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Knockdown of a novel lincRNA AATBC suppresses proliferation and induces apoptosis in bladder cancer.

Zhao F, Lin T, He W, Han J, Zhu D, Hu K, Li W, Zheng Z, Huang J, Xie W - Oncotarget (2015)

Bottom Line: We also found that inhibition of AATBC resulted in cell proliferation arrest through G1 cell cycle mediated by cyclin D1, CDK4, p18 and phosphorylated Rb.Furthermore, JNK inhibitor SP600125 could attenuate the apoptotic effect achieved by AATBC knockdown, confirming the involvement of JNK signaling in the induced apoptosis.Moreover, mouse xenograft model revealed that knockdown of AATBC led to suppress tumorigenesis in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.

ABSTRACT
Long intergenic noncoding RNAs (lincRNAs) play important roles in regulating various biological processes in cancer, including proliferation and apoptosis. However, the roles of lincRNAs in bladder cancer remain elusive. In this study, we identified a novel lincRNA, which we termed AATBC. We found that AATBC was overexpressed in bladder cancer patient tissues and positively correlated with tumor grade and pT stage. We also found that inhibition of AATBC resulted in cell proliferation arrest through G1 cell cycle mediated by cyclin D1, CDK4, p18 and phosphorylated Rb. In addition, inhibition of AATBC induced cell apoptosis through the intrinsic apoptosis signaling pathway, as evidenced by the activation of caspase-9 and caspase-3. The investigation for the signaling pathway revealed that the apoptosis following AATBC knockdown was mediated by activation of phosphorylated JNK and suppression of NRF2. Furthermore, JNK inhibitor SP600125 could attenuate the apoptotic effect achieved by AATBC knockdown, confirming the involvement of JNK signaling in the induced apoptosis. Moreover, mouse xenograft model revealed that knockdown of AATBC led to suppress tumorigenesis in vivo. Taken together, our study indicated that AATBC might play a critical role in pro-proliferation and anti-apoptosis in bladder cancer by regulating cell cycle, intrinsic apoptosis signaling, JNK signaling and NRF2. AATBC could be a potential therapeutic target and molecular biomarker for bladder cancer.

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The involvement of JNK and NRF2 pathway in apoptosis induced by AATBC knockdownA. 36 hours after transfection, levels of JNK, p-JNK, p-p38, p-ERK1/2 and NRF2 were determined by Western blotting analysis. β-tubulin served as loading control. B. Indicated cell lines were treated with transfection and SP600125 for 36 hours. The levels of p-JNK, NRF2, caspase-9, caspase-3 and PARP were evaluated. β-tubulin served as loading control. C. 36 hours after treatment of transfection and SP600125, flow cytometric analysis showed that JNK inhibitor SP600125 could protect UM-UC-3 and EJ cells from apoptosis. Data was represented as means ± SD. *P <0.05 (vs. control).
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Figure 6: The involvement of JNK and NRF2 pathway in apoptosis induced by AATBC knockdownA. 36 hours after transfection, levels of JNK, p-JNK, p-p38, p-ERK1/2 and NRF2 were determined by Western blotting analysis. β-tubulin served as loading control. B. Indicated cell lines were treated with transfection and SP600125 for 36 hours. The levels of p-JNK, NRF2, caspase-9, caspase-3 and PARP were evaluated. β-tubulin served as loading control. C. 36 hours after treatment of transfection and SP600125, flow cytometric analysis showed that JNK inhibitor SP600125 could protect UM-UC-3 and EJ cells from apoptosis. Data was represented as means ± SD. *P <0.05 (vs. control).

Mentions: In view of the evidence that the MAPKs, consisting of ERK1/2, JNK and p38, play critical roles in apoptosis, we examined the activation of MAPK pathway to further uncover the underlying mechanisms for the alterations of apoptosis in UM-UC-3 and EJ cells after transfection with siRNAs. As revealed by Western blotting (Fig. 6A), knockdown of AATBC enhanced the phosphorylation level of JNK in both UM-UC-3 and EJ cells. In contrast, the expression levels of phosphorylated ERK1/2 and p38 were not obviously changed upon the treatment of AATBC knockdown. JNK-mediated apoptosis can occur through multiple pathways, including oxidative stress (OS) pathway [18]. Inspired by this, we detected the factors in OS pathway. In this study, besides the activation of JNK, we found that the expression level of NRF2, a key antioxidant transcription factor in OS pathway, was down-regulated (Fig. 6A), indicating the impaired cellular self-protective response in bladder cancer cells after AATBC depletion. Furthermore, the treatment with the inhibitor of JNK (SP600125) could enhance the expression level of NRF2 (Fig. 6B) and improve the cell adaptive ability to compensate the stress condition, indicating a potential link between JNK activation and NRF2 inhibition. Collectively, these results demonstrated that apoptosis after AATBC knockdown might be mediated by the activation of JNK signaling and suppression of NRF2.


