Repurposing of Loperamide as a New Drug With Anticancer Activity for Human Osteosarcoma.

BACKGROUND/AIM: Osteosarcoma is an aggressive malignant bone tumor, with unfavorable outcomes in patients with metastatic and recurrent disease. To improve patient survival new treatment options are needed. By using the drug repurposing approach, which takes advantage of already approved drugs with non-oncology primary use, we investigated the activity of loperamide, a peripheral opiate receptor agonist, a drug widely used in clinical practice to treat acute non-specific and chronic diarrhea, on human osteosarcoma. MATERIALS AND METHODS: Human osteosarcoma cell lines (143B, Saos-2, HOS and MG-63) and multidrug-resistant MG-63DXR30 cells were treated with loperamide. Proliferation and cell viability were determined by viable cell count and acid phosphatase assay. Loperamide activity on cell cycle and apoptosis induction were evaluated by flow cytometry and a luminescence assay testing caspase 3/7 activity, respectively. RESULTS: Loperamide significantly inhibited cell proliferation, through alteration of cell cycle profile at G0/G1 phase and apoptotic death in human osteosarcoma cells. Furthermore, loperamide significantly inhibited the growth of multidrug-resistant osteosarcoma cells. CONCLUSION: Our findings provide new perspectives for loperamide and its therapeutic repositioning for the treatment of osteosarcoma.

Association between Bone Turnover Markers and Fracture Healing in Long Bone Non-Union: A Systematic Review.

Background: Fracture healing is a very complex and well-orchestrated regenerative process involving many cell types and molecular pathways. Despite the high efficiency of this process, unsatisfying healing outcomes, such as non-union, occur for approximately 5-10% of long bone fractures. Although there is an obvious need to identify markers to monitor the healing process and to predict a potential failure in callus formation to heal the fracture, circulating bone turnover markers' (BTMs) utility as biomarkers in association with radiographic and clinical examination still lacks evidence so far. Methods: A systematic review on the association between BTMs changes and fracture healing in long bone non-union was performed following PRISMA guidelines. The research papers were identified via the PubMed, Cochrane, Cinahl, Web of Science, Scopus, and Embase databases. Studies in which the failure of fracture healing was associated with osteoporosis or genetic disorders were not included. Results: A total of 172 studies were collected and, given the inclusion criteria, 14 manuscripts were included in this review. Changes in circulating BTMs levels were detected during the healing process and across groups (healed vs. non-union patients and healthy vs. patients with non-union). However, we found high heterogeneity in patients' characteristics (fracture site, gender, and age) and in sample scheduling, which made it impossible to perform a meta-analysis. Conclusions: Clinical findings and radiographic features remain the two important components of non-union diagnosis so far. We suggest improving blood sample standardization and clinical data collection in future research to lay the foundations for the effective use of BTMs as tools for diagnosing non-union.

Extracellular vesicle-associated IGF2BP3 tunes Ewing sarcoma cell migration and affects PI3K/Akt pathway in neighboring cells.

Ewing sarcoma (EWS) is a challenging pediatric cancer characterized by vast intra-tumor heterogeneity. We evaluated the RNA-binding protein IGF2BP3, whose high expression correlates with a poor prognosis and an elevated tendency of metastases, as a possible soluble mediator of inter-cellular communication in EWS. Our data demonstrate that (i) IGF2BP3 is detected in cell supernatants, and it is released inside extracellular vesicles (EVs); (ii) EVs from IGF2BP3-positive or IGF2BP3-negative EWS cells reciprocally affect cell migration but not the proliferation of EWS recipient cells; (iii) EVs derived from IGF2BP3-silenced cells have a distinct miRNA cargo profile and inhibit the PI3K/Akt pathway in recipient cells; (iv) the 11 common differentially expressed miRNAs associated with IGF2BP3-positive and IGF2BP3-negative EVs correctly group IGF2BP3-positive and IGF2BP3-negative clinical tissue specimens. Overall, our data suggest that IGF2BP3 can participate in the modulation of phenotypic heterogeneity.

FT-IR Spectral Signature of Sensitive and Multidrug-Resistant Osteosarcoma Cell-Derived Extracellular Nanovesicles.

