Connexin-43 enhances tumor suppressing activity of artesunate via gap junction-dependent as well as independent pathways in human breast cancer cells

Molecular Interplay Between Non-Coding RNAs and Connexins and Its Possible Role in Cancer

Non-coding RNAs (ncRNAs) are sequences that do not encode for proteins and play key roles in different cellular processes, including cell proliferation and differentiation. On the other hand, connexins (Cxs) are transmembrane proteins that principally allow intercellular communication. In pathological conditions such as cancer, there is a deregulation in the expression and/or function of ncRNAs and Cxs, which in turn leads to an enhancement in the aggressive phenotype, such as a greater proliferative and invasive capacity. This suggests a plausible interplay between ncRNAs and Cxs. Based on that, this review aims to summarize the current knowledge regarding this relationship and to analyze how it may influence the development of aggressive traits in cancer cells and the clinicopathological features of cancer patients. Finally, we discuss the potential of ncRNAs and Cxs as promising clinical biomarkers for cancer diagnosis, prognosis, and therapeutic targeting.

Boosting Natural Killer Cells' Immunotherapy with Amoxicillin-Loaded Liposomes

Natural killer (NK) cell immunotherapy is a significant category in tumor therapy due to its potent tumor-killing and immunomodulatory effects. This research delves into exploring the mechanisms underlying the ability of amoxicillin to boost NK cell cytotoxicity in NK cell immunotherapy. Amoxicillin significantly enhances the cytotoxic activity of NK-92MI cells against MCF-7 cells by triggering the initiation of a cytolytic program in target cell-deficient NK-92MI cells and augmenting the degranulation level of NK-92MI cells in the presence of target cells. The ability of NK cells to recognize target cells was increased upon exposure to amoxicillin at low concentration (10 ng/mL). Additionally, the utilization of amoxicillin loaded in liposome (AMO@Liposome) for NK cell immunotherapy in a mouse breast cancer model resulted in an increased antitumor effect in comparison to without the treatment of AMO@Liposome. RNA transcriptome analysis showed that amoxicillin upregulated differential genes related to the synaptic vesicle cycle pathway and calcium signaling pathway, and FOSB, TNFRSF18, and H4C1 were identified as critical players. These studies suggest that the strategy of using amoxicillin in NK cell immunotherapy has potential applications in the field of tumor therapy.

Simvastatin Enhances the Cytotoxic Effects of Doxorubicin in a Mammary Adenocarcinoma Cell Model by Involving Connexin 43

Gap Junctions channels formed by Connexins (Cx) provide intercellular communication enabling the coordination of cell growth, differentiation, and metabolism, and their reduction has been shown in many tumor types. Expression levels of Cx43, the most extensively studied Gap Junctions forming protein, are reduced or completely absent in breast cancer cells, while their overexpression correlates with increased cellular permeability to anticancer agents and, consequently, reduced resistance to drug treatments. So, drug associations targeting Cx43 are being considered to overcome chemoresistance. Previous studies demonstrated that Simvastatin (Sim) interferes with Cx43 expression and localization, and chemo-sensitizing effects of Sim in several tumor cell lines treated with antineoplastic chemotherapeutics have been shown. This study aimed to evaluate whether Sim cotreatment enhances Doxorubicin-induced cytotoxicity by affecting Cx43 expression and/or phosphorylation, so MCF-7 cells were treated with Sim (10 µM) for 4 h and then coexposed to Sim and Doxorubicin (1 µM) for 20 h. In Sim cotreated cells, increased membrane levels of Cx43 have been shown; moreover, decreased levels of Cx43 phosphorylated on Ser368 and Ser262 residues, involved in channel closure and disruption of cell-cell communication, have been demonstrated in these cells. In Sim cotreated cells increased Doxorubicin uptake and enhanced Doxorubicin-induced cytotoxic effects have been demonstrated together with reduced migratory capacity. Our data support the notion that Sim cotreatment could be a possible strategy to overcome chemoresistance, since the observed increase in Cx43 membrane levels, and the concomitant reduction of Cx43 phosphorylation, could be responsible for increased sensitization of cells to Doxorubicin treatment.

Connexin-43 in Cancer: Above and Beyond Gap Junctions!

Connexin-43 (Cx43) is the most characterized gap junction protein, primarily involved in the Gap Junctional Intercellular Communication (GJIC) between adjacent cells to facilitate molecule exchange and the formation of a signaling network. It is increasingly evident that the importance of Cx43 is not only limited to its GJIC function, but rather includes its role in connecting the intracellular and extracellular environment by forming membrane hemichannels, as well as its intracellular signaling function mediated by its C-terminal tail (Cx43-CT). Notably, Cx43 has been implicated in a variety of cancers, with earlier notions suggesting a tumor-suppressor function, whereas new studies shed light on its pro-tumorigenic role. Moreover, apart from GJIC-based activities, the relevance of the non-canonical functions of Cx43 in tumor progression is being actively studied. This review provides an analysis of the current research on the pro-tumorigenic roles of Cx43, with a focus on Cx43-CT interactions and the function of hemichannels in cancer progression. A better understanding of the multifaceted functions of Cx43 in cancer biology could foster its recognition as a pivotal target for the development of innovative therapeutic strategies.

