Akt is the downstream target of GRP78 in mediating cisplatin resistance in ER stress-tolerant human lung cancer cells

Resistance to the platinum‑based chemotherapeutic drugs in oral cancer: Focus on the role of p22phox (Review)

Oral cancer, commonly known as oral squamous cell carcinoma (OSCC), is an aggressive malignancy in the oral cavity with a poor prognosis and survival rate, particularly at the advanced stages. Oral cancer represents one of the most widespread cancers worldwide, in which the prevalence is particularly high in South and Southeast Asia. While the incidence and mortality rates continue to increase over the past decades, oral cancer treatment can be challenging and at times ineffective, largely due to drug resistance. To date, platinum-based drugs, such as cisplatin, remain the mainstay of chemotherapy for patients with oral cancer. However, long-term exposure to cisplatin inevitably leads to the development of resistance to the drug, which is still a major issue to overcome in oral cancer treatment. The molecular mechanisms of cisplatin resistance in oral cancer have been extensively studied in recent years and the present review places specific emphasis on a novel mechanism of resistance to the platinum drugs mediated by p22phox, an endoplasmic reticulum membrane protein. In addition to delineating the unique p22phox-dependent cisplatin resistance, the present review compares and contrasts the resistance mechanism to its current counterparts. Finally, with the goal of tackling the problem of chemotherapy resistance in oral cancer, various strategies are presented that may counteract p22phox-dependent cisplatin resistance, which may potentially improve the efficacy of the platinum-based drugs and warrant future clinical validation.

Decoding contextual crosstalk: revealing distinct interactions between non-coding RNAs and unfolded protein response in breast cancer

Breast cancer is significantly influenced by endoplasmic reticulum (ER) stress, impacting both its initiation and progression. When cells experience an accumulation of misfolded or unfolded proteins, they activate the unfolded protein response (UPR) to restore cellular balance. In breast cancer, the UPR is frequently triggered due to challenging conditions within tumors. The UPR has a dual impact on breast cancer. On one hand, it can contribute to tumor growth by enhancing cell survival and resistance to programmed cell death in unfavorable environments. On the other hand, prolonged and severe ER stress can trigger cell death mechanisms, limiting tumor progression. Furthermore, ER stress has been linked to the regulation of non-coding RNAs (ncRNAs) in breast cancer cells. These ncRNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), play essential roles in cancer development by influencing gene expression and cellular processes. An improved understanding of how ER stress and ncRNAs interact in breast cancer can potentially lead to new treatment approaches. Modifying specific ncRNAs involved in the ER stress response might interfere with cancer cell survival and induce cell death. Additionally, focusing on UPR-associated proteins that interact with ncRNAs could offer novel therapeutic possibilities. Therefore, this review provides a concise overview of the interconnection between ER stress and ncRNAs in breast cancer, elucidating the nuanced effects of the UPR on cell fate and emphasizing the regulatory roles of ncRNAs in breast cancer progression.

Targeting PAK4 reverses cisplatin resistance in NSCLC by modulating ER stress

Chemoresistance poses a significant impediment to effective treatments for non-small-cell lung cancer (NSCLC). P21-activated kinase 4 (PAK4) has been implicated in NSCLC progression by invasion and migration. However, the involvement of PAK4 in cisplatin resistance is not clear. Here, we presented a comprehensive investigation into the involvement of PAK4 in cisplatin resistance within NSCLC. Our study revealed enhanced PAK4 expression in both cisplatin-resistant NSCLC tumors and cell lines. Notably, PAK4 silencing led to a remarkable enhancement in the chemosensitivity of cisplatin-resistant NSCLC cells. Cisplatin evoked endoplasmic reticulum stress in NSCLC. Furthermore, inhibition of PAK4 demonstrated the potential to sensitize resistant tumor cells through modulating endoplasmic reticulum stress. Mechanistically, we unveiled that the suppression of the MEK1-GRP78 signaling pathway results in the sensitization of NSCLC cells to cisplatin after PAK4 knockdown. Our findings establish PAK4 as a promising therapeutic target for addressing chemoresistance in NSCLC, potentially opening new avenues for enhancing treatment efficacy and patient outcomes.

Expression and gene regulatory network of S100A16 protein in cervical cancer cells based on data mining

S100A16 protein belongs to the S100 family of calcium-binding proteins, which is widely distributed in human tissues and highly conserved. S100 calcium-binding proteins possess broad biological functions, such as cancer cell proliferation, apoptosis, tumor metastasis, and inflammation (Nat Rev Cancer 15:96-109, 2015). The S100A16 protein was initially isolated from a cell line derived from astrocytoma. The S100A16 protein, consisting of 103 amino acids, is a small acidic protein with a molecular weight of 11,801.4 Da and an isoelectric point (pI) of 6.28 (Biochem Biophys Res Commun 313:237-244, 2004). This protein exhibits high conservation among mammals and is widely expressed in various human tissues (Biochem Biophys Res Commun 322:1111-1122, 2004). Like other S100 proteins, S100A16 contains two EF-hand motifs that form a helix-loop-helix structural domain. The N-terminal domain and the C-terminal domain of S100A16 are connected by a "hinge" linker.S100A16 protein exhibits distinct characteristics that distinguish it from other S100 proteins. A notable feature is the presence of a single functional Ca2 + binding site located in the C-terminal EF-hand, consisting of 12 amino acids per protein monomer (J Biol Chem 281:38905-38917, 2006). In contrast, the N-terminal EF-hand of S100A16 comprises 15 amino acids instead of the typical 14, and it lacks the conserved glutamate residue at the final position. This unique attribute may contribute to the impaired Ca2 + binding capability in the N-terminal region (J Biol Chem 281:38905-38917, 2006). Studies have shown an integral role of S100 calcium-binding proteins in the diagnosis, treatment, and prognosis of certain diseases (Cancers 12:2037, 2020). Abnormal expression of S100A16 protein is implicated in the progression of breast and prostate cancer, but an inhibitor of oral cancer and acute lymphoblastic leukemia tumor cell proliferation (BMC Cancer 15:53, 2015; BMC Cancer 15:631, 2015). Tu et al. (Front Cell Dev Biol 9:645641, 2021) indicate that the overexpression of S100A16 mRNA in cervical cancer(CC) such as cervical squamous cell carcinoma and endocervical adenocarcinoma as compared to the control specimens. Tomiyama N. and co-workers (Oncol Lett 15:9929-9933, 2018) (Tomiyama, N) investigated the role of S100A16 in cancer stem cells using Yumoto cells (a CC cell line),The authors found upregulation of S100A16 in Yumoto cells following sphere formation as compared to monolayer culture.Despite a certain degree of understanding, the exact biological function of S100A16 in CC is still unclear. This article explores the role of S100A16 in CC through a bioinformatics analysis. Referencing the mRNA expression and SNP data of cervical cancer available through The Cancer Genome Atlas (TCGA) database, we analyzed S100A16 and its associated regulatory gene expression network in cervical cancer. We further screened genes co-expressed with S100A16 to hypothesize their function and relationship to the S100A16 cervical cancer phenotype.Our results showed that data mining can effectively elucidate the expression and gene regulatory network of S100A16 in cervical cancer, laying the foundation for further investigations into S100A16 cervical tumorigenesis.

Synergistic anticancer activity of cisplatin combined with tannic acid enhances apoptosis in lung cancer through the PERK-ATF4 pathway

BACKGROUND

Cisplatin (CDDP) is a common anticancer drug whose side effects limit its clinical applications. Tannins (TA) are plant-derived polyphenols that inhibit tumor growth in different types of cancer. Here, we evaluated the anticancer effect of TA combined with CDDP on lung cancer cell lines (GLC-82 and H1299) and investigated the underlying molecular mechanism of endoplasmic reticulum (ER) stress-induced apoptosis.

METHODS

Cell lines were treated with CDDP, TA, and CDDP + TA, and the effect of the combination was assessed using MTT assay and observed under light and fluorescence microscopes. Cell apoptosis was detected by flow cytometry, and the levels of ERS apoptosis pathway related genes were valuated by qRT-PCR and western blotting. The effects of the drug combination on the tumors of nude mice injected with H1299 cells were investigated, and the expression of key factors in the ER stress apoptotic pathway was investigated.

RESULTS

The combination of CDDP and TA significantly inhibited lung cancer cell viability indicating a synergistic antitumoral effect. The mRNA and protein expression levels of key ER stress factors in the CDDP + TA group were considerably higher than those in the CDDP and TA groups, the tumor volume in tumor-bearing mice was the smallest, and the number of apoptotic cells and the protein expression levels of the key ER stress in the combination group were considerably higher.

