PEG-coated irinotecan cationic liposomes improve the therapeutic efficacy of breast cancer in animals

BACKGROUND

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among females owing.

AIM

This study aimed to construct a kind of PEG-coated irinotecan cationic liposomes for investigating its efficacy and mechanism of action in the treatment of breast cancer in preclinical models.

MATERIALS AND METHODS

Evaluations were performed on the MDA-MB231 breast cancer cells, the xenografted MDA-MB231 cancer cells in Female nude mice and Sprague-Dawley (SD) rat. The liposomes were characterized through assays of cytotoxicity, intracellular uptake, nuclei morphology, antitumor activities, pharmacokinetics and tissue distribution.

RESULTS

The zeta potential of PEG-coated irinotecan cationic liposomes was approximately 23 mV. The PEG-coated irinotecan cationic liposomes were approximately 66nm in diameter, significantly increased the intracellular uptake of irinotecan, and showed strong inhibitory effect on MDA-MB231 breast cancer cells. A significant antitumor efficacy in the xenografted MDA-MB231 breast cancer cells in nude mice was evidenced by intravenous administration of PEG-coated irinotecan cationic liposomes. PEG-coated irinotecan cationic liposomes also improved the irinotecan blood circulation time and showed an enhanced drug concentration in tumor.

CONCLUSIONS

PEG-coated irinotecan cationic liposomes had significant inhibitory effect against breast cancer in vitro and in vivo, hence providing a new strategy for treating breast cancer.

The entomopathogenic bacterial endosymbionts Xenorhabdus and Photorhabdus: convergent lifestyles from divergent genomes

Members of the genus Xenorhabdus are entomopathogenic bacteria that associate with nematodes. The nematode-bacteria pair infects and kills insects, with both partners contributing to insect pathogenesis and the bacteria providing nutrition to the nematode from available insect-derived nutrients. The nematode provides the bacteria with protection from predators, access to nutrients, and a mechanism of dispersal. Members of the bacterial genus Photorhabdus also associate with nematodes to kill insects, and both genera of bacteria provide similar services to their different nematode hosts through unique physiological and metabolic mechanisms. We posited that these differences would be reflected in their respective genomes. To test this, we sequenced to completion the genomes of Xenorhabdus nematophila ATCC 19061 and Xenorhabdus bovienii SS-2004. As expected, both Xenorhabdus genomes encode many anti-insecticidal compounds, commensurate with their entomopathogenic lifestyle. Despite the similarities in lifestyle between Xenorhabdus and Photorhabdus bacteria, a comparative analysis of the Xenorhabdus, Photorhabdus luminescens, and P. asymbiotica genomes suggests genomic divergence. These findings indicate that evolutionary changes shaped by symbiotic interactions can follow different routes to achieve similar end points.

Hearts from DCD donors display acceptable biventricular function after heart transplantation in pigs

Cardiac transplantation is in decline, in contrast to other solid organs where the number of solid organ transplants from donors after circulatory death (DCD) is increasing. Hearts from DCD donors are not currently utilized due to concerns that they may suffer irreversible cardiac injury with resultant poor graft function. Using a large animal model, we tested the hypothesis that hearts from DCD donors would be suitable for transplantation. Donor pigs were subjected to hypoxic cardiac arrest (DCD) followed by 15 min of warm ischemia and resuscitation on cardiopulmonary bypass, or brainstem death (BSD) via intracerebral balloon inflation. Cardiac function was assessed through load-independent measures and magnetic resonance imaging and spectroscopy. After resuscitation, DCD hearts had near normal contractility, although stroke volume was reduced, comparable to BSD hearts. DCD hearts had a significant decline in phosphocreatine and increase in inorganic phosphate during the hypoxic period, with a return to baseline levels after reperfusion. After transplantation, cardiac function was comparable between BSD and DCD groups. Therefore, in a large animal model, the DCD heart maintains viability and recovers function similar to that of the BSD heart and may be suitable for clinical transplantation. Further study is warranted on optimal reperfusion strategies.

