Salinomycin: A new paradigm in cancer therapy

Ophiobolin A derivatives with enhanced activities under tumor-relevant acidic conditions

Glioblastoma (GBM) is the most common form of malignant primary brain tumor and is one of the most lethal cancers. The difficulty in treating GBM stems from its highly developed mechanisms of drug resistance. Our research team has recently identified the fungal secondary metabolite ophiobolin A (OpA) as an agent with significant activity against drug-resistant GBM cells. However, the OpA's mode of action is likely based on covalent modification of its intracellular target(s) and thus possible off-target reactivity needs to be addressed. This work involves the investigation of an acid-sensitive OpA analogue approach that exploits the elevated acidity of the GBM microenvironment to enhance the selectivity for tumor targeting. This project identified analogues that showed selectivity at killing GBM cells grown in cultures at reduced pH compared to those maintained under normal neutral conditions. These studies are expected to facilitate the development of OpA as an anti-GBM agent by investigating its potential use in an acid-sensitive analogue form with enhanced selectivity for tumor targeting.

Hesperidin/Salinomycin Combination; a Natural Product for Deactivation of the PI3K/Akt Signaling Pathway and Anti-Apoptotic Factors in KG1a Cells

AML is a highly aggressive malignant clonal disease of hematopoietic origin. Hesperidin as a polyphenol glycoside, Activates the apoptotic pathway and salinomycin as a k + selective ionophore. We examined how hesperidin and salinomycin induce pro-apoptotic effects in KG1a cells. Cells were divided into four groups; 1) control cells (CRTL), 2) cells treated with hesperidin 85 μM, 3) cells treated with 2 μM salinomycin, 4) cells treated with combination of salinomycin and hesperidin. The MTT assay was implemented to determine the IC50 of hesperidin and salinomycin in KG1a cell lines. Propidium iodide staining and flow cytometry were used to analyze the distribution of the cell cycle. The level of ROS was evaluated by fluorescent microscopy and spectrophotometry. Additionally, Akt, XIAP, Bad, and FOXO1 gene expression was analyzed by real-time PCR. Hesperidin/Salinomycin decreased the viability of KG1a leukemic cells more than Hesperidin and Salinomycin separately. Changes in the shape of apoptotic cells and rise in ROS levels were detected after Hesperidin/Salinomycin treatment. Our findings showed that following Hesperidin/Salinomycin treatment, the expression of PI3K/AKT signaling pathway related genes (AKT, PTEN and FOXO1), were in line with the destruction of KG-1a cells. Furthermore, XIAP and BAD mRNA were regulated to trigger apoptosis in cancer cells. The study discovered that hesperidin and salinomycin, could effectively hinder the PI3K/Akt signaling pathway in leukemia cancer cells. Also, the combination of hesperidin and salinomycin has the potential to be a treatment option for acute myeloid leukemia.

Multifaceted effects of LRP6 in cancer: exploring tumor development, immune modulation and targeted therapies

Low-density lipoprotein receptor (LDLR)-related protein 6 (LRP6), a member of the LDLR superfamily of cell surface receptors, is most widely known as a crucial co-receptor in the activation of canonical Wnt/β-catenin signaling. This signaling pathway is implicated in multiple biological processes, such as lipoprotein metabolism, protease regulation, cell differentiation, and migration. LRP6 is frequently overexpressed in a variety of tumors, including liver cancer, colorectal cancer, and prostate cancer, and is generally considered an oncogene that promotes tumor proliferation, migration, and invasion. However, there are exceptions; some studies have reported that LRP6 inhibits lung metastasis of breast cancer through its ectodomain (LRP6N), and patients with low LRP6 expression tend to have a poor prognosis. Thus, the role of LRP6 in tumors remains controversial. Although limited studies have shown that LRP6 is associated with the expression and roles of a variety of immune cells in tumors, the interaction of LRP6 with the tumor microenvironment (TME) is not fully understood. Furthermore, it is crucial to acknowledge that LRP6 can engage with alternative pathways, including the mTORC1, CXCL12/CXCR4, and KRAS signaling pathways mentioned earlier, resulting in the regulation of biological functions independent of canonical Wnt/β-catenin signaling. Due to the potential of LRP6 as a molecular target for cancer therapy, various treatment modalities have been developed to directly or indirectly inhibit LRP6 function, demonstrating promising anti-cancer effects across multiple cancer types. This review will concentrate on exploring the expression, function, and potential therapeutic applications of LRP6 in different cancer types, along with its influence on the TME.

Plasticity and resistance of cancer stem cells as a challenge for innovative anticancer therapies - do we know enough to overcome this?

According to the CSC hypothesis, cancer stem cells are pivotal in initiating, developing, and causing cancer recurrence. Since the identification of CSCs in leukemia, breast cancer, glioblastoma, and colorectal cancer in the 1990s, researchers have actively investigated the origin and biology of CSCs. However, the CSC hypothesis and the role of these cells in tumor development model is still in debate. These cells exhibit distinct surface markers, are capable of self-renewal, demonstrate unrestricted proliferation, and display metabolic adaptation. CSC phenotypic plasticity and the capacity to EMT is strictly connected to the stemness state. CSCs show high resistance to chemotherapy, radiotherapy, and immunotherapy. The plasticity of CSCs is significantly influenced by tumor microenvironment factors, such as hypoxia. Targeting the genetic and epigenetic changes of cancer cells, together with interactions with the tumor microenvironment, presents promising avenues for therapeutic strategies. See also the Graphical abstract(Fig. 1).

