Hepatoprotective role of Sestrin2 against chronic ER stress

Upon prolonged endoplasmic reticulum (ER) stress, cells attenuate protein translation to prevent accumulation of unfolded proteins. Here we show that Sestrin2 is critical for this process. Sestrin2 expression is induced by an ER stress-activated transcription factor CCAATenhancer- binding protein beta (c/EBPβ). Once induced, Sestrin2 halts protein synthesis by inhibiting mammalian target of rapamycin complex 1 (mTORC1). As Sestrin2-deficient cells continue to translate a large amount of proteins during ER stress, they are highly susceptible to ER stress-associated cell death. Accordingly, dietary or genetically induced obesity, which does not lead to any pathological indication other than simple fat accumulation in the liver of wild-type (WT) mice, can provoke Sestrin2-deficient mice to develop severe ER stressassociated liver pathologies such as extensive liver damage, steatohepatitis and fibrosis. These pathologies are suppressed by liver-specific Sestrin2 reconstitution, mTORC1 inhibition or chemical chaperone administration. The Sestrin2-mediated unfolded protein response (UPR) may be a general protective mechanism against ER stress-associated diseases

Hepatoprotective role of Sestrin2 against chronic ER stress

Upon prolonged endoplasmic reticulum (ER) stress, cells attenuate protein translation to prevent accumulation of unfolded proteins. Here we show that Sestrin2 is critical for this process. Sestrin2 expression is induced by an ER stress-activated transcription factor CCAATenhancer- binding protein beta (c/EBPβ). Once induced, Sestrin2 halts protein synthesis by inhibiting mammalian target of rapamycin complex 1 (mTORC1). As Sestrin2-deficient cells continue to translate a large amount of proteins during ER stress, they are highly susceptible to ER stress-associated cell death. Accordingly, dietary or genetically induced obesity, which does not lead to any pathological indication other than simple fat accumulation in the liver of wild-type (WT) mice, can provoke Sestrin2-deficient mice to develop severe ER stressassociated liver pathologies such as extensive liver damage, steatohepatitis and fibrosis. These pathologies are suppressed by liver-specific Sestrin2 reconstitution, mTORC1 inhibition or chemical chaperone administration. The Sestrin2-mediated unfolded protein response (UPR) may be a general protective mechanism against ER stress-associated diseases

Berberine Suppresses Cell Motility Through Downregulation of TGF-β1 in Triple Negative Breast Cancer Cells

Background/Aims: Transforming growth factor-beta proteins (TGF-βs) are multifunctional growth factors and powerful modulators of the epithelial-mesenchymal transition (EMT) in a variety of cancer types including breast and lung cancer cells. Here, we demonstrated the inhibitory effect of berberine (BBR) on tumor growth and metastasis of triple negative breast cancer (TNBC) cells via suppression of TGF-β1 expression. Methods: The levels of mRNA expression were analyzed by real-time PCR. The levels of MMP-2, MMP-9 and TGF-β1 protein expression were analyzed by zymography and confocal microscopy, respectively. Cell migration was analyzed by wound healing assay. Tumorigenicity of TNBC cells such as tumor growth and metastasis was analyzed using xenograft models. Results: In a clinical data set, aberrant TGF-β1 expression was associated with poor prognosis of breast cancer patients. Our in vitro results using TNBC cells showed that the expression levels of matrix metalloproteinase (MMP)-2 and MMP-9 and the capacity for cell migration were increased by TGF-β1 treatment. In contrast, basal levels of MMP-2 and MMP-9 were suppressed by a specific TGF-β receptor I inhibitor, SB431542. In addition, TGF-β1–induced MMP-2 and MMP-9 expression and cell migration were decreased by SB431542. Interestingly, we showed for the first time that BBR decreased the level of TGF-β1, but not TGF-β2, in TNBC cells. Furthermore, BBR significantly decreased the level of MMP-2 expression as well as the capacity for cell migration in TNBC cells. Finally, we examined the effect of BBR on in vivo tumor growth and lung metastasis in MDA-MB231 and 4T1 breast cancer xenograft models and showed that both were significantly decreased following BBR treatment. Conclusion: BBR suppresses tumorigenicity of TNBC cells through inhibition of TGF-β1 expression. Therefore, we demonstrate that BBR could be a promising drug for treatment of TNBC

Berberine Suppresses TPA-Induced Fibronectin Expression through the Inhibition of VEGF Secretion in Breast Cancer Cells

Background/Aims: Berberine (BBR) is an isoquinoline alkaloid and is beneficial for the anticancer effect on a variety of human tumor cells. However, BBR's anti-angiogenesis property and its clinical potential as an inhibitor of tumor angiogenesis in breast cancer cells have not been fully elucidated. Here, we investigated the effect of BBR on TPA-induced VEGF and fibronectin (FN) as well as VEGF-induced FN in breast cancer cells. Methods: The secretion of VEGF protein was detected by ELISA. Fibronectin mRNA and protein expression was analyzed by Real-Time PCR and western blotting, respectively. The overexpressions of CA-MEK, and CA-Akt were examined by adenovirus system. Results: Our results showed that TPA, a tumor promoter, significantly increased the level of VEGF and FN expression in both MCF7 and T47D breast cancer cells. On the other hand, TPA-induced VEGF and FN expression was suppressed by LY294002, a PI-3K inhibitor. In contrast, the level of FN expression also significantly increased by constitutively active (CA)-AKT overexpression. We also found that TPA-induced VEGF and FN expression was decreased by BBR treatment. Finally, our results showed that VEGF augmented the expression of FN whereas VEGF-induced FN expression was decreased by BBR treatment. Conclusion: Taken together, we suggest that BBR may suppress TPA-induced VEGF and FN as well as VEGF-induced FN through the inhibition of the PI-3K/AKT pathway in breast cancer cells. Therefore, we suggest that BBR may be used as a candidate drug for the inhibition of angiogenesis of human breast cancer