Current Cancer Drug Targets - Volume 10, Issue 7, 2010

Bone metastases contribute to morbidity in patients with common cancers, and conventional therapy provides only palliation and can induce systemic side effects. The development of nanostructured delivery systems that combine carriers with bone-targeting molecules can potentially overcome the drawbacks presented by conventional approaches. We have recently developed biodegradable, biocompatible nanoparticles (NP) made of a conjugate between poly (D,Llactide- co-glycolic) acid and alendronate, suitable for systemic administration, and directly targeting the site of tumorinduced osteolysis. Here, we loaded NP with doxorubicin (DXR), and analyzed the in vitro and in vivo activity of the drug encapsulated in the carrier system. After confirming the intracellular uptake of DXR-loaded NP, we evaluated the antitumor effects in a panel of human cell lines, representative for primary or metastatic bone tumors, and in an orthotopic mouse model of breast cancer bone metastases. In vitro, both free DXR and DXR-loaded NP, (58-580 ng/mL) determined a significant dose-dependent growth inhibition of all cell lines. Similarly, both DXR-loaded NP and free DXR reduced the incidence of metastases in mice. Unloaded NP were ineffective, although both DXR-loaded and unloaded NP significantly reduced the osteoclast number at the tumor site (P = 0.014, P = 0.040, respectively), possibly as a consequence of alendronate activity. In summary, NP may act effectively as a delivery system of anticancer drugs to the bone, and deserve further evaluation for the treatment of bone tumors.

The present study deals with the evaluation of the efficacy of oxaliplatin and paclitaxel combination as a potential strategy in controlling HNSCC cell proliferation and the assessment of correlation between occurrence of apoptosis and changes in expression of survivin (IAP). The panel cell lines included two HNSCC cell lines (Cal27 and NT8e) and one normal cell line (293) with differential level of survivin expression in accordance with chemosensitivity. The cytotoxicity and effect of drugs on apoptosis was determined, separately and in combination. Combined treatment of cells with paclitaxel and oxaliplatin resulted in significantly higher cytotoxicity as compared to individual single drug treatment. Cytotoxicity was prominent in paclitaxel to oxaliplatin (pacl-oxal) sequence treatment with an approximate two-fold increase in apoptosis as compared to oxaliplatin to paclitaxel (oxal-pacl) sequence treatment. Paclitaxel treatment also caused increased survivin expression showing reduced apoptosis at low concentration. Oxaliplatin, when combined with paclitaxel, decreased the survivin level with increased cell death. Inhibition of survivin by a small interfering RNA (siRNA) method also increased the sensitivity of the cancer cell lines to paclitaxel whereas over-expression of survivin in the transfected 293-cell line provided resistance. In conclusion, the interaction between drugs was synergistic and schedule-dependent. Survivin played a critical role in paclitaxel resistance through the suppression of apoptosis, and a significant induction of apoptosis was observed when oxaliplatin was combined with paclitaxel at least in part by the down-regulation of survivin.

Platinum-based anticancer drugs are a cornerstone of the current antineoplastic treatment. However, their use is limited by the onset of peripheral nervous system dysfunction, which can be severe and persistent over a long period of time. Among the several hypotheses proposed to explain this side effect, evidence is increasing that dorsal root ganglia (DRG) oxidative stress can be an important pathogenetic mechanism and, possibly, a therapeutic target to limit the severity of platinum-induced peripheral neurotoxicity but preserving the anticancer effectiveness. In fact, DRG energy failure has been suggested as a result of mitochondrial DNA-platinum binding and several antioxidant drugs have been tested in pre-clinical experiments and clinical trials. In this review, an update on the current knowledge on the relationship existing between oxidative stress and platinum drugs peripheral neurotoxicity will be given.

Src was the first proto-oncogene to be discovered. Since then the role of Src has been extensively studied in vitro. Src is a key regulator of multiple signal transduction pathways and plays a significant part in cellular transformation. Dysfunction of Src, through overexpression or increased activation, has profound effects on basic cellular functions. Elevated Src expression and/or activation is evident across a wide range of solid tumour types, highlighting its place in carcinogenesis and making it an attractive therapeutic target. In this review, we discuss in vitro and in vivo data examining the role of Src in the different cellular processes involved in oncogenesis and metastasis, covering the association of Src with increased cell proliferation and survival, decreased cellular adhesion, increased cell motility and invasiveness, accelerated/advanced angiogenesis and pathogenic bone activity. We also review evidence gathered from human tumour tissue and translational research studies that further substantiates the role of Src in oncogenesis. A summary of Src inhibitors currently being developed and trialled as therapeutic agents is provided to underline Src as a potential molecular target for solid tumour therapy. Further clinical data are needed to conclusively demonstrate that Src inhibitors have clinical utility in the treatment of solid tumors.

