Huixin Yu

Apigenin induces autophagic cell death in human papillary thyroid carcinoma BCPAP cells

Apigenin, abundantly present in fruits and vegetables, is recognized as a flavonoid with anti-inflammatory, antioxidant and anticancer properties. In this study, we first investigated the anti-neoplastic effects of apigenin on papillary thyroid carcinoma (PTC) cell line BCPAP cells. Our results show that apigenin inhibited the viability of BCPAP cells in a dose-dependent manner. A large body of evidence demonstrates that autophagy contributes to cell death in certain contexts. In the present study, autophagy was induced by apigenin treatment in BCPAP cells, as evidenced by Beclin-1 accumulation, conversion of LC3 protein, p62 degradation as well as the significantly increased formation of acidic vesicular organelles (AVOs) compared to the control group. 3-MA, an autophagy inhibitor, rescued the cells from apigenin-induced cell death. Notably, apigenin enhanced production of reactive oxygen species (ROS), and subsequent induction of significant DNA damage as monitored by the TUNEL assay. In addition, apigenin treatment caused a significant accumulation of cells in the G2/M phase via down-regulation of Cdc25C expression. Our findings reveal that apigenin inhibits papillary thyroid cancer cell viability by the stimulation of reactive oxygen species (ROS) production, induction of DNA damage, leading to G2/M cell cycle arrest followed by autophagic cell death. Thus, our results provide new insights into the molecular mechanisms underlying apigenin-mediated autophagic cell death and suggest apigenin as a potential chemotherapeutic agent which is able to fight against papillary thyroid cancer.

Disruption of chaperone-mediated autophagy-dependent degradation of MEF2A by oxidative stress-induced lysosome destabilization

Oxidative stress has been implicated in both normal aging and various neurodegenerative disorders and it may be a major cause of neuronal death. Chaperone-mediated autophagy (CMA) targets selective cytoplasmic proteins for degradation by lysosomes and protects neurons against various extracellular stimuli including oxidative stress. MEF2A (myocyte enhancer factor 2A), a key transcription factor, protects primary neurons from oxidative stress-induced cell damage. However, the precise mechanisms of how the protein stability and the transcriptional activity of MEF2A are regulated under oxidative stress remain unknown. In this study, we report that MEF2A is physiologically degraded through the CMA pathway. In pathological conditions, mild oxidative stress (200 μM H2O2) enhances the degradation of MEF2A as well as its activity, whereas excessive oxidative stress (> 400 μM H2O2) disrupts its degradation process and leads to the accumulation of nonfunctional MEF2A. Under excessive oxidative stress, an N-terminal HDAC4 (histone deacetylase 4) cleavage product (HDAC4-NT), is significantly induced by lysosomal serine proteases released from ruptured lysosomes in a PRKACA (protein kinase, cAMP-dependent, catalytic, α)-independent manner. The production of HDAC4-NT, as a MEF2 repressor, may account for the reduced DNA-binding and transcriptional activity of MEF2A. Our work provides reliable evidence for the first time that MEF2A is targeted to lysosomes for CMA degradation; oxidative stress-induced lysosome destabilization leads to the disruption of MEF2A degradation as well as the dysregulation of its function. These findings may shed light on the underlying mechanisms of pathogenic processes of neuronal damage in various neurodegenerative-related diseases.

Curcumin inhibits metastasis in human papillary thyroid carcinoma BCPAP cells via down-regulation of the TGF-β/Smad2/3 signaling pathway

Thyroid cancers usually possess a good prognosis while the risks of recurrence and metastasis turn out to be a disturbing issue. Curcumin [bis(4-hydroxy-3-methoxy-phenyl)-1,6-heptadiene-3,5-dione] is a natural polyphenolic compound mainly found in turmeric (Curcuma longa). Our previous studies have demonstrated that curcumin showed proliferation-inhibitory and apoptosis-inducing effects on K1 papillary thyroid cancer cells. However, the mechanism underlying the inhibition effects of curcumin on thyroid cancer cells remains unclear. Herein, we demonstrated that curcumin remarkably increased the expression of the epithelial marker E-cadherin and repressed the expression of the mesenchymal marker vimentin in human papillary thyroid carcinoma BCPAP cells. Curcumin also suppressed multiple metastatic steps of BCPAP cells, including cell attachment, spreading as well as migration. In addition, the transcription, secretion and activation of matrix metalloproteinases (MMPs) induced by transforming growth factor-β1 (TGF-β1) in BCPAP cells were mitigated upon curcumin treatment. Further evidence showed that curcumin decreased TGF-β1-mediated phosphorylation of Smad2 and Smad3. These results revealed that curcumin inhibited the TGF-β1-induced epithelial-mesenchymal transition (EMT) via down-regulation of Smad2/3 signaling pathways. Our findings provide new evidence that the anti-metastatic and anti-EMT activities of curcumin may contribute to the development of chemo-preventive agents for thyroid cancer treatment.