Osteosarcoma (OS) is the most common primary bone cancer in children and adolescents. Despite aggressive treatment regimens, the outcome is unsatisfactory, and multidrug resistance (MDR) is a pivotal process in OS treatment failure. OS-derived extracellular vesicles (EVs) promote drug resistance to chemotherapy and target therapy through different mechanisms. The aim of this study was to identify subpopulations of osteosarcoma-EVs by Fourier transform infrared spectroscopy (FT-IR) to define a specific spectral signature for sensitive and multidrug-resistant OS-derived EVs. EVs were isolated from sensitive and MDR OS cells as well as from mesenchymal stem cells by differential centrifugation and ultracentrifugation. EVs size, morphology and protein expression were characterized. FT-IR/ATR of EVs spectra were acquired in the region of 400-4000 cm-1 (resolution 4 cm-1, 128 scans). The FT-IR spectra obtained were consistently different in the EVs compared to cells from which they originate. A specific spectral signature, characterized by a shift and a new band (1601 cm-1), permitted to clearly distinguish EVs isolated by sensitive and multidrug-resistant OS cells. Our data suggest that FT-IR spectroscopy allows to characterize and define a specific spectral signature for sensitive and MDR OS-derived EVs.

Strawberry-Derived Exosome-Like Nanoparticles Prevent Oxidative Stress in Human Mesenchymal Stromal Cells.

Plant-derived exosome-like nanovesicles (EPDENs) have recently been isolated and evaluated as potential bioactive nutraceutical biomolecules. It has been hypothesized that EPDENs may exert their activity on mammalian cells through their specific cargo. In this study, we isolated and purified EPDENs from the strawberry juice of Fragaria x ananassa (cv. Romina), a new cultivar characterized by a high content of anthocyanins, folic acid, flavonols, and vitamin C and an elevated antioxidant capacity. Fragaria-derived EPDENs were purified by a series of centrifugation and filtration steps. EPDENs showed size and morphology similar to mammalian extracellular nanovesicles. The internalization of Fragaria-derived EPDENs by human mesenchymal stromal cells (MSCs) did not negatively affect their viability, and the pretreatment of MSCs with Fragaria-derived EPDENs prevented oxidative stress in a dose-dependent manner. This is possibly due to the presence of vitamin C inside the nanovesicle membrane. The analysis of EPDEN cargo also revealed the presence of small RNAs and miRNAs. These findings suggest that Fragaria-derived EPDENs may be considered nanoshuttles contained in food, with potential health-promoting activity.

The Release of Inflammatory Mediators from Acid-Stimulated Mesenchymal Stromal Cells Favours Tumour Invasiveness and Metastasis in Osteosarcoma.

Osteosarcoma is the most frequent primary malignant bone tumour with an impressive tendency to metastasise. Highly proliferative tumour cells release a remarkable amount of protons into the extracellular space that activates the NF-kB inflammatory pathway in adjacent stromal cells. In this study, we further validated the correlation between tumour glycolysis/acidosis and its role in metastases. In patients, at diagnosis, we found high circulating levels of inflammatory mediators (IL6, IL8 and miR-136-5p-containing extracellular vesicles). IL6 serum levels significantly correlated with disease-free survival and 18F-FDG PET/CT uptake, an indirect measurement of tumour glycolysis and, hence, of acidosis. In vivo subcutaneous and orthotopic models, co-injected with mesenchymal stromal (MSC) and osteosarcoma cells, formed an acidic tumour microenvironment (mean pH 6.86, as assessed by in vivo MRI-CEST pH imaging). In these xenografts, we enlightened the expression of both IL6 and the NF-kB complex subunit in stromal cells infiltrating the tumour acidic area. The co-injection with MSC also significantly increased lung metastases. Finally, by using 3D microfluidic models, we directly showed the promotion of osteosarcoma invasiveness by acidosis via IL6 and MSC. In conclusion, osteosarcoma-associated MSC react to intratumoural acidosis by triggering an inflammatory response that, in turn, promotes tumour invasiveness at the primary site toward metastasis development.

The Emerging Roles of Extracellular Vesicles in Osteosarcoma.

