Efficient Drug Delivery of Paclitaxel Glycoside: A Novel Solubility Gradient Encapsulation into Liposomes Coupled with Immunoliposomes Preparation

Although the encapsulation of paclitaxel into liposomes has been extensively studied, its significant hydrophobic and uncharged character has generated substantial difficulties concerning its efficient encapsulation into the inner water core of liposomes. We found that a more hydrophilic paclitaxel molecule, 7-glucosyloxyacetylpaclitaxel, retained tubulin polymerization stabilization activity. The hydrophilic nature of 7-glucosyloxyacetylpaclitaxel allowed its efficient encapsulation into the inner water core of liposomes, which was successfully accomplished using a remote loading method with a solubility gradient between 40% ethylene glycol and Cremophor EL/ethanol in PBS. Trastuzumab was then conjugated onto the surface of liposomes as immunoliposomes to selectively target human epidermal growth factor receptor-2 (HER2)-overexpressing cancer cells. In vitro cytotoxicity assays revealed that the immunoliposomes enhanced the toxicity of 7-glucosyloxyacetylpaclitaxel in HER2-overexpressing cancer cells and showed more rapid suppression of cell growth. The immunoliposomes strongly inhibited the tumor growth of HT-29 cells xenografted in nude mice. Notably, mice survived when treated with the immunoliposomes formulation, even when administered at a lethal dose of 7-glucosyloxyacetylpaclitaxel in vivo. This data successfully demonstrates immunoliposomes as a promising candidate for the efficient delivery of paclitaxel glycoside

Targeting Ovarian Cancer Cells Overexpressing CD44 with Immunoliposomes Encapsulating Glycosylated Paclitaxel

Paclitaxel (PTX) is one of the front-line drugs approved for the treatment of ovarian cancer. However, the application of PTX is limited due to the significant hydrophobicity and poor pharmacokinetics. We previously reported target-directed liposomes carrying tumor-selective conjugated antibody and encapsulated glycosylated PTX (gPTX-L) which successfully overcome the PTX limitation. The tubulin stabilizing activity of gPTX was equivalent to that of PTX while the cytotoxic activity of gPTX was reduced. In human ovarian cancer cell lines, SK-OV-3 and OVK18, the concentration at which cell growth was inhibited by 50% (IC50) for gPTX range from 15⁻20 nM, which was sensitive enough to address gPTX-L with tumor-selective antibody coupling for ovarian cancer therapy. The cell membrane receptor CD44 is associated with cancer progression and has been recognized as a cancer stem cell marker including ovarian cancer, becoming a suitable candidate to be targeted by gPTX-L therapy. In this study, gPTX-loading liposomes conjugated with anti-CD44 antibody (gPTX-IL) were assessed for the efficacy of targeting CD44-positive ovarian cancer cells. We successfully encapsulated gPTX into liposomes with the loading efficiency (LE) more than 80% in both of gPTX-L and gPTX-IL with a diameter of approximately 100 nm with efficacy of enhanced cytotoxicity in vitro and of convenient treatment in vivo. As the result, gPTX-IL efficiently suppressed tumor growth in vivo. Therefore gPTX-IL could be a promising formulation for effective ovarian cancer therapies

Cytokine Expression and Macrophage Localization in Xenograft and Allograft Tumor Models Stimulated with Lipopolysaccharide

T cell-deficient mice such as nude mice are often used to generate tumor xenograft for the development of anticancer agents. However, the functionality of the other immune cells including macrophages, dendritic cells (DCs), and myeloid-derived suppressor cells (MDSCs) in the xenograft are largely unknown. Macrophages and dendritic cells (DCs) acquire functionally distinct properties in response to various environmental stimuli; the interaction of these cells with MDSCs in tumor microenvironments regulates cancer progression. Nude mice are less likely to reject human cancer cells because of major histocompatibility complex (MHC) mismatches. The tumor microenvironment in a xenograft, comprising human and mouse cells, exhibits more complex bidirectional signaling and function than that of allograft. Here, we evaluated the differences of myeloid cells between them. Plasma interferon-γ and interleukin-18 concentrations in the xenograft tumor model after lipopolysaccharide (LPS) administration were significantly higher than those in the allograft tumor model. MHC class I, II, and CD80 expression levels were increased in CD11b+ and MDSC populations after LPS administration in the spleen of a xenograft tumor model but not in that of an allograft tumor model. Additionally, the number of CD80- and mannose receptor C type 1 (MRC1)-expressing cells was decreased upon LPS administration in the tumor of the xenograft tumor. These results suggest that functions of macrophages and DCs are sustained in the xenograft, whereas their functions in response to LPS were suppressed in the allograft. The findings will encourage the consideration of the effects of myeloid cells in the xenograft for drug development