Punicalagin induces apoptosis-independent autophagic cell death in human papillary thyroid carcinoma BCPAP cells

Thyroid cancer is the most common endocrine carcinoma with increased incidence worldwide. Punicalagin is a tannin in pomegranate and contributes to a variety of physiological and pathological processes including inflammation, immunity and cancer. However, the exact role of punicalagin played in thyroid cancer treatment has not been elucidated yet. Our study shows that punicalagin decreased the viability of thyroid cancer cell line BCPAP. Punicalagin treatment did not influence the nuclear fragmentation or chromatin condensation and cell cycle distribution of BCPAP cells. Besides, no caspase-3 and PARP cleavage was observed after punicalagin treatment. These characteristics integrally indicated that punicalagin initiated a non-apoptotic cell death in BCPAP cells. Autophagy is a response of cancer cells to various anticancer therapies. In the present study, punicalagin treatment resulted in marked autophagy induction as evidenced by an increase in LC3-II conversion and beclin-1 expression, and increased in p62 degradation. In addition, punicalagin-induced cell death was significantly inhibited by autophagy inhibitors 3-methyladenine. Moreover, the punicalagin activates the MAPK and inhibits the mTOR signaling pathways to promote the process of autophagy. Taken together, our results provide evidences for the antitumor effect of punicalagin which is considerably linked to its ability to induce autophagic cell death.

Curcumin induces cell death of human papillary thyroid carcinoma BCPAP cells through endoplasmic reticulum stress

Curcumin, a major active component of Curcuma longa, is a natural polyphenolic antioxidant compound which has a strong potential for cancer prevention and treatment. However, the effect of curcumin on papillary thyroid carcinoma cells has not been investigated. In the present study, we report that curcumin induces cell death of papillary thyroid carcinoma (PTC) cell line BCPAP cells through endoplasmic reticulum (ER) stress. Curcumin suppressed cell viability of BCPAP cells in a dose-dependent manner. A large body of evidence demonstrates that ER stress contributes to cell death in certain contexts. ER stress was induced by curcumin treatment in BCPAP cells, as evidenced by the up-regulation of intracellular calcium level, and up-regulated expression of CCAAT/enhancer binding protein homologous protein (CHOP) at both mRNA and protein levels compared to the control group. Moreover, the activation of activating transcription factor 6 (ATF6)/X-box binding protein-1 (XBP-1) pathways could be involved in the ER stress signaling of curcumin treatment. Thus, our results provide new insights into the molecular mechanisms of curcumin-mediated cell death in PTC cells and suggest curcumin might be a potential chemotherapeutic agent which is able to fight against papillary thyroid cancer.

Induction of Apoptosis in Human Papillary-Thyroid-Carcinoma BCPAP Cells by Diallyl Trisulfide through Activation of the MAPK Signaling Pathway

This study aimed to elucidate the potential effects of diallyl trisulfide (DATS) on human papillary-thyroid-carcinoma BCPAP cells and its underlying mechanisms. DATS is an organosulfur compound derived from garlic. In this study, we demonstrated that compared with the solvent control, DATS treatment at concentrations of 5, 10, and 20 μΜ decreased cell survival rates of BCPAP cells to 84.51 ± 2.67, 57.16 ± 1.18, and 41.22 ± 1.19% respectively. DATS also caused cell-cycle arrest at G0/G1 phase, and the proportion of cells arrested in G0/G1 phase rose from 68.8 ± 8.38 to 80.4 ± 8.38%, which eventually resulted in cell apoptosis through a mitochondrial apoptotic pathway in BCPAP cells. Further evidence showed that DATS activated ERK, JNK, and p38, members of the MAPK family. Moreover, ERK and JNK inhibitors partially reversed apoptosis in BCPAP cells induced by DATS treatment. Taken together, our results demonstrated that DATS exerted an apoptosis-inducing effect on papillary-thyroid-cancer cells via activation of the MAPK signaling pathway, which shed light on a prospective therapeutic target for thyroid-cancer treatment.

