Transfer into a mesothelioma cell line of tumor suppressor gene p16 by cholesterol-based cationic lipids

Biotin-directed assembly of targeted modular lipoplexes and their transfection of human hepatoma cells in vitro

The asialoglycoprotein receptor, which is abundantly and near exclusively expressed on hepatocytes, has received much attention in the design of non-viral hepatotropic DNA delivery systems. Thus, asialoglycoproteins and hexopyranosyl ligands have been coupled to DNA-binding cationic polymers and liposomes in the assembly of complexes intended for uptake by liver parenchymal cells. The aim of the study was to construct a hepatocyte-targeted multimodular liposome-based transfecting complex, in which the biotin-streptavidin interaction provides the cohesive force between the ligand asialorosomucoid and the liposome bilayer, and to evaluate its transfection capabilities in the hepatocyte-derived human transformed cell line HepG2. Dibiotinylated asialoorosomucoid was attached to cationic liposomes constructed from 3beta[N-(N',N'-dimethylaminopropane)-carbamoyl] cholesterol (Chol-T):dioleoylphosphatidylethanolamine:biotinylcholesterylformylhydrazide (MSB1) (48:50:2 mole ratio) through streptavidin interposition. Liposome-pGL3 DNA interactions were studied by gel band shift and ethidium displacement assays. The cytotoxicity of assemblies was evaluated in the HepG2 cell line and transfection capabilities determined by measuring the activity of the transgene luciferase. Binding assays showed that all DNA was liposome associated at a DNA (negative):liposome (positive) charge ratio of 1:1. Accommodation of a streptavidin dibiotinylated asialoorosomucoid assembly was achieved at a DNA:liposome:streptavidin dibiotinylated asialoorosomucoid ratio of 1:4:9 (weight basis). Complexes showed optimal transfection activity at this ratio, which was reduced 10-fold by the presence of the competing ligand asialofetuin. The streptavidin-biotin interaction has been applied for the first time to the assembly of hepatocyte-targeted lipoplexes that display asialoorosomucoid and that are well tolerated by a human hepatoma cell line in which transfection is demonstrably achieved by receptor mediation. Favorable size and charge ratio characteristics suggest that this system may be suitable for in vivo application.

Frequent p16 inactivation by homozygous deletion or methylation is associated with a poor prognosis in Japanese patients with pleural mesothelioma

This study examined the p16 expression status and the P16 gene deletion and methylation status in specimens from Japanese patients with malignant pleural mesothelioma (MPM). Immunohistochemical staining for p16 protein and fluorescence in situ hybridization for the P16 gene were performed using specimens from 30 Japanese patients with primary MPM. The methylation status of the P16 gene was examined in 13 patients whose frozen tumor specimens were available using a methylation-specific PCR assay. Among the 30 patients, the loss of p16 protein expression was observed in 24 patients (80.0%). Twenty-one patients had homozygous deletions, and 9 patients retained the P16 gene. None of the patients with P16 homozygous deletions exhibited p16-positive expression, and 3 patients who retained the P16 gene did not exhibit p16-positive expression. Aberrant P16 methylation was present in two patients with an intact P16 gene but without p16 expression. These results suggest that either a homozygous deletion or methylation is responsible for P16 inactivation. Regarding the prognosis, patients with p16-negative expression had a significantly shorter survival time than those with p16-positive expression (P=0.040). Our study showed that P16 inactivation by homozygous deletions or methylation is a frequent event in Japanese patients with MPMs, relating to poor prognosis. Homozygous deletion is the major cause of P16 inactivation, but methylation also lead to the inactivation of P16 when the P16 alleles are retained.