Studies on in vivo antithrombotic activity of quercetin, a natural flavonoid isolated from a traditional medicinal plant, African eggplant (Solanum indicum)

ETHNOPHARMACOLOGICAL RELEVANCE

Every year, cardiovascular diseases (CVDs) account for about 17.9 million deaths, making them the primary cause of both morbidity and mortality. Conventional drugs, which are often prescribed to treat cardiovascular diseases, are costly and have adverse effects. Consequently, dietary modifications and other medications are needed. Traditional use of Solanum indicum as cardiotonic to treat hypertension and anticoagulant potency has been reported but poorly evaluated scientifically.

AIM OF THE STUDY

This study investigated the in vivo anticoagulant activity and mechanism of anticoagulation of quercetin (QC), a bioactive compound isolated from S. indicum (SI) hydroethanolic fruit extract.

MATERIALS AND METHODS

Bioassay-guided fractionation (anticoagulant activity) extracted QC from hydroethanolic SI extract. QC was extensively characterized biochemically and pharmacologically. The interaction between QC and thrombin was investigated using spectrofluorometric and isothermal calorimetric methods. Cytotoxicity, antiplatelet, and thrombolytic studies were carried out in vitro. The Swiss albino mice were used to assess the in vivo, anticoagulant, and antithrombotic activities of QC.

RESULTS

QC exhibits anticoagulant activity via (i) uncompetitive inhibition of thrombin but not FXa with a Ki value of 33.11 ± 4.2 μM and (ii) a partial inhibition of thrombin-catalyzed platelet aggregation with an IC50 value of 13.2 ± 1.2 μM. The experimental validation of the in silico study's prediction of QC's binding to thrombin was confirmed by spectrofluorometric and isothermal calorimetric analyses. QC was nontoxic to mammalian, non-hemolytic cells and demonstrated thrombolytic activity by activating plasminogen. QC demonstrated in vivo anticoagulant efficacy, preventing k-carrageen-induced thrombus formation in mice's tails. In the acute circulatory stasis paradigm in mice, QC reduces thromboxane B2 (TXB2) and endothelin-1 (ET-1) while increasing nitric oxide synthase (eNOS) and 6-keto prostaglandin F1α (6-keto-PGF1 α).

CONCLUSION

Effective in vivo anticoagulant and antithrombotic properties of S. indicum's bioactive component QC point to the plant's potential use as a herbal anticoagulant medication for preventing and treating cardiovascular diseases linked to thrombosis.

Insights into the role of connexins and specialized intercellular communication pathways in breast cancer: Mechanisms and applications

Gap junctions, membrane-based channels comprised of connexin proteins (Cxs), facilitate direct communication among neighbouring cells and between cells and the extracellular space through their hemichannels. The normal human breast expresses various Cxs family proteins, such as Cx43, Cx30, Cx32, Cx46, and Cx26, crucial for proper tissue development and function. These proteins play a significant role in breast cancer development, progression, and therapy response. In primary tumours, there is often a reduction and cytoplasmic mislocalization of Cx43 and Cx26, while metastatic lesions show an upregulation of these and other Cxs. Although existing research predominantly supports the tumour-suppressing role of Cxs in primary carcinomas through channel-dependent and independent functions, controversies persist regarding their involvement in the metastatic process. This review aims to provide an updated perspective on Cxs in human breast cancer, with a specific focus on intrinsic subtypes due to the heterogeneous nature of this disease. Additionally, the manuscript will explore the role of Cxs in immune interactions and novel forms of intercellular communication, such as tunneling nanotubes and extracellular vesicles, within the breast tumour context and tumour microenvironment. Recent findings suggest that Cxs hold potential as therapeutic targets for mitigating metastasis and drug resistance. Furthermore, they may serve as novel biomarkers for cancer prognosis, offering promising avenues for future research and clinical applications.

Connexin 43 in Dermatofibroma and Dermatofibrosarcoma Protuberans: Diagnostic, Pathogenic, and Therapeutic Implications

ABSTRACT

Connexins play a crucial role in the formation of gap junctions that connect cells to each other, as well as cells to the surrounding environment. In recent years, connexin 43 has been extensively studied in various human tumors. In this study, we conducted an immunohistochemical analysis to evaluate the expression of connexin in 16 dermatofibromas (DFs) and 13 dermatofibrosarcoma protuberans (DFSP). Connexin was diffusely expressed in the cytoplasm of all DFs with moderate or strong intensity, whereas all DFSPs showed negative staining. In addition to its diagnostic implications, the loss of Cx43 may elucidate the invasive capacity of DFSP and offer a potential avenue for future therapeutic interventions.

