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KLF17 empowers TGF-β/Smad signaling by targeting Smad3-dependent pathway to suppress tumor growth and metastasis during cancer progression.

Ali A, Zhang P, Liangfang Y, Wenshe S, Wang H, Lin X, Dai Y, Feng XH, Moses R, Wang D, Li X, Xiao J - Cell Death Dis (2015)

Bottom Line: Mechanistically, silencing KLF17 reduced Smad3-DNA complex formation on Smad binding element (SBE) and affects the expression of TGF-β/Smad target genes.Intriguingly, TGF-β stimulates the recruitment of KLF17 on chromatin to subsets of metastasis-associated genes.Clinically, KLF17 expression significantly decreases during advance HCC.

View Article: PubMed Central - PubMed

Affiliation: 1] Nortern Jiangsu People's Hospital (Medical College of Yangzhou University), Yangzhou, Jiangsu 225001, China [2] Shanghai Key Laboratory of Regulatory Biology, Key Laboratory of Brain Functional Genomics (Ministry of Education), Shanghai Key Laboratory of Brain Functional Genomics, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China.

ABSTRACT
Inhibition of tumor suppressive signaling is linked to cancer progression, metastasis and epithelial-mesenchymal transition (EMT). Transforming growth factor-β1 (TGF-β)/Smad signaling plays an important role in tumor suppression. Kruppel-like-factor 17 (KLF17) is a negative regulator of metastasis and EMT. However, underlying mechanisms leading to tumor suppressive and anti-metastatic function of KLF17 still remains unknown. Here, we show that KLF17 plays an integral role in potentiating TGF-β/Smad signaling via Smad3-dependent pathway to suppress tumor progression. Intriguingly, TGF-β/Smad3 signaling induces KLF17 expression, generating a positive feedback loop. TGF-β/Smad3-KLF17 loop is critical for anti-metastasis and tumor inhibition in cancer cells. Mechanistically, silencing KLF17 reduced Smad3-DNA complex formation on Smad binding element (SBE) and affects the expression of TGF-β/Smad target genes. Moreover, KLF17 alters Smad3 binding pattern on chromatin. KLF17 regulates TGF-β target genes that are Smad3-dependent. Smad3 and KLF17 physically interact with each other via KLF17 responsive elements/SBE region. Intriguingly, TGF-β stimulates the recruitment of KLF17 on chromatin to subsets of metastasis-associated genes. Functionally, depletion of KLF17 enhanced tumorigenic features in cancer cells. KLF17 is critical for full cytostatic function of TGF-β/Smad signaling. Clinically, KLF17 expression significantly decreases during advance HCC. KLF17 shows positive correlation with Smad3 levels in cancer samples. Our data shows that enhance KLF17 activity has important therapeutic implications for targeted-therapies aimed at TGF-β/Smad3 pathway. These findings define novel mechanism by which TGF-β/Smad-KLF17 pathway mutually affect each other during cancer metastasis, provide a new model of regulation of TGF-β/Smad signaling by KLF17 and defines new insights into anti-metastatic function of KLF17.

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KLF17 regulates a panel of TGF-β-SMAD3-dependent target genes. (a and b) HepG2 cells were transfected with control siRNA or siRNA targeting against KLF17 (20 nM) for 48 h, and analyzed by RT-PCR. Data are representative of three independent experiments (mean±S.D.). (Two-tailed Student's t-test, *P<0.05, **P<0.005)
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fig4: KLF17 regulates a panel of TGF-β-SMAD3-dependent target genes. (a and b) HepG2 cells were transfected with control siRNA or siRNA targeting against KLF17 (20 nM) for 48 h, and analyzed by RT-PCR. Data are representative of three independent experiments (mean±S.D.). (Two-tailed Student's t-test, *P<0.05, **P<0.005)

Mentions: Based on the above findings, we hypothesize that KLF17 may have broader impact on the transcriptional regulation of TGF-β/Smad-dependent target genes. We thus examined the levels of several TGF-β/Smad-dependent target genes in KLF17 knockdown cells and control cells. Using Real time-PCR (RT-PCR) approach, we observed changes in the expression of several TGF-β/Smad-dependent target genes between control and KLF17 knockdown cells (Figure 4a), suggesting that KLF17 indeed influences the transcriptional program of the TGF-β/Smad pathway. Importantly, genes upregulated by Smad3/4 in response to TGF-β, including p15, PUMA, ATF-3, TGLN, CBFA-1 and 14-3-3δ,36, 37, 38 were repressed in the absence of KLF17 (Figure 4a). In contrast, genes repressed by Smad3/4, such as CEACAM-5, MMP-1, C-MYC, BCL-2, ID1 and hTERT,36, 39, 40 were de-repressed when KLF17 was depleted, indicating a positive regulation of Smad3 by KLF17 (Figure 4a).


