The farnesyl transferase inhibitor R115777 (Zarnestra) synergistically enhances growth inhibition and apoptosis induced on epidermoid cancer cells by Zoledronic acid (Zometa) and Pamidronate

The potential role of SNHG16/ miRNA-146a/ TRAF6 signaling pathway in the protective effect of zoledronate against colorectal cancer and associated osteoporosis in mouse model

Bone fracture as a consequence of colorectal cancer (CRC) and associated osteoporosis (OP) is considered a risk factor for increasing the mortality rate among CRC patients. SNHG16/ miRNA-146a/ TRAF6 signaling pathway is a substantial contributor to neoplastic evolution, progression, and metastasis. Here, we investigated the effect of zoledronate (ZOL) on the growth of CRC and associated OP in a mouse model. Thirty Balb/c mice were divided into Naïve, azoxymethane (AOM)/dextran sodium sulfate (DSS), and ZOL groups. Body weight and small nucleolar RNA host gene 16 (SNHG16) expression, microRNA-146a, and TRAF6 in bone, colon, and stool were investigated. Samples of colon and bone were collected and processed for light microscopic, immunohistochemical staining for cytokeratin 20 (CK20), nuclear protein Ki67 (pKi-67), and caudal type homeobox transcription factor 2 (CDx2) in colon and receptor activator of nuclear factor kB (RANK) and osteoprotegerin (OPG) in bone. A computerized tomography (CT) scan of the femur and tibia was studied. ZOL produced a significant decrease in the expression of SNHG16 and TRAF6 and an increase in miRNA-146a in the colon and bone. ZOL administration improved the histopathological changes in the colon, produced a significant decrease in CK20 and Ki-67, and increased CDx2 expressions. In bone, ZOL prevented osteoporotic changes and tumour cell invasion produced a significant decrease in RANK and an increase in OPG expressions, alongside improved bone mineral density in CT scans. ZOL could be a promising preventive therapy against colitis-induced cancer and associated OP via modulation expression of SNHG16, miRNA-146a, and TRAF6.

Synthesis of Tetrasubstituted Phosphorus Analogs of Aspartic Acid as Antiproliferative Agents

An efficient general method for the synthesis of a wide family of α-aminophosphonate analogs of aspartic acid bearing tetrasubstituted carbons is reported through an aza-Reformatsky reaction of α-iminophosphonates, generated from α-aminophosphonates, in an umpolung process. In addition, the α-aminophosphonate substrates showed in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell lines A549 (carcinomic human alveolar basal epithelial cell) and SKOV3 (human ovarian carcinoma). In view of the possibilities in the diversity of the substituents that offer the synthetic methodology, an extensive profile structure-activity is presented, measuring IC₅₀ values up to 0.34 µM in the A549 and 9.8 µM in SKOV3 cell lines.

Zoledronic acid-loaded lipidic nanoparticles enhance apoptosis and attenuate invasiveness by inhibiting epithelial to mesenchymal transition (EMT) in HepG2 cancer cells

The aim of this study was to evaluate the potential of zoledronic acid (ZOL)-loaded lipidic nanoparticles (ZOL-NLCs) in enhancing the efficiency of paclitaxel (Pac) in the context of cytotoxicity, apoptosis, and invasiveness of HepG₂ hepatocellular carcinoma cells. ZOL-NLCs were characterized in terms of zeta potential, particle size, and scanning electron microscope (SEM) as well as cell internalization. To measure the anti-proliferative effects of ZOL-NLCs, annexin-V/PI and MTT assays were employed. Real-time PCR and western blot analysis were performed to identify the molecular mechanisms underlying the apoptosis in response to the studied conditions. Furthermore, the transwell migration assay was applied to clarify the role of applied formulations on the invasiveness of HepG₂ cells. Our results demonstrated that the optimized ZOL had an average particle size of 105 ± 6 nm with a nearly narrow size distribution. The IC₅₀ values for ZOL and ZOL-NLCs were 90 ± 3.1 and 54.6 ± 2.4 µM, respectively. The population of apoptotic cells was increased from 17 ± 2% to 27 ± 4% (p < 0.05) in response to treatment with ZOL-NLCs. ZOL-loaded nanoparticles triggered the mRNA expression of Bax as pro-apoptotic marker and E-cadherin as epithelial one along with a decrease in mesenchymal marker, N-cadherin, and Bcl-xl as an anti-apoptotic marker in HepG₂ cells. These outcomes were consistent with western blot analysis of protein expressions. Besides, ZOL-incorporated lipidic nanoparticles reduced the migration of HepG₂ cells significantly. Our data suggest that the formulation of ZOL into lipidic nanoparticles can be considered a potential therapeutic approach that can enhance the efficacy of Pac chemotherapy.

Bisphosphonate-Based Conjugates and Derivatives as Potential Therapeutic Agents in Osteoporosis, Bone Cancer and Metastatic Bone Cancer

Metastatic bone cancer occurs in every type of cancer but is prevalent in lung, breast, and prostate cancers. These metastases can cause extensive morbidity, including a range of skeletal-related events, often painful and linked with substantial hospital resource usage. The treatment used is a combination of chemotherapy and surgery. However, anticancer drugs are still limited due to severe side effects, drug resistance, poor blood supply, and non-specific drug uptake, necessitating high toxic doses. Bisphosphonates are the main class of drugs utilized to inhibit metastatic bone cancer. It is also used for the treatment of osteoporosis and other bone diseases. However, bisphosphonate also suffers from serious side effects. Thus, there is a serious need to develop bisphosphonate conjugates with promising therapeutic outcomes for treating metastatic bone cancer and osteoporosis. This review article focuses on the biological outcomes of designed bisphosphonate-based conjugates for the treatment of metastatic bone cancer and osteoporosis.

Various pathways of zoledronic acid against osteoclasts and bone cancer metastasis: a brief review

Zoledronic acid (ZA) is one of the most important and effective class of anti-resorptive drug available among bisphosphonate (BP), which could effectively reduce the risk of skeletal-related events, and lead to a treatment paradigm for patients with skeletal involvement from advanced cancers. However, the exact molecular mechanisms of its anticancer effects have only recently been identified. In this review, we elaborate the detail mechanisms of ZA through inhibiting osteoclasts and cancer cells, which include the inhibition of differentiation of osteoclasts via suppressing receptor activator of nuclear factor κB ligand (RANKL)/receptor activator of nuclear factor κB (RANK) pathway, non-canonical Wnt/Ca2+/calmodulin dependent protein kinase II (CaMKII) pathway, and preventing of macrophage differentiation into osteoclasts, in addition, induction of apoptosis of osteoclasts through inhibiting farnesyl pyrophosphate synthase (FPPS)-mediated mevalonate pathway, and activation of reactive oxygen species (ROS)-induced pathway. Furthermore, ZA also inhibits cancer cells proliferation, viability, motility, invasion and angiogenesis; induces cancer cell apoptosis; reverts chemoresistance and stimulates immune response; and acts in synergy with other anti-cancer drugs. In addition, some new ways for delivering ZA against cancer is introduced. We hope this review will provide more information in support of future studies of ZA in the treatment of cancers and bone cancer metastasis.

