MicroRNA-221 promotes cisplatin resistance in osteosarcoma cells by targeting PPP2R2A

Low PPP2R2A expression promotes sensitivity to CHK1 inhibition in high-grade serous ovarian cancer

Rationale: High-grade serous ovarian cancer (HGSOC), the most lethal epithelial ovarian cancer subtype, faces persistent challenges despite advances in the therapeutic use of PARP inhibitors. Thus, innovative strategies are urgently needed to improve survival rates for this deadly disease. Checkpoint kinase 1 (CHK1) is pivotal in regulating cell survival during oncogene-induced replication stress (RS). While CHK1 inhibitors (CHK1i's) show promise as monotherapy for ovarian cancer, a crucial biomarker for effective stratification in clinical trials is lacking, hindering efficacy improvement and toxicity reduction. PP2A B55α, encoded by PPP2R2A, is a regulatory subunit of the serine/threonine protein phosphatase 2 (PP2A) that influences CHK1 sensitivity in non-small cell lung cancer (NSCLC). Given the complexity of PP2A B55α function in different types of cancer, here we sought to identify whether PPP2R2A deficiency enhances the sensitivity of HGSOC to CHK1 inhibition. Methods: To determine whether PPP2R2A deficiency affects the sensitivity of HGSOC to CHK1 inhibition, we treated PPP2R2A knockdown (KD) HGSOC cells or HGSOC cells with naturally low PPP2R2A expression with a CHK1 inhibitor, then assessed cell growth in in vitro and in vivo assays. Additionally, we investigated the mechanisms contributing to the increased RS and the enhanced sensitivity to the CHK1 inhibitor in PPP2R2A-KD or deficient cells using various molecular biology assays, including western blotting, immunofluorescence, and DNA fiber assays. Results: Our study suggests that PPP2R2A-KD elevates c-Myc-induced RS via upregulation of replication initiation, rendering HGSOC cells reliant on CHK1 for survival, including those resistant to PARP inhibitors. Conclusion: Combined, these results identify PPP2R2A/PP2A B55α as a potential predictive biomarker for CHK1i sensitivity in HGSOC, as well as suggesting it as a therapeutic target to overcome PARP resistance.

PP2A B55α inhibits epithelial-mesenchymal transition via regulation of Slug expression in non-small cell lung cancer

PP2A B55α, encoded by PPP2R2A, acts as a regulatory subunit of the serine/threonine phosphatase PP2A. Despite a frequent loss of heterozygosity of PPP2R2A in cases of non-small cell lung cancer (NSCLC), research on PP2A B55α's functions remains limited and controversial. To investigate the biological roles of PP2A B55α, we conducted bulk RNA-sequencing to assess the impact of PPP2R2A knockdown using two shRNAs in a NSCLC cell line. Gene set enrichment analysis (GSEA) of the RNA-sequencing data revealed significant enrichment of the epithelial-mesenchymal transition (EMT) pathway, with SNAI2 (the gene encoding Slug) emerging as one of the top candidates. Our findings demonstrate that PP2A B55α suppresses EMT, as PPP2R2A deficiency through knockdown or homozygous or hemizygous depletion promotes EMT and metastatic behavior in NSCLC cells, as evidenced by changes in EMT biomarkers, invasion and migration abilities, as well as metastasis in a tail vein assay. Mechanistically, PP2A B55α inhibits EMT by downregulating SNAI2 expression via the GSK3β-β-catenin pathway. Importantly, PPP2R2A deficiency also slows cell proliferation by disrupting DNA replication, particularly in PPP2R2A-/- cells. Furthermore, PPP2R2A deficiency, especially PPP2R2A-/- cells, leads to an increase in the cancer stem cell population, which correlates with enhanced resistance to chemotherapy. Overall, the decrease in PP2A B55α levels due to hemizygous/homozygous depletion heightens EMT and the metastatic or stemness/drug resistance potential of NSCLC cells despite their proliferation disadvantage. Our study highlights the significance of PP2A B55α in EMT and metastasis and suggests that targeting EMT/stemness could be a potential therapeutic strategy for treating PPP2R2A-deficient NSCLC.

Targeting pediatric solid tumors in the new era of RNA therapeutics

Despite substantial progress in pediatric cancer treatment, poor prognosis remained for patients with recurrent or metastatic disease, given the limitations of approved targeted treatments and immunotherapies. RNA therapeutics offer significant potential for addressing a broad spectrum of diseases, including cancer. Advances in manufacturing and delivery systems are paving the way for the rapid development of therapeutic RNAs for clinical applications. This review summarizes therapeutic RNA classifications and the mechanisms of action, highlighting their potential in manipulating major cancer-related pathways and biological effects. We also focus on the pre-clinical investigation of RNA molecules with efficient delivery systems for their therapeutic potential targeting pediatric solid tumors.

