In our studies, the induction of hypoxia in WM115 and WM266-4 melanoma cells during culture was confirmed by increasing the mRNA as well as protein levels of carbonic anhydrase IX, and additionally by increasing the mRNA level of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4 (Figure 1A,B and Figure 2A,B), which was also reported previously by Trojan et al. [44]. The gene discussed is CA9; the disease is melanoma.