A Histone Deacetylase Inhibitor Manifests Synergistic Interaction with Artesunate by Suppressing DNA Repair Activity

Artesunate (ART), a plant based semi-synthetic antimalarial drug, is emerging as a new class of effective cancer chemotherapeutics. However, the dosage of ART required to have an anti-cancer effect on cancer cells is greater than that needed to exterminate malarial parasites. The goal of this study was to develop an effective combination therapy to reduce the dose-dependent side effects of ART both in vitro and in vivo. In our study, 4-phenylbutyrate (4-PB), a histone deacetylase inhibitor (HDAC), exhibited significant synergistic induction of apoptosis in MCF-7 cells in combination with ART. The IC50 of ART decreased significantly from 55.56 ± 5.21 µM to 24.71 ± 3.44 µM in MCF-7 cells. ART treatment increased cellular oxidative stress, and the resulting generation of intracellular reactive oxygen species (ROS) caused extensive DNA damage in the cell. The extent of ROS production and cell cycle arrest were further enhanced by 4-PB treatment. In further investigation, we found that 4-PB attenuated mRNA expression of crucial DNA damage response (DDR) elements of the nonhomologous end-joining (NHEJ) pathway, consequently enhancing the DNA damaging effect of ART. Furthermore, the combination therapy resulted in improvement in the life expectancy of the treated mice and a prominent reduction in tumour volume without interfering with the normal biochemical, haematological and histological parameters of the mice. Overall, our study revealed a novel combination therapy in which 4-PB potentiated the cytotoxicity of ART synergistically and provided a promising combination drug for effective cancer therapy.

Artemisinins in Combating Viral Infections Like SARS-CoV-2, Inflammation and Cancers and Options to Meet Increased Global Demand

Artemisinin is a natural bioactive sesquiterpene lactone containing an unusual endoperoxide 1, 2, 4-trioxane ring. It is derived from the herbal medicinal plant Artemisia annua and is best known for its use in treatment of malaria. However, recent studies also indicate the potential for artemisinin and related compounds, commonly referred to as artemisinins, in combating viral infections, inflammation and certain cancers. Moreover, the different potential modes of action of artemisinins make these compounds also potentially relevant to the challenges the world faces in the COVID-19 pandemic. Initial studies indicate positive effects of artemisinin or Artemisia spp. extracts to combat SARS-CoV-2 infection or COVID-19 related symptoms and WHO-supervised clinical studies on the potential of artemisinins to combat COVID-19 are now in progress. However, implementing multiple potential new uses of artemisinins will require effective solutions to boost production, either by enhancing synthesis in A. annua itself or through biotechnological engineering in alternative biosynthesis platforms. Because of this renewed interest in artemisinin and its derivatives, here we review its modes of action, its potential application in different diseases including COVID-19, its biosynthesis and future options to boost production.

Progress on the study of the anticancer effects of artesunate

Artesunate (ART) is a derivative of artemisinin that is extracted from the wormwood plant Artemisia annua. ART is an antimalarial drug that has been shown to be safe and effective for clinical use. In addition to its antimalarial properties, ART has been attracting attention over recent years due to its reported inhibitory effects on cancer cell proliferation, invasion and migration. Therefore, ART has a wider range of potential clinical applications than first hypothesized. The aim of the present review was to summarize the latest research progress on the possible anticancer effects of ART, in order to lay a theoretical foundation for the further development of ART as a therapeutic option for cancer.

Artemisinins as a novel anti-cancer therapy: Targeting a global cancer pandemic through drug repurposing

Artemisinins are a unique class of antimalarial drugs with significant potential for drug repurposing for a wide range of diseases including cancer. Cancer is a leading cause of death globally and the majority of cancer related deaths occur in Low and Middle Income Countries (LMICs) where conventional treatment options are often limited by financial cost. Drug repurposing can significantly shorten new therapeutic discovery pathways, ensuring greater accessibility and affordability globally. Artemisinins have an excellent safety and tolerability profile as well as being affordable for deployment in Low and Middle Class Income Countries at around USD1 per daily dose. Robust, well designed clinical trials of artemisinin drug repurposing are indicated for a variety of different cancers and treatment settings.

Determination of Usnic Acid Responsive miRNAs in Breast Cancer Cell Lines

OBJECTIVE

Breast Cancer (BC) is the most common type of cancer diagnosed in women. A common treatment strategy for BC is still not available because of its molecular heterogeneity and resistance is developed in most of the patients through the course of treatment. Therefore, alternative medicine resources as being novel treatment options are needed to be used for the treatment of BC. Usnic Acid (UA) that is one of the secondary metabolites of lichens used for different purposes in the field of medicine and its anti-proliferative effect has been shown in certain cancer types, suggesting its potential use for the treatment.

