ATF2 contributes to cisplatin resistance in non-small cell lung cancer and celastrol induces cisplatin resensitization through inhibition of JNK/ATF2 pathway

Celastrol inhibits angiogenesis and the biological processes of MDA-MB-231 cells via the DEGS1/S1P signaling pathway

Celastrol (Cel) shows potent antitumor activity in various experimental models. This study examined the relationship between Cel's antivascular and antitumor effects and sphingolipids. CCK-8 assay, transwell assay, Matrigel, PCR-array/RT-PCR/western blotting/immunohistochemistry assay, ELISA and HE staining were used to detect cell proliferation, migration and invasion, adhesion and angiogenesis, mRNA and protein expression, S1P production and tumor morphology. The results showed that Cel could inhibit proliferation, migration or invasion, adhesion and angiogenesis of human umbilical vein endothelial cells (HUVECs) and MDA-MB-231 cells by downregulating the expression of degenerative spermatocyte homolog 1 (DEGS1). Transfection experiments showed that downregulation of DEGS1 inhibited the above processes and sphingosine-1-phosphate (S1P) production of HUVECs and MDA-MB-231 cells, while upregulation of DEGS1 had the opposite effects. Coculture experiments showed that HUVECs could promote proliferation, migration and invasion of MDA-MB-231 cells through S1P/sphingosine-1-phosphate receptor (S1PR) signaling pathway, while Cel inhibited these processes in MDA-MB-231 cells induced by HUVECs. Animal experiments showed that Cel could inhibit tumor growth in nude mice. Western blotting, immunohistochemistry and ELISA assay showed that Cel downregulated the expression of DEGS1, CD146, S1PR1-3 and S1P production. These data confirm that DEGS1/S1P signaling pathway may be related to the antivascular and antitumor effects of cel.

Human NTHL1 expression and subcellular distribution determines cisplatin sensitivity in human lung epithelial and non-small cell lung cancer cells

Base excision repair is critical for maintaining genomic stability and for preventing malignant transformation. NTHL1 is a bifunctional DNA glycosylase/AP lyase that initiates repair of oxidatively damaged pyrimidines. Our recent work established that transient over-expression of NTHL1 leads to acquisition of several hallmarks of cancer in non-tumorigenic immortalized cells likely through interaction with nucleotide excision repair protein XPG. Here, we investigate how NTHL1 expression levels impact cellular sensitivity to cisplatin in non-tumorigenic immortalized cells and five non-small cell lung carcinomas cell lines. The cell line with lowest expression of NTHL1 (H522) shows the highest resistance to cisplatin indicating that decrease in NTHL1 levels may modulate resistance to crosslinking agents in NSCLC tumors. In a complementation study, overexpression of NTHL1 in H522 cell line sensitized it to cisplatin. Using NTHL1 N-terminal deletion mutants defective in nuclear localization we show that cisplatin treatment can alter NTHL1 subcellular localization possibly leading to altered protein-protein interactions and affecting cisplatin sensitivity. Experiments presented in this study reveal a previously unknown link between NTHL1 expression levels and cisplatin sensitivity of NSCLC tumor cells. These findings provide an opportunity to understand how altered NTHL1 expression levels and subcellular distribution can impact cisplatin sensitivity in NSCLC tumor cells.

Quiescent Ovarian Cancer Cells Secrete Follistatin to Induce Chemotherapy Resistance in Surrounding Cells in Response to Chemotherapy

PURPOSE

We recently reported that the transcription factor NFATC4, in response to chemotherapy, drives cellular quiescence to increase ovarian cancer chemoresistance. The goal of this work was to better understand the mechanisms of NFATC4-driven ovarian cancer chemoresistance.

EXPERIMENTAL DESIGN

We used RNA sequencing to identify NFATC4-mediated differential gene expression. CRISPR-Cas9 and FST (follistatin)-neutralizing antibodies were used to assess impact of loss of FST function on cell proliferation and chemoresistance. ELISA was used to quantify FST induction in patient samples and in vitro in response to chemotherapy.

RESULTS

We found that NFATC4 upregulates FST mRNA and protein expression predominantly in quiescent cells and FST is further upregulated following chemotherapy treatment. FST acts in at least a paracrine manner to induce a p-ATF2-dependent quiescent phenotype and chemoresistance in non-quiescent cells. Consistent with this, CRISPR knockout (KO) of FST in ovarian cancer cells or antibody-mediated neutralization of FST sensitizes ovarian cancer cells to chemotherapy treatment. Similarly, CRISPR KO of FST in tumors increased chemotherapy-mediated tumor eradication in an otherwise chemotherapy-resistant tumor model. Suggesting a role for FST in chemoresistance in patients, FST protein in the abdominal fluid of patients with ovarian cancer significantly increases within 24 hours of chemotherapy exposure. FST levels decline to baseline levels in patients no longer receiving chemotherapy with no evidence of disease. Furthermore, elevated FST expression in patient tumors is correlated with poor progression-free, post-progression-free, and overall survival.

CONCLUSIONS

FST is a novel therapeutic target to improve ovarian cancer response to chemotherapy and potentially reduce recurrence rates.

NEDD4L represses prostate cancer cell proliferation via modulating PHF8 through the ubiquitin-proteasome pathway

PURPOSE

Prostate cancer (PC) is a heterogeneous malignancy that greatly threatens man's health. E3 ubiquitin-protein ligase neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) imparts an regulatory role in various malignancies. This study focused on the modulatory mechanism of NEDD4L in proliferation of prostate cancer cells (PCCs) via regulating histone demethylase plant homeodomain finger protein 8 (PHF8/KDM7B) through the ubiquitin-proteasome system.

METHODS

The expression levels of NEDD4L, PHF8, H3 lysine 9 dimethylation (H3K9me2) and activating transcription factor 2 (ATF2) in PC tissues and cell lines were detected via real-time quantitative polymerase chain reaction and Western blotting. After transfection of pcDNA3.1-NEDD4L, pcDNA3.1-PHF8, and pcDNA3.1-ATF2 into PCCs, cell proliferation was assessed via the cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays. Interaction between NEDD4L and PHF8 was identified via the protein immunoprecipitation. The ubiquitination level of PHF8 was determined via the ubiquitination detection. The enrichments of H3K9me2 and PHF8 in the ATF2 promotor region were detected via the chromatin-immunoprecipitation assay.

RESULTS

PHF8 and ATF2 were highly expressed while NEDD4L was poorly expressed in PC tissues and cells. NEDD4L overexpression reduced proliferation of PCCs. NEDD4Linduced degradation of PHF8 via ubiquitination. PHF8 limited the enrichment of H3K9me2 in the ATF2 promotor region and enhanced ATF2 transcription. Upregulation of PHF8 or ATF2 abolished the inhibitory role of NEDD4L in proliferation of PCCs.

CONCLUSION

NEDD4L facilitated degradation of PHF8 to limit ATF2 transcription, thereby suppressing proliferation of PCCs.

