Activating transcription factor 4 increases chemotherapeutics resistance of human hepatocellular carcinoma

The RNA Demethylases ALKBH5 and FTO Regulate the Translation of ATF4 mRNA in Sorafenib-Treated Hepatocarcinoma Cells

Translation is one of the main gene expression steps targeted by cellular stress, commonly referred to as translational stress, which includes treatment with anticancer drugs. While translational stress blocks the translation initiation of bulk mRNAs, it nonetheless activates the translation of specific mRNAs known as short upstream open reading frames (uORFs)-mRNAs. Among these, the ATF4 mRNA encodes a transcription factor that reprograms gene expression in cells responding to various stresses. Although the stress-induced translation of the ATF4 mRNA relies on the presence of uORFs (upstream to the main ATF4 ORF), the mechanisms mediating this effect, particularly during chemoresistance, remain elusive. Here, we report that ALKBH5 (AlkB Homolog 5) and FTO (FTO: Fat mass and obesity-associated protein), the two RNA demethylating enzymes, promote the translation of ATF4 mRNA in a transformed liver cell line (Hep3B) treated with the chemotherapeutic drug sorafenib. Using the in vitro luciferase reporter translational assay, we found that depletion of both enzymes reduced the translation of the reporter ATF4 mRNA upon drug treatment. Consistently, depletion of either protein abrogates the loading of the ATF3 mRNA into translating ribosomes as assessed by polyribosome assays coupled to RT-qPCR. Collectively, these results indicate that the ALKBH5 and FTO-mediated translation of the ATF4 mRNA is regulated at its initiation step. Using in vitro methylation assays, we found that ALKBH5 is required for the inhibition of the methylation of a reporter ATF4 mRNA at a conserved adenosine (A235) site located at its uORF2, suggesting that ALKBH5-mediated translation of ATF4 mRNA involves demethylation of its A235. Preventing methylation of A235 by introducing an A/G mutation into an ATF4 mRNA reporter renders its translation insensitive to ALKBH5 depletion, supporting the role of ALKBH5 demethylation activity in translation. Finally, targeting either ALKBH5 or FTO sensitizes Hep3B to sorafenib-induced cell death, contributing to their resistance. In summary, our data show that ALKBH5 and FTO are novel factors that promote resistance to sorafenib treatment, in part by mediating the translation of ATF4 mRNA.

Immunogenic landscape and risk score prediction based on unfolded protein response (UPR)-related molecular subtypes in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is the most common type of cancer and causes a significant number of cancer-related deaths worldwide. The molecular mechanisms underlying the development of HCC are complex, and the heterogeneity of HCC has led to a lack of effective prognostic indicators and drug targets for clinical treatment of HCC. Previous studies have indicated that the unfolded protein response (UPR), a fundamental pathway for maintaining endoplasmic reticulum homeostasis, is involved in the formation of malignant characteristics such as tumor cell invasiveness and treatment resistance. The aims of our study are to identify new prognostic indicators and provide drug treatment targets for HCC in clinical treatment based on UPR-related genes (URGs).

Methods

Gene expression profiles and clinical information were downloaded from the TCGA, ICGC and GEO databases. Consensus cluster analysis was performed to classify the molecular subtypes of URGs in HCC patients. Univariate Cox regression and machine learning LASSO algorithm were used to establish a risk prognosis model. Kaplan-Meier and ROC analyses were used to evaluate the clinical prognosis of URGs. TIMER and XCell algorithms were applied to analyze the relationships between URGs and immune cell infiltration. Real time-PCR was performed to analyze the effect of sorafenib on the expression levels of four URGs.

Results

Most URGs were upregulated in HCC samples. According to the expression pattern of URGs, HCC patients were divided into two independent clusters. Cluster 1 had a higher expression level, worse prognosis, and higher expression of immunosuppressive factors than cluster 2. Patients in cluster 1 were more prone to immune escape during immunotherapy, and were more sensitive to chemotherapeutic drugs. Four key UPR genes (ATF4, GOSR2, PDIA6 and SRPRB) were established in the prognostic model and HCC patients with high risk score had a worse clinical prognosis. Additionally, patients with high expression of four URGs are more sensitive to sorafenib. Moreover, ATF4 was upregulated, while GOSR2, PDIA6 and SRPRB were downregulated in sorafenib-treated HCC cells.

Conclusion

The UPR-related prognostic signature containing four URGs exhibits high potential application value and performs well in the evaluation of effects of chemotherapy/immunotherapy and clinical prognosis.

