An extraordinarily high level of IL-15 expression by a cell line transduced with a modified BMGneo vector displays hypoxic upregulation.

Interleukin (IL)-15 expression level is tightly controlled in mammalian cells by various mechanisms. In order to achieve higher expression levels of IL-15, many attempts have been made, but the highest expression rate among those reported is still only 13.3 ng/106 cells/24 h. Here we report that a selected human embryonic kidney 293 (HEK293) cell line, denoted 293HAN cells, which can survive and proliferate under conditions of hypoxia, acidity, and nutritional depletion (HAN), after transduction -- with a modified BMGneo vector -- can produce functional human IL-15 at the extremely high rate of 890 ng/106 cells/24 h under normoxic conditions -- a 67-fold increase. This is as a result of multiple episomally based vector copy numbers per cell. An extra benefit was that the BMGneo vector was found to be inducible in hypoxia and allowed a further approximately threefold upregulation of the human IL-15 level which made these 293HAN cells, transduced with the modified BMGneo vector, a very promising tool for high IL-15 production (approximately 200-fold increase above that of baseline normoxia). The mechanism of hypoxic upregulation was found to be related to the mouse MT-1 promoter present in the vector.