CONCLUSIONS

The combination of TA and CDDP may produce synergistic antitumoral effects mediated by the PERK-ATF4-CHOP apoptotic axis, suggesting a novel adjuvant treatment for lung cancer.

Bufalin serves as a pharmaceutic that mitigates drug resistance

Intrinsic or acquired drug resistance of tumor cells is the main cause of tumor chemotherapy failure and tumor-related death. Bufalin (BF) is the main active monomer component extracted from the Traditional Chinese Medicine Toad venom (secretions of glands behind the ears and epidermis of bufo gargarizans and Bufo Melanostictus Schneider). It is a cardiotonic steroid with broad-spectrum anti-cancer effects and has been widely used against various malignant tumors in clinical practice. Pharmacological studies also found that BF has the effect of reversing drug resistance, which provides a new perspective for the application of Traditional Chinese Medicine as a chemosensitizer in cancer therapy. This article provides an extensive search and summary of published research on mitigating drug resistance to BF and reviews its potential mechanisms.

The role of endoplasmic reticulum stress in the regulation of long noncoding RNAs in cancer

Cancer cells must overcome a variety of external and internal stresses to survive and proliferate. These unfavorable conditions include the accumulation of mutations, nutrient deficiency, oxidative stress, and hypoxia. These stresses can cause aggregation of misfolded proteins inside the endoplasmic reticulum. Under these conditions, the cell undergoes endoplasmic reticulum stress (ER-stress), and consequently initiates the unfolded protein response (UPR). Activation of the UPR triggers transcription factors and regulatory factors, including long noncoding RNAs (lncRNAs), which control the gene expression profile to maintain cellular stability and hemostasis. Recent investigations have shown that cancer cells can ensure their survival under adverse conditions by the UPR affecting the expression of lncRNAs. Therefore, understanding the relationship between lncRNA expression and ER stress could open new avenues, and suggest potential therapies to treat various types of cancer.

MiR-181c sensitizes ovarian cancer cells to paclitaxel by targeting GRP78 through the PI3K/Akt pathway

Primary cytoreductive surgery with platinum-taxane-based chemotherapy is the standard treatment for ovarian cancer (OC) patients; however, resistance to chemotherapy is a contributing factor to OC mortality. Paclitaxel (PTX), the most widely used taxane, has become the first-line drug against OC. The molecular mechanism of PTX resistance is different from that of platinum-based agents and is still not completely elucidated. Our previous study showed that glucose-regulated protein 78 (GRP78) is involved in the resistance of OC cells to PTX. However, little is known regarding endogenous inhibitors of this gene. MicroRNAs (miRNAs) play critical roles in the regulation of gene expression; therefore, we sought to identify miRNA(s) with potential to target GRP78 under the hypothesis that miRNA(s) could serve as potential therapeutic targets. Here, we show that miR-181c, predicted to target GRP78, was downregulated in PTX-resistant OC cells and tissues. MiR-181c downregulated GRP78 expression and induced apoptosis by directly targeting its 3'-untranslated region (UTR). Overexpression of miR-181c sensitized resistant OC to PTX by inhibiting the PI3K/Akt pathway in vitro and in vivo. Taken together, our findings indicate that the delivery of miR-181c can efficiently suppress GRP78 expression and GRP78-mediated PTX resistance in OC and suggest that this strategy has therapeutic potential.

Transketolase promotes colorectal cancer metastasis through regulating AKT phosphorylation

Transketolase (TKT) which is an important metabolic enzyme in the pentose phosphate pathway (PPP) participates in maintaining ribose 5-phosphate levels. TKT is necessary for maintaining cell growth. However, we found that in addition to this, TKT can also affect tumor progression through other ways. Our previous study indicate that TKT could promote the development of liver cancer by affecting bile acid metabolism. And in this study, we discovered that TKT expression was remarkably upregulated in colorectal cancer, abnormal high expression of TKT is associated with poor prognosis of colorectal cancer. Additionally, TKT promoted colorectal cancer cell growth and metastasis. Further study demonstrated that TKT interacted with GRP78 and promoted colorectal cancer cell glycolysis through increasing AKT phosphorylation, thereby enhancing colorectal cancer cell metastasis. Thus, TKT is expected to become an indicator for judging the prognosis of colorectal cancer, and provide a theoretical basis for drug development of new treatment targets for colorectal cancer.

Circ-CUL2/microRNA-888-5p/RB1CC1 axis participates in cisplatin resistance in NSCLC via repressing cell advancement

Elevated evidences manifest that circular RNAs (circRNAs) are vital in human tumor advancement and chemotherapy resistance. The study was to explore the character of Circ-CUL2 in non-small cell lung cancer (NSCLC). Firstly, the expression of circ-CUL2, microRNA (miR)-888-5p and RB1CC1 was detected in human NSCLC tissues and cell lines by reverse transcription quantitative polymerase chain reaction or Western blot. Then, cell counting kit (CCK)-8, plate clone, Transwell assays, and flow cytometry were applied to separately detect the impacts of circ-CUL2 on proliferation, migration, invasion, apoptosis and cisplatin (DDP) resistance of A549/DDP cells. In this study, exploration of the biological function of Circ-CUL2 was via the Circ-CUL2/miR-888-5p/RB1CC1 axis. The results manifested circ-CUL2 and RB1CC1 were down-regulated in NSCLC tissues and cell lines, while miR-888-5p was up-regulated. Elevated Circ-CUL2 or refrained miR-888-5p repressed A549/DDP cell progression with depressive DDP resistance. Circ-CUL2 curbed miR-888-5p, which targeted RB1CC1. Restrained RB1CC1 turned around the impacts of Circ-CUL2 on the cells. All in all, Circ-CUL2 is anti-NSCLC via miR-888-5p/RB1CC1 axis, enhancing the sensitivity of A549/DDP cells to DDP. Hence, Circ-CUL2 is supposed to be a novel biomarker offering a brand-new strategy for NSCLC therapy.

Disulfiram/copper shows potent cytotoxic effects on myelodysplastic syndromes via inducing Bip-mediated apoptosis and suppressing autophagy

Patients with myelodysplastic syndromes (MDS) who resist or fail to respond to hypomethylating agents (HMAs) show very poor outcomes and have no effective treatment strategies. Therefore, new therapeutic approaches are urgently needed for MDS patients harboring adverse prognostic factors. Repurposing disulfiram (DSF), an alcohol-abuse drug, with or without Copper (Cu) has attracted considerable attentions as a candidate anti-tumor therapy in diverse malignancies. However, the effect of DSF in the presence or absence of Cu on MDS has not been reported yet. In this study, we found that monotherapy with DSF showed mild cytotoxic effects on MDS preclinical models. However, the anti-tumor activity of DSF was significantly enhanced in the presence of Cu in MDS in vitro and in vivo with minimal safety profiles. DSF/Cu combination blocked MDS cell cycle progression at the G0/G1 phase, accompanied by reduction of the S phase. Accordingly, co-treatment with DSF and Cu downregulated the expression of Cyclin D1 and Cyclin A2, whereas this combination upregulated the level of P21 and P27. Mechanistically, the anti-MDS effectiveness of DSF/Cu was potentially associated with activation of the ER stress-related Bip pathway and inactivation of the Akt pathway. In addition, inhibition of autophagy process also contributed to the cytotoxicity of DSF/Cu in MDS cells. In conclusion, these findings provide impressive evidence that the DSF/Cu complex shows potent anti-tumor efficacies on MDS preclinical models, representing a potential alternative therapy for MDS patients and warranting further investigation in clinical contexts.

GRP78 in lung cancer

Glucose-regulating protein 78 (GRP78) is a molecular chaperone in the endoplasmic reticulum (ER) that promotes folding and assembly of proteins, controls the quality of proteins, and regulates ER stress signaling through Ca²⁺ binding to the ER. In tumors, GRP78 is often upregulated, acting as a central stress sensor that senses and adapts to changes in the tumor microenvironment, mediating ER stress of cancer cells under various stimulations of the microenvironment to trigger the folding protein response. Increasing evidence has shown that GRP78 is closely associated with the progression and poor prognosis of lung cancer, and plays an important role in the treatment of lung cancer. Herein, we reviewed for the first time the functions and mechanisms of GRP78 in the pathological processes of lung cancer, including tumorigenesis, apoptosis, autophagy, progression, and drug resistance, giving a comprehensive understanding of the function of GRP78 in lung cancer. In addition, we also discussed the potential role of GRP78 as a prognostic biomarker and therapeutic target for lung cancer, which is conducive to improving the assessment of lung cancer and the development of new therapeutic interventions.