Therapeutic Approaches of Dual-targeted Nanomedicines for Tumor Multidrug Resistance

Currently, the main cause of cancer chemotherapy failure is multi-drug resistance (MDR), which involves a variety of complex mechanisms. Compared with traditional small-molecule chemotherapy, targeted nanomedicines offer promising alternative strategies as an emerging form of therapy, especially active targeted nanomedicines. However, although single-targeted nanomedicines have made some progress in tumor therapy, the complexity of tumor microenvironment and tumor heterogeneity limits their efficacy. Dual-targeted nanomedicines can simultaneously target two tumor-specific factors that cause tumor MDR, which have the potential in overcoming tumor MDR superior to single-targeted nanomedicines by further enhancing cell uptake and cytotoxicity in new forms, as well as the effectiveness of tumor-targeted delivery. This review discusses tumor MDR mechanisms and the latest achievements applied to dual-targeted nanomedicines in tumor MDR.

The Effect of the Supplementation of Humic Substances and Fermented Products in the Feed on the Content of Salinomycin Residues in Poultry Tissues

The presence of antimicrobial residues in products of animal origin is a constant problem for consumer health. The aim of this study was to observe the effect of the addition of humic substances (H), fermented products (F) and a mixture of both (FH) to feed supplemented with the coccidiostat salinomycin, compared with a control group (C), on the content of salinomycin residues in the edible tissues of broiler chickens using two microbial inhibition screening methods, Explorer 2.0 test and the Screening Test for Antibiotic Residues (STAR), and a confirmatory competitive enzyme immunoassay analysis (Salinomycin ELISA Kit). The results of the microbial inhibition tests showed a gradual decline in the positive results in the tissue samples from the last day of salinomycin administration (30th day) tothe last day of fattening (37th day, day of slaughter) in group C and no positive results in the tissue samples from experimental groups H, F and FH slaughtered on the last day of fattening. Using the Salinomycin ELISA Kit, salinomycin was detected in the chicken muscle tissues of all the control and experimental groups. However, no sample from any group contained salinomycin at a concentration exceeding the maximum residue limits set by European law. The high level of significance (p < 0.001) confirmed the positive influence of the administration of humic substances and fermented products on the content of salinomycin residues in chicken tissues.

FTO-mediated LINC01134 stabilization to promote chemoresistance through miR-140-3p/WNT5A/WNT pathway in PDAC

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer most frequently detected at an advanced stage that limits treatment options to systemic chemotherapy, which has provided only marginal positive clinical outcomes. Currently, the first-line chemotherapeutic agent for PDAC is gemcitabine (GEM). However, the chemotherapy resistance to GEM is often overlooked in the clinical treatment of PDAC due to the lack of effective biological markers. Therefore, it is crucial to find new prognostic markers and therapeutic targets for patients with PDAC. In this study, we identified a novel regulatory mechanism in the development of resistance to GEM in PDAC. Here, we report that LINC01134 was significantly upregulated in primary tumors from PDAC patients. In vitro and in vivo functional studies revealed that LINC01134 promotes PDAC resistance to GEM through facilitating stem cell features and modulating the cell cycle. Mechanistically, LINC01134 interactes with tumor suppressor miR-497-5p in PDAC cells. Increased LINC01134 downregulates miR-140-3p to promotes the oncogenic WNT5A expression. Moreover, m6A demethylase FTO participated in the upregulation of LINC01134 by maintaining LINC01134 mRNA stability through YTHDF2. Taken together, the present study suggested FTO-mediated LINC01134 stabilization to promote chemotherapy resistance to GEM through miR-140-3p/WNT5A/WNT pathway in PDAC. Our study identified new prognostic markers and new therapeutic targets for patients with PDAC.

Emerging therapeutic strategy for mitigating cancer progression through inhibition of sirtuin-1 and epithelial-mesenchymal transition

With 8.8 million deaths worldwide, cancer is the major reason for the high rate of fatalities. Malignancy's commencement, progression, development, metastasis, and therapy resistance have all been correlated with the epithelial-to-mesenchymal transition (EMT) pathway. EMT promotes the cancer cells' metastatic spread and starts the development of treatment resistance. Sirtuin-1 (SIRT1) is a histone deacetylase that is important for signaling, cell persistence, and apoptosis. It does this by deacetylating important cell signaling molecules and proteins that are associated with apoptosis. The function of SIRT1 in EMT and cancer progression, as well as the emerging therapeutic strategy of treating cancer through the inhibition of SIRT1 and EMT will be discussed in detail.

