The metastatic T-cell hybridoma antigen/P-selectin glycoprotein ligand 1 is required for hematogenous metastasis of lymphomas

Antibody targeting of surface P-selectin glycoprotein ligand 1 leads to lymphoma apoptosis and tumorigenesis inhibition

Lymphomas are a heterogeneous group of diseases that originate from T, B or natural killer cells. Lymphoma treatment is based on chemotherapy, radiotherapy, and monoclonal antibody (mAb) or other immunotherapies. The P-selectin glycoprotein ligand 1 (PSGL-1) is expressed at the surface of hematological malignant cells and has been shown to have a pro-oncogenic role in multiple myeloma and lymphoma. Here, we investigated the expression and therapeutic potential of PSGL-1 in T and B cell lymphomas. By flow cytometry analysis, we found that PSGL-1 was expressed in both T and B cell-derived lymphoma cell lines but generally at higher levels in T cell lymphoma cell lines. For most T and B cell-derived lymphoma cell lines, in vitro targeting with the PL1 mAb, which recognizes the PSGL-1 N-terminal extracellular region and blocks functional interactions with selectins, resulted in reduced cell viability. The PL1 mAb pro-apoptotic activity was shown to be dose-dependent, to be linked to increased ERK kinase phosphorylation, and to be dependent on the MAP kinase signaling pathway. Importantly, anti-PSGL-1 treatment of mice xenografted with the HUT-78 cutaneous T-cell lymphoma cell line resulted in decreased tumor growth, had no effect on in vivo proliferation, but increased the levels of apoptosis in tumors. Anti-PSGL-1 treatment of mice xenografted with a Burkitt lymphoma cell line that was resistant to anti-PSGL-1 treatment in vitro, had no impact on tumorigenesis. These findings show that PSGL-1 antibody targeting triggers lymphoma cell apoptosis and substantiates PSGL-1 as a potential target for lymphoma therapy.

P-selectin glycoprotein ligand 1 promotes T cell lymphoma development and dissemination

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PSGL-1 protein is frequently expressed at the surface of malignant T cells.

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Enforced expression of PSGL-1 promotes T cell tumorigenesis in mice.

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PSGL-1 expression accelerates malignant T cell dissemination from tumors to several organs.

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PSGL-1 expression promotes malignant T cell expansion in kidneys and lungs.

P-selectin glycoprotein ligand-1 (PSGL-1) is a membrane-bound glycoprotein expressed in lymphoid and myeloid cells. It is a ligand of P-, E- and L-selectin and is involved in T cell trafficking and homing to lymphoid tissues, among other functions. PSGL-1 expression has been implicated in different lymphoid malignancies, so here we aimed to evaluate the involvement of PSGL-1 in T cell lymphomagenesis and dissemination. PSGL-1 was highly expressed at the surface of human and mouse T cell leukemia and lymphoma cell lines. To assess its impact on T cell malignancies, we stably expressed human PSGL-1 (hPSGL-1) in a mouse thymic lymphoma cell line, which expresses low levels of endogenous PSGL-1 at the cell surface. hPSGL-1-expressing lymphoma cells developed subcutaneous tumors in athymic nude mice recipients faster than control empty vector or parental cells. Moreover, the kidneys, lungs and liver of tumor-bearing mice were infiltrated by hPSGL-1-expressing malignant T cells. To evaluate the role of PSGL-1 in lymphoma cell dissemination, we injected intravenously control and hPSGL-1-expressing lymphoma cells in athymic mice. Strikingly, PSGL-1 expression facilitated disease infiltration of the kidneys, as determined by histological analysis and anti-CD3 immunohistochemistry. Together, these results indicate that PSGL-1 expression promotes T cell lymphoma development and dissemination to different organs.

Acute Myeloid Leukemia Chemo-Resistance Is Mediated by E-selectin Receptor CD162 in Bone Marrow Niches

The interactions of leukemia cells with the bone marrow (BM) microenvironment is critical for disease progression and resistance to treatment. We have recently found that the vascular adhesion molecule E-(endothelial)-selectin is a key niche component that directly mediates acute myeloid leukemia (AML) chemo-resistance, revealing E-selectin as a promising therapeutic target. To understand how E-selectin promotes AML survival, we investigated the potential receptors on AML cells involved in E-selectin-mediated chemo-resistance. Using CRISPR-Cas9 gene editing to selectively suppress canonical E-selectin receptors CD44 or P-selectin glycoprotein ligand-1 (PSGL-1/CD162) from human AML cell line KG1a, we show that CD162, but not CD44, is necessary for E-selectin-mediated chemo-resistance in vitro. Using preclinical models of murine AML, we then demonstrate that absence of CD162 on AML cell surface leads to a significant delay in the onset of leukemia and a significant increase in sensitivity to chemotherapy in vivo associated with a more rapid in vivo proliferation compared to wild-type AML and a lower BM retention. Together, these data reveal for the first time that CD162 is a key AML cell surface receptor involved in AML progression, BM retention and chemo-resistance. These findings highlight specific blockade of AML cell surface CD162 as a potential novel niche-based strategy to improve the efficacy of AML therapy.

