Further, these cells were positive for CD44 and CD326 (Figure 3F), well‐known cancer stem cell markers,[19] and exhibited an increasing proportion of SP (Figure S4A, Supporting Information) and tumorigenesis with sorted CD326+ cells for serial transplantation (Figure 3G–I), which could differentiate into both CD326‐ cancer cells and CD31+ vascular endothelial cells (Figure S4C,D, Supporting Information). Here, PECAM1 is linked to cancer.