Protein phosphatase 2A modulation and connection with miRNAs and natural products

Protein phosphatase 2A (PP2A), a heterotrimeric holoenzyme (scaffolding, catalytic, and regulatory subunits), regulates dephosphorylation for more than half of serine/threonine phosphosites and exhibits diverse cellular functions. Although several studies on natural products and miRNAs have emphasized their impacts on PP2A regulation, their connections lack systemic organization. Moreover, only part of the PP2A family has been investigated. This review focuses on the PP2A-modulating effects of natural products and miRNAs' interactions with potential PP2A targets in cancer and non-cancer cells. PP2A-modulating natural products and miRNAs were retrieved through a literature search. Utilizing the miRDB database, potential PP2A targets of these PP2A-modulating miRNAs for the whole set (17 members) of the PP2A family were retrieved. Finally, PP2A-modulating natural products and miRNAs were linked via a literature search. This review provides systemic directions for assessing natural products and miRNAs relating to the PP2A-modulating functions in cancer and disease treatments.

Deciphering chemoresistance in osteosarcoma: Unveiling regulatory mechanisms and function through the lens of noncoding RNA

Osteosarcoma (OS) is a primary malignant bone tumor and is prevalent in children, adolescents, and elderly individuals. It has the characteristics of high invasion and metastasis. Neoadjuvant chemotherapy combined with surgical resection is the most commonly used treatment for OS. However, the efficacy of OS is considerably diminished by chemotherapy resistance. In recent years, noncoding RNAs (ncRNAs), including microRNAs, long noncoding RNAs, and circular RNAs, are hot topics in the field of chemotherapy resistance research. Several studies have demonstrated that ncRNAs are substantially associated with chemoresistance in OS. Thus, the present study overviews the abnormally expressed ncRNAs in OS and the molecular mechanisms involved in chemoresistance, with an emphasis on their function in promoting or inhibiting chemoresistance. ncRNAs are expected to become potential therapeutic targets for overcoming drug resistance and predictive biomarkers in OS, which are of great significance for enhancing the therapeutic effect and improving the prognosis.

MicroRNAs as the pivotal regulators of cisplatin resistance in osteosarcoma

Osteosarcoma (OS) is an aggressive bone tumor that originates from mesenchymal cells. It is considered as the eighth most frequent childhood cancer that mainly affects the tibia and femur among the teenagers and young adults. OS can be usually diagnosed by a combination of MRI and surgical biopsy. The intra-arterial cisplatin (CDDP) and Adriamycin is one of the methods of choices for the OS treatment. CDDP induces tumor cell death by disturbing the DNA replication. Although, CDDP has a critical role in improving the clinical complication in OS patients, a high ratio of CDDP resistance is observed among these patients. Prolonged CDDP administrations have also serious side effects in normal tissues and organs. Therefore, the molecular mechanisms of CDDP resistance should be clarified to define the novel therapeutic modalities in OS. Multidrug resistance (MDR) can be caused by various cellular and molecular processes such as drug efflux, detoxification, and signaling pathways. MicroRNAs (miRNAs) are the key regulators of CDDP response by the post transcriptional regulation of target genes involved in MDR. In the present review we have discussed all of the miRNAs associated with CDDP response in OS cells. It was observed that the majority of reported miRNAs increased CDDP sensitivity in OS cells through the regulation of signaling pathways, apoptosis, transporters, and autophagy. This review highlights the miRNAs as reliable non-invasive markers for the prediction of CDDP response in OS patients.

Paradox: Curcumin, a Natural Antioxidant, Suppresses Osteosarcoma Cells via Excessive Reactive Oxygen Species

Osteosarcoma (OS) is an aggressive tumor with a rare incidence. Extended surgical resections are the prevalent treatment for OS, which may cause critical-size bone defects. These bone defects lead to dysfunction, weakening the post-surgical quality of patients' life. Hence, an ideal therapeutic agent for OS should simultaneously possess anti-cancer and bone repair capacities. Curcumin (CUR) has been reported in OS therapy and bone regeneration. However, it is not clear how CUR suppresses OS development. Conventionally, CUR is considered a natural antioxidant in line with its capacity to promote the nuclear translocation of a nuclear transcription factor, nuclear factor erythroid 2 (NRF2). After nuclear translocation, NRF2 can activate the transcription of some antioxidases, thereby circumventing excess reactive oxygen species (ROS) that are deleterious to cells. Intriguingly, this research demonstrated that, in vitro, 10 and 20 μM CUR increased the intracellular ROS in MG-63 cells, damaged cells' DNA, and finally caused apoptosis of MG-63 cells, although increased NRF2 protein level and the expression of NRF2-regulated antioxidase genes were identified in those two groups.

