Inorganic phosphate enhances sensitivity of human osteosarcoma U2OS cells to doxorubicin via a p53-dependent pathway

The Biological Impact of Some Phosphonic and Phosphinic Acid Derivatives on Human Osteosarcoma

Osteosarcoma malignancy currently represents a major health problem; therefore, the need for new therapy approaches is of great interest. In this regard, the current study aims to evaluate the anti-neoplastic potential of a newly developed phosphinic acid derivative (2-carboxyethylphenylphosphinic acid) and, subsequently, to outline its pharmaco-toxicological profile by employing two different in vitro human cell cultures (keratinocytes-HaCaT-and osteosarcoma SAOS-2 cells), employing different techniques (MTT assay, cell morphology assessment, LDH assay, Hoechst staining and RT-PCR). Additionally, the results obtained are compared with three commercially available phosphorus-containing compounds (P1, P2, P3). The results recorded for the newly developed compound (P4) revealed good biocompatibility (cell viability of 77%) when concentrations up to 5 mM were used on HaCaT cells for 24 h. Also, the HaCaT cultures showed no significant morphological alterations or gene modulation, thus achieving a biosafety profile even superior to some of the commercial products tested herein. Moreover, in terms of anti-osteosarcoma activity, 2-carboxyethylphenylphosphinic acid expressed promising activity on SAOS-2 monolayers, the cells showing viability of only 55%, as well as apoptosis features and important gene expression modulation, especially Bid downregulation. Therefore, the newly developed compound should be considered a promising candidate for further in vitro and in vivo research related to osteosarcoma therapy.

Ephedra herb reduces adriamycin-induced testicular toxicity by upregulating the gonadotropin-releasing hormone signalling pathway

OBJECTIVE

We investigated the protective effects of ephedra herb (HEPH) on adriamycin-induced testicular toxicity in rats and explored the potential mechanisms underlying these effects.

METHODS

A rat model of adriamycin injury was established, and sperm motility-related indicator and oxidative stress levels in the testis were evaluated. Serum levels of sex hormones and levels of testicular cell apoptosis were detected by enzyme-linked immunosorbent assay and flow cytometry, respectively. Western blotting (WB), immunofluorescence analyses, and reverse transcription-polymerase chain reaction (RT-PCR) were performed to evaluate the gonadotropin-releasing hormone (GnRH) signalling pathway- and meiosis-related genes and proteins. In subsequent in vitro experiments, adriamycin was used to stimulate GC-1 cells, which were treated with HEPH, ephedrine, or pseudoephedrine. Cell viability was assessed using flow cytometry to detect apoptosis and reactive oxygen species, whereas the GnRH signalling pathway and levels of meiosis-related genes and proteins were evaluated by InCell WB, a high-content imaging system, and RT-PCR.

RESULTS

Per in vivo experiments, HEPH restored testicular weight and function, sperm characteristics, serum and tissue hormonal levels, and antioxidant defences and significantly activated the GnRH signalling pathway- and meiosis-related protein levels. All protective effects of HEPH against adriamycin-induced injury were antagonised by the GnRH antagonist cetrorelix. In vitro, HEPH, ephedrine, and pseudoephedrine significantly reduced adriamycin-induced GC-1 cell apoptosis and reactive oxygen species levels and increased the expression of GnRH signalling pathway- and meiosis-related proteins. The effect of pseudoephedrine was greater than that of ephedrine, and these findings may be an important basis for understanding the effects of HEPH.

Hydrogen phosphate selectively induces MDA MB 231 triple negative breast cancer cell death in vitro

Phosphate ions are the most abundant anions inside the cells, and they are increasingly gaining attention as key modulators of cellular function and gene expression. However, little is known about the effect of inorganic phosphate ions on cancer cells, particularly breast cancer cells. Here, we investigated the toxicity of different phosphate compounds to triple-negative human breast cancer cells, particularly, MDA-MB-231, and compared it to that of human monocytes, THP-1. We found that, unlike dihydrogen phosphate (H₂PO₄⁻), hydrogen phosphate (HPO₄²⁻) at 20 mM or lower concentrations induced breast cancer cell death more than immune cell death, mainly via apoptosis. We correlate this effect to the fact that phosphate in the form of HPO₄²⁻ raises pH levels to alkaline levels which are not optimum for transport of phosphate into cancer cells. The results in this study highlight the importance of further exploring hydrogen phosphate (HPO₄²⁻) as a potential therapeutic for the treatment of breast cancer.

Modulating phosphate consumption, a novel therapeutic approach for the control of cancer cell proliferation and tumorigenesis

Phosphorus, often in the form of inorganic phosphate (Pi), is critical to cellular function on many levels; it is required as an integral component of kinase signaling, in the formation and function of DNA and lipids, and energy metabolism in the form of ATP. Accordingly, crucial aspects of cell mitosis - such as DNA synthesis and ATP energy generation - elevate the cellular requirement for Pi, with rapidly dividing cells consuming increased levels. Mechanisms to sense, respond, acquire, accumulate, and potentially seek Pi have evolved to support highly proliferative cellular states such as injury and malignant transformation. As such, manipulating Pi availability to target rapidly dividing cells presents a novel strategy to reduce or prevent unrestrained cell growth. Currently, limited knowledge exists regarding how modulating Pi consumption by pre-cancerous cells might influence the initiation of aberrant growth during malignant transformation, and if reducing the bioavailability or suppressing Pi consumption by malignant cells could alter tumorigenesis. The concept of targeting Pi-regulated pathways and/or consumption by pre-cancerous or tumor cells represents a novel approach to cancer prevention and control, although current data remains insufficient as to rigorously assess the therapeutic value and physiological relevance of this strategy. With this review, we present a critical evaluation of the paradox of how an element critical to essential cellular functions can, when available in excess, influence and promote a cancer phenotype. Further, we conjecture how Pi manipulation could be utilized as a therapeutic intervention, either systemically or at the cell level, to ultimately suppress or treat cancer initiation and/or progression.

