GSCs showed characteristics consistent with cancer stem cells: namely, neurosphere formation (Figure S1A, Supporting Information); expression of stem cell markers Sox2 and OLIG2 (Figure S1B,D, Supporting Information) and multilineage differentiation with markers for astrocytes (GFAP), neurons (MAP2) or oligodendrocytes (O4) (Figure S1E, Supporting Information). Here, IGKV1D-37 is linked to cancer.