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T-cell intracellular antigens function as tumor suppressor genes.

Sánchez-Jiménez C, Ludeña MD, Izquierdo JM - Cell Death Dis (2015)

Bottom Line: Genome-wide profiling illustrates a selective upregulation of p53 signaling pathway-related genes.Remarkably, low expressions of TIA1 and TIAR correlate with poor prognosis in patients with lung squamous cell carcinoma.These findings strongly support the concept that TIA proteins act as tumor suppressor genes.

View Article: PubMed Central - PubMed

Affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid (CSIC/UAM), C/ Nicolás Cabrera 1, Madrid, Spain.

ABSTRACT
Knockdown of T-cell intracellular antigens TIA1 and TIAR in transformed cells triggers cell proliferation and tumor growth. Using a tetracycline-inducible system, we report here that an increased expression of TIA1 or TIAR in 293 cells results in reduced rates of cell proliferation. Ectopic expression of these proteins abolish endogenous TIA1 and TIAR levels via the regulation of splicing of their pre-mRNAs, and partially represses global translation in a phospho-eukaryotic initiation factor 2 alpha-dependent manner. This is accompanied by cell cycle arrest at G1/S and cell death through caspase-dependent apoptosis and autophagy. Genome-wide profiling illustrates a selective upregulation of p53 signaling pathway-related genes. Nude mice injected with doxycycline-inducible cells expressing TIA1 or TIAR retard, or even inhibit, growth of xenotumors. Remarkably, low expressions of TIA1 and TIAR correlate with poor prognosis in patients with lung squamous cell carcinoma. These findings strongly support the concept that TIA proteins act as tumor suppressor genes.

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Expression of TIA proteins leads to slow cell death mediated by caspase-dependent apoptosis and late autophagy. (a) Analysis of cellular morphology and viability of FT293 cells for 3–7 days. Scale bars represent 20 μm (b) Quantification of cell death rates at 4 and 7 days. The represented values are means±S.E.M. (n=3–5; *P<0.01; **P<0.001) (c) Western blot analysis of cell death markers at 4 and 7 days (d) Cell death by apoptosis occurs in a caspase-dependent way. FT293 cells were grown for 4 days and then treated for 4 days further with DMSO or caspase inhibitor Z-VAD-FMK. The represented values are means±S.E.M. (n=2; *P<0.01)
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fig3: Expression of TIA proteins leads to slow cell death mediated by caspase-dependent apoptosis and late autophagy. (a) Analysis of cellular morphology and viability of FT293 cells for 3–7 days. Scale bars represent 20 μm (b) Quantification of cell death rates at 4 and 7 days. The represented values are means±S.E.M. (n=3–5; *P<0.01; **P<0.001) (c) Western blot analysis of cell death markers at 4 and 7 days (d) Cell death by apoptosis occurs in a caspase-dependent way. FT293 cells were grown for 4 days and then treated for 4 days further with DMSO or caspase inhibitor Z-VAD-FMK. The represented values are means±S.E.M. (n=2; *P<0.01)

Mentions: Given these growth-restricted phenotypes, cell lines were analyzed by microscopy for an extended period (3–7 days post induction). Sustained TIA1 and TIAR expression for 4 days was associated with obvious deleterious changes in cellular and nuclear morphology that became dramatic after 7 days in culture (Figure 3a and Supplementary Figure S4), indicating the existence of additional mechanisms that limit cell growth. We therefore measured cell death by flow cytometry. We found a significant increase in the percentage of cells undergoing cell death at 4 days, which was further elevated at 7 days (Figure 3b). Analysis of molecular markers related to apoptotic and autophagic phenotypes, as cleaved poly (ADP-ribose) polymerase and activated caspase-3, 8 and 9, or processed LC3B-II, respectively, confirmed the evolution of cell death at 4 and 7 days (Figure 3c), and were consistent with the existence of cell death events associated with slow apoptosis and late autophagy (Figure 3c). In addition, treatment of FT293 cells expressing GFP, HuR, TIA1 or TIAR with the broad-spectrum caspase inhibitor Z-VAD-FMK for 4 days resulted in a significant prevention of apoptosis in TIA1- and TIAR-expressing cells (Figure 3d). Collectively, these findings strongly suggest that sustained TIA1 or TIAR expression inhibits cell proliferation, favors cell cycle arrest at G1/S and triggers cell death through slow caspase-dependent apoptosis and late autophagy.


