Limits...
A novel HIF-1α-integrin-linked kinase regulatory loop that facilitates hypoxia-induced HIF-1α expression and epithelial-mesenchymal transition in cancer cells.

Chou CC, Chuang HC, Salunke SB, Kulp SK, Chen CS - Oncotarget (2015)

Bottom Line: We show that ILK can account for the effects of hypoxia on Akt, mTOR, and GSK3β phosphorylation.In concert with HIF-1α, these downstream effectors promote epithelial-mesenchymal transition (EMT) through modulation of Snail and Zeb1.Finally, we show that the small-molecule ILK inhibitor T315 can disrupt this regulatory loop in vivo and suppress xenograft tumor growth, thereby providing proof-of-concept that targeting ILK represents an effective strategy to block HIF-1α expression and aggressive phenotype in cancer cells.

View Article: PubMed Central - PubMed

Affiliation: Division of Medicinal Chemistry, College of Pharmacy and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio, USA.

ABSTRACT
Here, we described a novel regulatory feedback loop in which hypoxia induces integrin-linked kinase (ILK) expression through a HIF-1α-dependent mechanism and ILK, in turn, stimulates HIF-1α expression through cell type- and cell context-dependent pathways. HIF-1α increased ILK via transcriptional activation. ILK increased HIF-1α levels by promoting mTOR-mediated translation in PC-3 and MCF-7 cells, and by blocking GSK3β-mediated degradation in LNCaP cells, consistent with the cell line-/cellular context-specific functions of ILK as a Ser473-Akt kinase. We show that ILK can account for the effects of hypoxia on Akt, mTOR, and GSK3β phosphorylation. Also, ILK can de-repress HIF-1α signaling through the YB-1-mediated inhibition of Foxo3a expression. In concert with HIF-1α, these downstream effectors promote epithelial-mesenchymal transition (EMT) through modulation of Snail and Zeb1. Thus, the ILK-HIF-1α regulatory loop could underlie the maintenance of high HIF-1α expression levels and the promotion of EMT under hypoxic conditions. Finally, we show that the small-molecule ILK inhibitor T315 can disrupt this regulatory loop in vivo and suppress xenograft tumor growth, thereby providing proof-of-concept that targeting ILK represents an effective strategy to block HIF-1α expression and aggressive phenotype in cancer cells.

No MeSH data available.


Related in: MedlinePlus

Effect of ILK inhibition by treatment with T315 on PC-3 xenograft tumors(A) Effect of T315 (p.o., 50 mg/kg, once daily) on PC-3 tumor growth in nude mice (n = 8). Inset, average body weights of each treatment group during the study. Data are presented as means ± S.E. (*p < 0.05 compared to vehicle). (B & C) Western blot analysis of the phosphorylation/expression levels of relevant markers in six representative tumors from each treatment group. (B) Immunoblots. (C) Relative expression levels of the various markers based on densitometric quantitation of band intensities. Data are presented as means ± SD (*p < 0.05 compared to vehicle). T, T315; V, vehicle. (D) Diagrams depicting the mechanisms by which ILK inhibition regulates HIF-1α expression and reverses the mesenchymal phenotype of cancer cells under hypoxic conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4480751&req=5

Figure 7: Effect of ILK inhibition by treatment with T315 on PC-3 xenograft tumors(A) Effect of T315 (p.o., 50 mg/kg, once daily) on PC-3 tumor growth in nude mice (n = 8). Inset, average body weights of each treatment group during the study. Data are presented as means ± S.E. (*p < 0.05 compared to vehicle). (B & C) Western blot analysis of the phosphorylation/expression levels of relevant markers in six representative tumors from each treatment group. (B) Immunoblots. (C) Relative expression levels of the various markers based on densitometric quantitation of band intensities. Data are presented as means ± SD (*p < 0.05 compared to vehicle). T, T315; V, vehicle. (D) Diagrams depicting the mechanisms by which ILK inhibition regulates HIF-1α expression and reverses the mesenchymal phenotype of cancer cells under hypoxic conditions.

Mentions: In light of the high expression levels of both HIF-1α and ILK in PC-3 cells relative to the other cell lines examined and the sensitivity of PC-3 xenograft tumors to ILK inhibition [19], the PC-3 xenograft tumor model was selected to assess the ability of T315 to disrupt the HIF-1α-ILK regulatory loop in vivo. Daily oral administration of T315 (50 mg/kg) to tumor-bearing mice was well tolerated as no loss of body weight (Figure 7A, inset) or other overt signs of toxicity were observed. Consistent with our previous report [19], T315 significantly suppressed PC-3 xenograft tumor growth relative to the vehicle-treated control after 35 days of treatment (means ± S.E., 199 ± 27 versus 455 ± 116 mm3) (Figure 7A). This tumor suppression was associated with decreased intratumoral expression of HIF-1α and ILK, accompanied by parallel decreases in the phosphorylation/expression levels of ILK's downstream targets (Akt, mTOR, GSK3β), as well as increased epithelial (Foxo3a, E-cadherin) and decreased mesenchymal (YB-1, vimentin, Snail, Zeb1) markers (Figure 7B and 7C). Together, these findings suggest that ILK inhibition by a small-molecule agent reversed the mesenchymal phenotype of PC-3 tumors by disrupting the HIF-1α-ILK feedback loop.


