MicroRNA-199a-5p inhibits cisplatin-induced drug resistance via inhibition of autophagy in osteosarcoma cells

Autophagy-driven regulation of cisplatin response in human cancers: Exploring molecular and cell death dynamics

Despite the challenges posed by drug resistance and side effects, chemotherapy remains a pivotal strategy in cancer treatment. A key issue in this context is macroautophagy (commonly known as autophagy), a dysregulated cell death mechanism often observed during chemotherapy. Autophagy plays a cytoprotective role by maintaining cellular homeostasis and recycling organelles, and emerging evidence points to its significant role in promoting cancer progression. Cisplatin, a DNA-intercalating agent known for inducing cell death and cell cycle arrest, often encounters resistance in chemotherapy treatments. Recent studies have shown that autophagy can contribute to cisplatin resistance or insensitivity in tumor cells through various mechanisms. This resistance can be mediated by protective autophagy, which suppresses apoptosis. Additionally, autophagy-related changes in tumor cell metastasis, particularly the induction of Epithelial-Mesenchymal Transition (EMT), can also lead to cisplatin resistance. Nevertheless, pharmacological strategies targeting the regulation of autophagy and apoptosis offer promising avenues to enhance cisplatin sensitivity in cancer therapy. Notably, numerous non-coding RNAs have been identified as regulators of autophagy in the context of cisplatin chemotherapy. Thus, therapeutic targeting of autophagy or its associated pathways holds potential for restoring cisplatin sensitivity, highlighting an important direction for future clinical research.

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.

Autophagy Modulation as a Potential Therapeutic Strategy in Osteosarcoma: Current Insights and Future Perspectives

Autophagy, the process that enables the recycling and degradation of cellular components, is essential for homeostasis, which occurs in response to various types of stress. Autophagy plays an important role in the genesis and evolution of osteosarcoma (OS). The conventional treatment of OS has limitations and is not always effective at controlling the disease. Therefore, numerous researchers have analyzed how controlling autophagy could be used as a treatment or strategy to reverse resistance to therapy in OS. They highlight how the inhibition of autophagy improves the efficacy of chemotherapeutic treatments and how the promotion of autophagy could prove positive in OS therapy. The modulation of autophagy can also be directed against OS stem cells, improving treatment efficacy and preventing cancer recurrence. Despite promising findings, future studies are needed to elucidate the molecular mechanisms of autophagy and its relationship to OS, as well as the mechanisms underlying the functioning of autophagic modulators. Careful evaluation is required as autophagy modulation may have adverse effects on normal cells, and the optimization of autophagic modulators for use as drugs in OS is imperative.

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.

Regulatory miRNAs in cancer cell recovery from therapy exposure and its implications as a novel therapeutic strategy for preventing disease recurrence

The desired outcome of cancer therapies is the eradication of disease. This can be achieved when therapy exposure leads to therapy-induced cancer cell death as the dominant outcome. Theoretically, a permanent therapy-induced growth arrest could also contribute to a complete response, which has the potential to lead to remission. However, preclinical models have shown that therapy-induced growth arrest is not always durable, as recovering cancer cell populations can contribute to the recurrence of cancer. Significant research efforts have been expended to develop strategies focusing on the prevention of recurrence. Recovery of cells from therapy exposure can occur as a result of several cell stress adaptations. These include cytoprotective autophagy, cellular quiescence, a reversable form of senescence, and the suppression of apoptosis and necroptosis. It is well documented that microRNAs regulate the response of cancer cells to anti-cancer therapies, making targeting microRNAs therapeutically a viable strategy to sensitization and the prevention of recovery. We propose that the use of microRNA-targeting therapies in prolonged sequence, that is, a significant period after initial therapy exposure, could reduce toxicity from the standard combination strategy, and could exploit new epigenetic states essential for cancer cells to recover from therapy exposure. In a step toward supporting this strategy, we survey the available scientific literature to identify microRNAs which could be targeted in sequence to eliminate residual cancer cell populations that were arrested as a result of therapy exposure. It is our hope that by successfully identifying microRNAs which could be targeted in sequence we can prevent disease recurrence.

MicroRNAs as the critical regulators of autophagy-mediated cisplatin response in tumor cells

Chemotherapy is one of the most common therapeutic methods in advanced and metastatic tumors. Cisplatin (CDDP) is considered as one of the main first-line chemotherapy drugs in solid tumors. However, there is a high rate of CDDP resistance in cancer patients. Multi-drug resistance (MDR) as one of the main therapeutic challenges in cancer patients is associated with various cellular processes such as drug efflux, DNA repair, and autophagy. Autophagy is a cellular mechanism that protects the tumor cells toward the chemotherapeutic drugs. Therefore, autophagy regulatory factors can increase or decrease the chemotherapy response in tumor cells. MicroRNAs (miRNAs) have a pivotal role in regulation of autophagy in normal and tumor cells. Therefore, in the present review, we discussed the role of miRNAs in CDDP response through the regulation of autophagy. It has been reported that miRNAs mainly increased the CDDP sensitivity in tumor cells by inhibition of autophagy. PI3K/AKT signaling pathway and autophagy-related genes (ATGs) were the main targets of miRNAs in the regulation of autophagy-mediated CDDP response in tumor cells. This review can be an effective step to introduce the miRNAs as efficient therapeutic options to increase autophagy-mediated CDDP sensitivity in tumor cells.

