This result was also validated by utilizing NK cells derived from peripheral blood mononuclear cells (PBMC) as the killer source, where cells positive in CD45 and NKp46 could efficiently penetrate tumor cells to form CIC structures (Fig. 5g) and killed tumor cells in a CD44-dependent way that was associated with CIC formation (Fig. 5h–k). The gene discussed is CD44; the disease is neoplasm.