CACFD1 (calcium channel flower domain containing 1) functions as a flower isoform that produces tissue-specific fitness fingerprints to identify and eliminate unfit cells during cell selection processes 1. In humans, CACFD1 behaves as a Flower-Win protein that confers competitive growth advantages to cells; cells with higher CACFD1 levels are recognized as 'winner' cells and are protected from apoptosis, while surrounding cells with lower levels are marked for elimination 1. This ancient cell recognition mechanism, originally evolved in Drosophila, is active in human cancer cells, where increased CACFD1 expression enables malignant cells to proliferate despite interaction with Lose-expressing stromal cells 1. Inhibition of CACFD1 expression reduces tumor growth and metastasis while inducing chemotherapy sensitivity 1. CACFD1 also involves vesicle-mediated transport and protein binding functions [GO annotations]. Genetically, CACFD1 variants (rs4962153, rs3094379) are implicated in shared pathways influencing both COVID-19 severity and coronary heart disease risk 2, and expression is regulated by GPSM1 genetic variants in skeletal muscle contexts 3. These findings suggest CACFD1 represents a conserved cellular competition mechanism with significant implications for cancer biology and disease susceptibility.