Feedback loop between hepatocyte nuclear factor 1α and endoplasmic reticulum stress mitigates liver injury by downregulating hepatocyte apoptosis

Hepatocyte nuclear factor alpha (HNF1α), endoplasmic reticulum (ER) stress, and hepatocyte apoptosis contribute to severe acute exacerbation (SAE) of liver injury. Here, we explore HNF1α-ER stress-hepatocyte apoptosis interaction in liver injury. LO2, HepG2 and SK-Hep1 cells were treated with thapsigargin (TG) or tunicamycin (TM) to induce ER stress. Carbon tetrachloride (CCl4) was used to induce acute liver injury in mice. Low-dose lipopolysaccharide (LPS) exacerbated liver injury in CCl4-induced mice. Significant apoptosis, HNF1α upregulation, and nuclear factor kappa B (NF-κB) activation were observed in human-derived hepatocytes during ER stress. Knockdown of Rela, NF-κB p65, inhibited the HNF1α upregulation. Following CCl4 treatment ER stress, apoptosis, HNF1α expression and RelA phosphorylation were significantly increased in mice. HNF1α knockdown reduced activating transcription factor 4 (ATF4) expression, and aggravated ER stress as well as hepatocyte apoptosis in vivo and in vitro. The double fluorescent reporter gene assay confirmed that HNF1α regulated the transcription of ATF4 promoter. LPS aggravated CCl4-induced liver injury and reduced HNF1α, and ATF4 expression. Therefore, in combination, HNF1α and ER stress could be mutually regulated forming a feedback loop, which helps in protecting the injured liver by down-regulating hepatocyte apoptosis. Low-dose LPS aggravates hepatocyte apoptosis and promotes the SAE of liver injury by interfering with the feedback regulation of HNF1α and ER stress in acute liver injury.

CCDC106 promotes the proliferation and invasion of ovarian cancer cells by suppressing p21 transcription through a p53-independent pathway

Ovarian cancers are the major cause of mortality for women worldwide. This study was aimed to elucidate the biological activities of CCDC106 in the proliferation and invasion of mutant p53 and of wild-type p53 ovarian cancer cells. CAOV3 (mutant p53) cells showed high expression levels of CCDC106, but it was expressed at low levels in SKOV3 (mutant p53) and in A2780 (wild-type p53) cells. The overexpression of CCDC106 promoted the expression of proliferation markers (cyclin family members), invasion and Epithelial-to-mesenchymal transition (EMT) markers (claudin-1, claudin-4, N-cadherin, snail, slug) while the knockdown of CCDC106 inhibited their expression in mutant p53 cells but not in wild-type p53 cells. Treatment with a CK2 inhibitor blocked the translocation of CCDC106 into the nuclei of mutant p53 cells. Immunoprecipitation assays confirmed that ATF4 is a potential binding partner of CCDC106. The overexpression of CCDC106 reduced p21 and p27 protein expression levels while treatment with an ATF4 siRNA rescued their expression. The overexpression of CCDC106 promoted colony formation and invasion of mutant p53 cells, which was suppressed by treatment with an ATF4 siRNA. Immunohistochemistry results showed that CCDC106 and ATF4 are expressed at high levels but p21 is expressed at low levels in FIGO III-IV stage and in mutant p53 ovarian cancer samples. A significant association between poor overall survival and high CCDC106 and ATF4 expression levels was observed in human ovarian cancer samples. In conclusion, CCDC106 promotes proliferation, invasion and EMT of mutant p53 ovarian cancer cells via the ATF4 mediated inhibition of p21.

Therapeutic Potential of (-)-Agelamide D, a Diterpene Alkaloid from the Marine Sponge Agelas sp., as a Natural Radiosensitizer in Hepatocellular Carcinoma Models