The aim of this study was to demonstrate that oligo-branched peptides can be effective either for spotlighting tumor cells that overexpress peptide receptors, or for killing them, simply by exchanging the functional moiety coupled to the conserved receptor-targeting core. Tetra-branched peptides containing neurotensin (NT) sequence are described here as selective targeting agents for human colon, pancreas and prostate cancer. Fluorophore-conjugated peptides were used to measure tumor versus healthy tissue binding in human surgical samples, resulting in validation of neurotensin receptors as highly promising tumor-biomarkers. Drug-armed branched peptides were synthesized with different conjugation methods, resulting in uncleavable adducts or drug-releasing molecules. Cytotoxicity on human cell lines from colon (HT-29), pancreas (PANC-1) or prostate (PC-3) carcinoma indicated branched NT conjugated with MTX and 5-FdU as the most active agents on PANC-1 (EC50 4.4e-007 M) and HT-29 (1.1e-007 M), respectively. Tetra-branched NT armed with 5-FdU was used for in vivo experiments in HT-29-xenografted mice and produced a 50% reduction in tumor growth with respect to animals treated with the free drug. An unrelated branched peptide carrying the same drug was completely ineffective. In vitro and in vivo results indicated that branched peptides are valuable tools for tumor selective targeting.

The focus of this study was to develop additive or synergistic agents to chemosensitize the existing chemotherapeutic drug in human non-small cell lung cancer (NSCLC). In this study employing analyses of the NF-κB/ I-κB kinase (IKK) signal cascade in a number of NSCLC cell lines, we report the identification and characterization of parthenolide. Parthenolide is a sesquiterpene lactone that can antagonize paclitaxel-mediated NF-κB nuclear translocation and activation through selectively targeting I-κB kinase (IKK) activity. Our results showed that parthenolide dramatically lowered the effective dose of Paclitaxel needed to induce cytotoxicity of a wide range of NSCLC cell lines. An examination of pathways common to Paclitaxel and parthenolide signaling revealed that this synergy was related to modulation of the NF-κB/ I-κB kinase (IKK) signal cascade through IKKß. Parthenolide alone induced apoptosis via the mitochondria/ caspase pathway. Moreover, in a human orthotopic NSCLC xenograft model, a well-tolerated combination induces tumor regression. These data strengthen the rationale for the use of parthenolide to decrease the apoptotic threshold via a caspase-dependent process and support the use of concurrent low doses of paclitaxel in the treatment of NSCLC with paclitaxel chemoresistance.

There is a growing body of evidence that Wnt signaling, which is already known to play a critical role in various types of cancer, also has a vital function in B cell neoplasias, particularly in chronic lymphocytic leukemia (CLL). It is known that Wnt proteins are overexpressed in primary CLL cells and several physiological inhibitors are partly inactivated in this disease. Furthermore, β-catenin is upregulated upon Wnt stimulation and cooperates with the transcription factor lymphoid enhancer binding factor-1 (LEF-1). LEF-1 is excessively overexpressed in CLL cells by more than 3,000- fold compared to normal B cells. Moreover, LEF-1 could be identified as an important regulator of pathophysiologically relevant genes in CLL, and several Wnt/β-catenin signaling components substantially influence CLL cell survival. In this review we summarize the current state of knowledge about Wnt/β-catenin/LEF-1 signaling in CLL. Following a short overview of current treatment concepts in CLL, we briefly describe Wnt signaling in human cancers. We then discuss recent progress in understanding regulation of the Wnt/β-catenin/LEF-1 signaling pathway in this disease. Based on the present scientific evidence we highlight which components of this important signaling pathway could serve as therapeutic targets in CLL. We then present previous results gained from experimental approaches to target different parts of the Wnt/β-catenin/LEF-1 cascade. Together with potentially promising approaches we also critically reflect on the kind of difficulties and problems that may arise using such strategies.

CTLA-4 is a negative regulator of the proliferation and the effector function of T-cells. Therefore, it might be important to determine its expression on tumor cells and T-lymphocytes from cancer patients, to investigate its role in initiating and maintaining the neoplastic pathogenesis. CTLA-4 expression was detected in breast tissue by immunohistochemical staining and RT-PCR in 60 patients with breast cancer and 30 normal controls. The levels of CTLA-4 on T lymphocytes in 33 of the patients and 27 of the control group were determined by flow cytometry. Isolated peripheral blood mononuclear cells (PBMCs) were stimulated with phytohaemagglutinin (PHA). Stimulation index and IL-2 level in the cell culture supernatant were measured by MTT assay and ELISA method, respectively. Patients showed strong expression of CTLA-4 in the tumor cells of all specimens at both the protein and mRNA level, but only weakly positive or negative expression in normal breast tissue. Patients with higher mRNA level of CTLA-4 had obvious axillary lymph nodes metastases and higher clinical stage. Spontaneous expression of CD3+CTLA-4+ on PBMCs of tumor patients was also significantly higher than that of the controls. Moreover, PBMCs derived from patients with high expression of CD3+CTLA-4+ T-cells showed poor responsiveness to PHA stimulation and lower IL-2 production. Therefore, abnormal expression and dysregulation of CTLA-4 could partly explain the mechanism of evasion of anti-tumor immune responses in breast cancer patients and therefore highlight its importance in the development and progression of breast cancer.

