Sodium butyrate induced keratinocyte apoptosis

Apoptosis of keratinocytes is a key mechanism required for epidermal homeostasis and the renewal of damaged cells. Its dysregulation has been implicated in many skin diseases including cancer and hyperproliferative disorders. In the present study, the effect of sodium butyrate, a histone deacetylase inhibitor, on keratinocyte apoptosis was investigated using the HaCaT human keratinocyte cell line. Sodium butyrate induced morphological changes associated with apoptosis and nuclear fragmentation of HaCaTs. Annexin V staining demonstrated that sodium butyrate induced apoptosis in a dose and time-dependent manner with 50% of HaCaTs apoptotic after exposure to 0.8 mg/ml sodium butyrate for 24 h. Apoptosis was associated with upregulation of cell surface expression of the death receptor Fas and activation of the extrinsic caspase pathway, with induction of caspase 8 activity peaking after 8 h. Caspase 3 activity peaked after 24 h and was associated with cleavage of the caspase 3 substrate, poly (ADP-ribose) polymerase (PARP). The intrinsic caspase pathway was not activated as caspase 9 activity was not detected, and there was no change in the expression of terminal differentiation markers keratin 10 and involucrin following sodium butyrate treatment. Together these results indicate that sodium butyrate is a potent inducer of Fas associated apoptosis via caspase activation in HaCaT keratinocytes, an effect that is independent of the induction of terminal differentiation.     

Wogonin induces apoptosis by suppressing E6 and E7 expressions and activating intrinsic signaling pathways in HPV-16 cervical cancer cells

Wogonin is a flavonoid compound extracted from Scutellaria baicalensis and is well known as a benzodiazepine receptor ligand with anxiolytic effects. Many recent studies have demonstrated that wogonin modulates angiogenesis, proliferation, invasion, and tumor progress in various cancer tissues. We further explored the mechanism of action of wogonin on cervical cancer cells that contain or lack human papillomavirus (HPV) DNA. Wogonin was cytotoxic to HPV 16 (+) cervical cancer cells, SiHa and CaSki, but not to HPV-negative cells. We demonstrated that wogonin induced apoptosis by suppressing the expressions of the E6 and E7 viral oncogenes in HPV-infected cervical cancer CaSki and SiHa cells. The modulation of p53 and protein retinoblastoma (pRb) were also triggered by the suppression of E6 and E7 expressions. However, p53 was not altered in HPV-negative cervical cancer C33A cells. Moreover, wogonin modulated the mitochondrial membrane potential and the expression of pro- and anti-apoptotic factors such as Bax and Bcl-2. Wogonin also provoked the cleavage of caspase-3, caspase-9, and poly ADP ribose polymerase. After transfection of siRNAs to target E6 and E7, additional restoration of p53 and pRb was not induced, but processing of caspases and PARP was increased compared with wogonin treatment alone. Together, our findings demonstrated that wogonin effectively promotes apoptosis by downregulating E6 and E7 expressions and promoting intrinsic apoptosis in human cervical cancer cells.     

Efficacy of TRAIL treatment against HPV16 infected cervical cancer cells undergoing senescence following siRNA knockdown of E6/E7 genes

In this study we investigated E6 and E7 oncogenes from the Human Papilloma Virus as targets for siRNA knockdown in order to boost the efficacy of the anti-cancer drug ‘tumor necrosis factor-related apoptosis inducing ligand’ (TRAIL). SiHa cells were treated with TRAIL following transfection with E6/E7 siRNA and the expression of death receptors DR4 and DR5, cell viability, apoptosis, senescence and cell cycle analysis were undertaken using flow cytometry, MTT viability assay and cellular β-galactosidase activity assays. E6/E7 siRNA resulted in significant upregulation of death receptors DR4 and DR5 but did not result in an enhanced sensitivity to TRAIL. Our results indicate that E6/E7-siRNA induces senescence rather than apoptosis in SiHa cells. The occurrence of senescence in drug resistant cervical cancer cells such as the SiHa cell line by E6/E7 siRNA, among other factors, may prevent TRAIL induced activation of extrinsic and intrinsic pathways that lead to apoptotic cell death. Our findings are significant for combinatorial strategies for cancer therapy since the induction of senescence can preclude apoptosis rendering cells to be recalcitrant to TRAIL treatment.     

