Cholesteryl butyrate solid lipid nanoparticles (cholbut SLN) can be a delivery system  for the anti-cancer drug butyrate. We have previously shown that cholbut SLN inhibit the adhesion of polymorphonuclear cells (PMNs) to human umbilical vein endothelial cells (HUVEC) and suggested that they may act as an anti-inflammatory agent . Moreover, cholbut SLN inhibited HUVEC adhesiveness to cancer cell lines derived from human colon–rectum, breast, prostate cancers and melanoma. The effect was concentration and time-dependent and exerted on both cancer cells and HUVEC. In addition, these SLN inhibited migration of cancer cells and substantially down-modulated ERK and p38 phosphorylation. Furthermore, cholbut SLN induced E-cadherin and inhibited claudin-1 expression in HUVEC . The aim of the research reported here was to evaluate the activity of cholbut SLN on tumor cell growth using in vitro and in vivo models. We demonstrated, using the MTT test, that cholbut SLN strikingly decreased viability of the colon cancer cell lines HT29, HCT15, and HCT116, and the prostate cancer cell line PC-3. The effect was concentration and time-dependent and exerted on all tumor cell lines, being HCT15, HT29 and PC-3 only minimally sensitive to the free butyrate. The cholbut SLN inhibition detected by the clonogenic assay was consistently higher than that detected by the MTT assay, suggesting that several cells, that were still viable after the cholbut SLN treatment in the MTT assay, were severely damaged since they were unable to proliferate in the clonogenic assay. These effects seemed to be mediated by inhibition of the Akt pathway since cholbut SLN substantially down-modulated Akt phosphorylation on all cell lines and, in PC-3 cells, induced cell cycle arrest in the G2/M phases. To assess the effect of cholbut SLN in vivo, mice were injected i.v. with 1x106 PC3-Luc cells and treated with cholbut SLN or PBS. At time 0, and 7, 14, and 21 days after cell injection, mice were i.p. injected with luciferin and analyzed by in vivo optical imaging to evaluate the tumor cell growth in the lungs. Qualitative and quantitative analyses showed that a progressively increasing luminescent signal was present in the lungs of control mice, while no signal was detected in the lungs of mice treated with cholbut SLN. Histological analysis showed that no metastases were detected in the lungs of the mice treated with cholbut SLN, while disseminated tumor foci were detected in the lungs of the control mice. To further assess the cholbut SLN effect on the tumor growth in vivo, mice were injected s.c. with PC-3 cells and treated with either cholbut SLN or PBS starting when the tumor diameter reached 2 mm. Analysis of the tumor dimension showed that treatment with cholbut SLN substantially delayed the tumor growth compared to that detected in the control mice. These results suggest that cholbut SLN may act as an anti-metastastic drug, and they add a novel mechanism to the anti-tumour activity of this multifaceted drug.
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