Multiple Roles of Glycans in Hematological Malignancies

The three types of blood cells (red blood cells for carrying oxygen, white blood cells for immune protection, and platelets for wound clotting) arise from hematopoietic stem/progenitor cells in the adult bone marrow, and function in physiological regulation and communication with local microenvironments to maintain systemic homeostasis. Hematological malignancies are relatively uncommon malignant disorders derived from the two major blood cell lineages: myeloid (leukemia) and lymphoid (lymphoma). Malignant clones lose their regulatory mechanisms, resulting in production of a large number of dysfunctional cells and destruction of normal hematopoiesis. Glycans are one of the four major types of essential biological macromolecules, along with nucleic acids, proteins, and lipids. Major glycan subgroups are N-glycans, O-glycans, glycosaminoglycans, and glycosphingolipids. Aberrant expression of glycan structures, resulting from dysregulation of glycan-related genes, is associated with cancer development and progression in terms of cell signaling and communication, tumor cell dissociation and invasion, cell-matrix interactions, tumor angiogenesis, immune modulation, and metastasis formation. Aberrant glycan expression occurs in most hematological malignancies, notably acute myeloid leukemia, myeloproliferative neoplasms, and multiple myeloma, etc. Here, we review recent research advances regarding aberrant glycans, their related genes, and their roles in hematological malignancies. Our improved understanding of the mechanisms that underlie aberrant patterns of glycosylation will lead to development of novel, more effective therapeutic approaches targeted to hematological malignancies.

The Interaction of Selectins and PSGL-1 as a Key Component in Thrombus Formation and Cancer Progression

Cellular interaction is inevitable in the pathomechanism of human disease. Formation of heterotypic cellular aggregates, between distinct cells of hematopoietic and nonhematopoietic origin, may be involved in events leading to inflammation and the complex process of cancer progression. Among adhesion receptors, the family of selectins with their ligands have been considered as one of the major contributors to cell-cell interactions. Consequently, the inhibition of the interplay between selectins and their ligands may have potential therapeutic benefits. In this review, we focus on the current evidence on the selectins as crucial modulators of inflammatory, thrombotic, and malignant disorders. Knowing that there is promiscuity in selectin binding, we outline the importance of a key protein that serves as a ligand for all selectins. This dimeric mucin, the P-selectin glycoprotein ligand 1 (PSGL-1), has emerged as a major player in inflammation, thrombus, and cancer development. We discuss the interaction of PSGL-1 with various selectins in physiological and pathological processes with particular emphasis on mechanisms that lead to severe disease.

C-type lectins facilitate tumor metastasis

Metastasis, a life-threatening complication of cancer, leads to the majority of cases of cancer-associated mortality. Unfortunately, the underlying molecular and cellular mechanisms of cancer metastasis remain to be fully elucidated. C-type lectins are a large group of proteins, which share structurally homologous carbohydrate-recognition domains (CRDs) and possess diverse physiological functions, including inflammation and antimicrobial immunity. Accumulating evidence has demonstrated the contribution of C-type lectins in different steps of the metastatic spread of cancer. Notably, a substantial proportion of C-type lectins, including selectins, mannose receptor (MR) and liver and lymph node sinusoidal endothelial cell C-type lectin, are important molecular targets for the formation of metastases in vitro and in vivo. The present review summarizes what has been found regarding C-type lectins in the lymphatic and hematogenous metastasis of cancer. An improved understanding the role of C-type lectins in cancer metastasis provides a comprehensive perspective for further clarifying the molecular mechanisms of cancer metastasis and supports the development of novel C-type lectins-based therapies the for prevention of metastasis in certain types of cancer.

Transfection of miRNAs targeting the FUT3 gene inhibits cell proliferation in human gastric cancer cell line KATO-III

AIM: To investigate the effect of inhibition of FUT3 gene expression with miRNAs on the proliferation of gastric cancer cells (KATO-Ⅲ).

METHODS: Vectors carrying two miRNAs targeting the FUT3 gene were constructed and transiently transfected into KATO-III cells using lipidosome-mediated method. RT-PCR was performed to detect the expression of FUT3 mRNA, and immunocytochemistry and flow cytometry analysis were carried out to test expression variation of sLeA antigen. MTT assay and colony-forming assay were used to analyze cell proliferation and to detect the effect of decreased FUT3 expression on cell growth.

