Effective transgene expression without toxicity by intraperitoneal administration of PEG-detachable polyplex micelles in mice with peritoneal dissemination.

Block copolymer of poly(ethylene glycol)-block-poly{N-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (PEG-P[Asp(DET)]) has been originally introduced as a promising gene carrier by forming a nanomicelle with plasmid DNA. In this study, the polyplex micelle of PEG-SS-P[Asp(DET)], which disulfide linkage (SS) between PEG and cationic polymer can detach the surrounding PEG chains upon intracellular reduction, was firstly evaluated with respect to in vivo transduction efficiency and toxicity in comparison to that of PEG-P[Asp(DET)] in peritoneally disseminated cancer model. Intraperitoneal (i.p.) administration of PEG-SS-P[Asp(DET)] polyplex micelles showed a higher (P<0.05) transgene expression compared with PEG-P[Asp(DET)] in tumors. In contrast, the delivered distribution of the micelles was not different between the two polyplex micelles. PEG-SS-P[Asp(DET)] micelle encapsulating human tumor necrosis factor α (hTNF-α) gene exhibits a higher antitumor efficacy against disseminated cancer compared with PEG-P[Asp(DET)] or saline control. No hepatic and renal toxicities were observed by the administration of polyplex micelles. In conclusion, PEG-detachable polyplex micelles may represent an advantage in gene transduction in vivo over PEG-undetachable polyplex micelles after i.p. administration for peritoneal dissemination of cancer.

Impaired activities of cyclic adenosine monophosphate-responsive element binding protein, protein kinase A and calcium-independent phospholipase A2 are involved in deteriorated regeneration of cirrhotic liver after partial hepatectomy in rats.

AIMS: This study is to elucidate whether cyclic adenosine monophosphate (cAMP)-mediated signal is involved in lower regenerative potential of cirrhotic liver. METHODS: Hepatic cAMP concentration, activities of protein kinase A (PKA), c-AMP responsive element binding protein (CREB) and Ca(2+) -independent phospholipase A(2) (iPLA2) and regeneration rate were compared between rats with thioacetamide-induced cirrhotic and normal livers after two-third hepatectomy. RESULTS: The liver regeneration estimated by the rates of [(3) H]-thymidine incorporation and staining of proliferating cell nuclear antigen was significantly lower in the cirrhotic group. CREB, PKA and iPLA2 activities, assessed by western blots and electromobility shift assay, were significantly impaired after hepatectomy in the cirrhosis group. PKA and iPLA2 silencing by siRNA transfection significantly inhibited CREB activity and cell growth in transformed hepatocytes in vitro. CONCLUSIONS: CREB dysfunction, mediated by PKA and iPLA2 suppression, may be involved in the deteriorated liver regeneration in the cirrhotic rats.

Chemotherapy with hybrid liposomes for human breast tumors along with apoptosis in vivo.

Hybrid liposomes (HL-n) can be prepared by dissolving both vesicular and micellar molecules in buffer solution with ultrasonication. A clear solution of HL-n composed of 95 mol% dimyristoylphosphatidylcholine (DMPC) and 5 mol% polyoxyethylenedodecyl ether (C(12)(EO)(n), n=21 and 25) having hydrodynamic diameter of 100 nm could be kept over 1 month on the basis of dynamic light scattering measurements was obtained. (1) Increases of fusion and accumulation of HL-n including NBDPC as a fluorescence probe into human breast tumor (MDA-MB-453) cell membranes were observed. (2) Reduction of mitochondrial membrane potential and activation of caspase-8, caspase-9, and caspase-3 were observed, indicating that apoptotic signal by HL-n should pass through mitochondria and these caspases. (3) Remarkable reduction of tumor volume in a xenograft mice model intravenously treated with HL-n without drugs after the subcutaneously inoculation of MDA-MB-453 cells was verified in vivo. Induction of apoptosis in tumor of xenograft mice treated with HL-n was observed in micrographs on the basis of TUNEL method. It was noteworthy that the therapeutic effects of HL-n along with apoptosis were obtained for xenograft mice model of human breast tumor in vivo.