Activating transcription factor 2 (AccATF2) regulates tolerance to oxidative stress in Apis cerana cerana

Activating transcription factor 2 (ATF2), a basic leucine zipper (bZIP) transcription factor, plays a crucial role in immune and DNA damage response in mammals. However, the function of ATF2 in insects remains unknown. Here, we isolated the ATF2 gene from Apis cerana cerana (AccATF2) and found that AccATF2 was a main regulator of the honeybee response to oxidative stress. Our results showed that AccATF2 was highly expressed in the head, thorax and integument. AccATF2 was expressed throughout the development period of honeybees, and the highest AccATF2 transcript level was noted in brown-eyed pupae, indicating its indispensable roles in honeybee survival. Antioxidant function analysis showed that AccATF2 expression was markedly induced in response to oxidative stress caused by various environmental stresses. AccATF2 overexpression substantially enhanced the tolerance to oxidative stress of Escherichia coli cells compared with control cells. AccATF2 knockdown significantly increased the production of malondialdehyde (MDA), the transcription of antioxidant genes and the activity of antioxidant enzymes in honeybees, suggesting that AccATF2 knockdown resulted in oxidative damage to honeybees. Moreover, AccATF2 knockdown decreased honeybee resistance to oxidative stress caused by high temperature. Overall, AccATF2 plays an important role in maintaining redox homeostasis and protecting honeybees from oxidative stress caused by various environmental stimuli. Our discoveries add to a growing understanding of how honeybees cope with various adverse environmental conditions to ensure their survival.

Nuclear Mechanisms Involved in Endocrine Resistance

Endocrine therapy is a standard treatment offered to patients with ERα (estrogen receptor α)-positive breast cancer. In endocrine therapy, ERα is either directly targeted by anti-estrogens or indirectly by aromatase inhibitors which cause estrogen deficiency. Resistance to these drugs (endocrine resistance) compromises the efficiency of this treatment and requires additional measures. Endocrine resistance is often caused by deregulation of the PI3K/AKT/mTOR pathway and/or cyclin-dependent kinase 4 and 6 activities allowing inhibitors of these factors to be used clinically to counteract endocrine resistance. The nuclear mechanisms involved in endocrine resistance are beginning to emerge. Exploring these mechanisms may reveal additional druggable targets, which could help to further improve patients' outcome in an endocrine resistance setting. This review intends to summarize our current knowledge on the nuclear mechanisms linked to endocrine resistance.

JARID2 promotes stemness and cisplatin resistance in non-small cell lung cancer via upregulation of Notch1

Increased stemness is causally linked to development of drug resistance in cancers. JARID2 is a member of the Jumonji family of proteins and regulates differentiation of embryonic stem cells. However, the role of JARID2 in lung cancer stemness and drug resistance is still unclear. In this study, we investigated the expression of JARID2 in parental and cisplatin (CDDP) resistant non-small cell lung cancer (NSCLC) cells. The function of JARID2 in modulating CDDP sensitivity of NSCLC cells was determined. It was found that JARID2 is upregulated in CDDP resistant NSCLC cells, which depends on SOX2 expression. JARID2 overexpression promotes CDDP resistance in NSCLC cells, whereas JARID2 depletion restores CDDP sensitivity in CDDP resistant NSCLC cells. Moreover, JARID2 overexpression enhances cancer stem cell-like properties in NSCLC cells, which is coupled with increased expression of cancer stem cell markers. Mechanistically, JARID2-induced stemness and CDDP resistance is mediated by upregulation of Notch1. In clinical settings, high expression of JARID2 is significantly associated with advanced TNM stage, shorter overall survival, and poor chemotherapeutic response. These findings point toward an important role of JARID2 in CDDP resistance and stemness of NSCLC and provide a promising target for overcoming CDDP resistance.

Micro-RNA-451 Reduces Proliferation of B-CPAP Human Papillary Thyroid Cancer Cells by Downregulating Expression of Activating Transcription Factor 2

Background

MicroRNAs (miRNAs) are novel biomarkers that are important in tumorigenesis and cancer treatment resistance. miR-451 is expressed in human papillary thyroid carcinoma (PTC) tissues and is associated with tumor progression. This study investigated the molecular mechanism associated with the effects of miR-451 on B-CPAP human PTC cells in vitro.

Material/Methods

Binding of miRNAs to the 3′ untranslated region (3′UTR) of messenger RNA (mRNA) was determined with a luciferase reporter assay. miRNAs and plasmids were transfected into human PTC B-CPAP cells with Lipofectamine 2000 Transfection Reagent. Cell viability was tested with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. The levels of miRNAs and mRNA were determined with quantitative polymerase chain reaction and protein levels were analyzed with immunoblotting.

Results

miR-451 bound to wild-type but not mutant 3′-UTR of activating transcription factor 2 (ATF2). MiR-451 mimics inhibited the growth of B-CPAP cells and reduced mRNA and protein levels in ATF2, whereas miR-451 inhibitors promoted the growth of B-CPAP cells and increased mRNA and protein levels in ATF2.

Conclusions

miR-451 directly bound to the 3′UTR of ATF2, decreased mRNA and protein levels in ATF2, and inhibited growth of B-CPAP cells. Our findings suggest that miR-451 may be a potential therapeutic target for PTC.

The interplay between ATF2 and NEAT1 contributes to lung adenocarcinoma progression

Background

Activating transcription factor 2 (ATF2), a member of the activator protein 1 (AP-1) transcription factor family, has been shown to be involved in the pathobiology of numerous cancers. However, the biological role and mechanism of ATF2 in lung adenocarcinoma (LUAD) remains to be elucidated.

Methods

The expression of ATF2, NEAT1 and miR-26a-5p in LUAD tissues and cell lines was detected by qRT-PCR and western blotting. The interaction between ATF2, NEAT1, and miR-26a-5p was validated by chromatin immunoprecipitation, luciferase reporter assay and RNA immunoprecipitation. Cell proliferation, invasion and tumorigenesis of LUAD cells were analyzed by using CCK8, transwell invasion assay and xenograft tumor model.

Results

We confirmed that ATF2 expression was increased in LUAD tissues compared with normal adjacent lung tissues. Functional experiments showed that ATF2 positively regulated cell proliferation and invasion in LUAD cells. Moreover, we identified that NEAT1 expression was increased in LUAD tissues and positively correlated with ATF2 expression. Mechanistically, ATF2 could bind to the promoter of NEAT1 to promote its transcription. Rescue experiments showed that ATF2 exerted its oncogenic function in LUAD, at least, partly through NEAT1 upregulation. In turn, NEAT1 could positively regulate ATF2 expression and form a positive feedback loop in LUAD cells. Furthermore, we demonstrated that NEAT1 positively regulated ATF2 expression via sponging miR-26a-5p.

Conclusion

ATF2 and NEAT1 form a positive feedback loop mediated by miR-26a-5p and coordinately contribute to LUAD progression.

