A2B adenosine receptor agonist induces cell cycle arrest and apoptosis in breast cancer stem cells via ERK1/2 phosphorylation

The protective mechanism of Tao Hong Si Wu decoction against breast cancer through regulation of EGFR/ERK1/2 signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Tao Hong Si Wu Decoction (THSWD), a traditional Chinese herbal medicine, is widely utilized in clinical settings, either alone or in combination with other medications, for the treatment of breast cancer.

AIM OF THE STUDY

The specific targeting molecule(s) of THSWD and its associated molecular mechanisms remain unclear. This research aims to elucidate the underlying molecular mechanisms of THSWD in the treatment of breast cancer.

MATERIALS AND METHODS

The pharmacological properties of THSWD were investigated in breast cancer cells and tumor tissues using a range of methods including Acridine Orange/Ethidium Bromide (AO/EB) staining, Transwell assay, flow cytometry, immunofluorescence assay, and breast cancer mice models.

RESULTS

Our findings demonstrate that THSWD induces necrosis and/or apoptosis in breast cancer cells, while significantly inhibiting cell migration. Target proteins of THSWD in anticancer activity include EGFR, RAS, and others. THSWD treatment for breast cancer is associated with the EGFR/ERK1/2 signaling pathway.

CONCLUSION

Our findings offer initial insights into the primary mechanism of action of THSWD in breast cancer treatment, indicating its potential as a complementary therapy deserving further investigation.

Adenosine receptors in breast cancer

Adenosine receptors are important in the normal physiological function of cells and the pathogenesis of various cancer cells, including breast cancer cells. The activity of adenosine receptors in cancer cells is related to cell proliferation, angiogenesis, metastasis, immune system evasion, and interference with apoptosis. Considering the different roles of adenosine receptors in cancer cells, we intend to investigate the function of adenosine receptors and their biological pathways in breast cancer to improve understanding of therapeutically relevant signaling pathways.

Purinergic system in cancer stem cells

Accumulating evidence supports the idea that cancer stem cells (CSCs) are those with the capacity to initiate tumors, generate phenotypical diversity, sustain growth, confer drug resistance, and orchestrate the spread of tumor cells. It is still controversial whether CSCs originate from normal stem cells residing in the tissue or cancer cells from the tumor bulk that have dedifferentiated to acquire stem-like characteristics. Although CSCs have been pointed out as key drivers in cancer, knowledge regarding their physiology is still blurry; thus, research focusing on CSCs is essential to designing novel and more effective therapeutics. The purinergic system has emerged as an important autocrine-paracrine messenger system with a prominent role at multiple levels of the tumor microenvironment, where it regulates cellular aspects of the tumors themselves and the stromal and immune systems. Recent findings have shown that purinergic signaling also participates in regulating the CSC phenotype. Here, we discuss updated information regarding CSCs in the purinergic system and present evidence supporting the idea that elements of the purinergic system expressed by this subpopulation of the tumor represent attractive pharmacological targets for proposing innovative anti-cancer therapies.

A2B Adenosine Receptor in Idiopathic Pulmonary Fibrosis: Pursuing Proper Pit Stop to Interfere with Disease Progression

Purine nucleotides and nucleosides are involved in various human physiological and pathological mechanisms. The pathological deregulation of purinergic signaling contributes to various chronic respiratory diseases. Among the adenosine receptors, A2B has the lowest affinity such that it was long considered to have little pathophysiological significance. Many studies suggest that A2BAR plays protective roles during the early stage of acute inflammation. However, increased adenosine levels during chronic epithelial injury and inflammation might activate A2BAR, resulting in cellular effects relevant to the progression of pulmonary fibrosis.