Autophagy as a self-digestion signal in human cancers: Regulation by microRNAs in affecting carcinogenesis and therapy response

Autophagy is defined as a "self-digestion" signal, and it is a cell death mechanism its primary function is degrading toxic agents and aged organelles to ensure homeostasis in cells. The basic leve ls of autophagy are found in cells, and when its levels exceed to standard threshold, cell death induction is observed. Autophagy dysregulation in cancer has been well-documented, and regulation of this pathway by epigenetic factors, especially microRNAs (miRNAs), is interesting and noteworthy. miRNAs are considered short endogenous RNAs that do not encode functional proteins, and they are essential regulators of cell death pathways such as apoptosis, necroptosis, and autophagy. Accumulating data has revealed miRNA dysregulation (upregulation or downregulation) during tumor progression, and their therapeutic manipulation provides new insight into cancer therapy. miRNA/autophagy axis in human cancers has been investigated an exciting point is the dual function of both autophagy and miRNAs as oncogenic and onco-suppressor factors. The stimulation of pro-survival autophagy by miRNAs can increase the survival rate of tumor cells and mediates cancer metastasis via EMT inductionFurthermore, pro-death autophagy induction by miRNAs has a negative impact on the viability of tumor cells and decreases their survival rate. The miRNA/autophagy axis functions beyond regulating the growth and invasion of tumor cells, and they can also affect drug resistance and radio-resistance. These subjects are covered in the current review regarding the new updates provided by recent experiments.

The regulation of autophagy by the miR-199a-5p/p62 axis was a potential mechanism of small cell lung cancer cisplatin resistance

BACKGROUND

Autophagy has been found to be involved in the multidrug resistance (MDR) of cancers, but whether it is associated with resistance of small cell lung cancer (SCLC) has not been studied. Here, we hypothesized that a potential autophagy-regulating miRNA, miR-199a-5p, regulated cisplatin-resistant SCLC.

METHODS

We validated the MDR of H446/EP using CCK-8 and LDH. We tested the binding of miR-199a-5p to p62 using the Dual-Luciferase assay and validated the association of miR-199a-5p and p62 in SCLC samples. We overexpressed (OE) and knocked down (KD) miR-199a-5p in H446 and H446/EP and determined the expression of miR-199a-5p, autophagy-related proteins, and the formation of autophagolysosomes using QPCR, western blotting, and MDC staining respectively. These results were validated in an orthotopic H446 mouse model of SCLC.

RESULTS

H446/EP was resistant to cisplatin, etoposide, paclitexal, epirubicin, irinotecan, and vinorelbine. Exposure of cisplatin at 5 μg/ml for 24 h increased LC3II/LC3I, ATG5, p62, and the formation of autophagolysosomes in H446 cells, but not in H446/EP cells. The expression of miR-199a-5p was up-regulated in H446/EP compared to H446. MiR-199a-5p directly targeted the p62 gene. The expression of miR-199a-5p and p62 were correlated in SCLC samples. In H446 and H69PR, the OE of miR-199a-5p increased LC3II/LC3I, p62, and the formation of autophagolysosomes, but not ATG5, while the KD of miR-199a-5p decreased p62, but did not affect LC3II/LC3I, ATG5, and the formation of autophagolysosomes. In H446/EP, the OE of miR-199a-5p decreased p62 only. These results were generally consistent to results in the animal tumor samples.

CONCLUSIONS

The regulation of autophagy by the miR-199a-5p/p62 axis was a potential mechanism of small cell lung cancer cisplatin resistance.

The MicroRNA-Based Strategies to Combat Cancer Chemoresistance via Regulating Autophagy

Chemoresistance frequently occurs in cancer treatment, which results in chemotherapy failure and is one of the most leading causes of cancer-related death worldwide. Understanding the mechanism of chemoresistance and exploring strategies to overcome chemoresistance have become an urgent need. Autophagy is a highly conserved self-degraded process in cells. The dual roles of autophagy (pro-death or pro-survival) have been implicated in cancers and chemotherapy. MicroRNA (miRNA) is a class of small non-coding molecules that regulate autophagy at the post-transcriptional level in cancer cells. The association between miRNAs and autophagy in cancer chemoresistance has been emphasized. In this review, we focus on the dual roles of miRNA-mediated autophagy in facilitating or combating chemoresistance, aiming to shed lights on the potential role of miRNAs as targets to overcome chemoresistance.