Pristimerin synergizes with gemcitabine through abrogating Chk1/53BP1-mediated DNA repair in pancreatic cancer cells

It has been shown that checkpoint kinase inhibitors can enhance chemosensitivity to gemcitabine by disrupting the replication stress response (RSR). In the present study, we aimed to describe the chemical synthetic lethal effects of the combination of gemcitabine and quinone-methide triterpenoid pristimerin in pancreatic cancer (PC) cells. The drug interaction assay indicated effective synergy between gemcitabine and pristimerin at sub-IC₅₀ concentrations. Interestingly, pristimerin induced lysosomal degradation of checkpoint kinase 1 (Chk1), decreased the percentage of cells at the G1/S boundary and triggered significant double-stranded DNA breaks compared to gemcitabine treatment alone. Moreover, gemcitabine activated the phosphorylation of Chk1 and induced the formation of poly (ADP-ribose) polymers (PARs) as well as the accumulation of 53BP1, which was either partially or completely impaired by pristimerin. Meanwhile, pristimerin augmented the expression of γH2AX upon gemcitabine treatment. Finally, the combination of gemcitabine with pristimerin increased the apoptotic potential of PC cells. These results show that pristimerin acts as a naturally occurring inhibitor of RSR, and a novel therapeutic strategy of combining pristimerin and gemcitabine deserves further detailed investigation in PC models in vivo.

Circ_SATB2 Attenuates the Anti-Tumor Role of Celastrol in Non-Small-Cell Lung Carcinoma Through Targeting miR-33a-5p/E2F7 Axis

Background

Celastrol (Cela) was a natural compound that exerted anti-tumor activity in many cancer cells. Nevertheless, the molecular mechanism behind the anti-tumor role of Cela in non-small-cell lung carcinoma (NSCLC) remains to be clarified.

Methods

Flow cytometry was used to analyze cell cycle progression and apoptosis. Colony formation assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were used to analyze cell proliferation. Cell migration and invasion abilities were assessed by transwell assays. Quantitative real-time polymerase chain reaction (qRT-PCR) was implemented for the detection of RNA levels. Western blot assay was used for the determination of protein levels. Dual-luciferase reporter assay was conducted to confirm the interaction between microRNA-33a-5p (miR-33a-5p) and circular RNA SATB homeobox 2 (circ_SATB2) or E2F transcription factor 7 (E2F7). Xenograft tumor assay was conducted to test the roles of Cela and circ_SATB2 in NSCLC progression in vivo.

Results

Cela hampered the malignant behaviors of NSCLC cells. Cela down-regulated circ_SATB2 level in NSCLC cells. Cela stimulation-induced suppressive influence in NSCLC progression was alleviated by circ_SATB2 accumulation. E2F7 interference overturned circ_SATB2-mediated effects in Cela-stimulated NSCLC cells. MiR-33a-5p was a target of circ_SATB2, and E2F7 was verified as a target of miR-33a-5p. Circ_SATB2 attenuated Cela-mediated effects through targeting miR-33a-5p in NSCLC cells. Cela-mediated suppressive effect on tumor growth was partly attenuated by the overexpression of circ_SATB2 in vivo.

Conclusion

Cela suppressed NSCLC development through regulating circ_SATB2/miR-33a-5p/E2F7 signaling cascade.

The Ras-ERK signaling pathway regulates acetylated activating transcription factor 2 via p300 in pancreatic cancer cells

Background

Activating transcription factor 2 (ATF2) regulates the expression of downstream target genes and is phosphorylated by the Ras-extracellular-signal-regulated kinase (ERK) pathway. Acetylation of ATF2 is necessary for this type of regulation. However, the molecular mechanism by which the Ras-ERK pathway mediates the regulation of acetylated ATF2 is unknown. This study investigates the mechanism of Ras-ERK pathway-mediated regulation of acetylated ATF2 in maintaining the characteristic phenotype of pancreatic cancer cells.

Methods

This study was carried out using ASPC-1 and BXPC-3 pancreatic cancer cell lines transfected with the double mutant Ras^G12V/T35S. The levels of phosphorylated ERK1/2 were measured to establish the activated Ras-ERK pathway. The regulation of acetylated ATF2 was examined by detecting the protein level using western blotting, and the effects on cancer cell phenotype were measured using cell viability, proliferation, migration, and apoptosis assays. Also, chromatin immunoprecipitation (ChIP) assays were used to measure the effect on respective downstream target genes.

Results

The results showed that Ras^G12V/T35S reduced the level of acetylated ATF2 in ASPC-1 and BXPC-3 cells. Compared to wild-type ATF2, the mutant ATF2^K357Q (which mimics the irreversible acetylated form of ATF2) reduced the cancer cell phenotype and showed decreased enrichment on target genes upon transfection with Ras. Moreover, the level of acetylated ATF2 was regulated by the degradation of p300 through E3 ubiquitin ligase mouse double minute 2 homolog (MDM2).

Conclusions

Activation of the Ras-ERK pathway regulates acetylated ATF2 through degradation of p300 via a proteasome-dependent pathway, which alters the transcription of downstream target genes responsible for the cancer cell phenotype.

Bcl-xL represents a therapeutic target in Philadelphia negative myeloproliferative neoplasms

Myeloproliferative neoplasms are divided into essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). Although ruxolitinib was proven to be effective in reducing symptoms, patients rarely achieve complete molecular remission. Therefore, it is relevant to identify new therapeutic targets to improve the clinical outcome of patients. Bcl‐xL protein, the long isoform encoded by alternative splicing of the Bcl‐x gene, acts as an anti‐apoptotic regulator. Our study investigated the role of Bcl‐xL as a marker of severity of MPN and the possibility to target Bcl‐xL in patients. 129 MPN patients and 21 healthy patients were enrolled in the study. We analysed Bcl‐xL expression in leucocytes and in enriched CD34+ and CD235a+ cells. Furthermore, ABT‐737, a Bcl‐xL inhibitor, was tested in HEL cells and in leucocytes from MPN patients. Bcl‐xL was found progressively over‐expressed in cells from ET, PV and PMF patients, independently by JAK2 mutational status. Moreover, our data indicated that the combination of ABT‐737 and ruxolitinib resulted in a significantly higher apoptotic rate than the individual drug. Our study suggests that Bcl‐xL plays an important role in MPN independently from JAK2 V617F mutation. Furthermore, data demonstrate that targeting simultaneously JAK2 and Bcl‐xL might represent an interesting new approach.

6'-O-galloylpaeoniflorin regulates proliferation and metastasis of non-small cell lung cancer through AMPK/miR-299-5p/ATF2 axis

Background

Recent studies have shown 6'-O-galloylpaeoniflorin (GPF), a nature product extracted from the roots of paeoniflorin exerts anti-oxidant and anti-inflammatory activities. However, the effects of GPF on the proliferation and invasion in non-small cell lung cancer (NSCLC) cells have not been clarified.

Methods

MTT assay was performed to determine the cytotoxicity of GPF treatment on NSCLC cells. Colony formation assay, cell scratch test and transwell assay were performed to determine the proliferation and invasion of NSCLC cells in vitro, respectively. An A549 cell xenograft mouse model was performed to confirm the growth of NSCLC cells in vivo. Western blotting was used to measure the levels of activating transcription factor 2 (ATF2), AMP-activated protein kinase (AMPK) and phosph-AMPK (p-AMPK). Luciferase assay was used to validate the binding of miR-299-5p on the 3' untranslated region (UTR) of ATF2.

