The Development and Characterization of an HEK293-Derived Cell Line for Use in an Intratumoral Cytokine Delivery System

As part of ongoing work to develop a method of cytokine delivery for use as an intratumoral depot, we noted that HEK293 cells, encapsulated in alginate, died within 24–48 h after in vivo, intratumoral implantation. We hypothesized that the highly hypoxic and acidic conditions found inside the tumor was the cause of the cells' premature demise. Therefore, we set out to develop a cell line, derived from HEK293, that would survive these hostile conditions. The HEK293 line was selected in 0.3–0.5% oxygen conditions over several weeks, followed by a further 6-week period of culture in alternating hypoxic and normoxic conditions. The most rapidly growing clones were selected and grown in normoxic conditions for several weeks to ensure their stability. The clones were then compared to the original line in terms of cell proliferation in normoxia and hypoxia, colony-forming efficiency, and morphological characteristics. The resulting line was able to proliferate in the harshest of conditions and continues to release its biological payload after alginate microencapsulation.