Cellule cancéreuse | EPFL Graph Search

Une cellule cancéreuse est une cellule anormale ayant acquis des caractères spécifiques à l'origine d'un cancer. Type de cellules cancéreuses Les cellules cancéreuses se distinguent selon le type de cellules dont elles descendent. Cellule présentant des anomalies au niveau de fragments chromosomiques ou de chromosomes entiers causant ainsi une perturbation de son cycle et une instabilité génétique. Qualifiée de siège de lésions génétiques, la cellule cancéreuse ne cesse de se diviser et refuse la coopération avec toute autre cellule normale.Un cancer se développe à partir d'une cellule normale altérée par un certain nombre d'anomalies – des mutations – qui ne sont pas réparées par les processus habituels. La cellule devient anormale et, si elle n'est pas détruite, se multiplie pour former une tumeur.Quelles sont les cellules cancéreuses ? Les cellules cancéreuses sont des cellules "anormales" engagées dans un processus anarchique où elles accumulent les anomalies.D'un po

Immunosuppressive roles of Activin-A in melanoma and characterization of its precursor cleavage

Katarina Pinjusic

Activin-A, a transforming growth factor êµ family member, is a pleiotropic cytokine with diverse functions in development, fertility, adult tissue homeostasis, and aging. Accordingly, deregulation of Activin-A signaling has been associated with many pathological conditions, including cancer and cancer-associated muscle wasting (cachexia). Activin-A was shown to signal in endocrine, but also local autocrine and paracrine manner. Its secretion in many cancer types is associated with a poor prognosis. Previous studies suggest that Activin-A expression in melanoma promotes tumor growth and metastasis indirectly by inhibiting adaptive anti-tumor immunity, leading to a decrease in the intratumoral frequency of cytotoxic CD8+ T cells (CTLs). However, the underlying mechanisms and the relevant direct target cells of Activin-A and their significance for cancer therapies remained unknown. Similar to other TGFêµ-related ligands, proActivin-A is cleaved by proprotein convertases (PCs) to release mature ligands. However, unlike other family members whose signaling is tightly regulated, Activin-A apparently does not have latency.In this thesis, I characterize proActivin-A cleavage and show that one prodomain can be cleaved independently of known PCs. The resulting hemi-cleaved Activin-A can bind activin type II receptors and induce SMAD3 signaling in reporter cells. A protein interactome screen and analysis of cleavage intermediates in plasma revealed that the hemi-cleaved Activin-A likely interacts with extracellular matrix proteins via the remaining prodomain where it promotes local signaling and regulates trafficking. Luciferase reporter assay showed that hemi-cleaved Activin-A can avoid, at least partially, inhibition by endogenous inhibitors FSTL3 and FST, and enable parallel activation of BMP and Activin signaling pathways. Finally, analysis of B16-F1 melanoma models revealed that only fully cleaved Activin-A in source cells increased tumor growth by acting locally in the tumor microenvironment suggesting that the context of Activin-A precursor processing regulates its tumor growth-promoting effect.The second part of this thesis addresses the mechanisms of Activin-induced immunosuppression in melanoma. We found that Activin-A impairs CTL function indirectly and independently of CD4+ T cell, CSF1R+ macrophages, and IL4 signaling. At least in part, anti-tumor CTL responses are impaired by the inhibitory effects of Activin-A on the secretion of critical CTL-recruiting chemokines CXCL9 and CXCL10 by macrophages and dendritic cells (DCs). Furthermore, Activin-A conferred resistance to immune checkpoint blockade therapy. Characterization of Activin-induced changes in the gene expression of tumor-infiltrating cells by Single cell RNA sequencing revealed that INHBA expression induced the most changes in DCs and least in T cells. Interestingly, the most prominently induced hallmark in Activin-secreting tumors across cell types was the IFN signature. In vitro analyses showed that Activin-A increases IFNÎ³-induced activation of STAT1 and confers resistance to cytostatic IFN signaling in cancer cells.Altogether, the findings of this thesis expand our knowledge on the regulation of Activin-A signaling by precursor cleavage and offer insights into mechanisms of Activin-induced immunosuppression in melanoma. Inhibition of Activin-A maturation thus emerges as a potential new strategy to improve responses to immunotherapies in melanoma and likely other cancers

EPFL2022

Integrative transcriptome analyses of Transposable Elements (TEs) and genes contribute to a better understanding of colorectal cancer