Feline SCCs of the Head and Neck Display Partial Epithelial-Mesenchymal Transition and Harbor Stem Cell-like Cancer Cells

Squamous cell carcinoma of the head and neck (HNSCC) is a malignant cancer disease in humans and animals. There is ample evidence that the high plasticity of cancer cells, i.e., their ability to switch from an epithelial to a mesenchymal, endothelial, and stem cell-like phenotype, chiefly contributes to progression, metastasis, and multidrug resistance of human HNSCCs. In feline HNSCC, the field of cancer cell plasticity is still unexplored. In this study, fourteen feline HNSCCs with a known feline papillomavirus (FPV) infection status were subjected to histopathological grading and subsequent screening for expression of epithelial, mesenchymal, and stem cell markers by immunohistochemistry (IHC) and immunofluorescence staining (IF). Irrespective of the FPV infection status, all tumors except one corresponded to high-grade, invasive lesions and concurrently expressed epithelial (keratins, E-cadherin, β-catenin) and mesenchymal (vimentin, N-cadherin, CD146) proteins. This finding is indicative for partial epithelial-mesenchymal transition (pEMT) events in the lesions, as similarly described for human HNSCCs. IF double staining revealed the presence of CD44/CD271 double-positive cells notably within the tumors' invasive fronts that likely correspond to cancer stem cells. Taken together, the obtained findings suggest that feline HNSCCs closely resemble their human counterparts with respect to tumor cell plasticity.

Oxidative stress induction by narasin augments doxorubicin's efficacy in osteosarcoma

Complications and fata toxicity induced by chemotherapy are the main challenge for clinical management of osteosarcoma. The identification of agents that can augment the efficacy of chemotherapy at lower doses may represent an alternative therapeutic strategy. Narasin is a polyether antibiotic widely used in veterinary medicine. In this study, we show that narasin is active against osteosarcoma cells at the same concentrations that are less toxic to normal cells. This effect is achieved by growth inhibition and apoptosis induction, which is mediated by oxidative stress and damage, and mitochondrial dysfunction. The antioxidant N-acetyl-l-cysteine (NAC) abolishes the anti-osteosarcoma activity. Importantly, narasin significantly augments doxorubicin's efficacy in both osteosarcoma cell culturing system and subcutaneous implantation mouse model. The combination of narasin and doxorubicin at non-toxic doses completely arrests osteosarcoma growth in mice. Our results suggest that the concurrent administration of doxorubicin and narasin could present a viable alternative therapeutic approach for osteosarcoma.

Mitochondria in oral cancer stem cells: Unraveling the potential drug targets for new and old drugs

Head and neck cancer is a major health problem worldwide, with most cases arising in the oral cavity. Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer, accounting for over 90% of all cases. Compared to other types of cancer, OSCC, has the worse prognosis, with a 5-year survival rate of 50%. Additionally, OSCC is characterized by a high rate of resistance to chemotherapy treatment, which may be partly explained by the presence of cancer stem cells (CSC) subpopulation. CSC can adapt to harmful environmental condition and are highly resistant to both chemotherapy and radiotherapy treatments, thus contributing to tumor relapse. The aim of this review is to highlight the role of mitochondria in oral CSC as a potential target for oral cancer treatment. For this purpose, we reviewed some fundamental aspects of the most validated protein markers of stemness, autophagy, the mitochondrial function and energy metabolism in oral CSC. Moreover, a discussion will be made on why energy metabolism, especially oxidative phosphorylation in CSC, may offer such a diverse source of original pharmacological target for new drugs. Finally, we will describe some drugs able to disturb mitochondrial function, with emphasis on those aimed to interrupt the electron transport chain function, as novel therapeutic strategies in multidrug-resistant oral CSC. The reutilization of old drugs approved for clinical use as new antineoplastics, in cancer treatment, is also matter of revision.

Investigating the effects of essential oils and pure botanical compounds against Eimeria tenella in vitro

Essential oils (EO) and natural bioactive compounds are well-known antibacterial and anti-inflammatory factors; however, little is known about their anticoccidial activity and mode of action. EO deriving from basil (BEO), garlic (GAR), oregano (OEO), thyme (TEO), and their main bioactive compounds were investigated for their anticoccidial proprieties and compared to salinomycin (SAL) and amprolium (AMP) in vitro. The invasion of Eimeria tenella sporozoites was studied on 2 cell models: Madin-Darby Bovine Kidney (MDBK) cells and primary chicken epithelial cells (cIEC). Invasion efficiency was evaluated at 2 and 24 h postinfection (hpi) with counts of extracellular sporozoites and by detection of intracellular E. tenella DNA by PCR. Results show that at both timepoints, the EO were most effective in preventing the invasion of E. tenella with an average reduction of invasion at 24 hpi by 36% in cIEC and 55% in MDBK. The study also examined cytokine gene expression in cIEC at 24 hpi and found that AMP, BEO, OEO, TEO, carvacrol (CAR), and thymol (THY) significantly reduced interleukin (IL)8 expression, with CAR also reducing expression of IL1β and IL6 compared to the infected control. In addition, this work investigated the morphology of E. tenella sporozoites treated with anticoccidial drugs and EO using a scanning electron microscope. All the treatments induced morphological anomalies, characterized by a reduction of area, perimeter and length of sporozoites. SAL had a significant impact on altering sporozoite shape only at 24 h, whereas CAR and THY significantly compromised the morphology already at 2 hpi, compared to the untreated control. OEO and GAR showed the most significant alterations among all the treatments. The findings of this study highlight the potential of EO as an alternative to traditional anticoccidial drugs in controlling E. tenella invasion and in modulating primary immune response.

