NDRG1 enhances the sensitivity to Cetuximab by promoting Stat1 ubiquitylation in colorectal cancer.

INTRODUCTION

Cetuximab (CTX) is an effective targeted drug for the treatment of metastatic colorectal cancer, but it is effective only in patients with wild-type KRAS genes. Even in this subset of patients, the sensitivity of CTX in patients with right hemi-colon cancer is much lower than that in patients with left hemi-colon cancer. This significantly limits its clinical application. Therefore, further elucidation of the underlying molecular mechanisms is needed. N-myc downstream-regulated gene 1 (NDRG1) plays an important role in solid tumor invasion and metastasis, but whether it can influence CTX sensitivity has not been thoroughly investigated.

OBJECTIVE

Our study aimed to identify a novel mechanism by which NDRG1 affects CTX sensitivity.

METHODS

Through mass spectrometry analysis of our previously constructed CTX-resistant RKO and HCT116 cells, we found that the signal transducer and activator of transcription-1 (Stat1) might be a potential target of NDRG1. By knocking out NDRG1 or/and Stat1 genes, we then applied the loss-of-function experiments to explore the regulatory relationship between NDRG1 and Stat1 and their roles in the cell cycle, epithelial-mesenchymal transition (EMT), and the sensitivity to CTX in these two colorectal cancer (CRC) cells. Finally, we used the nude-mouse transplanted tumor model and human CRC samples to verify the expression of NDRG1 and Stat1 and their impact on CTX sensitivity in vivo.

RESULTS

Stat1 was upregulated in CTX-resistant cells, whereas NDRG1 was downregulated. Mechanically, NDRG1 was inversely correlated with Stat1 expression. It suppressed CRC cell proliferation, migration, and invasion, and promoted apoptosis and epithelial-mesenchymal transition (EMT) by inhibiting Stat1. In addition, NDRG1 directly interacted with Stat1 and promoted Smurf1-induced Stat1 ubiquitination. Importantly, this novel NDRG1-dependent regulatory loop also enhanced CTX sensitivity both in vitro and in vivo.

CONCLUSION

Our study revealed that NDRG1 enhanced the sensitivity to Cetuximab by inhibiting Stat1 expression and promoting its ubiquitination in colorectal cancer, elucidating NDRG1 might be a potential therapeutic target for refractory CTX-resistant CRC tumors. But its clinical value still needs to be validated in a larger sample size as well as a different genetic background.