Research Progress of Exosome-Loaded miRNA in Osteosarcoma

Currently, although the improvement of surgical techniques and the development of chemotherapy drugs have brought a certain degree of development to the treatment of osteosarcoma, the treatment of osteosarcoma has many shortcomings, and its treatment is limited. MiRNAs and exosomes can be used as diagnostic tools, and they play an important role in the occurrence and chemotherapy resistance of osteosarcoma. Therefore, providing a new method for the treatment of osteosarcoma is the key to solving this problem. To systematically summarize the research status of exoskeleton drug-loaded miRNA in osteosarcoma, we identified and evaluated 208 studies and found that exosome-carrying miRNA can be used as an index for the diagnosis and prognosis of osteosarcoma and share a certain relationship with chemosensitivity. In addition, exosomes can also be used as a carrier of genetic drugs able to regulate the progression of osteosarcoma. Based on the above findings, we propose suggestions for the future development of this field, aiming to bring new ideas for the early diagnosis and treatment of osteosarcoma.

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.

Autophagy inhibition and microRNA‑199a‑5p upregulation in paclitaxel‑resistant A549/T lung cancer cells

Multidrug resistance (MDR) is one of the major reasons for the clinical failure of cancer chemotherapy. Autophagy activation serves a crucial role in MDR. However, the specific molecular mechanism linking autophagy with MDR remains unknown. The results of the present study demonstrated that autophagy was inhibited and microRNA (miR)-199a-5p levels were upregulated in MDR model lung cancer cells (A549/T and H1299/T) compared with those in the parental cell lines. Paclitaxel (PTX) treatment increased the expression levels of miR-199a-5p in parental lung cancer cells compared with those in PTX-untreated cells, and these expression levels were negatively correlated with PTX sensitivity of the cells. miR-199a-5p knockdown in A549/T cells induced autophagy and resensitized cells to multiple chemotherapeutic drugs including PTX, taxotere, topotecan, SN38, oxaliplatin and vinorelbine. By contrast, miR-199a-5p overexpression in A549 cells suppressed autophagy and desensitized cells to these chemotherapeutic drugs. Mechanistically, the results of the present study demonstrated that miR-199a-5p blocked autophagy by activating the PI3K/Akt/mTOR signaling pathway and inhibiting the protein expression of autophagy-related 5. Furthermore, p62 protein was identified as a direct target of miR-199a-5p; miR-199a-5p bound to p62 mRNA to decrease its mRNA and protein expression levels. In conclusion, the results of the present study suggested that miR-199a-5p may contribute to MDR development in lung cancer cells by inhibiting autophagy and targeting p62. The regulatory effect of miR-199a-5p on autophagy may provide novel insights for future multidrug-resistant lung cancer chemotherapy.

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.

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.

MicroRNA-mediated autophagy regulation in cancer therapy: The role in chemoresistance/chemosensitivity

Chemoresistance has doubled the effort needed to reach an effective treatment for cancer. Now, scientists should consider molecular pathways and mechanisms involved in chemoresistance to overcome cancer. Autophagy is a "self-digestion" mechanism in which potentially toxic and aged organelles and macromolecules are degraded. Increasing evidence has shown that autophagy possesses dual role in cancer cells (onco-suppressor or oncogene). So, it is vital to identify its role in cancer progression and malignancy. MicroRNAs (miRs) are epigenetic factors capable of modulation of autophagy in cancer cells. In the current review, we emphasize on the relationship between miRs and autophagy in cancer chemotherapy. Besides, we discuss upstream mediators of miR/autophagy axis in cancer chemotherapy including long non-coding RNAs, circular RNAs, Nrf2 c-Myc, and HIF-1α. At the final section, we provide a discussion about how anti-tumor compounds affect miR/autophagy axis in ensuring chemosensitivity. These topics are described in this review to show how autophagy inhibition/induction can lead to chemosensitivity/chemoresistance, and miRs are considered as key players in these discussions.

Autophagy-mediating microRNAs in cancer chemoresistance

Chemoresistance is a complex phenomenon responsible for failure in response to chemotherapy agents and more than 90% of deaths in cancer patients. MicroRNAs (miRNAs), as a subgroup of non-coding RNAs with lengths between 21 and 25 nucleotides, are involved in various cancer processes like chemoresistance via interacting with their target mRNAs and suppressing their expression. Autophagy is a greatly conserved procedure involving the lysosomal degradation of cytoplasmic contents and organelles to deal with environmental stresses like hypoxia and starvation. Autophagy contributes to response to chemotherapy agents: autophagy can act as a protective mechanism for mediating the resistance in response to chemotherapy or can induce autophagic cell death and mediate the sensitivity to chemotherapy. On the other hand, one of the processes targeted by microRNAs in the regulation of chemoresistance is autophagy. Hence, we studied the literatures on chemoresistance mechanisms, the miRNAs' role in cancer, and the miRNAs' role in chemoresistance by modulating autophagy. Graphical Abstract.

