Characterization of multidrug-resistant osteosarcoma sublines and the molecular mechanisms of resistance

LncRNA Miat knockdown enhances pirarubicin-mediated anticancer sensitivity in breast cancer cells

Pirarubicin (THP) is a widely used antitumor agent in clinical practice, but its reduced sensitivity during treatment has limited its use. The aim of this study was to investigate the role and mechanism of LncRNA Miat knockdown in improving THP sensitivity. We assessed the role of Miat overexpression/knockdown on THP-mediated 4T1 anticancer activity by CCK8, TUNEL, flow cytometry, wound healing assay, Transwell, Ca2+ , real time quantitative PCR (RT-qPCR) and Western blot. The results showed that Miat expression was higher in 4T1 mouse breast cancer cells than in HC11 mouse mammary epithelial cells, while THP decreased Miat expression in 4T1. Miat knockdown in combination with further reduced cell viability, promoted apoptosis and inhibited migration compared to THP alone. This may be related to the reduction of calcium ions in 4T1. In conclusion, Miat knockdown enhanced the sensitivity of THP to 4T1 by inhibiting calcium channels.

LIM Kinases, LIMK1 and LIMK2, Are Crucial Node Actors of the Cell Fate: Molecular to Pathological Features

LIM kinase 1 (LIMK1) and LIM kinase 2 (LIMK2) are serine/threonine and tyrosine kinases and the only two members of the LIM kinase family. They play a crucial role in the regulation of cytoskeleton dynamics by controlling actin filaments and microtubule turnover, especially through the phosphorylation of cofilin, an actin depolymerising factor. Thus, they are involved in many biological processes, such as cell cycle, cell migration, and neuronal differentiation. Consequently, they are also part of numerous pathological mechanisms, especially in cancer, where their involvement has been reported for a few years and has led to the development of a wide range of inhibitors. LIMK1 and LIMK2 are known to be part of the Rho family GTPase signal transduction pathways, but many more partners have been discovered over the decades, and both LIMKs are suspected to be part of an extended and various range of regulation pathways. In this review, we propose to consider the different molecular mechanisms involving LIM kinases and their associated signalling pathways, and to offer a better understanding of their variety of actions within the physiology and physiopathology of the cell.

The strategy and clinical relevance of in vitro models of MAP resistance in osteosarcoma: a systematic review

Over the last 40 years osteosarcoma (OS) survival has stagnated with patients commonly resistant to neoadjuvant MAP chemotherapy involving high dose methotrexate, adriamycin (doxorubicin) and platinum (cisplatin). Due to the rarity of OS, the generation of relevant cell models as tools for drug discovery is paramount to tackling this issue. Four literature databases were systematically searched using pre-determined search terms to identify MAP resistant OS cell lines and patients. Drug exposure strategies used to develop cell models of resistance and the impact of these on the differential expression of resistance associated genes, proteins and non-coding RNAs are reported. A comparison to clinical studies in relation to chemotherapy response, relapse and metastasis was then made. The search retrieved 1891 papers of which 52 were relevant. Commonly, cell lines were derived from Caucasian patients with epithelial or fibroblastic subtypes. The strategy for model development varied with most opting for continuous over pulsed chemotherapy exposure. A diverse resistance level was observed between models (2.2-338 fold) with 63% of models exceeding clinically reported resistance levels which may affect the expression of chemoresistance factors. In vitro p-glycoprotein overexpression is a key resistance mechanism; however, from the available literature to date this does not translate to innate resistance in patients. The selection of models with a lower fold resistance may better reflect the clinical situation. A comparison of standardised strategies in models and variants should be performed to determine their impact on resistance markers. Clinical studies are required to determine the impact of resistance markers identified in vitro in poor responders to MAP treatment, specifically with respect to innate and acquired resistance. A shift from seeking disputed and undruggable mechanisms to clinically relevant resistance mechanisms may identify key resistance markers that can be targeted for patient benefit after a 40-year wait.

Delivery of mGluR5 siRNAs by Iron Oxide Nanocages by Alternating Magnetic Fields for Blocking Proliferation of Metastatic Osteosarcoma Cells

Although osteosarcoma is the most common primary malignant bone tumor, chemotherapeutic drugs and treatment have failed to increase the five-year survival rate over the last three decades. We previously demonstrated that type 5 metabotropic glutamate receptor, mGluR5, is required to proliferate metastatic osteosarcoma cells. In this work, we delivered mGluR5 siRNAs in vitro using superparamagnetic iron oxide nanocages (IO-nanocages) as delivery vehicles and applied alternating magnetic fields (AMFs) to improve mGluR5 siRNAs release. We observed functional outcomes when mGluR5 expression is silenced in human and mouse osteosarcoma cell lines. The results elucidated that the mGluR5 siRNAs were successfully delivered by IO-nanocages and their release was enhanced by AMFs, leading to mGluR5 silencing. Moreover, we observed that the proliferation of both human and mouse osteosarcoma cells decreased significantly when mGluR5 expression was silenced in the cells. This novel magnetic siRNA delivery methodology was capable of silencing mGluR5 expression significantly in osteosarcoma cell lines under the AMFs, and our data suggested that this method can be further used in future clinical applications in cancer therapy.

