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The proto-oncogene c-Src and its downstream signaling pathways are inhibited by the metastasis suppressor, NDRG1.

Liu W, Yue F, Zheng M, Merlot A, Bae DH, Huang M, Lane D, Jansson P, Lui GY, Richardson V, Sahni S, Kalinowski D, Kovacevic Z, Richardson DR - Oncotarget (2015)

Bottom Line: Moreover, NDRG1 suppressed Rac1 activity by modulating phosphorylation of a c-Src downstream effector, p130Cas, and its association with CrkII, which acts as a "molecular switch" to activate Rac1.Hence, the role of NDRG1 in decreasing cell migration is, in part, due to its inhibition of c-Src activation.In addition, novel pharmacological agents, which induce NDRG1 expression and are currently under development as anti-metastatic agents, markedly increase NDRG1 and decrease c-Src activation.

View Article: PubMed Central - PubMed

Affiliation: Department of General Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, P.R.China.

ABSTRACT
N-myc downstream regulated gene-1 (NDRG1) is a potent metastasis suppressor that plays a key role in regulating signaling pathways involved in mediating cancer cell invasion and migration, including those derived from prostate, colon, etc. However, the mechanisms and molecular targets through which NDRG1 reduces cancer cell invasion and migration, leading to inhibition of cancer metastasis, are not fully elucidated. In this investigation, using NDRG1 over-expression models in three tumor cell-types (namely, DU145, PC3MM and HT29) and also NDRG1 silencing in DU145 and HT29 cells, we reveal that NDRG1 decreases phosphorylation of a key proto-oncogene, cellular Src (c-Src), at a well-characterized activating site (Tyr416). NDRG1-mediated down-regulation of EGFR expression and activation were responsible for the decreased phosphorylation of c-Src (Tyr416). Indeed, NDRG1 prevented recruitment of c-Src to EGFR and c-Src activation. Moreover, NDRG1 suppressed Rac1 activity by modulating phosphorylation of a c-Src downstream effector, p130Cas, and its association with CrkII, which acts as a "molecular switch" to activate Rac1. NDRG1 also affected another signaling molecule involved in modulating Rac1 signaling, c-Abl, which then inhibited CrkII phosphorylation. Silencing NDRG1 increased cell migration relative to the control and inhibition of c-Src signaling using siRNA, or a pharmacological inhibitor (SU6656), prevented this increase. Hence, the role of NDRG1 in decreasing cell migration is, in part, due to its inhibition of c-Src activation. In addition, novel pharmacological agents, which induce NDRG1 expression and are currently under development as anti-metastatic agents, markedly increase NDRG1 and decrease c-Src activation. This study leads to important insights into the mechanism involved in inhibiting metastasis by NDRG1 and how to target these pathways with novel therapeutics.

No MeSH data available.


Related in: MedlinePlus

Schematic diagram illustrating the c-Src signaling pathway assessed herein (A) and immunoblots revealed that NDRG1 expression inhibited c-Src phosphorylation (Tyr416) in DU145 cells (B) and HT29 cells (C)(B, C) Whole-cell lysates were prepared, and immunoblotting was performed to determine the effect of NDRG1 expression on levels of phosphorylated (p-) c-Src (p-Src(Tyr416) and p-Src(Tyr527)) and total c-Src compared to that of the relative control cells (vector control and sh-control). Blots are representative of 3–5 experiments. Densitometric analysis is expressed relative to the β-actin loading control. Data show the mean ± S.D. (3–5 experiments); *p < 0.05; **p < 0.01; ***p < 0.001, relative to vector control or sh-control cells, as appropriate.
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Figure 1: Schematic diagram illustrating the c-Src signaling pathway assessed herein (A) and immunoblots revealed that NDRG1 expression inhibited c-Src phosphorylation (Tyr416) in DU145 cells (B) and HT29 cells (C)(B, C) Whole-cell lysates were prepared, and immunoblotting was performed to determine the effect of NDRG1 expression on levels of phosphorylated (p-) c-Src (p-Src(Tyr416) and p-Src(Tyr527)) and total c-Src compared to that of the relative control cells (vector control and sh-control). Blots are representative of 3–5 experiments. Densitometric analysis is expressed relative to the β-actin loading control. Data show the mean ± S.D. (3–5 experiments); *p < 0.05; **p < 0.01; ***p < 0.001, relative to vector control or sh-control cells, as appropriate.

Mentions: The phosphorylation and activation of p130Cas is one of the key initial events in downstream c-Src signaling (Figure 1A) [11]. Interestingly, phosphorylation of p130Cas promotes its binding to CrkII, which subsequently recruits DOCK180, leading to the activation of the Rho family GTPase, Ras-related C3 botulinum toxin substrate 1 (Rac1; Figure 1A) [12, 13]. Additionally, c-Src can also activate c-Abl, which plays an important role in regulating cell motility in response to PDGF [14]. In fact, c-Abl interacts with and phosphorylates CrkII at Tyr221, which is required for Rac1 signaling activation that is involved in cytoskeleton dynamics, adhesion and cell migration (Figure 1A) [15, 16]. Rac1 plays a crucial role in regulating cancer cell motility by virtue of cycling between inactive GDP-bound and active GTP-bound forms (i.e., GTP-Rac1) [17]. Aberrant Rac1 activation associated with c-Src activation, contributes to the development and progression of a variety of cancers, and is accompanied with poor prognosis, cancer invasion and metastasis [18].