Radiation therapy (RT) is an effective local treatment for unresectable hepatocellular carcinoma (HCC), but there are currently no predictive biomarkers to guide treatment decision for RT or adjuvant systemic drugs to be combined with RT for HCC patients. Previously, we reported that extracts of the marine sponge Agelas sp. may contain a natural radiosensitizer for HCC treatment. In this study, we isolated (−)-agelamide D from Agelas extract and investigated the mechanism underlying its radiosensitization. (−)-Agelamide D enhanced radiation sensitivity of Hep3B cells with decreased clonogenic survival and increased apoptotic cell death. Furthermore, (−)-agelamide D increased the expression of protein kinase RNA-like endoplasmic reticulum kinase/inositol-requiring enzyme 1α/activating transcription factor 4 (PERK/eIF2α/ATF4), a key pathway of the unfolded protein response (UPR) in multiple HCC cell lines, and augmented radiation-induced UPR signaling. In vivo xenograft experiments confirmed that (−)-agelamide D enhanced tumor growth inhibition by radiation without systemic toxicity. Immunohistochemistry results showed that (−)-agelamide D further increased radiation-induced ATF4 expression and apoptotic cell death, which was consistent with our in vitro finding. Collectively, our results provide preclinical evidence that the use of UPR inducers such as (−)-agelamide D may enhance the efficacy of RT in HCC management.

Activation of LXRβ inhibits proliferation, promotes apoptosis, and increases chemosensitivity of gastric cancer cells by upregulating the expression of ATF4

Recently, great advances have been achieved in both surgery and chemotherapy for the treatment of gastric cancer, but there is still poor prognosis for this disease. The aim of this study is to investigate the role of liver X receptor β (LXRβ) in chemosensitivity of gastric cancer SGC7901 cells. From 171 patients with gastric cancer, the gastric cancer and paracancerous tissues were selected to measure the expression of LXRβ and ATF4. Gastric cancer cell lines were cultured and screened to figure out the proliferation and apoptosis of gastric cancer SGC7901 cells with the treatment of LXRβ agonist (GW3965), ATF4 short hairpin RNA (shRNA), and chemotherapy drug paclitaxel. The expression of apoptosis-related gene cleaved caspase-3 was detected by Western blot analysis. First, we found that the expressions of LXRβ and ATF4 in gastric cancer tissues and cells were significantly lower than those in their paracancerous tissues and gastric mucosal epithelial cells. In addition, activation of LXRβ and paclitaxel treatment suppressed proliferation of SGC7901 cells, and the expression of ATF4 was upregulated in a concentration-dependent manner. Furthermore, shRNA significantly inhibited the expression of ATF4 and blocked the chemosensitivity of SGC7901 cells to LXRβ activation. Our study demonstrates that the expression of LXRβ was low in gastric cancer. In addition, activation of LXRβ may inhibit the proliferation of gastric cancer cells, promote apoptosis, and increase chemosensitivity by upregulating the expression of ATF4.

TLR4 increases the stemness and is highly expressed in relapsed human hepatocellular carcinoma

Toll‐like receptor 4 (TLR4) plays an essential role in cancer progress. Here, we find that the expression of TLR4 in relapsed human hepatocellular carcinoma (HCC) clinical samples is higher than that in the non‐relapsed ones, which leads us to explore the role of TLR4 in cancer stemness. We reported that TLR4‐AKT signaling pathway was activated by lipopolysaccharides (LPS) in HCC cell lines to enhance the cancer stemness capacity, which was reflected by the increased percentage of CD133⁺CD49f⁺ population and side population, enhanced sphere formation, and the upregulation of stemness marker gene‐SOX2. Downregulation of SOX2 attenuated the enhanced HCC stemness induced by LPS, indicating SOX2 as a downstream mediator of LPS‐TLR4 signaling. The role of LPS‐TLR4 signaling in inducing HCC stemness was further confirmed by tumor xenograft experiment in vivo. Taken together, our findings provide a novel therapeutic target to prevent the recurrence of HCC.

miR-885-5p suppresses hepatocellular carcinoma metastasis and inhibits Wnt/β-catenin signaling pathway

MicroRNAs (miRNAs) inhibit or improve the malignant progression of hepatocellular carcinoma (HCC). We previously reported that compared to health controls, patients with liver cirrhosis present the highest levels of circulating miR-885-5p, followed by those with chronic hepatitis B and those with HCC. However, the molecular involvement of miR-885-5p in HCC metastasis is presently unclear. Here, we demonstrated that the expression of miR-885-5p negatively correlated with the invasive and metastatic capabilities of human HCC tissue samples and cell lines. We found that miR-885-5p expression levels correlated with the survival of patients with HCC. Overexpression of miR-885-5p decreased metastasis of HCC cells in vitro and in vivo. Inhibition of miR-885-5p improved proliferation of non-metastatic HCC cells. Furthermore, we disclosed that miR-885-5p targeted gene encoding β-catenin CTNNB1, leading to decreased activity of the Wnt/β-catenin signaling pathway. The present study indicates that miR-885-5p suppresses the metastasis of HCC and inhibits Wnt/β-catenin signaling pathway by its CTNNB1 target, which suggests that miR-885-5p to be a promising negative regulator of HCC progression and as a novel therapeutic agent to treat HCC.