The predictive value of MiR-221 in cancer chemoresistance: a systematic review and meta-analysis

BACKGROUND

Many studies have reported that microRNA-221 (miR-221) is abnormally expressed in various cancers, and there has not been a study to systematically analyze the association between miR-221 and chemoresistance in different cancers.

METHODS

We systematically searched PubMed, Web of Science, Ovid, and Cochrane for relevant studies. The pooled odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (CIs) were used to estimate.

RESULTS

A total of 30 studies with 1670 patients were enrolled in our study. Thirteen cancer types have been studied, and traditional chemotherapy, targeted drugs, endocrine therapy, chemoradiotherapy, and other treatments were used. High miR-221 expression was associated with poor chemotherapy response in most studies, and the meta-analysis confirmed this result (OR = 3.64, 95%CI: 1.73-7.62, p = 0.001). Besides, the higher level of miR-221 was related to shorter overall survival (OS) (HR = 2.16, 95%CI: 1.47-3.16, p < 0.001) and progression-free survival (PFS) (HR = 1.81, 95%CI: 1.51-2.16, p < 0.001) in patients after chemotherapy.

CONCLUSION

Our results highlight that high miR-221 expression has possible associations with chemoresistance and poor prognosis in multiple cancers. Further studies are needed to discover the molecular mechanisms underlying these associations to provide a solid evidence base for it being used as biomarkers of response to chemotherapeutic interventions in cancer.

A spotlight on the interplay of signaling pathways and the role of miRNAs in osteosarcoma pathogenesis and therapeutic resistance

Osteosarcoma (OS) is one of the most common bone cancers that constantly affects children, teenagers, and young adults. Numerous epigenetic elements, such as miRNAs, have been shown to influence OS features like progression, initiation, angiogenesis, and treatment resistance. The expression of numerous genes implicated in OS pathogenesis might be regulated by miRNAs. This effect is ascribed to miRNAs' roles in the invasion, angiogenesis, metastasis, proliferation, cell cycle, and apoptosis. Important OS-related mechanistic networks like the WNT/b-catenin signaling, PTEN/AKT/mTOR axis, and KRAS mutations are also affected by miRNAs. In addition to pathophysiology, miRNAs may influence how the OS reacts to therapies like radiotherapy and chemotherapy. With a focus on how miRNAs affect OS signaling pathways, this review seeks to show how miRNAs and OS are related.

miR-221/222 as biomarkers and targets for therapeutic intervention on cancer and other diseases: A systematic review

Among deregulated microRNAs (miRs) in human malignancies, miR-221 has been widely investigated for its oncogenic role and as a promising biomarker. Moreover, recent evidence suggests miR-221 as a fine-tuner of chronic liver injury and inflammation-related events. Available information also supports the potential of miR-221 silencing as promising therapeutic intervention. In this systematic review, we selected papers from the principal databases (PubMed, MedLine, Medscape, ASCO, ESMO) between January 2012 and December 2020, using the keywords "miR-221" and the specific keywords related to the most important hematologic and solid malignancies, and some non-malignant diseases, to define and characterize deregulated miR-221 as a valuable therapeutic target in the modern vision of molecular medicine. We found a major role of miR-221 in this view.

MicroRNA-92a-3p Enhances Cisplatin Resistance by Regulating Krüppel-Like Factor 4-Mediated Cell Apoptosis and Epithelial-to-Mesenchymal Transition in Cervical Cancer

Recent studies have confirmed the existence and key roles of microRNA (miRNAs) in cancer drug resistance, including cervical cancer (CC). The present study aims to establish a novel role for miR-92a-3p and its associated gene networks in cisplatin (DDP) resistance of CC. First, the disparities in miRNA expression between CC tissues and adjacent normal tissues were screened based on GSE19611 microarray data that retrieved from Gene Expression Omnibus (GEO), and we identified several miRs that were significantly downregulated or upregulated in CC tissues including miR-92a-3p. Moreover, miR-92a-3p was significantly up-regulated in DDP-resistant cells and was the most differently expressed miRNA. Functionally, knockdown of miR-92a-3p increased the sensitivity of DDP-resistant cells to DDP via inhibiting cell proliferation, migration and invasion, and promoting apoptosis. Conversely, overexpression of miR-92a-3p significantly induced DDP resistance in CC parental cells including HeLa and SiHa cells. Moreover, Krüppel-like factor 4 (KLF4) was identified as a direct target of miR-92a-3p, and an obvious inverse correlation was observed between the expression of miR-92a-3p and KLF4 in 40 pairs of cancer tissues. Furthermore, KLF4 knockdown reversed the promoting effect of miR-92a-3p inhibition on DDP sensitivity in DDP-resistant CC cells. Besides, high expression of miR-92a-3p was associated with DDP resistance, as well as a short overall survival in clinic. Taken together, these findings provide important evidence that miR-92a-3p targets KLF4 and is significant in DDP resistance in CC, indicating that miR-92a-3p may be an attractive target to increase DDP sensitivity in clinical CC treatment.