Pamidronate decreases bilirubin-impaired cell death and improves dentinogenic dysfunction of stem cells from human deciduous teeth

BACKGROUND

Hyperbilirubinemia that occurs in pediatric liver diseases such as biliary atresia can result in the development of not only jaundice in the brain, eyes, and skin, but also tooth abnormalities including green pigmentation and dentin hypoplasia in the developing teeth. However, hyperbilirubinemia-induced tooth impairments remain after liver transplantation. No effective dental management to prevent hyperbilirubinemia-induced tooth impairments has been established.

METHODS

In this study, we focused on pamidronate, which is used to treat pediatric osteopenia, and investigated its effects on hyperbilirubinemia-induced tooth impairments. We cultured stem cells from human exfoliated deciduous teeth (SHED) under high and low concentrations of unconjugated bilirubin in the presence or absence of pamidronate. We then analyzed the effects of pamidronate on the cell death, associated signal pathways, and dentinogenic function in SHED.

RESULTS

We demonstrated that a high concentration of unconjugated bilirubin induced cell death in SHED via the mitochondrial pathway, and this was associated with the suppression of AKT and extracellular signal-related kinase 1 and 2 (ERK1/2) signal pathways and activation of the nuclear factor kappa B (NF-κB) signal pathway. The high concentration of unconjugated bilirubin impaired the in vitro and in vivo dentinogenic capacity of SHED, but not the low concentration. We then demonstrated that pamidronate decreased the bilirubin-induced cell death in SHED via the altered AKT, ERK1/2, and NF-κB signal pathways and recovered the bilirubin-impaired dentinogenic function of SHED.

CONCLUSIONS

Our findings suggest that pamidronate may prevent tooth abnormalities in pediatric patients with hyperbilirubinemia.

Bisphosphonate conjugation for bone specific drug targeting

Bones provide essential functions and are sites of unique biochemistry and specialized cells, but can also be sites of disease. The treatment of bone disorders and neoplasia has presented difficulties in the past, and improved delivery of drugs to bone remains an important goal for achieving effective treatments. Drug targeting strategies have improved drug localization to bone by taking advantage of the high mineral concentration unique to the bone hydroxyapatite matrix, as well as tissue-specific cell types. The bisphosphonate molecule class binds specifically to hydroxyapatite and inhibits osteoclast resorption of bone, providing direct treatment for degenerative bone disorders, and as emerging evidence suggests, cancer. These bone-binding molecules also provide the opportunity to deliver other drugs specifically to bone by bisphosphonate conjugation. Bisphosphonate bone-targeted therapies have been successful in treatment of osteoporosis, primary and metastatic neoplasms of the bone, and other bone disorders, as well as refining bone imaging. In this review, we focus upon the use of bisphosphonate conjugates with antineoplastic agents, and overview bisphosphonate based imaging agents, nanoparticles, and other drugs. We also discuss linker design potential and the current state of bisphosphonate conjugate research progress. Ongoing investigations continue to expand the possibilities for bone-targeted therapeutics and for extending their reach into clinical practice.

FPPS mediates TGF-β1-induced non-small cell lung cancer cell invasion and the EMT process via the RhoA/Rock1 pathway

Farnesyl pyrophosphate synthase (FPPS), a key enzyme in the mevalonate pathway, was recently shown to play a role in cancer progression. However, its role in non-small cell lung cancer (NSCLC) metastasis and the underlying mechanism remain unclear. In this study, FPPS expression was significantly correlated with TNM stage, and metastasis. Inhibition or knockdown of FPPS blocked TGF-β1-induced cell invasion and epithelial-to-mesenchymal transition (EMT) process. FPPS expression of FPPS was induced by TGF-β1 and FPPS promoted cell invasion and EMT via the RhoA/Rock1 pathway. In conclusion, FPPS mediates TGF-β1-induced lung cancer cell invasion and EMT via the RhoA/Rock1 pathway. These findings suggest new treatment strategies to reduce mortality associated with metastasis in patients with NSCLC.

Nano-technology based carriers for nitrogen-containing bisphosphonates delivery as sensitisers of γδ T cells for anticancer immunotherapy

Nitrogen containing bisphosphonates (N-BPs) including zoledronate (ZOL) and alendronate (ALD) inhibit farnesyl diphosphate synthase, and have been shown to have a cytotoxic affect against cancer cells as a monotherapy and to also sensitise tumour cells to destruction by γδ T cells. γδ T cells are a subset of human T lymphocytes and have a diverse range of roles in the immune system including the recognition and destruction of cancer cells. This property of γδ T cells can be harnessed for use in cancer immunotherapy through in vivo expansion or the adoptive transfer of ex vivo activated γδ T cells. The use of N-BPs with γδ T cells has been shown to have a synergistic effect in in vitro, animal and clinical studies. N-BPs have limited in vivo activity due to rapid clearance from the circulation. By encapsulating N-BPs in liposomes (L) it is possible to increase the levels of N-BPs at non-osseous tumour sites. L-ZOL and L-ALD have been shown to have different toxicological profiles than free ZOL or ALD. Both L-ALD and L-ZOL led to increased spleen weight, leucocytosis, neutrophilia and lymphocytopenia in mice after intravenous injection. L-ALD was shown to be better tolerated than L-ZOL in murine studies. Biodistribution studies have been performed in order to better understand the interaction of N-BPs and γδ T cells in vivo. Additionally, in vivo therapy studies have shown that mice treated with both L-ALD and γδ T cells had a significant reduction in tumour growth compared to mice treated with L-ALD or γδ T cells alone. The use of ligand-targeted liposomes may further increase the efficacy of this combinatory immunotherapy. Liposomes targeting the αvβ6 integrin receptor using the peptide A20FMDV2 had a greater ability than untargeted liposomes in sensitising cancer cells to destruction by γδ T cells in αvβ6 positive cancer cell lines.

Synergistic Antiproliferative Effects of Zoledronic Acid and Fluvastatin on Human Pancreatic Cancer Cell Lines: An in Vitro Study

Bisphosphonates and statins are known to have antitumor activities against different types of cancer cell lines. In the present study, we investigated the antiproliferative effects of the combination of zoledronic acid (ZOL), a bisphophosphonate, and fluvastatin (FLU), a statin, in vitro on two types of human pancreatic cancer cell lines, Mia PaCa-2 and Suit-2. The pancreatic cancer cell lines were treated with ZOL and FLU both individually and in combination to evaluate their antiproliferative effects using WST-8 cell proliferation assay. In this study, we demonstrated a potent synergistic antiproliferative effect of both drugs when used in combination in both cell lines. Moreover, we studied the molecular mechanism behind this synergistic effect, which was inhibited by the addition of the mevalonate pathway products, farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP). Furthermore, we aimed to determine the effect of ZOL and FLU combination on RhoA and Ras guanosine 5'-triphosphate (GTP)-proteins. The combination induced a marked accumulation in RhoA and unprenylated Ras. GGPP and FPP reversed the increase in the amount of both proteins. These results indicated that the combination treatment impaired RhoA and Ras signaling pathway by the inhibition of geranylgeranylation and/or farnesylation. This study provides a potentially effective approach for the treatment of pancreatic cancer using a combination treatment of ZOL and FLU.

miR-29s: a family of epi-miRNAs with therapeutic implications in hematologic malignancies

A wealth of studies has highlighted the biological complexity of hematologic malignancies and the role of dysregulated signal transduction pathways. Along with the crucial role of genetic abnormalities, epigenetic aberrations are nowadays emerging as relevant players in cancer development, and significant research efforts are currently focusing on mechanisms by which histone post-translational modifications, DNA methylation and noncoding RNAs contribute to the pathobiology of cancer. As a consequence, these studies have provided the rationale for the development of epigenetic drugs, such as histone deacetylase inhibitors and demethylating compounds, some of which are currently in advanced phase of pre-clinical investigation or in clinical trials. In addition, a more recent body of evidence indicates that microRNAs (miRNAs) might target effectors of the epigenetic machinery, which are aberrantly expressed or active in cancers, thus reverting those epigenetic abnormalities driving tumor initiation and progression. This review will focus on the broad epigenetic activity triggered by members of the miR-29 family, which underlines the potential of miR-29s as candidate epi-therapeutics for the treatment of hematologic malignancies.