Results

Administration of GPF (50 or 100 μM) was significantly cytotoxic to A549 cells and H1299 cells, as well as inhibited the clonality, invasion and metastasis of NSCLC cells in vitro. GPF treatment also inhibited the tumor growth of NSCLC cell mouse xenografts in vivo. Exotic expression of miR-299-5p significantly inhibited the growth of NSCLC cells in vitro and in vivo. Downregulation of miR-299-5p expression attenuated the inhibition of the proliferation and metastasis of non-small cell lung cancer cells by GPF treatment. miR-299-5p significantly decreased ATF2 mRNA and protein levels in A549 cells (p < 0.05). Overexpression of ATF2 blocked the inhibitory effect of miR-299-5p on the proliferation and invasiveness of A549 cells.

Conclusions

GPF regulates miR-299-5p/ATF2 axis in A549 cells via the AMPK signalling pathway, thereby inhibiting the proliferation and metastasis of non-small cell lung cancer cells.

Celastrol pretreatment as a therapeutic option against cisplatin-induced nephrotoxicity

Celastrol is a natural bioactive compound extracted from the medicinal plant Tripterygium wilfordii Hook F. It exhibits immunosuppressive, anti-inflammatory, and antioxidant activities. Cisplatin is a commonly used chemotherapeutic drug in the treatment of a wide range of tumors. Although very effective therapeutically, it can cause nephrotoxicity leading to dose reduction or discontinuation of treatment. This study aims to clarify the therapeutic potential of celastrol in cisplatin-induced nephrotoxicity. The possible protective effects of celastrol pretreatment against cisplatin-induced oxidative stress and genotoxicity were investigated. A rat kidney epithelial cell line NRK-52E was pretreated with the desired concentrations of celastrol (200 nM, 100 nM, and 50 nM) for 24 h. The cells were treated with 50 μM cisplatin for a further 24 h to see whether cisplatin caused the same or less toxicity compared to the vehicle control group. Alkaline comet assay was performed for genotoxicity assessment. Genotoxicity evaluation revealed that celastrol caused a statistically significant reduction in DNA damage. Oxidative stress parameters were evaluated by measuring the glutathione (GSH) and protein carbonyl (PC) levels and also by measuring the enzyme activities of glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT) and superoxide dismutase (SOD) enzymes. Celastrol pretreatment increased the GSH content of the cells and ameliorated the protein carbonylation level. Likewise, celastrol pretreatment improved the GR and CAT activities. However, no significant difference was observed in GPx and SOD activities. In the light of these findings, celastrol treatment could be a therapeutic option to reduce cisplatin-induced nephrotoxicity. Further studies are needed for the clarification of its therapeutic potential.

Axl is a novel target of celastrol that inhibits cell proliferation and migration, and increases the cytotoxicity of gefitinib in EGFR mutant non‑small cell lung cancer cells

Gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR‑TKI) is an excellent therapeutic agent to treat EGFR mutation‑positive non‑small cell lung cancer (NSCLC). However, the initial response decreases as chemoresistance develops. In the present study, gefitinib‑resistant EGFR mutant NSCLC PC‑9/GR cells were established to examine the characteristics and mechanisms associated with chemoresistance. Axl expression in PC‑9/GR cells was transcriptionally upregulated, since Axl protein and mRNA expression levels were identified to be increased according to western blot analysis and reverse transcription polymerase chain reaction results. The inhibitory effect of celastrol on Axl protein expression level, cell viability and clonogenicity were identified in parental and gefitinib‑resistant PC‑9 cells. In addition, treatment of PC‑9/GR cells with celastrol and gefitinib in combination was demonstrated to synergistically suppress Axl protein expression level, cell proliferation and migration. Taken together, upregulation of Axl expression seems to be associated with chemoresistance of PC‑9/GR cells. Furthermore, celastrol targets Axl to exert its anticancer effects in order to increase the susceptibility of PC‑9/GR cells to gefitinib and overcome chemoresistance.

TRAF6-p38/JNK-ATF2 axis promotes microglial inflammatory activation

Activating transcription factor 2 (ATF2), a member of the alkaline-leucine zipper family, is widely expressed in various tissues, and reportedly involved in inflammatory responses to various irritates, but its role in the central nervous system (CNS) remains unclear. This study aimed to investigate the expression and biological function of ATF2 in CNS inflammation. Utilizing the LPS-induced neuroinflammation model on mice, we first found ATF2 up-regulation and its co-localization with microglia in inflamed mice brain. In vitro, we revealed an increased expression, phosphorylation, and nuclear accumulation of ATF2 in LPS-treated BV2 microglia cells. Inhibiting ATF2 significantly decreased the expression of pro-inflammatory factors in LPS-treated microglia, and alleviated neuronal apoptosis induced by the conditioned medium of activated microglia. Knocking down TRAF6, an important adaptor of the TLR4/MAPK/NF-κB signaling pathway, suppressed the LPS-induced ATF2 expression and phosphorylation, accompanied by the decreased p38/JNK phosphorylation, in microglia. Blocking p38 or JNK signaling pathway by the specific inhibitors reversed the TRAF6-overexpression mediated ATF2 activation. Taken together, our data first proved the pro-inflammatory function of ATF2 in microglia, and suggested that the TRAF6-JNK/p38-ATF2 axis might promote microglial inflammatory activation and thus aggravate neuronal injury in brain, which might become a potential therapeutic target for CNS diseases.

Phytochemicals: Current strategy to sensitize cancer cells to cisplatin

Cisplatin-based chemotherapeutic regimens are the most frequently used adjuvant treatments for many types of cancer. However, the development of chemoresistance to cisplatin results in treatment failure. Despite the significant developments in understanding the mechanisms of cisplatin resistance, effective strategies to enhance the chemosensitivity of cisplatin are lacking. Phytochemicals are naturally occurring plant-based compounds that can augment the anti-cancer activity of cisplatin, with minimal side effects. Notably, some novel phytochemicals, such as curcumin, not only increase the efficacy of cisplatin but also decrease toxicity induced by cisplatin. However, the exact mechanisms underlying this process remain unclear. In this review, we discussed the progress made in utilizing phytochemicals to enhance the anti-cancer efficacy of cisplatin. We also presented some ideal phytochemicals as novel agents for counteracting cisplatin-induced organ damage.

Inactivation of ATF-2 enhances epithelial-mesenchymal transition and gemcitabine sensitivity in human pancreatic cancer cells

OBJECTIVE

This work aimed to study the activating transcription factor 2 or AMP-dependent transcription factor-2 (ATF-2) inhibition mediated gemcitabine sensitivity in human pancreatic cancer cells.