S-Adenosylmethionine: more than just a methyl donor

Covering: from 2000 up to the very early part of 2023S-Adenosyl-L-methionine (SAM) is a naturally occurring trialkyl sulfonium molecule that is typically associated with biological methyltransfer reactions. However, SAM is also known to donate methylene, aminocarboxypropyl, adenosyl and amino moieties during natural product biosynthetic reactions. The reaction scope is further expanded as SAM itself can be modified prior to the group transfer such that a SAM-derived carboxymethyl or aminopropyl moiety can also be transferred. Moreover, the sulfonium cation in SAM has itself been found to be critical for several other enzymatic transformations. Thus, while many SAM-dependent enzymes are characterized by a methyltransferase fold, not all of them are necessarily methyltransferases. Furthermore, other SAM-dependent enzymes do not possess such a structural feature suggesting diversification along different evolutionary lineages. Despite the biological versatility of SAM, it nevertheless parallels the chemistry of sulfonium compounds used in organic synthesis. The question thus becomes how enzymes catalyze distinct transformations via subtle differences in their active sites. This review summarizes recent advances in the discovery of novel SAM utilizing enzymes that rely on Lewis acid/base chemistry as opposed to radical mechanisms of catalysis. The examples are categorized based on the presence of a methyltransferase fold and the role played by SAM within the context of known sulfonium chemistry.

Salinomycin disturbs Golgi function and specifically affects cells in epithelial-to-mesenchymal transition

Epithelial-to-mesenchymal transition (EMT) gives rise to cells with properties similar to cancer stem cells (CSCs). Targeting the EMT program to selectively eliminate CSCs is a promising way to improve cancer therapy. Salinomycin (Sal), a K+/H+ ionophore, was identified as highly selective towards CSC-like cells, but its mechanism of action and selectivity remains elusive. Here, we show that Sal, similar to monensin and nigericin, disturbs the function of the Golgi. Sal alters the expression of Golgi-related genes and leads to marked changes in Golgi morphology, particularly in cells that have undergone EMT. Moreover, Golgi-disturbing agents severely affect post-translational modifications of proteins, including protein processing, glycosylation and secretion. We discover that the alterations induced by Golgi-disturbing agents specifically affect the viability of EMT cells. Collectively, our work reveals a novel vulnerability related to the EMT, suggesting an important role for the Golgi in the EMT and that targeting the Golgi could represent a novel therapeutic approach against CSCs.

The tale of antibiotics beyond antimicrobials: Expanding horizons

Antibiotics had proved to be a godsend for mankind since their discovery. They were once the magical solution to the vexing problem of infection-related deaths. German scientist Paul Ehrlich had termed salvarsan as the silver bullet to treatsyphilis.As time passed, the magic of newly discovered silver bullets got tarnished with raging antibiotic resistance among bacteria and associated side-effects. Still, antibiotics remain the primary line of treatment for bacterial infections. Our understanding of their chemical and biological activities has increased immensely with advancement in the research field. Non-antibacterial effects of antibiotics are studied extensively to optimise their safer, broad-range use. These non-antibacterial effects could be both useful and harmful to us. Various researchers across the globe including our lab are studying the direct/indirect effects and molecular mechanisms behind these non-antibacterial effects of antibiotics. So, it is interesting for us to sum up the available literature. In this review, we have briefed the possible reason behind the non-antibacterial effects of antibiotics, owing to the endosymbiotic origin of host mitochondria. We further discuss the physiological and immunomodulatory effects of antibiotics. We then extend the review to discuss molecular mechanisms behind the plausible use of antibiotics as anticancer agents.

F3 peptide functionalized liquid crystalline nanoparticles for delivering Salinomycin against breast cancer

Salinomycin (Sal) is a potent veterinary antibiotic known to offer significant toxicity to the variety of neoplastic cells. Its therapeutic utility is limited due to its higher lipophilicity (logP 7.5) and poor hydrophilicity. Liquid crystalline nanoparticles (LCNPs) known to offer a suitable delivery platform for these kinds of drugs. The overexpressed nucleolin receptor on the cell surface and cytoplasm, could be selected as a target in cancer therapy. The present study involves the development and characterization of the F3 peptide functionalized LCNPs for delivering Sal (F3-Sal-NPs) for selectively targeting to the nucleolin receptor. The optimized LCNPs were characterized for particle size, zeta potential, surface morphology, drug release kinetics and stability. The LCNPs have a structure similar to nematic phases. In vitro drug release studies revealed sustained drug release characteristics (89.5 ± 1.5% at 120 h) with F3-Sal-NPs. The cytotoxicity results demonstrated that F3-Sal-NPs were 4.8, 2.6 and 5.5 folds more effective than naïve drug in MDA-MB-468, MDA-MB-231 and MCF-7 cells, respectively and the cell cycle was arrested in the S and G2/M phases. The expression of the gene responsible for the stemness (CD44 gene), apoptosis (BAX/Bcl-2 ration) and angiogenesis (LCN-2) was reduced by F3-Sal-NPs treatment. Ex vivo hemolytic toxicity was reduced (6.5 ± 1.5%) and the pharmacokinetics and bioavailability of Sal was improved with F3-Sal-NPs. The in vivo antitumor efficacy was tested in EAC bearing mice, where F3-Sal-NPs significantly reduced the tumor growth by 2.8-fold compared to pure Sal and induced necrosis of tumor cells. The results clearly demonstrate the outstanding performance of F3 peptide functionalized LCNPs for delivering Sal against breast cancer.