Autophagy regulation by microRNAs: Novel insights into osteosarcoma therapy

Osteosarcoma (OS) is a kind of primary bone cancer that is considered as the leading cause of children death. Surgery and chemotherapy are considered as common treatment approaches for OS; the rate of survival for patients is almost 60-70%. Besides the used therapeutic approaches, it seems that there is a crucial need to launch new treatments for OS. In this regard, more understanding about cellular and molecular pathways involved in OS can contribute to recovery and develop new therapeutic platforms. Autophagy is a cellular machinery that digests and degrades dysfunctional proteins and organelles, so it can regulate the cell proliferation and survival. Most of the time, OS cells use autophagy to increase their survival and proliferation and to gain the ability to resist chemotherapy. Although, there are several controversial evidences on how OS cells use autophagy. A variety of cellular and molecular pathways, that is, microRNAs (miRNAs) can modulate autophagy. MiRNAs are some endogenous, approximately 22 nucleotide RNAs that have an important role in posttranscriptional regulation of mRNAs by targeting them. There are many evidences that the various miRNA expressions in OS cells are dysregulated, so it can propel a normal cell to cancerous one by influencing the cell survival, apoptosis, and autophagy, and eventually increased chemoresitance. Hence, miRNAs can be considered as new biomarkers for OS diagnosis, and according to the role of autophagy in OS progression, miRNAs can use inhibiting or promoting autophagy agents. The present review summarizes the effects of aberrant expression of miRNAs in OS diagnosis and treatment with focus on their roles in autophagy.

CircMUC16 promotes autophagy of epithelial ovarian cancer via interaction with ATG13 and miR-199a

BACKGROUND

Circular RNA (circRNA) has been proven to play a significant role in multiple types of cancer. However, the expression and role of circRNAs in epithelial ovarian cancer (EOC) remains elusive.

METHODS

CircRNA and mRNA expression profiles of EOC were screened with sequencing analysis. Gene silencing and over-expression were used to study circRNA function. Cell proliferation and Matrigel invasion assays were used to detect cell proliferation and invasion, respectively. The expression of circRNAs, mRNAs and miRNAs was detected using qPCR. The location of circRNAs was detected using FISH. The expression of proteins was detected using western blot and immunohistochemistry.

RESULTS

CircMUC16 had increased expression in EOC tissues as compared to healthy ovarian tissues. The expression of circMUC16 was linked to the progression in stage and grade of EOC. Hence, silencing circMUC16 suppressed autophagy flux of SKOV3 cells. In contrast, ectopic expression of circMUC16 promoted autophagy flux of A2780 cells. CircMUC16-mediated autophagy exacerbated EOC invasion and metastasis. Mechanistically, circMUC16 could directly bind to miR-199a-5p and relieve suppression of target Beclin1 and RUNX1. In turn, RUNX1 elevated the expression of circMUC16 via promotion of its transcription. CircMUC16 could directly bind to ATG13 and promote its expression.

CONCLUSION

This study demonstrated that circMUC16 regulated Beclin1 and RUNX1 by sponging miR-199a-5p. The data suggested that circMUC16 could be a potential target for EOC diagnosis and therapy.

Role of miR-199a-5p in osteoblast differentiation by targeting TET2

OBJECTIVE

miR-199a-5p was increased during osteoblast differentiation, which may target and regulate TET2, a gene attracted a lot of attention in the osteoblast differentiation in the past few years. However, the role of miR-199a-5p in osteoblast differentiation by targeting TET2 is not established.

METHODS

The correlation between miR-199a-5p and TET2 was verified through dual luciferase reporter assay, and their expressions in human bone marrow stromal cells (hBMSCs) during the osteoblast differentiation were detected. hBMSCs were transfected with TET2 siRNA, miR-199a-5p mimic or/and TET2 CRISPR activation plasmid., and then prepared for the induction of osteoblast differentiation, followed by alkaline phosphatase (ALP) and alizarin red staining, qRT-PCR and Western blotting. In vivo, ovariectomized (OVX) mice were injected with agomir-miR-199a-5p, antagomiR-199a-5p or/and TET2 siRNA to calculate the BMD and BV/TV ratio of mice, as well as to measure the expressions of osteogenesis-related genes in bone tissues.

RESULTS

A gradual increase of miR-199a-5p was observed in hBMSCs during the induction of osteoblast differentiation, while TET2 expression was decreased. Besides, miR-199a-5p was reduced in the bone tissue of OVX mice, while TET2 was up-regulated. In addition, overexpression of miR-199a-5p and inhibition of TET2 augmented ALP activity in hBMSCs, with the enhanced calcification and the up-regulated expressions of Runx2, OSX and OCN, which also increased the quality of bone in OVX mice accompanying the enhancement BV/TV ratio, BMD and osteogenesis-related genes.

CONCLUSION

MiR-199a-5p may promote the osteoblast differentiation and prevent OVX-induced osteoporosis by targeting TET2.

miRNA signatures in childhood sarcomas and their clinical implications

Progresses in multimodal treatments have significantly improved the outcomes for childhood cancer. Nonetheless, for about one-third of patients with Ewing sarcoma, rhabdomyosarcoma, or osteosarcoma steady remission has remained intangible. Thus, new biomarkers to improve early diagnosis and the development of precision-targeted medicine remain imperative. Over the last decade, remarkable progress has been made in the basic understanding of miRNAs function and in interpreting the contribution of their dysregulation to cancer development and progression. On this basis, this review focuses on what has been learned about the pivotal roles of miRNAs in the regulation of key genes implicated in childhood sarcomas.

