A CAM bioimaging model reveals the connection between VEGFA vascular remodeling and enhanced sarcoma progression via tumor secretome

We developed a sensitive bioimaging system for sarcoma by creating a cell line that stably expresses both Katushka2S fluorophore and NanoLuc luciferase, enabling robust dual tracking of tumor growth and metastasis in the chick chorioallantoic membrane (CAM) model. NanoLuc luciferase was notably more effective than Katushka2S for identifying tumor cell metastases in embryo tissues. Pretreating CAM with tumor cell-conditioned medium (TCM) significantly increased neovascularization, Ki67 expression, tumor volumes, and metastasis of the most difficult-to-establish low-tumorigenic and low-metastatic U2OS cells, indicating that tumor cell secretome actively alter the CAM vascular environment to aid tumor progression. The bead-based multiplex profiling of the TCM demonstrated a notable increase in pro-angiogenic factors. Neutralizing VEGFA, the most abundant factor in the TCM, effectively counteracted vascular and pro-metastatic effects of TCM. In contrast, elevating VEGFA levels brought back the pro-tumorigenic effects of TCM. This study reveals the importance of tumor cell secretomes in creating the vascular niche in CAM and points to VEGFA as a target to prevent secretome-induced angiogenesis and sarcoma development. Furthermore, our optimized CAM model permits continuous tumor growth and metastasis monitoring in embryonic development, providing a reliable platform for prognostic studies of sarcoma treatments in ongoing anti-angiogenic and multikinase inhibitors trials.