Chlorotoxin-Fc Fusion Inhibits Release of MMP-2 from Pancreatic Cancer Cells

Chlorotoxin (CTX) is a 36-amino acid peptide derived from Leiurus quinquestriatus (scorpion) venom, which inhibits low-conductance chloride channels in colonic epithelial cells. It has been reported that CTX also binds to matrix metalloproteinase-2 (MMP-2), membrane type-1 MMP, and tissue inhibitor of metalloproteinase-2, as well as CLC-3 chloride ion channels and other proteins. Pancreatic cancer cells require the activation of MMP-2 during invasion and migration. In this study, the fusion protein was generated by joining the CTX peptide to the amino terminus of the human IgG-Fc domain without a hinge domain, the monomeric form of chlorotoxin (M-CTX-Fc). The resulting fusion protein was then used to target pancreatic cancer cells (PANC-1) in vitro. M-CTX-Fc decreased MMP-2 release into the media of PANC-1 cells in a dose-dependent manner. M-CTX-Fc internalization into PANC-1 cells was observed. When the cells were treated with chlorpromazine (CPZ), the internalization of the fusion protein was reduced, implicating a clathrin-dependent internalization mechanism of M-CTX-Fc in PANC-1 cells. Furthermore, M-CTX-Fc clearly exhibited the inhibition of the migration depending on the concentration, but human IgG, as negative control of Fc, was not affected. The M-CTX-Fc may be an effective instrument for targeting pancreatic cancer

Solubility of PTX and gPTX in different solvents.

<p>* <i>Solubility of H₂O was referred as described previously</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107976#pone.0107976-Mandai1" target="_blank">[19]</a>.</p><p>** <i>CEP consists of Cremophor EL and ethanol in PBS (12∶12∶76 volume %)</i>.</p><p>Solubility of PTX and gPTX in different solvents.</p

Anticancer efficacy of different gPTX formulations with repeated administration in HT-29 cells tumor-bearing mice.

<p>gPTX-IL (open circle with line), gPTX-L (open triangle), gPTX-L with trastuzumab (open square), trastuzumab (closed square), CEP-IL (closed circle), CEP-L (closed triangle), or PBS (cross) was intravenously injected at day 0, 10, and 20. The dose of each administration was 150 mg/kg gPTX. A and B, Changes in tumor volume. C, Changes in body weight. D, Survival curves. Data are presented as the mean ± S.D. The changes of tumor volume and body weight in the mice administered with gPTX-L do not show S.D. after day 10. The <i>P</i> value shown compared with gPTX-IL and gPTX-L with trastuzumab treated group at day 43 (n = 4). *, <i>P</i><0.05.</p

Influence of the lipid composition and incubation time for drug encapsulation by the solubility gradient method.

<p>A, The encapsulation efficiency (EE) of gPTX-L with various lipid compositions was evaluated after 30 min of incubation for gPTX encapsulation. B, The drug retention of gPTX-L with different lipid compositions was evaluated in medium supplied with 10% FBS at 37°C. C, The efficiency of drug encapsulation under different durations of incubation was evaluated with a DPPC to Chol ratio of 3∶1.</p

Cytotoxicity of different gPTX formulations by the MTT assay.

<p>A, The IC₅₀ values after drug exposure for 72 h are shown. B, The IT₅₀ values at IC₁₀₀ are shown. The data are presented as the mean ± S.D. for three independent experiments. *, <i>P</i><0.05. **, <i>P</i><0.01. ***, <i>P</i><0.005. ****, <i>P</i><0.001. NSD, no significant difference.</p