PSAT1 is regulated by ATF4 and enhances cell proliferation via the GSK3β/β-catenin/cyclin D1 signaling pathway in ER-negative breast cancer

Background

A growing amount of evidence has indicated that PSAT1 is an oncogene that plays an important role in cancer progression and metastasis. In this study, we explored the expression and function of PSAT1 in estrogen receptor (ER)-negative breast cancer.

Method

The expression level of PSAT1 in breast cancer tissues and cells was analyzed using real-time-PCR (RT-PCR), TCGA datasets or immunohistochemistry (IHC). The overall survival of patients with ER-negative breast cancer stratified by the PSAT1 expression levels was evaluated using Kaplan-Meier analysis. The function of PSAT1 was analyzed using a series of in vitro assays. Moreover, a nude mouse model was used to evaluate the function of PSAT1 in vivo. qRT-PCR and western blot assays were used to evaluate gene and protein expression, respectively, in the indicated cells. In addition, we demonstrated that PSAT1 was activated by ATF4 by chromatin immunoprecipitation (ChIP) assays.

Results

mRNA expression of PSAT1 was up-regulated in ER-negative breast cancer. A tissue microarray that included 297 specimens of ER-negative breast cancer was subjected to an immunohistochemistry assay, which demonstrated that PSAT1 was overexpressed and predicted a poor clinical outcome of patients with this disease. Our data showed that PSAT1 promoted cell proliferation and tumorigenesis in vitro and in vivo. We further found that PSAT1 induced up-regulation of cyclin D1 via the GSK3β/β-catenin pathway, which eventually led to the acceleration of cell cycle progression. Furthermore, ATF4 was also overexpressed in ER-negative breast cancers, and a positive correlation between the ATF4 and PSAT1 mRNA levels was observed in ER-negative breast cancers. We further demonstrated that knockdown of ATF4 by siRNA reduced PSAT1 expression. Finally, chromatin immunoprecipitation (ChIP) assays showed that PSAT1 was a target of ATF4.

Conclusions

PSAT1, which is overexpressed in ER-negative breast cancers, is activated by ATF4 and promotes cell cycle progression via regulation of the GSK3β/β-catenin/cyclin D1 pathway.

Electronic supplementary material

The online version of this article (doi: 10.1186/s13046-017-0648-4) contains supplementary material, which is available to authorized users.

DDX3 regulates endoplasmic reticulum stress-induced ATF4 expression

Accumulation of unfolded and potentially toxic proteins in the endoplasmic reticulum (ER) activates a cell stress adaptive response, which involves a reprogramming of general gene expression. ATF4 is a master stress-induced transcription factor that orchestrates gene expression in cells treated with various ER stress inducers including those used to treat cancers. ER stress-induced ATF4 expression occurs mainly at the translational level involving the activity of the phosphorylated (P) translation initiation factor (eIF) eIF2α. While it is well established that under ER stress PeIF2α drives ATF4 expression through a specialised mode of translation re-initiation, factors (e.g. RNA-binding proteins and specific eIFs) involved in PeIF2α-mediated ATF4 translation remain unknown. Here we identified the RNA-binding protein named DDX3 as a promotor of ATF4 expression in cancer cells treated with sorafenib, an ER stress inducer used as a chemotherapeutic. Depletion experiments showed that DDX3 is required for PeIF2α-mediated ATF4 expression. Luciferase and polyribosomes assays showed that DDX3 drives ER stress-induced ATF4 mRNA expression at the translational level. Protein-interaction assays showed that DDX3 binds the eIF4F complex, which we found to be required for ER stress-induced ATF4 expression. This study thus showed that PeIF2α-mediated ATF4 mRNA translation requires DDX3 as a part of the eIF4F complex.

Up-Regulated ATF4 Expression Increases Cell Sensitivity to Apoptosis in Response to Radiation

BACKGROUND/AIMS

Activating transcription factor 4 (ATF4) is a member of the activating transcription factor family which regulates the expression of genes involved in amino acid metabolism, redox homeostasis and ER stress responses. ATF4 is also over-expressed in human solid tumors, although its effect on responsiveness to radiation is largely unexplored.