Extracellular vesicles (EVs) are heterogeneous nanosized vesicles that are constitutively released by virtually all types of cells. They have been isolated in almost all body fluids. EVs cargo consists of various molecules (nucleic acids, proteins, lipids, and metabolites), that can be found on EVs surface and/or in their lumen. EVs structure confer stability and allow the transfer of their cargo to specific cell types over a distance. EVs play a critical role in intercellular communication in physiological and pathological settings. The broadening of knowledge on EVs improved our comprehension of cancer biology as far as tumor development, growth, metastasis, chemoresistance, and treatment are concerned. Increasing evidences suggest that EVs have a significant role in osteosarcoma (OS) development, progression, and metastatic process. The modulation of inflammatory communication pathways by EVs plays a critical role in OS and in other bone-related pathological conditions such as osteoarthritis and rheumatoid arthritis. In this review we describe the emerging data on the role of extracellular vesicles in osteosarcoma and discuss the effects and function of OS-derived EVs focusing on their future applicability in clinical practice.

Extracellular Nanovesicles Secreted by Human Osteosarcoma Cells Promote Angiogenesis.

Angiogenesis involves a number of different players among which extracellular nanovesicles (EVs) have recently been proposed as an efficient cargo of pro-angiogenic mediators. Angiogenesis plays a key role in osteosarcoma (OS) development and progression. Acidity is a hallmark of malignancy in a variety of cancers, including sarcomas, as a result of an increased energetic metabolism. The aim of this study was to investigate the role of EVs derived from osteosarcoma cells on angiogenesis and whether extracellular acidity, generated by tumor metabolism, could influence EVs activity. For this purpose, we purified and characterized EVs from OS cells maintained at either acidic or neutral pH. The ability of EVs to induce angiogenesis was assessed in vitro by endothelial cell tube formation and in vivo using chicken chorioallantoic membrane. Our findings demonstrated that EVs derived from osteosarcoma cells maintained either in acidic or neutral conditions induced angiogenesis. The results showed that miRNA and protein content of EVs cargo are correlated with pro-angiogenic activity and this activity is increased by the acidity of tumor microenvironment. This study provides evidence that EVs released by human osteosarcoma cells act as carriers of active angiogenic stimuli that are able to promote endothelial cell functions relevant to angiogenesis.

Exosome-like Nanovesicles Isolated from Citrus limon L. Exert Antioxidative Effect.

BACKGROUND: Exosome-like nanovesicles are biological nanostructures mediating cell-tocell communication and capable to load selected cargos also in the interaction among different species. OBJECTIVE: We aimed to explore the content of exosome-like nanovesicles derived from Citrus limon L. and to analyze the effects of their uptake on human cells. METHOD: We isolated exosome-like nanovesicles from Citrus limon L. juice (EXO-CLs) by differential centrifugation. EXO-CLs were analyzed for short RNA content by advanced sequencing technologies, and for ascorbic acid (vitamin C) and citrate content by enzymatic assays. EXO-CLs anti-oxidant and pro-differentiative potential was evaluated in vitro on mesenchymal stromal cells (MSC), a common tool for regenerative strategies for several human tissues. RESULTS: We showed that EXO-CLs carry detectable amounts of citrate and vitamin C and, although it was not possible to identify specific miRNAs, we detected short RNA sequences (20-30 bp) with unknown functions and with different distribution size in respect to whole Citrus limon L. juice. In vitro, EXO-CLs were uptaken by MSC and had a significant protective effect against oxidative stress. Furthermore, regarding the potential benefit for human bone health, we found that EXO-CLs modulate MSC differentiation versus the osteogenic lineage. CONCLUSION: We demonstrated that incubation with EXO-CLs exert antioxidant activity in human cells. This is most likely due to the direct delivery and uptake of micronutrients by human cells that are well preserved inside the nanovesicle membrane, including the unstable vitamin C. Based on our results, we speculate that fruit-derived nanovesicles have the potential to mediate interspecies influence after food intake.

Does chronic raise of metal ion levels induce oxidative DNA damage and hypoxia-like response in patients with metal-on-metal hip resurfacing?