Synergistic effects of BAY606583 on docetaxel in esophageal cancer through modulation of ERK1/2

Docetaxel (DTX) is a taxane chemotherapy agent used to treat many types of cancers, including esophageal squamous cell carcinoma. Adenosine is a purinergic signaling molecule that contributes to cancer cell proliferation via A2B adenosine receptor (A2BAR) activation. Extracellular signal-regulated protein kinase (ERK) plays a crucial role in cell proliferation in various types of cancers. Stimulation of A2BAR involves a regulated ERK signaling pathway, and might provide a fascinating approach for treatment, leading to decreased proliferation in certain tumors that express A2BAR. Recent studies demonstrated that DTX and A2BAR have anticancer effects. The current study was designed to investigate the synergistic effect of the A2BAR agonist (BAY606583) on DTX in inducing antiproliferation effects on esophageal squamous cells carcinoma (ESCCs). The cell viability was assessed using the MTT assay in KYSE-30 and Ym-1 cells. In addition, the synergistic effect of DTX on the A2BAR agonist was evaluated. Subsequently, apoptosis was assessed by Annexin-V and propidium iodide staining, and Bcl-2, Bax, and ERK1/2 protein-level expressions were evaluated by Western blot. Use of BAY606583 and cotreatment of DTX and BAY606583 significantly decreased cell proliferation in KYSE-30 and Ym-1 cell lines. The use of BAY606583 and cotreatment of DTX with the A2BAR agonist induced apoptosis in KYSE-30 and Ym-1 cells. Western blot analysis revealed that the use of the A2BAR agonist and cotreatment of DTX with the A2BAR agonist inhibited the expression of apoptotic regulatory proteins as well as the expression of ERK1/2 proteins. Our findings suggested that use of BAY606583 and cotreatment of BAY606583/DTX have an antiproliferative effect on ESCC cell lines through ERK signaling pathway inhibition. BAY606583 has a synergistic effect on DTX, which could be used as an adjuvant for esophageal cancer therapy.

The adenosine-A2a receptor regulates the radioresistance of gastric cancer via PI3K-AKT-mTOR pathway

BACKGROUND

Radiotherapy is a key strategy in gastric cancer (GC) treatment. However, radioresistance remains a serious concern. It is unclear whether the accumulation of adenosine A2a receptor (ADO-A2aR) is related to radioresistance in GC. In this study, the molecular role of ADO-A2aR in GC radioresistance was investigated.

METHODS

Colony formation assays were used to assess the role of ADO-A2aR on radioresistance. GC stem cell surface marker expression (including Nanog, OCT-4, SOX-2 and CD44) and PI3K/AKT/mTOR signaling pathway associated protein levels (including phosphorylated PI3K, phosphorylated AKT and phosphorylated mTOR) were determined via western blotting, flow cytometry and immunofluorescence. In addition, the role of ADO-A2aR on radioresistance was explored in vivo using murine xenograft models.

RESULTS

ADO-A2aR regulated GC cell stemness both in vitro and in vivo. This was shown to induce radioresistance in GC. ADO-A2aR was revealed to significantly induce cell cycle arrest and promote GC cell apoptosis. These activities were closely linked to activation of the PI3K/AKT/mTOR pathway.

CONCLUSION

This study identified that ADO enhances GC cell stemness via interaction with A2aR and subsequent activation of the PI3K/AKT/mTOR pathway. Ultimately, this resulted in radioresistance. A2aR is a potential target to improve GC radiosensitivity.

Current Adenosinergic Therapies: What Do Cancer Cells Stand to Gain and Lose?

A key objective in immuno-oncology is to reactivate the dormant immune system and increase tumour immunogenicity. Adenosine is an omnipresent purine that is formed in response to stress stimuli in order to restore physiological balance, mainly via anti-inflammatory, tissue-protective, and anti-nociceptive mechanisms. Adenosine overproduction occurs in all stages of tumorigenesis, from the initial inflammation/local tissue damage to the precancerous niche and the developed tumour, making the adenosinergic pathway an attractive but challenging therapeutic target. Many current efforts in immuno-oncology are focused on restoring immunosurveillance, largely by blocking adenosine-producing enzymes in the tumour microenvironment (TME) and adenosine receptors on immune cells either alone or combined with chemotherapy and/or immunotherapy. However, the effects of adenosinergic immunotherapy are not restricted to immune cells; other cells in the TME including cancer and stromal cells are also affected. Here we summarise recent advancements in the understanding of the tumour adenosinergic system and highlight the impact of current and prospective immunomodulatory therapies on other cell types within the TME, focusing on adenosine receptors in tumour cells. In addition, we evaluate the structure- and context-related limitations of targeting this pathway and highlight avenues that could possibly be exploited in future adenosinergic therapies.