METHODS

Anti-proliferative effect of UA in BC cells (MDA-MB-231, MCF-7, BT-474) was identified through MTT analysis. Microarray analysis was performed in cells treated with the effective concentration of UA and UA-responsive miRNAs were detected. Their targets and the pathways that they involve were determined using a miRNA target prediction tool.

RESULTS

Microarray experiments showed that 67 miRNAs were specifically responsive to UA in MDA-MB-231 cells while 15 and 8 were specific to BT-474 and MCF-7 cells, respectively. The miRNA targets were mostly found to play role in Hedgehog signaling pathway. TGF-Beta, MAPK and apoptosis pathways were also the prominent ones according to the miRNA enrichment analysis.

CONCLUSION

The current study is important as being the first study in the literature which aimed to explore the UA related miRNAs, their targets and molecular pathways that may have roles in the BC. The results of pathway enrichment analysis and anti-proliferative effects of UA support the idea that UA might be used as a potential alternative therapeutic agent for BC treatment.

Corrigendum to "Protoporphyrin IX tracer fluorescence modulation for improved brain tumor cell lines visualization"

Fluorescence image guided surgical resection (FIGR) of high grade gliomas (HGGs) takes advantage of the accumulation of the tracer protoporphyrin IX (PpIX) in glioma cells following administration of 5-aminolevulinic acid (5-ALA). Occasionally, PpIX fluorescence intensity may be insufficient, thus compromising the efficacy and precision of the surgical intervention. The cause for the signal variation is unclear and strategies to improve the intensity of PpIX fluorescence are considered necessary. We have previously shown that differential expression of the epidermal growth factor receptor in glioblastoma cells affects PpIX fluorescence. Herein, we investigated other factors impairing PpIX accumulation and pharmacological treatments able to enhance PpIX fluorescence in glioblastoma cells displaying lower signal. In the present study we demonstrate that presence of serum in cell culture medium and differences in cellular confluence can negatively influence PpIX accumulation in U87 cell lines. We hypothesized that PpIX fluorescence intensity results from the interplay between the metabolic clearance of PpIX mediated by ferrochelatase (FECH) and heme oxygenase-1 (HO-1) and the cellular efflux of PpIX through the ATP-binding cassette subfamily G member 2 (ABCG2). Based on the availability of compounds targeting these proteins and inhibiting them, in this study we used modulators such as genistein, an isoflavone able to inhibit ABCG2; deferoxamine, which chelate iron ions impairing FECH activity and tin protoporphyrin IX (SnPP), the specific HO-1 inhibitor. Finally, we showed the efficacy of a precisely tuned pharmacological treatment in increasing PpIX accumulation and consequently fluorescence in glioblastoma cells. This strategy may translate in more sensitive tracing of tumor cells in-vivo and improved FIGR of HGGs and possibly low grade gliomas (LGGs).

Impaired Endothelium-Dependent Hyperpolarization Underlies Endothelial Dysfunction during Early Metabolic Challenge: Increased ROS Generation and Possible Interference with NO Function

Endothelial dysfunction is a hallmark of diabetic vasculopathies. Although hyperglycemia is believed to be the culprit causing endothelial damage, the mechanism underlying early endothelial insult in prediabetes remains obscure. We used a nonobese high-calorie (HC)-fed rat model with hyperinsulinemia, hypercholesterolemia, and delayed development of hyperglycemia to unravel this mechanism. Compared with aortic rings from control rats, HC-fed rat rings displayed attenuated acetylcholine-mediated relaxation. While sensitive to nitric oxide synthase (NOS) inhibition, aortic relaxation in HC-rat tissues was not affected by blocking the inward-rectifier potassium (Kir) channels using BaCl2 Although Kir channel expression was reduced in HC-rat aorta, Kir expression, endothelium-dependent relaxation, and the BaCl2-sensitive component improved in HC rats treated with atorvastatin to reduce serum cholesterol. Remarkably, HC tissues demonstrated increased reactive species (ROS) in smooth muscle cells, which was reversed in rats receiving atorvastatin. In vitro ROS reduction, with superoxide dismutase, improved endothelium-dependent relaxation in HC-rat tissues. Significantly, connexin-43 expression increased in HC aortic tissues, possibly allowing ROS movement into the endothelium and reduction of eNOS activity. In this context, gap junction blockade with 18-β-glycyrrhetinic acid reduced vascular tone in HC rat tissues but not in controls. This reduction was sensitive to NOS inhibition and SOD treatment, possibly as an outcome of reduced ROS influence, and emerged in BaCl2-treated control tissues. In conclusion, our results suggest that early metabolic challenge leads to reduced Kir-mediated endothelium-dependent hyperpolarization, increased vascular ROS potentially impairing NO synthesis and highlight these channels as a possible target for early intervention with vascular dysfunction in metabolic disease. SIGNIFICANCE STATEMENT: The present study examines early endothelial dysfunction in metabolic disease. Our results suggest that reduced inward-rectifier potassium channel function underlies a defective endothelium-mediated relaxation possibly through alteration of nitric oxide synthase activity. This study provides a possible mechanism for the augmentation of relatively small changes in one endothelium-mediated relaxation pathway to affect overall endothelial response and highlights the potential role of inward-rectifier potassium channel function as a therapeutic target to treat vascular dysfunction early in the course of metabolic disease.

