# Suppression of Ehrlich ascites tumor cell proliferation via G1 arrest induced by dietary nucleic acid-derived nucleosides

## TL;DR

This study shows that nucleosides from dietary nucleic acids can stop cancer cell growth by causing G1 phase arrest in the cell cycle.

## Contribution

The novel finding is that guanosine and 2’-deoxyguanosine induce G1 arrest via C/EBPβ activation in Ehrlich ascites tumor cells.

## Key findings

- RNA and DNA hydrolysate show anti-proliferative effects in mouse and in vitro models.
- Guanosine and 2’-deoxyguanosine inhibit cancer cell progression from G1 to S phase.
- C/EBPβ is activated and translocates to the nucleus in response to these nucleosides.

## Abstract

The nucleic acids found in food play a crucial role in maintaining various bodily functions. This study investigated the potential anticancer effects of dietary nucleic acids, an area that is still not fully understood. By utilizing an in vivo mouse model and an in vitro cell model, we discovered an anti-proliferative impact of RNA in both systems. DNA exhibited anti-proliferative effects in the mouse model, while this phenomenon wasn’t observed in the in vitro cell model using Ehrlich ascites tumor (EAT) cells. Conversely, DNA hydrolysate demonstrated distinct anti-proliferative effects in EAT cells, suggesting that nucleotides or nucleosides generated during nucleic acid digestion act as active constituents. Furthermore, we examined various nucleosides and two sodium-independent equilibrative nucleoside transporter inhibitors (ENTs), identifying guanosine and 2’-deoxyguanosine as pivotal in the anti-proliferative effect. We also found that the anti-proliferation activity with both nucleosides was suppressed by the treatment of dipyridamole, a non-selective inhibitor for ENT1 and ENT2, but not nitrobenzylthioinosine, a low inhibitor for ENT2. The uptake of these compounds into cells is likely facilitated by ENT2. These nucleotides impeded the progression of cancer cells from the G1 phase to the S phase in the cell cycle. Another significant finding is the increased expression of CCAAT/enhancer-binding protein (C/EBPβ) induced by guanosine and 2’-deoxyguanosine. Furthermore, immunostaining revealed that C/EBPβ diffuses into the nucleus, indicating its presence. This suggests that guanosine or 2-deoxyguanosine induces G1 arrest in cancer cells via the activation of C/EBPβ. Encouraged by these promising results, guanosine and 2’-deoxyguanosine show potential applications in cancer prevention.