RESULTS: Compared to non-transfected cells and cells transfected with empty vector, the relative expression levels of FUT3 mRNA were significantly decreased (0.41 ± 0.01 vs 0.71 ± 0.05, 0.65 ± 0.03, both P < 0.05; 0.36 ± 0.02 vs 0.71 ± 0.05, 0.65 ± 0.03, both P < 0.05); the sLeA antigen expression levels were also significantly reduced (35.51% ± 0.36% vs 52.79% ± 2.62%, 49.75% ± 1.29%, both P < 0.05; 26.05% ± 1.14% vs 52.79% ± 2.62%, 49.75% ± 1.29%, both P < 0.05); cell growth was significantly inhibited (38.10% ± 1.96% vs 5.6% ± 0.63%, 8.9% ± 0.91%, both P < 0.05; 49.04% ± 2.37% vs 5.6% ± 0.63%, 8.9% ± 0.91%, both P < 0.05); and colony-forming ability was significantly reduced (14.10% ± 1.70% vs 29.79% ± 3.05%, 28.92% ± 2.10%, both P < 0.05; 12.50% ± 1.96% vs 29.79% ± 3.05%, 28.92% ± 2.10%, both P < 0.05) in FUT3-miRNA and FUT3-miRNA2 transfeced cells.

CONCLUSION: Transfection of miRNAs targeting the FUT3 gene can effectively inhibit the proliferation of KATO-Ⅲ cells.

Activated platelets interact with lung cancer cells through P-selectin glycoprotein ligand-1

Hematogenous metastasis always leads to the poor prognosis of non-small cell lung cancers (NSCLC). Activated platelets are involved in hematogenous metastasis and may be a potential therapeutic target. P-selectin is an important adhesion molecule and expressed on the surface of activated platelets. P-selectin glycoprotein ligand-1 (PSGL-1) as a transmembrane protein is expressed on the surface of various cell types. P-selectin can bind to PSGL-1, and thereby initiate the platelet-mediated cell adhesion. The aim of the study was to investigate the degree of platelet activation in NSCLC and the roles of PSGL-1 in the activation of platelets. Purified platelets were obtained from NSCLC patients (40 lung adenocarcinomas and 26 lung squamous cell carcinomas), and P-selectin expression was detected by fluorescence-activated cell sorter. The population of peripheral blood platelets with P-selectin expression in lung adenocarcinoma was 63.16 ± 25.44 %, and significantly higher than that in lung squamous cell carcinoma (35.97 ± 17.19 %) and the healthy population (9.12 ± 7.66 %, n = 30). A specific small hairpin RNA (shRNA) for PSGL-1 was transfected into A549 human alveolar cell carcinoma cells. The expressions of PSGL-1 mRNA and protein were significantly reduced with the PSGL-1 shRNA (p < 0.01). Furthermore, the knockdown of PSGL-1 also resulted in the significantly reduced aggregate formation of activated platelets and A549 cells. Thus, activated platelets may interact with lung cancer cells through PSGL-1. Inhibiting platelet activation and/or down-regulating PSGL-1 expression may be useful for suppression of tumor metastasis.

P-selectin glycoprotein ligand-1 positive microparticles in allogeneic stem cell transplantation of hematologic malignancies

P-selectin and its receptor P-selectin glycoprotein ligand-1 (PSGL-1) mediate adhesion between leukocytes, tumor cells (including leukemias and lymphomas), and platelets, and play an important role in hematopoiesis, T cell activation, and cancer growth and metastasis. As microparticles (MPs) are released from activated or apoptotic cells, there should be significant numbers of circulating PSGL-1-bearing MPs in the blood of patients undergoing allogeneic stem cell transplantation (alloSCT). We enumerated PSGL-1-expressing MPs in plasma samples from 30 consecutive patients with hematologic disorders at different time points during the course of alloSCT by flow cytometry and analyzed their relation to cell counts, patient characteristics, and clinical outcome. Median follow-up time of surviving patients was 1,772 days (range 1272-1981 days). Nineteen patients (63.3%) died, 10 due to progression of disease (33.3%). The PSGL-1 MPs significantly declined during conditioning therapy but increased again after transfusion of donor cells and even more at the time of engraftment. Numbers >250/μL after graft transfusion were associated with a shorter time to engraftment for patients receiving fresh peripheral stem cell grafts (median, 15 vs. 21 days; p = 0.049). Furthermore, low PSGL-1 MP values at those two time points were associated with a higher risk of progress/relapse in univariate analysis (p = 0.008-0.014; hazard ratio [HR] = 15.0-42.0) with cumulative incidences at 5 years of 81.8% versus 28.6% and 85.7% versus 20.0%, respectively. In conclusion, PSGL-1 microparticles show a characteristic course during alloSCT and their possible association with relapse/progress requires further evaluation of the PSGL-1/P-selectin interaction in leukemias and lymphomas.