Therapeutic vulnerabilities of cancer stem cells and effects of natural products

Covering: 1995 to 2022Tumors possess both genetic and phenotypic heterogeneity leading to the survival of subpopulations post-treatment. The term cancer stem cells (CSCs) describes a subpopulation that is resistant to many types of chemotherapy and which also possess enhanced migratory and anchorage-independent growth capabilities. These cells are enriched in residual tumor material post-treatment and can serve as the seed for future tumor re-growth, at both primary and metastatic sites. Elimination of CSCs is a key goal in enhancing cancer treatment and may be aided by application of natural products in conjunction with conventional treatments. In this review, we highlight molecular features of CSCs and discuss synthesis, structure-activity relationships, derivatization, and effects of six natural products with anti-CSC activity.

Novel Cerium(IV) Coordination Compounds of Monensin and Salinomycin

The largely uncharted complexation chemistry of the veterinary polyether ionophores, monensic and salinomycinic acids (HL) with metal ions of type M⁴⁺ and the known antiproliferative potential of antibiotics has provoked our interest in exploring the coordination processes between MonH/SalH and ions of Ce⁴⁺. (1) Methods: Novel monensinate and salinomycinate cerium(IV)-based complexes were synthesized and structurally characterized by elemental analysis, a plethora of physicochemical methods, density functional theory, molecular dynamics, and biological assays. (2) Results: The formation of coordination species of a general composition [CeL₂(OH)₂] and [CeL(NO₃)₂(OH)], depending on reaction conditions, was proven both experimentally and theoretically. The metal(IV) complexes [CeL(NO₃)₂(OH)] possess promising cytotoxic activity against the human tumor uterine cervix (HeLa) cell line, being highly selective (non-tumor embryo Lep-3 vs. HeLa) compared to cisplatin, oxaliplatin, and epirubicin.

Wnt Signaling Inhibitors and Their Promising Role in Tumor Treatment

In a continuous search for the improvement of antitumor therapies, the inhibition of the Wnt signaling pathway has been recognized as a promising target. The altered functioning of the Wnt signaling in human tumors points to the strategy of the inhibition of its activity that would impact the clinical outcomes and survival of patients. Because the Wnt pathway is often mutated or epigenetically altered in tumors, which promotes its activation, inhibitors of Wnt signaling are being intensively investigated. It has been shown that knocking down specific components of the Wnt pathway has inhibitory effects on tumor growth in vivo and in vitro. Thus, similar effects are expected from the application of Wnt inhibitors. In the last decades, molecules acting as inhibitors on the pathway’s specific molecular levels have been identified and characterized. This review will discuss the inhibitors of the canonical Wnt pathway, summarize knowledge on their effectiveness as therapeutics, and debate their side effects. The role of the components frequently mutated in various tumors that are principal targets for Wnt inhibitors is also going to be brought to the reader’s attention. Some of the molecules identified as Wnt pathway inhibitors have reached early stages of clinical trials, and some have only just been discovered. All things considered, inhibition of the Wnt signaling pathway shows potential for the development of future therapies.

Polylactic acid based biodegradable hybrid block copolymeric nanoparticle mediated co-delivery of salinomycin and doxorubicin for cancer therapy

Existence of cancer stem cells (CSCs) are primarily responsible for chemoresistance, cancer reoccurrence and treatment failure in cancer patients. Eliminating CSCs along with bulk tumor is a necessity to achieve complete cancer inhibition. Salinomycin (SAL) has potential to specifically target and kill CSCs through blocking their multiple pathways simultaneously. SAL has also been reported to improve anti-cancer efficacy of numerous chemo-based drugs when used in combination therapy. However, clinical use of SAL is restricted due to its high off targeted toxicity. Herein, we have developed a PLA based hybrid block copolymer for concomitant delivery of SAL and doxorubicin (DOX) with an aim to reduce their adverse side effects and enhance the therapeutic efficacy of the treatment. Designed PLA based nanoplatform showed high encapsulation and sustained release profile for both the drugs. Cytotoxicity evaluation on cancer cell lines confirmed the synergistic effect of SAL:DOX co-loaded NPs. Additionally, prepared SAL NPs were also found to be highly effective against chemo-resistant cancer cells and CSCs derived from cancer patient. Most importantly, encapsulation of SAL in PLA NPs improved its pharmacokinetics and biodistribution profile. Consequently, undesired toxicity with SAL NPs was significantly reduced which in-turn increased the dose tolerability in mice as compared to free SAL. Treatment of EAC tumor bearing mice with SAL:DOX co-loaded NPs resulted in excellent tumor regression and complete inhibition of cancer reoccurrence. These results conclude that concomitant delivery of SAL and DOX using PLA based block copolymeric nano-carrier have a strong potential for cancer therapy.

