Investigating immune cell recruitment into solid tumors using a zebrafish melanoma model

• Applicant: Dr. Johannes Krug
• Subject Area: Hematology, Oncology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572368082

Immunotherapies have been more successful in treating hematologic malignancies than solid tumors. A key limitation for their success is the insufficient recruitment of immune cells capable of overcoming the immunosuppressive tumor microenvironment. My proposal focuses on investigating factors crucial for immune cell recruitment, ultimately promoting tumor cell death, by using a zebrafish melanoma model. The proposed work comprises 6 work packages (WPs). WP1 focuses on identifying factors underlying immune cell infiltration. To address this, tumors injected with the immune stimulant CpG ODN will be analyzed via a multi-omics approach including RNA-seq, lipidomics, and spatial transcriptomics. Identified factors will be verified in WP2 regarding their potential to increase immune infiltration by TEAZ (transgene electroporation in adult zebrafish) or intratumoral injections of candidates, followed by flow cytometry-based analysis. Factors with the highest potential to recruit immune cells will be further analyzed in WP3 via gene inactivation or overexpression to determine their impact on tumorigenesis. This should reveal factors that prevent or delay the onset of tumor formation. In addition, the proposed work includes the analysis of natural killer (NK) cells. To study their impact on melanoma, NK cell-specific reporter lines will be generated via a knock-in of a reporter cassette (WP4). This reporter will allow visualization (eGFP) and, in addition, ablation of NK cells (NTR/Mtz system). The zebrafish melanoma model allows to study different stages of melanoma formation. Hence, I will investigate the role of NK cells in immunosurveillance (WP5). Different stages of melanoma will be investigated for the presence of NK cells via imaging. The activity of NK cells throughout the different stages will be investigated via RNA-seq to determine whether and when these cells might become dysfunctional during tumor formation. Ablation of NK cells aims to elucidate their impact on melanoma formation (WP6). In summary, this research proposal aims to gain a better understanding of immune cell recruitment into solid tumors. Identified factors can serve as therapeutic targets to improve future immunotherapies for solid tumors. Furthermore, due to their cytotoxic activity, NK cells show great potential for eliminating cancer cells. Investigating their potential and understanding mechanisms that counteract their inactivation by the immunosuppressive tumor microenvironment is crucial for their use in combating cancer.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. Leonard Zon