Autocrine and paracrine purinergic signaling in the most lethal types of cancer

Cancer comprises a collection of diseases that occur in almost any tissue and it is characterized by an abnormal and uncontrolled cell growth that results in tumor formation and propagation to other tissues, causing tissue and organ malfunction and death. Despite the undeniable improvement in cancer diagnostics and therapy, there is an urgent need for new therapeutic and preventive strategies with improved efficacy and fewer side effects. In this context, purinergic signaling emerges as an interesting candidate as a cancer biomarker or therapeutic target. There is abundant evidence that tumor cells have significant changes in the expression of purinergic receptors, which comprise the G-protein coupled P2Y and AdoR families of receptors and the ligand-gated ion channel P2X receptors. Tumor cells also exhibit changes in the expression of nucleotidases and other enzymes involved in nucleotide metabolism, and the concentrations of extracellular nucleotides are significantly higher than those observed in normal cells. In this review, we will focus on the potential role of purinergic signaling in the ten most lethal cancers (lung, breast, colorectal, liver, stomach, prostate, cervical, esophagus, pancreas, and ovary), which together are responsible for more than 5 million annual deaths.

A three-dimensional microenvironment alters CD73 expression in cervical cancer

Stem-like cells (CSCs) have a tumour-initiating capacity and play critical role in tumour metastasis, relapse and resistance to therapy. The ectoenzyme CD73, encoded by the NT5E gene, which catalyses the hydrolysis of AMP into adenosine, has been associated to an immunosuppressive tumour microenvironment, tumour cell adhesion and migration. Therefore, we investigated the expression and activity of CD73 in sphere-forming cells from cervical cancer in comparison to monolayer cells in vitro. In addition, in silico analysis was performed to determine the expression of CD73 and other members of purinergic signalling in CSC-like population derived from different tumour types in comparison to monolayer cells. CD73 protein expression levels and functionality in SiHa cells were analysed by flow cytometry and enzymatic assay, respectively. In silico investigation was performed through the analysis of seven datasets from different tumour types using GEO database. In vitro analysis showed a decreased CD73 protein expression and enzymatic activity in cervical spheres, when compared to monolayers. In addition, when sphere-derived cells are re-plated as monolayer culture, the CD73 expression and activity are restored. Supporting the in vitro results, in silico analysis showed that three-dimensional spheres derived from cervical, thyroid and breast cancer presented decreased expression of CD73, when compared to their adherent counterparts. The decreased expression of CD73 in sphere-derived cells or CSC-enriched population reinforce its important role in cell adhesion, tumour spreading ability and metastasis, suggesting CD73 as potential target to be further investigated in cervical cancer.

Knockdown of TAZ decrease the cancer stem properties of ESCC cell line YM-1 by modulation of Nanog, OCT-4 and SOX2

Cancer stem cells are a rare population in tumors with high metastatic potential and resistance to treatment. Recent strategies in cancer treatment have focused on targeting important signaling pathways that have an important role in maintaining CSC populations. TAZ (transcriptional co-activator with PDZ-binding motif) is a key downstream of the Hippo pathway which plays a fundamental role in the survival of CSCs from different origins, however, no data on the role of TAZ in esophageal cancer are available. Our findings showed that esophageal CSCs enriched from the YM-1 cell line have stemness properties. We found that TAZ was strongly expressed in esophageal CSCs and knockdown of TAZ in esophageal CSCs results in reduced colony formation and cell migration. Moreover, this data indicated that TAZ knockdown reduces the expression of SOX-2, OCT-4, and Nanong in esophageal CSCs. Taken together, the results of the current study suggested that TAZ has a crucial role in the biology of esophageal CSCs.