Insight Into the Role of Autophagy in Osteosarcoma and Its Therapeutic Implication

Osteosarcoma is an aggressive bone cancer that frequently metastasizes to the lungs. The cytotoxicity of most chemotherapeutics and targeted drugs in the treatment of osteosarcoma is partially lessened. Furthermore, there is a poor response to current chemo- and radiotherapy for both primary lesions and pulmonary metastases of osteosarcoma. There is a clear need to explore promising drug candidates that could improve the efficacy of osteosarcoma treatment. Autophagy, a dynamic and highly conserved catabolic process, has dual roles in promoting cell survival as well as cell death. The role of autophagy has been investigated extensively in different tumor types, and a growing body of research has highlighted the potential value of using autophagy in clinical therapy. Here, we address significant aspects of autophagy in osteosarcoma, including its functions, modulation, and possible therapeutic applications.

Targeting autophagy is a promising therapeutic strategy to overcome chemoresistance and reduce metastasis in osteosarcoma

Osteosarcoma (OS) is the most common primary bone malignancy, mainly affecting children and adolescents. Currently, surgical resection combined with adjuvant chemotherapy has been standardized for OS treatment. Despite great advances in chemotherapy for OS, its clinical prognosis remains far from satisfactory; this is due to chemoresistance, which has become a major obstacle to improving OS treatment. Autophagy, a catabolic process through which cells eliminate and recycle their own damaged proteins and organelles to provide energy, can be activated by chemotherapeutic drugs. Accumulating evidence has indicated that autophagy plays the dual role in the regulation of OS chemoresistance by either promoting drug resistance or increasing drug sensitivity. The aim of the present review was to demonstrate thatautophagy has both a cytoprotective and an autophagic cell death function in OS chemoresistance. In addition, methods to detect autophagy, autophagy inducers and inhibitors, as well as autophagy‑mediated metastasis, immunotherapy and clinical prognosis are also discussed.

Interaction among inflammasome, autophagy and non-coding RNAs: new horizons for drug

Autophagy and inflammasomes are shown to interact in various situations including infectious disease, cancer, diabetes and neurodegeneration. Since multiple layers of molecular regulators contribute to the interplay between autophagy and inflammasome activation, the detail of such interplay remains largely unknown. Non-coding RNAs (ncRNAs), which have been implicated in regulating an expanding list of cellular processes including immune defense against pathogens and inflammatory response in cancer and metabolic diseases, may join in the crosstalk between inflammasomes and autophagy in physiological or disease conditions. In this review, we summarize the latest research on the interlink among ncRNAs, inflammasomes and autophagy and discuss the emerging role of these three in multiple signaling transduction pathways involved in clinical conditions. By analyzing these intriguing interconnections, we hope to unveil the mechanism inter-regulating these multiple processes and ultimately discover potential drug targets for some refractory diseases.

miR-199a-5p Represses Protective Autophagy and Overcomes Chemoresistance by Directly Targeting DRAM1 in Acute Myeloid Leukemia

Chemotherapy resistance is still a primary clinical obstacle to the successful treatment of acute myeloid leukemia (AML). The underlying mechanisms of drug resistance are complicated and have not been fully understood. Here, we found that miR-199a-5p levels were significantly reduced in refractory/relapsed AML patients compared to those who achieved complete remission after chemotherapy. Consistently, miR-199a-5p was markedly decreased in Adriamycin-resistant AML K562/ADM cells in contrast with Adriamycin-sensitive K562 cells, and its decrement dramatically correlated with the chemoresistance of AML cells. Furthermore, we demonstrated that the basic and Adriamycin-induced autophagic activity in K562/ADM cells was higher than that in K562 cells. This inducible autophagy played a prosurvival role and contributed to the development of acquired drug resistance. Importantly, we investigated that miR-199a-5p could negatively regulate autophagy, at least in part, by inhibiting damage regulator autophagy modulator (DRAM1) expression at both the transcriptional and posttranscriptional level. miR-199a-5p bound directly to the 3'-UTR of DRAM1 mRNA which was a functional target of miR-199a-5p. Indeed, downregulation of DRAM1 gene by siRNA in K562/ADM cells resulted in autophagy suppression and chemosensitivity restoration. These results revealed that the miR-199a-5p/DRAM1/autophagy signaling represented a novel pathway regulating chemoresistance, indicating a potential therapeutic strategy for the intervention in drug-resistant AML.