Proteomic analysis of zoledronic-acid resistant prostate cancer cells unveils novel pathways characterizing an invasive phenotype

Proteomic analysis identified differentially expressed proteins between zoledronic acid-resistant and aggressive DU145R80 prostate cancer (PCa) cells and their parental DU145 cells. Ingenuity Pathway Analysis (IPA) showed a strong relationship between the identified proteins within a network associated with cancer and with homogeneous cellular functions prevalently related with regulation of cell organization, movement and consistent with the smaller and reduced cell-cell contact morphology of DU145R80 cells. The identified proteins correlated in publically available human PCa genomic data with increased tumor expression and aggressiveness. DU145R80 exhibit also a clear increase of alpha-v-(αv) integrin, and of urokinase receptor (uPAR), both included within the same network of the identified proteins. Interestingly, the actin-rich structures localized at the cell periphery of DU145R80 cells are rich of Filamin A, one of the identified proteins and uPAR which, in turn, co-localizes with αv-integrin, in podosomes and/or invadopodia. Notably, the invasive feature of DU145R80 may be prevented by blocking anti-αv antibody. Overall, we unveil a signaling network that physically links the interior of the nucleus via the cytoskeleton to the extracellular matrix and that could dictate PCa aggressiveness suggesting novel potential prognostic markers and therapeutic targets for PCa patients.

Combination of zoledronic acid and serine/threonine phosphatase inhibitors induces synergistic cytotoxicity and apoptosis in human breast cancer cells via inhibition of PI3K/Akt pathway

The aim of this study was to investigate the cytotoxic and apoptotic effects of zoledronic acid (ZA) in combination with serine/threonine protein phosphatase inhibitors, calyculin-A (CA) and okadaic acid (OA), in human MCF-7 and MDA-MB-231 breast cancer cells. XTT cell viability assay was used to evaluate cytotoxicity. DNA fragmentation and caspase-3/7 activity assays were performed to evaluate apoptosis. Activities of phosphatase 1 (PP1) and phosphatase 2A (PP2A) were measured by serine/threonine phosphatase ELISA kit. Expression levels of PI3K, p-PI3K, Akt, p-Akt, Bcl-2, p-Bcl-2, Bad, and p-Bad proteins were evaluated by Western blot analysis. Combination of ZA with either CA or OA showed synergistic cytotoxicity and apoptosis as compared to any agent alone in both MCF-7 and MDA-MB-231 breast cancer cells. Combination treatment also resulted in inhibition of both PP1 and PP2A activities. Both agents used alone or in combination did not induce significant changes in total PI3K, Akt, Bcl-2, and Bad expressions, while p-PI3K, p-Akt, p-Bcl-2, and p-Bad levels were reduced by the combination treatment as compared to agents alone. Moreover, apoptotic effect of combination treatment was significantly inhibited in the presence of LY294002, a specific PI3K inhibitor, in both breast cancer cell lines. In conclusion, synergistic apoptotic effect of the combination treatment is correlated with the block of the PI3K/Akt signal pathway in breast cancer cells.

Nanoparticles for the delivery of zoledronic acid to prostate cancer cells: a comparative analysis through time lapse video-microscopy technique

Time-lapse live cell imaging is a powerful tool for studying the responses of cells to drugs. Zoledronic acid (ZOL) is the most potent aminobiphosphonate able to induce cell growth inhibition at very low concentrations. The lack of clear evidence of ZOL-induced anti-cancer effects is likely due to its unfavorable pharmacokinetic profile. The use of nanotechnology-based formulations allows overcoming these limitations in ZOL pharmaco-distribution. Recently, stealth liposomes (LIPOs) and new self-assembly PEGylated nanoparticles (NPs) encapsulating ZOL were developed. Both the delivery systems showed promising anticancer activity in vitro and in vivo. In this work, we investigated the cytostatic effect of these novel formulations (LIPOs and NPs) compared with free ZOL on 2 different prostate cancer cell lines, PC 3 and DU 145 and on prostate epithelial primary cells EPN using time lapse video-microscopy (TLVM). In PC3 cells, free ZOL showed a significant anti-proliferative effect but this effect was lower than that induced by LIPOs and NPs encapsulating ZOL; moreover, LIPO-ZOL was more potent in inducing growth inhibition than NP-ZOL. On the other hand, LIPO-ZOL slightly enhanced the free ZOL activity on growth inhibition of DU 145, while the anti-proliferative effect of NP-ZOL was not statistically relevant. These novel formulations did not induce anti-proliferative effects on EPN cells. Finally, we evaluated cytotoxic effects on DU145 where, LIPO-ZOL induced the highest cytotoxicity compared with NP-ZOL and free ZOL. In conclusion, ZOL can be transformed in a powerful anticancer agent, if administered with nanotechnology-based formulations without damaging the healthy tissues.

Significance of KRAS/PAK1/Crk pathway in non-small cell lung cancer oncogenesis

Background

Key effector(s) of mutated KRAS in lung cancer progression and metastasis are unknown. Here we investigated the role of PAK1/Crk axis in transduction of the oncogenic KRAS signal in non-small cell lung cancer (NSCLC).

Methods

We used NSCLC clinical specimens to examine the correlation among KRAS mutations (codon 12, 13 and 61); PAK1/Crk axis activation [p-PAK1(Thr423), p-Crk(Ser41)]; and adhesion molecules expression by immunohistochemistry. For assessing the role of proto-oncogene c-Crk as a KRAS effector, we inhibited KRAS in NSCLC cells by a combination of farnesyltransferase inhibitor (FTI) and geranylgeranyltransferase inhibitor (GGTI) and measured p-Crk-II(Ser41) by western blotting. Finally, we disrupted the signaling network downstream of KRAS by blocking KRAS/PAK1/Crk axis with PAK1 inhibitors (i.e., IPA-3, FRAX597 or FRAX1036) along with partial inhibition of all other KRAS effectors by prenylation inhibitors (FTI + GGTI) and examined the motility, morphology and proliferation of the NSCLC cells.