A novel HIF-1α-integrin-linked kinase regulatory loop that facilitates hypoxia-induced HIF-1α expression and epithelial-mesenchymal transition in cancer cells.

Chou CC, Chuang HC, Salunke SB, Kulp SK, Chen CS - Oncotarget (2015)

Effect of ILK inhibition by treatment with T315 on PC-3 xenograft tumors(A) Effect of T315 (p.o., 50 mg/kg, once daily) on PC-3 tumor growth in nude mice (n = 8). Inset, average body weights of each treatment group during the study. Data are presented as means ± S.E. (*p < 0.05 compared to vehicle). (B & C) Western blot analysis of the phosphorylation/expression levels of relevant markers in six representative tumors from each treatment group. (B) Immunoblots. (C) Relative expression levels of the various markers based on densitometric quantitation of band intensities. Data are presented as means ± SD (*p < 0.05 compared to vehicle). T, T315; V, vehicle. (D) Diagrams depicting the mechanisms by which ILK inhibition regulates HIF-1α expression and reverses the mesenchymal phenotype of cancer cells under hypoxic conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4480751&req=5

Figure 7: Effect of ILK inhibition by treatment with T315 on PC-3 xenograft tumors(A) Effect of T315 (p.o., 50 mg/kg, once daily) on PC-3 tumor growth in nude mice (n = 8). Inset, average body weights of each treatment group during the study. Data are presented as means ± S.E. (*p < 0.05 compared to vehicle). (B & C) Western blot analysis of the phosphorylation/expression levels of relevant markers in six representative tumors from each treatment group. (B) Immunoblots. (C) Relative expression levels of the various markers based on densitometric quantitation of band intensities. Data are presented as means ± SD (*p < 0.05 compared to vehicle). T, T315; V, vehicle. (D) Diagrams depicting the mechanisms by which ILK inhibition regulates HIF-1α expression and reverses the mesenchymal phenotype of cancer cells under hypoxic conditions.
Mentions: In light of the high expression levels of both HIF-1α and ILK in PC-3 cells relative to the other cell lines examined and the sensitivity of PC-3 xenograft tumors to ILK inhibition [19], the PC-3 xenograft tumor model was selected to assess the ability of T315 to disrupt the HIF-1α-ILK regulatory loop in vivo. Daily oral administration of T315 (50 mg/kg) to tumor-bearing mice was well tolerated as no loss of body weight (Figure 7A, inset) or other overt signs of toxicity were observed. Consistent with our previous report [19], T315 significantly suppressed PC-3 xenograft tumor growth relative to the vehicle-treated control after 35 days of treatment (means ± S.E., 199 ± 27 versus 455 ± 116 mm3) (Figure 7A). This tumor suppression was associated with decreased intratumoral expression of HIF-1α and ILK, accompanied by parallel decreases in the phosphorylation/expression levels of ILK's downstream targets (Akt, mTOR, GSK3β), as well as increased epithelial (Foxo3a, E-cadherin) and decreased mesenchymal (YB-1, vimentin, Snail, Zeb1) markers (Figure 7B and 7C). Together, these findings suggest that ILK inhibition by a small-molecule agent reversed the mesenchymal phenotype of PC-3 tumors by disrupting the HIF-1α-ILK feedback loop.

Bottom Line: We show that ILK can account for the effects of hypoxia on Akt, mTOR, and GSK3β phosphorylation.In concert with HIF-1α, these downstream effectors promote epithelial-mesenchymal transition (EMT) through modulation of Snail and Zeb1.Finally, we show that the small-molecule ILK inhibitor T315 can disrupt this regulatory loop in vivo and suppress xenograft tumor growth, thereby providing proof-of-concept that targeting ILK represents an effective strategy to block HIF-1α expression and aggressive phenotype in cancer cells.

View Article: PubMed Central - PubMed

Affiliation: Division of Medicinal Chemistry, College of Pharmacy and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio, USA.

ABSTRACT
Here, we described a novel regulatory feedback loop in which hypoxia induces integrin-linked kinase (ILK) expression through a HIF-1α-dependent mechanism and ILK, in turn, stimulates HIF-1α expression through cell type- and cell context-dependent pathways. HIF-1α increased ILK via transcriptional activation. ILK increased HIF-1α levels by promoting mTOR-mediated translation in PC-3 and MCF-7 cells, and by blocking GSK3β-mediated degradation in LNCaP cells, consistent with the cell line-/cellular context-specific functions of ILK as a Ser473-Akt kinase. We show that ILK can account for the effects of hypoxia on Akt, mTOR, and GSK3β phosphorylation. Also, ILK can de-repress HIF-1α signaling through the YB-1-mediated inhibition of Foxo3a expression. In concert with HIF-1α, these downstream effectors promote epithelial-mesenchymal transition (EMT) through modulation of Snail and Zeb1. Thus, the ILK-HIF-1α regulatory loop could underlie the maintenance of high HIF-1α expression levels and the promotion of EMT under hypoxic conditions. Finally, we show that the small-molecule ILK inhibitor T315 can disrupt this regulatory loop in vivo and suppress xenograft tumor growth, thereby providing proof-of-concept that targeting ILK represents an effective strategy to block HIF-1α expression and aggressive phenotype in cancer cells.

No MeSH data available.


Related in: MedlinePlus