Oral cancer is one of the most aggressive epithelial malignancies, whose incidence is on the rise. Previous studies have shown that in a subset of human oral squamous cell carcinoma (OSCC) tumor specimens, overexpression of the DPAGT1 gene, encoding the dolichol-P-dependent N-acetylglucoseamine-1-phosphate transferase, a key regulator of the metabolic pathway of protein N-glycosylation, drives tumor cell discohesion by inhibiting E-cadherin adhesive function. Recently, we reported that DPAGT1 was a target of the canonical Wnt signaling pathway. Here, we link overexpression of DPAGT1 in human OSCC tumor specimens to aberrant activation of canonical Wnt signaling. We report dramatic increases in β- and γ-catenins at the DPAGT1 promoter and correlate them with reduced expression of a Wnt inhibitor, Dickkopf-1 (Dkk-1). Using human squamous carcinoma cell lines of the head and neck, we show that partial inhibition of DPAGT1 reduces canonical Wnt signaling, indicating that DPAGT1 and canonical Wnt signaling function in a positive feedback loop. We provide evidence that E-cadherin inhibits DPAGT1, canonical Wnt signaling and the OSCC cancer phenotype by depleting nuclear β-and γ-catenins, with hypoglycosylated E-cadherin being the most effective.This suggests that in human OSCC, extensive N-glycosylation of E-cadherin compromises its ability to inhibit canonical Wnt signaling and DPAGT1 expression. Our studies reveal a novel interplay between DPAGT1/N-glycosylation and canonical Wnt signaling and suggest that dysregulation of this crosstalk is a key mechanism underlying OSCC. They also suggest that partial inhibition of DPAGT1 may represent an effective way to restore normal interactions among these essential pathways in oral cancer.

BackgroundHead and neck squamous cell carcinoma (HNSCC) is the sixth most common malignant tumor in the world. Studies in recent years have demonstrated that cancer stem cells (CSCs) are present in many tumor tissues, including HNSCC, and CSCs are the root cause of tumor recurrence and metastasis. Thus, taking new treatment measures to target the killing of CSCs that are resistant to chemotherapy and radiotherapy is key to the success of cancer treatment.MethodsWe explored a method for preparing anti-CD44 antibody-modified superparamagnetic iron oxide nanoparticles (SPIONPs). Biocompatibility was evaluated by a CCK-8 assay. The CSCs were obtained by a 3D cell culture technique from Cal-27 (human oral squamous cell carcinoma) cells, and then the CSCs were identified by quantitative real-time polymerase chain reaction (qRT-PCR). The targeting efficiency of the CD44-SPIONPs to CSCs was confirmed by Prussian blue staining and visualized by laser scanning confocal microscopy (LSCM). Flow cytometry was used to detect the apoptosis of CSCs after alternating magnetic field (AMF) treatment. The efficacy of tumor growth inhibition by CD44-SPIONP-mediated magnetic hyperthermia therapy was evaluated with tumor xenografts in nude mice.ResultsThe CD44-SPIONPs exhibited no negative effect on CSCs, indicating good biocompatibility. After SPIONPs were cocultured with stem cells, the majority of CD44-SPIONPs labeled with FITC penetrated the cell membrane into the cytoplasm. After AMF treatment, CD44-SPIONPs induced CSCs to undergo programmed death. The inhibitory ratio of the treated group was 33.43%, and necrotic areas in the tumor tissue were mainly distributed around the magnetic fluid.ConclusionThese results demonstrate that it is possible to kill CSCs using targeted magnetic nanoparticles and an AMF and that magnetic fluid hyperthermia significantly inhibited the growth of grafted Cal-27 tumors in mice.

Key words: apoptosis; vesicular stomatitis virus; gemcitabine; lung cancer; chemotherapyLung cancer accounts for about 1.5 million cases worldwide and is the leading cause of cancer-related death in both males and females. Non small cell lung cancer (NSCLC) comprises approximately 75-80% of all lung cancers. Despite aggressive approaches made in the therapy of lung cancer in the past decades, the prognosis of NSCLC remains poor, with 5-year survival rates of 5-14%, even if treated with surgery, radiotherapy and/or chemotherapy. 1-3 Efforts are therefore continuing to develop new and less toxic therapeutic approaches for the treatment of lung cancer.Vesicular stomatitis virus (VSV) is an enveloped, negativesense RNA virus and prototypic member of the family rhabdoviridae. 4 -6 It has been shown to replicate rapidly in vitro and kill selectively a variety of tumor cell lines. An essential, dose-limiting site of chemotherapy is the bone marrow while VSV can selectively kill leukemia cells when cocultured with normal bone marrow cells. 4 Furthermore, VSV exhibits the antitumor activity in both human tumor xenografts in nude mice and syngeneic tumors in the immunocompetent mice. 4,5 Gemcitabine (2Ј,2Ј-diflurodeoxycytidine) is a new deoxycytidine analogue that inhibits DNA synthesis. After cellular uptake, gemcitabine is phosphorylated to its active metabolites, which competitively inhibits DNA chain elongation, leading to DNA fragmentation and cell death. Gemcitabine has shown cytotoxic activity against a wide range of cancer cell lines in vitro and a number of murine and human tumors in vivo. [7][8][9] Gemcitabine monotherapy produced objective response in 20 -25% of patients with advanced NSCLC and has similar efficacy to cisplatin plus etoposide. 10 -12 When combined with cisplatin and/or paclitaxel or vinorelbine, gemcitabine therapy shows an objective response rates in 28 -54% and the median survival durations ranged from 38 to 61.5 weeks. [13][14][15][16][17][18] However, the treatment of advanced lung cancer still remains a challenge to medical oncologists.Because of differences in mechanisms of action and toxicity profiles, the combination of the above 2 agents may have clinical potential. The present study was designed to determine whether gemcitabine potentiates the antitumor activity of VSV in vitro using both A549 (human lung adenocarcinoma) and LLC (murine Lewis lung carcinoma) cell lines and in vivo using A549 lung cancer xenografts and the murine syngeneic Lewis lung cancer, and if so, to examine the possible mechanism in the phenomenon, as well as to provide some potential implications for the treatment of human lung cancer. MATERIAL AND METHODS Cells lines and agentsLLC cells and A549 cells were purchased from American Type Culture Collection (Rockville, MD). They were maintained in monolayer cultures in DMEM and RPMI-1640, respectively, supplemented with 10% heat-inactivated fetal bovine serum (FBS), at 37°C in a humidified atmosphere containing 5% CO 2 . Human umbilical vein endothelial cells (HU...

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