Primary effusion lymphoma: genomic profiling revealed amplification of SELPLG and CORO1C encoding for proteins important for cell migration

Primary effusion lymphoma (PEL) is associated with Kaposi sarcoma herpesvirus (KSHV) but its pathogenesis is poorly understood. Many KSHV-associated products can deregulate cellular pathways commonly targeted in cancer. However, KSHV infection alone is insufficient for malignant transformation. PEL also lacks the chromosomal translocations seen in other lymphoma subtypes. We investigated 28 PELs and ten PEL cell lines by 1 Mb resolution array comparative genomic hybridization (CGH) and found frequent gains of 1q21-41 (47%), 4q28.3-35 (29%), 7q (58%), 8q (63%), 11 (32%), 12 (61%), 17q (29%), 19p (34%), and 20q (34%), and losses of 4q (32%), 11q25 (29%), and 14q32 (63%). Recurrent focal amplification was seen at several regions on chromosomes 7, 8, and 12. High-resolution chromosome-specific tile-path array CGH confirmed these findings, and identified selectin-P ligand (SELPLG) and coronin-1C (CORO1C) as the targets of a cryptic amplification at 12q24.11. Interphase FISH and quantitative PCR showed SELPLG/CORO1C amplification (>4 extra copies) and low levels of copy number gain (1-4 extra copies) in 23% of PELs, respectively. Immunohistochemistry revealed strong expression of both SELPLG and coronin-1C in the majority of PELs, irrespective of their gene dosage. SELPLG is critical for cell migration and chemotaxis, while CORO1C regulates actin-dependent processes, thus important for cell motility. Their overexpression in PEL is expected to play an important role in its pathogenesis.

Construction of human FUT3 eukaryotic expression vector and its expression in human breast adenocarcinoma cells

AIM: To construct the human FUT3 (α 1, 3-fucosyltransferase) eukaryotic expression vector and analyze its expression in human breast adenocarcinoma MDA-MB-231 cells.

METHODS: The full-length FUT3 cDNA was obtained by reverse transcription-polymerase chain reaction (RT-PCR) and cloned into pMD18-T simple vector for sequence analysis. Then the FUT3 gene was subcloned into pEGFP-C1 plasmid. The resulting recombinant vector pEGFP-C1-FUT3 was identified by digestion with restriction endonucleases and transfected into MDA-MB-231 cells. A stably transfected cell line was established using G418 selection. The expression of FUT3 was observed under a fluorescence microscope and examined by semi-quantitative RT-PCR.

RESULTS: The full-length human FUT3 cDNA was successfully obtained, and the recombinant plasmid pEGFP-C1-FUT3 was successfully constructed. After transfection into MDA-MB-231 cells, green fluorescence (green fluorescent protein) was observed. Semi-quantitative RT-PCR analysis showed that FUT3 was highly expressed in MDA-MB-231 cells.

CONCLUSION: The FUT3 eukaryotic expression vector pEGFP-C1-FUT3 that can express FUT3 in MDA-MB-231 cells is constructed successfully and can be used to study the biological functions of the FUT3 gene.

Separable requirements for cytoplasmic domain of PSGL-1 in leukocyte rolling and signaling under flow

In inflamed venules, leukocytes use P-selectin glycoprotein ligand-1 (PSGL-1) to roll on P-selectin and E-selectin and to activate integrin alphaLbeta2 (lymphocyte function-associated antigen-1, LFA-1) to slow rolling on intercellular adhesion molecule-1 (ICAM-1). Studies in cell lines have suggested that PSGL-1 requires its cytoplasmic domain to localize in membrane domains, to support rolling on P-selectin, and to signal through spleen tyrosine kinase (Syk). We generated "DeltaCD" mice that express PSGL-1 without the cytoplasmic domain. Unexpectedly, neutrophils from these mice localized PSGL-1 normally in microvilli, uropods, and lipid rafts. DeltaCD neutrophils expressed less PSGL-1 on their surfaces because of inefficient export from the endoplasmic reticulum. Limited digestion of wild-type neutrophils with O-sialoglycoprotein endopeptidase was used to reduce the PSGL-1 density to that on DeltaCD neutrophils. At matched PSGL-1 densities, both DeltaCD and wild-type neutrophils rolled similarly on P-selectin. However, DeltaCD neutrophils rolling on P-selectin did not trigger Syk-dependent activation of LFA-1 to slow rolling on ICAM-1. These data demonstrate that the PSGL-1 cytoplasmic domain is dispensable for leukocyte rolling on P-selectin but is essential to activate beta2 integrins to slow rolling on ICAM-1.