Selective cytotoxicity of Aniba rosaeodora essential oil towards epidermoid cancer cells through induction of apoptosis

Essential oils are complex mixtures of odorous and volatile compounds derived from secondary plant metabolism. They can be isolated from many plants by mechanical pressing or hydro- and steam-distillation and are known to induce a wide range of biological effects through their antibacterial, antifungal, cytotoxic, antioxidant and antimutagenic activities. In order to explore their beneficial properties on human skin cells, we investigated the effects of an essential oil from rosewood Aniba rosaeodora (REO) on the human epidermoid carcinoma cell line A431, on immortal HaCaT cells thought to represent an early stage of skin carcinogenesis, on transformed normal HEK001 keratinocytes and on primary normal NHEK keratinocytes. In a defined range of concentrations, REO selectively killed A431 and HaCaT cells. The same treatments had only a minor cytotoxic effect on HEK001 and NHEK cells. Preferentially in A431 and HaCaT cells, REO triggered the production of reactive oxygen species, induced depolarization of the mitochondrial membrane and caused caspase-dependent cell death characterized by phosphatidylserine externalization, an early marker of apoptosis. Both intrinsic and extrinsic apoptotic pathways were implicated in REO-induced cell death. The identification of selective induction of apoptosis in precancerous and cancerous skin cells by REO highlights the potential anticancer activity of this essential oil.     

Extinction of the HPV18 upstream regulatory region in cervical carcinoma cells after fusion with non-tumorigenic human keratinocytes under non-selective conditions.

'Universal fuser' clones of a human papillomavirus type 16 positive cervical carcinoma cell line (SiHa) were established to study the effect of a non-tumorigenic fusion partner on the regulation of a stably integrated chloramphenicol acetyltransferase (CAT) gene controlled by the HPV18 upstream regulatory region under non-selective conditions. The CAT expressing cells were fused with both non-tumorigenic, spontaneously immortalized human keratinocytes (HaCaT) and non-modified SiHa cells. The resulting hybrids were characterized by restriction enzyme fragment length polymorphism analysis and flow cytometry. While the non-selectable, HPV18-driven indicator gene is constitutively expressed in SiHa cells, the CAT activity is extinguished in SiHa x HaCaT cells, but still present in SiHa x SiHa hybrids. Examination of the cytokeratin expression pattern reveals that the keratinocyte phenotype seems not only to be dominant in terms of the extinction of the HPV18 regulatory region but also by the conservation of most of the differentiation markers of the non-tumorigenic fusion partner. Cycloheximide treatment and intracellular competition experiments using the transient COS7 fusion-amplification technique are accompanied by the reactivation of the marker gene in previously CAT- SiHa x HaCaT hybrids. These data strongly suggest that trans-acting negative regulatory factors derived from the non-malignant human keratinocytes are responsible for the extinction phenomenon.     

Caffeine promotes ultraviolet B-induced apoptosis in human keratinocytes without complete DNA repair

