CXCL8 and renal cell carcinoma: On the other hand, VHL-deficient RCC cells exposed to normoxic conditions expressed IL-6 and IL-8 at very low levels (Figs. 1C–F) and unlike HK2 cells, hypoxic conditions resulted in a significant increase of IL-6 and IL-8 production starting at 180′ and steadily increasing to 4–5 fold by 72 hours (Figs. 1 C–F).