Identification of a survival-related signature for sarcoma patients through integrated transcriptomic and proteomic profiling analyses

Sarcoma (SARC) represents a group of highly histological and molecular heterogeneous rare malignant tumors with poor prognosis. There are few proposed classifiers for predicting patient's outcome. The Cancer Proteome Atlas (TPCA) and The Cancer Genome Atlas (TCGA) databases provide multi-omics datasets that enable a comprehensive investigation for this disease. The proteomic expression profile of SARC patients along with the clinical information was downloaded. 55 proteins were found to be associated with overall survival (OS) of patients using univariate Cox regression analysis. We developed a prognostic risk signature that comprises seven proteins (AMPKALPHA, CHK1, S6, ARID1A, RBM15, ACETYLATUBULINLYS40, and MSH6) with robust predictive performance using multivariate Cox stepwise regression analysis. Additionally, the signature could be an independent prognostic predictor after adjusting for clinicopathological parameters. Patients in high-risk group also have worse progression free intervals (PFI) than that of patients in low-risk group, but not for disease free intervals (DFI). The signature was validated using transcriptomic profile of SARC patients from TCGA. Potential mechanisms between high- and low-risk groups were identified using differentially expressed genes (DEGs) analysis. These DEGs were primarily enriched in RAS and MPAK signaling pathways. The signature protein molecules are candidate biomarkers for SARC, and the analysis of computational biology in tumor infiltrating lymphocytes and immune checkpoint molecules revealed distinctly immune landscapes of high- and low-risk patients. Together, we constructed a prognostic signature for predicting outcomes for SARC integrating proteomic and transcriptomic profiles, this might have value in guiding clinical practice.

Untargeted LC-MS/MS analysis reveals metabolomics feature of osteosarcoma stem cell response to methotrexate

Background

Cancer stem cell (CSC) is identified in osteosarcoma (OS) and considered resistant to chemotherapeutic agents. However, the mechanism of osteosarcoma stem cell (OSC) resistant to chemotherapy remains debatable and vague, and the metabolomics feature of OSC is not clarified.

Materials and methods

OSC was isolated by using sphere forming assay and identified. Untargeted LC-MS/MS analysis was performed to reveal the metabolomics feature of OSC and underlying mechanisms of OSC resistant to methotrexate (MTX).

Results

OSC was efficiently isolated and identified from human OS 143B and MG63 cell lines with enhanced chemo-resistance to MTX. The untargeted LC-MS analysis revealed that OSC showed differential metabolites and perturbed signaling pathways, mainly involved in metabolisms of fatty acid, amino acid, carbohydrate metabolism and nucleic acid. After treated with MTX, metabolomics feature of OSC was mainly involved metabolisms of amino acid, fatty acid, energy and nucleic acid. Moreover, compared with their parental OS cells response to MTX, the differential metabolites and perturbed signaling pathways were mainly involved in metabolism of amino acid, fatty acid and nucleic acid. What's more, Rap1 signaling pathway and Ras signaling pathway were involved in OS cells and their SCs response to MTX.

Conclusion

Sphere-forming assay was able to efficiently isolate OSC from human OS cell lines and the untargeted LC-MS/MS analysis was suggested a sufficient methodology to investigate metabolomics features of OS cells and OSCs. Moreover, the metabolomics features of OSCs response to MTX might reveal a further understanding of chemotherapeutic resistance in OS.

SLC34A2 simultaneously promotes papillary thyroid carcinoma growth and invasion through distinct mechanisms

Thyroid cancer is the fastest growing cancer among all solid tumors in recent decades. Papillary thyroid carcinoma (PTC) is the most predominant type of thyroid cancer. Around 30% of PTC patients with distant metastases and local invasion receive poor prognosis. Thus, the identification of new druggable biological targets is of great importance. Accumulating evidence indicates that solute carrier family numbers have emerged as obligate effectors during the progression of multiple malignancies. Here, we uncovered the functional significance, molecular mechanisms, and clinical impact of solute carrier family 34 member A2 (SLC34A2) in PTC. SLC34A2 was markedly overexpressed in PTC tissues at both mRNA and protein levels compared with matched adjacent normal tissues due to promoter hypomethylation mediated by the DNA methyltransferase 3 beta (DNMT3B). Furthermore, a series of in vivo and in vitro gain- or loss-of-functional assays elucidated the role of SLC34A2 in boosting cell proliferation, cell cycle progression, migration, invasion, and adhesion of PTC cells. Using immunoprecipitation and mass spectrometry, we discovered that SLC34A2 bound to the actin-binding repeats domain of Cortactin (CTTN), thereby inducing the invadopodia formation of PTC cells to promote the metastasis potential of PTC cells. Besides, our mechanistic studies, as well as gene set enrichment analysis (GSEA), have pinpointed the PTEN/AKT/FOXO3a pathway as a major signaling functioning downstream of SLC34A2 regulated cell growth. Taken together, our results highlighted that SLC34A2 plays a pivotal oncogenic role during carcinogenesis and metastasis through distinct mechanisms in PTC.

Emerging Anticancer Potentials of Selenium on Osteosarcoma

Selenium is a trace element essential to humans and forms complexes with proteins, which exert physiological functions in the body. In vitro studies suggested that selenium possesses anticancer effects and may be effective against osteosarcoma. This review aims to summarise current evidence on the anticancer activity of inorganic and organic selenium on osteosarcoma. Cellular studies revealed that inorganic and organic selenium shows cytotoxicity, anti-proliferative and pro-apoptotic effects on various osteosarcoma cell lines. These actions may be mediated by oxidative stress induced by selenium compounds, leading to the activation of p53, proapoptotic proteins and caspases. Inorganic selenium is selective towards cancer cells, but can cause non-selective cell death at a high dose. This condition challenges the controlled release of selenium from biomaterials. Selenium treatment in animals inoculated with osteosarcoma reduced the tumour size, but did not eliminate the incidence of osteosarcoma. Only one study investigated the relationship between selenium and osteosarcoma in humans, but the results were inconclusive. In summary, although selenium may exert anticancer properties on osteosarcoma in experimental model systems, its effects in humans require further investigation.

