Expression of ADK-S and ADK-L Isoforms and Their Association with CD39/CD73/A2aR in Colorectal Cancer

The level of mRNA of the long (L) and short (S) isoforms of adenosine kinase (ADK) was analyzed in patients with colorectal cancer (CRC). ADK is required to convert adenosine (ADO) to AMP. It was shown that tumor and normal colon tissues (n=13) do not differ in the level of ADK-S and ADK-L mRNA. At the same time, the level of ADK-S mRNA (tumor: p=0.0214, normal: p=0.005) in the colon tissue was lower than in the blood of CRC patients (n=20), and the level of ADK-L mRNA (tumor: p=0.007, normal: p=0.024), on the contrary, was higher. A negative correlation was found between the level of ADK-S mRNA and the level of A2aR mRNA in both tumor and normal tissues (p=0.018 and p=0.0014, respectively). In the tumor tissue, a positive correlation was shown between ADK-L and CD73 mRNA levels (p=0.017). The obtained data indicate the association ADK with the expression of CD39/CD73/A2aR in CRC patients. In this regard, the effect of recombinant ADK on the expression of CD39 and CD73 ectonucleotidase by T cells in vitro was analyzed. In a culture of peripheral blood mononuclear cells isolated from the blood of 5 healthy donors, ADK did not abolish the inhibitory effect on the expression of CD39 and CD73 by CD8⁺T cells in the presence of a high concentration of ATP (a source for ADO). Effects on CD39⁺CD4⁺, CD73⁺CD4⁺T cells and CD39⁺ Treg cells were also not found.