CD44 and breast cancer: We have established five breast cancer PDXs with various molecular subtypes including luminal A and B, triple-negative breast cancer (Supplemental Table 1), and identified ALDH as a BCSC marker for BC0244, BC0634, BC0350, VBC108, and CD44+CD24− as BCSC marker for BC0145 PDXs (Table 1) (22–25).