Unveiling an alternative mechanism of action for bevacizumab therapy using breast cancer xenografts

• Autor(a) principal: Cardoso, Sara Filipa Tavares
• Data de Publicação: 2024
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/175432
• topic: Bevacizumab; scRNA-seq; Zebrafish tumor xenografts; Tumor-associated macrophages; Hippo signaling; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Angiogenesis is the formation of new blood vessels from pre-existing ones and it is a well-recognized hallmark of cancer targeted in anti-tumoral therapies. Bevacizumab is a monoclonal antibody that specifically binds to VEGF-A and inhibits this process. Patient responses to this drug are highly heterogenous and no therapy biomarkers have been identified to date, highlighting the importance of better understanding its mechanism of action. Fior’s lab at the Champalimaud Foundation uses zebrafish tumor xenografts to study tumor-associated mechanisms. During a study to establish the feasibility of this model to screen bevacizumab, it was discovered that treated triple-negative breast cancer (Hs578T) xenografts presented a reduction in tumor size and a higher infiltration of proinflammatory tumor-associated macrophages (TAMs). This suggested that this drug was acting through the modulation of macrophages in the tumor microenvironment (TME). The aim of this work was to help unravel the molecular dynamics in the TME upon bevacizumab treatment in Hs578T zebrafish xenografts. To achieve this, computational and experimental approaches were used. The analysis of single-cell RNA sequencing (scRNA-seq) data of zebrafish TAMs revealed the presence of subpopulations with different immune profiles at an early timepoint, although few alterations were observed between the control and treatment groups. The low expression of VEGF-A receptors in these cells suggested that bevacizumab is acting via an inderect mechanism. scRNA-seq data of tumor cells at later timepoints allowed to identify therapy-resistant and -sensitive clusters, as well as several molecular pathways differentially enriched between conditions. Hippo signaling emerged as one possible mechanism bridging the communication between tumor and TAMS, mediating the action of bevacizumab. Vasculogenesis was upregulated in the treated cells, arising as a possible alternative process to angiogenesis. Confocal microscopy imaging of the TME unraveled that the vascular network of this model is mainly composed of vascular and not lymphatic endothelial cells, validating previous results obtained in the lab. Overall, this work contributed to explore the dynamics of Hs578T zebrafish xenografts upon bevacizumab treatment and enabled the construction of a proposed working model for this drug, which can serve as a guide for future research.