Punicalagin from pomegranate promotes human papillary thyroid carcinoma BCPAP cell death by triggering ATM-mediated DNA damage response

Punicalagin (PUN), a component derived from pomegranate, is well known for its anticancer activity. Our previous work revealed that PUN induces autophagic cell death in papillary thyroid carcinoma cells. We hypothesized that PUN triggers DNA damage associated with cell death because DNA damage was reported as an inducer of autophagy. Our results showed that PUN treatment caused DNA breaks as evidenced by the significant enhancement in the phosphorylation of H2A.X. However, reactive oxygen species and DNA conformational alteration, 2 common inducing factors in DNA damage, were not involved in PUN-induced DNA damage. The phosphorylation of ataxia-telangiectasia mutated gene-encoded protein (ATM) but not ataxia telangiectasia and Rad3-related protein (ATR) was up-regulated in a time- and dosage-dependent manner after PUN treatment. KU-55933, an inhibitor of ATM, inhibited the phosphorylation of ATM induced by PUN and reversed the decreased cell viability caused by PUN. Thus, we demonstrated that PUN induces cell death of papillary thyroid carcinoma cells by triggering ATM-mediated DNA damage response, which provided novel mechanisms and potential targets for the better understanding of the anticancer actions of PUN.

Rice protein hydrolysates (RPHs) inhibit the LPS-stimulated inflammatory response and phagocytosis in RAW264.7 macrophages by regulating the NF-κB signaling pathway

The antioxidant and anti-hypertension properties of rice peptides following hydrolysis by proteolytic enzymes have been investigated previously, but the anti-inflammatory and immune characteristics have not been fully explored. In this study, we investigated the inhibitory effects of trypsin-derived rice protein hydrolysates (RPHs) on the inflammatory response in LPS-stimulated RAW264.7 macrophages, and probed their underlying molecular mechanisms of action. Moreover, a fraction, RPHs-C-7-3, displayed significant inflammation suppression activity by inhibiting the release of nitric oxide (NO) and tumour necrosis factor-α (TNF-α). Transcription of TNF-α, inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), and interleukin-1β (IL-1β) were decreased in a dose-dependent manner. Additionally, RPHs-C-7-3 attenuated iNOS and repressed the nuclear transcription factor (NF-κB) signaling pathway by impeding the nuclear translocation of p65. RPHs-C-7-3 also repressed the phagocytic ability of the activated macrophages. Our results demonstrated that RPHs exerted anti-inflammatory effects in LPS-stimulated RAW264.7 macrophages and may therefore have potential for treating inflammation-related conditions.

Punicalagin induces senescent growth arrest in human papillary thyroid carcinoma BCPAP cells via NF-κB signaling pathway

Papillary thyroid carcinoma (PTC) is the most common endocrine carcinoma. Our previous study revealed that punicalagin (PUN), an active component from pomegranate, triggered autophagic cell death and DNA damage response (DDR) in papillary thyroid carcinoma BCPAP cells. But the detailed anti-cancer mechanisms of punicalagin against PTC still remained to be further explored. DDR activation is a proven cause of cellular senescence, which mediates anti-tumor processes under certain circumstances. In this study, we reported that punicalagin treatment generated a senescent phenotype of BCPAP cells characterized as altered morphology, increased cell granularity and senescence-associated β-galactosidase (SA-β-Gal) staining. Senescence induced by punicalagin treatment was further confirmed by cell cycle arrest and upregulation of cyclin-dependent kinase inhibitor p21. Meanwhile, the senescence-associated secretory phenotype (SASP) included high levels of inflammatory cytokines, principally IL-6 and IL-1β. Furthermore, punicalagin exposure caused the phosphorylation and subsequent degradation of IκBα as well as the nuclear translocation of p65, suggesting the activation of NF-κB signaling pathway. Inhibition of NF-κB by pyrrolidine dithiocarbamate (PDTC), a selective inhibitor of NF-κB, partially reversed the cellular senescent phenotype induced by punicalagin in BCPAP cells as evidenced by the decreased fraction of SA-β-Gal staining positive cells and blockage of SASP generation. These results collectively showed that punicalagin treatment induced senescent growth arrest and SASP via triggering NF-κB activation. These observations elucidated novel anti-cancer mechanisms of punicalagin and might provide new potential prospects for PTC therapy.