METHODS

Real-time PCR was used to detect ATF4 mRNA levels in cells treated with different doses of 60Coγ radiation. Cell viability was assayed using a cell counting kit. The cell cycle was analyzed using flow cytometry, and cell apoptosis was assayed using Annexin V-PI double labeling. Small interfering RNA (siRNA) against ATF4 was transfected into ECV304 cells using Lipofectamine 2000. An ATF4 over-expression plasmid (p-ATF4-CGN) was transfected into HEK293 cells that endogenously expressed low levels of ATF4. The levels of intracellular reactive oxygen species (ROS) were measured using CM-H2DCFDA as a probe.

RESULTS

ATF4 mRNA and protein expression levels were higher after radiation and increased in a dose- and time-dependent manner in AHH1 lymphoblast cells (P < 0.05). An increase in ATF4 levels was also observed after radiation in primary murine spleen cells, human endothelial ECV304 cells, human liver LO2 cells, breast cancer MCF7 cells, and human hepatocellular carcinoma HEPG2 cells. No change was observed in human embryonic kidney 293 (HEK293) cells. Over-expressing ATF4 in HEK293 cells inhibited cell proliferation, increased cell apoptosis and significantly increased the proportion of cells in G1 phase. Conversely, when ATF4 expression was knocked down using siRNA in ECV304 cells, it protected the cells from radiation-induced apoptosis. These findings suggest that ATF4 may play a role in radiation-induced cell killing by inhibiting cell proliferation and promoting cell apoptosis.

CONCLUSIONS

In this study, we found that radiation up-regulated the expression of ATF4. We used ATF4 knockdown and over-expression systems to show that ATF4 may play a role in radiation-induced cellular apoptosis.

Sorafenib, a multikinase inhibitor, induces formation of stress granules in hepatocarcinoma cells

Stress granules (SGs) are cytoplasmic RNA multimeric bodies that form under stress conditions known to inhibit translation initiation. In most reported stress cases, the formation of SGs was associated with the cell recovery from stress and survival. In cells derived from cancer, SGs formation was shown to promote resistance to either proteasome inhibitors or 5-Fluorouracil used as chemotherapeutic agents. Despite these studies, the induction of SGs by chemotherapeutic drugs contributing to cancer cells resistance is still understudied. Here we identified sorafenib, a tyrosine kinase inhibitor used to treat hepatocarcinoma, as a potent chemotherapeutic inducer of SGs. The formation of SGs in sorafenib-treated hepatocarcionoma cells correlates with inhibition of translation initiation; both events requiring the phosphorylation of the translation initiation factor eIF2α. Further characterisation of the mechanism of sorafenib-induced SGs revealed PERK as the main eIF2α kinase responsible for SGs formation. Depletion experiments support the implication of PERK-eIF2α-SGs pathway in hepatocarcinoma cells resistance to sorafenib. This study also suggests the existence of an unexpected complex regulatory balance between SGs and phospho-eIF2α where SGs dampen the activation of the phospho-eIF2α-downstream ATF4 cell death pathway.

Glucose deprivation induces chemoresistance in colorectal cancer cells by increasing ATF4 expression

AIM

To investigate the role of activating transcription factor 4 (ATF4) in glucose deprivation (GD) induced colorectal cancer (CRC) drug resistance and the mechanism involved.

METHODS

Chemosensitivity and apoptosis were measured under the GD condition. Inhibition of ATF4 using short hairpin RNA in CRC cells under the GD condition and in ATF4-overexpressing CRC cells was performed to identify the role of ATF4 in the GD induced chemoresistance. Quantitative real-time RT-PCR and Western blot were used to detect the mRNA and protein expression of drug resistance gene 1 (MDR1), respectively.

RESULTS

GD protected CRC cells from drug-induced apoptosis (oxaliplatin and 5-fluorouracil) and induced the expression of ATF4, a key gene of the unfolded protein response. Depletion of ATF4 in CRC cells under the GD condition can induce apoptosis and drug re-sensitization. Similarly, inhibition of ATF4 in the ATF4-overexpressing CRC cells reintroduced therapeutic sensitivity and apoptosis. In addition, increased MDR1 expression was observed in GD-treated CRC cells.

CONCLUSION

These data indicate that GD promotes chemoresistance in CRC cells through up-regulating ATF4 expression.

