Expression of L-PHA-binding proteins in breast cancer: reconstitution and molecular characterization of beta 1-6 branched oligosaccharides in three-dimensional cell culture

Membrane protein regulators of melanoma pulmonary colonisation identified using a CRISPRa screen and spontaneous metastasis assay in mice

Metastasis is the spread of cancer cells to a secondary site within the body, and is the leading cause of death for cancer patients. The lung is a common site of metastasis for many cancer types, including melanoma. Identifying the genes involved in aiding metastasis of melanoma cells to the lungs is critical for the development of better treatments. As the accessibility of cell surface proteins makes them attractive therapeutic targets, we performed a CRISPR activation screen using a library of guide RNAs (gRNAs) targeting the transcription start sites of 2195 membrane protein-encoding genes, to identify genes whose upregulated expression aided pulmonary metastasis. Immunodeficient mice were subcutaneously injected in the flank with murine B16-F0 melanoma cells expressing dCas9 and the membrane protein library gRNAs, and their lungs collected after 14–21 days. Analysis was performed to identify the gRNAs that were enriched in the lungs relative to those present in the cells at the time of administration (day 0). We identified six genes whose increased expression promotes lung metastasis. These genes included several with well-characterized pro-metastatic roles (Fut7, Mgat5, and Pcdh7) that have not previously been linked to melanoma progression, genes linked to tumor progression but that have not previously been described as involved in metastasis (Olfr322 and Olfr441), as well as novel genes (Tmem116). Thus, we have identified genes that, when upregulated in melanoma cells, can aid successful metastasis and colonization of the lung, and therefore may represent novel therapeutic targets to inhibit pulmonary metastasis.

The cancer glycome: carbohydrates as mediators of metastasis

Glycosylation is a frequent post-translational modification which results in the addition of carbohydrate determinants, "glycans", to cell surface proteins and lipids. These glycan structures form the "glycome" and play an integral role in cell-cell and cell-matrix interactions through modulation of adhesion and cell trafficking. Glycosylation is increasingly recognized as a modulator of the malignant phenotype of cancer cells, where the interaction between cells and the tumor micro-environment is altered to facilitate processes such as drug resistance and metastasis. Changes in glycosylation of cell surface adhesion molecules such as selectin ligands, integrins and mucins have been implicated in the pathogenesis of several solid and hematological malignancies, often with prognostic implications. In this review we focus on the functional significance of alterations in cancer cell glycosylation, in terms of cell adhesion, trafficking and the metastatic cascade and provide insights into the prognostic and therapeutic implications of recent findings in this fast-evolving niche.

The (1->6)-β-glucan moiety represents a cross-reactive epitope of infection-induced malignancy surveillance

Exposure to pathogen-associated molecular patterns (PAMPs) by vaccination or infection is known to have beneficial effects on neoplastic diseases, although the underlying molecular mechanisms are so far unclear. In this article, we report that Abs against (1→6)-β-d-glucan, a typical microbial PAMP and a major target for high titer circulating natural Abs in healthy human subjects, cross-recognize a novel tumor-associated carbohydrate Ag on cancer cells. The (1→6)-β-glucan cross-reactive moiety is immunologically dominant in tumor cells, as C57BL/6 mice harboring EL-4 solid tumors produced anti-(1→6)-β-glucan Abs and the titer of which significantly correlated with enhanced survival and smaller tumor burden. Moreover, the (1→6)-β-glucan-specific Abs exhibited potent tumoricidal activities in vitro. C57BL/6 mice immunized with Candida albicans produced protective immunity against inoculated EL-4 tumors, which was attributed to the formation of (1→6)-β-glucan-specific Abs. Importantly, (1→6)-β-glucan-specific Abs significantly prolonged the survival and reduced the tumor size in mice inoculated with EL-4 tumors. Our results demonstrate that the (1→6)-β-glucan cross-reactive moiety represents a focal point between infection immunity and cancer surveillance, and natural Abs against this epitope may contribute to the first-line antitumor surveillance in humans. Our data also provide important explanation for the long-observed relationship between feverish infection and concurrent remission from cancer.

Engagement of I-branching {beta}-1, 6-N-acetylglucosaminyltransferase 2 in breast cancer metastasis and TGF-{beta} signaling

