Desmoglein 3 (Dsg3), the pemphigus vulgaris antigen, has recently been shown to be upregulated in squamous cell carcinoma (SCC) and has been identified as a good tumor-specific marker for clinical staging of cervical sentinel lymph nodes in head and neck SCC. However, little is known about its biological function in cancer. The actin-binding protein Ezrin and the activator protein 1 (AP-1) transcription factor are implicated in cancer progression and metastasis. Here, we report that Dsg3 regulates the activity of c-Jun/AP-1 as well as protein kinase C (PKC)-mediated phosphorylation of Ezrin-Thr567, which contributes to the accelerated motility of cancer cells. Ectopic expression of Dsg3 in cancer cell lines caused enhanced phosphorylation at Ezrin-Thr567 with concomitant augmented membrane protrusions, cell spreading and invasive phenotype. We showed that Dsg3 formed a complex with Ezrin at the plasma membrane that was required for its proper function of interacting with F-actin and CD44 as Dsg3 knockdown impaired these associations. The increased Ezrin phosphorylation in Dsg3-overexpressing cells could be abrogated substantially by various pharmacological inhibitors for Ser/Thr kinases, including PKC and Rho kinase that are known to activate Ezrin. Furthermore, a marked increase in c-Jun S63 phosphorylation, among others, was found in Dsg3-overexpressing cells and the activation of c-Jun/AP-1 was further supported by a luciferase reporter assay. Taken together, our study identifies a novel Dsg3-mediated c-Jun/AP-1 regulatory mechanism and PKC-dependent Ezrin phosphorylation that could be responsible for Dsg3-associated cancer metastasis.

Abstract. Background: Carboplatin and paclitaxel

Widescale evaluation of interacting partners for carbohydrates is an underexploited area. Probing of the ‘glyco-interactome’ has particular relevance given the lack of direct genetic control of glycoconjugate biosynthesis. Here we design, create and utilize a natural product-derived glycomimetic iminosugar probe in a Glycomimetic Affinity-enrichment Proteomics (glyco-AeP) strategy to elucidate key interactions directly from mammalian tissue. The binding partners discovered here and the associated genomic analysis implicate a subset of chaperone and junctional proteins as important in male fertility. Such repurposing of existing therapeutics thus creates direct routes to probing in vivo function. The success of this strategy suggests a general approach to discovering ‘carbohydrate-active’ partners in biology.

No abstract

Ovarian cancer ranks first in the number of deaths and second in the number of new cases among gynecological cancers. In the majority of the cases, surgery is the intervention of choice, but chemotherapy has progressed considerably over the last years. First-line treatment for advanced-stage disease is a combination of carboplatin and paclitaxel. However, drug resistance has become a major obstacle to the successful chemotherapeutic treatment of human cancers. Currently, there is no clear consensus on treatment options for ovarian cancer patients who acquired drug resistance, due to the lack of knowledge about drug resistance mechanisms. There is an urgent need to explain how drug resistance occurs and to identify proteins related to this phenomenon, so that inhibitors can be designed. The aims of this study are to develop and optimise a two-dimensional gel electrophoresis method to compare protein profile of human ovarian cancer cell lines, which are sensitive or resistant to anticancer chemotherapy, so that proteins related to drug resistance can be identified using mass spectrometry. The parental ovarian cancer cell line models PEO1 and SKOV-3 are used as drug sensitive reference cell lines. Novel drug resistant models, derived from the parental lines, with in vitro acquired resistance to paclitaxel and carboplatin are used alongside their respective drug sensitive parental counterparts. Proteins related to tumorigenesis or drug resistance, either new or previously reported, were identified in at least one of the three cell lines. These proteins belong to different classes and are responsible for distinct functions within the cell, such as cytoskeleton and cell structure, detoxification and stress response, and cellular metabolism. This is the first proteomic study on these specific ovarian cancer cell lines using paclitaxel and carboplatin. The results obtained will be useful for further studies of resistance mechanisms and screening of resistance biomarkers for the development of tailored therapeutic strategies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4799. doi:1538-7445.AM2012-4799