In response to ultraviolet B damage, keratinocytes undergo apoptosis to eliminate damaged cells, thereby preventing tumorigenic transformation. Caffeine, the most widely consumed psychoactive substance, produces complex pharmacological actions; it has been shown to be chemopreventive in non-melamona skin cancer in mice through increasing apoptosis. Here we have investigated the molecular and cellular mechanisms in the pro-apoptotic effect of caffeine on UVB-irradiated human HaCaT keratinocytes. Pretreatment with caffeine increased UVB-induced apoptosis in HaCaT cells. Caffeine blocked UVB-induced Chk1 phosphorylation. In addition, similar to the effect of the PI3K inhibitor LY294002, caffeine also inhibited phosphorylation of AKT and up-regulation of COX-2, two critical oncogenic pathways in skin tumorigenesis. However, phosphorylation of EGFR or ERK was unaffected. Inhibiting ATR pathways by siRNA targeting ATR had little effect on UVB-induced apoptosis or AKT activation, indicating that the inhibitory effect of caffeine on apoptosis and the AKT pathway does not require the ATR pathway. Inhibiting AKT by caffeine blocked UVB-induced COX-2 up-regulation. Expression of constitutively active AKT that was not inhibited by caffeine was found to protect cells from caffeine-promoted apoptosis post-UVB irradiation, indicating that AKT is an essential inhibitory target for caffeine to promote apoptosis. Caffeine specifically sensitized cells with unrepaired DNA damage to UVB-induced apoptosis. These findings indicate that in HaCaT keratinocytes, inhibiting the AKT/COX-2 pathways through an ATR-independent pathway is a critical molecular mechanism by which caffeine promotes UVB-induced apoptosis of unrepaired keratinocytes for elimination.     

Restoration of p53 tumor suppressor pathway in human cervical carcinoma cells by sodium arsenite

In most cervical cancer cells, p53 and Rb are disrupted by human papillomaviruses (HPVs) E6 and E7, respectively. Restoration of p53 or Rb function by blocking E6/p53 or E7/Rb pathway might be a potential therapeutic purpose for these cancer cells. Treatment with sodium arsenite (SA) resulted in significant repression of E6 and E7 mRNA levels in SiHa cells. After E6 and E7 repression, p53 was dramatically induced and accumulated in cellular nuclei and Rb was also induced. Two p53-responsive genes, p21(waf1/cip1) and mdm2, were induced after SA treatment. Furthermore, SA also reduced the expressions of Cdc25A and cyclin B, blocked cell cycle progression at G2/M phase, and induced apoptosis in SiHa cells. SA-induced apoptosis was greatly reduced by expression of a dominant-negative mutated p53. In this study, we have first demonstrated that SA did repress E6 and E7 oncogenes, restore the p53 tumor suppressor pathway and induce apoptosis in SiHa cells. Therefore, it would be a potential strategy to promote SA as therapeutic purpose for HPV-positive cancer cells.     

Mechanism of Action of Two Flavone Isomers Targeting Cancer Cells with Varying Cell Differentiation Status

Apoptosis can be triggered in two different ways, through the intrinsic or the extrinsic pathway. The intrinsic pathway is mediated by the mitochondria via the release of cytochrome C while the extrinsic pathway is prompted by death receptor signals and bypasses the mitochondria. These two pathways are closely related to cell proliferation and survival signaling cascades, which thereby constitute possible targets for cancer therapy. In previous studies we introduced two plant derived isomeric flavonoids, flavone A and flavone B which induce apoptosis in highly tumorigenic cancer cells of the breast, colon, pancreas, and the prostate. Flavone A displayed potent cytotoxic activity against more differentiated carcinomas of the colon (CaCo-2) and the pancreas (Panc28), whereas flavone B cytotoxic action is observed on poorly differentiated carcinomas of the colon (HCT 116) and pancreas (MIA PaCa). Apoptosis is induced by flavone A in better differentiated colon cancer CaCo-2 and pancreatic cancer Panc 28 cells via the intrinsic pathway by the inhibition of the activated forms of extracellular signal-regulated kinase (ERK) and pS6, and subsequent loss of phosphorylation of Bcl-2 associated death promoter (BAD) protein, while apoptosis is triggered by flavone B in poorly differentiated colon cancer HCT 116 and MIA PaCa pancreatic cancer cells through the extrinsic pathway with the concomitant upregulation of the phosphorylated forms of ERK and c-JUN at serine 73. These changes in protein levels ultimately lead to activation of apoptosis, without the involvement of AKT.     

