ADA and cancer: The dominant population of human cells that was responsible for the origin of ADA2 were monocytes/macrophages (Figure 7G), but also less aggressive cancer cells (MCF‐7) showed slight activity of ADA2 (Figure 7C).The remaining ADA1 activity inside the cells and the entire eADA activity in analysed human cells were catalysed by ADA1 (Figure 7C‐G).