To elucidate the biological characteristics and adaptive evolution of sika deer, the gene families between sika deer and aforementioned 13 other mammals were analyzed, revealing that 378 significantly expanded gene families were functionally related to signal transduction (Hippo signaling pathway, PI3K-AKT signaling pathway, and calcium signaling pathway), cell growth and death (cell cycle and apoptosis), and pathways in cancer (Table S14). The gene discussed is AKT1; the disease is cancer.