The therapeutic potential of targeting CD73 and CD73-derived adenosine in melanoma

The hypoxic environment of melanoma results in CD73 upregulation on the surface of various tumor microenvironment (TME) cells including tumor cells, stromal cells and infiltrated immune cells. Consequently, CD73 through both enzymatic and none enzymatic functions affect melanoma progression. Overaccumulation of CD73-derived adenosine through interaction with its four G coupled receptors (A₁AR, A_2AAR, A_2BAR, and A₃AR) mediate tumor growth, immune suppression, angiogenesis, and metastasis. This paper aims to comprehensively review the therapeutic potential of CD73 ectonucleotidase targeting in melanoma. To reach this goal, firstly, we summarize the structure, function, regulation, and clinical outcome of CD73 ectonucleotidase. Then, we depict the metabolism and signaling of CD73-derived adenosine along with its progressive role in development of melanoma. Furthermore, the therapeutic potentials of CD73 -adenosine axis targeting is assessed in both preclinical and clinical studies. Targeting CD73-derived adenosine via small molecule inhibitor or monoclonal antibodies studies especially in combination with immune checkpoint blockers including PD-1 and CTLA-4 have shown desirable results for management of melanoma in preclinical studies and several clinical trials have recently been started to evaluate the therapeutic potential of CD73-derived adenosine targeting in solid tumors. Indeed, targeting of CD73-derived adenosine signaling could be considered as a new therapeutic target in melanoma.

Mechanism of inositol-requiring enzyme 1-alpha inhibition in endoplasmic reticulum stress and apoptosis in ovarian cancer cells

IRE1α endonuclease is a key regulator of endoplasmic reticulum (ER) stress that controls cell survival/apoptosis in cancers. Inhibition of IRE1α endonuclease leads to decreased splice XBP1 which decreases cell proliferation and increases cell death in cancer cells. Therefore, this study investigated the effects and mechanism of STF-083010 (an IRE1α inhibitor) on the cell growth/apoptosis of ovarian malignant cells via the XBP1-CHOP-Bim pathway following the induction of ER stress (ERS). ERS in OVCAR3 and SKOV3 cells was measured using Thioflavin T staining. The expression of ER stress response genes was evaluated by QRT-PCR. The levels of XBP1(s), PERK, phospho-PERK, p-PP2A, ATF4, BIP/GRP78, CHOP, and Bim proteins were evaluated using western blotting. Cell viability and apoptosis in STF-083010 and Tunicamycin (Tm) co-treated cells were assessed using BrdU, MTT, Annexin V-FITC/PI staining, and caspases-12 and -3 activity assays. The results showed increased XBP1, CHOP, and ATF-4 mRNA expression levels as well as high protein aggregation in STF-083010 and Tm co-treated cells. The IRE1α inhibitor down-regulated sXBP1 and BIP proteins, while XBP-1, p-PERK, ATF-4, CHOP, and Bim proteins were up-regulated. STF-083010 reduced cell proliferation and induced apoptosis through the activation of caspases-12 and -3 and Bax/Bcl-2 protein expression. In summary, the present data revealed the effects of STF-083010 in ER stress and apoptosis as well as signaling via XBP1/CHOP/Bim mediators. Thus, STF-083010 is proposed as a new target for the control of ERS in ovarian cancer cells.

Cockle Shell-Derived Aragonite CaCO3 Nanoparticles for Co-Delivery of Doxorubicin and Thymoquinone Eliminates Cancer Stem Cells

