Current Medicinal Chemistry - Volume 14, Issue 29, 2007

1α,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], the most active metabolite of vitamin D, exerts its biological effects by binding to a specific intracellular receptor (the vitamin D receptor, VDR) present in target cells. 1,25-(OH)2D3 is involved in a host of cell processes, including calcium homeostasis, cell growth and differentiation, and secretion of hormones. Several studies have explored the role of 1,25-(OH)2D3 in cell growth and differentiation in normal and tumoral mammary gland, in which it shows antiproliferative effects. These effects have been attributed to suppression of growth-stimulatory signals and potentiation of growth-inhibitory signals, leading to changes in cell-cycle regulators as well as to induction of apoptosis. In apparent contrast to these antiproliferative effects, however, several studies have suggested that breast tumor formation may be related to the autocrine/paracrine effects of growth hormone (GH) and prolactin (PRL). The pituitary transcription factor-1 (Pit-1), which in the pituitary is critical to both cell differentiation and PRL and GH transcription, has been recently found in normal and tumoral human breast tissue, with mRNA expression levels significantly higher in tumors than in normal breast. As in the pituitary, Pit-1 regulates mammary GH and PRL secretion, increases cell proliferation and decreases apoptosis. 1,25-(OH)2D3 administration to the MCF-7 human breast adenocarcinoma cell line significantly reduces Pit-1 expression, suggesting that inhibition of Pit-1 expression by 1,25-(OH)2D3 may reduce the increase in proliferation induced by this transcription factor directly or indirectly through increased GH and/or PRL expression. In this review, we evaluate the role of 1,25-(OH)2D3 and Pit- 1/PRL/GH in human breast, and consider the relationships between these factors in normal mammary development and in breast cancer.

Increasing evidence supports the hypothesis that nutrition habits play a critical role in the incidence and growth of colorectal cancer. Among dietary factors, fish-derived n-3 polyunsaturated fatty acids (PUFAs) have gained particular interest, since epidemiological studies have shown a reduced incidence of this cancer in populations consuming high levels of fish. Also a variety of experimental studies and different clinical trials substantiated the beneficial role of n-3 PUFAs. Such an anti-neoplastic activity has been related to the regulatory effects exhibited by n-3 PUFAs on cell proliferation and apoptosis. Anti-angiogenic and anti-metastatic effects have been also reported for these fatty acids. Finally, it has been suggested that they may act as adjuvant therapeutic agents sensitizing tumors, including colon cancer, to different anti-neoplastic drugs. Several molecular mechanisms have been hypothesized to explain their anti-neoplastic action and, in particular, the modulating effect on the expression of several proteins involved in the regulation of cell cycle and apoptosis, such as Bcl-2, Bax, c-Myc seem to play a central role. Their inhibitory action has been also recently suggested for the molecular pathways driven by COX-2 and β-catenin, known to play a major role in the development and progression of colon cancer. The aim of the present review is to analyze the anti-neoplastic effect of n-3 PUFAs towards colon cancer, and examine the molecular mechanisms involved.

The central problem in cancer chemotherapy is the severe toxic side effects of anticancer drugs on healthy tissues. The use of liposomes as drug delivery vehicles for antitumour therapeutics has great potential to revolutionise the future of cancer therapy. As tumour architecture causes liposomes to preferentially accumulate at the tumour site, their use as drug carriers results in the localization of a greater amount of the loaded drug at the tumour site, thus improving cancer therapy and reducing the harmful non-specific side effects of chemotherapeutics. In addition, targeting of liposomal anticancer drugs to antigens expressed or over-expressed on tumour cells provides a very efficient system for increasing the therapeutic indices of the drugs. Animal models allow detailed examination of molecular and physiological basis of diseases and offer a frontline testing system for studying the involvement of specific genes and the efficacy of novel therapeutic approaches. Until recently, the most resorted experimental model of paediatric Neuroblastoma (NB) tumour is the subcutaneous xenograft in nude mice. However, the main disadvantage of this animal model is that it does not reflect the metastatic potential of NB cells, ultimately responsible for poor patient survival. A more realistic view of the clinical potential of targeted therapies could be obtained if a tumour model were available that better reflects the growth of advanced NB in children (i.e. large adrenal gland tumours and multiple small metastatic lesions). All current data support this concept and recommend that orthotopic implantation of tumour cells in recipient animals is mandatory for studies of tumour progression, angiogenesis, invasion, and metastasis. This review will focus on the description of the most clinically relevant animal models established to test the efficacy of targeted liposomal anti-tumour formulations for the treatment of Neuroblastoma.