Metal-on-metal hip resurfacing (MOM-HR) represents a viable alternative to traditional arthroplasty. Nevertheless, in MOM coupling both metal nanoparticles and ions are released, whose toxicity remains a matter of concern. We investigated whether 'endogenous' chronic exposure to cobalt and chromium induced a state of oxidative stress, DNA damage and a hypoxia-like response in patients with well-functioning MOM-HR. Twenty-two patients with unilateral MOM-HR were recruited at long-term. Twenty-one osteoarthritic subjects were enrolled for comparison. Serum ion levels were measured and correlated with 8-hydroxydeoxyguanosine and circulating-free-DNA, as markers of oxidative DNA damage. Moreover, the hypoxia-inducible factor-1α, marker of hypoxic state, was evaluated. Ion concentrations were found to be 5-to-15 times higher in MOM-HR patients than in presurgery subjects (p < 0.001); circulating-free-DNA, 8-hydroxydeoxyguanosine, and hypoxia-inducible factor-1α levels were not significantly different between groups and did not correlate with ion levels. Analyzing the results according to gender, MOM-HR males had higher 8-hydroxydeoxyguanosine levels (p = 0.01) compared with MOM-HR females. Similarly, circulating-free-DNA values were higher in males than females, even if this difference did not reach statistical significance. This research is the first that attempted to investigate the long-term effects of ion dissemination in subjects with well-fixed MOM implants. A significant correlation between biomarkers increase and ion levels was not demonstrated. Nevertheless, both circulating-free-DNA and 8-hydroxydeoxyguanosine showed a tendency to increase in MOM-HR males. Further studies with a larger sample size should be performed to detect the clinical relevance of biomarkers increase especially in younger subjects, where a chronic moderately elevated exposure has to be faced. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 460-466, 2017.

Blocking Tumor-Educated MSC Paracrine Activity Halts Osteosarcoma Progression.

Purpose: Human osteosarcoma is a genetically heterogeneous bone malignancy with poor prognosis despite the employment of aggressive chemotherapy regimens. Because druggable driver mutations have not been established, dissecting the interactions between osteosarcoma cells and supporting stroma may provide insights into novel therapeutic targets.Experimental Design: By using a bioluminescent orthotopic xenograft mouse model of osteosarcoma, we evaluated the effect of tumor extracellular vesicle (EV)-educated mesenchymal stem cells (TEMSC) on osteosarcoma progression. Characterization and functional studies were designed to assess the mechanisms underlying MSC education. Independent series of tissue specimens were analyzed to corroborate the preclinical findings, and the composition of patient serum EVs was analyzed after isolation with size-exclusion chromatography.Results: We show that EVs secreted by highly malignant osteosarcoma cells selectively incorporate a membrane-associated form of TGFß, which induces proinflammatory IL6 production by MSCs. TEMSCs promote tumor growth, accompanied with intratumor STAT3 activation and lung metastasis formation, which was not observed with control MSCs. Importantly, intravenous administration of the anti-IL6 receptor antibody tocilizumab abrogated the tumor-promoting effects of TEMSCs. RNA-seq analysis of human osteosarcoma tissues revealed a distinct TGFß-induced prometastatic gene signature. Tissue microarray immunostaining indicated active STAT3 signaling in human osteosarcoma, consistent with the observations in TEMSC-treated mice. Finally, we isolated pure populations of EVs from serum and demonstrated that circulating levels of EV-associated TGFß are increased in osteosarcoma patients.Conclusions: Collectively, our findings suggest that TEMSCs promote osteosarcoma progression and provide the basis for testing IL6- and TGFß-blocking agents as new therapeutic options for osteosarcoma patients. Clin Cancer Res; 23(14); 3721-33. ©2017 AACR.

Effect of Vinorelbine on cell growth and apoptosis induction in human osteosarcoma in vitro.