Cancer stem cells CSCs (tumour-initiating cells) are responsible for cancer metastasis and recurrence associated with resistance to conventional chemotherapy. This study generated MBA MD231 3D cancer stem cells enriched spheroids in serum-free conditions and evaluated the influence of combined doxorubicin/thymoquinone-loaded cockle-shell-derived aragonite calcium carbonate nanoparticles. Single loaded drugs and free drugs were also evaluated. WST assay, sphere forming assay, ALDH activity analysis, Surface marker of CD44 and CD24 expression, apoptosis with Annexin V-PI kit, cell cycle analysis, morphological changes using a phase contrast light microscope, scanning electron microscopy, invasion assay and migration assay were carried out; The combination therapy showed enhanced apoptosis, reduction in ALDH activity and expression of CD44 and CD24 surface maker, reduction in cellular migration and invasion, inhibition of 3D sphere formation when compared to the free drugs and the single drug-loaded nanoparticle. Scanning electron microscopy showed poor spheroid formation, cell membrane blebbing, presence of cell shrinkage, distortion in the spheroid architecture; and the results from this study showed that combined drug-loaded cockle-shell-derived aragonite calcium carbonate nanoparticles can efficiently destroy the breast CSCs compared to single drug-loaded nanoparticle and a simple mixture of doxorubicin and thymoquinone.

Inhibition of the Adenosinergic Pathway in Cancer Rejuvenates Innate and Adaptive Immunity

The adenosine pathway plays a key role in modulating immune responses in physiological and pathological conditions. Physiologically, anti-inflammatory effects of adenosine balance pro-inflammatory adenosine 5'-triphosphate (ATP), protecting tissues from damage caused by activated immune cells. Pathologically, increased adenosine monophosphatase (AMPase) activity in tumors leads to increased adenosine production, generating a deeply immunosuppressed microenvironment and promoting cancer progression. Adenosine emerges as a promising target for cancer therapy. It mediates protumor activities by inducing tumor cell proliferation, angiogenesis, chemoresistance, and migration/invasion by tumor cells. It also inhibits the functions of immune cells, promoting the formation of a tumor-permissive immune microenvironment and favoriting tumor escape from the host immune system. Pharmacologic inhibitors, siRNA or antibodies specific for the components of the adenosine pathway, or antagonists of adenosine receptors have shown efficacy in pre-clinical studies in various in vitro and in vivo tumor models and are entering the clinical arena. Inhibition of the adenosine pathway alone or in combination with classic immunotherapies offers a potentially effective therapeutic strategy in cancer.

MicroRNA‑125a‑5p controls the proliferation, apoptosis, migration and PTEN/MEK1/2/ERK1/2 signaling pathway in MCF‑7 breast cancer cells

MicroRNA (miR)-125a-5p has shown the potential for suppressing tumorigenesis and development; however, the effects of miR-125a-5p on breast cancer cells remains unknown. The aim of this study was to evaluate the effects and underlying mechanisms of miR-125a-5p in MCF-7 breast cancer cells. MCF-7 cells were transfected with miR-125a-5p mimic or miR-125a-5p small interfering RNA to produce miR-125a-5p overexpressing/knockdown cells. Cell proliferation was assessed by an MTT assay, and cell migration ability was determined by an in vitro scratch assay. Hoechst 33258 staining and flow cytometry were performed to assess the effects of miR-125a-5p on MCF-7 apoptosis. Western blotting and reverse transcription-quantitative polymerase chain reaction were used for measuring phosphatase and tensin homolog (PTEN), phosphorylated (p)-mitogen-activated protein kinase kinase (MEK1/2)/MEK1/2, p-ERK1/2/ERK1/2, B-cell lymphoma-2 (Bcl-2), cleaved caspase-3, and miR-125a-5p expression. miR-125a-5p overexpression inhibited the proliferation and migration, but promoted the apoptosis of MCF-7 cells. These effects were associated with increases in PTEN and cleaved caspase-3 expression, and decreases in p-MEK1/2/MEK1/2, p-ERK1/2/ERK1/2, and Bcl-2. Silencing of miR-125a-5p exhibited opposing effects on MCF-7 cells. These observations suggested that miR-125a-5p participates in the regulation of multiple functions of MCF-7 cells by promoting the expression of PTEN tumor suppressor genes, activating MEK1/2/ERK1/2 signaling, and regulating caspase-3/Bcl-2 signaling. Thus, it may be a suitable target for breast cancer gene therapy.