Exosomal miR-136-5p Derived from Anlotinib-Resistant NSCLC Cells Confers Anlotinib Resistance in Non-Small Cell Lung Cancer Through Targeting PPP2R2A

Background

Anlotinib resistance is a challenge for advanced non-small cell lung cancer (NSCLC). Understanding the underlying mechanisms against anlotinib resistance is of great importance to improve prognosis and treatment of patients with advanced NSCLC.

Methods

RT-qPCR assay was used to assess the level of miR-136-5p in anlotinib-resistant NSCLC cells and exosomes derived from anlotinib-resistant NSCLC cells. In addition, miR-136-5p level in tumor tissues from patients who exhibited a poor response to anlotinib therapy and patients who were therapy naïve or patients who exhibited a positive response to anlotinib therapy was detected by RT-qPCR assay.

Results

In this study, we found that high levels of plasma exosomal miR-136-5p is correlated with clinically poor anlotinib response. In addition, anlotinib-resistant NSCLC cells promoted parental NSCLC cell proliferation via transferring functional miR-136-5p from anlotinib-resistant NSCLC cells to parental NSCLC cells via exosomes. Moreover, exosomal miR-136-5p could endow NSCLC cells with anlotinib resistance by targeting PPP2R2A, leading to the activation of Akt pathway. Furthermore, miR-136-5p antagomir packaging into anlotinib-resistant NSCLC cell-derived exosomes functionally restored NSCLC cell anlotinib sensitivity in vitro. Animal studies showed that A549/anlotinib cell-derived exosomal miR-136-5p agomir promoted A549 cell anlotinib resistance in vivo.

Conclusion

Collectively, these findings indicated that anlotinib-resistant NSCLC cell-derived exosomal miR-136-5p confers anlotinib resistance in NSCLC cells by targeting PPP2R2A, indicating miR-136-5p may act as a potential biomarker for anlotinib response in NSCLC.

Effect of MiR-210 on the Chemosensitivity of Breast Cancer by Regulating JAK-STAT Signaling Pathway

The study is aimed at exploring the effect of microribonucleic acid- (miR-) 210 on the chemosensitivity of breast cancer and its potential molecular mechanism. Cell Counting Kit-8 (CCK-8) was applied to detect the half maximal inhibitory concentration (IC50) of cisplatin (DDP) on cell, and quantitative polymerase chain reaction (qPCR) was carried out to measure the relative expression level of miR-210. The IC50 value of DDP on cells was detected via CCK-8 after downregulating the expression of miR-210 in MCF-7/DDP cells. Flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) confirmed the effect of themiR-210 downregulation on the apoptosis of drug-resistant MCF-7/DDP cells. Besides, the impacts of the miR-210 downregulation on apoptosis-related proteins and Janus-activated kinase- (JAK-) signal transducer and activator of transcription (STAT) signaling pathway-related proteins were examined by Western blotting. The interaction between miR-210 and the target protein was detected through luciferase activity assay, qPCR, and Western blotting. Drug-resistant MCF-7/DDP cells had significantly stronger resistance to DDP and a remarkably higher expression level of miR-210 than control parental MCF-7 cells (p < 0.05). After the downregulation of the miR-210 expression, MCF-7/DDP cells had markedly reduced resistance but obviously increased sensitivity to DDP (p < 0.05). MiR-210 downregulation increased the apoptosis of MCF-7/DDP cells (p < 0.05). In addition, after miR-210 was knocked down, the expression level of b-cell lymphoma 2 (Bcl-2) was decreased, while the expression levels of Bcl-2-associated X protein (Bax) and cysteinyl aspartate-specific proteinase-3 (caspase-3) were increased. Besides, miR-210 was able to suppress the expression of protein inhibitor of the activated STAT 4 (PIAS4) gene by directly targeting its 3' untranslated region (3'UTR). The expression of miR-210 has a correlation with chemoresistance of breast cancer MCF-7 cells. MiR-210 regulates the JAK-STAT signal transduction pathway by targeting PIAS4, thus exerting an effect on breast cancer chemosensitivity.

