Differential expression of cytokines and receptor expression during anoxic growth

Cell density in tumor cell three dimensional (3D) cultures affects secretome expression of components. A microenvironment characteristic shared by high-density 3D cell culture and in vivo tumor masses is poor oxygenation, with anoxia being a natural cell state in tumor centers. Until recently, the ability to study anoxia-adapted cell physiology was not possible. Using a newly-developed methodology, anoxic HeLa cell secretome expression was measured.

Anoxic HeLa cell cytokine levels after 3 days' (hypoxia inducible factor, HIF1 positive) and 10 days' growth (HIF1 negative; anaerobic respiration) were significantly (p < 0.01) higher than normoxic controls for: IL-8 (1.8- and 3.4-fold higher, respectively), GRO (1.3- and 1.1-fold higher, respectively), and IL-11 (1.4- and 1.1-fold higher, respectively). In contrast, G-CSF, IFNα2, and CXCL-10 levels decreased over time (day 3 vs. day 10). Thus, metabolically active HeLa cells respond to the lack of oxygen, in part, by regulating the levels of cytokines produced. Cytokines expressed at increased levels, in the absence of oxygen, correspond to a secretomic profile reported for paracrine signaling pathways associated with metastasis. Further studies defining physiologic changes that occur upon anoxic growth may lead to the discovery of novel chemotherapeutic drug targets.