Large field-induced strains in a lead-free piezoelectric material

Piezoelectric materials exhibit a mechanical response to electrical inputs, as well as an electrical response to mechanical inputs, which makes them useful in sensors and actuators. Lead-based piezoelectrics demonstrate a large mechanical response, but they also pose a health risk. The ferroelectric BiFeO(3) is an attractive alternative because it is lead-free, and because strain can stabilize BiFeO(3) phases with a structure that resembles a morphotropic phase boundary. Here we report a reversible electric-field-induced strain of over 5% in BiFeO(3) films, together with a characterization of the origins of this effect. In situ transmission electron microscopy coupled with nanoscale electrical and mechanical probing shows that large strains result from moving the boundaries between tetragonal- and rhombohedral-like phases, which changes the phase stability of the mixture. These results demonstrate the potential of BiFeO(3) as a substitute for lead-based materials in future piezoelectric applications.

In-gel protein N- and C-termini identification and its application for transgenic protein characterization

A new method for the determination of N- and C-termini of a protein isolated in a polyacrylamide gel is introduced. In-gel partial protein hydrolysis by hydrochloric acid is used to generate N- and C-terminal peptides for identification. This new method is complementary to existing techniques. The application of the in-gel protein termini identification technique to the characterization of the transgenic protein diacylglycerol acyltransferase (UrDGAT2A) purified from soybean seeds is also reported here. Both N- and C-termini of UrDGAT2A were successfully identified and the N-terminus was found to be blocked by acetylation. The analysis results of UrDGAT2A and two commercial proteins (bovine serum albumin (BSA) and alcohol dehydrogenase) are used to demonstrate the effectiveness of the method in identifying actual N- and C-termini, terminal truncation and blocking.

An accurate and clean calibration method for MALDI-MS

A new method for the mass calibration of the matrix-assisted laser desorption/ionization-mass spectrometry spectrum is introduced. This method achieves the same accuracy as that of internal calibration but without its drawbacks. The interference and signal suppression by calibration standard are avoided, and a pure/clean sample spectrum is obtained. No prior knowledge about the sample quantity is required for the calibration. The effectiveness of the method is demonstrated with protein identification data.

Activation of transient receptor potential vanilloid subtype 1 increases secretion of the hypofunctional, transplanted submandibular gland

Hyposecretion occurs in most patients early after submandibular gland autotransplantation for severe keratoconjunctivitis sicca. Endogenous transient receptor potential vanilloid subtype 1 (TRPV1) has been recently demonstrated in rabbit submandibular glands, and activation of TRPV1 by capsaicin increases secretion in isolated glands, but the TRPV1-mediated secretory mechanism remains to be elucidated. The purpose of this study was to verify whether activation of TRPV1 by capsaicin could improve the secretion of transplanted gland and its underlying mechanism. The salivary flow of the transplanted glands was significantly decreased, and the mRNA and protein levels of TRPV1 and aquaporin 5 (AQP5) were downregulated in the transplanted glands. Topical capsaicin cream increased secretion and upregulated levels of TRPV1 and AQP5 in transplanted glands. Moreover, in cultured submandibular gland cells, capsaicin increased the mRNA expression of AQP5 and led to redistribution of AQP5 from the cytoplasm to the plasma membrane via TRPV1 activation. Capsaicin enhanced the phosphorylation of extracellular signal-regulated kinase (ERK). Preincubation of cells with PD98059, an inhibitor of ERK kinase, suppressed the capsaicin-induced mRNA expression of AQP5. In summary, the capsaicin-induced secretory mechanism involved activation of TRPV1 and upregulation of AQP5 in an ERK-dependent manner and promoted the redistribution of AQP5 in submandibular gland cells. Activation of TRPV1 may provide a new therapeutic strategy to improve submandibular gland hypofunction.

