and ESR1 expression in luminal A breast cancer cells, suggesting that ESR1, XBP1, and NAT1 expression may share a common transcriptional network arising from the luminal epithelium associated with better survival in breast cancer. Clusters of high-expression genes, including NAT1, in breast tumors might serve as potential targets for novel therapeutic drug development.

Combined analysis of ChIP-seq and gene microarray datasets identify the E2-mediated genes in ERα-dependent manner in osteosarcoma

Osteosarcoma is a common bone tumor which is affected by E2, the most representative estrogen. Gene regulation function of E2 is highly dependent on estrogen receptor. The purpose of this study was to explore the gene regulation patterns of E2 through estrogen receptor α (ESR1) in osteosarcoma based on the combined analysis of ChIP-seq and gene microarray. All of the datasets were downloaded from the Gene Expression Omnibus (GEO). Differential expression genes (DEGs) in E2 treated U2OS cells expressing ESR1 (U2OS-ERα) compared with those treated with vehicle were obtained based on R programming software. ESR1-specific binding sites (peaks) in E2 treated U2OS cells were identified through MACS. Overlaps between DEGs and ESR1 target genes which contained peaks in promoters were considered as reliable E2-mediated genes through ESR1 in osteosarcoma. Moreover, we conducted miRNA-Gene regulation analysis for those genes through miRWalk database to identify potential therapeutic targets for the genes. Functional enrichment analysis of DEGs indicated their potential involvement in cancer, and cell activity-related processes. Fifteen overlaps were identified between DEGs and target genes of ESR1, of which 12 were found to be regulated by miRNA. Several known estrogen response genes and novel genes were obtained in this study and they might provide potential therapeutic targets for osteosarcoma.