Results

Immunohistochemical analysis demonstrated an inverse correlation between PAK1/Crk phosphorylation and E-cadherin/p120-catenin expression. Furthermore, KRAS mutant tumors expressed higher p-PAK1(Thr423) compared to KRAS wild type. KRAS prenylation inhibition by (FTI + GGTI) completely dephosphorylated proto-oncogene c-Crk on Serine 41 while Crk phosphorylation did not change by individual prenylation inhibitors or diluent. Combination of PAK1 inhibition and partial inhibition of all other KRAS effectors by (FTI + GGTI) dramatically altered morphology, motility and proliferation of H157 and A549 cells.

Conclusions

Our data provide evidence that proto-oncogene c-Crk is operative downstream of KRAS in NSCLC. Previously we demonstrated that Crk receives oncogenic signals from PAK1. These data in conjunction with the work of others that have specified the role of PAK1 in transduction of KRAS signal bring forward the importance of KRAS/PAK1/Crk axis as a prominent pathway in the oncogenesis of KRAS mutant lung cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1360-4) contains supplementary material, which is available to authorized users.

Antitumor activity of pamidronate in breast cancer cells transformed by low doses of α-particles and estrogen in vitro

Human breast cancer is a major cause of global morbidity and mortality in women and it is a process that involves numerous molecular and cellular alterations attributed to environmental substances and agents such as hormones. Bisphosphonates, such as pamidronate, are potent antiresorptive drugs used to the treatment of metabolic bone disease, exerting anti-proliferative, anti-migratory and apoptotic effects. The aim of this study was to evaluate gene and protein expression involved in these processes. An in vitro model was developed with the MCF-10F immortalized breast epithelial cell line exposed to low radiation doses of high LET (linear energy transfer) α-particles (150 keV/µm) and cultured in the presence of 17β-estradiol (estrogen). This model consisted of the following cell lines: i) MCF-10F, normal; ii) Alpha3, non-malignant; iii) Alpha5, pre-tumorigenic, and iv) Tumor2, derived from Alpha5 injected into the nude mice. Our previous results have shown that Alpha5 and Tumor2 increased cell proliferation, anchorage independency, invasive capabilities and tumor formation in nude mice in comparison to control. Expression of the gene (RT-qPCR) and protein (western blotting, flow cyto-metry) was measured. The results indicated that pamidronate decreased invasion, migration and Rho-A, c-Ha-ras, p53, Serpin-1, Caveolin-1, Bcl-xL and NFκB gene and protein expression. Thus, it seems that pamidronate may impinge upon cellular proliferation, invasion, metastasis and apoptosis and it may exert antitumor activity in breast cancer cells transformed by low doses of α-particles and estrogen in vitro.

Effects of bisphosphonate zoledronic acid in hepatocellular carcinoma, depending on mevalonate pathway

BACKGROUND AND AIM

Zoledronic acid (ZOL) is a nitrogen-containing bisphosphonate and is used to reduce cancer-induced osteolysis. We reported previously that ZOL delayed both the growth and pain progression of bone metastases from hepatocellular carcinoma. The present study was designed to evaluate the effects of ZOL on hepatoma cell lines and the molecular mechanisms of such effects.

METHODS

Cell viability assay, scratch assay, immunohistochemistry, Western blotting, and flow cytometry analysis were performed using Huh7 and HepG2 cells treated with and without ZOL.

RESULTS

ZOL reduced cell growth in a dose-dependent manner and prevented cell migration when used at a concentration exceeding 10 μM. Immunohistochemistry showed that the inhibitory effects of ZOL on hepatoma cell progression was not due to the suppression of Ras and RhoA expression but due to inhibition of their translocation from the cytosol to the cell membrane, which terminates mevalonate pathway. Immunoblotting and flow cytometry showed that ZOL inhibited the mitogen-activated protein kinase pathway (MAPK) and induced apoptosis of hepatoma cells.

CONCLUSIONS

Our results indicated that ZOL prevented cell growth and metastasis based on direct antitumor effects in hepatoma cells. The use of ZOL could not only suppress the progression to bone metastatic lesions but also prevented growth of primary hepatocellular carcinoma.

Multiple myeloma-related bone disease: state-of-art and next future treatments

SUMMARY 

Multiple myeloma (MM) is a plasma cell malignancy associated with the development of life-threatening and/or severe osteolytic lesions, which significantly worsen the quality of life of affected patients. MM-related bone disease (BD) is the result of an overwhelming osteoclastic activity, while osteoblast-mediated bone formation is inhibited. Bisphosphonates are still the mainstay of therapy for BD. However, these drugs are associated with mid long-term sequelae. In this work, we review the pathogenesis and currently available therapies of MM-related BD. We describe the most recent and promising findings that may translate in changing the clinical practice in the next future.

Myeloid-derived suppressor cells in multiple myeloma: pre-clinical research and translational opportunities

Immunosuppressive cells have been reported to play an important role in tumor-progression mainly because of their capability to promote immune-escape, angiogenesis, and metastasis. Among them, myeloid-derived suppressor cells (MDSCs) have been recently identified as immature myeloid cells, induced by tumor-associated inflammation, able to impair both innate and adaptive immunity. While murine MDSCs are usually identified by the expression of CD11b and Gr1, human MDSCs represent a more heterogeneous population characterized by the expression of CD33 and CD11b, low or no HLA-DR, and variable CD14 and CD15. In particular, the last two may alternatively identify monocyte-like or granulocyte-like MDSC subsets with different immunosuppressive properties. Recently, a substantial increase of MDSCs has been found in peripheral blood and bone marrow (BM) of multiple myeloma (MM) patients with a role in disease progression and/or drug resistance. Pre-clinical models recapitulating the complexity of the MM-related BM microenvironment (BMM) are major tools for the study of the interactions between MM cells and cells of the BMM (including MDSCs) and for the development of new agents targeting MM-associated immune-suppressive cells. This review will focus on current strategies for human MDSCs generation and investigation of their immunosuppressive function in vitro and in vivo, taking into account the relevant relationship occurring within the MM–BMM. We will then provide trends in MDSC-associated research and suggest potential application for the treatment of MM.

Acquired resistance to zoledronic acid and the parallel acquisition of an aggressive phenotype are mediated by p38-MAP kinase activation in prostate cancer cells

The nitrogen-containing bisphosphonates (N-BP) zoledronic acid (ZOL) inhibits osteoclast-mediated bone resorption, and it is used to prevent skeletal complications from bone metastases. ZOL has also demonstrated anticancer activities in preclinical models and, recently, in cancer patients, highlighting the interest in determining eventual mechanisms of resistance against this agent. In our study, we selected and characterised a resistant subline of prostate cancer (PCa) cells to better understand the mechanisms, by which tumour cells can escape the antitumour effect of ZOL. DU145R80-resistant cells were selected in about 5 months using stepwise increasing concentrations of ZOL from DU145 parental cells. DU145R80 cells showed a resistance index value of 5.5 and cross-resistance to another N-BP, pamidronate, but not to the non-nitrogen containing BP clodronate. Notably, compared with DU145 parental cells, DU145R80 developed resistance to apoptosis and anoikis, as well as overexpressed the anti-apoptotic protein Bcl-2 and oncoprotein c-Myc. Moreover, DU145R80 cells underwent epithelial to mesenchymal transition (EMT) and showed increased expression of the metalloproteases MMP-2/9, as well as increased invading capability. Interestingly, compared with DU145, DU145R80 cells also increased the gene expression and protein secretion of VEGF and the cytokines Eotaxin-1 and IL-12. At the molecular level, DU145R80 cells showed strong activation of the p38-MAPK-dependent survival pathway compared with parental sensitive cells. Moreover, using the p38-inhibitor SB203580, we completely reversed the resistance to ZOL, as well as EMT marker expression and invasion. Furthermore, SB203580 treatment reduced the expression of VEGF, Eotaxin-1, IL-12, MMP-9, Bcl-2 and c-Myc. Thus, for the first time, we demonstrate that the p38-MAPK pathway can be activated under continuous extensive exposure to ZOL in PCa cells and that the p38-MAPK pathway has a critical role in the induction of resistance, as well as in the acquisition of a more aggressive and invasive phenotype.

