Systematic dissection and characterization of in vivo pathomechanisms of the type II transmembrane serine protease ST14 during epidermal carcinogenesis and metastasis in two zebrafish embryo models

• Applicant: Professor Dr. Matthias Hammerschmidt
• Subject Area: Developmental Biology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 453407124

Given that embryonic cells are generally relatively plastic and prone to become neoplastic, we have in the first funding period of project started to study epidermal carcinogenesis in vivo in zebrafish embryo mutants isolated from forward-genetics screens. In two of these mutants, epidermal carcinogenesis is caused by an aberrant activation of the type II transmembrane serine protease ST14, one bearing a loss-of-function mutation in the cognate ST14 inhibitor Hai1a, and one in Atp1b1a, a beta-subunit of a Na/K-pump that is otherwise unrelated to ST14. In humans, ST14 is known both as a tumor-suppressor and an oncogene, although the underlying mechanisms are not fully understood. Strikingly, depending on its different modes of hyper-activation, ST14 in atp1b1a zebrafish mutants activates different oncogenic pathways than in hai1a mutants, leading to more aggressive epidermal carcinogenesis, which also includes metastasis and which is reflected by the appearance of a new basal keratinocyte subcluster in our comparative scRNAseq analysis of hai1a and atp1b1a mutants. In the proposed follow-up project, these metastatic events will be studied in more depth, including further scRNAseq studies of atp1b1a mutants at later stages when metastasis in more advanced (Goal 1a) and addressing aspects of used migratory routs (Goal 1b), heterogeneity even among metastasizing cells (Goal 1c) and the impact of innate immune cells (Goal 1d). Furthermore, we will continue our functional analyses of selected genes that according to our scRNAseq data are up-regulated in metastasizing cells of atp1b1a, but not in hai1a mutants, which are likely neoplastic factors (Goal 2a), and of genes that are down-regulated, which are likely tumor-suppressors downstream of ST14 (Goal 2b). These analyses also include studies with chimeric embryos to discriminate between gene functions within cancer cells themselves and the tumor microenvironment. Finally, identified gene functions will be validated in different human carcinoma cell culture systems, investigating their impact on cell proliferation, cell motility and cell invasiveness (Goal 3). Together, these data will provide a detailed in vivo picture of pro-metastatic events dependent on ST14 activity and will delineate potential contextual explanations for the aggressiveness of carcinomas.

• DFG Programme: Research Grants