Budesonide loaded nanoparticles with pH-sensitive coating for improved mucosal targeting in mouse models of inflammatory bowel diseases.

The purpose of this study was to investigate the therapeutic potential of budesonide loaded nanocarriers for the treatment of inflammatory bowel disease (IBD). First, budesonide was encapsulated in poly(lactic-co-glycolic) acid (PLGA) nanoparticles by an oil in water (O/W) emulsion technique. A second batch of the same nanoparticles was additionally coated with a pH-sensitive methyl-methacrylate-copolymer. The particle sizes of the plain and the coated PLGA were 200±10.1nm and ~240±14.7nm, respectively. As could be shown in vitro, the pH-sensitive coating prevented premature drug release at acidic pH and only releases the drug at neutral to slightly alkaline pH. The efficacy of both coated and plain nanoparticle formulations was assessed in different acute and chronic colitis mouse models, also in comparison to an aqueous solution of the drug. The dose was always the same (0.168mg/kg). It was found that delivery by coated PLGA nanoparticles alleviated the induced colitis significantly better than by plain PLGA particles, which was already more effective than treatment with the same dose of the free drug. These data further corroborate the potential of polymeric nanocarriers for targeted drug delivery to the inflamed intestinal mucosa, and that this concept can still be further improved regarding the oral route of administration by implementing pH-dependent drug release characteristics.

VDR microRNA expression and epigenetic silencing of vitamin D signaling in melanoma cells.

Malignant melanoma cells express the vitamin D receptor (VDR). However, some melanoma cell lines fail to respond to the antiproliferative effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). We reported previously that out of seven melanoma cell lines analyzed, three cell lines (MeWo, SK-Mel28, SM) respond to the antiproliferative effects of 1,25(OH)2D3, while the others (SK-Mel5, SK-Mel25, IGR, Meljuso) are resistant. It was the aim of this study to investigate whether epigenetic mechanisms are of importance for the abrogation of vitamin D signaling in vitamin D resistant melanoma cells. We used the histone deacetylase inhibitor (HDACI) trichostatin A (TSA) and the DNA methyltransferase inhibitor (DNMTI) 5-azacytidine (5-Aza) to elucidate the effects of protein acetylation and of DNA hypermethylation on 1,25(OH)2D3-induced effects on cell proliferation, respectively. Additionally we analyzed the expression of VDR microRNA in 1,25(OH)2D3-responding and resistant melanoma cells. TSA and 5-Aza exerted dose- and time-dependent antiproliferative effects on melanoma cell lines. Interestingly, combination therapy with 1,25(OH)2D3 and TSA exerted synergistic antiproliferative effects in a 1,25(OH)2D3-resistant melanoma cell line (IGR) (p<0.05). Combination therapy with 1,25(OH)2D3 and 5-Aza resulted in synergistic (MeWo after 72 h; p<0.05) or additive (other melanoma cell lines analyzed) antiproliferative effects. Additionally, we could show that VDR mRNA expression is relatively high in two of three 1,25(OH)2D3-responsive melanoma cells as compared to resistant cells, moreover this relatively high VDR expression is associated with low expression of miRNA125b in MeWo and SK-Mel28 cells. Our results suggest that the endogenous VDR mRNA level is inversely associated with expression of miRNA125b in melanoma cell lines analyzed. Moreover, miRNA125b may be involved in the regulation of VDR expression and in the resistance against 1,25(OH)(2)D(3) in melanoma cells. It can be speculated whether miRNA125b may be of prognostic importance and/or may represent a therapeutic target for malignant melanoma. Drugs that influence epigenetic mechanisms might be promising therapeutics for the treatment of metastasized malignant melanoma, alone or in combination with antiproliferative or cytotoxic agents such as 1,25(OH)2D3.

Challenge and promise: the role of miRNA for pathogenesis and progression of malignant melanoma.

microRNAs are endogenous noncoding RNAs that are implicated in gene regulation. More recently, miRNAs have been shown to play a pivotal role in multiple cellular processes that interfere with tumorigenesis. Here we summarize the essential role of microRNAs for human cancer with special focus on malignant melanoma and the promising perspectives for cancer therapies.