BF12, a Novel Benzofuran,Exhibits Antitumor Activity by Inhibiting Microtubules and the PI3K/Akt/mTOR Signaling Pathway in Human Cervical Cancer Cells

BF12 [(2E)‐3‐[6‐Methoxy‐2‐(3,4,5‐trimethoxybenzoyl)‐1‐benzofuran‐5‐yl]prop‐2‐enoic acid], a novel derivative of combretastatin A‐4 (CA‐4), was previously found to inhibit tumor cell lines, with a particularly strong inhibitory effect on cervical cancer cells. In this study, we investigated the microtubule polymerization effects and apoptosis signaling mechanism of BF12. BF12 showed a potent efficiency against cervical cancer cells, SiHa and HeLa, with IC₅₀ values of 1.10 and 1.06 μm , respectively. The cellular mechanism studies revealed that BF12 induced G2/M phase arrest and apoptosis in SiHa and HeLa cells, which were associated with alterations in the expression of the cell G2/M cycle checkpoint‐related proteins (cyclin B1 and cdc2) and alterations in the levels of apoptosis‐related proteins (P53, caspase‐3, Bcl‐2, and Bax) of these cells, respectively. Western blot analysis showed that BF12 inhibited the PI3 K/Akt/mTOR signaling pathway and induced apoptosis in human cervical cancer cells. BF12 was identified as a tubulin polymerization inhibitor, evidenced by the effective inhibition of tubulin polymerization and heavily disrupted microtubule networks in living SiHa and HeLa cells. By inhibiting the PI3 K/Akt/mTOR signaling pathway and inducing apoptosis in human cervical cancer cells, BF12 shows promise for use as a microtubule inhibitor.     

Polyphenol (-)-epigallocatechin gallate inhibits apoptosis induced by irradiation in human HaCaT keratinocytes

Green tea is a rich source of polyphenols, and (-)-epigallocatechin-3-gallate (EGCG) is a major constituent of green tea polyphenols. In the present study, we investigated the effect of EGCG on apoptosis induced by irradiation in the human keratinocytic cell line HaCaT. Irradiation by gamma-ray induced apoptosis with concomitant cleavage of caspase-3 and its in vivo substrate poly(ADP-ribose) polymerase. Treatment of cells with EGCG inhibited irradiation-induced apoptosis as detected by Hoechst staining and internucleosomal cleavage of DNA, and prevented the cleavage of these proteins by irradiation. We also found that the treatment of cells with EGCG alone suppressed cell growth and induced apoptosis in these cells. Our results suggest that EGCG inhibits irradiation-induced apoptosis by inactivating the caspase pathway in HaCaT cells. Our study also indicates that EGCG has a dual effect on the survival of these keratinocytes.     

Overexpression of LINC00037 represses cervical cancer progression by activating mTOR signaling pathway

Long non-coding RNAs have been reported to play crucial roles in tumorigenesis including cervical cancer. LINC00037 has been identified as a significant regulator in several cancers. Our study was aimed to investigate the function of LINC00037 in cervical cancer progression. LINC00037 was significantly downregulated in human cervical cancer cells (HeLa, HCC94, HT-3, Caski, and SiHa cells) compared with the ectocervical epithelial cells (End1/E6E7 cells). Overexpression of LINC00037 was able to inhibit cervical cancer cell proliferation, induce cell apoptosis, and restrain the cell migration/invasion capacity. Reversely, knockdown of LINC00037 exhibited an opposite process in vitro. mTOR has been recognized as an atypical serine/threonine kinase that is involved in regulating significant cellular functions. In our present study, we observed that the mTOR signaling pathway was strongly activated in human cervical cancer cells. Meanwhile, upregulation of LINC00037 contributed to the inactivation of mTOR signaling whereas downregulation of LINC00037 activated the pathway. Subsequently, in vivo animal models using SiHa cells were established and we proved that LINC00037 repressed cervical cancer progression via targeting the mTOR signaling pathway. All these findings implied that LINC00037 could regulate cervical cancer pathogenesis via mTOR signaling. In conclusion, a novel role of LINC00037 was manifested in cervical cancer progression.     