The Small RNA Landscape in NSCLC: Current Therapeutic Applications and Progresses

Non-small-cell lung cancer (NSCLC) is the second most diagnosed type of malignancy and the first cause of cancer death worldwide. Despite recent advances, the treatment of choice for NSCLC patients remains to be chemotherapy, often showing very limited effectiveness with the frequent occurrence of drug-resistant phenotype and the lack of selectivity for tumor cells. Therefore, new effective and targeted therapeutics are needed. In this context, short RNA-based therapeutics, including Antisense Oligonucleotides (ASOs), microRNAs (miRNAs), short interfering (siRNA) and aptamers, represent a promising class of molecules. ASOs, miRNAs and siRNAs act by targeting and inhibiting specific mRNAs, thus showing an improved specificity compared to traditional anti-cancer drugs. Nucleic acid aptamers target and inhibit specific cancer-associated proteins, such as "nucleic acid antibodies". Aptamers are also able of receptor-mediated cell internalization, and therefore, they can be used as carriers of secondary agents giving the possibility of producing very highly specific and effective therapeutics. This review provides an overview of the proposed applications of small RNAs for NSCLC treatment, highlighting their advantageous features and recent advancements in the field.

PDIA4 confers resistance to ferroptosis via induction of ATF4/SLC7A11 in renal cell carcinoma

The prognosis of renal cell carcinoma (RCC) remains poor due to metastases and resistance to chemotherapy. Salinomycin (Sal) exhibits the potential of antitumor, while the underlying mechanism is not completely clear. Here, we found that Sal induced ferroptosis in RCCs and identified Protein Disulfide Isomerase Family A Member 4 (PDIA4) as a mediator of Sal's effect on ferroptosis. Sal suppressed PDIA4 by increasing its autophagic degradation. Downregulation of PDIA4 increased the sensitivity to ferroptosis, while ectopic overexpression of PDIA4 conferred ferroptosis resistance to RCCs. Our data showed that downregulation of PDIA4 suppressed activating transcription factor 4 (ATF4) and its downstream protein SLC7A11 (solute carrier family 7 member 11), thereby aggravating ferroptosis. In vivo, the administration of Sal promoted ferroptosis and suppressed tumor progress in the xenograft mouse model of RCC. Bioinformatical analyses based on clinical tumor samples and database indicated a positive correlation exists between PDIA4 and PERK/ATF4/SLC7A11 signaling pathway, as well as the malignant prognosis of RCCs. Together, our findings reveal that PDIA4 promotes ferroptosis resistance in RCCs. Treatment of Sal sensitizes RCC to ferroptosis via suppressing PDIA4, suggesting the potential therapeutical application in RCCs.

Tongguanteng injection reverses paclitaxel resistance via upregulation of TAB1 expression in ovarian cancer in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Tongguanteng injection (TGT), the water extract from the stem of the Traditional Chinese hebal medicine of Marsdenia tenacissima (Roxb.) Wight et Arn. has been used as anticancer remedy for decades. TGT was not only used in the treatment of many malignant cancers extensively, but also an adjuvant anticancer drug with chemotherapeutics clinically.

AIM OF THE STUDY

To evaluate the effects of TGT on reversing paclitaxel (PTX) resistance and investigate the potential mechanism related to TAB1 in ovarian cancer (OC) in vitro and in vivo.

MATERIALS AND METHODS

The synergistic effect and reversal ratio were determined by CCK8 assay and median-effect principle after the combination of TGT and PTX in OC A2780 and its PTX-resistant (A2780/T) cells. The biological functions in cell apoptosis, migration and invasion of A2780/T cells treated by PTX 4 μM with TGT 20, 40, 80 mg⋅mL^-1 for 24 h were evaluated by colony formation, flow cytometry, wound healing and transwell assays. Proteomics technique and bioinformatic analysis were used to indentify the change of TAB1 expression in A2780/T cells induced by TGT. The association between TAB1 expression and human OC was analyzed by gene expression databases. In A2780/T cells, western blotting and colony formation assays were used to investigate the relationship between TAB1 expression and PTX resistance after TAB1 overexpression by TAB1 plasmids. The mechanism of TGT and PTX regulating TAB1 and its related proteins were explored by western blotting and flow cytometry assays after TAB1 knock-down using siTAB1. Moreover, TUNEL staining, immunohistochemistry (IHC) and histopathology were used to observe the antitumor effects, TAB1 and p-p38 expression and the tissues impairments in nude mice xenograft model established by A2780/T cells after the co-treatment with TGT and PTX by in vivo.

RESULTS

TGT combined with PTX showed the synergistic effect (CI<1), which could reverse the IC₅₀ values of PTX in OC A2780 and A2780/T cells about 23.50 and 6.44 times, respectively. Besides, TGT combined with PTX could significantly inhibit the migration, invasion and promote apoptosis of A2780/T cells. We identified that TGT could induce TAB1 expression in A2780/T cells by proteomics analysis. TAB1 downregulation was significantly associated with tumorigenesis and poor prognosis in OC patients and PTX resistance in A2780/T cells. Furthermore, TGT could activate TAB1/TAK1/p38 MAPK signaling pathway targeting TAB1 and regulate the expression of Bax, Bcl-2 proteins to improve the sensitivity of A2780/T cells to PTX. TGT combined with PTX also showed a greater inhibition in tumor growth than PTX monotherapy in vivo. These promising results show the efficacy of TGT in reversing PTX resistance and provide a potential strategy that targeting TAB1/TAK1/p38 MAPK signaling pathway may improve the chemotherapy sensitivity in OC.

