Nucleoside transporters (NTs) mediate the uptake of
nucleosides and nucleobases across the plasma membrane, mostly for salvage purposes. The canonical NTs belong to two gene families, SLC29 and SLC28. The former encode equilibrative
nucleoside transporter proteins (ENTs), which mediate the facilitative diffusion of natural
nucleosides with broad selectivity, whereas the latter encode concentrative
nucleoside transporters (CNTs), which are
sodium-coupled and show high affinity for substrates with variable selectivity. These
proteins are expressed in most cell types, exhibiting apparent functional redundancy. This might indicate that CNTs have specific roles in the physiology of the cell beyond
nucleoside salvage. Here, we addressed this possibility using adenoviral vectors to restore
tumor cell expression of hCNT1 or a polymorphic variant (hCNT1S546P) lacking
nucleoside translocation ability. We found that hCNT1 restoration in
pancreatic cancer cells significantly altered cell-cycle progression and phosphorylation status of key signal-transducing
kinases, promoted
poly-(ADP-ribose) polymerase hyperactivation and cell death and reduced cell migration. Importantly, the translocation-defective transporter triggered these same effects on cell physiology. Moreover, this study also shows that restoration of hCNT1 expression is able to reduce
tumor growth in a mouse model of pancreatic
adenocarcinoma. These data predict a novel role for a NT
protein, hCNT1, which appears to be independent of its role as mediator of
nucleoside uptake by cells. Thereby, hCNT1 fits the profile of a transceptor in a substrate translocation-independent manner and is likely to be relevant to
tumor biology.