NDRG2 facilitates colorectal cancer differentiation through the regulation of Skp2-p21/p27 axis

Abstract

Poorly differentiated colorectal cancers (CRCs) are more aggressive and lack targeted therapies. We and others previously reported the predominant role of tumor-suppressor NDRG2 in promoting CRC differentiation, but the underlying mechanism is largely unknown. Herein, we demonstrate that NDRG2 induction of CRC cell differentiation is dependent on the repression of E3 ligase Skp2 activity. In patients and Ndrg2 knockout mice, NDRG2 and Skp2 are negatively correlated and associated with cell differentiation stage. Further, NDRG2 suppression of Skp2 contributes to the inductions and stabilizations of p21 and p27, which are Skp2 target proteins for degradation. The reduction of either p21 or p27 levels by shRNA can decrease NDRG2-induced AKP activity and resume cell growth inhibition, thus both p21 and p27 are required for NDRG2 effect on the promotion of cell differentiation in CRCs. The mechanistic study shows that NDRG2 suppresses β-catenin nuclear translocation and decreases the occupancy of β-catenin/TCF complex on Skp2 promoter, potentially through dephosphorylating GSK-3β. By subjecting a series of NDRG2 deletion mutants to Skp2 expression, the loss of NH2-terminal domain can completely abolish NDRG2-dependent differentiation induction. Supporting the biological significance of the reciprocal relationship between NDRG2 and Skp2, an NDRG2low/Skp2high gene expression signature correlates with poor CRC patient outcome and could be considered as a diagnostic marker of CRCs.

NDRG2 Regulates Adherens Junction Integrity to Restrict Colitis and Tumorigenesis

“…The aforementioned results prompted us to uncover how Ndrg2 loss caused the transcriptional repression of E-cadherin. However, the current studies didn’t support the concept of NDRG2 as a transcriptional regulator per se[9, 17, 18]. It’s reasonable for us to further analyze whether Ndrg2 deficiency alters the expression of key transcriptional regulators of E-cadherin, such as Snail, Slug and ZEB1/2 etc[19, 20].…”

“…We further confirmed the alteration of Snail and E-cadherin in human colorectal cancer cells with NDRG2 knockdown (Supplementary figure 6A, B). Nextly, by subjecting different FLAG-tagged NDRG2 truncations (figure 5B, right panel)[9], we found Snail expression was significantly decreased with full length NDRG2 (NDRG2/FL), but obviously abolished by NDRG2 N-terminal deletion (NDRG2/ΔN) (figure 5B, left panel), suggesting the key role of N-terminal of NDRG2 for Snail regulation. With chase assay of protein stability, we noticed NDRG2/FL could obviously shorten the half-life of Snail protein (figure 5C, D).…”

“…We previously identified N-myc downstream regulated gene 2 (NDRG2) as a novel tumor suppressor gene that played a role in regulating the proliferation, differentiation and metastasis of multiple types of malignant tumors[7, 8]. Notably, our recent data showed that NDRG2 could inhibit colorectal cancer cell proliferation and promote cell differentiation[9]. Moreover, we found that decreased NDRG2 expression was a powerful and independent predictor of a poor prognosis in colorectal cancer[10, 11].…”

Truncated TEAD‐binding protein of TAZ inhibits glioma survival through the induction of apoptosis and repression of epithelial‐mesenchymal transition

“…Immunohistochemistry (IHC) was performed using as previously described. 14 The sections were deparaffinized and dehydrated by xylene and alcohol, respectively, and then treated with 0.5% H 2 O 2 for the blockage of endogenous peroxidase. For immunohistochemical analysis, sections were stained with TAZ antibody (1:200, ab84927; Abcam) and evaluated.…”

N-Myc Downstream-Regulated Gene 2 (NDRG2) as a Novel Tumor Suppressor in Multiple Human Cancers

“…Moreover, NDRG2-deficient mice show spontaneous development of various tumor types, including T-cell lymphomas, providing in vivo evidence that NDRG2 functions as a tumor suppressor gene. We believe that NDRG2 is a novel tumor suppressor and might be a therapeutic target for cancer treatment.Genes and Cancer 2 carcinoma cells [8]. Moreover, NDRG2-deficient mice show spontaneous development of various tumor types, providing in vivo evidence that NDRG2 functions as a tumor suppressor gene.…”