Research Progress of MicroRNA in Chemotherapy Resistance of Osteosarcoma

Osteosarcoma (OS) is a malignant tumor prevalent in adolescents; however, a clinically effective treatment for this malignancy is lacking. The lack of effective treatment methods and factors, such as recurrence and drug resistance, further dampen the prospect of clinically treating OS. In recent years, small molecule microRNAs (miRNAs) with a length of approximately 20-24 nucleotides have gradually attracted the attention of the medical community. Studies have found that miRNAs can regulate the cell cycle, apoptosis, cell proliferation, and cell proliferation. The metabolic response of cancer cells, invasion and metastasis of cancer cells, and angiogenesis play an important role in the process of tumorigenesis. miRNAs regulate gene expression by regulating mRNA expression after transcription. A large amount of data from many studies indicate that they have diagnostic and prognostic biomarker effects in OS and are involved in regulating the metabolism of cancer cells and resistance or sensitivity to chemotherapy drugs. Chemotherapy resistance is one of the most critical problems in clinically treating OS. A large number of basic studies and systematic summaries are required to provide a theoretical basis for elucidating the mechanism and drug development of chemotherapeutic agents. Therefore, this article discusses the role of miRNAs in OS resistance. Herein, the related research progress of the studies is reviewed to provide more useful information for the development of effective therapy.

MicroRNAs: The Link between the Metabolic Syndrome and Oncogenesis

Metabolic syndrome (MetS) represents a cluster of disorders that increase the risk of a plethora of conditions, in particular type two diabetes, cardiovascular diseases, and certain types of cancers. MetS is a complex entity characterized by a chronic inflammatory state that implies dysregulations of adipokins and proinflammatory cytokins together with hormonal and growth factors imbalances. Of great interest is the implication of microRNA (miRNA, miR), non-coding RNA, in cancer genesis, progression, and metastasis. The adipose tissue serves as an important source of miRs, which represent a novel class of adipokines, that play a crucial role in carcinogenesis. Altered miRs secretion in the adipose tissue, in the context of MetS, might explain their implication in the oncogenesis. The interplay between miRs expressed in adipose tissue, their dysregulation and cancer pathogenesis are still intriguing, taking into consideration the fact that miRNAs show both carcinogenic and tumor suppressor effects. The aim of our review was to discuss the latest publications concerning the implication of miRs dysregulation in MetS and their significance in tumoral signaling pathways. Furthermore, we emphasized the role of miRNAs as potential target therapies and their implication in cancer progression and metastasis.

Knockdown of microRNA-203 reduces cisplatin chemo-sensitivity to osteosarcoma cell lines MG63 and U2OS in vitro by targeting RUNX2

Clinical studies have reported that miRNAs abnormal expression are associated with the generation of cisplatin-resistant to osteosarcoma. Our previous research found that miR-203 is downregulated in osteosarcoma cells and overexpressed miR-203 exerts antitumor properties on osteosarcoma cells. However, the role and mechanism of miR-203 in regulating the sensitivity of cisplatin in osteosarcoma cells remains unclear. This study aimed to investigate the effects of miR-203 in cisplatin therapy for osteosarcoma cells in vitro and determined the underlying mechanism. In this study, we found that miR-203 was significantly upregulated in osteosarcoma cells after exposure to cisplatin. miR-203 knockdown reduced the sensitivity of osteosarcoma cells to cisplatin by suppressing cell apoptosis, cell cycle arrest, and inducing invasion. Meanwhile, we found that miR-203 knockdown reduces the therapeutic sensitivity of osteosarcoma cells by upregulating RUNX2. Moreover, we found that RUNX2 silencing sensitizes osteosarcoma cells to chemotherapy treatment of cisplatin. In summary, our findings demonstrated that miR-203 knockdown reduces cisplatin chemo-sensitivity to osteosarcoma cells in vitro by targeting RUNX2, and speculated that miR-203 may be a target for drug resistance of osteosarcoma to cisplatin.

Comprehensive Analysis of Correlations in the Expression of miRNA Genes and Immune Checkpoint Genes in Bladder Cancer Cells

Personalised medicine is the future and hope for many patients, including those with cancers. Early detection, as well as rapid, well-selected treatment, are key factors leading to a good prognosis. MicroRNA mediated gene regulation is a promising area of development for new diagnostic and therapeutic methods, crucial for better prospects for patients. Bladder cancer is a frequent neoplasm, with high lethality and lacking modern, advanced therapeutic modalities, such as immunotherapy. MicroRNAs are involved in bladder cancer pathogenesis, proliferation, control and response to treatment, which we summarise in this perspective in response to lack of recent review publications in this field. We further performed a correlation-based analysis of microRNA and gene expression data in bladder cancer (BLCA) TCGA dataset. We identified 27 microRNAs hits with opposite expression profiles to genes involved in immune response in bladder cancer, and 24 microRNAs hits with similar expression profiles. We discuss previous studies linking the functions of these microRNAs to bladder cancer and assess if they are good candidates for personalised medicine therapeutics and diagnostics. The discussed functions include regulation of gene expression, interplay with transcription factors, response to treatment, apoptosis, cell proliferation and angiogenesis, initiation and development of cancer, genome instability and tumour-associated inflammatory reaction.