Bisphosphonates and cancer: what opportunities from nanotechnology?

Bisphosphonates (BPs) are synthetic analogues of naturally occurring pyrophosphate compounds. They are used in clinical practice to inhibit bone resorption in bone metastases, osteoporosis, and Paget's disease. BPs induce apoptosis because they can be metabolically incorporated into nonhydrolyzable analogues of adenosine triphosphate. In addition, the nitrogen-containing BPs (N-BPs), second-generation BPs, act by inhibiting farnesyl diphosphate (FPP) synthase, a key enzyme of the mevalonate pathway. These molecules are able to induce apoptosis of a number of cancer cells in vitro. Moreover, antiangiogenic effect of BPs has also been reported. However, despite these promising properties, BPs rapidly accumulate into the bone, thus hampering their use to treat extraskeletal tumors. Nanotechnologies can represent an opportunity to limit BP accumulation into the bone, thus increasing drug level in extraskeletal sites of the body. Thus, nanocarriers encapsulating BPs can be used to target macrophages, to reduce angiogenesis, and to directly kill cancer cell. Moreover, nanocarriers can be conjugated with BPs to specifically deliver anticancer agent to bone tumors. This paper describes, in the first part, the state-of-art on the BPs, and, in the following part, the main studies in which nanotechnologies have been proposed to investigate new indications for BPs in cancer therapy.

Analysis of molecular mechanisms and anti-tumoural effects of zoledronic acid in breast cancer cells

Zoledronic acid (ZOL) is the most potent nitrogen-containing bisphosphonate (N-BPs) that strongly binds to bone mineral and acts as a powerful inhibitor of bone resorption, already clinically available for the treatment of patients with osteolytic metastases. Recent data also suggest that ZOL, used in breast cancer, may provide more than just supportive care modifying the course of the disease, though the possible molecular mechanism of action is still unclear.As breast cancer is one of the primary tumours with high propensity to metastasize to the bone, we investigated, for the first time, differential gene expression profile on Michigan Cancer Foundation-7 (MCF-7) breast cancer cells treated with low doses of ZOL (10 μM). Microarrays analysis was used to identify, describe and summarize evidence regarding the molecular basis of actions of ZOL and of their possible direct anti-tumour effects. We validated gene expression results of specific transcripts involved in major cellular process by Real Time and Western Blot analysis and we observed inhibition of proliferation and migration through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Matrigel assay. We then focused on changes in the cytoskeletal components as fibronectin 1 (FN1), actin, and anti angiogenic compounds as transforming growth factor-β1 (TGF-β1) and thrombospondin 1 (THBS1). The up-regulation of these products may have an important role in inhibiting proliferation, invasion and angiogenesis mediated by ZOL.

Isoprenyl-thiourea and urea derivatives as new farnesyl diphosphate analogues: synthesis and in vitro antimicrobial and cytotoxic activities

A series of new isoprenyl-thiourea and urea derivatives were synthesized by the reaction of alkyl or aryl isothiocyanate or isocyanate and primary amines. The structures of the compounds were established by (1)H NMR, (13)C NMR, MS, HRMS and elemental analysis. The new compounds were screened for in vitro antimicrobial activity against seven strains representing different types of gram-positive and gram-negative bacteria. More than a third of the synthesized compounds showed variable inhibition activities against the tested strains. Best antimicrobial activities were found for those thiourea analogues with 3-methyl-2-butenyl, isobutyl or isopentyl groups and aromatic rings possessing electron withdrawing substituents. The new compounds were also subjected to a preliminary screening for antitumoral activity. The presence of a highly lipophilic group and an electron withdrawing group in the aromatic rings enhanced anticancer activity of the synthesized compounds, showing in most cases more activity than that of the controls.

Stathmin is involved in the cooperative effect of Zoledronic acid and gefitinib on bone homing breast cancer cells in vitro

Zoledronic acid (Zol) is the most potent inhibitor of bone resorption among the bisphosphonates and is commonly used for inhibiting bone metastasis. However, it remains unclear whether Zol provides a survival benefit. Recent findings indicate that epidermal growth factor (EGF) signaling is an important mediator of bone metastasis. Thus, we examined the combined effects of Zol and an EGF receptor-tyrosine kinase inhibitor, gefitinib, on the proliferation and invasion of a bone-seeking clone and the breast cancer cell line MDA-MB-231. Combined treatment with Zol and gefitinib synergistically inhibited both invasion and cell proliferation of the bone-seeking clone, but not those of the MDA-MB-231 cells. Two-dimensional difference gel electrophoresis and mass spectrometry demonstrated that stathmin was down-regulated during these cooperative effects. Stathmin is a signal transduction regulatory factor which plays an important role in cell division and malignant tumor development. Our data suggest that stathmin may be a promising target molecule for blocking bone metastasis of breast cancer.

Nanotechnologies to use bisphosphonates as potent anticancer agents: the effects of zoledronic acid encapsulated into liposomes

Zoledronic acid (ZOL) is a potent amino-bisphosphonate used for the treatment of bone metastases with recently reported antitumor activity. However, the short plasma half-life and rapid accumulation in bone limits the use of ZOL as an antitumor agent in extraskeletal tissues. Therefore, we developed stealth liposomes encapsulating ZOL (LipoZOL) to increase extraskeletal drug availability. Compared to free ZOL, LipoZOL induced a stronger inhibition of growth of a range of different cancer cell lines in vitro. LipoZOL also caused significantly larger inhibition of tumor growth and increased the overall survival in murine models of human prostate cancer and multiple myeloma, in comparison with ZOL. Moreover, a strong inhibition of vasculogenetic events without evidence of necrosis in the tumor xenografts from prostate cancer was recorded after treatment with LipoZOL. We demonstrated both antitumor activity and tolerability of LipoZOL in preclinical animal models of both solid and hematopoietic malignancies, providing a rationale for early exploration of use of LipoZOL as a potential anticancer agent in cancer patients.

FROM THE CLINICAL EDITOR

The short plasma half-life and rapid accumulation in bone limits the use of zoledronic acid as an antitumor agent in extraskeletal tissues. Therefore, stealth liposomes encapsulating ZOL (LipoZOL) have been developed to increase extraskeletal drug availability.

