Search

Purpose:Exploitation of altered glycosylation in cancer is a major goal for the design of new cancer therapy. Here, we designed a novel secreted chimeric signal peptide–Galectin-3 conjugate (sGal-3) and investigated its ability to induce cancer-specific cell death by targeting aberrantly N-glycosylated cell surface receptors on cancer cells.Experimental Design:sGal-3 was genetically engineered from Gal-3 by extending its N-terminus with a noncleavable signal peptide from tissue plasminogen activator. sGal-3 killing ability was tested on normal and tumor cells in vitro and its antitumor activity was evaluated in subcutaneous lung cancer and orthotopic malignant glioma models. The mechanism of killing was investigated through assays detecting sGal-3 interaction with specific glycans on the surface of tumor cells and the elicited downstream proapoptotic signaling.Results:We found sGal-3 preferentially binds to β1 integrin on the surface of tumor cells due to aberrant N-glycosylation resulting from cancer-associated upregulation of several glycosyltransferases. This interaction induces potent cancer-specific death by triggering an oncoglycan-β1/calpain/caspase-9 proapoptotic signaling cascade. sGal-3 could reduce the growth of subcutaneous lung cancers and malignant gliomas in brain, leading to increased animal survival.Conclusions:We demonstrate that sGal-3 kills aberrantly glycosylated tumor cells and antagonizes tumor growth through a novel integrin β1–dependent cell-extrinsic apoptotic pathway. These findings provide proof-of-principle that aberrant N-oncoglycans represent valid cancer targets and support further translation of the chimeric sGal-3 peptide conjugate for cancer therapy.

S1-S7

Supplementary Figure 1 Legend from 16-kDa Prolactin Inhibits Endothelial Cell Migration by Down-Regulating the Ras-Tiam1-Rac1-Pak1 Signaling Pathway

Supplementary Figure 1 from 16-kDa Prolactin Inhibits Endothelial Cell Migration by Down-Regulating the Ras-Tiam1-Rac1-Pak1 Signaling Pathway

Phytogenic feed additives have become attractive alternatives for use in animal diets. The objective of the present study was to evaluate the effect of a phytogenic-based feed additive on growth performance, nutrient digestibility, blood profiles, fecal noxious gas emission, and intestinal morphology of weaning pigs after dietary challenge with E. coli K88. A total of 120 crossbred pigs [(Yorkshire × Landrace) × Duroc)] with an initial body weight (BW) of 6.09 ± 0.96 kg (21 d of age) were assigned randomly to 1 of the 4 dietary treatments. Each pen housed 5 pigs, and there were 6 pens/treatment. Treatments included: T1, negative control (without antibiotics); T2, T1 + antibiotic; T3, T1 + 0.05% phytogenics; and T4, T1 + 0.2% commercial mix of organic acids. Overall, the average daily gain (ADG) with the T3 treatment was higher (PE.coli K88.

Angiogenesis plays a key role in promoting tumorigenesis and metastasis. The 16-kDa fragment of prolactin (16k PRL) is an NH2-terminal natural breakdown fragment of the intact 23-kDa prolactin and has been shown to have potent antiangiogenic and antitumor activities. The mechanism(s) involved in the action of 16k PRL in endothelial cells remains unclear. In this study, we showed that 16k PRL reduced rat aortic endothelial cell (RAEC) migration in a wound-healing assay and in a Matrigel tube formation assay, suggesting that 16k PRL inhibits endothelial cell migration, an important activity involved in angiogenesis and tumorigenesis. We further investigated how 16k PRL attenuates endothelial cell migration. We first showed that RAEC migration is mediated through the Rho GTPase Rac1, as Rac1 inhibition by the Rac1-specific inhibitor NSC27366 or Rac1 knockdown by small interfering RNA both blocked RAEC migration. We next showed that 16k PRL reduced the activation of Rac1 in a concentration-dependent manner. Furthermore, 16k PRL inhibition of Rac1 is mediated through the suppression of T lymphoma invasion and metastasis 1 (Tiam1) and its upstream activator Ras in a phosphoinositide-3-kinase–independent manner. 16k PRL also down-regulated the phosphorylation of the downstream effector of Rac1, p21-activating kinase 1 (Pak1), and inhibited its translocation to the leading edge of migrating cells. Thus, 16k PRL inhibits cell migration by blocking the Ras-Tiam1-Rac1-Pak1 signaling pathway in endothelial cells. [Cancer Res 2007;67(22):11045–53]

