Human equilibrative nucleoside transporter 1 (hENT1) expression correlates with gemcitabine uptake and cytotoxicity in mantle cell lymphoma (MCL)

2348 Nucleoside transporters (NTs) might play a relevant role in the intracellular targeting of many nucleoside analogues used in anticancer therapy. Two gene families (SLC28 and SLC29) encode the two types of human NTs, Concentrative Nucleoside Transporter (CNT) and Equilibrative Nucleoside Transporter (ENT) proteins. We have previously described that chronic lymphocytic leukemia (CLL) cells express both SLC28- and SLC29- related mRNAs, although transport function seems to be mostly related to ENT-type transporters. In this study we have analyzed the role of ENTs in nucleoside-derived drug bioavailability and action in mantle cell lymphoma (MCL) cells. We have analyzed the expression of hENT1 and hENT2 by real time RT-PCR and by Western Blot, using polyclonal antibodies against hENT1 and hENT2 in five MCL cell lines and 20 primary MCL cells. High levels of hENT1 protein expression (0.15 ± 0.14) in MCL cells were detected in contrast to hENT1 expression in CLL cells (0.08 ± 0.02), and a good correlation was found between protein and mRNA levels of hENT1 ( p= 0.03 ), thus indirectly suggesting that hENT1 might be transcriptionally regulated in MCL cells. Uridine transport significantly correlated with hENT1 -related mRNA expression and protein levels ( p = 0.009 and 0.042 , respectively). Similar results were obtained for gemcitabine transport ( p = 0.036 and p = 0.013 , respectively), but no correlation was found for fludarabine uptake. Unless the doses of gemcitabine to induce a cytototxic effect in primary MCL cells (LD 50 50 hENT1 mRNA and protein amounts, drug uptake and sensitivity to gemcitabine was also observed ( p ). These results further support the hypothesis that nucleoside transporters are implicated in the therapeutic response to nucleoside analogues, suggesting that hENT1 expression might be useful to predict response to nucleoside analogues known to be taken up via ENT1 carriers, such as gemcitabine in MCL patients.