Vinorelbine (VNR) is a semi-synthetic vinca alkaloid known to exert its antitumour activity by interfering with the polymerisation of tubulin. It has shown a broad spectrum of activity in some advanced carcinomas of lung, breast and ovary. This report demonstrates for the first time the antiproliferative effect of VNR and its molecular mechanism in human osteosarcoma in vitro. TP53 wild-type HOS cells and TP53 mutated MG-63 cells were chosen for this study. In each cell line, VNR caused a significant dose- and time-dependent growth inhibition and induced apoptotic death independent of TP53 status. Phosphorylation and/or alteration of Bcl-2 were not induced by VNR, thereby indicating a new pathway utilised by the drug to induce apoptosis in this tumour in vitro. VNR produced a down-regulation of cyclin D1 and an up-regulation of p53 expression in TP53 wild-type HOS cells, whereas no alteration in cyclin D1 expression was evident in the TP53 negative MG-63 cells. These data suggest a new potential use for Vinorelbine as a therapeutic agent against human osteosarcoma.

Multimodal transfer of MDR by exosomes in human osteosarcoma.

Exosomes are extracellular vesicles released by both normal and tumour cells which are involved in a new intercellular communication pathway by delivering cargo (e.g., proteins, microRNAs, mRNAs) to recipient cells. Tumour-derived exosomes have been shown to play critical roles in different stages of tumour growth and progression. In this study, we investigated the potential role of exosomes to transfer the multidrug resistance (MDR) phenotype in human osteosarcoma cells. Exosomes were isolated by differential centrifugation of culture media from multidrug resistant human osteosarcoma MG-63DXR30 (Exo/DXR) and MG-63 parental cells (Exo/S). Exosome purity was examined by transmission electron microscopy and confirmed by immunoblot analysis for the expression of specific exosomal markers. Our data showed that exosomes derived from doxorubicin-resistant osteosarcoma cells could be taken up into secondary cells and induce a doxorubicin-resistant phenotype. The incubation of osteosarcoma cells with Exo/DXR decreased the sensitivity of parental cells to doxorubicin, while exposure with Exo/S was ineffective. In addition, we demonstrated that Exo/DXR expressed higher levels of MDR-1 mRNA and P-glycoprotein compared to Exo/S (p=0.03). Interestingly, both MDR-1 mRNA and P-gp increased in MG-63 cells after incubation with Exo/DXR, suggesting this as the main mechanism of exosome-mediated transfer of drug resistance. Our findings suggest that multidrug resistant osteosarcoma cells are able to spread their ability to resist the effects of doxorubicin treatment on sensitive cells by transferring exosomes carrying MDR-1 mRNA and its product P-glycoprotein.

Role of cholesterol ester pathway in the control of cell cycle in human aortic smooth muscle cells.

Cholesterol esterification by acyl-CoA:cholesterol acyltransferase (ACAT) and proliferation of vascular smooth muscle cells (VSMC) are key events in vascular proliferative diseases. Here we performed experiments to ascertain the role of cholesterol ester pathway in the control of human aortic VSMC cycle progression. Results showed that serum-induced VSMC proliferation was preceded by an increased ability of the cells to esterify cholesterol as well as by an increased expression of ACAT and multidrug resistance (MDR1) mRNAs and extracellular related kinases 1/2 (ERK1/2), whereas caveolin-1 levels were markedly decreased. Cell cycle analyses performed in the presence of two inhibitors of cholesterol esterification, directly inhibiting ACAT (Sandoz 58-035) or the transport of cholesterol substrate from plasma membrane to endoplasmic reticulum (progesterone), indicate that each inhibitor suppressed the serum-induced DNA synthesis by accumulation of VSMCs in the G1 phase. The effect was associated with a rapid inhibition of ERK1/2 mitogenic signaling pathway; a down-regulation of cyclin D1, ACAT, and MDR1 mRNA; and an up-regulation of caveolin-1. These data provide a plausible link between cholesterol esterification and control of cell cycle G1/S transition, supporting the hypothesis that cholesterol esterification may accelerate the progression of human vascular proliferative diseases by modulating the rate of the VSMC proliferation.

Mitochondrial DNA D-loop as a new target of Saporin 6 nuclease activity.