KLF17 empowers TGF-β/Smad signaling by targeting Smad3-dependent pathway to suppress tumor growth and metastasis during cancer progression.

Ali A, Zhang P, Liangfang Y, Wenshe S, Wang H, Lin X, Dai Y, Feng XH, Moses R, Wang D, Li X, Xiao J - Cell Death Dis (2015)

KLF17 regulates a panel of TGF-β-SMAD3-dependent target genes. (a and b) HepG2 cells were transfected with control siRNA or siRNA targeting against KLF17 (20 nM) for 48 h, and analyzed by RT-PCR. Data are representative of three independent experiments (mean±S.D.). (Two-tailed Student's t-test, *P<0.05, **P<0.005)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385926&req=5

fig4: KLF17 regulates a panel of TGF-β-SMAD3-dependent target genes. (a and b) HepG2 cells were transfected with control siRNA or siRNA targeting against KLF17 (20 nM) for 48 h, and analyzed by RT-PCR. Data are representative of three independent experiments (mean±S.D.). (Two-tailed Student's t-test, *P<0.05, **P<0.005)
Mentions: Based on the above findings, we hypothesize that KLF17 may have broader impact on the transcriptional regulation of TGF-β/Smad-dependent target genes. We thus examined the levels of several TGF-β/Smad-dependent target genes in KLF17 knockdown cells and control cells. Using Real time-PCR (RT-PCR) approach, we observed changes in the expression of several TGF-β/Smad-dependent target genes between control and KLF17 knockdown cells (Figure 4a), suggesting that KLF17 indeed influences the transcriptional program of the TGF-β/Smad pathway. Importantly, genes upregulated by Smad3/4 in response to TGF-β, including p15, PUMA, ATF-3, TGLN, CBFA-1 and 14-3-3δ,36, 37, 38 were repressed in the absence of KLF17 (Figure 4a). In contrast, genes repressed by Smad3/4, such as CEACAM-5, MMP-1, C-MYC, BCL-2, ID1 and hTERT,36, 39, 40 were de-repressed when KLF17 was depleted, indicating a positive regulation of Smad3 by KLF17 (Figure 4a).

Bottom Line: Mechanistically, silencing KLF17 reduced Smad3-DNA complex formation on Smad binding element (SBE) and affects the expression of TGF-β/Smad target genes.Intriguingly, TGF-β stimulates the recruitment of KLF17 on chromatin to subsets of metastasis-associated genes.Clinically, KLF17 expression significantly decreases during advance HCC.

View Article: PubMed Central - PubMed

Affiliation: 1] Nortern Jiangsu People's Hospital (Medical College of Yangzhou University), Yangzhou, Jiangsu 225001, China [2] Shanghai Key Laboratory of Regulatory Biology, Key Laboratory of Brain Functional Genomics (Ministry of Education), Shanghai Key Laboratory of Brain Functional Genomics, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China.

ABSTRACT
Inhibition of tumor suppressive signaling is linked to cancer progression, metastasis and epithelial-mesenchymal transition (EMT). Transforming growth factor-β1 (TGF-β)/Smad signaling plays an important role in tumor suppression. Kruppel-like-factor 17 (KLF17) is a negative regulator of metastasis and EMT. However, underlying mechanisms leading to tumor suppressive and anti-metastatic function of KLF17 still remains unknown. Here, we show that KLF17 plays an integral role in potentiating TGF-β/Smad signaling via Smad3-dependent pathway to suppress tumor progression. Intriguingly, TGF-β/Smad3 signaling induces KLF17 expression, generating a positive feedback loop. TGF-β/Smad3-KLF17 loop is critical for anti-metastasis and tumor inhibition in cancer cells. Mechanistically, silencing KLF17 reduced Smad3-DNA complex formation on Smad binding element (SBE) and affects the expression of TGF-β/Smad target genes. Moreover, KLF17 alters Smad3 binding pattern on chromatin. KLF17 regulates TGF-β target genes that are Smad3-dependent. Smad3 and KLF17 physically interact with each other via KLF17 responsive elements/SBE region. Intriguingly, TGF-β stimulates the recruitment of KLF17 on chromatin to subsets of metastasis-associated genes. Functionally, depletion of KLF17 enhanced tumorigenic features in cancer cells. KLF17 is critical for full cytostatic function of TGF-β/Smad signaling. Clinically, KLF17 expression significantly decreases during advance HCC. KLF17 shows positive correlation with Smad3 levels in cancer samples. Our data shows that enhance KLF17 activity has important therapeutic implications for targeted-therapies aimed at TGF-β/Smad3 pathway. These findings define novel mechanism by which TGF-β/Smad-KLF17 pathway mutually affect each other during cancer metastasis, provide a new model of regulation of TGF-β/Smad signaling by KLF17 and defines new insights into anti-metastatic function of KLF17.

Show MeSH
Related in: MedlinePlus