Xenotropic and polytropic retrovirus receptor 1 (XPR1) promotes progression of tongue squamous cell carcinoma (TSCC) via activation of NF-κB signaling

Background

Xenotropic and polytropic retrovirus receptor 1 (XPR1), a previously identified cellular receptor for several murine leukemia viruses, plays a role in many pathophysiological processes. However, the role of XPR1 in human cancers has not yet been characterized.

Methods

Real-time PCR and western blotting assay were used to measure the expression of XPR1 in tongue squamous cell carcinoma (TSCC) tissues. Expression of XPR1 and p65 in clinical specimens was analyzed using immunohistochemical assay. The function of XPR1 on progression of TSCC was explored using in vitro and in vivo experiments. The molecular mechanism by which XPR1 helps to cancer progression was investigated by luciferase reporter activity, ELISA, PKA activity assay, immunofluorescence, western blotting and qPCR assay.

Results

Herein, we find that XPR1 is markedly upregulated in TSCC tissues compared to normal tongue tissues. High expression of XPR1 significantly correlates with the malignant features and poor patient survival in TSCC. Ectopic expression of XPR1 increases, while silencing of XPR1 reduces the proliferation, invasion and anti-apoptosis capacities of TSCC cells. Importantly, silencing of XPR1 effectively inhibits the tumorigenecity of TSCC cells. Moreover, we identified that XPR1 increased the concentration of intracellular cAMP and activated PKA. Thus, XPR1 promoted phosphorylation and activation of NF-κB signaling, which is required for XPR1-mediated oncogenic roles and significantly correlates with XPR1 expression in clinical specimens.

Conclusions

These findings uncover a critical role of XPR1 in TSCC progression via activation of NF-κB, and suggest that XPR1 might be a potential prognostic marker or therapeutic target.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1155-6) contains supplementary material, which is available to authorized users.

Silica/Polyethylene Glycol Hybrid Materials Prepared by a Sol-Gel Method and Containing Chlorogenic Acid

Chlorogenic acid (CGA) is a very common dietary polyphenolic compound. CGA is becoming very attractive due to its potential use as preventive and therapeutic agent in many diseases, including cancer. Inorganic/organic hybrid materials are gaining considerable attention in the biomedical field. The sol-gel process provides a useful way to obtain functional organic/inorganic hybrids. The aim of this study was to synthesize silica/polyethylene glycol (PEG) hybrids with different percentages of CGA by sol-gel technique and to investigate their impact on the cancer cell proliferation. Synthesized materials have been chemically characterized through the FTIR spectroscopy and their bioactivity evaluated looking by SEM at their ability to produce a hydroxyapatite layer on their surface upon incubation with simulated body fluid (SBF). Finally, their effects on cell proliferation were studied in cell lines by direct cell number counting, MTT, flow cytometry-based cell-cycle and cell death assays, and immunoblotting experiments. Notably, we found that SiO₂/PEG/CGA hybrids exhibit clear antiproliferative effects in different tumor, including breast cancer and osteosarcoma, cell lines in a CGA dependent manner, but not in normal cells. Overall, our results increase the evidence of CGA as a possible anticancer agent and illustrate the potential for clinical applications of sol-gel synthesized SiO₂/PEG/CGA materials.

Astragaloside IV enhances taxol chemosensitivity of breast cancer via caveolin-1-targeting oxidant damage

Accumulating evidence suggests that caveolin-1 (CAV-1) is a stress-related oncotarget and closely correlated to chemoresistance. Targeting CAV-1 might be a promising strategy to improve chemosensitivity for breast cancer treatment. Astragaloside IV (AS-IV), a bioactive compound purified from Astragalus membranaceus, has been shown to exhibit multiple bioactivities, including anticancer. However, the involved molecular targets are still ambiguous. In this study, we investigated the critical role of CAV-1 in mediating the chemosensitizing effects of AS-IV to Taxol on breast cancer. We found that AS-IV could enhance the chemosensitivity of Taxol with minimal direct cytotoxicity on breast cancer cell lines MCF-7 and MDA-MB-231, as well as the nontumor mammary epithelial cell line MCF-10A. AS-IV was further demonstrated to aggravate Taxol-induced apoptosis and G2/M checkpoint arrest. The phosphorylation of mitogen-activated protein kinase (MAPK) signaling extracellular signal-regulated kinase (ERK) and c-Jun N-terminal Kinase (JNK), except p38, was also abrogated by a synergistic interaction between AS-IV and Taxol. Moreover, AS-IV inhibited CAV-1 expression in a dose-dependent manner and reversed CAV-1 upregulation induced by Taxol administration. Mechanism study further demonstrated that AS-IV treatment triggered the eNOS/NO/ONOO^- pathway via inhibiting CAV-1, which led to intense oxidant damage. CAV-1 overexpression abolished the chemosensitizing effects of AS-IV to Taxol by inhibiting oxidative stress. In vivo experiments further validated that AS-IV increased Taxol chemosensitivity on breast cancer via inhibiting CAV-1 expression, followed by activation of the eNOS/NO/ONOO^- pathway. Taken together, our findings not only suggested the potential of AS-IV as a promising candidate to enhance chemosensitivity, but also highlighted the significance of CAV-1 as the target to reverse cancer drug resistance.

