The prostate metastasis suppressor gene NDRG1 differentially regulates cell motility and invasion

Abstract

Experimental and clinical evidence suggests that N‐myc downregulated gene 1 (NDRG1) functions as a suppressor of prostate cancer metastasis. Elucidating pathways that drive survival and invasiveness of NDRG1‐deficient prostate cancer cells can help in designing therapeutics to target metastatic prostate cancer cells. However, the molecular mechanisms that lead NDRG1‐deficient prostate cancer cells to increased invasiveness remain largely unknown. In this study, we demonstrate that NDRG1‐deficient prostate tumors have decreased integrin expression and reduced cell adhesion and motility. Our data indicate that loss of NDRG1 differentially affects Rho GTPases. Specifically, there is a downregulation of active RhoA and Rac1 GTPases with a concomitant upregulation of active Cdc42 in NDRG1‐deficient cells. Live cell imaging using a fluorescent sensor that binds to polymerized actin revealed that NDRG1‐deficient cells have restricted actin dynamics, thereby affecting cell migration. These cellular and molecular characteristics are in sharp contrast to what is expected after loss of a metastasis suppressor. We further demonstrate that NDRG1‐deficient cells have increased resistance to anoikis and increased invasiveness which is independent of its elevated Cdc42 activity. Furthermore, NDRG1 regulates expression and glycosylation of EMMPRIN, a master regulator of matrix metalloproteases. NDRG1 deficiency leads to an increase in EMMPRIN expression with a concomitant increase in matrix metalloproteases and thus invadopodial activity. Using a three‐dimensional invasion assay and an in vivo metastasis assay for human prostate xenografts, we demonstrate that NDRG1‐deficient prostate cancer cells exhibit a collective invasion phenotype and are highly invasive. Thus, our findings provide novel insights suggesting that loss of NDRG1 leads to a decrease in actin‐mediated cellular motility but an increase in cellular invasion, resulting in increased tumor dissemination which positively impacts metastatic outcome.

Eukaryotic elongation factor 2 kinase upregulates the expression of proteins implicated in cell migration and cancer cell metastasis

“…A recent in vitro study reported several novel eEF2K substrates; 36 among them, NDRG1 is implicated in cancer cell invasion and metastasis and was reported to be phosphorylated by eEF2K on Thr346, Thr356 and/or Thr366. [37][38][39][40] However, we were unable to detect any phosphorylation of NDRG1 by eEF2K in vitro or on the phosphorylation of NDRG1 in cells (Supporting Information Figs. S12 and S13).…”

Identification of PIM1 substrates reveals a role for NDRG1 in prostate cancer cellular migration and invasion

“…Additionally, overexpression of NDRG1 reduces metastasis in a rodent model of prostate cancer 49 . In contrast, prostate cancer cells with low NDRG1 expression display increased motility and invasiveness 45 , and reduced expression of NDRG1 was associated with poor overall survival in a variety of cancers, including prostate 50 . NDRG1 is transcriptionally regulated by the androgen receptor 51 .…”

“…We focused on characterizing the effect of PIM1-dependent serine 330 phosphorylation (pS330) of NDRG1, given that a phosphoproteomic analyses of prostate cancer tissues by Drake et al demonstrated that levels of NDRG1 pS330 were found to be 7.7 times higher in metastatic lesions than in localized prostate cancer 43 (Sup Table 5). Although several studies have implicated NDRG1 in prostate cancer 44,45 , a link between PIM1 and NDRG1 has not been established. NDRG1 is a member of the alpha/beta hydrolase superfamily, but does not possess catalytic activity 46 .…”

“…NDRG1 regulates the expression of the membrane protein KAI1 (CD82), which interacts with adjacent cells via the membrane protein gp-Fγ to inhibit metastasis 57 . Moreover, NDRG1 expression in HepG2 cells leads to increased membrane-localized beta-catenin, which promotes a less migratory phenotype and greater cell-cell contact 45 . In light of these findings, and given the previously demonstrated ability of PIM1 to promote cell migration and invasion 58,59 , we investigated the effect of NDRG1 phosphorylation on the migration and invasion of prostate cancer cells.…”

Differential role of PTEN in transforming growth factor β (TGF‐β) effects on proliferation and migration in prostate cancer cells

“…Of these molecular mechanisms, tumor suppressor genes, which normally inhibit cell growth and prevent tumor formation, become functionally inactive in cancer cells through various mechanisms in the process of tumorigenesis. Insights into the molecular function of tumor suppressors could aid in understanding pathways and barriers that prevent the process of tumor progression . Phosphatase and tensin homolog ( PTEN ), a tumor suppressor gene, is frequently mutated in a variety of human cancers including prostate cancer .…”