Thymoquinone Potentiated the Anticancer Effect of Cisplatin on Hepatic Tumorigenesis by Modulating Tissue Oxidative Stress and Endoplasmic GRP78/CHOP Signaling

Thymoquinone (TQ) combined with Cisplatin may augment its anticancer effect on hepatocellular carcinoma (HCC), through oxidative stress mitigation and endoplasmic reticulum (ER) protein modulation. Fifty adult male Wistar albino rats were assigned into five equal experimental groups (n = 10); 1) Control, 2) diethylnitrosamine/carbon tetrachloride-induced liver tumorigenesis model (HCC), 3) Cisplatin (2 mg.kg^-1ip) treated rats, 4) Thymoquinone treated group (20 mg.kg^-1oral), and 5) group treated with both drugs as in Groups 3 and 4. Treatment regimens started following model confirmation and continued for 4 weeks. In the HCC model, we detected elevated ER chaperone glucose-regulated protein-78 (GRP78) and reduced C/EBP-homologous protein (CHOP)-mediated apoptosis that was accompanied by the elevated alpha-fetoprotein (AFP) marker and deteriorated liver functions. Our original results indicated that Thymoquinone potentiated the pro-apoptotic effect of cisplatin by modulating GRP78/CHOP signaling. Cisplatin/TQ reduced the elevated GRP78 and induced CHOP-mediated apoptosis in the diseased liver tissues compared to the HCC and Cisplatin treated groups. Cisplatin/TQ combination normalized AFP levels and improved liver functions compared to both HCC and cisplatin groups alone. In conclusion, Thymoquinone enhanced the efficacy of Cisplatin in HCC treatment by modulating the GRP78/CHOP/caspase-3 pathway. Thymoquinone is recommended to achieve greater therapeutic benefits and reduce the cisplatin hepatotoxicity in HCC management.

Adaptive response of resistant cancer cells to chemotherapy

Despite advances in cancer therapeutics and the integration of personalized medicine, the development of chemoresistance in many patients remains a significant contributing factor to cancer mortality. Upon treatment with chemotherapeutics, the disruption of homeostasis in cancer cells triggers the adaptive response which has emerged as a key resistance mechanism. In this review, we summarize the mechanistic studies investigating the three major components of the adaptive response, autophagy, endoplasmic reticulum (ER) stress signaling, and senescence, in response to cancer chemotherapy. We will discuss the development of potential cancer therapeutic strategies in the context of these adaptive resistance mechanisms, with the goal of stimulating research that may facilitate the development of effective cancer therapy.

Interplay between endoplasmic reticulum stress and non-coding RNAs in cancer

To survive, cancer cells are subjected to various internal and external adverse factors, including genetic mutations, hypoxia, nutritional deficiencies, and drug toxicity. All of these factors result in the accumulation of unfolded proteins in the endoplasmic reticulum, which leads to a condition termed endoplasmic reticulum stress (ER stress) and triggers the unfolded protein response (UPR). UPR downstream components strictly control transcription and translation reprogramming to ensure selective gene expression, including that of non-coding RNA (ncRNAs), to adapt to adverse environments. NcRNAs, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), play important roles in regulating target gene expression and protein translation, and their aberrant expression is related to tumor development. Dysregulation of ncRNAs is involved in the regulation of various cellular characteristics of cancer cells, including growth, apoptosis, metastasis, angiogenesis, drug sensitivity, and tumor stem cell properties. Notably, ncRNAs and ER stress can regulate each other and collaborate to determine the fate of tumor cells. Therefore, investigating the interaction between ER stress and ncRNAs is crucial for developing effective cancer treatment and prevention strategies. In this review, we summarize the ER stress-triggered UPR signaling pathways involved in carcinogenesis followed by the mutual regulation of ER stress and ncRNAs in cancer, which provide further insights into the understanding of tumorigenesis and therapeutic strategies.

Rosuvastatin and simvastatin attenuate cisplatin-induced cardiotoxicity via disruption of endoplasmic reticulum stress-mediated apoptotic death in rats: targeting ER-Chaperone GRP78 and Calpain-1 pathways

Cisplatin (CP) is a powerful antineoplastic chemotherapeutic agent with broad-spectrum properties. Acute and cumulative cardiotoxicity are major limiting factors for CP therapy. Various pathogenic pathways have been suggested to CP-induced cardiotoxicity; oxidative damage, ER stress, and programmed cell death/apoptosis. The present study aimed to assess the signaling mechanisms related to the advantageous effects of rosuvastatin (RSV) and simvastatin (SMV) against CP-related cardiac ER stress dependent apoptotic death in rats. Acute cardiotoxicity was induced by a single dose of CP (10 mg/kg, i.p.) on the 10th day of the experiment. RSV (10 mg/ kg/day) and SMV (10 mg/kg/day) were orally administered for 15 days. CP-treated rats showed significant alterations in electrocardiographic recordings and elevation in serum cardiac function biomarkers; troponin T content, lactate dehydrogenase and creatine kinase-MB levels as well as boost in the cardiac oxidative stress biomarkers. In addition, CP exposure resulted in GRP78 induction; an ER stress and elevation marker at calpain-1 content as well as activation of activated caspase-3 (ACASP3) and caspase-12 were reflected on CP-triggered apoptosis evidenced by elevation in the Bax/Bcl-2 ratio. However, RSV and SMV administration mitigate those adverse CP effects. Statins administration prominently alleviated CP-induced cardiac abnormalities exerting improvement in the ECG pattern and cardiac enzyme biomarkers. Interestingly, statins; RSV and SMV, disrupted CP-induced ER stress and the consequent apoptotic cell death evidenced by downregulation of ER-chaperone GRP78, calpain-1, ACASP3 and caspase-12 as well as decline in the Bax/Bcl-2 ratio. From all the previous findings, it can be suggested that statins namely; RSV and SMV, play protective role against CP-induced cardiac injury by regulating ER stress-mediated apoptotic pathways.

A zinc finger family protein, ZNF263, promotes hepatocellular carcinoma resistance to apoptosis via activation of ER stress-dependent autophagy

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide. Endoplasmic reticulum stress (ERS) is generally activated in HCC and is important for the sensitivity of HCC to anticancer drugs. ERS-dependent autophagy is a crucial mechanism affecting the sensitivity of HCC to anticancer drugs, but the mechanism by which ERS regulates autophagy is not well understood. Zinc finger protein 263 (ZNF263) is a transcription factor member of the zinc finger family. However, its functional role in HCC remains to be studied. In the current study, we investigated the role of ZNF263 in regulating ERS-induced chemoresistance in HCC and its possible mechanism. We found that ZNF263 was the most significant ERS-specific super-enhancer bounding transcriptional factor and was up-regulated in HCC patients and cell lines. Further, ZNF263 expression correlated with ERS, clinical stage and shorter survival in HCC patients. ZNF263 knockdown by RNA interference results in decreased proliferation, apoptosis resistance, and chemoresistance. Further study showed that ZNF263 increased chemoresistance by activating ERS-related autophagy. In conclusion, our study highlights ZNF263 as a functional ERS-related tumor activator and indicates it as a potential target for HCC therapy.

Astragaloside IV sensitizes non-small cell lung cancer cells to cisplatin by suppressing endoplasmic reticulum stress and autophagy

Background

Cisplatin is an effective chemotherapeutic drug for treating various cancers including non-small cell lung cancer (NSCLC), but resistance to cisplatin remains the main limitation to its use in clinic. Astragaloside IV (AS-IV), which is derived from Astragalus membranaceus, has been proven to participate in various anti-cancer activities including anti-cancer, anti-oxidative, and anti-inflammatory functions.

Method

In this study, we explored the role of AS-IV in cisplatin chemoresistance to NSCLC cells by establishing cisplatin-resistant the NSCLC cell lines, A549^Cis and H1299^Cis.

Results

Cisplatin inhibited viability and promoted apoptosis of A549^Cis and H1299^Cis cells in a dose-dependent manner. In addition, cisplatin upregulated the levels of autophagy-related proteins (Beclin1, LC3 II/I) and endoplasmic reticulum (ER) stress-related proteins (glucose regulated protein 78: GRP78, protein kinase R (PKR)-like endoplasmic reticulum kinase: PERK), indicating that cisplatin caused autophagy and ER stress in NSCLC cells. However, treatment combined with AS-IV dose-dependently suppressed cell viability and increased the cell apoptosis rate in A549^Cis and H1299^Cis cells, suggesting that AS-IV elevated the anti-tumor role of cisplatin in NSCLC cells. AS-IV treatment suppressed the expression of GRP78 and Beclin1. Inhibition of ER stress or autophagy both counteracted the inhibitory effect of AS-IV on chemoresistance to cisplatin in NSCLC cells.