Downregulation of BAG3 attenuates cisplatin resistance by inhibiting autophagy in human epithelial ovarian cancer cells

Epithelial ovarian cancer (EOC) is one of the most common malignant gynecological tumors. Interval cytoreductive surgery and cisplatin-based chemotherapy are the standard treatments. However, acquired resistance to cisplatin presents a major challenge for improving the overall survival and prognosis of patients. Recent evidence indicates that cytoprotective functions of autophagy in cancer cells is a potential mechanism for chemoresistance. The present study aimed to investigate the mechanisms responsible for cisplatin resistance in EOC cell lines. The results revealed that cisplatin activated autophagy, measured by an increase in the expression of LC3-II by western blot analysis, protecting ovarian cancer cells from cisplatin toxicity. The present study also identified Bcl-2-associated athanogene 3 (BAG3) as a novel autophagy regulator that serves a role in cisplatin resistance. Treatment with cisplatin was observed to enhance BAG3 expression in parental and cisplatin-resistant ovarian cancer cell lines, and the downregulation of BAG3 blocked cisplatin-induced autophagy, thereby increasing cisplatin sensitivity in the EOC cell lines. In conclusion, BAG3 attenuates cisplatin resistance by inhibiting autophagy, suggesting that downregulation of BAG3 may be a useful therapeutic strategy to overcome cisplatin resistance by preventing cytoprotective autophagy in EOC.

Low‑intensity ultrasound enhances the chemosensitivity of hepatocellular carcinoma cells to cisplatin via altering the miR‑34a/c‑Met axis

Recently, the use of low-intensity ultrasound (LIUS) combined with chemotherapeutic agents is widely used in clinical practice, mainly for the treatment of cancer; however, the mechanisms as to how LIUS enhances the antitumor effects of these agents are not fully understood. The aim of the present study was to explore the synergistic antitumor effects and mechanisms of cisplatin (DDP) combined with LIUS (LIUS-DDP) in hepatocellular carcinoma (HCC). We reported that LIUS effectively enhanced Huh7 and HCCLM3 cell sensitivity to a low concentration of DDP. Reverse transcription-quantitative polymerase chain reaction analysis revealed that LIUS could increase the expression of microRNA-34a (miR-34a) in HCC cells following DDP treatment. In addition, LIUS-DDP significantly increased intracellular reactive oxygen species (ROS) levels in vitro, and the upregulation of miR-34a induced by LIUS-DDP was reversed by the ROS scavenger N-acetylcysteine, suggesting that LIUS upregulates the expression of miR-34a via production of ROS. In addition, knockdown of miR-34a in HCC cells significantly suppressed the synergistic effects of LIUS-DDP treatment. Conversely, overexpression of miR-34a enhanced these synergistic effects. The results of a dual-luciferase assay indicated that c-Met, a well-known oncogene, was a target of miR-34a. We also determined that LIUS-DDP treatment inhibited the expression of c-Met, possibly due to increased ROS production, which upregulated miR-34a expression. Furthermore, overexpression of c-Met reversed the synergistic effects of LIUS-DDP treatment. Our findings suggest that LIUS could enhance the chemosensitivity of HCC cells to DDP by altering the miR-34a/c-Met axis. Therefore, DDP combined with LIUS may be a potential therapeutic application for the clinical treatment of patients with HCC.

Drug resistance-related microRNAs in osteosarcoma: Translating basic evidence into therapeutic strategies

Although the application of multiple chemotherapy brought revolutionary changes to improve overall survival of osteosarcoma patients, the existence of multidrug resistance (MDR) has become a great challenge for successful osteosarcoma treatment in recent decades. Substantial studies have revealed various underlying mechanisms of MDR in cancers. As for osteosarcoma, evidence has highlighted that microRNAs (miRNAs) can mediate in the processes of DNA damage response, apoptosis avoidance, autophagy induction, activation of cancer stem cells, and signal transduction. Besides, these drug resistance‐related miRNAs showed much promise for serving as candidates for predictive biomarkers of poor outcomes and shorter survival time, and therapeutic targets to reverse drug resistance and overcome treatment refractoriness. This review aims to demonstrate the potential molecular mechanisms of miRNAs‐regulated drug resistance in osteosarcoma, and provide insight in translating basic evidence into therapeutic strategies.

MicroRNA-504 modulates osteosarcoma cell chemoresistance to cisplatin by targeting p53

Chemoresistance implicates the therapeutic value of cisplatin and remains a primary obstacle to its clinical use. MicroRNAs (miRs) negatively modulate the expression of their target genes and are associated with the occurrence and progression of various types of tumor. The abnormal expression of miR-504 has been reported in certain types of human tumor and has been associated with tumor prognosis. However, the association between miR-504 and cisplatin in human osteosarcoma remains unclear. The present study therefore aimed to assess the in vitro effects and possible mechanism of miR-504 in cell proliferation, apoptosis and cisplatin resistance in MG63 osteosarcoma cells. The results demonstrated that miR-504 was overexpressed in osteosarcoma tissues and cells. This overexpression also induced cell proliferation, as determined by MTT and EdU staining assays. Furthermore, miR-504 suppressed cisplatin-induced apoptosis, which was demonstrated via MTT, cell morphology analysis and flow cytometry. Cisplatin-induced G₁ arrest was also suppressed, which was determined by flow cytometry. The potential target genes of miR-504 were predicted using bioinformatics. p53 was confirmed to be a direct target of miR-504 using a luciferase reporter assay and western blot analysis revealed that miR-504 negatively regulated p53 expression at a molecular level. These results indicate that miR-504 contributes to cisplatin resistance in MG63 osteosarcoma cells by suppressing p53. miR-504 may therefore be a potential biomarker for cisplatin resistance in patients with osteosarcoma.