The single-chain ribosome-inactivating proteins (RIPs) from plant origin, including Saporin 6 from the seeds of Saponaria officinalis, are ribotoxins known to act as N-glycosidases which depurinate the conserved alpha sarcin loop of large rRNAs. As a consequence, the eukaryotic ribosomes become inactivated, thereby arresting the protein synthesis at the elongation step. RIPs are currently under study as antiviral and antiproliferative agents. Additional in vitro activities of RIPs against either RNA or DNA have been recently described. A specific nuclease activity on plasmidic DNA was demonstrated by either purified or bacterial-recombinant molecules. We report here that human mitochondrial DNA (mtDNA) is a new specific target of Saporin 6 nuclease activity. A unique site of cleavage has been identified and mapped within the most variable part of the D-loop region of the covalently closed circular mtDNA molecule.

Loss of heterozygosity at 17p13.3-ter, distal to TP53, correlates with negative hormonal phenotype in sporadic breast cancer.

Genetic alterations on chromosome 17p are frequent in a variety of human malignancies such as sporadic breast carcinomas. The clinico-pathological significance of it remains to be elucidated. The purpose of this study was to explore whether the allelic loss (LOH) in 17p13.3, which is suggested by the presence of tumour suppressor genes, independent of TP53, are related to current clinico-pathological criteria for characterising breast cancer. A group of sporadic breast carcinomas, with no alteration in TP53 locus, were analysed for the presence of LOH in D17S34 and D17S30/5 loci, mapped to the 17p13.3 region, distinct from and telomeric to TP53. LOH by at least one marker was observed in 13 of 47 informative cases (27.6%). Clinicopathological parameters such as age, menopausal status, histological type, tumour size, nodal status, grading, ploidy, labelling index, S-phase fraction and hormonal phenotype, were evaluated. LOH at distal 17p13.3 significantly correlated with the absence of oestrogen receptors (ER) (P=0.018), progesterone receptors (PgR) (P=0.009) and concordant absence of either ER or PgR (P=0.006). This may provide a basis for speculation as to the function of the putative tumour suppressor genes in 17p13-ter in sporadic breast cancer.

Acridine Orange is an Effective Anti-Cancer Drug that Affects Mitochondrial Function in Osteosarcoma Cells.

Acridine orange (AO) is an antimalarial drug that accumulates into acidic cellular compartments. Lysosomes are quite acidic in cancer cells, and on this basis we have demonstrated that photoactivated AO is selectively toxic in sarcomas. However, photodynamic therapy is only locally effective, and cannot be used to eradicate systemic residual disease. In this study, we have evaluated the activity of non-photoactivated AO on sensitive and chemoresistant osteosarcoma (OS) cells to be considered for the systemic delivery. Since lysosomes are even more acidic in chemoresistant cells (MDR), we found that AO accumulation was significantly higher in the lysosomes of MDR in respect to parental cells, and in both cell types, therapeutic doses of AO significantly inhibited cell growth. However, the level of growth inhibition was inversely related to the level of lysosomal uptake of AO, suggesting that the main target of this agent is indeed extralysosomal. A significant reduction of intracellular ATP content and of the expression of mitochondrial complex III suggests a mitochondrial targeting. Notably, MDR cells showed a lower mitochondrial activity. Finally, the combined treatment of AO with the anticancer agent doxorubicin (DXR) significantly increased chemotoxicity by promoting DXR mitochondrial targeting, as revealed by the further reduction in ATP intracellular content. In conclusion, AO is able to effectively target both sensitive and resistant OS cells through mitotoxicity.

Loss of heterozygosity at pseudoautosomal regions in human breast cancer and association with negative hormonal phenotype.

To determine the possible involvement of X-linked genes in breast cancer, a group of human sporadic breast carcinomas were analyzed for loss of heterozygosity (LOH) at 12 polymorphic loci distributed along the whole chromosome X. LOH by at least one marker was observed in 14 of 46 informative cases and two regions of consistent LOH in 10 of 14 (71.4%) were identified at pseudoautosomal regions (PAR). Allelic losses in these regions significantly correlated with the absence of estrogen receptors (P<0.05) and concordant absence of either estrogen (ER) or progesterone (PgR) receptors (P<0.05). The clinicopathological parameters evaluated, (like age, menopausal status, histological type, tumor size, nodal status, grading, ploidy, labeling index, and S-phase fraction), were independent from the LOH present in the PAR regions of X chromosome. This study suggests a role as a prognostic factor for LOH and ER(-)/PgR(-) when associated and provides some additional support for the existence of candidate tumor suppressor gene on PAR regions, whose alteration may play a role in breast cancer development and progression.