Purine-Metabolising Enzymes and Apoptosis in Cancer

The enzymes of both de novo and salvage pathways for purine nucleotide synthesis are regulated to meet the demand of nucleic acid precursors during proliferation. Among them, the salvage pathway enzymes seem to play the key role in replenishing the purine pool in dividing and tumour cells that require a greater amount of nucleotides. An imbalance in the purine pools is fundamental not only for preventing cell proliferation, but also, in many cases, to promote apoptosis. It is known that tumour cells harbour several mutations that might lead to defective apoptosis-inducing pathways, and this is probably at the basis of the initial expansion of the population of neoplastic cells. Therefore, knowledge of the molecular mechanisms that lead to apoptosis of tumoural cells is key to predicting the possible success of a drug treatment and planning more effective and focused therapies. In this review, we describe how the modulation of enzymes involved in purine metabolism in tumour cells may affect the apoptotic programme. The enzymes discussed are: ectosolic and cytosolic 5'-nucleotidases, purine nucleoside phosphorylase, adenosine deaminase, hypoxanthine-guanine phosphoribosyltransferase, and inosine-5'-monophosphate dehydrogenase, as well as recently described enzymes particularly expressed in tumour cells, such as deoxynucleoside triphosphate triphosphohydrolase and 7,8-dihydro-8-oxoguanine triphosphatase.

Immunometabolic Dysfunction of Natural Killer Cells Mediated by the Hypoxia-CD73 Axis in Solid Tumors

NK cell infiltration into solid tumors is often low and is largely represented by the poorly-cytotoxic CD56^bright subset. Numerous studies have demonstrated that CD73, overexpressed under conditions of hypoxia, is involved in a variety of physiological processes, while its overexpression has been correlated with tumor invasiveness, metastasis and poorer patient survival in many cancers. Hypoxia itself favors aggressive glycolytic fueling of cancer cells, in turn driving reprogramming of NK cell metabolism. In addition, the hypoxia-driven activity of CD73 immunometabolically impairs NK cells in tumors, due to its catalytic role in the generation of the highly immunosuppressive metabolite adenosine. Adenosinergic signaling was shown to alter NK cell metabolic programs, leading to tumor-promoting environments characterized by NK cell dysfunction. Despite the demonstrated role of NK cell responses in the context of CD73 targeting, the engagement of NK cells in the setting of hypoxia/CD73 signaling has not been extensively studied or exploited. Here, we discuss available evidence on the role of hypoxic signaling on CD73-mediated activity, and how this relates to the immunometabolic responses of NK cells, with a particular focus on the therapeutic targeting of these pathways.

Targeting Adenosine in Cancer Immunotherapy to Enhance T-Cell Function

T cells play a critical role in cancer control, but a range of potent immunosuppressive mechanisms can be upregulated in the tumor microenvironment (TME) to abrogate their activity. While various immunotherapies (IMTs) aiming at re-invigorating the T-cell-mediated anti-tumor response, such as immune checkpoint blockade (ICB), and the adoptive cell transfer (ACT) of natural or gene-engineered ex vivo expanded tumor-specific T cells, have led to unprecedented clinical responses, only a small proportion of cancer patients benefit from these treatments. Important research efforts are thus underway to identify biomarkers of response, as well as to develop personalized combinatorial approaches that can target other inhibitory mechanisms at play in the TME. In recent years, adenosinergic signaling has emerged as a powerful immuno-metabolic checkpoint in tumors. Like several other barriers in the TME, such as the PD-1/PDL-1 axis, CTLA-4, and indoleamine 2,3-dioxygenase (IDO-1), adenosine plays important physiologic roles, but has been co-opted by tumors to promote their growth and impair immunity. Several agents counteracting the adenosine axis have been developed, and pre-clinical studies have demonstrated important anti-tumor activity, alone and in combination with other IMTs including ICB and ACT. Here we review the regulation of adenosine levels and mechanisms by which it promotes tumor growth and broadly suppresses protective immunity, with extra focus on the attenuation of T cell function. Finally, we present an overview of promising pre-clinical and clinical approaches being explored for blocking the adenosine axis for enhanced control of solid tumors.