TIFA, an inflammatory signaling adaptor, is tumor suppressive for liver cancer

TIFA (TNF receptor associated factor (TRAF)-interacting protein with a Forkhead-associated (FHA) domain), also called T2BP, was first identified using a yeast two-hybrid screening. TIFA contains a FHA domain, which directly binds phosphothreonine and phosphoserine, and a consensus TRAF6-binding motif. TIFA-mediated oligomerization and poly-ubiquitinylation of TRAF6 mediates signaling downstream of the Tumor necrosis factor alpha receptor 1 (TNFaR-I) and interleukin-1/Toll-like receptor 4 (TLR4) pathways. Examining TIFA expression in hepatocellular carcinoma (HCC) tissues microarrays, we noted marked decreases TIFA reactivity in tumor versus control samples. In agreement, we found that HCC cell lines show reduced TIFA expression levels versus normal liver controls. Reconstituting TIFA expression in HCC cell lines promoted two independent apoptosis signaling pathways: the induction of p53 and cell cycle arrest, and the activation of caspase-8 and caspase-3. In contrast, the expression of a non-oligomerizing mutant of TIFA impacted cells minimally, and suppression of TIFA expression protected cells from apoptosis. Mice bearing TIFA overexpression hepatocellular xenografts develop smaller tumors versus TIFA mutant tumors; terminal deoxynucleotidyl transferase dUTP nick end labeling staining demonstrates increased cell apoptosis, and decreased proliferation, reflecting cell cycle arrest. Interestingly, p53 has a greater role in decreased proliferation than cell death, as it appeared dispensable for TIFA-induced cell killing. The findings demonstrate a novel suppressive role of TIFA in HCC progression via promotion of cell death independent of p53.

Simvastatin inhibits ischemia/reperfusion injury-induced apoptosis of retinal cells via downregulation of the tumor necrosis factor-α/nuclear factor-κB pathway

Simvastatin, which is widely used in the prevention and treatment of hyperlipidemia-associated diseases, has been reported to enhance the survival of retinal ganglion cells (RGCs) in a model of retinal ischemia/reperfusion (IR) injury. However, the underlying mechanism of the anti-apoptotic effects of simvastatin on the retina have yet to be elucidated. In the present study, rats were treated with simvastatin or saline for 7 days prior to IR via ligation of the right cephalic artery. The results showed that simvastatin prevented the apoptosis of RGCs and cells in the inner nuclear layer. Furthermore, simvastatin regulated the expression of apoptosis-associated proteins. The expression levels of the anti-apoptotic protein B-cell lymphoma-2 were upregulated 4 and 24 h after IR in the simvastatin/IR group compared to those in the saline/IR group. Conversely, the levels of pro-apoptotic protein Bax were downregulated in the simvastatin/IR group compared to those in the saline/IR group. Furthermore, the results of the present study showed for the first time, to the best of our knowledge, that simvastatin decreased IR injury-induced tumor necrosis factor-α (TNF-α) and nuclear factor-κB (NF-κB) expression in the retina. These findings strongly suggested that simvastatin inhibits apoptosis following IR-induced retinal injury by inhibition of the TNF-α/NF-κB pathway. The present study also provided a rationale for developing therapeutic methods to treat IR-induced retinal injury in the clinic.

Gene expression in hepatocellular carcinoma: pilot study of potential transarterial chemoembolization response biomarkers

PURPOSE

To perform a feasibility study to explore the relationship between hepatocellular carcinoma genetics and transarterial chemoembolization treatment response to identify potential biomarkers associated with enhanced treatment efficacy.

MATERIALS AND METHODS

In this single-institution study, pretreatment hepatocellular carcinoma biopsy specimens for tumors in 19 patients (14 men, five women; mean age, 59 y) treated with chemoembolization between 2007 and 2013 were analyzed for a panel of 60 chemotherapy-sensitivity, hypoxia, mitosis, and inflammatory genes with the QuantiGene Plex 2.0 mRNA detection assay. Demographic, disease, and procedure data and tumor response outcomes were collected. Quantitative mRNA levels were compared based on radiologic response between tumors exhibiting complete response (CR) versus partial response (PR).

