Cationic liposomes (CLs) have been regarded as the most promising gene delivery vectors for decades with the advantages of excellent biodegradability, biocompatibility, and high nucleic acid encapsulation efficiency. However, the clinical use of CLs in cancer gene therapy is limited because of many uncertain factors in vivo . Extracellular barriers such as opsonization, rapid clearance by the reticuloendothelial system and poor tumor penetration, and intracellular barriers, including endosomal/lysosomal entrapped network and restricted diffusion to the nucleus, make CLs not the ideal vector for transferring extrinsic genes in the body. However, the obstacles in achieving productive therapeutic effects of nucleic acids can be addressed by tailoring the properties of CLs, which are influenced by lipid compositions and surface modification. This review focuses on the physiological barriers of CLs against cancer gene therapy and the effects of lipid compositions on governing transfection efficiency, and it briefly discusses the impacts of particle size, membrane charge density, and surface modification on the fate of CLs in vivo , which may provide guidance for their preclinical studies.

SUMMARY:Matrix metalloproteinases (MMPs) have been implicated in the formation of microvessels during angiogenesis, but their role in vascular regression is poorly understood. The rat aorta model of angiogenesis was used to study the function of MMPs at different stages of the angiogenic process. Gelatin zymography and Western analysis demonstrated production of MMP-2 and MMP-9 by aortic outgrowths in serum-free collagen gel culture. MMP-2 was found in both culture medium and collagen gel, whereas MMP-9 was predominantly associated with the gel. MMP expression increased gradually during the angiogenic growth phase and stayed high when vessels regressed and collagen lysed around the aortic rings. The MMP inhibitors, batimastat and marimastat, blocked formation of microvessels when added to the culture medium at the beginning of the experiment. They, however, stabilized the microvessels and prevented vascular regression after the angiogenic growth phase. This effect was observed also under conditions of angiogenic stimulation by basic fibroblast growth factor. MMP inhibitormediated stabilization of microvessels was associated with inhibition of collagen lysis and accumulation of collagen fibrils in the subendothelial space. This study demonstrates that MMPs promote microvessel formation during the early stages of angiogenesis, but also contribute to the reabsorption of the neovasculature in the later stages of this process. The time-dependent divergent effects of MMPs on microvessel growth and survival may influence the in vivo activity of MMP inhibitors used to treat angiogenesis-dependent disorders. (Lab Invest 2000, 80:545-555).

Recent studies have implicated the Tie2 tyrosine-kinase receptor and its main ligands - angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) - as crucial regulators of mural cell recruitment during angiogenesis. Angiopoietin-mediated activation of Tie2 promotes perivascular mural cell assembly, but the mechanisms regulating this process are poorly understood because differentiated mural cells do not have the Tie2 receptor, which is reportedly expressed only in endothelial cells. There is also no direct evidence that Tie2 activation results in production of mural cell chemoattractants by the endothelium. In the rat aorta model of angiogenesis,developing microvessels recruit mural cells from the intimal/subintimal layers of the aortic wall. Ang-1 and Ang-2 promote angiogenesis in this system,stimulating branching morphogenesis and mural cell assembly. Mural precursor cells (MPCs) isolated with a nonenzymatic method from the intimal aspect of the rat aorta were positive for smooth muscle cell markers (α-smooth muscle actin and calponin) and negative for endothelial markers(factor-VIII-related antigen and CD31). These cells responded chemotactically to Ang-1 and Ang-2, and secreted MMP-2 when treated with these factors. Western-blot analysis, immunocytochemistry and RT-PCR demonstrated that MPCs express the Tie2 receptor. Immunoprecipitation showed phosphorylation of MPC Tie2 on tyrosine residues upon stimulation with Ang-1 or Ang-2. Surface expression of Tie2 was further demonstrated by isolating Tie2+/α-smooth muscle actin+ MPCs from primary aortic outgrowths with anti-Tie2-IgG-coated magnetic beads. Immunostaining of the rat aorta confirmed expression of Tie2 not only in endothelial cells but also in nonendothelial mesenchymal cells located in the aortic intimal/subintimal layers, which are the source of MPCs. These data indicate that the aortic wall contains Tie2+ nonendothelial mesenchymal cells and suggest that Tie2-related recruitment of mural cells during angiogenesis may occur through angiopoietin-mediated direct stimulation of these cells.

Pelvic lymph node metastasis (PLNM) is an independent prognostic parameter and determines the treatment strategies of cervical cancer. Increasing evidence indicates that long non-coding RNAs (lncRNAs) play a crucial role in the process of tumor biological functions. This study aimed to mine lymph node metastasis-associated lncRNAs and investigate their potential pathophysiological mechanism in cervical cancer lymph node metastasis. We applied the lncRNA-mining approach to identify lncRNA transcripts represented on Affymetrix human genome U133 plus 2.0 microarrays from Gene Expression Omnibus (GEO) and then by validation in clinical specimens. The biological role and molecular mechanism of these lncRNAs were predicted by bioinformatic analysis. Subsequently, a receiver operating characteristic (ROC) curve and survival curve were conducted to evaluate the diagnostic and prognostic value of candidate lncRNAs. In total, 234 differentially expressed lncRNAs were identified to significantly associate with pelvic lymph node metastasis in early-stage cervical cancer. Our qRT-PCR results were consistent with the mining analysis (P<0.05). The functional enrichment analysis suggested that these lncRNAs may be involved in the biological process of lymph node metastasis. The ROC curves demonstrated satisfactory discrimination power of MIR100HG and AC024560.2 with areas under the curve of 0.801 and 0.837, respectively. Survival curve also indicated that patients with high MIR100HG expression had a tendency of poor prognosis. This is the first study to successfully mine the lncRNA expression patterns in PLNM of early-stage cervical cancer. MIR100HG and AC024560.2 may be a potential biomarkers of PLNM and these lncRNAs may provide broader perspective for combating cervical cancer metastasis.