Naturally occurring anti-cancer compounds: shining from Chinese herbal medicine

Numerous natural products originated from Chinese herbal medicine exhibit anti-cancer activities, including anti-proliferative, pro-apoptotic, anti-metastatic, anti-angiogenic effects, as well as regulate autophagy, reverse multidrug resistance, balance immunity, and enhance chemotherapy in vitro and in vivo. To provide new insights into the critical path ahead, we systemically reviewed the most recent advances (reported since 2011) on the key compounds with anti-cancer effects derived from Chinese herbal medicine (curcumin, epigallocatechin gallate, berberine, artemisinin, ginsenoside Rg3, ursolic acid, silibinin, emodin, triptolide, cucurbitacin B, tanshinone I, oridonin, shikonin, gambogic acid, artesunate, wogonin, β-elemene, and cepharanthine) in scientific databases (PubMed, Web of Science, Medline, Scopus, and Clinical Trials). With a broader perspective, we focused on their recently discovered and/or investigated pharmacological effects, novel mechanism of action, relevant clinical studies, and their innovative applications in combined therapy and immunomodulation. In addition, the present review has extended to describe other promising compounds including dihydroartemisinin, ginsenoside Rh2, compound K, cucurbitacins D, E, I, tanshinone IIA and cryptotanshinone in view of their potentials in cancer therapy. Up to now, the evidence about the immunomodulatory effects and clinical trials of natural anti-cancer compounds from Chinese herbal medicine is very limited, and further research is needed to monitor their immunoregulatory effects and explore their mechanisms of action as modulators of immune checkpoints.

Disruption of gap junctions attenuates acute myeloid leukemia chemoresistance induced by bone marrow mesenchymal stromal cells

The bone marrow (BM) niche impacts the progression of acute myeloid leukemia (AML) by favoring the chemoresistance of AML cells. Intimate interactions between leukemic cells and BM mesenchymal stromal cells (BM-MSCs) play key roles in this process. Direct intercellular communications between hematopoietic cells and BM-MSCs involve connexins, components of gap junctions. We postulated that blocking gap junction assembly could modify cell–cell interactions in the leukemic niche and consequently the chemoresistance. The comparison of BM-MSCs from AML patients and healthy donors revealed a specific profile of connexins in BM-MSCs of the leukemic niche and the effects of carbenoxolone (CBX), a gap junction disruptor, were evaluated on AML cells. CBX presents an antileukemic effect without affecting normal BM-CD34⁺ progenitor cells. The proapoptotic effect of CBX on AML cells is in line with the extinction of energy metabolism. CBX acts synergistically with cytarabine (Ara-C) in vitro and in vivo. Coculture experiments of AML cells with BM-MSCs revealed that CBX neutralizes the protective effect of the niche against the Ara-C-induced apoptosis of leukemic cells. Altogether, these results suggest that CBX could be of therapeutic interest to reduce the chemoresistance favored by the leukemic niche, by targeting gap junctions, without affecting normal hematopoiesis.

Protoporphyrin IX tracer fluorescence modulation for improved brain tumor cell lines visualization

Fluorescence image guided surgical resection (FIGR) of high grade gliomas (HGGs) takes advantage of the accumulation of the tracer protoporphyrin IX (PpIX) in glioma cells following administration of 5-aminolevulinic acid (5-ALA). Occasionally, PpIX fluorescence intensity may be insufficient, thus compromising the efficacy and precision of the surgical intervention. The cause for the signal variation is unclear and strategies to improve the intensity of PpIX fluorescence are considered necessary. We have previously shown that differential expression of the epidermal growth factor receptor in glioblastoma cells affects PpIX fluorescence. Herein, we investigated other factors impairing PpIX accumulation and pharmacological treatments able to enhance PpIX fluorescence in glioblastoma cells displaying lower signal. In the present study we demonstrate that presence of serum in cell culture medium and differences in cellular confluence can negatively influence PpIX accumulation in U87 cell lines. We hypothesized that PpIX fluorescence intensity results from the interplay between the metabolic clearance of PpIX mediated by ferrochelatase and heme oxygenase-1 and the cellular efflux of PpIX through the ATP-binding cassette subfamily G member 2 (ABCG2). Based on the availability of compounds targeting these proteins and inhibiting them, in this study we used modulators such as genistein, an isoflavone able to inhibit ABCG2; deferoxamine, which chelate iron ions impairing FECH activity and tin protoporphyrin IX (SnPP), the specific HO-1 inhibitor. Finally, we showed the efficacy of a precisely tuned pharmacological treatment in increasing PpIX accumulation and consequently fluorescence in glioblastoma cells. This strategy may translate in more sensitive tracing of tumor cells in-vivo and improved FIGR of HGGs and possibly low grade gliomas (LGGs).