Isoproterenol improves secretion of transplanted submandibular glands

Autotransplantation of the submandibular gland is effective for severe keratoconjunctivitis sicca. However, most transplants show decreased secretion shortly after the operation, which leads to obstruction of Wharton's duct. The hypothesis that decreased catecholamine release due to denervation contributes to hypofunction in the early phase was tested in transplanted glands in rabbits. We found that salivary flow, expression of beta(1)- and beta(2)-adrenoceptor, and the maximum binding capacity were markedly decreased in the transplanted glands. Isoproterenol significantly reversed the decreased secretion, enhanced the expressions of beta(1)- and beta(2)-adrenoceptor, and ameliorated the atrophy of acinar cells. The contents of cAMP and phospho-ERK 1/2 were increased after isoproterenol treatment. These results indicate that lack of beta-adrenoceptor stimulation is involved in early dysfunction of the transplanted gland. Isoproterenol treatment moderates structural injury and improves secretory function in the transplanted submandibular gland through up-regulating beta(1)- and beta(2)-adrenoceptor expression and post-receptor signal transduction.

Transforming growth factor beta engages TACE/ADAM17 and ErbB3 to activate PI3K/Akt in HER2-overexpressing breast cancer and desensitizes cells to trastuzumab

Abstract #35

TGFb signaling synergizes with HER2 in breast cancer progression. Exogenous TGFb or expression of an activated TGFb type I receptor (Alk5T204D) in MCF10A/HER2 and BT474 cells activated PI3K/Akt and enhanced survival and migration. In both cell types, TGFb stimulated P-EGFR and P-HER2 as well as the association of p85, the regulatory subunit of PI3K, with Y1289 P-ErbB3 which, in turn, activated PI3K/Akt. RNA interference of ErbB3 or treatment with pertuzumab, an antibody that blocks HER2-mediated activation of ErbB3, blocked TGFb-induced P-ErbB3, P-Akt, and cell motility. Treatment with TGFb or expression of Alk5TD increased protein levels of secreted TGFalpha, amphiregulin, and heregulin without a change in mRNA levels. The increase on secreted ErbB ligands without a change in mRNA levels suggested increased shedding of ErbB pro-ligands by tumor necrosis factor a-converting enzyme (TACE). Transfection of siRNA against human TACE but not control siRNA abrogated TGFb-stimulated ErbB receptor phosphorylation, P-Akt, and cell invasiveness. Transfection of full-length mouse TACE but not truncated TACE lacking the cytoplasmic domain reconstituted TGFb-induced ErbB phosphorylation in cells transfected with human TACE siRNA. TGF-b increased TACE phosphorylation in both serine and threonine as measured by P-Ser and P-Thr immunoblots of TACE pull downs. Incubation of TACE with Alk5TD in the presence of ATP in vitro resulted in both Ser and Thr phosphorylation in full-length but not truncated TACE. Further, addition of TGFb or expression of Alk5TD desensitized SKBR3 and BT474 cells to trastuzumab. Treatment with the type I TGFb receptor (Alk5) small molecule inhibitor LY2109761, the PI3K inhibitor LY294002, or siRNA against ErbB3 or TACE restored the inhibitory effect of trastuzumab. Finally, we generated an active Alk5 expression signature by selecting genes that were differentially expressed between BT474/Alk5TD and BT474/vector cells. Mapping of this signature to a previously published 295-breast tumor array (van de Vijver et al. and Chang et al.) revealed 90 of 271 genes in the Alk5TD signature with a >1.5-fold change from the median expression which correlated with HER2-positive and basal-like tumors and conferred a worse recurrence-free (RFS) and overall survival (OS) (RFS p=0.05, OS p=0.01). Hierarchical clustering analysis to an array data set reported by Harris et al. in 22 patients with HER2+ breast cancer treated with neoadjuvant trastuzumab and vinorelbine (Clin. Cancer Res. 2007) showed that the Alk5TD signature correlated with tumors that did not respond clinically. These data suggest that TGFb potentiates signaling downstream ErbB receptors via TACE, ErbB3, and PI3K, thus contributing to tumor progression and resistance to anti-HER2 therapies.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 35.