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ASPL-TFE3 Oncoprotein Regulates Cell Cycle Progression and Induces Cellular Senescence by Up-Regulating p21

View Article: PubMed Central - PubMed

ABSTRACT

Alveolar soft part sarcoma is an extremely rare soft tissue sarcoma with poor prognosis. It is characterized by the unbalanced recurrent chromosomal translocation der(17)t(X;17)(p11;q25), resulting in the generation of an ASPL-TFE3 fusion gene. ASPL-TFE3 oncoprotein functions as an aberrant transcriptional factor and is considered to play a crucial role in the tumorigenesis of alveolar soft part sarcoma. However, the underlying molecular mechanisms are poorly understood. In this study, we identified p21 (p21WAF1/CIP1) as a direct transcriptional target of ASPL-TFE3. Ectopic ASPL-TFE3 expression in 293 cells resulted in cell cycle arrest and significant increases in protein and mRNA levels of p21. ASPL-TFE3 activated p21 expression in a p53-independent manner through direct transcriptional interactions with the p21 promoter region. When ASPL-TFE3 was expressed in human bone marrow–derived mesenchymal stem cells in a tetracycline-inducible manner, we observed the up-regulation of p21 expression and the induction of senescence-associated β-galactosidase activity. Suppression of p21 significantly decreased the induction of ASPL-TFE3-mediated cellular senescence. Furthermore, ASPL-TFE3 expression in mesenchymal stem cells resulted in a significant up-regulation of proinflammatory cytokines associated with senescence-associated secretory phenotype (SASP). These results show that ASPL-TFE3 regulates cell cycle progression and induces cellular senescence by up-regulating p21 expression. In addition, our data suggest a potential mechanism by which ASPL-TFE3-induced senescence may play a role in tumorigenesis by inducing SASP, which could promote the protumorigenic microenvironment.

No MeSH data available.


ASPL-TFE3 up-regulates the expression of proinflammatory cytokines. UE7T-TR-AT cells were cultured in the presence of tetracycline for the indicated days, and then the expression of IL1A, IL1B, IL6, and IL8 was analyzed by real-time quantitative PCR. Gene expression data were normalized to those for beta-actin. Data are presented as fold changes in mRNA levels relative to those on day 0 from three independent experiments. Error bars show SD; *P < .05; **P < .01.
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f0030: ASPL-TFE3 up-regulates the expression of proinflammatory cytokines. UE7T-TR-AT cells were cultured in the presence of tetracycline for the indicated days, and then the expression of IL1A, IL1B, IL6, and IL8 was analyzed by real-time quantitative PCR. Gene expression data were normalized to those for beta-actin. Data are presented as fold changes in mRNA levels relative to those on day 0 from three independent experiments. Error bars show SD; *P < .05; **P < .01.

Mentions: One of the hallmarks of senescent cells is the senescence-associated secretory phenotype (SASP), which influences the microenvironment via the secretion of proinflammatory cytokines and growth factors [35], [36]. Senescent cells have undergone widespread changes in protein expression and secretion, ultimately leading to the SASP. Despite the tumor-suppressing role of senescence-associated cell cycle arrest, SASP has been suggested to promote tumorigenesis [36]. Thus, we examined the expression of representative SASP-associated proinflammatory cytokines, including IL1A, IL1B, IL6, and IL8, in tetracycline-treated UE7T/TR-AT cells by quantitative real-time PCR (Figure 6). At 4 days after tetracycline treatment, the expression of IL1A, IL1B, and IL8 was significantly increased compared with that of untreated UE7T/TR-AT cells. In contrast, the expression levels of IL1B, IL6, and IL8 were decreased at 1 day after tetracycline treatment, suggesting that the up-regulation of proinflammatory cytokines is probably not due to direct transcriptional up-regulation by ASPL-TFE3.


ASPL-TFE3 Oncoprotein Regulates Cell Cycle Progression and Induces Cellular Senescence by Up-Regulating p21
ASPL-TFE3 up-regulates the expression of proinflammatory cytokines. UE7T-TR-AT cells were cultured in the presence of tetracycline for the indicated days, and then the expression of IL1A, IL1B, IL6, and IL8 was analyzed by real-time quantitative PCR. Gene expression data were normalized to those for beta-actin. Data are presented as fold changes in mRNA levels relative to those on day 0 from three independent experiments. Error bars show SD; *P < .05; **P < .01.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037204&req=5

f0030: ASPL-TFE3 up-regulates the expression of proinflammatory cytokines. UE7T-TR-AT cells were cultured in the presence of tetracycline for the indicated days, and then the expression of IL1A, IL1B, IL6, and IL8 was analyzed by real-time quantitative PCR. Gene expression data were normalized to those for beta-actin. Data are presented as fold changes in mRNA levels relative to those on day 0 from three independent experiments. Error bars show SD; *P < .05; **P < .01.
Mentions: One of the hallmarks of senescent cells is the senescence-associated secretory phenotype (SASP), which influences the microenvironment via the secretion of proinflammatory cytokines and growth factors [35], [36]. Senescent cells have undergone widespread changes in protein expression and secretion, ultimately leading to the SASP. Despite the tumor-suppressing role of senescence-associated cell cycle arrest, SASP has been suggested to promote tumorigenesis [36]. Thus, we examined the expression of representative SASP-associated proinflammatory cytokines, including IL1A, IL1B, IL6, and IL8, in tetracycline-treated UE7T/TR-AT cells by quantitative real-time PCR (Figure 6). At 4 days after tetracycline treatment, the expression of IL1A, IL1B, and IL8 was significantly increased compared with that of untreated UE7T/TR-AT cells. In contrast, the expression levels of IL1B, IL6, and IL8 were decreased at 1 day after tetracycline treatment, suggesting that the up-regulation of proinflammatory cytokines is probably not due to direct transcriptional up-regulation by ASPL-TFE3.

View Article: PubMed Central - PubMed

ABSTRACT

Alveolar soft part sarcoma is an extremely rare soft tissue sarcoma with poor prognosis. It is characterized by the unbalanced recurrent chromosomal translocation der(17)t(X;17)(p11;q25), resulting in the generation of an ASPL-TFE3 fusion gene. ASPL-TFE3 oncoprotein functions as an aberrant transcriptional factor and is considered to play a crucial role in the tumorigenesis of alveolar soft part sarcoma. However, the underlying molecular mechanisms are poorly understood. In this study, we identified p21 (p21WAF1/CIP1) as a direct transcriptional target of ASPL-TFE3. Ectopic ASPL-TFE3 expression in 293 cells resulted in cell cycle arrest and significant increases in protein and mRNA levels of p21. ASPL-TFE3 activated p21 expression in a p53-independent manner through direct transcriptional interactions with the p21 promoter region. When ASPL-TFE3 was expressed in human bone marrow&ndash;derived mesenchymal stem cells in a tetracycline-inducible manner, we observed the up-regulation of p21 expression and the induction of senescence-associated &beta;-galactosidase activity. Suppression of p21 significantly decreased the induction of ASPL-TFE3-mediated cellular senescence. Furthermore, ASPL-TFE3 expression in mesenchymal stem cells resulted in a significant up-regulation of proinflammatory cytokines associated with senescence-associated secretory phenotype (SASP). These results show that ASPL-TFE3 regulates cell cycle progression and induces cellular senescence by up-regulating p21 expression. In addition, our data suggest a potential mechanism by which ASPL-TFE3-induced senescence may play a role in tumorigenesis by inducing SASP, which could promote the protumorigenic microenvironment.

No MeSH data available.