Natural Killer (NK) cells and NK cell lines are modified to increase cytotoxicity, wherein the cells and compositions thereof have a use in the treatment of cancer. Modified NK cells and NK cell lines are produced via genetic modification of CD38low NK cells to transiently express the Fc receptor CD16 (F158V) from mRNA introduced into the NK cell, rather than from a chromosomal coding sequence. The cytotoxicity of the modified NK cells against CD38-expressing cancer cells is increased by administration of these modified cells in combination with a CD38-binding antibody. Separately, cytotoxicity against breast cancer is exhibited by the modified NK cells in combination withHerceptin.