Noncoding RNAs in osteosarcoma: Implications for drug resistance

Osteosarcoma is the most frequent bone malignancy in children and adolescents. Despite advances of surgery and chemotherapy in osteosarcoma over the past decades, overall survival rates of osteosarcoma have reached a plateau. The development of multi-drug resistance (MDR) has become the main obstacle in improving chemotherapeutic effects in osteosarcoma treatment. Therefore, understanding detailed mechanisms of chemoresistance and developing novel therapeutic targets to overcome chemoresistance are crucial to improve the prognosis of osteosarcoma patients. Accumulating evidence has proved that multiple noncoding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) play pivotal roles in osteosarcoma progression. Notably, a great number of ncRNAs are abnormally expressed and can regulate chemosensitivity through various mechanisms in osteosarcoma. In this review, we systematically summarize the roles of ncRNAs as well as the molecular mechanisms in modulating drug resistance of osteosarcoma and discuss the potential roles of ncRNAs as biomarkers and novel therapeutic targets for osteosarcoma.

Analysis of a Preliminary microRNA Expression Signature in a Human Telangiectatic Osteogenic Sarcoma Cancer Cell Line

Telangiectatic osteosarcoma (TOS) is an aggressive variant of osteosarcoma (OS) with distinctive radiographic, gross, microscopic features, and prognostic implications. Despite several studies on OS, we are still far from understanding the molecular mechanisms of TOS. In recent years, many studies have demonstrated not only that microRNAs (miRNAs) are involved in OS tumorigenesis, development, and metastasis, but also that the presence in high-grade types of OS of cancer stem cells (CSCs) plays an important role in tumor progression. Despite these findings, nothing has been described previously about the expression of miRNAs and the presence of CSCs in human TOS. Therefore, we have isolated/characterized a putative CSC cell line from human TOS (TOS-CSCs) and evaluated the expression levels of several miRNAs in TOS-CSCs using real-time quantitative assays. We show, for the first time, the existence of CSCs in human TOS, highlighting the in vitro establishment of this unique stabilized cell line and an identification of a preliminary expression of the miRNA profile, characteristic of TOS-CSCs. These findings represent an important step in the study of the biology of one of the most aggressive variants of OS and the role of miRNAs in TOS-CSC behavior.

Recent Insights into Therapy Resistance in Osteosarcoma

Osteosarcoma, the most common bone malignancy of childhood, has been a challenge to treat and cure. Standard chemotherapy regimens work well for many patients, but there remain minimal options for patients with progressive or resistant disease, as clinical trials over recent decades have failed to significantly improve survival. A better understanding of therapy resistance is necessary to improve current treatments and design new strategies for future treatment options. In this review, we discuss known mechanisms and recent scientific advancements regarding osteosarcoma and its patterns of resistance against chemotherapy, radiation, and other newly-introduced therapeutics.

MiR-455-3p downregulation facilitates cell proliferation and invasion and predicts poor prognosis of osteosarcoma

Background

Osteosarcoma (OS) is one of the most primary malignant bone tumors, mainly attracting children and young adults. The microRNAs are mentioned to play vital roles in many cancers, including OS. The purpose of this study was to explore the expression and function of miR-455-3p in OS and predict the potential effects in clinical diagnosis and prognosis.

Method

We conducted quantitative real-time PCR to assess the expression of miR-455-3p in OS tissues and cell lines. The Cell Counting Kit-8 assay, Transwell assay, and flow cytometry were performed to assess the ability of miR-455-3p on cell proliferation, migration, invasion, and apoptosis. Kaplan–Meier curve and Cox regression analysis were used to demonstrate the survival outcome.

Results

This study revealed that the expression of miR-455-3p was decreased in OS tissues and cell lines. The dysregulation of miR-455-3p was in association with tumor size, distant metastasis, and clinical stage. Patients with high miR-455-3p expression had a satisfying survival rate. Multivariate Cox analysis indicated that miR-455-3p was a promising prognostic indicator. Expression of miR-455-3p could inhibit the proliferation, migration, and invasion, and facilitate apoptosis of OS cells in vitro.