Green and cost-effective synthesis of carbon dots from date kernel and their application as a novel switchable fluorescence probe for sensitive assay of Zoledronic acid drug in human serum and cellular imaging

A new label-free, sensitive and selective off and on signaling fluorescence platform for assay of trace levels of Zoledronic acid (ZA) drug in human biological samples based on nitrogen doped carbon dots (N-CDs) - ferric ions (Fe³⁺) was designed. The fluorescence probe, N-CDs, was synthesized for the first time through a facile, eco-friendly and one-step hydrothermal treatment using date kernel as the precursor without any need to use chemical reagents. These CDs exhibited excellent water solubility, ionic and photo stability in various circumstances and a highly relative quantum yield of 12.5%. In the presence of Fe³⁺, the fluorescence intensity (FL) for N-CDs was strongly quenched due to the interaction between ferric ions and the functional groups at the N-CDs (switch off). Afterwards, by the addition of ZA, the fluorescence sensor status turned to "ON" (switch on) due to the dominance of ZA in the competition between functional groups on the surface of N-CDs and phosphate groups in ZA in the interaction with Fe³⁺ results in removing Fe³⁺ from the surface of N-CDs. Under the optimized conditions, the proposed fluorescence probe (N-CDs-Fe³⁺) exhibited good sensing performance for ZA assay with a linearity from 0.1 μM to 10.0 μM, a detection limit of 0.04 μM and the precision of 2.70%. The developed N-CDs-Fe³⁺ sensor was successfully used for the assay of ZA contents with good recoveries and selectivity in human serum samples. Meanwhile, the in vitro cytotoxic activity and cellular uptake of N-CDs were investigated on human osteosarcoma (MG-63) cell line.

Characterization and assessment of potential microRNAs involved in phosphate-induced aortic calcification

Medial artery calcification, a hallmark of type 2 diabetes mellitus and chronic kidney disease (CKD), is known as an independent risk factor for cardiovascular mortality and morbidity. Hyperphosphatemia associated with CKD is a strong stimulator of vascular calcification but the molecular mechanisms regulating this process remain not fully understood. We showed that calcification was induced after exposing Sprague-Dawley rat aortic explants to high inorganic phosphate level (P_i , 6 mM) as examined by Alizarin red and Von Kossa staining. This calcification was associated with high Tissue-Nonspecific Alkaline Phosphatase (TNAP) activity, vascular smooth muscle cells de-differentiation, manifested by downregulation of smooth muscle 22 alpha (SM22α) protein expression which was assessed by immunoblot analysis, immunofluorescence, and trans-differentiation into osteo-chondrocyte-like cells revealed by upregulation of Runt related transcription factor 2 (Runx2), TNAP, osteocalcin, and osteopontin mRNA levels which were determined by quantitative real-time PCR. To unravel the possible mechanism(s) involved in this process, microRNA (miR) expression profile, which was assessed using TLDA technique and thereafter confirmed by individual qRT-PCR, revealed differential expression 10 miRs, five at day 3 and 5 at day 6 post P_i treatment versus control untreated aortas. At day 3, miR-200c, -155, 322 were upregulated and miR-708 and 331 were downregulated. After 6 days of treatment, miR-328, -546, -301a were upregulated while miR-409 and miR-542 were downregulated. Our results indicate that high P_i levels trigger aortic calcification and modulation of certain miRs. These observations suggest that mechanisms regulating aortic calcification might involve miRs, which warrant further investigations in future studies.

Oxidative Stress and Cellular Response to Doxorubicin: A Common Factor in the Complex Milieu of Anthracycline Cardiotoxicity

The production of reactive species is a core of the redox cycling profile of anthracyclines. However, these molecular characteristics can be viewed as a double-edged sword acting not only on neoplastic cells but also on multiple cellular targets throughout the body. This phenomenon translates into anthracycline cardiotoxicity that is a serious problem in the growing population of paediatric and adult cancer survivors. Therefore, better understanding of cellular processes that operate within but also go beyond cardiomyocytes is a necessary step to develop more effective tools for the prevention and treatment of progressive and often severe cardiomyopathy experienced by otherwise successfully treated oncologic patients. In this review, we focus on oxidative stress-triggered cellular events such as DNA damage, senescence, and cell death implicated in anthracycline cardiovascular toxicity. The involvement of progenitor cells of cardiac and extracardiac origin as well as different cardiac cell types is discussed, pointing to molecular signals that impact on cell longevity and functional competence.

The Influence of the Polymer Amount on the Biological Properties of PCL/ZrO₂ Hybrid Materials Synthesized via Sol-Gel Technique

Organic/inorganic hybrid materials are attracting considerable attention in the biomedical area. The sol-gel process provides a convenient way to produce many bioactive organic-inorganic hybrids. Among those, poly(e-caprolactone)/zirconia (PCL/ZrO₂) hybrids have proved to be bioactive with no toxic materials. The aim of this study was to investigate the effects of these materials on the cellular response as a function of the PCL content, in order to evaluate their potential use in the biomedical field. For this purpose, PCL/ZrO₂ hybrids containing 6, 12, 24, and 50 wt % of PCL were synthesized by the sol-gel method. The effects of their presence on the NIH-3T3 fibroblast cell line carrying out direct cell number counting, MTT, cell damage assays, flow cytometry-based analysis of cell-cycle progression, and immunoblotting experiments. The results confirm and extend the findings that PCL/ZrO₂ hybrids are free from toxicity. The hybrids containing 12 and 24 wt % PCL, (more than 6 and 50 wt % ones) enhance cell proliferation when compared to pure ZrO₂ by affecting cell cycle progression. The finding that the content of PCL in PCL/ZrO₂ hybrids differently supports cell proliferation suggests that PCL/ZrO₂ hybrids could be useful tools with different potential clinical applications.

Targeted drug delivery of near IR fluorescent doxorubicin-conjugated poly(ethylene glycol) bisphosphonate nanoparticles for diagnosis and therapy of primary and metastatic bone cancer in a mouse model

BACKGROUND

Most primary and metastatic bone tumors demonstrate increased osteoclast activity and bone resorption. Current treatment is based on a combination of surgery, radiotherapy and chemotherapy. Severe side effects are associated with chemotherapy due to use of high dosage and nonspecific uptake. Bisphosphonates have a strong affinity to Ca2+ ions and are widely used in the treatment of bone disorders.