Conclusions

AS-IV sensitized NSCLC cells to cisplatin through suppressing ER stress and autophagy. This study provides a novel strategy of cisplatin combined with AS-IV for the treatment of cisplatin-resistant NSCLC patients.

Long noncoding RNA LINC00461 mediates cisplatin resistance of rectal cancer via miR-593-5p/CCND1 axis

On account of the acquired drug resistance, the potency of cisplatin-based chemotherapy is far from satisfactory in rectal cancer. Increasing evidence has highlighted the crucial function of aberrantly expressed lncRNAs on the cisplatin resistance in multiple cancers. This research was the first attempt to decipher the underlying function and mechanism of long intergenic non-protein coding RNA 461 (LINC00461) in rectal cancer and also its relation to cisplatin resistance of rectal cancer. Data from this study revealed that LINC00461 expression was upregulated in rectal cancer cells. LINC00461 depletion restrained rectal cancer progression and sensitized rectal cancer cells to cisplatin. Molecular mechanism assays testified that LINC00461 bound with miR-593-5p. Besides, miR-593-5p upregulation improved the sensitivity of rectal cancer cells to cisplatin. Additionally, cyclin D1 (CCND1) was manifested to be a downstream target of miR-593-5p. Furthermore, CCND1 upregulation could reverse the effect of LINC00461 downregulation on rectal cancer progression and cisplatin resistance of rectal cancer. To sum up, LINC00461 mediates cisplatin resistance of rectal cancer by targeting miR-593-5p/CCND1 axis, shedding new light on the treatment of rectal cancer.

Knockdown of circ-ABCB10 promotes sensitivity of lung cancer cells to cisplatin via miR-556-3p/AK4 axis

BACKGROUND

Due to the acquired drug resistance, the potency of cisplatin-based chemotherapy is limited in lung cancer, which is a big obstacle in clinical treatment of lung cancer. Abundant evidence has revealed that circular RNAs (circRNAs) exerted facilitating or suppressive function on the tumorigenesis of multiple cancers. The oncogenic role of circ-ABCB10 in breast cancer and clear cell renal cell carcinoma has been validated in recent researches. However, the regulatory mechanism of circ-ABCB10 and its relation to cellular sensitivity to cisplatin in lung cancer is poorly understood.

METHODS

The expression and characteristic of circ-ABCB10 were analyzed by RT-qPCR and nucleic acid electrophoresis. CCK-8, colony formation, TUNEL and transwell assays were applied to probe the role of FOXD3-AS1 in lung cancer. The interactions of miR-556-3p with circ-ABCB10 and AK4 were testified by luciferase reporter and RIP assays.

RESULTS

Circ-ABCB10 was markedly upregulated and featured with loop structure in lung cancer. Circ-ABCB10 depletion suppresses lung cancer progression and sensitizes lung cancer cells to cisplatin. Molecular mechanism assays manifested that circ-ABCB10 bound with miR-556-3p and negatively modulated miR-556-3p expression. Additionally, AK4 was testified to be the downstream target of miR-556-3p. More importantly, rescue assays clarified that upregulation of AK4 could reverse the cisplatin-sensitizing and tumor-suppressing effect of circ-ABCB10 knockdown on lung cancer cells.

CONCLUSIONS

Circ-ABCB10 knockdown enhances sensitivity of lung cancer cells to cisplatin by targeting miR-556-3p/AK4 axis.

CLPTM1L/CRR9 ectodomain interaction with GRP78 at the cell surface signals for survival and chemoresistance upon ER stress in pancreatic adenocarcinoma cells

Altered regulation of endoplasmic reticulum (ER) homeostasis has been implicated in many cancers and has recently become a therapeutic and chemosensitization target of interest. We have identified Cleft Lip and Palate Transmembrane 1-Like (CLPTM1L)/Cisplatin Resistance Related Protein 9 (CRR9) as an ER stress related mediator of cytoprotection in pancreatic cancer. We recently demonstrated that CLPTM1L is highly expressed in pancreatic ductal adenocarcinoma and associated with poor outcome. Furthermore, we have discovered that CLPTM1L interacts with phosphoinositol-3-kinase-alpha at the tumor cell surface and causes up-regulation of Bcl-xL and pAkt mediated survival signaling. Here, we demonstrate surface relocalization and survival signaling by CLPTM1L triggered by endoplasmic reticular (ER) stress. We demonstrate the interaction of CLPTM1L with the central ER stress survival mediator, Glucose Regulated Protein 78 (GRP78)/Binding Immunoglobulin Protein (BiP) and PI3K-alpha /p110α. This interaction and surface relocalization of CLPTM1L and GRP78 is induced by ER stress, including that caused by treatment with gemcitabine. We demonstrate that the extracellular loop of CLPTM1L is required for gemcitabine resistance and interaction with GRP78. This interaction and the chemoresistance effect conferred by this pathway is targetable with our recently developed inhibitory CLPTM1L antibodies, which may represent novel modalities of chemosensitization and treatment of pancreatic adenocarcinoma. Anchorage independent growth, GRP78-mediated chemoresistance, and Akt phosphorylation were abrogated by inhibition of CLPTM1L. These findings demonstrate a novel and potentially targetable mechanism of cytoprotection and chemoresistance in pancreatic tumors.

Tunicamycin enhances the suppressive effects of cisplatin on lung cancer growth through PTX3 glycosylation via AKT/NF-κB signaling pathway

Long pentraxin-3 (PTX3) is an inflammatory molecule related to cancer proliferation, invasion, and metastasis. Many studies have highlighted the significance of glycosylated molecules in immune modulation, inflammation and cancer progression. Moreover, aberrant glycosylation of cancer cells is linked to chemoresistance. This study aimed to develop effective therapeutic strategies for deglycosylation of PTX3 (dePTX3) in order to enhance chemosensitivity to cisplatin (Cis) in lung cancer treatment. The A549 and SPCA1 cells were used to determine the role of PTX3 glycosylation in lung cancer growth. Our results revealed that PTX3 was higher in both human lung cancer tissues and serum in comparison with control. Furthermore, we found that deglycosylated PTX3 (dePTX3) by tunicamycin (TM), which is N-glycan precursor biosynthesis blocker, and PNGase F significantly reduced the survival and migration of lung cancer cells. To further confirm this, we also generated glycosylation-site mutant of PTX3 (mPTX3) to characterize the loss of glyco-function. dePTX3 and TM enhanced the suppressive effects of Cis on lung cancer cell growth, migration and invasion compared to individual treatment. Treatment with a combination of TM and Cis significantly inactivated AKT/NF-κB signaling pathway and induced apoptosis. In conclusion, these findings suggest that PTX3 is an important mediator of lung cancer progression, and dePTX3 by TM enhances the anticancer effects of Cis. The deglycosylation in chemotherapy may represent a potential novel therapeutic strategy against lung cancer.

GIV/Girdin promotes cell survival during endoplasmic reticulum stress

Endoplasmic reticulum (ER) stress is a form of cellular stress that is experienced by cells both under normal physiological conditions such as in professional secretory cells and disease states such as cancer, diabetes, and neurodegeneration. Upon facing ER stress, cells activate a conserved signaling pathway called the unfolded protein response (UPR) to restore normal function by halting general protein translation, upregulating expression of chaperones, and promoting ER-associated degradation. However, if the stress is overwhelming and cells are not able to recover within a reasonable time frame, the UPR ultimately commits cells to programmed cell death. How cells make this life-or-death decision remains an exciting yet poorly understood phenomenon. Here, we show that Gα-interacting vesicle-associated protein (GIV) aka Girdin plays an important role in promoting cell survival during ER stress. Cells lacking GIV are impaired in activating the pro-survival Akt pathway upon induction of ER stress. These cells also show enhanced levels of the pro-apoptotic transcription factor, CCAAT/enhancer binding protein homologous protein (CHOP) as compared to control cells. Due to decreased pro-survival signals and a concomitant increase in pro-apoptotic signals, GIV-depleted cells show a significant reduction in cell survival upon prolonged ER stress which can be rescued by re-expression of GIV or by directly activating Akt in these cells. Together, this study shows a novel, cytoprotective role for GIV in ER-stressed cells and furthers our understanding of the mechanisms that contribute to cell survival during ER stress.

Overexpression of endoplasmic reticulum stress-related proteins, XBP1s and GRP78, predicts poor prognosis in pulmonary adenocarcinoma

OBJECTIVES

Endoplasmic reticulum (ER) stress is associated with tumor development and progression via pro-tumorigenic and anti-tumorigenic effects. However, the clinicopathological implications of the ER stress pathway in non-small cell lung cancer remain unclear. Therefore, we sought to address these issues in this study.