Human papillomavirus (HPV) oncoprotein E6 facilitates Calcineurin-Nuclear factor for activated T cells 2 (NFAT2) signaling to promote cellular proliferation in cervical cell carcinoma

The calcineurin-NFAT signaling pathway regulates cell proliferation, differentiation, and development in diverse cell types and organ systems. Deregulation of calcineurin-NFAT signaling has been reported in leukaemias and few solid tumors such as breast and colon. In the present study, we found elevated calcineurin protein levels and phosphatase activity in cervical cancer cell lines and depletion of the same attenuated cell proliferation. Additionally, nuclear levels of NFAT2, a downstream target of calcineurin, viz, was found elevated in human papillomavirus (HPV) infected cells, HeLa and SiHa, compared to the HPV negative cells, HaCaT and C33A, indicative of its higher DNA binding activity. The nuclear levels of both NFAT1 and NFAT3 remain unaltered implicating they have little role in cervical carcinogenesis. Similar to the in vitro studies, the HPV infected human squamous cell carcinoma specimens showed higher NFAT2 levels compared to the normal cervical epithelium. Depletion of NFAT2 by RNAi attenuated growth of SiHa cells. Overexpression of HPV16 oncoproteins viz, E6 and E7 increased NFAT2 expression levels and DNA binding activity, while knockdown of E6 by RNAi decreased the same. Briefly, we now report an activation of calcineurin-NFAT2 axis in cervical cancer and a novel role of HPV oncoprotein in facilitating NFAT2 dependent cell proliferation.     

Grape Seed Proanthocyanidins (GSPs) Inhibit the Growth of Cervical Cancer by Inducing Apoptosis Mediated by the Mitochondrial Pathway

Grape seed proanthocyanidins (GSPs), a biologically active component of grape seeds, have been reported to possess a wide array of pharmacological and biochemical properties. Recently, the inhibitory effects of GSPs on various cancers have been reported, but their effects on cervical cancer remain unclear. Here, we explored the effect of GSPs on cervical cancer using in vitro and in vivo models. In vitro, the treatment of HeLa and SiHa cells with GSPs resulted in a significant inhibition of cell viability. Further investigation indicated that GSPs led to the dose-dependent induction of apoptosis in cancer cells. The underlying mechanism was associated with increased expression of the pro-apoptotic protein Bak-1, decreased expression of the anti-apoptotic protein Bcl-2, the loss of mitochondrial membrane potential, and the activation of caspase-3, suggesting that GSPs induced cervical cancer cell apoptosis through the mitochondrial pathway. In addition, the administration of GSPs (0.1%, 0.2%, and 0.4%, w/v) as a supplement in drinking water significantly inhibited the tumor growth of HeLa and SiHa cells in athymic nude mice, and the number of apoptotic cells in those tumors was also increased significantly. Taken together, our studies demonstrated that GSPs could inhibit the growth of cervical cancer by inducing apoptosis through the mitochondrial pathway, which provides evidence indicating that GSPs may be a potential chemopreventive and/or chemotherapeutic agent for cervical cancer.     

Caspase-dependent apoptosis induced by two synthetic halogenated flavanones, 3′,7-dichloroflavanone and 3′,6-dichloroflavanone,on human breast and prostate cancer cells

The destruction of cancer cells with chemotherapeutic agents is normally achieved through apoptosis. We previously introduced two synthetic halogenated flavanone derivatives, 3^′,7-dichloroflavanone (3′-7 DCF) and 3^′,6-dichloroflavanone (3′-6 DCF), as potential apoptosis-inducing agents. In the current study, we investigated the ability of these compounds in triggering intrinsic or/and extrinsic pathway of apoptosis in breast and prostate cancer cells. Also, the synergistic effect of 3′-7 DCF with TLR3 (Toll-like receptor 3) agonist in apoptosis induction was evaluated on PC3 and LNCaP human prostate cancer cells. The involved pathway of apoptosis in the treated cells was delineated by caspase-3 activity assay, PARP-1 (poly(ADP-ribose)polymerase-1) cleavage, and procaspase-9 cleavage as markers of the intrinsic pathway and procaspase-8 cleavage as the marker of the extrinsic pathway. With the exception of the normal cells, treatment of all cell lines with both 3′-7 DCF and 3′-6 DCF triggered the cleavage of procaspase-8 and procaspase-9. These results indicate that the intrinsic and the extrinsic pathways of apoptosis are the mechanisms of the toxicity of flavanones in these cancer cell lines. However, the cytoxicity of the compound 3′-7 DCF was not synergistic with TLR3 agonist. Interestingly, the activation of caspases-9 preceeded that of caspase-8 suggesting that the intrinsic pathway is the primary reason for apoptosis induction by the flavanones.     