RESULTS

We have engineered a unique biodegradable bisphosphonate nanoparticle (NPs) bearing two functional surface groups: (1) primary amine groups for covalent attachment of a dye/drug (e.g. NIR dye Cy 7 or doxorubicin); (2) bisphosphonate groups for targeting and chelation to bone hydroxyapatite. In addition, these engineered NPs contain high polyethyleneglycol (PEG) concentration in order to increase their blood half life time. In vitro experiments on Saos-2 human osteosarcoma cell line, demonstrated that at a tenth of the concentration, doxorubicin-conjugated bisphosphonate NPs achieved a similar uptake to free doxorubicin. In vivo targeting experiments using the NIR fluorescence bisphosphonate NPs on both Soas-2 human osteosarcoma xenograft mouse model and orthotopic bone metastases mCherry-labeled 4T1 breast cancer mouse model confirmed specific targeting. In addition, therapeutic in vivo experiments using doxorubicin-conjugated bisphosphonate NPs demonstrated a 40% greater inhibition of tumor growth in Saos-2 human osteosarcoma xenograft mouse model when compared to free doxorubicin.

CONCLUSIONS

In this research we have shown the potential use of doxorubicin-conjugated BP NPs for the targeting and treatment of primary and metastatic bone tumors. The targeted delivery of doxorubicin to the tumor significantly increased the efficacy of the anti-cancer drug, thus enabling the effective use of a lower concentration of doxorubicin. Furthermore, the targeting ability of the BP NPs in an orthotopic xenograft mouse model reinforced our findings that these BP NPs have the potential to be used for the treatment of primary and metastatic bone cancer.

CTGF enhances resistance to 5-FU-mediating cell apoptosis through FAK/MEK/ERK signal pathway in colorectal cancer

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers among both males and females; the chemotherapy drug 5-fluorouracil (5-FU) is one of a doctors’ first lines of defense against CRC. However, therapeutic failures are common because of the emergence of drug resistance. Connective tissue growth factor (CTGF) is a secreted protein that binds to integrins, and regulates the invasiveness and metastasis of certain carcinoma cells. Here, we found that CTGF was upregulated in drug-resistant phenotype of human CRC cells. Overexpression of CTGF enhanced the resistance to 5-FU-induced cell apoptosis. Moreover, downregulating the expression of CTGF promoted the curative effect of chemotherapy and blocked the cell cycle in the G1 phase. We also found that CTGF facilitated resistance to 5-FU-induced apoptosis by increasing the expression of B-cell lymphoma-extra large (Bcl-xL) and survivin. Then we pharmacologically blocked MEK/ERK signal pathway and assessed 5-FU response by MTT assays. Our current results indicate that the expression of phosphorylated forms of MEK/ERK increased in high CTGF expression cells and MEK inhibited increases in 5-FU-mediated apoptosis of resistant CRC cells. Therefore, our data suggest that MEK/ERK signaling contributes to 5-FU resistance through upstream of CTGF, and supports CRC cell growth. Comprehending the molecular mechanism underlying 5-FU resistance may ultimately aid the fight against CRC.

S-Adenosylmethionine Affects ERK1/2 and Stat3 Pathways and Induces Apotosis in Osteosarcoma Cells

Osteosarcoma is a very aggressive bone tumor. Its clinical outcome remains discouraging despite intensive surgery, radiotherapy, and chemotherapy. Thus, novel therapeutic approaches are demanded. S-Adenosylmethionine (AdoMet) is a naturally occurring molecule that is synthesized in our body by methionine adenosyltransferase isoenzymes and is also available as a nutritional supplement. AdoMet is the principal methyl donor in numerous methylation reactions and is involved in many biological functions. Interestingly, AdoMet has been shown to exert antiproliferative action in various cancer cells. However, the underlying molecular mechanisms are just starting to be studied. Here, we investigated the effects of AdoMet on the proliferation of osteosarcoma U2OS cells and the underlying mechanisms. We carried out direct cell number counting, MTT and flow cytometry-based assays, and immunoblotting experiments in response to AdoMet treatment. We found that AdoMet strongly inhibits proliferation of U2OS cells by slowing-down cell cycle progression and by inducing apoptosis. We also report that AdoMet consistently causes an increase of p53 and p21 cell-cycle inhibitor, a decrease of cyclin A and cyclin E protein levels, and a marked increase of pro-apoptotic Bax/Bcl-2 ratio, with caspase-3 activation and PARP cleavage. Moreover, the AdoMet-induced antiproliferative effects were dynamically accompanied by profound changes in ERK1/2 and STAT3 protein and phosphorylation levels. Altogether, our data enforce the evidence of AdoMet acting as a biomolecule with antiproliferative action in osteosarcoma cells, capable of down-regulating ERK1/2 and STAT3 pathways leading to cell cycle inhibition and apoptosis, and provide a rationale for the possible use of AdoMet in osteosarcoma therapy.

Inorganic phosphate in the development and treatment of cancer: A Janus Bifrons?