CCN2 promotes drug resistance in osteosarcoma by enhancing ABCG2 expression

In recent years, osteosarcoma survival rates have failed to improve significantly with conventional treatment modalities because of the development of chemotherapeutic resistance. The human breast cancer resistance protein/ATP binding cassette subfamily G member 2 (BCRP/ABCG2), a member of the ATP-binding cassette family, uses ATP hydrolysis to expel xenobiotics and chemotherapeutics from cells. CCN family member 2 (CCN2) is a secreted protein that modulates the biological function of cancer cells, enhanced ABCG2 protein expression and activation in this study via the α6β1 integrin receptor and increased osteosarcoma cell viability. CCN2 treatment downregulated miR-519d expression, which promoted ABCG2 expression. In a mouse xenograft model, knockdown of CCN2 expression increased the therapeutic effect of doxorubicin, which was reversed by ABCG2 overexpression. Our data show that CCN2 increases ABCG2 expression and promotes drug resistance through the α6β1 integrin receptor, whereas CCN2 downregulates miR-519d. CCN2 inhibition may represent a new therapeutic concept in osteosarcoma.

Overexpression of microRNA-506-3p aggravates the injury of vascular endothelial cells in patients with hypertension by downregulating Beclin1 expression

The aim of the present study was to measure the expression of microRNA (miRNA)-506-3p in the peripheral blood of patients with hypertension and to determine the biological functions and mechanisms of action of miR-506-3p. A total of 61 patients with primary hypertension were included in the present study. Peripheral blood was collected from all patients, as well as 31 healthy subjects who were included in a control group. The expression of miR-506-3p in peripheral blood was determined by reverse transcription-quantitative polymerase chain reaction. Human umbilical vein endothelial cells (HUVECs) were transfected with miR-506-3p mimics or miR-506-3p inhibitor. The proliferation and migration of HUVECs were determined using cell-counting kit 8 and Transwell assays, respectively. The cell cycle and apoptosis of HUVECs were detected by flow cytometry. The expression of Beclin1 (BECN1) protein, a potential target of miR-506-3p, was measured using western blotting. A dual-luciferase reporter assay was performed to determine the interaction between BECN1 and miR-506-3p. It was demonstrated that miR-506-3p expression in the peripheral blood of patients with patients was upregulated and dependent on the severity of hypertension. miR-506-3p overexpression inhibited the proliferation and migration of HUVECs. In addition, miR-506-3p inhibited the transition from the G1 phase to the S-phase in HUVECs. Overexpression of miR-506-3p promoted the apoptosis of HUVECs. Notably, miR-506-3p downregulated the expression of BECN1 by directly binding to its 3′-untranslated region. The present study demonstrated that miR-506-3p expression is elevated in the peripheral blood of patients with hypertension and is associated with the severity of hypertension. By downregulating BECN1 expression, miR-506-3p aggravates injury in vascular endothelial cells by inhibiting the proliferation and migration of HUVECs, as well as promoting their apoptosis.

MicroRNA expression profiles in non‑epithelial ovarian tumors

Ovarian germ cell tumors (OGCTs) and sex cord stromal tumors (SCSTs) are rare gynecologic tumors that are derived from germ and stromal cells, respectively. Unlike their epithelial counterparts, molecular pathogenesis of these tumor types is still poorly understood. Here, we characterized microRNA (miRNA) expression profiles of 9 OGCTs (2 malignant and 7 benign) and 3 SCSTs using small RNA sequencing. We observed significant miRNA expression variations among the three tumor groups. To further demonstrate the biological relevance of our findings, we selected 12 miRNAs for validation in an extended cohort of 16 OGCTs (9 benign and 7 malignant) and 7 SCSTs by reverse transcription-quantitative polymerase chain reaction. Higher expression of miR‑373‑3p, miR‑372‑3p and miR‑302c‑3p and lower expression of miR‑199a‑5p, miR‑214‑5p and miR‑202‑3p were reproducibly observed in malignant OGCTs as compared to benign OGCTs or SCSTs. Comparing with benign OGCTs, miR‑202c‑3p and miR‑513c‑5p were more abundant in SCSTs. Additionally, we examined Beclin 1 (BECN1), a target of miR‑199a‑5p, in the clinical samples using western blot analysis. Our results show that BECN1 expression was higher in malignant OGCTs than benign OGCTs, which is concordant with their lower miR‑199a‑5p expression. This study suggests that these miRNAs may have potential value as tumor markers and implications for further understanding the molecular basis of these tumor types.