RESULTS

The study sample included 19 biopsy specimens from tumors (mean size, 3.0 cm; grade 1, n = 6; grade 2, n = 9; grade 3, n = 4) in patients treated with a mean of two conventional chemoembolization sessions. Thirteen and six tumors exhibited CR and PR, respectively, at a mean of 116 days after treatment. Tumors with CR showed a significant increase in (P < .05) or trend toward (P < .1) greater (range, 1.49-3.50 fold) pretreatment chemotherapy-sensitivity and mitosis (ATF4, BAX, CCNE1, KIF11, NFX1, PPP3CA, SNX1, TOP2A, and TOP2B) gene mRNA expression compared with tumors with PR, in addition to lower CXCL10 levels (0.48-fold), and had significantly (P < .05) higher (1.65-fold) baseline VEGFA levels.

CONCLUSIONS

Genetic signatures may allow prechemoembolization stratification of tumor response probability, and gene analysis may therefore offer an opportunity to personalize locoregional therapy by enhancing treatment modality allocation. Further corroboration of identified markers and exploration of their respective predictive capacity thresholds is necessary.

Activating transcription factor 4 mediates a multidrug resistance phenotype of esophageal squamous cell carcinoma cells through transactivation of STAT3 expression

Multidrug resistance (MDR) is a major challenge to the clinical treatment of esophageal cancer. The stress response gene activating transcription factor 4 (ATF4) is involved in homeostasis and cellular protection. However, relatively little is known about the expression and function of ATF4 in esophageal squamous cell carcinoma (ESCC) MDR. In this study, we investigate the potential role and mechanisms of ATF4 in ESCC MDR. We demonstrated that overexpression of ATF4 promotes the MDR phenotype in ESCC cells, while depletion of ATF4 in the MDR ESCC cell line induces drug re-sensitization. We also demonstrated that ATF4 transactivates STAT3 expression by directly binding to the signal transducers and activators of transcription 3 (STAT3) promoter, resulting in MDR in ESCC cells. Significantly, inhibition of STAT3 by small interfering RNA (siRNA) or a selective inhibitor (JSI-124) reintroduces therapeutic sensitivity. In addition, increased Bcl-2, survivin, and MRP1 expression levels were observed in ATF4-overexpressing cells. In conclusion, ATF4 may promote MDR in ESCC cells through the up-regulation of STAT3 expression, and thus is an attractive therapeutic target to combat therapeutic resistance in ESCC.

Nrf2- and ATF4-dependent upregulation of xCT modulates the sensitivity of T24 bladder carcinoma cells to proteasome inhibition

The ubiquitin-proteasome pathway degrades ubiquitinated proteins to remove damaged or misfolded protein and thus plays an important role in the maintenance of many important cellular processes. Because the pathway is also crucial for tumor cell growth and survival, proteasome inhibition by specific inhibitors exhibits potent antitumor effects in many cancer cells. xCT, a subunit of the cystine antiporter system xc (-), plays an important role in cellular cysteine and glutathione homeostasis. Several recent reports have revealed that xCT is involved in cancer cell survival; however, it was unknown whether xCT affects the cytotoxic effects of proteasome inhibitors. In this study, we found that two stress-inducible transcription factors, Nrf2 and ATF4, were upregulated by proteasome inhibition and cooperatively enhance human xCT gene expression upon proteasome inhibition. In addition, we demonstrated that the knockdown of xCT by small interfering RNA (siRNA) or pharmacological inhibition of xCT by sulfasalazine (SASP) or (S)-4-carboxyphenylglycine (CPG) significantly increased the sensitivity of T24 cells to proteasome inhibition. These results suggest that the simultaneous inhibition of both the proteasome and xCT could have therapeutic benefits in the treatment of bladder tumors.

Expression of ATF4 and VEGF in chorionic villus tissue in early spontaneous abortion

OBJECTIVE

To explore the relationship between early spontaneous abortion (SA) and the expression of activating transcription factor 4 (ATF4) and vascular endothelial growth factor (VEGF).

STUDY DESIGN

The expression of ATF4 and VEGF protein and mRNA in villi from first trimester spontaneous abortion (SA, n=30) and normal pregnancy (NP, n=30) were detected by immunohistochemistry and fluorescent quantitative polymerase chain reaction (FQ-PCR).

RESULTS

Both protein and mRNA expressions of ATF4 and VEGF in the SA group were significantly lower than in the NP group (P<0.01). Their proteins are expressed mainly in syncytiotrophoblast, cytotrophoblast and villous stromal cells. Correlation analysis showed that the expression of ATF4 was positively correlated with that of VEGF in the SA group (r=0.717, P<0.01).

CONCLUSION

Lower expression of ATF4 and VEGF genes in chorionic villus tissue may participate in the pathogenesis of spontaneous abortion.