Inorganic phosphate (Pi) is an essential nutrient to living organisms. It is required as a component of the energy metabolism, kinase/phosphatase signaling and in the formation and function of lipids, carbohydrates and nucleic acids and, at systemic level, it plays a key role for normal skeletal and dentin mineralization. Pi represents an abundant dietary element and its intestinal absorption is efficient, minimally regulated and typically extends to approximately 70%. Maintenance of proper Pi homeostasis is a critical event and serum Pi level is maintained within a narrow range through an elaborate network of humoral interactions and feedback loops involving intestine, kidney, parathyroid gland and bone, and depends on the activity of a number of hormones, including parathyroid hormone, 1,25-dihydroxy vitamin D, and fibroblast growth factor 23 as major regulators of Pi homeostasis. Notably, Pi intake seemingly continues to increase as a consequence of chronic high-phosphorus (P) diets deriving from the growing consumption of highly processed foods, especially restaurant meals, fast foods, and convenience foods. Several recent reports have generated significant associations between high-P intake or high-serum Pi concentration and morbidity and mortality. Many chronic diseases, including cardiovascular diseases, obesity and even cancer have been proposed to be associated with high-P intakes and high-serum Pi concentrations. On the other hand, there is also evidence that Pi can have antiproliferative effects on some cancer cell types, depending on cell status and genetic background and achieve additive cytotoxic effects when combined with doxorubicin, illustrating its potential for clinical applications and suggesting that up-regulating Pi levels at local sites for brief times, might contribute to the development of novel and cheap modalities for therapeutic intervention in some tumours. Overall, the influence of Pi on cell function and the possible relationship to cancer have to be fully understood and investigated further.

Targeting protein kinases to reverse multidrug resistance in sarcoma

Sarcomas are a group of cancers that arise from transformed cells of mesenchymal origin. They can be classified into over 50 subtypes, accounting for approximately 1% of adult and 15% of pediatric cancers. Wide surgical resection, radiotherapy, and chemotherapy are the most common treatments for the majority of sarcomas. Among these therapies, chemotherapy can palliate symptoms and prolong life for some sarcoma patients. However, sarcoma cells can have intrinsic or acquired resistance after treatment with chemotherapeutics drugs, leading to the development of multidrug resistance (MDR). MDR attenuates the efficacy of anticancer drugs and results in treatment failure for sarcomas. Therefore, overcoming MDR is an unmet need for sarcoma therapy. Certain protein kinases demonstrate aberrant expression and/or activity in sarcoma cells, which have been found to be involved in the regulation of sarcoma cell progression, such as cell cycle, apoptosis, and survival. Inhibiting these protein kinases may not only decrease the proliferation and growth of sarcoma cells, but also reverse their resistance to chemotherapeutic drugs to subsequently reduce the doses of anticancer drugs and decrease drug side-effects. The discovery of novel strategies targeting protein kinases opens a door to a new area of sarcoma research and provides insight into the mechanisms of MDR in chemotherapy. This review will focus on the recent studies in targeting protein kinase to reverse chemotherapeutic drug resistance in sarcoma.

Inorganic Phosphate Prevents Erk1/2 and Stat3 Activation and Improves Sensitivity to Doxorubicin of MDA-MB-231 Breast Cancer Cells

Due to its expression profile, triple-negative breast cancer (TNBC) is refractory to the most effective targeted therapies available for breast cancer treatment. Thus, cytotoxic chemotherapy represents the mainstay of treatment for early and metastatic TNBC. Therefore, it would be greatly beneficial to develop therapeutic approaches that cause TNBC cells to increase their sensitivity to cytotoxic drugs. Inorganic phosphate (Pi) is emerging as an important signaling molecule in many cell types. Interestingly, it has been shown that Pi greatly enhances the sensitivity of human osteosarcoma cell line (U2OS) to doxorubicin. We investigated the effects of Pi on the sensitivity of TNBC cells to doxorubicin and the underlying molecular mechanisms, carrying out flow cytometry-based assays of cell-cycle progression and cell death, MTT assays, direct cell number counting and immunoblotting experiments. We report that Pi inhibits the proliferation of triple-negative MDA-MB-231 breast cancer cells mainly by slowing down cell cycle progression. Interestingly, we found that Pi strongly increases doxorubicin-induced cytotoxicity in MDA-MB-231 cells by apoptosis induction, as revealed by a marked increase of sub-G1 population, Bcl-2 downregulation, caspase-3 activation and PARP cleavage. Remarkably, Pi/doxorubicin combination-induced cytotoxicity was dynamically accompanied by profound changes in Erk1/2 and Stat3 protein and phosphorylation levels. Altogether, our data enforce the evidence of Pi acting as a signaling molecule in MDA-MB-231 cells, capable of inhibiting Erk and Stat3 pathways and inducing sensitization to doxorubicin of TNBC cells, and suggest that targeting Pi levels at local sites might represent the rationale for developing effective and inexpensive strategies for improving triple-negative breast cancer therapy.

Downregulation of phosphoglycerate dehydrogenase inhibits proliferation and enhances cisplatin sensitivity in cervical adenocarcinoma cells by regulating Bcl-2 and caspase-3

Phosphoglycerate dehydrogenase (PHGDH) is the key enzyme of de novo serine biosynthesis. Previous reports have demonstrated that PHGDH plays an important role in some malignancies. However, the biological role of PHGDH in human cervical adenocarcinoma has not been explored. We examined the expression of PHGDH in 54 cervical adenocarcinoma samples by immunohistochemistry and evaluated the association with clinicopathological parameters and prognosis. We performed shRNA transfection to knock down PHGDH gene expression in HeLa cells. A cell proliferation test, cisplatin cytotoxicity test and apoptosis test examined the HeLa cell line after PHGDH knockdown in vitro. In vivo tumorigenesis was assessed using a mouse xenograft model. Moreover, we examined the effects on Bcl-2 and cleaved caspase-3 expression after knockdown of PHGDH and treatment of cisplatin for 48h by Western blot. In this study, we demonstrated that elevated PHGDH expression was found in cervical adenocarcinoma and was associated with tumor size and prognosis. Knocking down PHGDH in HeLa cells significantly inhibited cell proliferation and increased cisplatin chemotherapy sensitivity. Silencing PHGDH resulted in inhibition of tumorigenesis in vivo. Furthermore, PHGDH knockdown reduced Bcl-2 and increased cleaved caspase-3 expression. Collectively, our study indicates the novel roles of PHGDH in cervical adenocarcinoma and identifies PHGDH as a new anticancer target.

