sr-31747 and Disease-Models--Animal

SR31747A is a recently described sigma receptor ligand that binds SR31747A-binding protein 1 (SR-BP) and emopamil-binding protein (EBP) (also called the sigma 1 receptor and the human sterol isomerase (HSI), respectively), and has immunoregulatory and antiproliferative activities. To further investigate its antitumour activity and focusing on cancers, which are sensitive to the molecule, we measured the proliferation of different human epithelial breast or prostate cancer cell lines following in vitro and in vivo SR31747A treatment. Firstly, in vitro, we found that nanomolar concentrations of SR31747A dramatically inhibited cell proliferation in both hormono-responsive and -unresponsive cancer cell lines. Secondly, tumour development was significantly decreased in mice treated with SR31747A. In an attempt to decipher the SR31747A mode of action, we found that the two binding sites may not fully account for this activity. Indeed, while competitive experiments indicated that EBP prevails in mediating SR31747A antiproliferative activity, an analysis of the expression of both receptors indicated that the cellular sensitivity to SR31747A is not correlated with either EBP or SR-BP expression. These data suggest that additional binding sites may exist. Preliminary binding studies demonstrated that SR31747A also binds to sigma 2, a protein that has not yet been cloned, but which is considered as a potential marker of the proliferative status of tumour cells. Altogether, our data demonstrate the antitumoural activity of SR31747A both in vitro and in vivo in two different cancer models, broaden the spectrum of its binding proteins and enhance the potential for further therapeutic development of the molecule.

Topics: Animals; Antineoplastic Agents; Breast Neoplasms; Cell Division; Cells, Cultured; Cyclohexanes; Disease Models, Animal; Humans; Ligands; Male; Mice; Mice, Nude; Neoplasm Transplantation; Neoplasms, Experimental; Prostatic Neoplasms; Receptors, sigma; Tumor Cells, Cultured

There are several subtypes of sigma receptor, one of which is found throughout the immune system. SR31747A is a unique sigma ligand that possesses potent immune modulatory properties. Previous in vivo studies have documented that administration of SR31747A in murine models of sepsis resulted in decreased proinflammatory (IL-1, IL-6, TNF-alpha) and increased anti-inflammatory (IL-10) response (serum, splenocyte). Studies regarding the effect of this sigma ligand on purified macrophages are lacking. We therefore sought to investigate the effect of SR31747A in LPS-stimulated murine macrophages (RAW 264.7).. RAW cells were incubated at 2.5 x 10(5) cells/well; controls were incubated with media alone, experimental groups contained LPS (0.01 microg) and SR31747A (1 nM, 10 nM, 100 nM, 1 microM, 10 microM). Supernatant and cells were harvested at 24 and 48 h. Concentrations of nitric oxide (Greiss reaction) and IL-10 were determined in the supernatant; cellular IL-10 mRNA was assessed.. SR31747A induced a dose-dependent reduction in NO and IL-10 protein release in LPS-stimulated murine macrophages. The decrease in IL-10 protein synthesis was paralleled by a significant dose-dependent reduction in IL-10 mRNA.. SR31747A is a novel immunomodulator that down regulates nitric oxide and IL-10 protein and mRNA expression. This in vitro reduction of IL-10 protein and mRNA expression is in contrast to previous in vivo murine studies. These data suggest that peripheral macrophages are not the source of the increased anti-inflammatory (IL-10) response induced by SR31747A.

Topics: Animals; Cyclohexanes; Disease Models, Animal; In Vitro Techniques; Interleukin-10; Ligands; Lipopolysaccharides; Macrophages; Mice; Nitric Oxide Synthase; Receptors, sigma; RNA, Messenger; Sepsis; Time Factors