CONCLUSIONS

Our results revealed that Tongguanteng injection could reverse paclitaxel resistance and the potential mechanism might be associated with the activation of TAB1/TAK1/p38 MAPK signaling pathway in OC in vitro and in vivo. TAB1 might be a pivotal target for reversing PTX resistance. This study will provide a theoretical basis for the combination of Tongguanteng injection and paclitaxel in clinic.

Novel Salinomycin-Based Paramagnetic Complexes-First Evaluation of Their Potential Theranostic Properties

Combining therapeutic with diagnostic agents (theranostics) can revolutionize the course of malignant diseases. Chemotherapy, hyperthermia, or radiation are used together with diagnostic methods such as magnetic resonance imaging (MRI). In contrast to conventional contrast agents (CAs), which only enable non-specific visualization of tissues and organs, the theranostic probe offers targeted diagnostic imaging and therapy simultaneously.

METHODS

Novel salinomycin (Sal)-based theranostic probes comprising two different paramagnetic metal ions, gadolinium(III) (Gd(III)) or manganese(II) (Mn(II)), as signal emitting motifs for MRI were synthesized and characterized by elemental analysis, infrared spectral analysis (IR), electroparamagnetic resonance (EPR), thermogravimetry (TG) differential scanning calorimetry (DSC) and electrospray ionization mass spectrometry (ESI-MS). To overcome the water insolubility of the two Sal-complexes, they were loaded into empty bacterial ghosts (BGs) cells as transport devices. The potential of the free and BGs-loaded metal complexes as theranostics was evaluated by in vitro relaxivity measurements in a high-field MR scanner and in cell culture studies.

RESULTS

Both the free Sal-complexes (Gd(III) salinomycinate (Sal-Gd(III) and Mn(II) salinomycinate (Sal-Mn(II)) and loaded into BGs demonstrated enhanced cytotoxic efficacy against three human tumor cell lines (A549, SW480, CH1/PA-1) relative to the free salinomycinic acid (Sal-H) and its sodium complex (Sal-Na) applied as controls with IC₅₀ in a submicromolar concentration range. Moreover, Sal-H, Sal-Gd(III), and Sal-Mn(II) were able to induce perturbations in the cell cycle of treated colorectal and breast human cancer cell lines (SW480 and MCF-7, respectively). The relaxivity (r₁) values of both complexes as well as of the loaded BGs, were higher or comparable to the relaxivity values of the clinically applied contrast agents gadopentetate dimeglumine and gadoteridol.

CONCLUSION

This research is the first assessment that demonstrates the potential of Gd(III) and Mn(II) complexes of Sal as theranostic agents for MRI. Due to the remarkable selectivity and mode of action of Sal as part of the compounds, they could revolutionize cancer therapy and allow for early diagnosis and monitoring of therapeutic follow-up.

Salinomycin alleviates osteoarthritis progression via inhibiting Wnt/β-catenin signaling

Osteoarthritis (OA) is the most prevalent degenerative whole-joint disease characterized by cartilage degeneration, synovial hyperplasia, osteophyte formation, and subchondral bone sclerosis. Currently there are no disease-modifying treatments available for OA because its etiology and pathogenesis are largely unknown. Here we report that a natural carboxylic polyether ionophore that is used as an anti-tumor drug, salinomycin (SAL), may be a promising therapeutic drug for OA in the future. We found that SAL showed no cytotoxicity on mouse chondrocytes and displayed a protective effect against interleukin-1β (IL-1β), in cultured mouse chondrocytes and cartilage explants. Treatment with low SAL concentrations directly upregulated the anabolism factors collagen II and aggrecan, while it inhibited the catabolic factors matrix metalloproteinase-13 (MMP13) and metalloproteinase with thrombospondin motifs-5 (ADAMTS5) to protect against extracellular matrix (ECM) degradation, and also suppressed inflammatory responses in mouse chondrocytes. Furthermore, SAL reduced the severity of OA-associated changes and delayed cartilage destruction, subchondral bone sclerosis, and osteophyte formation in a destabilized medial meniscus (DMM) surgery-induced mouse OA model. Mechanistically, a low SAL concentration induced anabolism and inhibited catabolism in chondrocytes via inhibiting Lrp6 phosphorylation and Wnt/β-catenin signaling. Our results suggested that SAL may serve as a potential disease-modifying therapeutic against OA pathogenesis.

Oncostatin M: From Intracellular Signaling to Therapeutic Targets in Liver Cancer

Primary liver cancers represent the third-most-common cause of cancer-related mortality worldwide, with an incidence of 80–90% for hepatocellular carcinoma (HCC) and 10–15% for cholangiocarcinoma (CCA), and an increasing morbidity and mortality rate. Although HCC and CCA originate from independent cell populations (hepatocytes and biliary epithelial cells, respectively), they develop in chronically inflamed livers. Evidence obtained in the last decade has revealed a role for cytokines of the IL-6 family in the development of primary liver cancers. These cytokines operate through the receptor subunit gp130 and the downstream Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathways. Oncostatin M (OSM), a member of the IL-6 family, plays a significant role in inflammation, autoimmunity, and cancer, including liver tumors. Although, in recent years, therapeutic approaches for the treatment of HCC and CCA have been implemented, limited treatment options with marginal clinical benefits are available. We discuss how OSM-related pathways can be selectively inhibited and therapeutically exploited for the treatment of liver malignancies.