CCN1, a candidate target for zoledronic acid treatment in breast cancer

CCN1, also known as CYR61, is a survival and proangiogenic factor overexpressed in about 30% of invasive breast carcinomas, and particularly in triple-negative breast carcinomas (TNBC). CCN1 expression in breast cancer promotes tumorigenicity, metastasis, antihormone, and chemoresistance. TNBCs often develop bone metastasis, thus the vast majority of patients receive bisphosphonate treatment as a companion to chemotherapy. Zoledronic acid (ZOL), a bisphosphonate currently in use, inhibits bone resorption, prevents development of new osteolytic lesions induced by tumor metastasis, and has a direct antitumor activity in breast cancer cells and tumors. We have shown that ZOL inhibits anchorage independent growth as well as branching and morphogenesis in CCN1 overexpressing cells. However, the mechanism is not yet well understood. In this study, we investigate the effect of ZOL in breast cancer cells with high and undetectable CCN1 expression levels. We show that CCN1-expressing cells are more sensitive to ZOL, that ZOL induces downregulation of the CCN1 promoter activity and CCN1 protein expression in a dose-dependent manner, and that ZOL is associated with a decrease in phosphorylated Akt and translocation of FOXO3a, a negative regulator of CCN1 expression, to the nucleus. Deletion of the FOXO3a binding site in the CCN1 promoter prevents ZOL inhibition of the CCN1 promoter activity showing that FOXO3a transcriptional activation is necessary for ZOL to induce CCN1 inhibition. This study provides evidence that ZOL targets the proangiogenic factor (CCN1) through FOXO3a and reveals a new mechanism of ZOL action in breast cancer cells.

Statins can modulate effectiveness of antitumor therapeutic modalities

Despite significant, frequently very strong, antiproliferative and tumoricidal effects of statins demonstrated in vitro, their antitumor effects in animal models are modest, and their efficacy in clinical trials has not been proven. As such, statins seem unlikely to be ever regarded as antitumor agents. However, statins are regularly taken by many elderly cancer patients for the prevention of cardiovascular events. Owing to their pleiotropic effects in normal and tumor cells, statins interact in various ways with many antitumor treatment modalities, either potentiating or diminishing their effectiveness. Elucidation of these interactions might affect the choice of treatment to be planned in cancer patients as some combinations might be contraindicated, whereas others might elicit potentiated antitumor effects but at a cost of increased general toxicity. Some other combinations might induce either comparable or even stronger antitumor effects, but with a beneficial concomitant reduction of specific side effects. Most of the studies reviewed in this article have been carried in vitro or in experimental tumor models, but clinical relevance of the findings is also discussed.

Bisphosphonates for osteoporosis treatment are associated with reduced breast cancer risk

BACKGROUND

Bisphosphanates are used primarily for the prevention and treatment of osteoporosis, and are also indicated for osseous complications of malignancy. In addition to their bone resorption properties, the most commonly used nitrogen-containing bisphosphonate compounds also inhibit protein prenylation, and thus may exert anti-tumour properties.

METHODS

To evaluate whether the use of these drugs may be associated with cancer, specifically breast cancer, we conducted a population-based case-control study in Wisconsin from 2003 to 2006. Participants included 2936 incident invasive breast cancer cases and 2975 population controls aged < 70 years. Bisphosphonate use and potential confounders were assessed by interview.

RESULTS

Using multivariable logistic regression, the odds ratio for breast cancer in current bisphosphonate users compared with non-users was 0.67 (95% confidence interval 0.51-0.89). Increasing duration of use was associated with a greater reduction in risk (P-trend=0.01). Risk reduction was observed in women who were not obese (P-interaction=0.005).

CONCLUSION

These results are suggestive of an additional benefit of the common use of bisphosphonates, in this instance, the reduction in breast cancer risk.

The level of ATP analog and isopentenyl pyrophosphate correlates with zoledronic acid-induced apoptosis in cancer cells in vitro

Bisphosphonates are potent inhibitors of osteoclast function widely used to treat excessive bone resorption associated, e.g., with bone metastases. They have also antitumor activity. However, it is unclear whether this reflects an indirect effect via inhibition of bone resorption or a direct antitumor effect. Nitrogen-containing bisphosphonates (N-BPs), including zoledronic acid (ZOL), act by inhibiting farnesyl pyrophosphate synthase (FPPS). The mevalonate pathway is blocked and the accumulation of isopentenyl pyrophosphate (IPP) consequently occurs. IPP is conjugated to AMP to form a novel ATP analog (ApppI). The present study was undertaken to clarify whether IPP and/or ApppI has a direct involvement in apoptosis caused by ZOL in different cancer cell lines. There are marked differences in ZOL-induced ApppI formation between different cancer cell lines. On this basis, we selected three cancer cell lines that differ significantly from each other in their ZOL-induced IPP and ApppI accumulation: human estrogen-dependent (MCF7) and estrogen-independent (MDA-MB 436) breast cancer cell lines and a human myeloma cell line (RPMI 8226). The amount of IPP/ApppI correlated with the capacity of cells to undergo apoptosis. Geranylgeraniol (GGOH), an intermediate of mevalonate metabolism, blocks both IPP and ApppI formation and to some degree ZOL-induced apoptosis in a cell line-dependent manner. In addition, lovastatin (LOV), an inhibitor of the enzyme HMGCoA reductase, completely blocks IPP/ApppI formation as determined by mass spectrometry analysis, but enhances apoptosis. In conclusion, the current data suggest that ZOL-induced IPP/ApppI formation can contribute to ZOL-induced apoptosis. This mechanism and the inhibition of protein prenylation, both outcomes of FPPS inhibition in mevalonate pathway, seem to act in concert in ZOL-induced apoptosis in cancer cells.

Zoledronate inhibits the proliferation, adhesion and migration of vascular smooth muscle cells

Bisphosphonates, which are extensively used in bone-related disorders, have been reported to inhibit atherosclerosis and neointimal hyperplasia. In the present study, we investigated the effects of a bisphosphonate, zoledronate, on the proliferation, adhesion, migration and microstructure of vascular smooth muscle cells (VSMCs) from Sprague-Dawley rats. It was shown that zoledronate suppressed VSMCs proliferation after 48 h cultivation in a dose depend manner, most obviously at concentrations above 10 microM. Cell cycle analysis indicated that zoledronate inhibited the proliferation of VSMCs via cell cycle arrest at S/G2/M phase. This inhibition was not associated with cell death. In a modified Boyden chamber model, it was shown that zoledronate dose-dependently inhibited VSMCs adhesion to collagen and migration stimulated by platelet-derived growth factor-BB. Western blot analysis suggested that zoledronate significantly inhibited the phosphorylation of focal adhesion kinase. Furthermore, we observed that more and more VSMCs changed from a bipolar appearance to a globular shape under inverted light microscope as zoledronate concentration increased from 0.1 to 100 microM. Images under transmission electron microscope confirmed this morphological change, and many electron density bodies were observed in zoledronate-treated VSMCs. These findings indicated that bisphosphonates' effects of suppressing atherosclerosis and neointimal hyperplasia might be due to inhibition of VSMCs, at least for zoledronate.