Eunji Shin

Cancer is the second leading cause of death worldwide. Cancer develops through multiple hallmark functions including apoptosis evasion, unlimited replicative potential, metastasis, and immune avoidance. Over the past few decades, researchers have reported a substantial amount of information about the role of gene expression dysregulation in cancer, whereas transposable elements (TEs) have been overlooked despite the fact they constitute nearly half of the human genome. TEs are DNA repetitive sequences that spread across the genome of living organisms throughout the evolution of species, contributing to genomic diversity and shaping the epigenomic landscape. The vast majority of TEs appear to be transcriptionally silent in adult tissues, thus avoiding deleterious mutational insertions and recombination events in somatic tissues. Due to the global epigenetic dysregulation that occurs during tumorigenesis, some TEs lose repressive marks and become transcriptionally active in cancer cells. Consequently, TE insertions into oncogenes and tumor suppressor genes may occur, thereby contributing to cancer development and disease progression. It is also widely accepted that some TEs harbor transcription factor recognition sites and have regulatory functions on gene expression. Some transcriptionally active TEs can give rise to alternative TE-derived chimeric gene products. Given these facts, integrative transcriptome analysis of TEs and genes may contribute to a better understanding of complex traits of cancer and help to better classify cancer subtypes with clinical implications for patients.To gain insights into the underlying mechanisms of cancer pathogenesis, we constructed a co-expression network based on the similarity in expression levels of TEs and genes. We focused on colorectal cancer (CRC), a heterogeneous disease with different genetic and molecular backgrounds, contributing to patient outcomes and response to therapy. We investigated the coordinated activity of TEs and genes in view of recurrent CRC chromosomal aberrations, genome organization, and functional significance. We further examined co-expression changes in network structure under the contrasting conditions of cancerous versus matched healthy colic mucosal tissues. We found that the cancer network was associated with a dramatic decrease in the number of gene interactions as opposed to an increase in TE interactions. Physical chromosomal distance affects the degree of co-expression, where the proximal distance effect of TE is contrasted with the distant effect of the gene. Our study sheds light on the complex interplay between TEs and genes and how they coordinately shape cancer and normal co-expression networks. Furthermore, we integrated gene and TE expression to develop a new consensus molecular subtype (CMS) classifier derived from multiple layers of TE and gene signatures. We demonstrated that our new approach led to better identification of CRC patients of the former CMS3 subtype, the most heterogeneous subtype with mixed biological characteristics, and a global reduction of the expected misclassification of other CMS subtypes. We further optimized our classifier for potential clinical use and obtained a set of 50 genes and 20 TE integrants with the best ability to identify CMS subtypes. Our integrative model could be a major add on for the development of future clinical trials by improving patient stratification over current gene-restricted molecular classifications.

EPFL2022

Cytosolic delivery and characterization of monobodies interfering with SH2 domain-phosphotyrosine interactions

Nadine Eliane Schmit

Targeted cancer therapy is a very promising concept; however, small molecule inhibitors only exist for a limited number of oncoproteins and resistance development limits their clinical use. Different engineered non-antibody scaffolds are being explored to develop potent protein-based inhibitors of oncoproteins, which can overcome these hurdles. The first goal of this thesis was to characterize monobodies, engineered binders based on the fibronectin type 3 domain, which were selected to bind the SH2 domains of 6 members of the Src kinase family that play a role in different types of cancer. I have shown that the monobodies bind specifically to their target in cells by performing tandem affinity purifications with subsequent mass spectrometry analysis. When expressed in T cells, the Lck-targeting monobodies ML1 and ML3 inhibit the phosphorylation of Zap70, a kinase which is activated downstream of T cell activation. Moreover, the fusion of ML1 or ML3 to VHL, the substrate receptor of an E3 ubiquitin ligase, resulted in the targeted degradation of Lck. The selected monobodies therefore have great potential to interfere with cancer cell signaling and to be used in therapeutic approaches. The development of protein-based inhibitors is currently limited to extracellular targets due to the inability of proteins to cross the cell membrane. Many approaches to achieve cellular delivery are hampered by non-selective cytotoxicity or endosomal entrapment of the protein cargo. The second aim of my thesis was to explore different methods to deliver functional monobodies into cancer cells. Firstly, I tested cell penetrating poly-disulfides (CPDs). CPD-monobody adducts showed toxic effects on the tested cell line, and mainly followed an endocytic uptake route leading to lysosomal degradation, when used at subtoxic concentrations. Secondly, bacterial toxins have naturally evolved to deliver their payload into the cytoplasm of host cells. Both Shiga-like toxins and Exotoxin A from Pseudomonas aeruginosa are taken up into the cytosol via a retrograde trafficking route, avoiding endosomal entrapment. To deliver monobodies to the cytosol, we have tested a combination of their non-toxic subunits: The B subunit of Shiga-like toxin (Stx2B), binding to the sphingolipid Gb3 in the cell membrane, and the translocation domain of Exotoxin A (TDP). We could show that recombinant Stx2B-TDP-Monobody fusion proteins are taken up in HeLa cells, which naturally express Gb3. Colocalization analyses with markers for endocytic compartments demonstrated that the major part of the monobodies escape early endosomes and are not degraded in lysosomes. A recombinant fusion protein of the Stx2B-TDP construct with the monobody AS25, which allosterically inhibits Bcr-Abl kinase, leads to apoptosis in Bcr-Abl-dependent chronic myeloid leukemia cells. Furthermore, the delivery of the VHL-ML3 fusion protein into Jurkat T cells results in decreased Lck levels. The delivery of both constructs is dependent on Gb3 on the cell surface as well as the Stx2B-TDP subunits. These results demonstrate that functional monobodies can be delivered to the cytosol and bind to their target protein in cells. This method could facilitate the development of protein-based inhibitors of intracellular proteins for cancer treatment.

EPFL2018

Immunosuppressive roles of Activin-A in melanoma and characterization of its precursor cleavage

Katarina Pinjusic

EPFL2022

Cytosolic delivery and characterization of monobodies interfering with SH2 domain-phosphotyrosine interactions

Nadine Eliane Schmit

EPFL2018

Integrative transcriptome analyses of Transposable Elements (TEs) and genes contribute to a better understanding of colorectal cancer

Eunji Shin

EPFL2022