Cisplatin restores p53 function and enhances the radiosensitivity in HPV16 E6 containing SiHa cells

Most HPV-positive cervical cancer cells possess wild type p53 gene, but its normal p53 functions are disrupted by expression of HPVs E6. Treatment with 0-20 microM cisplatin for 24 h in HPV16 E6 containing SiHa cells suppressed E6 mRNA, reduced E6 protein, and restored p53 expression in dose-dependent manners. Dual-parameter flow cytometric analysis indicated that sub-G(1) apoptotic cells, but not necrotic cells were the major species for cisplatin-induced cytotoxicity in SiHa cells. After 0-10 microM cisplatin treatment, slightly more apoptotic cells appeared from SiHa cells than those from dominant negative p53-transfected SiHa cells. There was no different ionizing radiation (IR)-induced apoptosis in these two different cells. On the other hand, cisplatin enhanced more IR-induced sub-G(1) apoptosis in SiHa than mp53-SiHa cells. These accompanied with prolonged p53 restoration in irradiated-SiHa cells after 24 h cisplatin treatment and thereafter. In contrast, it was not found in cells after irradiation alone. Similar results were also shown in Mdm2 expression in SiHa cells after combined treatment. Therefore, cisplatin restored p53 expression and prolonged IR-induced p53 restoration would be possible candidates to response more sub-G(1) apoptosis in irradiated SiHa cells. These results provided another new explanation on cisplatin sensitizing radiotherapy for HPV16 E6 containing cancer cells.     

Apoptotic signaling induced by benzamide riboside: an in vitro study

Benzamide riboside (BR) is a novel anticancer agent exhibiting potent cytotoxic activity in malignant cell lines. However, the mechanism of induction of apoptosis is not clear. The purpose of this study was to elucidate the apoptotic signaling induced by BR on different human cancer cell lines. Our results revealed that BR at a dose of 50 μM induces apoptosis in SiHa, Hep2, and Ca Ski cells as studied by morphology and flow cytometry. A downregulation of anti-apoptotic proteins Bcl-2 and Bcl-xL was observed, whereas the expression level of the pro-apoptotic protein Bax remained unaffected. An upregulation of p53 was observed while no change was seen on the level of apoptosis inducing factor (AIF). A significant increase in caspase-3 and -9 activities was seen, which was accompanied by PARP cleavage. Release of cytochrome c from the mitochondria to the cytosol was also observed. Taken together, the findings suggest that BR induces apoptosis in SiHa, Hep2, and Ca Ski cells via the intrinsic mitochondrial pathway.     

The human papillomavirus type 16 E5 protein impairs TRAIL- and FasL-mediated apoptosis in HaCaT cells by different mechanisms