Citrinin induces apoptosis in mouse embryonic stem cells

The mycotoxin citrinin (CTN) is a natural contaminant in foodstuffs and animal feeds, and exerts cytotoxic and genotoxic effects on various mammalian cells. CTN causes cell injury, including apoptosis. However, its precise regulatory mechanisms of action, particularly in stem cells and embryos, are currently unclear. Recent studies show that CTN has cytotoxic effects on mouse embryonic stem cells and blastocysts, and is associated with defects in their subsequent development, both in vitro and in vivo. Experiments with the embryonic stem cell line, ESC-B5, disclose that CTN induces apoptosis via several mechanisms, including ROS generation, increased cytoplasmic free calcium levels, intracellular nitric oxide production, enhanced Bax/Bcl-2 ratio, loss of mitochondrial membrane potential, cytochrome c release, activation of caspase-9 and caspase-3, and p21-activated protein kinase 2 and c-Jun N-terminal protein kinase activation. Additional studies show that CTN promotes cell death via inactivation of the HSP90/multi-chaperone complex and subsequent degradation of Ras and Raf-1, further inhibiting anti-apoptotic processes such as the Ras-->ERK signal transduction pathway. On the basis of these findings, we propose a model for CTN-induced cell injury signalling cascades in embryonic stem cells and blastocysts.

Inhibition of geranylgeranyl diphosphate synthase induces apoptosis through multiple mechanisms and displays synergy with inhibition of other isoprenoid biosynthetic enzymes

Inhibitors of isoprenoid synthesis are widely used for treatment of human diseases, including hypercholesterolemia and osteoporosis, and they have the potential to be useful for treatment of cancer. Statin drugs inhibit the enzyme HMG-CoA reductase, whereas nitrogenous bisphosphonates have more recently been shown to inhibit farnesyl disphosphate synthase. In addition, our laboratory has recently developed several potent and specific bisphosphonate inhibitors of geranylgeranyl diphosphate synthase, including digeranyl bisphosphonate. Because all three enzymes fall in the same biosynthetic pathway and many of the biological effects are due to depletion of downstream products, we hypothesized that simultaneous inhibition of these enzymes would result in synergistic growth inhibition. In this study, we show that inhibition of geranylgeranyl diphosphate synthase induces apoptosis in K562 leukemia cells. This induction of apoptosis is in part dependent upon both geranylgeranyl diphosphate depletion and accumulation of farnesyl diphosphate. Combinations of either lovastatin or zoledronate with digeranyl bisphosphonate synergistically inhibited growth and induced apoptosis. These combinations also potently inhibited cellular geranylgeranylation. These results support the potential for combinations of multiple inhibitors of isoprene biosynthesis to inhibit cancer cell growth or metastasis at clinically achievable concentrations.

Zoledronic acid is unable to induce apoptosis, but slows tumor growth and prolongs survival for non-small-cell lung cancers

BACKGROUND

Although zoledronic acid (ZOL), a third-generation nitrogen-containing bisphosphonate, has been identified as an attractive therapeutic agent against breast cancer, prostate cancer, multiple myeloma as well as small-cell lung cancer (SCLC), as best as we are aware, the anti-tumor effect of ZOL upon non-small-cell lung cancer (NSCLC) remains to be effectively investigated. This study examined the effects of ZOL upon the line-1 tumor cell, using a murine lung adenocarcinoma cell line similar to the behavior of human lung adenocarcinoma.

METHODS

We investigated the anti-tumor effects of ZOL (3-100 microM) on line-1 tumor cells in vitro, including cellular proliferation, by means of an MTT assay, cell-cycle analysis by flow cytometry and by assessing the level of apoptosis by annexin V/propidium iodide (PI) and 4'-6-diamidino-2-phenylindole (DAPI) staining. Further, we evaluated the growth and survival of line-1 tumor cells following ZOL treatment (1 microg/kg/week) using an animal model. We also examined the in vivo cell-cycle pattern using lacZ-expressing line-1 cells (line-1/lacZ).

RESULTS

ZOL significantly slowed the line-1 tumor growth in a dose-dependent manner in vitro. The treated line-1 tumor cells typically arrested at the S/G2/M-phase of the cell-cycle following ZOL exposure, but no apoptotic cells could be detected by either annexin V/PI or DAPI staining. When the ZOL was washed out, the drug-inhibited cells continued to proliferate again and the cell-cycle prolongation elicited earlier by the drug, then disappeared. Within 72-96 h following drug removal, the cell-cycle of the treated cells revealed a similar distribution to that of the untreated controls. In vivo studies demonstrated that ZOL significantly slowed the line-1 tumor growth. Indeed, mice lived significantly longer when they had been ZOL-treated than was the case for untreated mice (p<0.05). Using line-1/lacZ cells, the in vivo cell-cycle distribution of line-1 tumor cells subsequent to ZOL exposure revealed S/G2/M-phase arrest that was identical to the in vitro culture.

CONCLUSIONS

ZOL maintains the potential to reduce tumor burden and prolong survival for murine pulmonary adenocarcinoma. The flow cytometrical analysis of cell-cycle demonstrated that ZOL induces no apoptosis but is able to arrest line-1 tumor cells at the S/G2/M-phase. Although the clinical relevance of these results warrants verification for human lung cancer patients, ZOL combined with chemotherapy and/or radiotherapy appears to be a new therapeutic strategy for the effective treatment of NSCLC.

The role of bisphosphonates in the management of patients that have cancer

Bisphosphonates are pharmacologic agents widely used in people for managing pathologic bone resorptive conditions. Based on their physicochemical properties, bisphosphonates concentrate within areas of active bone remodeling and induce osteoclast apoptosis. Appropriate use of bisphosphonates for treating companion animals requires a thorough understanding of how bisphosphonates exert their biologic effects. This review article highlights general properties of bisphosphonates, including their pharmacology, mechanisms of action, adverse side effects, anticancer mechanisms, surrogate markers for assessing response, and potential clinical utility for treating dogs and cats diagnosed with malignant skeletal tumors.

Bisphosphonates in cancer therapy

Bisphosphonates are the standard of care in the treatment of malignant bone diseases, because of their ability to inhibit osteoclast-mediated bone destruction. We review here preclinical evidence that bisphosphonates also exert direct antitumour effects and antiangiogenic properties. Furthermore, we describe new insights on how bisphosphonates may act synergistically in combination with antineoplastic drugs or gammadelta T cells to exhibit antitumour activity. These findings reveal new exciting possibilities to fully exploit the antitumour potential of bisphosphonates in the clinical practice.

Citrinin induces apoptosis via a mitochondria-dependent pathway and inhibition of survival signals in embryonic stem cells, and causes developmental injury in blastocysts

The mycotoxin CTN (citrinin), a natural contaminant in foodstuffs and animal feeds, has cytotoxic and genotoxic effects on various mammalian cells. CTN is known to cause cell injury, including apoptosis, but the precise regulatory mechanisms of CTN action, particularly in stem cells and embryos, are currently unclear. In the present paper, I report that CTN has cytotoxic effects on mouse embryonic stem cells and blastocysts, and is associated with defects in their subsequent development, both in vitro and in vivo. Experiments in embryonic stem cells (ESC-B5) showed that CTN induces apoptosis via ROS (reactive oxygen species) generation, increased Bax/Bcl-2 ratio, loss of MMP (mitochondrial membrane potential), induction of cytochrome c release, and activation of caspase 3. In this model, CTN triggers cell death via inactivation of the HSP90 [a 90 kDa isoform of the HSP (heat-shock protein) family proteins]/multichaperone complex and subsequent degradation of Ras and Raf-1, further inhibiting anti-apoptotic processes, such as the Ras-->ERK (extracellular-signal-regulated kinase) signal transduction pathway. In addition, CTN causes early developmental injury in mouse ESCs and blastocysts in vitro. Lastly, using an in vivo mouse model, I show that consumption of drinking water containing 10 muM CTN results in blastocyst apoptosis and early embryonic developmental injury. Collectively, these findings show for the first time that CTN induces ROS and mitochondria-dependent apoptotic processes, inhibits Ras-->ERK survival signalling via inactivation of the HSP90/multichaperone complex, and causes developmental injury in vivo.

