SIGLEC9 and neoplasm: Former studies of SIGLEC family genes in tumors were mainly about their functional roles on immune cell populations, facilitating tumor growth, and immune escape in different cancer types, such as inhibitory SIGLEC9 and SIGLEC7 expressed on natural killer cells, or SIGLEC6 expressed on mast cells in colorectal cancer, which could be exploited by tumor cells through increased sialylation and glycosylation (7, 35–41).