Addressing Doxorubicin Resistance in Bone Sarcomas Using Novel Drug-Resistant Models

Bone sarcomas have not shown a significant improvement in survival for decades, due, in part, to the development of resistance to current systemic treatments, such as doxorubicin. To better understand those mechanisms mediating drug-resistance we generated three osteosarcoma and one chondrosarcoma cell lines with a stable doxorubicin-resistant phenotype, both in vitro and in vivo. These resistant strains include a pioneer model generated from a patient-derived chondrosarcoma line. The resistant phenotype was characterized by a weaker induction of apoptosis and DNA damage after doxorubicin treatment and a lower migratory capability. In addition, all resistant lines expressed higher levels of ABC pumps; meanwhile, no clear trends were found in the expression of anti-apoptotic and stem cell-related factors. Remarkably, upon the induction of resistance, the proliferation potential was reduced in osteosarcoma lines but enhanced in the chondrosarcoma model. The exposure of resistant lines to other anti-tumor drugs revealed an increased response to cisplatin and/or methotrexate in some models. Finally, the ability to retain the resistant phenotype in vivo was confirmed in an osteosarcoma model. Altogether, this work evidenced the co-existence of common and case-dependent phenotypic traits and mechanisms associated with the development of resistance to doxorubicin in bone sarcomas.

Mechanisms of Resistance to Conventional Therapies for Osteosarcoma

Osteosarcoma (OS) is the most common primary bone tumor, mainly occurring in children and adolescents. Current standard therapy includes tumor resection associated with multidrug chemotherapy. However, patient survival has not evolved for the past decades. Since the 1970s, the 5-year survival rate is around 75% for patients with localized OS but dramatically drops to 20% for bad responders to chemotherapy or patients with metastases. Resistance is one of the biological processes at the origin of therapeutic failure. Therefore, it is necessary to better understand and decipher molecular mechanisms of resistance to conventional chemotherapy in order to develop new strategies and to adapt treatments for patients, thus improving the survival rate. This review will describe most of the molecular mechanisms involved in OS chemoresistance, such as a decrease in intracellular accumulation of drugs, inactivation of drugs, improved DNA repair, modulations of signaling pathways, resistance linked to autophagy, disruption in genes expression linked to the cell cycle, or even implication of the micro-environment. We will also give an overview of potential therapeutic strategies to circumvent resistance development.

Nanomedicine in osteosarcoma therapy: Micelleplexes for delivery of nucleic acids and drugs toward osteosarcoma-targeted therapies

Osteosarcoma(OS) represents the main cancer affecting bone tissue, and one of the most frequent in children. In this review we discuss the major pathological hallmarks of this pathology, its current therapeutics, new active biomolecules, as well as the nanotechnology outbreak applied to the development of innovative strategies for selective OS targeting. Small RNA molecules play a role as key-regulator molecules capable of orchestrate different responses in what concerns cancer initiation, proliferation, migration and invasiveness. Frequently associated with lung metastasis, new strategies are urgent to upgrade the therapeutic outcomes and the life-expectancy prospects. Hence, the prominent rise of micelleplexes as multifaceted and efficient structures for nucleic acid delivery and selective drug targeting is revisited here with special emphasis on ligand-mediated active targeting. Future landmarks toward the development of novel nanostrategies for both OS diagnosis and OS therapy improvements are also discussed.

Identification of differentially expressed genes in MG63 osteosarcoma cells with drug‑resistance by microarray analysis

Osteosarcoma is the most common type of primary malignant bone tumor, with extremely poor prognosis in patients with metastatic disease and resistance to therapy, such as multidrug regimens. The mechanisms of drug resistance are quite complex and have not been fully elucidated; thus, novel therapeutic targets should be identified to alleviate drug resistance in osteosarcoma. In the present study, the transcriptomes of the human osteosarcoma cell line MG63 and vincristine (VCR)-resistant MG63 cells were compared by microarray analysis. A total of 1,300 genes (602 upregulated and 698 downregulated) were reported to be differentially expressed in MG63/VCR compared with MG63 cells. Bioinformatics analysis predicted that the differentially expressed genes were mainly enriched in the B cell receptor, UVA-induced mitogen-activated protein kinases and receptor tyrosine kinase 2/3 signaling pathways. In the present study, 10 of the dysregulated genes, including roundabout homolog 1, death-associated protein kinase 1 and A-kinase anchor protein 12 were further evaluated by reverse transcription-quantitative polymerase chain reaction. These results may aid the validation of candidate biomarkers for the treatment and prognosis of osteosarcoma, and provide novel insight into the molecular mechanisms underlying the drug resistance of osteosarcoma cells.