T-cell intracellular antigens function as tumor suppressor genes.

Sánchez-Jiménez C, Ludeña MD, Izquierdo JM - Cell Death Dis (2015)

Expression of TIA proteins leads to slow cell death mediated by caspase-dependent apoptosis and late autophagy. (a) Analysis of cellular morphology and viability of FT293 cells for 3–7 days. Scale bars represent 20 μm (b) Quantification of cell death rates at 4 and 7 days. The represented values are means±S.E.M. (n=3–5; *P<0.01; **P<0.001) (c) Western blot analysis of cell death markers at 4 and 7 days (d) Cell death by apoptosis occurs in a caspase-dependent way. FT293 cells were grown for 4 days and then treated for 4 days further with DMSO or caspase inhibitor Z-VAD-FMK. The represented values are means±S.E.M. (n=2; *P<0.01)
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4385921&req=5

fig3: Expression of TIA proteins leads to slow cell death mediated by caspase-dependent apoptosis and late autophagy. (a) Analysis of cellular morphology and viability of FT293 cells for 3–7 days. Scale bars represent 20 μm (b) Quantification of cell death rates at 4 and 7 days. The represented values are means±S.E.M. (n=3–5; *P<0.01; **P<0.001) (c) Western blot analysis of cell death markers at 4 and 7 days (d) Cell death by apoptosis occurs in a caspase-dependent way. FT293 cells were grown for 4 days and then treated for 4 days further with DMSO or caspase inhibitor Z-VAD-FMK. The represented values are means±S.E.M. (n=2; *P<0.01)
Mentions: Given these growth-restricted phenotypes, cell lines were analyzed by microscopy for an extended period (3–7 days post induction). Sustained TIA1 and TIAR expression for 4 days was associated with obvious deleterious changes in cellular and nuclear morphology that became dramatic after 7 days in culture (Figure 3a and Supplementary Figure S4), indicating the existence of additional mechanisms that limit cell growth. We therefore measured cell death by flow cytometry. We found a significant increase in the percentage of cells undergoing cell death at 4 days, which was further elevated at 7 days (Figure 3b). Analysis of molecular markers related to apoptotic and autophagic phenotypes, as cleaved poly (ADP-ribose) polymerase and activated caspase-3, 8 and 9, or processed LC3B-II, respectively, confirmed the evolution of cell death at 4 and 7 days (Figure 3c), and were consistent with the existence of cell death events associated with slow apoptosis and late autophagy (Figure 3c). In addition, treatment of FT293 cells expressing GFP, HuR, TIA1 or TIAR with the broad-spectrum caspase inhibitor Z-VAD-FMK for 4 days resulted in a significant prevention of apoptosis in TIA1- and TIAR-expressing cells (Figure 3d). Collectively, these findings strongly suggest that sustained TIA1 or TIAR expression inhibits cell proliferation, favors cell cycle arrest at G1/S and triggers cell death through slow caspase-dependent apoptosis and late autophagy.

Bottom Line: Genome-wide profiling illustrates a selective upregulation of p53 signaling pathway-related genes.Remarkably, low expressions of TIA1 and TIAR correlate with poor prognosis in patients with lung squamous cell carcinoma.These findings strongly support the concept that TIA proteins act as tumor suppressor genes.

View Article: PubMed Central - PubMed

Affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid (CSIC/UAM), C/ Nicolás Cabrera 1, Madrid, Spain.

ABSTRACT
Knockdown of T-cell intracellular antigens TIA1 and TIAR in transformed cells triggers cell proliferation and tumor growth. Using a tetracycline-inducible system, we report here that an increased expression of TIA1 or TIAR in 293 cells results in reduced rates of cell proliferation. Ectopic expression of these proteins abolish endogenous TIA1 and TIAR levels via the regulation of splicing of their pre-mRNAs, and partially represses global translation in a phospho-eukaryotic initiation factor 2 alpha-dependent manner. This is accompanied by cell cycle arrest at G1/S and cell death through caspase-dependent apoptosis and autophagy. Genome-wide profiling illustrates a selective upregulation of p53 signaling pathway-related genes. Nude mice injected with doxycycline-inducible cells expressing TIA1 or TIAR retard, or even inhibit, growth of xenotumors. Remarkably, low expressions of TIA1 and TIAR correlate with poor prognosis in patients with lung squamous cell carcinoma. These findings strongly support the concept that TIA proteins act as tumor suppressor genes.

Show MeSH
Related in: MedlinePlus