Autophagy prevents doxorubicin‑induced apoptosis in osteosarcoma

Autophagy is a process of selective degradation of cellular components. Autophagy is an adaptive process in the majority of tumor cells; it provides sufficient nutrients by degrading cellular components to enhance the survival of tumors. Osteosarcoma is the most common type of primary malignant bone tumor in children and adolescents. Identification of an improved therapeutic strategy for the treatment of osteosarcoma is urgently required. Osteosarcoma has been primarily treated by chemotherapy and the phenomena of resistance to the therapy has become increasingly common. Doxorubicin (Dox) is a classic chemotherapeutic drug for the treatment of osteosarcoma, and certain studies have suggested that Dox induces autophagy. On the basis of the protective effect of autophagy for tumors, the present study investigated whether U2OS and Saos-2 osteosarcoma cells activate autophagy to reduce Dox-induced apoptosis. Dox was observed to inhibit the growth of U2OS and Saos-2 osteosarcoma cells in a concentration-dependent manner. The results of the western blot analysis demonstrated that Dox induced increased expression levels of the apoptosis-related proteins cleaved caspase-3 and cytochrome c and loss of mitochondrial membrane potential (MMP) in the U2OS and Saos-2 osteosarcoma cells. Furthermore, the results of the western blot analysis also revealed that Dox increased the expression levels of the autophagy-related protein microtubule-associated protein 1 light chain 3 and reduced those of p62 in the U2OS and Saos-2 osteosarcoma cells. In order to determine the effect of autophagy on the apoptosis induced by Dox in the U2OS and Saos-2 osteosarcoma cells, autophagy-related protein (Atg)7 small interfering (si) RNA or the autophagy inhibitor 3-methyladenine (3-MA) alone or combined with Dox was used in U2OS and Saos-2 osteosarcoma cells. The results identified that Atg7 siRNA and the autophagy inhibitor 3-MA significantly elevated the levels of growth inhibition by Dox and markedly increased the expression levels of the apoptosis‑related proteins cleaved caspase-3 and cytochrome c, and reduced the levels of MMP in the U2OS and Saos-2 osteosarcoma cells, which were treated with Dox. These results indicated that autophagy was the protective mechanism used by U2OS and Saos-2 osteosarcoma against Dox-induced apoptosis. The inhibition of autophagy notably increases the levels of apoptosis induced by Dox. This suggested that Dox used in combination with autophagy inhibitors may effectively treat osteosarcoma.

CCN2 enhances resistance to cisplatin-mediating cell apoptosis in human osteosarcoma

Osteosarcoma (OS) is the most common form of malignant bone tumor and is an aggressive malignant neoplasm exhibiting osteoblastic differentiation. Cisplatin is one of the most efficacious antitumor drugs for osteosarcoma patients. However, treatment failures are common due to the development of chemoresistance. CCN2 (also known as CTGF), is a secreted protein that binds to integrins, modulates the invasive behavior of certain human cancer cells. However, the effect of CCN2 in cisplatin-mediated chemotherapy is still unknown. Here, we found that CCN2 was upregulated in human osteosarcoma cells after treatment with cisplatin. Moreover, overexpression of CCN2 increased the resistance to cisplatin-mediated cell apoptosis. In contrast, reduction of CCN2 by CCN2 shRNA promoted the chemotherapeutic effect of cisplatin. We also found that CCN2 provided resistance to cisplatin-induced apoptosis through upregulation of Bcl-xL and survivin. Knockdown of Bcl-xL or survivin removed the CCN2-mediated resistance to apoptosis induced by cisplatin. On the other hand, CCN2 also promoted FAK, MEK, and ERK survival signaling pathways to enhance tumor survival during cisplatin treatment. In a mouse xenograft model, overexpression of CCN2 promoted resistance to cisplatin. However, knockdown of CCN2 increased the therapeutic effect of cisplatin. Therefore, our data suggest that CCN2 might be a critical oncogene of human osteosarcoma for cisplatin-resistance and supported osteosarcoma cell growth in vivo and in vitro.

Structure of human farnesyl pyrophosphate synthase in complex with an aminopyridine bisphosphonate and two molecules of inorganic phosphate

Human farnesyl pyrophosphate synthase (hFPPS) produces farnesyl pyrophosphate, an isoprenoid essential for a variety of cellular processes. The enzyme has been well established as the molecular target of the nitrogen-containing bisphosphonates (N-BPs), which are best known for their antiresorptive effects in bone but are also known for their anticancer properties. Crystal structures of hFPPS in ternary complexes with a novel bisphosphonate, YS0470, and the secondary ligands inorganic phosphate (Pi), inorganic pyrophosphate (PPi) and isopentenyl pyrophosphate (IPP) have recently been reported. Only the co-binding of the bisphosphonate with either PPi or IPP resulted in the full closure of the C-terminal tail of the enzyme, a conformational change that is required for catalysis and that is also responsible for the potent in vivo efficacy of N-BPs. In the present communication, a co-crystal structure of hFPPS in complex with YS0470 and two molecules of Pi is reported. The unusually close proximity between these ligands, which was confirmed by anomalous diffraction data, suggests that they interact with one another, with their anionic charges neutralized in their bound state. The structure also showed the tail of the enzyme to be fully disordered, indicating that simultaneous binding of two Pi molecules with a bisphosphonate cannot induce the tail-closing conformational change in hFPPS. Examination of homologous FPPSs suggested that this ligand-dependent tail closure is only conserved in the mammalian proteins. The prevalence of Pi-bound hFPPS structures in the PDB raises a question regarding the in vivo relevance of Pi binding to the function of the enzyme.