MATERIALS AND METHODS

Expression of two ER stress-related proteins, GRP78 and XBP1 spliced-form (XBP1s), was evaluated in pulmonary adenocarcinoma (pADC; n = 369) and squamous cell carcinoma (pSqCC; n = 246) using immunohistochemistry.

RESULTS

Expression levels of GRP78 and XBP1s were significantly higher in pADCs and pSqCCs, respectively (both, P < 0.0001). In the pADC group, XBP1s expression was higher in patients with ALK translocation than in those with wild-type ALK, wild-type EGFR, or EGFR mutation (P < 0.005). No significant difference in GRP78 expression according to ALK or EGFR status was noted. pADC harboring high GRP78 expression exhibited an increased XBP1s expression (P = 0.0067). Higher XBP1s expression was associated with shorter disease-free survival (DFS) in patients with pADC (P = 0.026) and in those with ALK translocation (P = 0.001). Higher GRP78 expression was associated with shorter DFS in patients with pADC (P = 0.029) and those with EGFR mutation (P = 0.005). Multivariate survival analysis revealed that high XBP1s expression was an independent predictor of poor DFS in pADC (P = 0.004, hazard ratio [HR] = 3.115), and that high GRP78 expression was an independent predictor of poor DFS in EGFR-mutated pADC (P = 0.007, HR = 2.168). Taken together, high expression of XBP1s or GRP78 was an independent poor prognostic factor in pADC (P = 0.002, HR = 2.403).

CONCLUSION

GRP78 and XBP1s are expressed variably in pADC, but their overexpression is associated with poor patient prognosis. The ER stress pathway may be a prognostic biomarker and potential therapeutic target for pADC.

E3 ubiquitin ligase Hakai regulates cell growth and invasion, and increases the chemosensitivity to cisplatin in non‑small‑cell lung cancer cells

Hakai was originally identified as an E3 ubiquitin ligase of the E‑cadherin complex implicated in cell adhesion and invasion. Recently, emerging evidence has strongly suggested that Hakai serves a pivotal role in the tumorigenesis of certain tumors. However, the role of Hakai in non‑small‑cell lung cancer (NSCLC) and its underlying molecular mechanism have not been clarified. In the present study, it was observed that Hakai was highly expressed in NSCLC cell lines compared with human normal bronchial epithelial cells, and transfection with Hakai small interfering RNA significantly inhibited the growth of A549 and NCI‑H460 NSCLC cells. In addition, the inhibition of Hakai suppressed NSCLC cell migration and invasion through upregulation of E‑cadherin and downregulation of N‑cadherin. Notably, it was also revealed that knockdown of Hakai led to a decrease in the expression of phosphorylated AKT (Ser473), and a significant enhancement of chemosensitivity to cisplatin was observed following Hakai suppression. In conclusion, the present study demonstrated for the first time that knockdown of Hakai inhibited the proliferation, migration and invasion of NSCLC cells, and sensitized NSCLC cells to cisplatin. Thus, Hakai may serve as a potential therapeutic target for the treatment of NSCLC.

HSPA5 negatively regulates lysosomal activity through ubiquitination of MUL1 in head and neck cancer

HSPA5/GRP78/BiP plays an important role in cell survival or tumor progression. For these reasons, HSPA5 is an emerging therapeutic target in cancer development. Here we report that HSPA5 contributes to head and neck cancer (HNC) survival via maintenance of lysosomal activity; however, a nonthermal plasma (NTP, considered as a next-generation cancer therapy)-treated solution (NTS) inhibits HNC progression through HSPA5-dependent alteration of lysosomal activity. HSPA5 prevents NTS-induced lysosome inhibition through lysosomal-related proteins or regulation of gene expression. However, NTS-induced MUL1/MULAN/GIDE/MAPL (mitochondrial ubiquitin ligase activator of NFKB 1) leads to downregulation of HSPA5 via K48-linked ubiquitination at the lysine 446 (K446) residue. MUL1 knockdown hinders NTS-induced lysosome inhibition or cytotoxicity through the reduction of HSPA5 ubiquitination in HNC cells. While MUL1 was suppressed, HSPA5 was overexpressed in tissues of HNC patients. NTS strongly inhibited HNC progression via alterations of expression of MUL1 and HSPA5, in vivo in a xenograft model. However, NTS did not induce inhibition of tumor progression or HSPA5 reduction in MUL1 knockout (KO) HNC cells which were generated by CRISPR/Cas9 system. The data provide compelling evidence to support the idea that the regulation of the MUL1-HSPA5 axis can be a novel strategy for the treatment of HNC.

S100A16, a promising candidate as a prognostic marker for platinum-based adjuvant chemotherapy in resected lung adenocarcinoma

Purpose

Although cisplatin-based adjuvant chemotherapy improves the survival of patients with resected non-small-cell lung cancer, not all patients show a survival benefit, and some patients experience severe toxicity. Therefore, identifying biomarkers is important for selecting subgroups of patients who may show improved survival with platinum-based adjuvant chemotherapy. S100A16 is thought to play key roles during different steps of tumor progression. The aim of this study was to evaluate the use of S100A16 expression as a prognostic marker in patients with completely resected lung adenocarcinoma receiving platinum-based adjuvant chemotherapy.

Methods

S100A16 expression was immunohistochemically studied in 65 consecutive lung adenocarcinoma patients who underwent complete resection and received platinum-based adjuvant chemotherapy. Kaplan–Meier survival analysis and Cox proportional hazards models were used to estimate the effect of S100A16 expression on disease-free survival (DFS) and overall survival (OS).

Results

S100A16 expression was detected in 26 of the 65 (40.0%) lung adenocarcinoma patients. Although S100A16 expression was not correlated with DFS (P=0.062), it was significantly correlated with OS (P=0.009). In addition, multivariable analysis revealed that S100A16 expression independently predicted a poorer survival (HR =4.79; 95% CI =1.87–12.23; P=0.001).

Conclusion

The present study revealed that S100A16 is a promising candidate as a prognostic marker for platinum-based adjuvant chemotherapy in resected lung adenocarcinoma. A further large-scale study is needed to confirm the present results.

Upregulation of miR-146a increases cisplatin sensitivity of the non-small cell lung cancer A549 cell line by targeting JNK-2

The aim of the present study was to investigate the effects of microRNA (miR-)146a on the cisplatin sensitivity of the non-small cell lung cancer (NSCLC) A549 cell line and study the underlying molecular mechanism. The differences in expression of miRNAs between A549 and A549/cisplatin (A549/DDP) cells were determined, and miR-146a was selected to study its effect on cisplatin sensitivity of A549/DDP cells. miR-146a mimic and inhibitor transient transfection systems were constructed using vectors, and A549/DDP cells were infected with miR-146a mimic and inhibitor to investigate growth, apoptosis and migration. The directed target of miR-146a was determined and the underlying molecular mechanism was validated in the present study. The results of the present study demonstrated that miR-146a was downregulated in NSCLC A549/DDP cells, compared with A549 cells. The overexpression of miR-146a induced apoptosis and inhibited the growth and invasion of A549/DDP cells, which resulted in increased cisplatin sensitivity in NSCLC cells. The JNK2 gene was determined as the direct target of miR-146a, and may be activated by the overexpression of miR-146a. Additionally, JNK2 activated the expression of p53 and inhibited B cell lymphoma 2. The upregulation of miR-146a increased cisplatin sensitivity of the A549 cell line by targeting JNK2, which may provide a novel method for treating NSCLC cisplatin resistance.

Hypoxic Preconditioning Promotes the Bioactivities of Mesenchymal Stem Cells via the HIF-1α-GRP78-Akt Axis

Mesenchymal stem cells (MSC) are ideal materials for stem cell-based therapy. As MSCs reside in hypoxic microenvironments (low oxygen tension of 1% to 7%), several studies have focused on the beneficial effects of hypoxic preconditioning on MSC survival; however, the mechanisms underlying such effects remain unclear. This study aimed to uncover the potential mechanism involving 78-kDa glucose-regulated protein (GRP78) to explain the enhanced MSC bioactivity and survival in hindlimb ischemia. Under hypoxia (2% O₂), the expression of GRP78 was significantly increased via hypoxia-inducible factor (HIF)-1α. Hypoxia-induced GRP78 promoted the proliferation and migration potential of MSCs through the HIF-1α-GRP78-Akt signal axis. In a murine hind-limb ischemia model, hypoxic preconditioning enhanced the survival and proliferation of transplanted MSCs through suppression of the cell death signal pathway and augmentation of angiogenic cytokine secretion. These effects were regulated by GRP78. Our findings indicate that hypoxic preconditioning promotes survival, proliferation, and angiogenic cytokine secretion of MSCs via the HIF-1α-GRP78-Akt signal pathway, suggesting that hypoxia-preconditioned MSCs might provide a therapeutic strategy for MSC-based therapies and that GRP78 represents a potential target for the development of functional MSCs.

