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Ahnak functions as a tumor suppressor via modulation of TGF?/Smad signaling pathway.

ABSTRACT: We provide detailed mechanisms of Ahnak-mediated potentiation of transforming growth factor ? (TGF?) signaling, which leads to a negative regulation of cell growth. We show that Smad3 interacts with Ahnak through MH2 domain and that Ahnak stimulates Smad3 localization into nucleus leading to potentiating TGF?-induced transcriptional activity of R-Smad. Moreover, overexpression of Ahnak resulted in growth retardation and cell cycle arrest through downregulation of c-Myc and cyclin D1/D2. We describe results from analyses of Ahnak(-/-) mouse model expressing middle T antigen in a mammary gland-specific manner (MMTV(Tg/+)Ahnak(-/-)), which showed significantly progressed hyperplasia of mammary glands compared with MMTV(Tg/+)Ahnak(+/+). Finally, we screened multiple human breast cancer tissues and showed that the expression of Ahnak in cancer tissues is lower than that in control tissues by 50%. Taken together, these data indicate that Ahnak mediates a negative regulation of cell growth and acts as novel tumor suppressor through potentiation of TGF? signaling.

SUBMITTER: Lee IH

PROVIDER: S-EPMC4180639 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Ahnak functions as a tumor suppressor via modulation of TGFβ/Smad signaling pathway.

Lee I H IH Sohn M M Lim H J HJ Yoon S S Oh H H Shin S S Shin J H JH Oh S-H SH Kim J J Lee D K DK Noh D Y DY Bae D S DS Seong J K JK Bae Y S YS

Oncogene 20140324 38

We provide detailed mechanisms of Ahnak-mediated potentiation of transforming growth factor β (TGFβ) signaling, which leads to a negative regulation of cell growth. We show that Smad3 interacts with Ahnak through MH2 domain and that Ahnak stimulates Smad3 localization into nucleus leading to potentiating TGFβ-induced transcriptional activity of R-Smad. Moreover, overexpression of Ahnak resulted in growth retardation and cell cycle arrest through downregulation of c-Myc and cyclin D1/D2. We descr ...[more]

PMID: 24662814

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Project description:BackgroundGlioblastoma multiforme (GBM) is characterized by lethal aggressiveness and patients with GBM are in urgent need for new therapeutic avenues to improve quality of life. Current studies on tumor invasion focused on roles of cytokines in tumor microenvironment and numerous evidence suggests that TGF-β2 is abundant in glioma microenvironment and vital for glioma invasion. Autopagy is also emerging as a critical factor in aggressive behaviors of cancer cells; however, the relationship between TGF-β2 and autophagy in glioma has been poorly understood.MethodsU251, T98 and U87 GBM cell lines as well as GBM cells from a primary human specimen were used in vitro and in vivo to evaluate the effect of TGF-β2 on autophagy. Western blot, qPCR, immunofluorescence and transmission-electron microscope were used to detect target molecular expression. Lentivirus and siRNA vehicle were introduced to establish cell lines, as well as mitotracker and seahorse experiment to study the metabolic process in glioma. Preclinical therapeutic efficacy was evaluated in orthotopic xenograft mouse models.ResultsHere we demonstrated that TGF-β2 activated autophagy in human glioma cell lines and knockdown of Smad2 or inhibition of c-Jun NH2-terminal kinase, attenuated TGF-β2-induced autophagy. TGF-β2-induced autophagy is important for glioma invasion due to the alteration of epithelial-mesenchymal transition and metabolism conversion, particularly influencing mitochondria trafficking and membrane potential (△Ψm). Autopaghy also initiated a feedback on TGF-β2 in glioma by keeping its autocrine loop and affecting Smad2/3/7 expression. A xenograft model provided additional confirmation on combination of TGF-β inhibitor (Galunisertib) and autophagy inhibitor (CQ) to better "turn off" tumor growth.ConclusionOur findings elucidated a potential mechanism of autophagy-associated glioma invasion that TGF-β2 could initiate autophagy via Smad and non-Smad pathway to promote glioma cells' invasion.

Dataset Information

Ahnak functions as a tumor suppressor via modulation of TGF?/Smad signaling pathway.

Publications

Ahnak functions as a tumor suppressor via modulation of TGFβ/Smad signaling pathway.

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