This paper consists in information about structure, synthesis and biological activity of peptide-acridine/acridone conjugates which are potential anticancer, antiviral and antiprion drugs.

Angiotensin II (AngII) is the major regulator of blood pressure, electrolyte balance, and some endocrine functions related to cardiovascular diseases. Moreover, it has been shown that AngII plays a role in various pathological situations involving tissue remodelling and in cancer. Two distinct subtypes of AngII receptors [type 1 (AT1) and type 2 (AT2)] have been identified, and both belong to the G protein-coupled receptor (GPCR) superfamily. A knowledge of the 3D structure of AT receptors could be of great help in the task of understanding molecular interactions, and in the rational design of specific ligands; however, as GPCRs are membrane-bound proteins, high-resolution structural characterization is still an extremely difficult task. For this reason, great importance has been placed on molecular modelling studies and in particular, on homology modelling (HM) techniques. In this review, we report and analyze the main experimental data and the computational procedures and validation methods used for the construction of the AT receptors, describing in details the most successful results and new trends.

Hsp90 is an evolutionarily conserved and ubiquitously expressed molecular chaperone that mainly modulates, along with a group of co-chaperones, the general platform of protein folding and prevents the nonspecific aggregation of misfolded or unfolded proteins. In the voluminous Hsp90 clientele, a large variety of important regulatory proteins can be identified, including many whose deregulation may lead to cancer initiation and progression, such as the oncogenic clients pp60v-src, Bcr-Abl, mutated p53, ErbB2 (Her-2), Akt, Flt3, HIF-1α and B-Raf. Therefore, inhibition of Hsp90 function offers the prospect of simultaneously disrupting multiple signaling pathways directly implicated in the development of malignant phenotypes. During the last few years, there has been a major focus on the development of Hsp90 specific inhibitors. This started with the discovery that certain natural products could specifically disrupt Hsp90 chaperone activities. The benzoquinone ansamycin antibiotic geldanamycin and its less toxic derivative 17-AAG have been shown to possess strong anti-proliferative and apoptotic activity in cancer cells, whereas 17-AAG has demonstrated potent anti-tumor activity in several human xenograft models, including breast, prostate and colon cancer. In an effort to overcome difficulties with drug toxicity and solubility, a number of novel bioengineered 17-AAG analogues, such as 17-DMAG and IPI-504, and small-molecule inhibitors, including purine and pyrazole derivatives, have emerged from rational drug design followed by high-throughput screening approaches. 17- AAG was the leader inhibitor to enter and successfully complete phase I clinical trials, thus demonstrating that Hsp90 constitutes a valid drug target for cancer therapy. This review includes information on the current model of ternary interactions between Hsp90, client proteins and a vast array of co-chaperones followed by a list of characteristic inhibitors and ongoing clinical trials reported thus far.

Acquisition of a complex immune system during evolution provided organisms with the most effective defense mechanism against “foreign&rdquo or “non-self&rdquo invaders. This efficient protection against pathogens, however, has been achieved at the expense of a higher risk for “self&rdquo-directed reaction or autoimmunity. Establishment of self-tolerance and homeostasis in the immune system is regulated at different physiological stages of immune cells development. The breakdown in discrimination between “self&rdquo and “non-self&rdquo causes an aberrant immune response against autoantigens that promote damage to the “self&rdquo cells and tissue(s), resulting in various autoimmune phenotypes. Whereas activation and clonal proliferation of autoreactive T- and B- lymphocytes underlies the pathogenesis of autoimmune diseases, the mechanism by which self-tolerance is lost and autoimmune responses are induced is not clear yet. Autoimmunity is a multi-step process that occurs as a consequence of complex interaction between genetic susceptibility and non-genetic factors. Programmed cell death, as a key mechanism to regulate immune system function, has a crucial influence on both the selection process of immune cells and the maintenance of this immune tolerance in peripheral repertoire. Thus, defects in apoptotic death pathways may contribute to the development of autoimmune response in susceptible individuals in certain conditions.

Influenza virosomes have proven to be effective vehicles for the delivery of antigens in the vaccination of humans against a number of pathogens. However, their potential as a means for gene delivery has yet to be realized. Chemical modification of viruses is emerging as a new strategy for production of safe and efficient gene delivery systems. Influenza virosomes exhibit many of the features of the virus, such as for cell binding, uptake and endosomal escape, which can be easily engineered into designer delivery vehicles capable of safe, efficient and cell-specific cargo delivery. This review focuses on the next generation of influenza virosomes and highlights aspects of their modification that may lead to simple but effective gene delivery vehicles.