R115777 (Zarnestra)/Zoledronic acid (Zometa) cooperation on inhibition of prostate cancer proliferation is paralleled by Erk/Akt inactivation and reduced Bcl-2 and bad phosphorylation

Zoledronic acid (ZOL) has proved activity in bone metastases from prostate cancer through inhibition of mevalonate pathway and of prenylation of intracellular proteins. We have reported that ZOL synergizes with R115777 farnesyltransferase inhibitor (FTI, Zarnestra) in inducing apoptosis and growth inhibition on epidermoid cancer cells. Here, we have studied the effects of the combination of these agents in prostate adenocarcinoma models and, specifically, on androgen-independent (PC3 and DU145) and -dependent (LNCaP) prostate cancer cell lines. We have found that ZOL and R115777 were synergistic in inducing both growth inhibition and apoptosis in prostate adenocarcinoma cells. These effects were paralleled by disruption of Ras-->Erk and Akt survival pathways, consequent decreased phosphorylation of both mitochondrial bcl-2 and bad proteins, and caspase activation. Finally, ZOL/R115777 combination induced cooperative effects also in vivo on tumor growth inhibition of prostate cancer xenografts in nude mice with a significant survival increase. These effects were paralleled by enhanced apoptosis and inactivation of both Erk and Akt. In conclusions, the combination between ZOL and FTI leads to enhanced anti-tumor activity in human prostate adenocarcinoma cells likely through a more efficacious inhibition of ras-dependent survival pathways and consequent bcl-related proteins-dependent apoptosis.

AZD3409 inhibits the growth of breast cancer cells with intrinsic resistance to the EGFR tyrosine kinase inhibitor gefitinib

AKT and MAPK signaling are involved in the resistance of breast cancer cells to the EGFR tyrosine kinase inhibitor gefitinib. RAS proteins are upstream mediators that transfer messages from surface receptors to intracellular signal transducers including MAPK and AKT pathways. AZD3409 is a novel prenyl inhibitor that has shown activity against both farnesyl transferase and geranylgeranyl transferase in isolated enzyme studies. We explored the activity of AZD3409 on breast cancer cell lines with high (SK-Br-3), intermediate (MDA-MB-361) or low (MDA-MB-468) sensitivity to gefitinib. We found that AZD3409 inhibits the growth of breast cancer cells in a dose-dependent manner, with the MDA-MB-468 and MDA-MB-361 cell lines showing higher sensitivity as compared with SK-Br-3 cells. Treatment with AZD3409 produced a significant reduction in the levels of activation of AKT in the three cell lines. AZD3409 also induced an increase in the expression of p27kip-1 and of hypophosphorylated forms of pRb2 in MDA-MB-468 cells that was associated with accumulation of cells in G0/G1 and the appearance of a sub-G1 peak suggestive of apoptosis. In contrast, AZD3409 produced a G2 arrest associated with reduced expression of pRb2 in MDA-MB-361 cells. A synergistic anti-tumor effect was observed when MDA-MB-468 or MDA-MB-361 cells were treated with both AZD3409 and gefitinib, whereas this combination was only additive in SK-Br-3 cells. However, treatment of breast cancer cells with AZD3409 and gefitinib did not produce a more significant blockade of AKT signaling as compared with gefitinib alone. These data suggest that AZD3409 might be active in gefitinib-resistant breast carcinoma.

CdSe quantum dots induce apoptosis in human neuroblastoma cells via mitochondrial-dependent pathways and inhibition of survival signals

Quantum dots (QDs) may be useful as novel luminescent markers, but their cytotoxicity has not been fully investigated. In this report, we demonstrate that CdSe-core QDs can induce apoptotic biochemical changes, including JNK activation, loss of mitochondrial membrane potential, mitochondrial release of cytochrome c and activation of caspase-9 and caspase-3 in the IMR-32 human neuroblastoma cell line. Importantly, treatment of IMR-32 cells with CdSe-core QD triggered an increase in reactive oxygen species (ROS) and inhibited survival-related signaling events, such as decreased Ras and Raf-1 protein expression and decreased ERK activation. These apoptotic biochemical changes were not detected in cells treated with ZnS-coated CdSe QDs. Collectively, these results demonstrate that CdSe-core QD treatment of IMR-32 cells induced JNK activation and mitochondrial-dependent apoptotic processes while inhibiting Ras-->ERK survival signaling and that a ZnS coating could effectively reduce QD cytotoxicity.

New insights into the role of T cells in the vicious cycle of bone metastases

PURPOSE OF REVIEW

Bone metastases interact with the bone microenvironment. Cancer cells modulate the functions of osteoblasts and osteoclasts to induce new bone formation or bone resorption, leading to secondary stimulation of tumor development. Recent findings suggest the involvement of T cells in this process.

RECENT FINDINGS

Bone metastatic cancer cells produce factors such as parathyroid hormone-related protein, interleukin-7, and interleukin-8 that can recruit or activate T cells. T cells are involved in bone remodeling and can induce osteoclastic resorption. Bone resorption releases transforming growth factor-beta, however, which could suppress T-cell antitumor immune responses. Bisphosphonate antiresorptive drugs are the approved treatment for solid tumor bone metastases. They have recently been found to activate the cytolytic activity of gammadelta T cells. Thus, inhibitors of transforming growth factor-beta or antiresorptive therapies may be effective enhancers of antitumor immune responses in bone.

SUMMARY

T cells at the site of bone metastases may be functionally suppressed by factors in the bone microenvironment. Instead of acting against tumor cells, they may increase bone resorption, making bone a privileged site for tumor growth.

Mechanisms of Disease: preclinical reports of antineoplastic synergistic action of bisphosphonates

For patients with malignant bone disease, bisphosphonate therapy is the standard treatment. Preclinical and preliminary clinical data suggest that bisphosphonates have direct or indirect antitumor effects: they affect growth-factor release, cancer-cell adhesion, invasion and viability, angiogenesis, and apoptosis of cancer cells. These effects might be enhanced through co-administration with chemotherapy agents, biological agents, or both. We survey the biochemical pathways and molecular targets of bisphosphonates, and discuss the molecular mechanisms of these antitumor effects, as well as the documented antineoplastic preclinical effects of bisphosphonates used in combination with cytotoxic and biological drugs. Moreover, the positive interactions between bisphosphonates and farnesyltransferase inhibitors, KIT receptor tyrosine kinase inhibitors (e.g. imatinib mesylate) and cyclo-oxygenase-2 inhibitors are discussed in relation to their potential synergistic and additive effects. We briefly discuss identification of new molecular targets of bisphosphonates from genomic and proteomic analysis, and highlight the cellular consequences of drug-related enzyme inhibition.