Conclusion

These results indicated the miR-455-3p was a potential clinical therapeutic target and prognostic biomarker by suppressing the proliferation, migration, and invasion, as well as enhancing cell apoptosis.

Connecting the Missing Dots: ncRNAs as Critical Regulators of Therapeutic Susceptibility in Breast Cancer

Whether acquired or de novo, drug resistance remains a significant hurdle in achieving therapeutic success in breast cancer (BC). Thus, there is an urge to find reliable biomarkers that will help in predicting the therapeutic response. Stable and easily accessible molecules such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are regarded as valuable prognostic biomarkers and therapeutic targets since they act as crucial regulators of the various mechanisms involved in BC drug resistance. Here, we reviewed the current literature on ncRNAs as mediators of resistance to systemic therapies in BC. Interestingly, upon integrating data results from individual studies, we concluded that miR-221, miR-222, miR-451, Urothelial Carcinoma Associated 1 (UCA1), and Growth arrest-specific 5 (GAS5) are strong candidates as prognostic biomarkers and therapeutic targets since they are regulating multiple drug resistance phenotypes in BC. However, further research around their clinical implications is needed to validate and integrate them into therapeutic applications. Therefore, we believe that our review may provide relevant evidence for the selection of novel therapeutic targets and prognostic biomarkers for BC and will serve as a foundation for future translational research in the field.

Upregulation of cell division cycle 20 in cisplatin resistance-induced epithelial-mesenchymal transition in osteosarcoma cells

Cell division cycle 20 homologue (Cdc20) is characterized as an oncoprotein that is involved in carcinogenesis. Accumulated evidence reveals that Cdc20 plays an oncogenic role by governing cell growth, apoptosis, motility, and metastasis. The role of Cdc20 in drug resistance is elusive. In the present study, we exploited whether Cdc20 is involved in the cisplatin (DDP) resistance-induced epithelial-mesenchymal transition (EMT) of osteosarcoma cells. We found that DDP resistant U2OS and MG63 cells underwent EMT. Moreover, DDP-resistant cells exhibit the mesenchymal features such as enhanced attachment and detachment and increased invasion activity and migration. Mechanistically, Cdc20 was highly expressed in DDP-resistant osteosarcoma cells compared to parental cells. Consistently, downregulation of CdcC20 in DDP-resistant cells reversed the EMT phenotypes and changed the expression of EMT biomarkers. Our studies provide evidence for targeting Cdc20 as a promising approach to enhancing drug sensitivity for the treatment of osteosarcoma.

Circular RNA hsa_circ_0002052 promotes osteosarcoma via modulating miR-382/STX6 axis

Circular RNAs (circRNAs) exert pivotal effects on regulating the progression of osteosarcoma (OS). It was found through microarray analysis that circ-0002052 is abnormally expressed in OS, but the role of circ-0002052 in OS remains obscure. The results of this research manifested that relative to that in non-tumor controls, circ-0002052 level was raised in OS tissues. Up-regulated circ-0002052 was associated with advanced stage, tumor size, and metastasis. Additionally, circ-0002052 elevation indicated a low survival rate in OS patients and silencing of circ-0002052 suppressed proliferation, migration, and invasion of OS cells. It was proved that circ-0002052 sponged miR-382 and stimulated STX6 expression, thus activating Wnt/β-catenin. The function of circ-0002052 reduction in OS cells was effectively reversed by miR-382 suppression. To sum up, it can be concluded that circ-0002052, functioning as a sponge for miR-382, enhances the activation of Wnt/β-catenin mediated by STX6 to stimulate the progression of OS, and circ-0002052 may be an underlying treatment target and a biomarker for prognosis of osteosarcoma.

microRNA-665 is down-regulated in gastric cancer and inhibits proliferation, invasion, and EMT by targeting PPP2R2A