Pro-Apoptotic Effect of Grape Seed Extract on MCF-7 Involves Transient Increase of Gap Junction Intercellular Communication and Cx43 Up-Regulation: A Mechanism of Chemoprevention

Growing evidence suggests dietary antioxidants reduce the risk of several cancers. Grape seeds extracts (GSE) are a rich source of polyphenols known to have antioxidant, chemopreventive and anticancer properties. Herein, we investigated the in vitro effects and putative action mechanisms of a grape seed extract (GSE) on human breast cancer cells (MCF-7). The effects of GSE were evaluated on cell proliferation, apoptosis and gap-junction-mediated cell-cell communications (GJIC), as basal mechanism involved in the promotion stage of carcinogenesis. GSE (0.05-100 μg/mL) caused a significant dose- and time-dependent inhibition of MCF-7 viability and induced apoptotic cell death, as detected by Annexin-V/Propidium Iodide. Concurrently, GSE induced transient but significant enhancement of GJIC in non-communicating MCF-7 cells, as demonstrated by the scrape-loading/dye-transfer (SL/DT) assay and an early and dose-dependent re-localization of the connexin-43 (Cx43) proteins on plasma membranes, as assayed by immunocytochemistry. Finally, real-time-PCR has evidenced a significant increase in cx43 mRNA expression. The results support the hypothesis that the proliferation inhibition and pro-apoptotic effect of GSE against this breast cancer cell model are mediated by the GJIC improvement via re-localization of Cx43 proteins and up-regulation of cx43 gene, and provide further insight into the action mechanisms underlying the health-promoting action of dietary components.

Connexins in cancer: bridging the gap to the clinic

Gap junctions comprise arrays of intercellular channels formed by connexin proteins and provide for the direct communication between adjacent cells. This type of intercellular communication permits the coordination of cellular activities and plays key roles in the control of cell growth and differentiation and in the maintenance of tissue homoeostasis. After more than 50 years, deciphering the links among connexins, gap junctions and cancer, researchers are now beginning to translate this knowledge to the clinic. The emergence of new strategies for connexin targeting, combined with an improved understanding of the molecular bases underlying the dysregulation of connexins during cancer development, offers novel opportunities for clinical applications. However, different connexin isoforms have diverse channel-dependent and -independent functions that are tissue and stage specific. This can elicit both pro- and anti-tumorigenic effects that engender significant challenges in the path towards personalised medicine. Here, we review the current understanding of the role of connexins and gap junctions in cancer, with particular focus on the recent progress made in determining their prognostic and therapeutic potential.

Lipid nanobubbles as an ultrasound-triggered artesunate delivery system for imaging-guided, tumor-targeted chemotherapy

PURPOSE

Herein, this study is to prepare folic acid (FA)-conjugated lipid nanobubbles (NBs) that highly load artesunate (Arte; FA-ALNBs), as an ultrasound (US)-triggered Arte delivery system for imaging-guided, tumor-targeted chemotherapy.

MATERIALS AND METHODS

The morphology, size, zeta potential, and stability of the FA-ALNBs were detected by optical microscopy and dynamic light scattering analysis. The cellular uptake of the FA-ALNBs was evaluated by confocal laser scanning microscopy and flow cytometry.

RESULTS

The FA-ALNBs showed uniform spheroidal structure, with 781.2±5.3 nm in average diameter, great physiological stability, and ~91.9%±1.1% encapsulation efficiency of Arte. Using focused US, about 36.1%±2.5% of the entrapped Arte was trigger-released from the FA-ALNBs. Owing to the US contrast property, FA-ALNBs showed an enhanced US signal in vitro when using an ultrasonic diagnostic apparatus with a 1-MHz linear transducer. Due to the FA receptor-mediated endocytosis effect, FA-ALNBs can be efficiently internalized by cells, showing an uptake ratio of about 56.4%±3.1%. FA-ALNBs showed an enhanced, dose-dependent cell-killing ability, while FA-ALNBs plus US irradiation exhibited a stronger anticancer effect in vitro. Post intravenous injection into tumor-bearing mice, FA-ALNBs showed an enhanced US contrast effect with increase in time, indicating the increasing accumulation of FA-ALNBs in tumor tissue, which peaked at 4 hours post injection. Focused US irradiation was conducted on the tumor region at 4 hours post injection of FA-ALNBs, which showed a greater tumor suppression effect after 30 days of treatment compared with all other treatment groups. Moreover, FA-ALNBs showed negligible systemic toxicity in vivo.