In this study, we have showed that GCNT2, a gene-encoding glucosaminyl (N-acetyl) transferase 2, I-branching enzyme, is overexpressed in highly metastatic breast cancer cell lines of human and mouse origin and basal-like breast tumor samples. GCNT2 expression is also significantly correlated to the metastatic phenotype in breast tumor samples. Functional studies showed that ectopic expression of GCNT2 enhances cell detachment, adhesion to endothelial cells, cell migration and invasion in vitro, and lung metastasis of breast cancer cells in vivo. Knockdown of GCNT2 expression decreases cell migration and invasion in vitro and lung metastasis in vivo. We have further shown the involvement of GCNT2 in the epithelial-to-mesenchymal transition (EMT). Specifically, the expression of E-cadherin is significantly changed upon GCNT2 expression at the protein level but not at the RNA level. Moreover, we have shown that GCNT2 is a direct target of the TGF-β-smad pathway and that change in GCNT2 expression modulates EMT induced by TGF-β1 treatment. Finally, we have shown that diminution of the glycosyltransferase activity of I-branching β-1, 6-N-acetylglucosaminyl transferase 2 (GCNT2) abrogates its cell migration and invasion-promoting function and synergistic effect with TGF-β to induce EMT. Our study for the first time showed that GCNT2 is a novel gene contributing to breast cancer metastasis with preferential expression in basal-like breast cancer. Moreover, we discovered that involvement of GCNT2 in EMT and TGF-β signaling, and further glycosylation modification of E-cadherin by GCNT2, are the underlying integrative mechanisms for breast cancer metastasis, implying that blocking TGF-β/GCNT2 signaling is a promising approach for targeting metastatic breast cancer.

Identification of proteins bearing beta1-6 branched N-glycans in human melanoma cell lines from different progression stages by tandem mass spectrometry analysis

The common structural alterations in the cell-surface glycoproteins concern the highly elevated expression of tri- and tetra-antennary beta1-6-N-acetylglucosamine (beta1-6 GlcNAc) bearing N-glycans, which are recognised by Phaseolus vulgaris agglutinin (PHA-L). In this report we identified proteins bearing beta1-6 GlcNAc branched N-glycans in three human melanoma cell lines: WM35--from the primary tumour site, as well as WM239 and WM9 from different metastatic sites: the skin and the lymph node, respectively, by tandem mass spectrometry (MS/MS) on PHA-L agarose bound material, followed by immunochemical identification. Our results show that melanoma cell lines differ from each other in the number of N-glycoproteins bearing beta1-6 GlcNAc branched oligosaccharides. Among identified proteins the largest group consists of integrin subunits. In addition, L1-CAM, Mac-2 binding protein, melanoma cell adhesion molecule, intercellular adhesion molecule, melanoma associated antigen, tumour rejection antigen-1, melanoma-associated chondroitin sulfate proteoglycan 4 and lysosome-associated membrane protein (LAMP-1) were found. It was indicated that WM35 cell line showed the lowest number of proteins possessing beta1-6 GlcNAc branched N-glycans in comparison to metastatic WM9 and WM239 cell lines. Our data suggest that changes in the number of proteins being a substrate for GlcNAc-TV are better correlated with melanoma development and progression than with expression of cell adhesion molecules.

The potentials of MS-based subproteomic approaches in medical science: the case of lysosomes and breast cancer

Because of the great number of women who are diagnosed with breast cancer each year, and though this disease presents the lowest mortality rate among cancers, breast cancer remains a major public health problem. As for any cancer, the tumorigenic and metastatic processes are still hardly understood, and the biochemical markers that allow either a precise monitoring of the disease or the classification of the numerous forms of breast cancer remain too scarce. Therefore, great hopes are put on the development of high-throughput genomic and proteomic technologies. Such comprehensive techniques should help in understanding the processes and in defining steps of the disease by depicting specific genes or protein profiles. Because techniques dedicated to the current proteomic challenges are continuously improving, the probability of the discovery of new potential protein biomarkers is rapidly increasing. In addition, the identification of such markers should be eased by lowering the sample complexity; e.g., by sample fractionation, either according to specific physico-chemical properties of the proteins, or by focusing on definite subcellular compartments. In particular, proteins of the lysosomal compartment have been shown to be prone to alterations in their localization, expression, or post-translational modifications (PTMs) during the cancer process. Some of them, such as the aspartic protease cathepsin D (CatD), have even been proven as participating actively in the disease progression. The present review aims at giving an overview of the implication of the lysosome in breast cancer, and at showing how subproteomics and the constantly refining MS-based proteomic techniques may help in making breast cancer research progress, and thus, hopefully, in improving disease treatment.

Characterization and In Vitro Cytotoxic Effect of Adriamycin-conjugated Monoclonal Antibody Prepared Against Breast Cancer Cell Line

We have produced an adriamycin-conjugated monoclonal antibody, AM1, covalently linked by acid-labile cis-aconitic spacer. The immunoconjugate, cis-aconitic adriamycin(cAA)-AM1, was confirmed to retain the binding activity against human breast cancer cell lines by flow cytometry. The immunoconjugate was shown to be internalized into antigen-positive cancer cells by flow cytometry analysis and high performance liquid chromatography. Antitumor effects of cAA-AM1 were assessed on human breast cancer and colon cancer cell lines, with inhibition of (3) H-leucine uptakes to the cells. cAA-AM1 demonstrated a selective cytotoxicity to ZR-75-1 which was reactive with AM1, whereas it showed no antitumor effect on SW1116 cells which did not react with AM1. Free adriamycin demonstrated a non-selective cytotoxicity against both cell lines. AM1 alone and cAA-control IgM did not show any antitumor effect on ZR-75-1. These results suggest that cAA-AM1 retains binding activity and specificity against breast cancer cells in vitro.