Radicol, a Novel Trinorguaiane-Type Sesquiterpene, Induces Temozolomide-Resistant Glioma Cell Apoptosis via ER Stress and Akt/mTOR Pathway Blockade

Glioblastoma multiforme (GBM) is the most frequent, lethal and aggressive tumour of the central nervous system (CNS) in adults. Multidrug resistance (MDR) results in undesirable prognosis during GBM chemotherapy. In this study, we determined that Radicol (RAD), a novel trinorguaiane-type sesquiterpene originally isolated from the root of Dictamnus radicis Cortex, exhibited potently cytotoxic effect on temozolomide (TMZ)-resistant GBM cell lines in a dose-dependent manner. Radicol-induced apoptosis was confirmed with Hoechst 33342/propidium iodide and terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end-labelling (TUNEL) staining. Studies investigating the mechanism revealed that RAD triggered an attenuation of protein disulphide isomerase (PDI) and induced the unmitigated unfolded protein response (UPR) and lethal endoplasmic reticulum (ER) stress. Simultaneously, we further demonstrated that RAD suppressed the activation of Akt/mTOR/p70S6K phosphorylation by up-regulating the induction of glycogen synthase kinase-3β (GSK-3β). These results established a link between RAD-induced ER stress and inhibition of the Akt/mTOR/p70S6K pathway, and the attenuation of PDI and activation of GSK-3β might be the synergistic target of antineoplastic effects during RAD-induced apoptosis. These findings suggested that RAD, possessing multiple cytotoxicity targets, low molecular weight and high lipid solubility, could be a promising agent for the treatment of malignant gliomas. Copyright © 2017 John Wiley & Sons, Ltd.

A novel HDAC6 inhibitor Tubastatin A: Controls HDAC6-p97/VCP-mediated ubiquitination-autophagy turnover and reverses Temozolomide-induced ER stress-tolerance in GBM cells

Temozolomide (TMZ) is the cornerstone of therapy for glioblastoma multiforme (GBM). However, its efficacy is limited due to the development of multidrug resistance (MDR). In this study, we first identified the occurrence of ER stress-tolerance (ERST) in glioma cells and confirmed that ERST was positively correlated with TMZ resistance. We further showed that the seesaw-effect of HDAC6-p97/VCP (increased HDAC6 and decreased p97/VCP) in glioma cells was crucial to ERST-associated TMZ resistance. Moreover, the combination treatment of Tubastatin A (TUB, a selective inhibitor of HDAC6) and TMZ synergistically overcame ERST, reduced cell viability and induced apoptosis in TMZ-resistant glioma cells. TUB and TMZ triggered pro-apoptotic signals of the unfolded protein response (UPR) and ER stress and reversed the ratio between HDAC6 and p97/VCP, which potentially attenuated the activation of heat shock proteins and mediated the reversal of ERST. The combination treatment also triggered the dissociation of Dynein-HDAC6 and attenuation of the Dynein-Dynactin motor complex. In addition, this treatment induced HDAC6-p97/VCP-mediated ubiquitination-autophagy turnover, which was involved in the degradation and clearance of ubiquitinated misfolded proteins. This effect could be partially reversed by HDAC6 KO and/or p97/VCP overexpression. Therefore, we proposed that glioma cells optimized the clearance of ubiquitinated misfolded proteins via the reinforcement of HDAC6-facilitated autophagy and attenuation of the p97/VCP-mediated ubiquitin-proteasome system (UPS). In conclusion, our findings showed that the balance of HDAC6-p97/VCP was crucial to ERST-associated TMZ resistance and that HDAC6 inhibition might be a synergistic target and strategy along with TMZ for the improvement of clinical glioma treatment.

Role of endoplasmic reticulum stress on cisplatin resistance in ovarian carcinoma

Endoplasmic reticulum (ER) is an essential site of cellular homeostasis regulation. ER stress (ERS) may induce autophagy in tumor cells that escape from apoptosis. The present study examined the effects and mechanism of ERS on cisplatin (DDP) sensitivity in ovarian carcinoma. SKOV3 tumor cells treated with Saquinavir were subjected to western blot and reverse transcription-quantitative polymerase chain reaction analysis to determine protein and messenger RNA (mRNA) expression levels of mechanistic target of rapamycin (mTOR) and Beclin 1. MTT assay was used to analyze the influence of Saquinavir on DDP resistance in SKOV3 cells. Saquinavir induced glucose-regulated protein 78 expression, which is a marker of ERS. Following treatment with various doses of Saquinavir, the sensitivity of ovarian cancer cells to DDP decreased significantly. Protein and mRNA expression levels of mTOR and Beclin 1 in SKOV3 cells were increased when the cells were exposed to Saquinavir or DDP for 24 h. Moreover, mTOR and Beclin 1 expression levels were highest in the Saquinavir + DDP group (0.684±0.072 and 0.6467±0.0468, respectively). SKOV3 tumor cells were also exposed to the autophagy inhibitor, 3-methyladenine (3-MA), and different concentrations of Saquinavir. Analysis of half maximal inhibitory concentration (IC₅₀) values of DDP after this treatment demonstrated that IC₅₀ values were significantly decreased compared with Saquinavir alone (P<0.001), suggesting that the sensitivity to DDP was improved in ovarian cancer cells after 3-MA exposure. These findings demonstrated that Saquinavir is able to induce ERS in SKOV3 cells effectively, and ER-induced stress may decrease the sensitivity of DDP in SKOV3 cells. Furthermore, ERS may regulate cell autophagy through the mTOR and Beclin 1 pathways, leading to a reduction in the sensitivity of DDP in SKOV3 cells. ERS in tumor cells and autophagy may be a potential target to improve the therapeutic effect of chemotherapy and reduce drug resistance in tumors.

Heat Shock Proteins and Cancer

Heat shock proteins (HSPs) constitute a large family of proteins involved in protein folding and maturation whose expression is induced by heat shock or other stressors. The major groups are classified based on their molecular weights and include HSP27, HSP40, HSP60, HSP70, HSP90, and large HSPs. HSPs play a significant role in cellular proliferation, differentiation, and carcinogenesis. In this article we comprehensively review the roles of major HSPs in cancer biology and pharmacology. HSPs are thought to play significant roles in the molecular mechanisms leading to cancer development and metastasis. HSPs may also have potential clinical uses as biomarkers for cancer diagnosis, for assessing disease progression, or as therapeutic targets for cancer therapy.

Endoplasmic reticulum stress induces 5-fluorouracil resistance in human colon cancer cells

Colon cancer can be treated with 5-fluorouracil (5-FU), but 5-FU resistance frequently occurs. We determined whether 5-FU resistance arises as a result of endoplasmic reticulum (ER) stress. 5-FU-resistant SNUC5 colon cancer cells (SNUC5/FUR cells) expressed higher levels of ER stress-related proteins than drug-sensitive SNUC5 cells. SNUC5/FUR cells also exhibited more intense ER staining and higher level of mitochondrial Ca(2+) overload. SNUC5/FUR cells transfected with siRNA against GRP78, ATF6, ERK, or AKT were more sensitive to 5-FU than siControl RNA-transfected cells. These results suggested that 5-FU resistance was associated with ER stress in colon cancer.

Tamoxifen-induced cytotoxicity in breast cancer cells is mediated by glucose-regulated protein 78 (GRP78) via AKT (Thr308) regulation

Glucose regulated protein 78 (GRP78) has recently been suggested to be associated with drug resistance in breast cancer patients. However, the precise role of GRP78 in drug resistance and the involved signaling pathways are not clearly understood. In the present study, we show that among a panel of drugs, namely Paclitaxel (TAX), Doxorubicin (DOX), 5-fluorouracil (5-FU), UCN-01 and Tamoxifen (TAM) used, TAM alone up-regulated the expression of GRP78 significantly and induced apoptosis in MCF-7 and MDA-MB-231 cells. Interestingly, inhibition of GRP78 by a specific pharmacological inhibitor, VER-155008 augmented TAM-induced apoptosis, and overexpression of GRP78 rendered the cells resistant to TAM-induced cell death suggesting a role for GRP78 in TAM-induced cytotoxicity. Mechanistically, the expression of phosphorylated AKT as determined by Western blot analyses revealed that TAM selectively upregulated phosphorylation of AKT at Thr308 but not at Ser473, and siRNA silencing of GRP78 resulted in inhibition of AKT phosphorylation at Thr308 but not at Ser473. Further, a GRP78 inhibitor, VER155008 inhibited TAM-induced phosphorylation of GSK3β, a downstream substrate of AKT. These results, thus suggests a role for GRP78 in TAM-induced AKT activation. Additionally, co-localization studies by immunofluorescence, and immunoprecipitation experiments demonstrated a complex formation of AKT and GRP78. Furthermore, in glucose-free medium, the cells were sensitized to TAM-induced cell death that was associated with reduced AKT phosphorylation at Thr308, thus strengthening the association of AKT regulation with drug response. Collectively, our findings identify a role of GRP78 in AKT regulation in response to TAM in breast cancer cells.