The effect of the human papillomavirus type 16 (HPV-16) E5 protein on apoptosis was investigated by using the polyclonal HaCaT-cell lines stably transfected either with E5 (HaCaT/E5) or the empty vector (HaCaT/pMSG) as reference. Apoptosis was triggered either by Fas ligand (FasL) or by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and was monitored by detection of cleavage of procaspase-8 and procaspase-3, as well as their substrate poly(ADP-ribose) polymerase (PARP). In contrast to the HaCaT/pMSG control cells we found that apoptosis induced by either of the two ligands is strongly suppressed in the E5-expressing keratinocytes. Fas expression is reduced by about a factor of two in HaCaT/E5 cells, which could be part of the mechanisms that protect the cells from FasL-induced apoptosis. For the TRAIL receptors, no such downregulation was observed. Here, E5 impairs the formation of the death-inducing signaling complex triggered by TRAIL. Apparently, E5 employs different mechanisms to inhibit death receptor signaling. This effect is not restricted to HaCaT/E5 cells since we found that the mouse fibroblast cell line A31-E5 is protected from TRAIL-induced apoptosis, as well but not the E5-lacking control cells A31-Neo. However, no such protection was observed upon FasL-induced apoptosis. Presumably, some of the antiapoptotic mechanisms employed by E5 of the human pathogenic HPV-16 are cell type specific. We propose that inhibition of ligand-mediated apoptosis in human keratinocytes is a primary function of the HPV-16 E5 protein needed to prevent apoptosis at early stages of viral infection.     

Activation of Cdc2 contributes to apoptosis in HPV E6 expressing human keratinocytes in response to therapeutic agents

Infection with human papillomaviruses (HPV) is strongly associated with the development of cervical cancer. The HPV E6 oncogene induces apoptosis in cervical cancer precursor lesions but the mechanism is poorly understood. While it is expected that inactivation of p53 by E6 should lead to a reduction in apoptosis, E6 also sensitizes cells to apoptosis under some experimental conditions. Here, we demonstrate that expression of E6 in human keratinocytes rendered sensitization to chemotherapeutic agents. The cell death was shown to be by apoptosis involving caspase activation and the mitochondria pathway. To explore mechanisms involved in sensitization of E6 expressing cells to apoptosis, we used a proteomic approach to identify proteins differentially expressed in E6 expressing and control keratinocytes. Among nearly a thousand proteins examined, Cdc2 was demonstrated to be the most dramatically up-regulated protein in E6 expressing cells. p53 degradation appears to be important for the up-regulation of Cdc2 by E6. Using genetic, pharmacologic, and siRNA strategies, a role for Cdc2 in E6 expression-conferred apoptosis was demonstrated. Thus, these results have important therapeutic implications in enhancing the efficacy of chemotherapy.     

Artematrolide A inhibited cervical cancer cell proliferation via ROS/ERK/mTOR pathway and metabolic shift

BackgroundArtematrolide A (AR-A), a guaianolide dimer isolated from Artemisia atrovirens, demonstrated significant inhibitory effect on three human hepatoma cell lines (HepG2, Huh7 and SMMC7721). The anti-cervical cancer effect and mechanism of this compound have yet to be explored. This study is to reveal the role and mechanisms of artematrolide A on cervical cancer cells, and provide the pharmacological understanding of artematrolide A.PurposeTo investigate the function and possible mechanism of artematrolide A on cervical cancer cells in vitro.MethodsHeLa S3 and SiHa cells were treated with artematrolide A at various concentrations. In this study, MTT, colony formation, cell migration and invasion, cell cycle analysis, cell apoptosis, reactive oxygen species (ROS) detection, western blotting, enzyme activity, and lactate production of artematrolide A were evaluated.ResultsArtematrolide A inhibited cell viability, proliferation, migration and invasion in a dose-dependent manner, caused cell cycle arrest in G2/M phase, and induced cell apoptosis via Bcl-2/PARP-1. The mechanism of action of artematrolide A included two aspects: artematrolide A suppressed cell proliferation by activating ROS/ERK/mTOR signaling pathway and promoted glucose metabolism from aerobic glycolysis to mitochondrial respiration by activating pyruvate dehydrogenase complex (PDC) and oxoglutarate dehydrogenase complex (OGDC) via inhibiting the activity of alkaline phosphatases (ALP).ConclusionArtematrolide A exhibited a significant cytotoxic activity on cervical cancer cells, induced G2/M cell cycle arrest and apoptosis by activating ROS/ERK/mTOR signaling pathway and promoting metabolic shift from aerobic glycolysis to mitochondrial respiration, which suggested artematrolide A might be a potential agent for the treatment of cervical cancer.