The present invention pertains to a method for the in-vitro or ex-vivo expansion of immune cells using a histone acetyl transferase (HAT) modulator as additive in the cell culture medium during the expansion procedure. Immune cells such as natural killer (NK) cells, T cells or cytokine induced killer (CIK) cells are used in adoptive cell therapies for the injection into patients suffering from malignant cancer diseases such as leukemia. Cells expanded using the method of the invention were superior proliferative and viable. Further provided by the invention is a cell culture medium comprising the HAT modulator of the invention as well as cell populations obtained using the method of the invention.