βIII-Tubulin alters glucose metabolism and stress response signaling to promote cell survival and proliferation in glucose-starved non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) survival rates are dismal and high βIII-tubulin expression is associated with chemotherapy drug resistance and tumor aggressiveness in this disease. Mounting evidence supports a role for βIII-tubulin in promoting cell survival in the harsh tumor microenvironment, which is characterized by poor nutrient supply. This study aimed to investigate the role of βIII-tubulin in glucose stress response signaling and the survival and proliferation of NSCLC cells. This study revealed that βIII-tubulin regulates cellular metabolism and glucose stress response signaling in NSCLC cells to promote cell survival and proliferation in glucose starvation. βIII-Tubulin decreases the reliance of cells on glycolytic metabolism, priming them to cope with variable nutrient supply present within the tumor microenvironment. βIII-Tubulin protects cells from endoplasmic reticulum (ER) stress and reduces both basal and glucose starvation-induced autophagy to maintain cell survival and proliferation. βIII-Tubulin enables rapid Akt activation in response to glucose starvation and co-immunoprecipitates with the master regulator of the ER stress response GRP78. Furthermore, suppression of βIII-tubulin delays the association of GRP78 with Akt in response to glucose starvation with the potential to influence Akt activation and ER homeostasis under these conditions. Together these results identify that βIII-tubulin regulates glucose metabolism and alters glucose starvation stress signaling to promote cell proliferation and survival in NSCLC cells. This elucidates a hitherto unknown role for this microtubule protein and provides insight into correlations between high βIII-tubulin expression and poor patient outcome in this disease.

Upregulated ATF6 contributes to chronic intermittent hypoxia-afforded protection against myocardial ischemia/reperfusion injury

In the present study, we investigated the role of activating transcription factor 6 (ATF6) in the mechanism by which chronic intermittent hypoxia (CIH) increases tolerance to myocardial ischemia/reperfusion (I/R). Experiments were conducted using a rat model of I/R injury in vivo and isolated Langendorff-perfused rat hearts ex vivo. The role of Akt in this process was also investigated in vitro using rat myoblast H9c2 cells. Cell viability was measured using a cell counting kit-8 assay. Lactate dehydrogenase (LDH) and creatine kinase cardiac isoenzyme activity were also measured as markers of cellular damage. ATF6, Akt and phosphorylated (p)-Akt expression was analyzed by western blot analysis. RNA interference (RNAi) was used to suppress ATF6 expression. We noted that ATF6 expression in the ventricular myocardium was significantly increased in rats exposed to CIH. Furthermore, we noted that CIH preserved cardiac function after I/R in vivo and improved post-ischemic recovery of myocardial performance in isolated rat hearts. ATF6 and p-Akt expression was upregulated in cultured H9c2 cells exposed to chronic mild hypoxia compared with those cultured under normoxic conditions. Chronic mild hypoxia attenuated subsequent simulated I/R injury in H9c2 cells (48 h), as evidenced by increased cell viability and decreased LDH activity. By contrast, decreased cell viability and increased LDH activity were observed in siRNA-ATF6-transfected H9c2 cells, with a concomitant reduction in p-Akt levels. These results indicated that ATF6 upregulation is involved in the mechanism by which CIH attenuates myocardial I/R injury, possibly through upregulation of p-Akt, which is a key regulator of cardiomyocyte survival.

ER stress and autophagy are involved in the apoptosis induced by cisplatin in human lung cancer cells

Cisplatin [cis-diamminedichloroplatinum II (CDDP)] is one of the most classical and effective chemotherapeutic drugs for the treatment of cancers including lung cancer. However, the presence of cisplatin resistance in cancer lowers its curative effect and limits its usage in the clinic. The aim of the present study was to investigate the underlying mechanisms of cisplatin resistance in lung cancer involving endoplasmic reticulum (ER) stress and autophagy. In the present study, we detected the effect of cisplatin on cell viability, ER stress and autophagy in lung cancer cell lines A549 and H460. We also tested the effects of ER stress and autophagy on apoptosis induced by cisplatin. The results showed that cisplatin induced apoptosis, ER stress and autophagy in lung cancer cell lines. In addition, the inhibition of ER stress by 4-phenylbutyric acid (4-PBA) or tauroursodeoxycholic acid sodium (TUDC) enhanced cisplatin-induced apoptosis in the human lung cancer cells. Meanwhile, combination treatment with the autophagic inhibitor 3-methyladenine (3-MA) or chloroquine (CQ) further increased the apoptosis induced by cisplatin in the human lung cancer cells. The present study provides a novel treatment strategy - cisplatin in combination with an autophagic inhibitor or an ER stress inhibitor leads to increased apoptosis in human lung cancer cells.

Expression of GRP78, Master Regulator of the Unfolded Protein Response, Increases Chemoresistance in Pancreatic Ductal Adenocarcinoma

The prognosis for patients with pancreatic ductal adenocarcinoma (PDAC) is dismal. Although gemcitabine (GEM) is the standard chemotherapeutic agent for adjuvant therapy of resectable PDAC, recurrent disease is observed in an alarming number of GEM-treated patients. Regardless of the adjuvant therapy, the vast majority of patients treated with chemotherapy after surgical resection show tumor recurrence. A better understanding of the molecular mechanisms that contribute to chemoresistance would aid the development of more effective treatment strategies. GRP78 is an endoplasmic reticulum (ER) chaperone protein that primarily resides in the lumen of the ER and is the master regulator of the unfolded protein response (UPR). Here, we report that expression of GRP78 is significantly higher in GEM-resistant PDAC compared to GEM-sensitive PDAC patient samples. We show that GRP78 induces chemoresistance in PDAC cells. Our results also show that knockdown of GRP78 reduces chemoresistance in PDAC. Finally, we found that IT-139, a ruthenium-based anticancer drug, can overcome GRP78-mediated chemoresistance. In vitro, IT-139 restores sensitivity to cytotoxic drugs in drug-resistant PDAC cells and induces twice as much cell death in combination treatment compared with GEM alone. In vivo, a single weekly IT-139 treatment in combination with GEM caused a 35% increase in median survival and a 25% increase in overall survival compared to GEM alone. Collectively, our data show that GRP78 expression promotes chemoresistance in PDAC and therapeutic strategies, blocking the activity of GRP78 increases the efficacy of currently available therapies. Mol Cancer Ther; 15(5); 1043-52. ©2016 AACR.

p22phox confers resistance to cisplatin, by blocking its entry into the nucleus

Cisplatin (CDDP) is a potent chemotherapeutic agent but resistance to the drug remains a major challenge in cancer treatment. To evaluate the efficacy of CDDP in oral squamous cell carcinoma (OSCC), we found that p22phox was highly expressed in CDDP-resistant OSCC specimens. Knockdown of p22phox sensitized OSCC cell lines to CDDP (P < 0.05). Stable overexpression of p22phox augmented CDDP resistance, as evidenced by the significantly higher IC₅₀ values. This cytoprotective effect was attributed to the abrogation of CDDP-induced apoptosis. Akt phosphorylation was increased in p22phox stable lines. However, blocking PI3K/Akt pathway only partially restored CDDP-induced apoptosis. In addition, the overexpressed p22phox in OSCC cells exhibited cytoplasmic localization with enhanced perinuclear expression, consistent with the localization pattern in OSCC specimens. Remarkably, CDDP entry into the nucleus was severely impaired in p22phox-overexpressing cells (P < 0.001), and cytoplasmically accumulated CDDP was co-localized with overexpressed p22phox. This was supported by decreased CDDP-DNA adduct formation and delayed chk1-p53 signaling activation. Together, overexpression of p22phox sequestered CDDP and caused defective CDDP entry into the nucleus, significantly attenuating CDDP-induced apoptosis. Such diminished apoptosis was further abolished by p22phox-activating PI3K/Akt pathway. Our work has suggested a novel biomarker and insight into the mechanism of CDDP resistance.