Adenosine protects pancreatic beta cells against apoptosis induced by endoplasmic reticulum stress

Chronic exposure to high glucose induces endoplasmic reticulum (ER) stress in pancreatic beta cells (PBCs). The previous evidence showed that adenosine modulate PBCs viability and insulin secretion. The aim of this study was to evaluate possible involvement of adenosine in protection of MIN6 β-cells from Tunicamycin (Tu)-induced ER stress. MIN6 cells were cotreated with Tu and different concentrations of adenosine. Cell viability, proliferation, and apoptosis were evaluated using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT), 5-bromo-2'-deoxyuridine (Brdu), and colony formation assays. Caspase-12 activity was assayed using the fluorometric method. Thioflavin T (ThT) staining was used for the evaluation of protein aggregation. Insulin secretion was evaluated using specific an ELISA kit. Ca²⁺ mobilization assayed using Fura2/AM probe. BIP, CHOP, XBP-1, and XBP-1s expression in both messenger RNA (mRNA) and protein levels were evaluated using the reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. Bcl-2, p-eIF2α/eIF2α, and GADD34 levels also determined with Western blot analysis. Adenosine protected MIN6 cells against Tu-induced ER stress in a dose-dependent manner and increased their proliferation. Decreased caspase-12 activity and upregulated Bcl-2 protein may explain antiapoptotic effects of adenosine. ThT staining indicated an attenuated aggregation of misfolded proteins. Adenosine effectively increased insulin secretion in Tu-treated cells. BIP, CHOP, XBP1, and sXBP1 expression were decreased significantly in cotreated cells, indicating alleviation of ER stress. However, adenosine potentiated the expression of GADD34 and decreased p-eIF2α/eIF2α ratio. Adenosine increased cytosolic Ca ²⁺ levels, which may promote adenosine triphosphate (ATP) synthesis in mitochondria, helping ER to preserve protein hemostasis. Taken together, adenosine upregulated Bcl-2 and GADD34 to protect PBCs against Tu-induced apoptosis and increase Insulin secretion.

IPP-1 controls Akt/CREB phosphorylation extension in A2a adenosine receptor signaling cascade in MIN6 pancreatic β-cell line

Signaling through A_2a adenosine receptor specifically prevent pancreatic β-cells (PBCs) loses under diabetogenic conditions. However, signaling mediators of this receptor in PBCs remained unidentified. Thus, we aimed to investigate the possible involvement of PKA/Akt/IPP-1/CREB pathway in MIN6 β-cells. In addition, we investigated IPP-1 role in A_2a receptor signaling pathway. The expression of A_2a receptor in MIN6 cell line was evaluated by RT-PCR and its functionality confirmed by quantification of cAMP in response to the CGS 21680, an A_2a receptor agonist. MTT and Brdu assays were used to evaluate cell viability and proliferation, respectively. PKA activity and insulin release were evaluated using ELISA methods. P-Akt/Akt, p-IPP-1/IPP-1, and p-CREB/CREB levels were assessed using western blotting. IPP-1 knock down assessments was performed using specific siRNA. Our result revealed that MIN6 cells express A_2a receptor which actively increased cAMP levels (with EC₅₀ = 2.41 µM) and PKA activity. Activation of this receptor increased cell viability, proliferation and insulin release. Moreover, we mentioned A_2a receptor stimulation increased p-Akt, p-IPP-1, and p-CREB levels in dose (max at 10 µM of CGS 21680) and time (max at 30 min after CGS 21680 treatment) dependent manner. Interestingly, herein, we found in IPP-1 knocked down cells, A_2a receptor failed to activate Akt and CREB. Altogether, we mentioned that in MIN6 cells A_2a receptor increase cell viability, proliferation and insulin release through PKA/Akt/IPP-1/CREB signaling pathway. In addition, we conclude A_2a receptor signaling through this pathway is dependent to activation of IPP-1.