Knockdown of a novel lincRNA AATBC suppresses proliferation and induces apoptosis in bladder cancer.

Zhao F, Lin T, He W, Han J, Zhu D, Hu K, Li W, Zheng Z, Huang J, Xie W - Oncotarget (2015)

The involvement of JNK and NRF2 pathway in apoptosis induced by AATBC knockdownA. 36 hours after transfection, levels of JNK, p-JNK, p-p38, p-ERK1/2 and NRF2 were determined by Western blotting analysis. β-tubulin served as loading control. B. Indicated cell lines were treated with transfection and SP600125 for 36 hours. The levels of p-JNK, NRF2, caspase-9, caspase-3 and PARP were evaluated. β-tubulin served as loading control. C. 36 hours after treatment of transfection and SP600125, flow cytometric analysis showed that JNK inhibitor SP600125 could protect UM-UC-3 and EJ cells from apoptosis. Data was represented as means ± SD. *P <0.05 (vs. control).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 6: The involvement of JNK and NRF2 pathway in apoptosis induced by AATBC knockdownA. 36 hours after transfection, levels of JNK, p-JNK, p-p38, p-ERK1/2 and NRF2 were determined by Western blotting analysis. β-tubulin served as loading control. B. Indicated cell lines were treated with transfection and SP600125 for 36 hours. The levels of p-JNK, NRF2, caspase-9, caspase-3 and PARP were evaluated. β-tubulin served as loading control. C. 36 hours after treatment of transfection and SP600125, flow cytometric analysis showed that JNK inhibitor SP600125 could protect UM-UC-3 and EJ cells from apoptosis. Data was represented as means ± SD. *P <0.05 (vs. control).
Mentions: In view of the evidence that the MAPKs, consisting of ERK1/2, JNK and p38, play critical roles in apoptosis, we examined the activation of MAPK pathway to further uncover the underlying mechanisms for the alterations of apoptosis in UM-UC-3 and EJ cells after transfection with siRNAs. As revealed by Western blotting (Fig. 6A), knockdown of AATBC enhanced the phosphorylation level of JNK in both UM-UC-3 and EJ cells. In contrast, the expression levels of phosphorylated ERK1/2 and p38 were not obviously changed upon the treatment of AATBC knockdown. JNK-mediated apoptosis can occur through multiple pathways, including oxidative stress (OS) pathway [18]. Inspired by this, we detected the factors in OS pathway. In this study, besides the activation of JNK, we found that the expression level of NRF2, a key antioxidant transcription factor in OS pathway, was down-regulated (Fig. 6A), indicating the impaired cellular self-protective response in bladder cancer cells after AATBC depletion. Furthermore, the treatment with the inhibitor of JNK (SP600125) could enhance the expression level of NRF2 (Fig. 6B) and improve the cell adaptive ability to compensate the stress condition, indicating a potential link between JNK activation and NRF2 inhibition. Collectively, these results demonstrated that apoptosis after AATBC knockdown might be mediated by the activation of JNK signaling and suppression of NRF2.

Bottom Line: We also found that inhibition of AATBC resulted in cell proliferation arrest through G1 cell cycle mediated by cyclin D1, CDK4, p18 and phosphorylated Rb.Furthermore, JNK inhibitor SP600125 could attenuate the apoptotic effect achieved by AATBC knockdown, confirming the involvement of JNK signaling in the induced apoptosis.Moreover, mouse xenograft model revealed that knockdown of AATBC led to suppress tumorigenesis in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Urology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.

ABSTRACT
Long intergenic noncoding RNAs (lincRNAs) play important roles in regulating various biological processes in cancer, including proliferation and apoptosis. However, the roles of lincRNAs in bladder cancer remain elusive. In this study, we identified a novel lincRNA, which we termed AATBC. We found that AATBC was overexpressed in bladder cancer patient tissues and positively correlated with tumor grade and pT stage. We also found that inhibition of AATBC resulted in cell proliferation arrest through G1 cell cycle mediated by cyclin D1, CDK4, p18 and phosphorylated Rb. In addition, inhibition of AATBC induced cell apoptosis through the intrinsic apoptosis signaling pathway, as evidenced by the activation of caspase-9 and caspase-3. The investigation for the signaling pathway revealed that the apoptosis following AATBC knockdown was mediated by activation of phosphorylated JNK and suppression of NRF2. Furthermore, JNK inhibitor SP600125 could attenuate the apoptotic effect achieved by AATBC knockdown, confirming the involvement of JNK signaling in the induced apoptosis. Moreover, mouse xenograft model revealed that knockdown of AATBC led to suppress tumorigenesis in vivo. Taken together, our study indicated that AATBC might play a critical role in pro-proliferation and anti-apoptosis in bladder cancer by regulating cell cycle, intrinsic apoptosis signaling, JNK signaling and NRF2. AATBC could be a potential therapeutic target and molecular biomarker for bladder cancer.

Show MeSH
Related in: MedlinePlus