The pathways downstream of ErbB-family proteins are very important in BC, especially when considering treatment with onco-protein inhibitors. We studied and implemented dynamic simulations of four downstream pathways and described the fragment of the signaling network we evaluated as a Molecular Interaction Map. Our simulations, enacted using Ordinary Differential Equations, involved 242 modified species and complexes, 279 reversible reactions and 110 catalytic reactions. Mutations within a single pathway tended to be mutually exclusive; only inhibitors acting at, or downstream (not upstream), of a given mutation were active. A double alteration along two distinct pathways required the inhibition of both pathways. We started an analysis of sensitivity/robustness of our network, and we systematically introduced several individual fluctuations of total concentrations of independent molecular species. Only very few cases showed significant sensitivity. We transduced the ErbB2 over-expressing BC line, BT474, with the HRAS (V12) mutant, then treated it with ErbB-family and phosphorylated MEK (MEKPP) inhibitors, Lapatinib and U0126, respectively. Experimental and simulation results were highly concordant, showing statistical significance for both pathways and for two respective endpoints, i.e. phosphorylated active forms of ERK and Akt, p one tailed = .0072 and = .0022, respectively. Working with a complex 39 basic species signaling network region, this technology facilitates both comprehension and effective, efficient and accurate modeling and data interpretation. Dynamic network simulations we performed proved to be both practical and valuable for a posteriori comprehension of biological networks and signaling, thereby greatly facilitating handling, and thus complete exploitation, of biological data.

DNA topoisomerase II enzymes regulate essential cellular processes by altering the topology of chromosomal DNA. These enzymes function by creating transient double-stranded breaks in the DNA molecule that allow the DNA strands to pass through each other and unwind or unknot tangled DNA. Because of the integral role of topoisomerases in regulating DNA metabolism, these enzymes are vital for cell survival. Several clinically active antitumor agents target these enzymes. Mammalian cells contain two topoisomerase II isozymes that are encoded by different genes: topoisomerase IIα and IIβ. Although, both isozymes are homologous and exhibit similar catalytic activity, they are differentially regulated and are involved in distinct biological functions. The topoisomerase IIα and topoisomerase IIβ enzymes are regulated by post-translational modifications, including sumoylation, ubiquitination and phosphorylation. These posttranslational modifications influence the biologic and catalytic activity of the enzyme and affect sensitivity of cells to topoisomerase II-targeted drugs. In this review, we describe how the catalytic and biologic activity of the topoisomerase II enzyme is regulated and discuss the mechanisms by which chemotherapeutic agents that target these enzymes function. Given the potential importance of site-specific modifications, in particular phosphorylation, in regulating sensitivity to topoisomerase II-targeted drugs, we discuss the potential role of altered topoisomerase II phosphorylation in development of drug resistance, which is often a limiting factor in the treatment of cancer.

CXCR4 is a chemokine receptor implicated in the metastatic process. The CXCR4 ligand, CXCL12, was shown to bind the CXCR7 receptor also, a recently deorphanized chemokine receptor whose signalling pathway and function are still controversial. This study was conducted to determine patients clinic-pathological factors and outcome according to the expressions of CXCR4 and CXCR7 in renal cell carcinoma (RCC). CXCR4 and CXCR7 expression were evaluated in 223 RCC patients through immunohistochemistry; moreover CXCR4 and CXCR7 were detected in 49 other consecutive RCC patients through RT- PCR. CXCR4 expression was low in 42/223 RCC (18,8%), intermediate in 71/223 (31,9%) and high in 110/223 (49,3%). CXCR7 expression was low in 44/223 RCC patients (19,8%), intermediate in 65/223 (29,1%) and high in 114/223 (51,1%). High CXCR4 and high CXCR7 expression predicted shorter disease free survival. In multivariate analysis, high CXCR4 expression (p= 0.0061), high CXCR7 (p= 0.0194) expression and the concomitant high expression of CXCR4 and CXCR7 (p= 0.0235) are independent prognosis factors. Through RT-PCR, CXCR4 was overexpressed in 36/49 and CXCR7 in 33/49 samples correlating with symptoms at diagnosis and lymph nodes status. So we can hypothesize that CXCR4 and CXCR7, singularly evaluated and in combination, are valuable prognostic factors in RCC patients.

Tumors are invariably less well-oxygenated than the normal tissues from which they arise. Hypoxia-inducible factor-1 (HIF-1), a key transcriptional regulator, plays a central role in the adaptation of tumor cells to hypoxia by activating the transcription of genes, which regulate several biological processes including angiogenesis, cell proliferation, survival, glucose metabolism and migration. The expression, activity and stability of HIF-1 are not only induced in response to reduced oxygen availability but also modulated through PI-3K, MAPKs, autocrine signaling pathways, E3 ubiquitin ligases, and other regulators. The regulators and effects of HIF-1 in cancer have intensively provided us a new clue for the HIF-1 targeting anticancer therapy. This review evaluates the HIF-1 structure, the regulation mechanisms, the functions in cancer and corresponding anticancer strategies.