2,5-Dimethyl-celecoxib inhibits cell cycle progression and induces apoptosis in human leukemia cells

Cyclooxygenase-2 (COX-2) is an essential regulator of cancer promotion and progression. Extensive efforts to target this enzyme have been developed to reduce growth of cancer cells for chemopreventive and therapeutic reasons. In this context, cyclooxygenase-2 inhibitors present interesting antitumor effects. However, inhibition of COX-2 by anti-COX-2 compounds such as celecoxib was recently associated with detrimental cardiovascular side effects limiting their clinical use. As many anticancer effects of celecoxib are COX-2 independent, analogs such as 2,5-dimethyl-celecoxib (DMC), which lacks COX-2-inhibitory activity, represent a promising alternative strategy. In this study, we investigated the effect of this molecule on growth of hematologic cancer cell lines (U937, Jurkat, Hel, Raji, and K562). We found that this molecule is able to reduce the growth and induces apoptosis more efficiently than celecoxib in all the leukemic cell lines tested. Cell death was associated with downregulation of Mcl-1 protein expression. We also found that DMC induces endoplasmic reticulum stress, which is associated with a decreased of GRP78 protein expression and an alteration of cell cycle progression at the G1/S transition in U937 cells. Accordingly, typical downregulation of c-Myc and cyclin D1 and an upregulation of p27 were observed. Interestingly, for shorter time points, an alteration of mitotic progression, associated with the downregulation of survivin protein expression was observed. Altogether, our data provide new evidence about the mode of action of this compound on hematologic malignancies.

GRP78 is implicated in the modulation of tumor aerobic glycolysis by promoting autophagic degradation of IKKβ

Compared with normal differentiated cells, cancer cells take up much more glucose and metabolize it mainly via aerobic glycolysis. This metabolic phenotype is characterized with high expression of glucose transporters (Gluts) and pyruvate kinase M2 (PKM2). Glucose regulated protein 78 (GRP78) is a glucose-sensing protein and frequently up-regulated in cancer cells, however, whether it is directly implicated in glucose metabolism remains to be elucidated. Here we report that upon glucose deficiency, the induction of GRP78 resulted in enhanced HIF-1α transcription, accompanied by a transient increased expression of Glut-1. In addition, GRP78 was likely to facilitate the membrane translocation of Glut-1 via protein-protein interaction. Glucose starvation-stimulated GRP78 also impaired the expression of PKM2 but promoted the expression of mitochondrial pyruvate dehydrogenase A (PDHA) and B (PDHB), resulting in the metabolic shift from glycolysis to the TCA cycle. Interestingly, the inhibition of PKM2 by GRP78 was abrogated when glucose supply was restored, suggesting that GRP78 and PKM2 expressions are adaptable to the nutritional levels in the microenvironment. Further mechanistic study indicated that GRP78 overexpression activated the Class III PI3K-mediated autophagy pathway and induced autophagic degradation of IKKβ, which caused inactivation of NF-κB pathway and subsequently altered the expression of PKM2 and HIF-1α. Our study establishes GRP78 and PKM2 as the crucial molecular links between cancer cell glucose metabolism and tumor microenvironment alterations.

New mechanisms for old drugs: Insights into DNA-unrelated effects of platinum compounds and drug resistance determinants

Platinum drugs have been widely used for the treatment of several solid tumors. Although DNA has been recognized as the primary cellular target for these agents, there are unresolved issues concerning their effects and the molecular mechanisms underlying the antitumor efficacy. These cytotoxic agents interact with sub-cellular compartments other than the nucleus. Here, we review how such emerging phenomena contribute to the pharmacologic activity as well as to drug resistance phenotypes. DNA-unrelated effects of platinum drugs involve alterations at the plasma membrane and in endo-lysosomal compartments. A direct interaction with the mitochondria also appears to be implicated in drug-induced cell death. Moreover, the pioneering work of a few groups has shown that platinum drugs can act on the tumor microenvironment as well, and potentiate antitumor activity of the immune system. These poorly understood aspects of platinum drug activity sites may be harnessed to enhance their antitumor efficacy. A complete understanding of DNA-unrelated effects of platinum compounds might reveal new aspects of drug resistance allowing the implementation of the antitumor therapeutic efficacy of platinum compound-based regimens and minimization of their toxic side effects.

RNA silencing of integrin-linked kinase increases the sensitivity of the A549 lung cancer cell line to cisplatin and promotes its apoptosis

The expression of integrin-linked kinase (ILK) has been reported to be involved in the regulation of integrin-mediated processes, including cancer cell proliferation, migration and invasion. Previous studies have demonstrated that inhibition of ILK may be an underlying approach for treating cancer. However, whether the knock down of ILK affects growth and apoptosis of lung cancer cells remains to be elucidated. Importantly, whether downregulation of ILK increases the sensitivity of lung cancer cells to cisplatin and amplifies cell apoptosis also remains to be elucidated. In the present study, ILK downregulation was mediated by lentivirus-mediated RNA interference. The expression levels of associated genes were determined by reverse-transcription quantitative polymerase chain reaction and western blotting. Cell proliferation was evaluated using a modified 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and clone formation assay. The cell cycle and apoptosis were analyzed using flow cytometry. The current data revealed that lentivirus-mediated ILK gene silencing alone inhibited A549 cell proliferation and promotes cell cycle arrest, however, had no detectable effect on cell apoptosis. However, combined treatment with lentivirus-mediated ILK interference and cisplatin chemotherapy induced significantly more cell apoptosis than mono-chemotherapy or knockdown. The increased cell apoptosis and proliferation inhibition were attributed to abnormal downstream protein expression of ILK, including phospho-glycogen synthase kinase 3β, p-AKT, activator protein-1, β-catenin, cyclin D1 and matrix metalloproteinase-9. ILK inhibition may suppress the proliferation of A549 and increase A549 sensitivity to cisplatin. The combined treatment of ILK gene knockdown and chemotherapy has the potential to improve anticancer efficacy.

Endoplasmic reticulum stress in endometrial cancer

Endometrial cancer (EC) is a common gynecologic malignancy often diagnosed at early stage. In spite of a huge advance in our understanding of EC biology, therapeutic modalities do not have significantly changed over the past 40 years. A restricted number of genes have been reported to be mutated in EC, mediating cell proliferation and invasiveness. However, besides these alterations, few other groups and ourselves recently identified the activation of the unfolded protein response (UPR) and GRP78 increase following endoplasmic reticulum (ER) stress as mechanisms favoring growth and invasion of EC cells. Here, a concise update on currently available data in the field is presented, analyzing the crosstalk between the UPR and the main signaling pathways regulating EC cell proliferation and survival. It is evident that this is a rapidly expanding and promising issue. However, more data are very likely to yield a better understanding on the mechanisms through which EC cells can survive the low oxygen and glucose tumor microenvironment. In this perspective, the UPR and, particularly, GRP78 might constitute a novel target for the treatment of EC in combination with traditional adjuvant therapy.

Nitric oxide confers cisplatin resistance in human lung cancer cells through upregulation of aldo-keto reductase 1B10 and proteasome

In this study, we show that exposure of human lung cancer A549 cells to cisplatin (cis-diamminedichloroplatinum, CDDP) promotes production of nitric oxide (NO) through generation of reactive oxygen species (ROS) and resulting upregulation of inducible NO synthase (iNOS). The incubation of the cells with a NO donor, diethylenetriamine NONOate, not only reduced the CDDP-induced cell death and apoptotic alterations (induction of CCAAT-enhancer-binding protein homologous protein and caspase-3 activation), but also elevated proteolytic activity of 26S proteasome, suggesting that the activation of proteasome function contributes to the reduction of CDDP sensitivity by NO. Monitoring expression levels of six aldo-keto reductases (AKRs) (1A1, 1B1, 1B10, 1C1, 1C2, and 1C3) during the treatment with the NO donor and subsequent CDDP sensitivity test using the specific inhibitors also proposed that upregulation of AKR1B10 by NO is a key process for acquiring the CDDP resistance in A549 cells. Treatment with CDDP and NO increased amounts of nitrotyrosine protein adducts, indicative of peroxynitrite formation, and promoted the induction of AKR1B10, inferring a relationship between peroxynitrite formation and the enzyme upregulation in the cells. The treatment with CDDP or a ROS-related lipid aldehyde, 4-hydroxy-2-nonenal, facilitated the iNOS upregulation, which was restored by increasing the AKR1B10 expression. In contrast, the facilitation of NO production by CDDP treatment was hardly observed in AKR1B10-overexpressing A549 cells and established CDDP-resistant cancer cells (A549, LoVo, and PC3). Collectively, these results suggest the NO functions as a key regulator controlling AKR1B10 expression and 26S proteasome function leading to gain of the CDDP resistance.