METHODS

The protein and messenger RNA expressions of ATF-2 in 42 pancreatic cancer tissues and adjacent nontumorous tissues were detected. Kaplan-Meier survival analysis was performed based on the expression level of ATF-2 protein in tumor tissues. Then the pancreatic cancer cells were transduced with ATF-2-expressing lentivirus and small interfering RNAs (siRNAs) to investigate the effect of ATF-2 on pancreatic cancer cell invasion, epithelium to mesenchyme transition, apoptosis, and gemcitabine sensitivity.

RESULTS

The expression of phosphorylated (p)-ATF-2 protein was upregulated in pancreatic cancer tissues compared with adjacent nontumorous tissues. Patients with relative higher p-ATF-2 level showed significantly lower survival time. Then we found that the transfection ATF-2 siRNA into BxPC3 cells inhibited cell proliferation, invasion, and epithelium to mesenchyme transition, but enhanced cell apoptosis. These changes could be enhanced by the additional administration of gemcitabine. In addition, we confirmed that the overexpression of ATF-2 in Panc-1 cells promoted cell invasion and epithelium to mesenchyme transition.

CONCLUSION

We concluded that inhibition-promoted ATF-2 expression was responsible for epithelium to mesenchyme transition and invasion of pancreatic cancer cells, while the inhibition of ATF-2 confers to gemcitabine sensitivity in human pancreatic cancer cells in vitro.

Silencing activating transcription factor 2 promotes the anticancer activity of sorafenib in hepatocellular carcinoma cells

The present study aimed to investigate the anticancer effect of sorafenib combined with silencing of activating transcription factor 2 (ATF2) in hepatocellular carcinoma (HCC) cells and to assess the underlying molecular mechanisms. Huh-7 HCC cell line was selected for the present study. Small interfering RNA (siRNA)-ATF2 sequence was constructed to silence ATF2 expression. The experiment was divided into 6 groups: i) Control; ii) vector; iii) sorafenib (6.8 µM); iv) vector+sorafenib; v) siRNA-ATF2; and vi) siRNA-ATF2+sorafenib groups. Cell proliferation, apoptosis, migration and invasion were detected following treatments with sorafenib and/or ATF2 silencing. Additionally, expression of tumor necrosis factor (TNF)-α and c-Jun N-terminal kinase 3 (JNK3) was detected using reverse transcription-quantitative polymerase chain reaction and western blotting. The current findings revealed that siRNA-ATF2 significantly reduced ATF2 expression. Cell proliferation, migration and invasion abilities in the sorafenib and siRNA-ATF2 groups were significantly reduced compared with the control group (P<0.05). Apoptotic rate in the sorafenib and siRNA-ATF2 groups was significantly increased compared with the control group (P<0.05). The mRNA and protein expression levels of ATF2 in the sorafenib or siRNA-ATF2 groups was significantly reduced when compared with control group. The phosphorylation of ATF2 was also reduced following sorafenib treatment or ATF2 silence. Although JNK3 mRNA expression level was not affected, the phosphorylation level of JNK3 was significantly promoted following sorafenib treatment or ATF2 silencing. Additionally, TNF-α mRNA and protein expression levels were increased following sorafenib treatment or ATF2 silencing. It is of note that siRNA-ATF2 treatment promoted the anticancer activity of sorafenib in Huh-7 cells. Additionally, siRNA-ATF2+sorafenib treatment combined additionally promoted TNF-α expression and phosphorylation of JNK3. Combined siRNA-ATF2 and sorafenib treatment had a greater anticancer effect compared with sorafenib or ATF2 silencing alone. The possible mechanism involved in the anticancer effect of sorafenib and ATF2 silencing may be associated with the activation of the TNF-α/JNK3 signaling pathway.

miR-144-5p Enhances the Radiosensitivity of Non-Small-Cell Lung Cancer Cells via Targeting ATF2

MicroRNAs (miRNAs or miRs) regulate gene expression at the posttranscriptional level and are involved in many biological processes such as cell proliferation and migration, stem cell differentiation, inflammation, and apoptosis. In particular, miR-144-3p is downregulated in various cancers, and its overexpression inhibits the proliferation and metastasis of cancer cells. However, the role of miR-144-5p in non-small-cell lung cancer (NSCLC), especially radiosensitivity, is unknown. In this study, we found that miR-144-5p was downregulated in NSCLC clinical specimens as well as NSCLC cell lines exposed to radiation. Enhanced expression of miR-144-5p promoted the radiosensitivity of NSCLC cells in vitro and A549 cell mouse xenografts in vivo. Furthermore, we identified activating transcription factor 2 (ATF2) as the direct and functional target of miR-144-5p using integrated bioinformatics analysis and a luciferase reporter assay. In addition, restoration of ATF2 expression inhibited miR-144-5p-induced NSCLC cell sensitivity to radiation in vitro and in vivo. Our findings suggest that deregulation of the miR-144-5p/ATF2 axis plays an important role in NSCLC cell radiosensitivity, thus representing a new potential therapeutic target for NSCLC.

Dasatinib modulates sensitivity to pemetrexed in malignant pleural mesothelioma cell lines

Background

Thymidylate synthase (TS), one of the key enzymes for thymidine synthesis, is a target of pemetrexed (PEM), a key agent for the systemic therapy of malignant pleural mesothelioma (MPM) and its overexpression has been correlated to PEM-resistance. In MPM, experimental data report activation of the c-SRC tyrosine kinase suggesting it as a potential target to be further investigated.

Results

MPM cell lines showed different sensitivity, being MSTO the most and REN the least sensitive to PEM. REN cells showed high levels of both TS and SRC: dasatinib inhibited SRC activation and suppressed TS protein expression, starting from 100 nM dose, blocking the PEM-induced up regulation of TS protein levels. Dasatinib treatment impaired cells migration, and both sequential and co-administration with PEM significantly increased apoptosis. Dasatinib pretreatment improved sensitivity to PEM, downregulated TS promoter activity and, in association with PEM, modulated the downstream PI3K-Akt-mTOR signaling.

Cell lines and Methods

In three MPM cell lines (MPP89, REN and MSTO), the effects of c-SRC inhibition, in correlation with TS expression and PEM sensitivity, were evaluated. PEM and dasatinib, a SRC inhibitor, were administered as single agents, in combination or sequentially. Cell viability, apoptosis and migration, as well as TS expression and SRC activation have been assessed.

Conclusions

These data indicate that dasatinib sensitizes mesothelioma cells to PEM through TS down-regulation.

A Mechanistic Overview of Triptolide and Celastrol, Natural Products from Tripterygium wilfordii Hook F

Triptolide and celastrol are predominantly active natural products isolated from the medicinal plant Tripterygium wilfordii Hook F. These compounds exhibit similar pharmacological activities, including anti-cancer, anti-inflammation, anti-obesity, and anti-diabetic activities. Triptolide and celastrol also provide neuroprotection and prevent cardiovascular and metabolic diseases. However, toxicity restricts the further development of triptolide and celastrol. In this review, we comprehensively review therapeutic targets and mechanisms of action, and translational study of triptolide and celastrol. We systemically discuss the structure-activity-relationship of triptolide, celastrol, and their derivatives. Furthermore, we propose the use of structural derivatives, targeted therapy, and combination treatment as possible solutions to reduce toxicity and increase therapeutic window of these potent natural products from T. wilfordii Hook F.