Involvement of HIF-1α activation in the doxorubicin resistance of human osteosarcoma cells.

Osteosarcoma is the most common primary bone cancer in children and adolescents. Despite aggressive treatment regimens, survival outcomes remain unsatisfactory, particularly in patients with metastatic and/or recurrent disease. Unfortunately, treatment failure is commonly due to the development of chemoresistance, for which the underlying molecular mechanisms remain unclear. The aim of the present study was to investigate the role of hypoxia-inducible factor 1α (HIF­1α) and its signalling pathways as mediators of drug-resistance in human osteosarcoma. Toward this aim, we established two osteosarcoma cell lines selected for resistance to doxorubicin, a drug of choice in the treatment of this tumour. Our results showed that the multidrug resistance (MDR) phenotype was also mediated by HIF-1α, the most important regulator of cell adaptation to hypoxia. Our data showed that this transcription factor promoted the outward transport of intracellular doxorubicin by activating the P-glycoprotein (P-gp) expression in osteosarcoma cells maintained in normoxic conditions. In addition, it hindered doxorubicin-induced apoptosis by regulating the expression of c-Myc and p21. Finally, we observed that the doxorubicin-resistant cells maintained for 2 months of continuous culture in a drug-free medium, lost their drug-resistance and this effect was associated with the absence of HIF-1α expression. The emerging role of HIF-1α in osteosarcoma biology indicates its use as a valuable therapeutic target.

Comparative "in vitro" evaluation of the antiresorptive activity residing in four Ayurvedic medicinal plants. Hemidesmus indicus emerges for its potential in the treatment of bone loss diseases.

ETHNOPHARMACOLOGICAL RELEVANCE: Four Indian plants, traditionally used in Ayurvedic medicine: Asparagus racemosus Willd., Emblica officinalis Gaertn., Hemidesmus indicus R. Br., and Rubia cordifolia L. were selected on the basis of their ethnobotanical use and of scientific evidence that suggests a potential efficacy in the treatment of bone-loss diseases. The antiresorptive properties of the four plants have been investigated. The aim was to provide adequate evidence for the exploitation of natural compounds as alternative therapeutics for the treatment of diseases caused by increased osteoclast activity. MATERIALS AND METHODS: Decoctions were prepared from dried plant material according to the traditional procedure and standardization by HPLC was performed using marker compounds for each species. Total polyphenols, flavonoids and radical scavenging activity of the decoctions were also determined. The bioactivity of the plant decoctions was evaluated in subsequent phases. (1) A cytotoxicity screening was performed on the mouse monocytic RAW 264.7 cell line to define the concentrations that could be utilized in the following step. (2) The antiresorptive properties of plant decoctions were compared with that of a "gold standard" drug (alendronate) by measuring osteoclastogenesis inhibition and osteoclast apoptosis. (3) The toxic effect on bone forming cells was excluded by evaluating the impact on the proliferation of osteogenic precursors (mesenchymal stem cells, MSC). RESULTS: All the decoctions inhibited osteoclastogenesis similarly to alendronate at the highest doses, but Hemidesmus indicus and Rubia cordifolia were also effective at lower concentrations. Apoptosis increased significantly when cells were exposed to the highest concentration of Emblica officinalis, Hemidesmus indicus, and Rubia cordifolia. All concentrations of Emblica officinalis tested inhibited the proliferation of osteogenic precursors, while only the highest doses of Asparagus racemosus and Rubia cordifolia were toxic. On the contrary, Hemidesmus indicus did not affect osteogenic precursor growth at any concentration tested. CONCLUSION: Among the medicinal plants included in the study, Hemidesmus indicus showed the greatest antiosteoclastic activity without toxic effect on osteogenic precursors. Therefore, Hemidesmus indicus exhibits the properties of an antiresorptive drug and represents the ideal candidate for further clinical investigations.