Angiogenesis plays a key role in promoting tumorigenesis and metastasis. Several antiangiogenic factors have been shown to inhibit tumor growth in animal models. Understanding their mechanism of action would allow for better therapeutic application. 16-kDa prolactin (PRL), a NH2-terminal natural breakdown fragment of the intact 23-kDa PRL, exerts potent antiangiogenic and antitumor activities. The signaling mechanism involved in 16-kDa PRL action in endothelial cells remains unclear. One of the actions of 16-kDa PRL is to attenuate the production of nitric oxide (NO) through the inhibition of inducible NO synthase (iNOS) expression in endothelial cells. To delineate the signaling mechanism from 16-kDa PRL, we examined the effect of 16-kDa PRL on interleukin IL-1β–inducible iNOS expression, which is regulated by two parallel pathways, one involving IFN regulatory factor 1 (IRF-1) and the other nuclear factor-κB (NF-κB). Our studies showed that 16-kDa PRL specifically blocked IRF-1 but not NF-κB signaling to the iNOS promoter. We found that IL-1β regulated IRF-1 gene expression through stimulation of p38 mitogen-activated protein kinase (MAPK), which mediated signal transducer and activator of transcription 1 (Stat1) serine phosphorylation and Stat1 nuclear translocation to activate the IRF-1 promoter. 16-kDa PRL effectively inhibited IL-1β–inducible p38 MAPK phosphorylation, resulting in blocking Stat1 serine phosphorylation, its subsequent nuclear translocation and activation of the Stat1 target gene IRF-1. Thus, 16-kDa PRL inhibits the p38 MAPK/Stat1/IRF-1 pathway to attenuate iNOS/NO production in endothelial cells.

Galectins are a family of animal lectins, which bind beta-galactose moieties. Gal3 is the only chimeric family member of Gals and consists of a collagen-like N-terminal region and a C-terminal carbohydrate recognition domain (CRD), which has binding affinity for galactose and N-acetyl-lactosamine. Gal3 is known to be secreted through Golgi apparatus-independent alternative pathway. Previously, we found that stimuli-induced p53 activation induced bystander killing effect against adjacent cells. This p53 bystander effect is mediated through the secretion of Gal3 with the requirement of p53-dependent induction of tumor suppressor activated pathway-6 (TSAP6). We found the apoptotic activity of extracellular Gal3: a variety of tumor cell types (malignant glioma, breast, colon, prostate, lung) are sensitive to Gal3-mediated killing, while normal cells (fibroblast, endothelial) are not affected. We demonstrated that conditional sGal3 induction (tet-on system) in glioma xenografts strongly inhibits tumor growth without overt toxicity in mice. We found that Gal3-mediated tumor cell killing was neutralized with lactose, a Gal3-CRD binding ligand, and Gal3-mediated apoptosis was inhibited by treatment with a caspase 9 inhibitor (LEHD) but not by a caspase 8 inhibitor (IETD). Gal3 interacts with several glycosylated cell surface proteins. We identified that Gal3-induced tumor specific apoptosis is mediated through Gal3-beta1 integrin binding through GST-Gal3 pulldown assay, cell membrane-specific Gal3-beta1 integrin co-immunoprecipitation, and beta1 integrin siRNA neutralization. Further, the treatment of N-glycosylation inhibitor (tunicamycin) interfered with Gal3-beta1 integrin interaction whereas, O-glycosylation inhibitor (benzyl-O-N-acetyl-D-galactosamine) increased N-glycosylation of beta1 integrin as well as consequent Gal3-beta1 integrin interaction and Gal3-mediated apoptosis. In summary, our data demonstrate that extracellular Gal3 interacts with tumor cells through highly-glycosylated cell surface beta1 integrin through its CRD binding and consequently induces apoptosis. These findings are important for our understanding of tumor-specific killing of Gal3 and suggest that Gal3 can be exploited as a therapeutic agent for cancer. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1264.