Galectin-9 induces apoptosis in OVCAR-3 ovarian cancer cell through mitochondrial pathway

Galectin-9 (Gal-9), a member of animal lectins' family, is implicated in the induction of apoptosis in various cancer cells. Here, we evaluated the anti-tumor effect of Gal-9 in OVCAR-3 ovarian cancer cells. The effect of the Gal-9 on cell viability was evaluated using MTT assays. Apoptosis was assessed using Annexin-V staining. The assessment of mitochondrial membrane potential (ΔΨm) was performed using a JC-1 probe. The activity of caspase-3 and caspase-6 were evaluated with colorimetric assay. The production of reactive oxygen species (ROS) was applied by fluorescent probe. The expression levels of Bax and Bcl-2 were assessed using western blotting. The result showed that Gal-9 inhibits cell viability. Flow cytometry analysis showed that Gal-9 induces apoptosis in ovarian cancer cells. Moreover, Gal-9 decreased ΔΨm and increased the generation of ROS and caspase-3 and caspase-6 activities in ovarian cancer cells. Moreover, Gal-9 induced expression of Bax as well as inhibited expression of Bcl-2. In conclusion, our results indicated that Gal-9 induced apoptosis in ovarian cancer cells through mitochondrial pathway.

A2a adenosine receptor agonist improves endoplasmic reticulum stress in MIN6 cell line through protein kinase A/ protein kinase B/ Cyclic adenosine monophosphate response element-binding protein/ and Growth Arrest And DNA-Damage-Inducible 34/ eukaryotic Initiation Factor 2α pathways

Endoplasmic reticulum (ER) stress is one of the main molecular events underlying pancreatic beta cell (PBC) failure, apoptosis, and a decrease in insulin secretion. Recent studies have highlighted the fundamental role of A2a adenosine receptor (A2aR) in potentiation of insulin secretion and proliferation of PBCs. However, possible protective effects of A2aR signaling against ER stress have not been elucidated yet. Thus, in the present study, we aimed to investigate the effects of A2aR activation in MIN6 beta cells undergoing tunicamycin (TM)-mediated ER stress. A2aR expression and activity were evaluated using real-time polymerase chain reaction and measurement of the cyclic adenosine monophosphate (cAMP), protein kinase A (PKA), phospho-protein kinase B or Akt (p-Akt)/Akt, and phospho-Cyclic adenosine monophosphate response element-binding protein/CREB levels in response to a specific agonist (CGS 21680). Survival and proliferation in TM and CGS 21680 cotreated cells were evaluated using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), annexin V-fluorescein isothiocyanate (FITC)/propidium iodide staining, colony formation, and 5-bromo-2'-deoxyuridine (Brdu) assays. In addition, the effects of A2aR stimulation on insulin secretion were evaluated using the enzyme-linked immunosorbent assay. B-cell lymphoma 2 (Bcl-2), phospho-eukaryotic Initiation Factor 2α (p-eIF2α)/eIF2α, growth arrest and DNA-damage-inducible 34 (GADD34), X-box binding protein 1 (XBP-1), spliced X-box binding protein 1 (XBP-1s), immunoglobulin heavy-chain-binding protein (BIP), and CCAAT-enhancer-binding protein homologous protein (CHOP) levels were evaluated using western blotting. Our results showed a decrease in A2aR expression and p-Akt/Akt and p-CREB/CREB levels in TM-pretreated cells. We also mentioned that CGS 21680 effectively increased cell survival, proliferation, and insulin secretion in TM-treated cells. The antiapoptotic effects were possibly mediated through Bcl-2 upregulation. Our western blotting results indicated that A2aR effectively downregulated p-eIF2α/eIF2α, XBP-1, XBP-1s, BIP, and CHOP levels, whereas GADD34 was upregulated. Altogether, the present study revealed that A2aR signaling through PKA/Akt/CREB mediators alleviated TM cytotoxicity effects in MIN6 beta cells. Thus, the stimulation of this receptor was seen as a new approach to control ER stress in the PBC cells.