Recently, microRNA-665 (miR-665) has been reported to function as both tumour suppressor and oncogene in several cancer types, including gastric cancer, hepatocellular cancer, and lung cancer. However, the biological function of miR-665 and its precise mechanisms in gastric cancer (GC) have not been well clarified. The aim of this study was to study the roles of miR-665/PPP2R2A axis in GC. The levels of PPP2R2A and miR-665 were detected by quantitative PCR assay in GC tissues and cell lines. Moreover, the biological roles of miR-665 and PPP2R2A in GC cells were assessed by cell proliferation, invasion, and epithelial-mesenchymal transition (EMT). The mRNA and protein levels of PPP2R2A were determined by using quantitative PCR and Western blotting assays. Luciferase assays were used to confirm that PPP2R2A was one target of miR-665. In this study, the miR-665 level was dramatically reduced in GC tissues and cell lines, and the PPP2R2A expression was significantly enhanced. What is more, the PPP2R2A expression was negatively related to the miR-665 level in GC tissues. Furthermore, up-regulation of miR-665 obviously restrained GC cells proliferation, invasion, and EMT. We confirmed that miR-665 could directly target PPP2R2A by luciferase reporter assay. Besides, knockdown of PPP2R2A also could markedly inhibit the proliferation, invasion and EMT of GC cells. Finally, overexpression of miR-665 in GC cells partially reversed the promoted effects of PPP2R2A up-regulation. Overexpression of miR-665 restrained GC cells proliferation, invasion and EMT via regulation of PPP2R2A. SIGNIFICANCE OF THE STUDY:  miR-665 has been reported to function as oncogene or tumour suppressor in different cancers. However, the precise roles of miR-665 in GC have not been elucidated. Our study for the first time demonstrated that miR-665 level was significantly down-regulated in GC. Additionally, miR-665 overexpression inhibited cell growth, invasion, and EMT of GC. Moreover, our data suggested a significant negative correlation between miR-665 and PPP2R2A expression in GC. MiR-665 suppressed GC cell proliferation, invasion, and EMT by directly targeting PPP2R2A, which suggested important roles for miR-665/PPP2R2A axis in the GC pathogenesis and its potential application in cancer therapy.

HOTAIR Promotes Cisplatin Resistance of Osteosarcoma Cells by Regulating Cell Proliferation, Invasion, and Apoptosis via miR-106a-5p/STAT3 Axis

Osteosarcoma (OS) is a common primary malignant bone tumor among adolescences, and the emergence of multidrug resistance poses a huge challenge for clinical treatment of OS. LncRNA HOTAIR (HOX antisense intergenic RNA) has been reported to be associated with many malignancies, including OS. However, the underlying mechanisms of HOTAIR involved in drug resistance in OS are obscure. Our study showed that HOTAIR was upregulated in cisplatin (DDP)-resistant OS tissues and cells. HOTAIR knockdown decreased the DDP resistance, drug resistance-related gene expression, cell proliferation, and invasion and promoted apoptosis of Saos2/DDP, MG-63/DDP, and U2OS/DDP cells. Mechanism researches displayed that miR-106a-5p was downregulated in DDP-resistant OS tissues and cells. MiR-106a-5p directly bound with HOTAIR and was regulated by HOTAIR. Moreover, STAT3 was inhibited by miR-106a-5p at a post-transcriptional level, and the transfection of miR-106a-5p reversed the upregulation of STAT3 caused by HOTAIR overexpression. The increase or decrease of miR-106a-5p suppressed the effect of HOTAIR upregulation or downregulation on DDP resistance, cell proliferation, invasion, and apoptosis of Saos2/DDP, MG-63/DDP, and U2OS/DDP cells. What's more, the transfection of STAT3 siRNA reversed the decrease of DDP resistance, cell proliferation, and invasion and rescued the increase of apoptosis induced by miR-106a-5p inhibition. These data suggested that HOTAIR enhanced DDP resistance of Saos2/DDP, MG-63/DDP, and U2OS/DDP cells by affecting cell proliferation, invasion, and apoptosis via miR-106a-5p/STAT3 axis.

Tumor Suppressor Function of miR-127-3p and miR-376a-3p in Osteosarcoma Cells

Since the introduction of high-dose chemotherapy about 35 years ago, survival rates of osteosarcoma patients have not been significantly improved. New therapeutic strategies replacing or complementing conventional chemotherapy are therefore urgently required. MicroRNAs represent promising targets for such new therapies, as they are involved in the pathology of multiple types of cancer, and aberrant expression of several miRNAs has already been shown in osteosarcoma. In this study, we identified silencing of miR-127-3p and miR-376a-3p in osteosarcoma cell lines and tissues and investigated their role as potential tumor suppressors in vitro and in vivo. Transfection of osteosarcoma cells (n = 6) with miR-127-3p and miR-376a-3p mimics significantly inhibited proliferation and reduced the colony formation capacity of these cells. In contrast, we could not detect any influence of miRNA restoration on cell cycle and apoptosis induction. The effects of candidate miRNA restoration on tumor engraftment and growth in vivo were analyzed using a chicken chorioallantoic membrane (CAM) assay. Cells transfected with mir-127-3p and miR-376a-3p showed reduced tumor take rates and tumor volumes and a significant decrease of the cumulative tumor volumes to 41% and 54% compared to wildtype cells. The observed tumor suppressor function of both analyzed miRNAs indicates these miRNAs as potentially valuable targets for the development of new therapeutic strategies for the treatment of osteosarcoma.