Exploitation of the UDP-glucose hydrolase NUDT22 as novel target in cancer therapy

NUDT22 is a hitherto unstudied family member of the NUDIX protein superfamily. Our group previously identified a specific substrate activity for NUDT22 towards uridine diphosphate (UDP)-glucose resulting in the generation of glucose 1-phosphate (G1P) and the pyrimidine precursor uridine monophosphate (UMP). Fast proliferating cells such as cancer cells can adapt the more energy-efficient nucleoside salvage pathways to maintain sufficient nucleotide pool levels for cell proliferation and to prevent DNA replication stress. Together with the observed NUDT22 expression alterations in cancer, we hypothesised a specific role of NUDT22 in nucleotide synthesis and the potential exploitation of NUDT22 as novel target in cancer therapy.

Here, we assessed the effects of NUDT22 knockout in osteosarcoma U2OS, noncancer retinal pigment epithelial hTERT-RPE1, and in breast cancer MCF7 cells on cell proliferation, nucleotide levels, DNA replication stress, DNA damage induction, DNA replication fork speed and cell cycle progression. We determined synergistic changes in cell survival, DNA damage induction and cell cycle progression upon targeting pyrimidine de novo synthesis with nucleoside analogues and other anticancer agents in NUDT22 KO cells and their respective controls. We performed gene expression database analysis of the cancer genome atlas (TCGA) as well as genotype-tissue expression (GTEx) program to assess changes in NUDT22 levels in cancer versus healthy tissue and determined the role of NUDT22 as potential cancer target in vitro and in a MCF7 breast cancer xenograft model. Furthermore, we exploited our group’s previously solved co-crystal structure of NUDT22 in complex
with UDP-glucose in virtual screens for the development of NUDT22 inhibitors. The identified and chemically optimised compounds were further evaluated based on enzymatic and cellular activity as well as their target engagement with recombinant protein and in cell lysate.

In conclusion, we propose the discovery of a novel pyrimidine salvage pathway through NUDT22 controlling pyrimidine levels for DNA replication stress prevention and cancer growth maintenance. Our in vitro and in vivo findings suggest that NUDT22 is an emerging target for cancer therapy. In addition, we identified potential first-in-class NUDT22 inhibitors that engage their target in both recombinant protein and cell lysate.