PF-4/CXCL4 and CXCL4L1 exhibit distinct subcellular localization and a differentially regulated mechanism of secretion

AbstractPF-4/CXCL4 is a member of the CXC chemokine family, which is mainly produced by platelets and known for its pleiotropic biological functions. Recently, the proteic product of a nonallelic variant gene of CXCL4 was isolated from human platelets and named as CXCL4L1. CXCL4L1 shows only 4.3% amino acid divergence in the mature protein, but exhibits a 38% amino acid divergence in the signal peptide region. We hypothesized that this may imply a difference in the cell type in which CXCL4L1 is expressed or a difference in its mode of secretion. In different types of transfected cells, CXCL4 and CXCL4L1 exhibited a distinct subcellular localization and a differential regulation of secretion, CXCL4 being stored in secretory granules and released in response to protein kinase C activation, whereas CXCL4L1 was continuously synthesized and secreted through a constitutive pathway. A protein kinase C-regulated CXCL4 secretion was observed also in lymphocytes, a cell type expressing mainly CXCL4 mRNA, whereas smooth muscle cells, which preferentially expressed CXCL4L1, exhibited a constitutive pathway of secretion. These results demonstrate that CXCL4 and CXCL4L1 exhibit a distinct subcellular localization and are secreted in a differentially regulated manner, suggesting distinct roles in inflammatory or homeostatic processes

Etude des inhibiteurs de l'angiogenèse de type CXCL4 / CXCL4L1 et identification de nouvelles cibles moléculaires

Les nouveaux traitements contre le cancer, utilisés en clinique, ciblent la néovascularisation nécessaire à la progression de la tumeur. Cette vascularisation se met en place lors de l'angiogenèse tumorale. Les cellules endothéliales formant ces vaisseaux sanguins sont homogènes et génétiquement stables contrairement aux cellules cancéreuses. Elles constituent alors une cible thérapeutique de choix. En étudiant le protéome de xénogreffes de glioblastomes sur la membrane choriollantoïdienne de poulet, à différents stades de vascularisation, nous avons dressé une liste de protéines pouvant être impliquées dans l'angiogenèse tumorale. A partir de ce travail, des protéines induisant dans la vascularisation de la tumeur doivent être étudiées plus en avant pour, à terme, servir de cibles thérapeutiques. Mieux connaître l'expression et la régularisation de molécules décrites comme angiostatiques, telle que la chimiokine CXCL4L1, est un premier pas vers leur utilisation à des fins thérapeutiques. CXCL4L1 mature ne diverge que de 4,3% par rapport au facteur plaquettaire 4 (CXCL4). Par contre, cette chimiokine est plus angiostatique que CXCL4. Il apparaît que les ARN messagers et les protéines CXCL4 et CXCL4L1 sont exprimés par des types cellulaires et tissulaires différents. De plus, ces molécules sont stockées de manière différente : CXCL4 est stocké dans les grannules denses de sécrétion des plaquettes alors que CXCL4L1 est sécrété de manière constitutive. Dans un second temps, nous avons mis en évidence le fait que l'ARN messager et la protéine CXCL4L1 sont surexprimés dans des adénocarcinomes pancréatiques humains. La médiane de survie des patients atteints d'un cancer pancréatique est très faible. Comprendre les mécanismes moléculaires induisant l'expression de CXCL4L1 dans ces tumeurs peut servir à la mise en place de traitements dans ce type de cancer.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Cancer-associated fibroblasts in renal cell carcinoma: implication in prognosis and resistance to anti-angiogenic therapy

International audienceObjectives: To investigate the role of cancer-associated fibroblasts (CAFs) in clear cell renal cell carcinoma (ccRCC) with respect to tumour aggressiveness, metastasis development, and resistance to anti-angiogenic therapy (vascular endothelial growth factor receptor-tyrosine kinase inhibitors [VEGFR-TKI]).Patients and methods: Our study involved tissue samples from three distinct and independent cohorts of patients with ccRCC. The presence of CAFs and tumour lymphangiogenesis was investigated, respectively, by transcriptional signatures and then correlated with tumour development and prognosis. The effect of these CAFs on tumour cell migration and VEGFR-TKI resistance was analysed on co-cultures of ccRCC cells with CAFs.Results: Results from our cohorts and from in silico investigations showed that VEGFR-TKI significantly increase the number of CAFs in tumours. In the same populations of patients with ccRCC, the proportion of intra-tumoral CAFs correlated to shorter disease-free and overall survival. The presence of CAFs was also correlated with lymphangiogenesis and lymph node metastasis. CAFs increased the migration and decreased the VEGFR-TKI-dependent cytotoxic effect of tumour cells.Conclusions: Our results show that VEGFR-TKI promote the development of CAFs, and CAFs favour tumour aggressiveness, metastatic dissemination, and resistance to treatment in ccRCC. CAFs could represent a new therapeutic target to fight resistance to treatment of ccRCC. Targeting CAF and immunotherapies combination are emerging as efficient treatments in many types of solid tumours. Our results highlight their relevance in ccRCC

Dual Roles for CXCL4 Chemokines and CXCR3 in Angiogenesis and Invasion of Pancreatic Cancer.

The CXCL4 paralog CXCL4L1 is a less studied chemokine that has been suggested to exert an antiangiogenic function. However, CXCL4L1 is also expressed in patient tumors, tumor cell lines, and murine xenografts, prompting a more detailed analysis of its role in cancer pathogenesis. We used genetic and antibody-based approaches to attenuate CXCL4L1 in models of pancreatic ductal adenocarcinoma (PDAC). Mechanisms of expression were assessed in cell coculture experiments, murine, and avian xenotransplants, including through an evaluation of CpG methylation and mutation of critical CpG residues. CXCL4L1 gene expression was increased greatly in primary and metastatic PDAC. We found that myofibroblasts triggered cues in the tumor microenvironment, which led to induction of CXCL4L1 in tumor cells. CXCL4L1 expression was also controlled by epigenetic modifications at critical CpG islands, which were mapped. CXCL4L1 inhibited angiogenesis but also affected tumor development more directly, depending on the tumor cell type. In vivo administration of an mAb against CXCL4L1 demonstrated a blockade in the growth of tumors positive for CXCR3, a critical receptor for CXCL4 ligands. Our findings define a protumorigenic role in PDAC development for endogenous CXCL4L1, which is independent of its antiangiogenic function. Cancer Res; 76(22); 6507-19. (c)2016 AACR