LIM kinase 1 serves an important role in the multidrug resistance of osteosarcoma cells

Multidrug resistance (MDR) is a major challenge for the management of the majority of cancers. The precise molecular mechanisms of MDR remain elusive. In a previous study, a multidrug resistant osteosarcoma model [MG63/vincristine (VCR)] was established by intermittent exposure of MG63 cells to gradually increasing concentrations of VCR. These cells exhibited cross-resistance to multiple structurally and mechanistically unrelated chemotherapeutic agents. The development of MDR was associated with increased expression of LIM kinase 1 (LIMK1). Compared with that in normal human fetal osteoblasts (hFOB) 1.19, the messenger RNA and protein expression of LIMK1 was significantly elevated both in MG63 and U2OS osteosarcoma cells. To observe the expression pattern of LIMK1 in osteosarcoma, immunohistochemical analyses were performed on specimens derived from 6 patients. The results indicated that LIMK1 was expressed to a greater extent in the tumor parenchyma than in the mesenchyme. The role of LIMK1 in MDR was confirmed by transfecting plasmids coding LIMK1-small interfering RNA (siRNA), wild-type-LIMK1 or empty vector into MG63/VCR cells, and measuring the expression of LIMK1 and multidrug resistance protein 1 (MDR1), also known as P-gycoprotein (P-gp). The results demonstrated that the level of MDR1/P-gp was positively correlated with the level of LIMK1. This correlation was also shown with the doxorubicin efflux assay and by measuring apoptosis. Specifically, after 6 h of incubation with VCR, 25.6% of the cells transfected with the LIMK1-siRNA plasmid were apoptotic compared with 6.2% in the empty vector group and 1.3% in the group of cells transfected with the wild-type-LIMK1 plasmid. Thus, it was concluded that LIMK1 serves a key role in the MDR of osteosarcoma and functions through MDR1.

TNF-related apoptosis-inducing ligand (TRAIL) for bone sarcoma treatment: Pre-clinical and clinical data

Bone sarcomas are rare, highly malignant mesenchymal tumours that affect teenagers and young adults, as well as older patients. Despite intensive, multimodal therapy, patients with bone sarcomas have poor 5-year survival, close to 50%, with lack of improvement over recent decades. TNF-related apoptosis-inducing ligand (TRAIL), a member of the tumour necrosis factor (TNF) ligand superfamily (TNFLSF), has been found to induce apoptosis in cancer cells while sparing nontransformed cells, and may therefore offer a promising new approach to treatment. We cover the existing preclinical and clinical evidence about the use of TRAIL and other death receptor agonists in bone sarcoma treatment. In vitro studies indicate that TRAIL and other death receptor agonists are generally potent against bone sarcoma cell lines. Ewing's sarcoma cell lines present the highest sensitivity, whereas osteosarcoma and chondrosarcoma cell lines are considered less sensitive. In vivo studies also demonstrate satisfactory results, especially in Ewing's sarcoma xenograft models. However, the few clinical trials in the literature show only low or moderate efficacy of TRAIL in treating bone sarcoma. Potential strategies to overcome the in vivo resistance reported include co-administration with other drugs and the potential to deliver TRAIL on the surface of primed mesenchymal or immune cells and the use of targeted single chain antibodies such as scFv-scTRAIL.

Mycoplasma fermentans deacetylase promotes mammalian cell stress tolerance

Mycoplasma fermentans is a pathogenic bacterium that infects humans and has potential pathogenic roles in respiratory, genital and rheumatoid diseases. NAD⁺-dependent deacetylase is involved in a wide range of pathophysiological processes and our studies have demonstrated that expression of mycoplasmal deacetylase in mammalian cells inhibits proliferation but promotes anti-starvation stress tolerance. Furthermore, mycoplasmal deacetylase is involved in cellular anti-oxidation, which correlates with changes in the proapoptotic proteins BIK, p21 and BIM. Mycoplasmal deacetylase binds to and deacetylates the FOXO3 protein, similar with mammalian SIRT2, and affects expression of the FOXO3 target gene BIM, resulting in inhibition of cell proliferation. Mycoplasmal deacetylase also alters the performance of cells under drug stress. This study expands our understanding of the potential molecular and cellular mechanisms of interaction between mycoplasmas and mammalian cells.