CONCLUSION

This versatile US-triggered drug delivery system with great anticancer efficacy was assessed both in vitro and in vivo, revealing great potential as a cancer theranostic agent for future application.

Connexin-43 Enhances the Redesigned Cytosine Deaminase Activity for Suicide Gene Therapy in Human Breast Cancer Cells

Background:

Escherichia coli cytosine deaminase (CD) converts 5-fluorocytosine (5-FC), a prodrug, into 5-fluorouracil (5-FU), a chemotherapeutic drug. However, the poor binding affinity of CD towards 5-FC as compared to the natural substrate cytosine, limits its application towards a successful suicide gene therapy. Although F186W mutant was developed to enhance the effect of wild-type CD, still scope for its improvement remains to further minimize the dose-dependent cytotoxicity of the drugs. Hence, in this study, we employ the anti-tumour attribute of the gap junction forming protein connexin-43 (Cx43) in conjunction with CD or F186W mutant.

Methods:

Lipofectamine was used to co-transfect CD/F186W-pVITRO2 and Cx43-pEGFP-N1 plasmids construct into MCF-7 cells. Comparative analysis of cell viability was observed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) and trypan blue–based assays. To further confirm the mode of cell death was apoptosis, propidium iodide and annexin V/7-aminoactinomycin D (7-AAD)-based apoptosis assays were performed.

Results:

Semi-quantitative polymerase chain reaction (PCR) confirmed the expression of both Cx43 and CD/F186W genes after transfection. Furthermore, cell viability assays revealed the enhanced activity of F186W-Cx43 compared with CD-Cx43 and F186W alone. The trend of the reduction in cell viability was also reflected in the flow cytometry–based apoptosis analyses. Overall, F186W-Cx43 combination demonstrated its superiority over the CD-Cx43 and F186W mutant alone.

Conclusions:

The enhanced cytotoxic activity of F186W mutant was further amplified by gap junction protein Cx43.

First Report of Plant-Derived β-Sitosterol with Antithrombotic, in Vivo Anticoagulant, and Thrombus-Preventing Activities in a Mouse Model

Inhibitors of thrombin, a key enzyme in the blood coagulation cascade, are of great interest because of their selective specificity and effectiveness in anticoagulation therapy against cardiovascular disorders. The natural soybean phytosterol, β-sitosterol (BSS) demonstrated anticoagulant activity by dose-dependent inhibition of thrombin in an uncompetitive manner with a K_i value of 0.267 μM as well as by partial inhibition of thrombin-catalyzed platelet aggregation with a half-maximal inhibitory concentration (IC₅₀) value of 10.45 ± 2.88 μM against platelet-rich plasma and 9.2 ± 1.2 μM against washed platelets. An in silico study indicated binding of BSS to thrombin, which was experimentally verified by spectrofluorometric and isothermal calorimetric analyses. Under in vitro conditions, BSS demonstrated thrombolytic activity by activating plasminogen, albeit it is devoid of protease (fibrinogenolytic) activity. BSS was noncytotoxic to mammalian cells, nonhemolytic, demonstrated its in vivo anticoagulant activity when administered orally, and inhibited k-carrageen-induced thrombus formation in the tails of mice. Our results suggest that dietary supplementation of BSS may help to prevent thrombosis-associated cardiovascular disorders.

Polyethylene Glycol-Encapsulated Histone Deacetylase Inhibitor Drug-Composite Nanoparticles for Combination Therapy with Artesunate

Combination drug therapy has become an effective clinical practice for cancer treatment because of low cytotoxicity by the synergistic effect of each medicine. Luminescent Au nanoclusters (Au NCs) were formulated into spherical polyethylene glycol (PEG)-Au NC-encapsulated drug-sodium butyrate (NaB) composite nanoparticles (PEG-Au NC-NaB-NPs) in the presence of PEG and NaB. Their effect on cancer cells was investigated using bio imaging, unravelling the mechanism of the endocytosis pathway and combination therapeutic interventions with a plant-based antimalarial drug artesunate (ART). PEG-Au NC-NaB-NPs showed bright red luminescence in the lysosomal compartment of the cells upon uptake predominantly through a caveolae-mediated pathway. Combination of PEG-Au NC-NaB-NPs with ART displayed enhanced therapeutic activity at a reduced dose compared to its individual doses and revealed heightened synergistic activity as identified from the combination index. The mechanism of synergism revealed elevated generation of reactive oxygen species with both NaB and ART, which disrupts mitochondrial membrane potential as evident from JC-1 staining. Remarkably, the histone deacetylase (HDAC) assay and terminal deoxynucleotidyl transferase dUTP nick end labeling assay enlightened the role of NaB and ART in HDAC inhibition and DNA fragmentation, respectively. Thus, induction of apoptosis with the synergistic effect of both NaB and ART with its meticulous mechanism makes it a promising tool for combinational cancer therapy. In vivo activity of the NPs was evaluated on Daltons lymphoma ascites bearing mice, which exhibited significant reduction of tumor volume and viable tumor cells with a prolonged life span.

