77P - Deciphering the regulation of the metastasis suppressor, NDRG1 in different cancer-types and its functional implications

Abstract

Background

The metastasis suppressor, N-myc Downstream Regulated Gene-1 (NDRG1) inhibits metastasis in a variety of cancer-types, including cancers of the breast, colon, pancreas and prostate. Its potent anti-oncogenic effects were demonstrated in multiple in vitro and in vivo studies, making it a promising therapeutic target. However, exactly how NDRG1 is regulated in different cancer-types and how different regulatory mechanisms affect NDRG1 function remain to be elucidated. Notably, post-translational modifications (PTMs), phosphorylation and cleavage of NDRG1, have been associated with its function. Therefore, it was crucial to examine whether these PTMs occur universally or selectively in different cancer-types. Further, considering the DNA repair role suggested for nuclear NDRG1, the effects of the above PTMs on nuclear NDRG1 levels was examined.

Methods

DU145 and PC3 prostate cancer cells, PANC-1 pancreatic cancer cells, HT-29 colon cancer cells, HepG2 and Hep3B hepatocellular carcinoma (HCC) cells were utilised. Full-length (FL) and truncated (T) NDRG1 isoforms were detected using a C-terminus directed antibody. The FL isoform was detected using an N-terminus directed antibody. Ser330 or Thr346 phosphorylation (p-NDRG1) was detected using specific antibodies.

Results

For the first time, we demonstrated that phosphorylation and potential cleavage of the NDRG1 protein occurs in all the various cancer cell-types examined. Although the levels varied, both the FL and T NDRG1 and its phosphorylated form were detected in all tumour cells assessed. The FL NDRG1 isoform was predominantly found in the cell nucleus. Ser330 p-NDRG1 was also highly localised in the cell nucleus, while Thr346 p-NDRG1 was mostly cytoplasmic. These cellular distribution patterns were similar in all cancer-types tested.

Conclusions

This study demonstrates for the first time that the NDRG1 protein is phosphorylated and potentially cleaved in diverse cancer cell-types. Further, FL NDRG1 and Ser330 p-NDRG1 were highly localised to the cell nucleus. These results indicate that the N-terminus region and phosphorylation at Ser330 could be crucial for nuclear expression and the well-known anti-metastatic function of NDRG1.

Clinical trial identification

Legal entity responsible for the study

The University of Sydney

Funding

The University of Sydney, Cancer Institute New South Wales National Health and Medical Research Council, Cancer Australia, Cure Cancer Australia Foundation.

Disclosure

All authors have declared no conflicts of interest.