Metabolomics profiles delineate uridine deficiency contributes to mitochondria-mediated apoptosis induced by celastrol in human acute promyelocytic leukemia cells

Celastrol, extracted from “Thunder of God Vine”, is a promising anti-cancer natural product. However, its effect on acute promyelocytic leukemia (APL) and underlying molecular mechanism are poorly understood. The purpose of this study was to explore its effect on APL and underlying mechanism based on metabolomics. Firstly, multiple assays indicated that celastrol could induce apoptosis of APL cells via p53-activated mitochondrial pathway. Secondly, unbiased metabolomics revealed that uridine was the most notable changed metabolite. Further study verified that uridine could reverse the apoptosis induced by celastrol. The decreased uridine was caused by suppressing the expression of gene encoding Dihydroorotate dehydrogenase, whose inhibitor could also induce apoptosis of APL cells. At last, mouse model confirmed that celastrol inhibited tumor growth through enhanced apoptosis. Celastrol could also decrease uridine and DHODH protein level in tumor tissues. Our in vivo study also indicated that celastrol had no systemic toxicity at pharmacological dose (2 mg/kg, i.p., 21 days). Altogether, our metabolomics study firstly reveals that uridine deficiency contributes to mitochondrial apoptosis induced by celastrol in APL cells. Celastrol shows great potential for the treatment of APL.

Niclosamide enhances the cytotoxic effect of cisplatin in cisplatin-resistant human lung cancer cells via suppression of lung resistance-related protein and c-myc

Lung cancer is a leading cause of cancer-associated mortality worldwide. The cisplatin (DDP)-based chemotherapy remains the foundation of treatment for the majority of patients affected by advanced non-small cell lung cancer (NSCLC). However, DDP-resistance limits the clinical utility of this drug in patients with advanced NSCLC. The aim of the present study was to investigate the inhibitory effect of niclosamide on human lung cancer cell growth and to investigate the possible underlying mechanism. The effects of niclosamide on the proliferation of human lung adenocarcinoma (A549) and DDP-resistant (CR) human lung adenocarcinoma (A549/DDP) cells were examined by Cell Counting kit-8 assay. The impact of niclosamide on the apoptosis of A549/DDP cells was detected by Annexin V-fluorescein isothiocyanate/propidium iodide assay. The expression levels of cisplatin-resistant-associated molecules (lung resistance-related protein and c-myc) following niclosamide treatment in A549/DDP cells were evaluated by western blot analysis. The results indicated that niclosamide in combination with DDP demonstrated a synergistic effect in A549/DDP cells and directly induced apoptosis, which may be associated with caspase-3 activation. Furthermore, niclosamide decreased the expression level of c-myc protein, which may influence DDP sensitivity of A549/DDP cells. Thus, the present study indicates that niclosamide combined with DDP exerts a synergistic effect in cisplatin-resistant lung cancer cells and may present as a promising drug candidate in lung cancer therapy.

Celastrol induces apoptosis in hepatocellular carcinoma cells via targeting ER-stress/UPR

Hepatocellular carcinoma (HCC) is one of the most serious and deadly diseases worldwide with limited options for effective treatment. Biomarker-based active compound targeting therapy may shed some light on novel drugs for HCC. The endoplasmic reticulum (ER) stress and unfolded protein response (UPR) play important roles in the regulation of cell fate and have become novel signaling targets for the development of anticancer drugs. Celastrol, a triterpene from traditional Chinese medicine, has been reported to possess anti-tumor effects on various cancers. We, along with several other research groups, have recently reported that UPR was induced by celastrol in several different cancers, including hepatocellular carcinoma. However, UPR status in HCC still remains unclear. The role of ER stress and autophagy in response to celastrol also has yet to be elucidated. Our results demonstrated that celastrol could cause G2/M phase rest and inhibit proliferation in HepG2 and Bel7402. Exposure to celastrol resulted in the activation of the intrinsic apoptotic pathway, via ER stress and the UPR. In murine syngeneic model studies celastrol inhibited H22 tumor growth via the induction of ER stress and apoptosis. Our study suggests that celastrol is a potential drug for HCC therapy via targeting ER-stress/UPR.

miR-145-5p inhibits epithelial-mesenchymal transition via the JNK signaling pathway by targeting MAP3K1 in non-small cell lung cancer cells

Lung cancer is one of the most common types of tumors and the leading cause of cancer-associated mortality in the world. Additionally, non-small cell lung cancer (NSCLC) accounts for ~80% of all lung cancer cases. Epithelial-mesenchymal transition (EMT) is an important cell biological process, which is associated with cancer migration, metastasis, asthma and fibrosis in the lung. In the present study, it was revealed that miR-145-5p was able to suppress EMT by inactivating the c-Jun N-terminal kinase (JNK) signaling pathway in NSCLC cells. Mitogen-activated protein kinase kinase kinase 1 (MAP3K1) was predicted and confirmed to be a novel target of miR-145-5p. Overexpression of MAP3K1 was able to reverse the inhibition of EMT induced by miR-145-5p via the JNK signaling pathway. Overall, the results revealed that miR-145-5p inhibits EMT via the JNK signaling pathway by targeting MAP3K1 in NSCLC cells.

Annexin A2 contributes to cisplatin resistance by activation of JNK-p53 pathway in non-small cell lung cancer cells

BACKGROUND

Development of resistance to therapy continues to be a serious clinical problem in lung cancer management. We previously identified that Annexin A2 is significantly up-regulated in cisplatin-resistant non-small cell lung cancer (NSCLC) A549/DDP cells. However, the exact function and molecular mechanism of Annexin A2 in cisplatin resistance of NSCLCs has not been determined.

METHODS

Western blot and qRT-PCR were performed to analyze the protein and mRNA level of indicated molecules, respectively. Immunohistochemistry was performed to analyze the expression of Annexin A2 in NSCLC tissue samples. MTS assay, Colony formation assays, AnnexinV/PI apoptosis assay, Luciferase Reporter Assay, Chromatin-immunoprecipitation, and nude mice xenograft assay were used to visualize the function of Annexin A2 on cisplatin resistance.

RESULTS

Our results demonstrated that knockdown of Annexin A2 increased cisplatin sensitivity of cisplatin-resistant A549/DDP cells both in vitro and in vivo, whereas overexpression of Annexin A2 increased cisplatin resistance of A549, H460 and H1650 cells. Moreover, we found that Annexin A2 enhanced cisplatin resistance via inhibition of cisplatin-induced cell apoptosis. Our studies showed that Annexin A2 suppressed the expression of p53 through activation of JNK/c-Jun signaling, which in turn resulted in a decrease in the expression of p53-regulated apoptotic genes p21, GADD45 and BAX, as well as p53-dependent cell apoptosis. Furthermore, we found that in NSCLC cases that Annexin A2 is highly expressed; it is positively correlated with a poor prognosis, as well as correlated with short disease-free survival for patients who received chemotherapy after surgery.