Novel strategies to prevent the development of multidrug resistance (MDR) in cancer

The development of multidrug resistance (MDR) is one of the major challenges to the success of traditional chemotherapy treatment in cancer patients. Most studies to date have focused on strategies to reverse MDR following its development. However, agents utilizing this approach have proven to be of limited clinical use, failing to demonstrate an improvement in therapeutic efficacy with almost no significant survival benefits observed in cancer clinical trials. An alternative approach that has been applied is to prevent or delay MDR prior or early in its development. Recent investigations have shown that preventing the emergence of MDR at the onset of chemotherapy treatment, rather than reversing MDR once it has developed, may assist in overcoming drug resistance. In this review, we focus on a number of novel strategies used by small-molecule inhibitors to prevent the development of MDR. These agents hold great promise for prolonging the efficacy of chemotherapy treatment and improving the clinical outcomes of patients with cancers that are susceptible to MDR development.

Noncoding RNA in drug resistant sarcoma

Sarcomas are a group of malignant tumors that arise from mesenchymal origin. Despite significant development of multidisciplinary treatments for sarcoma, survival rates have reached a plateau. Chemotherapy has been extensively used for sarcoma treatment; however, the development of drug resistance is a major obstacle limiting the success of many anticancer agents. Sarcoma biology has traditionally focused on genomic and epigenomic deregulation of protein-coding genes to identify the therapeutic potential for reversing drug resistance. New and more creative approaches have found the involvement of noncoding RNAs, including microRNAs and long noncoding RNAs in drug resistant sarcoma. In this review, we discuss the current knowledge of noncoding RNAs characteristics and the regulated genes involved in drug resistant sarcoma, and focus on their therapeutic potential in the future.

miR-382 functions as a tumor suppressor against esophageal squamous cell carcinoma

AIM

To explore the effect of miR-382 on esophageal squamous cell carcinoma (ESCC) in vitro and its possible molecular mechanism.

METHODS

Eca109 cells derived from human ESCC and Het-1A cells derived from human normal esophageal epithelium were used. Lentivirus-mediated miR-382 was overexpressed in Eca109 cells. The effect of miR-382 on cell proliferation was evaluated by MTT and colony formation assay. For cell cycle analysis, cells were fixed and stained for 30 min with propidium iodide (PI) staining buffer containing 10 mg/mL PI and 100 mg/mL RNase A, and analyzed by BD FACSCalibur™ flow cytometer. For cell apoptosis assay, cells were stained with an Annexin V-FITC/PI Apoptosis Detection Kit according to the manufacturer’s instructions and analyzed by a dual-laser flow cytometer. Cell invasion and migration abilities were determined through use of transwell chambers, non-coated or pre-coated with matrigel. Levels of proteins related to cell growth and migration were examined by western blotting.

RESULTS

Endogenous miR-382 was down-regulated in Eca109 cells compared with Het-1A. Introduction of miR-382 not only significantly inhibited proliferation and colony formation, but also arrested cell cycle at the G2/M phase, as well as promoted apoptosis and autophagy in Eca109 cells. Migration, invasion and epithelial-mesenchymal transition of Eca109 cells were suppressed by overexpressing miR-382. Western blotting results showed that miR-382 inhibited the phosphorylation of mTOR and 4E-BP1.

CONCLUSION

miR-382 functions as a tumor suppressor against ESCC development and metastasis, and could be considered as a potential drug source for the treatment of ESCC patients.

CLDN1 Increases Drug Resistance of Non-Small Cell Lung Cancer by Activating Autophagy via Up-Regulation of ULK1 Phosphorylation

BACKGROUND The aim of this study was to investigate the expression of CLDN1 in non-small cell lung cancer (NSCLC) and its mechanism of action in cisplatin resistance. MATERIAL AND METHODS A total of 55 patients with NSCLC admitted to our hospital between October 2013 and October 2015 were included. NSCLC tissues and tumor-adjacent tissues (≥5 cm from tumor edge) were collected. Among the 55 patients, 37 had adenocarcinoma and 18 had squamous cell carcinoma. Quantitative real-time polymerase chain reaction was used to determine mRNA expression, and protein expression was examined using Western blotting. CCK-8 assay was used to determine cell proliferation and Transwell assay was used to detect migration and invasion of the cells. Confocal microscopy was used to observe autophagosomes. RESULTS Increased CLDN1 expression promoted the development and metastasis of NSCLC. CLDN1 expression in A549/CDDP cells was up-regulated at both transcriptional and translational levels. Reduced CLDN1 expression decreased the drug resistance, proliferation, migration, and invasion abilities of A549/CDDP cells. Decreased CLDN1 expression promoted the apoptosis of A549/CDDP cells. CLDN1 enhanced CDDP drug resistance of A549 cells by activating autophagy. CLDN1 promoted the autophagy of A549 cells by up-regulating the phosphorylation level of ULK1. CONCLUSIONS The present study demonstrates that expression of CLDN1 in NSCLC is up-regulated and it is correlated with clinicopathological features. CLDN1 activates autophagy through up-regulation of ULK1 phosphorylation and promotes drug resistance of NSCLC cells to CDDP.