CD44+ cells persist and proliferate in recurrent tumors when PDAC becomes resistant to chemotherapeutic agents Maria Inés Molejon et al. designed an experiment for recurrent PDAC in which targeting CD44 surface antigen eliminated the remaining tumor cells in vivo after gemcitabine treatment in a PDAC-derived xenograft model (Molejon et al., 2015). Here, CD44 is linked to neoplasm.