CONCLUSIONS

These data suggested that Annexin A2 induces cisplatin resistance of NSCLCs via regulation of JNK/c-Jun/p53 signaling, and provided an evidence that blockade of Annexin A2 could serve as a novel therapeutic approach for overcoming drug resistance in NSCLCs.

Triptolide and celastrol loaded silk fibroin nanoparticles show synergistic effect against human pancreatic cancer cells

Pancreatic cancer is a lethal disease with a dreadful 5-year survival rate of only 5%. In spite of several treatment options, the prognosis still remains extremely poor. Therefore, novel therapy strategies with combinations of drugs are urgently required to combat this fatal disease. Triptolide (TPL) and celastrol (CL), two main compounds in traditional Chinese medicine isolated from Thunder God Vine, have a broad range of bioactivities including anticancer activity. Silk fibroin (SF), a naturally occurring protein with several unique properties, is an ideal carrier material. In this study, we prepared TPL and CL loaded silk fibroin nanoparticles (TPL-SFNPs and CL-SFNPs) by a modified desolvation method and evaluated their synergistic effects against human pancreatic cancer cells. Both SFNPs were characterized for particle size and zeta potential. The entrapment efficiency, drug loading, and drug release profiles were evaluated by HPLC. The cytotoxicity and synergistic effect of SFNPs were investigated in MIA PaCa-2 and PANC-1 human pancreatic cells. The results showed that the particle sizes of TPL-SFNPs and CL-SFNPs were 166.4 ± 4.6 nm and 170.4 ± 2.3 nm, with a mean zeta potential -27.2 ± 2.0 mV and -25.5 ± 2.57 mV, respectively. TPL-SFNPs and CL-SFNPs have a drug loading of 57.0 ± 4.7 μg mg-1 and 63.5 ± 3.8 μg mg-1 along with an encapsulation efficiency of 81.8 ± 2.8% and 87.0 ± 5.1%, respectively. Drug release studies revealed that a rapid release of the drugs from SFNPs was observed at pH 4.5 (lysosomal pH) and a delayed release was observed at pH 7.4 (plasma pH). TPL-SFNPs (IC50 3.80 and 4.75 nM) and CL-SFNPs (IC50 0.38 and 0.64 μM) were 2-3 fold more potent against MIA PaCa-2 and PANC-1 cells than free TPL (IC50 11.25 and 11.58 nM) and CL (IC50 0.84 and 1.23 μM). Furthermore, co-treatment with TPL-SFNPs and CL-SFNPs increased the growth inhibition of the same cells significantly in comparison with TPL-SFNPs or CL-SFNPs alone. Almost all combination index (CI) values, calculated using the CompuSyn software, were <1, suggesting that the growth inhibition effect of TPL-SFNPs in combination with CL-SFNPs was synergistic rather than additive, further suggesting that this novel combination may offer a potential treatment for pancreatic cancer.

Celastrol: A Spectrum of Treatment Opportunities in Chronic Diseases

The identification of new bioactive compounds derived from medicinal plants with significant therapeutic properties has attracted considerable interest in recent years. Such is the case of the Tripterygium wilfordii (TW), an herb used in Chinese medicine. Clinical trials performed so far using its root extracts have shown impressive therapeutic properties but also revealed substantial gastrointestinal side effects. The most promising bioactive compound obtained from TW is celastrol. During the last decade, an increasing number of studies were published highlighting the medicinal usefulness of celastrol in diverse clinical areas. Here we systematically review the mechanism of action and the therapeutic properties of celastrol in inflammatory diseases, namely, rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel diseases, osteoarthritis and allergy, as well as in cancer, neurodegenerative disorders and other diseases, such as diabetes, obesity, atherosclerosis, and hearing loss. We will also focus in the toxicological profile and limitations of celastrol formulation, namely, solubility, bioavailability, and dosage issues that still limit its further clinical application and usefulness.

MicroRNA-451 regulates chemoresistance in renal cell carcinoma by targeting ATF-2 gene

Renal cell carcinoma (RCC) is a malignant tumor, which severely threatens human's life, moreover, the multi-drug resistance (MDR) under RCC undoubtedly strengthen the difficulties in the treatment. MiR-451 has been considered to play an important role in regulation of MDR in several cancers, but the role of it in MDR of RCC has not been explored. This study aims to explore the mechanism of miR-451 as a target to regulate chemotherapy resistance, which is crucial for further exploring novel therapy for RCC. Two human cell lines (ACHN and GRC-1) were performed in this study and adriamycin (ADM) was used to construct MDR cell lines. qRT-PCR was used to determine the mRNA expression of miR-451 and ATF-2. Weston blot was used to determine protein expression. MTT assay and flow cytometry were used for assessing cell viability and apoptosis, individually. Luciferase reporter assay was used to detect the targeting of miR-451 and ATF-2. Results presented that the expression of miR-451 was higher in low MDR cell line (ACHN) comparing with the high MDR cell line (GRC-1), while the expression of ATF-2 revealed an opposite results. MiR-451 targeted ATF-2 and regulated its expression. Overexpression of miR-451 strengthened drug resistance, decreased cell viability, and increased cell apoptosis of GRC-1 pretreated by ADM, while overexpressed ATF-2 reversed the effect induced by miR-451 overexpression. Then miR-451 knockdown improved drug susceptibility, decreased cell apoptosis, and increased cell viability of ACHN induced by ADM, however, ATF-2 suppression reversed the low rate of cell apoptosis and high rate of cell viability induced by miR-451 knockdown. Our results revealed that miR-451 regulates the drug resistance of RCC by targeting ATF-2 gene, which might be critical for overcoming MDR in RCC patients. Impact statement This is the first study to emphasize the expression of miR-451 on regulating multi-drug resistance (MDR) in renal cell carcinoma (RCC). Our study found that miR-451 regulates the drug resistance of RCC by targeting ATF-2, which might be critical for overcoming MDR in RCC patients. This study not only provides solid theory foundation for the clinical therapy, but also offers unique insights for the further RCC research. Furthermore, the study helps us to understand the mechanism of MDR, which was crucial for identifying the chemoresistance on several related tumors.