[Effect of gap junction modulation on antitumor effects of adriamycin in estrogen receptor-positive breast cancer cells]

OBJECTIVE

To observe the effect of functional modulation of gap junctions (GJ) on the antitumor effect of adriamycin in breast cancer cells positive for estrogen receptor (ER).

METHODS

The inhibitory effect of 0 to 24.0 μmol/L adriamycin on the surviving fraction of ER-positive human breast cancer MCF-7 cells and ER-negative MDA-MB-231 cells was assessed with MTT assay; Western blotting and immunofluorescence assay were used to detect the expressions of Cx43 total protein and membrane protein in the cells. A parachute assay was used to evaluate the function of the GJ in MCF-7 cells. The cytotoxic effect of adriamycin was observed in the cells treated with retinoic acid (RA) for enhancing GJ function, in cells treated with oleamide and 18-α- glycyrrhizic acid (18-α-ga) for inhibiting GJ function, and also in cells transfected with Cx43siRNA for Cx43 knockdown.

RESULTS

ER-positive MCF-7 cells expressed a significantly higher level of Cx43 with stronger GJ function than ER-negative MDA- MB-231 cells. Adriamycin significantly inhibited the proliferation of MCF-7 cells (P < 0.01), and RA treatment further increased the cytotoxicity of adriamycin (P < 0.01) while oleamide and 18-α-GA obviously attenuated the cytotoxicity of adriamycin (P < 0.01). In the cells with Cx43 knockdown, the expressions of total Cx43 protein and Cx43 on the membrane were significantly reduced, the function of GJ was attenuated, and the cytotoxicity of adriamycin was significantly decreased (P < 0.01).

CONCLUSIONS

ER-positive breast cancer cells have stronger Cx43 expressions and GJ function than the ERnegative cells. The cytotoxicity of adriamycin against the breast cancer cells can be strengthened by enhancing GJ function and attenuated by inhibiting GJ function. Cx43 silencing inhibits the function of GJ to lower the cytotoxicity of adriamycin in human breast cancer MCF-7 cells.

Anticoagulant mechanism, pharmacological activity, and assessment of preclinical safety of a novel fibrin(ogen)olytic serine protease from leaves of Leucas indica

The harnessing of medicinal plants containing a plethora of bioactive molecules may lead to the discovery of novel, potent and safe therapeutic agents to treat thrombosis-associated cardiovascular diseases. A 35 kDa (m/z 34747.5230) serine protease (lunathrombase) showing fibrin(ogen)olytic activity and devoid of N- and O- linked oligosaccharides was purified from an extract of aqueous leaves from L. indica. The LC-MS/MS analysis, de novo sequencing, secondary structure, and amino acid composition determination suggested the enzyme’s novel characteristic. Lunathrombase is an αβ-fibrinogenase, demonstrating anticoagulant activity with its dual inhibition of thrombin and FXa by a non-enzymatic mechanism. Spectrofluorometric and isothermal calorimetric analyses revealed the binding of lunathrombase to fibrinogen, thrombin, and/or FXa with the generation of endothermic heat. It inhibited collagen/ADP/arachidonic acid-induced mammalian platelet aggregation, and demonstrated antiplatelet activity via COX-1 inhibition and the upregulation of the cAMP level. Lunathrombase showed in vitro thrombolytic activity and was not inhibited by endogenous protease inhibitors α₂ macroglobulin and antiplasmin. Lunathrombase was non-cytotoxic to mammalian cells, non-hemolytic, and demonstrated dose-dependent (0.125–0.5 mg/kg) in vivo anticoagulant and plasma defibrinogenation activities in a rodent model. Lunathrombase (10 mg/kg) did not show toxicity or adverse pharmacological effects in treated animals.

Regulation of tumor-stroma interactions by the unfolded protein response

The unfolded protein response (UPR) is a conserved adaptive pathway that helps cells cope with the protein misfolding burden within the endoplasmic reticulum (ER). Imbalance between protein folding demand and capacity in the ER leads to a situation called ER stress that is often observed in highly proliferative and secretory tumor cells. As such, activation of the UPR signaling has emerged as a key adaptive mechanism promoting cancer progression. It is becoming widely acknowledged that, in addition to its intrinsic effect on tumor biology, the UPR can also regulate tumor microenvironment. In this review, we discuss how the UPR coordinates the crosstalk between tumor and stromal cells, such as endothelial cells, normal parenchymal cells, and immune cells. In addition, we further describe the involvement of ER stress signaling in the response to current treatments as well as its impact on antitumor immunity mainly driven by immunogenic cell death. Finally, in this context, we discuss the relevance of targeting ER stress/UPR signaling as a potential anticancer approach.