In vitro delivery and controlled release of Doxorubicin for targeting osteosarcoma bone cancer

Drug delivery systems are designed to achieve drug therapeutic index and enhance the efficacy of controlled drug release targeting with specificity and selectivity by successful delivery of therapeutic agents at the desired sites without affecting the non-diseased neighbouring cells or tissues. In this research, we developed and demonstrated a bio-based calcium carbonate nanocrystals carrier that can be loaded with anticancer drug and selectively deliver it to cancer cells with high specificity by achieving the effective osteosarcoma cancer cell death without inducing specific toxicity. The results showed pH sensitivity of the controlled release characteristics of the drug at normal physiological pH 7.4 with approximately 80% released within 1,200 min but when exposed pH 4.8 the corresponding 80% was released in 50 min. This study showed that the DOX-loaded CaCO₃ nanocrystals have promising applications in delivery of anticancer drugs.

Potential health concerns of dietary phosphorus: cancer, obesity, and hypertension

Adult Americans typically consume on average 1400 mg, or more, of phosphorus (P) daily in meals, which almost doubles the recommended dietary allowance. After a meal phosphorus is rapidly absorbed at a high efficiency and hormonal mechanisms act swiftly to maintain the serum inorganic phosphate (Pi) concentration within fairly narrow limits. Both parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF-23) reduce serum phosphate during postprandial periods through homeostatic actions on the kidney. However, it is speculated that exposure of cells to a brief high-serum Pi concentration may signal alterations in cell functions that lead to deleterious effects. Elevation of serum FGF-23 or PTH may also be harmful to specific cell types. Examples of possible adverse health effects include cancer, obesity, and hypertension. Here I review potential mechanisms through which high-P intake may contribute to cell metabolic abnormalities and the development of chronic disease; high-dietary phosphorus, especially from foods processed with phosphate salts, may be associated with these chronic diseases. Further investigation is needed to establish the significance of high-phosphate diets within a large segment of the U.S. population with normal renal function.

Ocotillol Enhanced the Antitumor Activity of Doxorubicin via p53-Dependent Apoptosis

The use of doxorubicin (Dox) was severely constrained by dose-dependent side effects, which might be attenuated by combining a “sensitizer” to decrease its cumulative dosage. In this study, it was investigated whether ocotillol could enhance the antiproliferation activity of Dox. MTT assays and xenograft tumor model were firstly conducted to evaluate the effect of ocotillol on the antitumor activity of Dox. Flow cytometry and Hoechst staining assays were then performed to assess cell apoptosis. Western blot and real-time PCR were finally used to detect the expression of p53 and its target genes. Our results showed ocotillol to enhance Dox-induced cell death in p53 wild-type cancer cells. Compared with Dox alone, Dox with ocotillol (Dox-O) could induce much more cell apoptosis and activate p53 to a much greater degree, which in turn markedly increased expression of proapoptosis genes. The enhanced cytotoxic activity was partially blocked by pifithrin-α, which might be through attenuating the increased apoptosis. Furthermore, ocotillol significantly increased the antitumor activity of Dox in A549 xenograft tumor in nude mice. These findings indicated that ocotillol could potentiate the cytotoxic effect of Dox through p53-dependent apoptosis and suggested that coadministration of ocotillol with Dox might be a potential therapeutic strategy.

Inorganic Phosphate as a Novel Signaling Molecule with Antiproliferative Action in MDA-MB-231 Breast Cancer Cells

Inorganic phosphate (P_i) is an essential nutrient for living organisms. It plays a key role in diverse physiological functions, including osteoblast differentiation and skeletal mineralization. Relevantly, P_i is emerging as an important signaling molecule capable of modulating multiple cellular functions by altering signal transduction pathways, gene expression, and protein abundance in many cell types. To our knowledge, the consequences of elevated P_i on behavior of breast cancer cells have been poorly addressed. In this study we investigate the effects of P_i on proliferation of MDA-MB-231 breast cancer cells. We report that P_i inhibits proliferation of MDA-MB-231 cells by slowing cell cycle progression, without apoptosis occurrence. We found that P_i causes cells to accumulate in G1 phase in a time-dependent manner. Accordingly, G1 accumulation was associated with a decrease of cyclin A and cyclin E and an increase of cell cycle inhibitors p21 and p27 protein levels, respectively. Moreover, the P_i-induced antiproliferative effect was dynamically accompanied by profound changes in ERK1/2 and STAT3 protein and phosphorylation levels in response to P_i. Altogether, our data represent the first evidence of P_i acting as a novel signaling molecule in MDA-MB-231 breast cancer cells, capable of eliciting a strong antiproliferative action and suggest that targeting P_i levels at local sites might represent the rationale for developing novel strategies for therapeutic intervention in triple-negative breast cancer.

Synergistic cytotoxic effects of inorganic phosphate and chemotherapeutic drugs on human osteosarcoma cells

Novel therapeutic approaches are required for the treatment of osteosarcoma. Combination chemotherapy is receiving increased attention in order to identify compounds that may increase the therapeutic index of clinical anticancer drugs. In this regard, naturally occurring molecules with antitumor activity and with limited toxicity to normal tissues have been suggested as possible candidates for investigation of their synergistic efficacy in combination with antineoplastic drugs. Inorganic phosphate (Pi) is an essential nutrient for living organisms. Relevantly, Pi has emerged as an important signaling molecule capable of modulating multiple cellular functions by altering signal transduction pathways, gene expression and protein abundance in many cell types. Previously, we showed that Pi inhibits proliferation and aggressiveness of U2OS human osteosarcoma cells and that Pi is capable of inducing sensitization of osteosarcoma cells to doxorubicin in a p53-dependent manner. In this study, we extended the role of Pi in the chemosensitivity of osteosarcoma cells to other anticancer drugs. Specifically, we report and compare the antiproliferative effects of a combination between Pi and doxorubicin, Taxol^® and 5-fluorouracil (5-FU) treatments. We found that Pi increases the antiproliferative response to both Taxol and doxorubicin to a similar extent. On the other hand, Pi did not potentiate the anticancer effects induced by 5-FU. These effects were paralleled by apoptosis induction and were cell cycle-dependent. The clinical significance of our data and their potential therapeutic applications for improving osteosarcoma treatment are discussed.