Celastrol ameliorates Cd-induced neuronal apoptosis by targeting NOX2-derived ROS-dependent PP5-JNK signaling pathway

Celastrol, a plant-derived triterpene, has neuroprotective benefit in the models of neurodegenerative disorders that are characterized by overproduction of reactive oxygen species (ROS). Recently, we have reported that cadmium (Cd) activates c-Jun N-terminal kinase (JNK) pathway leading to neuronal cell death by inducing ROS inactivation of protein phosphatase 5 (PP5), and celastrol prevents Cd-activated JNK pathway against neuronal apoptosis. Therefore, we hypothesized that celastrol could hinder Cd induction of ROS-dependent PP5-JNK signaling pathway from apoptosis in neuronal cells. Here, we show that celastrol attenuated Cd-induced expression of NADPH oxidase 2 (NOX2) and its regulatory proteins (p22^phox , p40^phox , p47^phox , p67^phox , and Rac1), as well as the generation of ROS in PC12 cells and primary neurons. Also, N-acetyl-l-cysteine, a ROS scavenger, potentiated celastrol's inhibition of the events in the cells triggered by Cd, implying neuroprotection by celastrol via blocking Cd-evoked NOX2-derived ROS. Further research revealed that celastrol was involved in the regulation of PP5 inactivation and JNK/c-Jun activation induced by Cd, as celastrol prevented Cd from reducing PP5 expression, and over-expression of wild-type PP5 or dominant negative c-Jun strengthened celastrol's inhibition of Cd-induced phosphorylation of JNK and/or c-Jun, as well as apoptosis in neuronal cells. Of importance, inhibiting NOX2 with apocynin or silencing NOX2 by RNA interference enhanced the inhibitory effects of celastrol on Cd-induced inactivation of PP5, activation of JNK/c-Jun, ROS, and apoptosis in the cells. Furthermore, we noticed that expression of wild-type PP5 or dominant negative c-Jun, or pretreatment with JNK inhibitor SP600125 reinforced celastrol's suppression of Cd-induced NOX2 and its regulatory proteins, and consequential ROS in neuronal cells. These findings indicate that celastrol ameliorates Cd-induced neuronal apoptosis via targeting NOX2-derived ROS-dependent PP5-JNK signaling pathway. Our data highlight a beneficial role of celastrol in the prevention of Cd-induced oxidative stress and neurodegenerative diseases.

Compounds From Celastraceae Targeting Cancer Pathways and Their Potential Application in Head and Neck Squamous Cell Carcinoma: A Review

Squamous cell carcinoma of the head and neck is one of the most common cancer types worldwide. It initiates on the epithelial lining of the upper aerodigestive tract, at most instances as a consequence of tobacco and alcohol consumption. Treatment options based on conventional therapies or targeted therapies under development have limited efficacy due to multiple genetic alterations typically found in this cancer type. Natural products derived from plants often possess biological activities that may be valuable in the development of new therapeutic agents for cancer treatment. Several genera from the family Celastraceae have been studied in this context. This review reports studies on chemical constituents isolated from species from the Celastraceae family targeting cancer mechanisms studied to date. These results are then correlated with molecular characteristics of head and neck squamous cell carcinoma in an attempt to identify constituents with potential application in the treatment of this complex disease at the molecular level.

The P38α rs3804451 Variant Predicts Chemotherapy Response and Survival of Patients with Non-Small Cell Lung Cancer Treated with Platinum-Based Chemotherapy

The JNK and P38α pathways play an important role in the sensitivity and outcomes of chemotherapy. We hypothesize that functional single nucleotide polymorphisms (SNPs) of genes of these pathways modulate outcomes of patients with advanced non-small cell lung cancer (NSCLC) treated with first-line platinum-based chemotherapy (PBC). We selectively genotyped 11 independent, potentially functional SNPs of 9 genes in the JNK and P38α pathways first in a discovery group of 355 patients with advanced NSCLC treated with PBC, and we evaluated their associations with progression-free survival (PFS) and overall survival (OS) by Cox proportional hazards regression analysis. Then, resultant significant SNPs were further validated in a replication group of 355 patients. In both discovery and validation groups as well as their combined analysis, the MAPK14 rs3804451GA/AA genotypes showed a strong association with a reduced PFS (adjusted hazards ratio [HR]=1.39; 95% confidence interval [CI]=1.16-1.66; P=.0003) and OS (adjusted HR=1.41; 95% CI=1.11-1.80; P=.005) compared with the wild-type GG genotype. In contrast, patients with or without the MAPK14 rs3804451A allele had no significant difference in OS in response to tyrosine-kinase inhibitor treatment (adjusted HR=0.86; 95% CI=0.56-1.33; P=.505). The present study provides evidence that the MAPK14 rs3804451 G>A variant may modulate survival outcomes in patients with advanced NSCLC treated with PBC. Larger studies of additional patient populations are needed to validate our findings.

Synergistic anticancer effects of triptolide and celastrol, two main compounds from thunder god vine

Triptolide and celastrol are two main active compounds isolated from Thunder God Vine with the potent anticancer activity. However, the anticancer effect of triptolide in combination with celastrol is still unknown. In the present study, we demonstrated that the combination of triptolide with celastrol synergistically induced cell growth inhibition, cell cycle arrest at G2/M phase and apoptosis with the increased intracellular ROS accumulation in cancer cells. Pretreatment with ROS scavenger N-acetyl-L-cysteine dramatically blocked the apoptosis induced by co-treatment with triptolide and celastrol. Treatment with celastrol alone led to the decreased expressions of HSP90 client proteins including survivin, AKT, EGFR, which was enhanced by the addition of triptolide. Additionally, the celastrol-induced expression of HSP70 and HSP27 was abrogated by triptolide. In the nude mice with xenograft tumors, the lower-dose combination of triptolide with celastrol significantly inhibited the growth of tumors without obvious toxicity. Overall, triptolide in combination with celastrol showed outstanding synergistic anticancer effect in vitro and in vivo, suggesting that this beneficial combination may offer a promising treatment option for cancer patients.

Combined niclosamide with cisplatin inhibits epithelial-mesenchymal transition and tumor growth in cisplatin-resistant triple-negative breast cancer

Women with triple-negative breast cancer have worse prognosis compared to other breast cancer subtypes. Acquired drug resistance remains to be an important reason influencing triple-negative breast cancer treatment efficacy. A prevailing theory postulates that the cancer resistance and recurrence results from a subpopulation of tumor cells with stemness program, which are often insensitive to cytotoxic drugs such as cisplatin. Recent studies suggested that niclosamide, an anti-helminthic drug, has potential therapeutic activities against breast cancer stem cells, which prompts us to determine its roles on eliminating cisplatin-resistant cancer cells. Hence, we established a stable cisplatin-resistant MDA-MB-231 cell line (231-CR) through continuously exposure to increasing concentrations of cisplatin (5-20 μmol/l). Interestingly, 231-CR exhibited properties associated to epithelial-mesenchymal transition with enhanced invasion, preserved proliferation, increased mammosphere formation, and reduced apoptosis compared to naive MDA-MB-231 sensitive cells (231-CS). Importantly, niclosamide or combination with cisplatin inhibited both 231-CS and 231-CR cell proliferation in vitro. In addition, niclosamide reversed the EMT phenotype of 231-CR by downregulation of snail and vimentin. Mechanistically, niclosamide treatment in combination with or without cisplatin significantly inhibited Akt, ERK, and Src signaling pathways. In vivo study showed that niclosamide or combination with cisplatin could repress the growth of xenografts originated from either 231-CS or 231-CR cells, with prominent suppression of Ki67 expression. These findings suggested that niclosamide might serve as a novel therapeutic strategy, either alone or in combination with cisplatin, for triple-negative breast cancer treatment, especially those resistant to cisplatin.