The proto-oncogene c-Src and its downstream signaling pathways are inhibited by the metastasis suppressor, NDRG1.

Liu W, Yue F, Zheng M, Merlot A, Bae DH, Huang M, Lane D, Jansson P, Lui GY, Richardson V, Sahni S, Kalinowski D, Kovacevic Z, Richardson DR - Oncotarget (2015)

Schematic diagram illustrating the c-Src signaling pathway assessed herein (A) and immunoblots revealed that NDRG1 expression inhibited c-Src phosphorylation (Tyr416) in DU145 cells (B) and HT29 cells (C)(B, C) Whole-cell lysates were prepared, and immunoblotting was performed to determine the effect of NDRG1 expression on levels of phosphorylated (p-) c-Src (p-Src(Tyr416) and p-Src(Tyr527)) and total c-Src compared to that of the relative control cells (vector control and sh-control). Blots are representative of 3–5 experiments. Densitometric analysis is expressed relative to the β-actin loading control. Data show the mean ± S.D. (3–5 experiments); *p < 0.05; **p < 0.01; ***p < 0.001, relative to vector control or sh-control cells, as appropriate.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496188&req=5

Figure 1: Schematic diagram illustrating the c-Src signaling pathway assessed herein (A) and immunoblots revealed that NDRG1 expression inhibited c-Src phosphorylation (Tyr416) in DU145 cells (B) and HT29 cells (C)(B, C) Whole-cell lysates were prepared, and immunoblotting was performed to determine the effect of NDRG1 expression on levels of phosphorylated (p-) c-Src (p-Src(Tyr416) and p-Src(Tyr527)) and total c-Src compared to that of the relative control cells (vector control and sh-control). Blots are representative of 3–5 experiments. Densitometric analysis is expressed relative to the β-actin loading control. Data show the mean ± S.D. (3–5 experiments); *p < 0.05; **p < 0.01; ***p < 0.001, relative to vector control or sh-control cells, as appropriate.
Mentions: The phosphorylation and activation of p130Cas is one of the key initial events in downstream c-Src signaling (Figure 1A) [11]. Interestingly, phosphorylation of p130Cas promotes its binding to CrkII, which subsequently recruits DOCK180, leading to the activation of the Rho family GTPase, Ras-related C3 botulinum toxin substrate 1 (Rac1; Figure 1A) [12, 13]. Additionally, c-Src can also activate c-Abl, which plays an important role in regulating cell motility in response to PDGF [14]. In fact, c-Abl interacts with and phosphorylates CrkII at Tyr221, which is required for Rac1 signaling activation that is involved in cytoskeleton dynamics, adhesion and cell migration (Figure 1A) [15, 16]. Rac1 plays a crucial role in regulating cancer cell motility by virtue of cycling between inactive GDP-bound and active GTP-bound forms (i.e., GTP-Rac1) [17]. Aberrant Rac1 activation associated with c-Src activation, contributes to the development and progression of a variety of cancers, and is accompanied with poor prognosis, cancer invasion and metastasis [18].

Bottom Line: Moreover, NDRG1 suppressed Rac1 activity by modulating phosphorylation of a c-Src downstream effector, p130Cas, and its association with CrkII, which acts as a "molecular switch" to activate Rac1.Hence, the role of NDRG1 in decreasing cell migration is, in part, due to its inhibition of c-Src activation.In addition, novel pharmacological agents, which induce NDRG1 expression and are currently under development as anti-metastatic agents, markedly increase NDRG1 and decrease c-Src activation.

View Article: PubMed Central - PubMed

Affiliation: Department of General Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, P.R.China.

ABSTRACT
N-myc downstream regulated gene-1 (NDRG1) is a potent metastasis suppressor that plays a key role in regulating signaling pathways involved in mediating cancer cell invasion and migration, including those derived from prostate, colon, etc. However, the mechanisms and molecular targets through which NDRG1 reduces cancer cell invasion and migration, leading to inhibition of cancer metastasis, are not fully elucidated. In this investigation, using NDRG1 over-expression models in three tumor cell-types (namely, DU145, PC3MM and HT29) and also NDRG1 silencing in DU145 and HT29 cells, we reveal that NDRG1 decreases phosphorylation of a key proto-oncogene, cellular Src (c-Src), at a well-characterized activating site (Tyr416). NDRG1-mediated down-regulation of EGFR expression and activation were responsible for the decreased phosphorylation of c-Src (Tyr416). Indeed, NDRG1 prevented recruitment of c-Src to EGFR and c-Src activation. Moreover, NDRG1 suppressed Rac1 activity by modulating phosphorylation of a c-Src downstream effector, p130Cas, and its association with CrkII, which acts as a "molecular switch" to activate Rac1. NDRG1 also affected another signaling molecule involved in modulating Rac1 signaling, c-Abl, which then inhibited CrkII phosphorylation. Silencing NDRG1 increased cell migration relative to the control and inhibition of c-Src signaling using siRNA, or a pharmacological inhibitor (SU6656), prevented this increase. Hence, the role of NDRG1 in decreasing cell migration is, in part, due to its inhibition of c-Src activation. In addition, novel pharmacological agents, which induce NDRG1 expression and are currently under development as anti-metastatic agents, markedly increase NDRG1 and decrease c-Src activation. This study leads to important insights into the mechanism involved in inhibiting metastasis by NDRG1 and how to target these pathways with novel therapeutics.

No MeSH data available.


Related in: MedlinePlus