The metastasis suppressor NDRG1 down-regulates the epidermal growth factor receptor via a lysosomal mechanism by up-regulating mitogen-inducible gene 6

Abstract

The metastasis suppressor, N-Myc downstream-regulated gene-1 (NDRG1) inhibits a plethora of oncogenic signaling pathways by down-regulating the epidermal growth factor receptor (EGFR). Herein, we examined the mechanism involved in NDRG1-mediated EGFR down-regulation. NDRG1 overexpression potently increased the levels of mitogen-inducible gene 6 (MIG6), which inhibits EGFR and facilitates its lysosomal processing and degradation. Conversely, silencing NDRG1 in multiple human cancer cell types decreased MIG6 expression, demonstrating the regulatory role of NDRG1. Further, NDRG1 overexpression facilitated MIG6 -EGFR association in the cytoplasm, possibly explaining the significantly (p <0.001) increased half-life of MIG6 from 1.6 ؎ 0.2 h under control conditions to 7.9 ؎ 0.4 h after NDRG1 overexpression. The increased MIG6 levels enhanced EGFR co-localization with the late endosome/lysosomal marker, lysosomal-associated membrane protein 2 (LAMP2). An increase in EGFR levels after MIG6 silencing was particularly apparent when NDRG1 was overexpressed, suggesting a role for MIG6 in NDRG1-mediated down-regulation of EGFR. Silencing phosphatase and tensin homolog (PTEN), which facilitates early to late endosome maturation, decreased MIG6, and also increased EGFR levels in both the presence and absence of NDRG1 overexpression. These results suggest a role for PTEN in regulating MIG6 expression. Anti-tumor drugs of the di-2-pyridylketone thiosemicarbazone class that activate NDRG1 expression also potently increased MIG6 and induced its cytosolic co-localization with NDRG1. This was accompanied by a decrease in activated and total EGFR levels and its redistribution to late endosomes/lysosomes. In conclusion, NDRG1 promotes EGFR down-regulation through the EGFR inhibitor MIG6, which leads to late endosomal/lysosomal processing of EGFR.

Cx43 phosphorylation–mediated effects on ERK and Akt protect against ischemia reperfusion injury and alter the stability of the stress-inducible protein NDRG1

“…Like Cx43, NDRG1 migrates as multiple isoforms via SDS-PAGE, in part because of differences in phosphorylation (34,35). Although all NDRG1 isoforms are increased or decreased in the Cx43 mutants, the effects are most evident on the highmigrating isoform that is strongly recognized by the PAS antibody (Fig.…”

“…For example, NDRG1 has been reported to inhibit NF-B signaling (48), leading to downstream effects on epithelial mesenchymal transition (49,50) and angiogenesis (48). It has been shown to affect MAPK signaling through regulation of EGF receptor expression and internalization (34,51) and to stabilize adherens junctions through regulation of E-cadherin (34,52) and ␤catenin (50, 53) localization and degradation. The role of phosphorylation in regulating NDRG1 is not yet clear, although it is known to be phosphorylated by SGK, followed by GSK (54).…”

Unique targeting of androgen‐dependent and ‐independent AR signaling in prostate cancer to overcome androgen resistance

“…[5][6][7][8][9][10][11] NDRG1 also inhibits major oncogenic signaling pathways including EGFR and its downstream MAPK signaling, as well as the PI3K/AKT pathway in cancer cells. 10,12,13 Considering the role of NDRG1 in PCa, agents that can upregulate this protein could be highly efficacious against this disease. In fact, novel thiosemicarbazones, di-2-pyridyl ketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT) and di-2pyridyl ketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC; Figure 1A), which were developed in our laboratories, [14][15][16][17] markedly upregulate NDRG1 in cancer cells.…”

“…13 Subsequently, MIG6 promotes the internalization and lysosomal degradation of EGFR. 13 Hence, Dp44mT and DpC promote the degradation of critical RTK's, which impairs downstream signaling pathways such as PI3K/AKT. 11,18,21,[23][24][25] Dp44mT and DpC also bind intracellular metals following Irving William's series for transition metal complexes, with highest affinity for labile iron (Fe) and copper.…”

“…Increasing NDRG1 expression in PCa cells had several effects, including the inhibition of ( 1) proliferation; (2 ) the epithelial to mesenchymal transition (EMT), and ( 3 ) cell migration and invasion in vitro and metastasis in vivo 5‐11 . NDRG1 also inhibits major oncogenic signaling pathways including EGFR and its downstream MAPK signaling, as well as the PI3K/AKT pathway in cancer cells 10,12,13 …”