Microbiota Communities of Healthy and Bacterial Pustule Diseased Soybean

Soybean is an important source of protein and for a wide range of agricultural, food, and industrial applications. Soybean is being affected by Xanthomonas citri pv. glycines, a causal pathogen of bacterial pustule disease, result in a reduction in yield and quality. Diverse microbial communities of plants are involved in various plant stresses is known. Therefore, we designed to investigate the microbial community differentiation depending on the infection of X. citri pv. glycines. The microbial community's abundance, diversity, and similarity showed a difference between infected and non-infected soybean. Microbiota community analysis, excluding X. citri pv. glycines, revealed that Pseudomonas spp. would increase the population of the infected soybean. Results of DESeq analyses suggested that energy metabolism, secondary metabolite, and TCA cycle metabolism were actively diverse in the non-infected soybeans. Additionally, Streptomyces bacillaris S8, an endophyte microbiota member, was nominated as a key microbe in the healthy soybeans. Genome analysis of S. bacillaris S8 presented that salinomycin may be the critical antibacterial metabolite. Our findings on the composition of soybean microbiota communities and the key strain information will contribute to developing biological control strategies against X. citri pv. glycines.

Evidence of Metallic and Polyether Ionophores as Potent Therapeutic Drug Candidate in Cancer Management

Cancer remains one of the most crucial human malignancies with a higher mortality rate globally, and is predicted to escalate soon. Dysregulated ion homeostasis in cancerous cells prompted the researchers to investigate further ion homeostasis impeding agents as potent anticancerous agents. Reutilization of FDA-approved non-cancerous drugs has emerged as a practical approach to developing potent, cost-effective drugs for cancer treatment. Across the globe, most nations are incapable of fulfilling the medical demands of cancer patients due to costlier cancerous drugs. Therefore, we have inclined our review towards emphasizing recent advancements in cancer therapies involving ionophores utilization in exploring potent anticancer drugs. Numerous research reports have established the significant anticancerous potential of ionophores in several pre-clinical reports via modulating aberrant cell signaling pathways and enhancing antitumor immunity in immune cells. This review has mainly summarized the most significant ion homeostasis impeding agents, including copper, zinc, calcium, and polyether, that presented remarkable potential in cancer therapeutics via enhanced antitumor immunity and apoptosis induction. Altogether, this study could provide a robust future perspective for developing cost-effective anticancerous drugs rapidly and cost-effectively, thereby combating the limitations of currently available drugs used in cancer treatment.

Interaction of crown ethers with the ABCG2 transporter and their implication for multidrug resistance reversal

Overexpression of ABC transporters, such as ABCB1 and ABCG2, plays an important role in mediating multidrug resistance (MDR) in cancer. This feature is also attributed to a subpopulation of cancer stem cells (CSCs), having enhanced tumourigenic potential. ABCG2 is specifically associated with the CSC phenotype, making it a valuable target for eliminating aggressive and resistant cells. Several natural and synthetic ionophores have been discovered as CSC-selective drugs that may also have MDR-reversing ability, whereas their interaction with ABCG2 has not yet been explored. We previously reported the biological activities, including ABCB1 inhibition, of a group of adamantane-substituted diaza-18-crown-6 (DAC) compounds that possess ionophore capabilities. In this study, we investigated the mechanism of ABCG2-inhibitory activity of DAC compounds and the natural ionophores salinomycin, monensin and nigericin. We used a series of functional assays, including real-time microscopic analysis of ABCG2-mediated fluorescent substrate transport in cells, and docking studies to provide comparative aspects for the transporter-compound interactions and their role in restoring chemosensitivity. We found that natural ionophores did not inhibit ABCG2, suggesting that their CSC selectivity is likely mediated by other mechanisms. In contrast, DACs with amide linkage in the side arms demonstrated noteworthy ABCG2-inhibitory activity, with DAC-3Amide proving to be the most potent. This compound induced conformational changes of the transporter and likely binds to both Cavity 1 and the NBD-TMD interface. DAC-3Amide reversed ABCG2-mediated MDR in model cells, without affecting ABCG2 expression or localization. These results pave the way for the development of new crown ether compounds with improved ABCG2-inhibitory properties.

Alkaline-earth metal(II) complexes of salinomycin – spectral properties and antibacterial activity

In the present paper the synthesis and structural characterization of alkaline-earth metal(II) complexes of the polyether ionophorous antibiotic salinomycinic acid (SalH.H2O) are discussed. The complexes [M(Sal)2(H2O)2] (M = Mg2+, 1; Ca2+, 2; Sr2+, 3; Ba2+, 4) were obtained reacting salinomycinic acid and Et4NOH with the corresponding metal(II) salts at metal-to-ligand-to-base molar ratio of 1:1:1. The spectral properties of 1–4 were characterized using infrared spectroscopy, fast atom bombardment-mass spectrometry, nuclear magnetic resonance and elemental analysis data. The crystallinity degree and morphology of complex 2 were studied by X-ray powder diffraction and transmission electron microscopy. The biometal(II) salinomycinate complexes 1 and 2 possess an enhanced antimicrobial activity compared to the parent antibiotic against Gram-positive bacteria. The comparison between the effectiveness of the complexes, reported here, and the already known isostructural coordination species of salinomycin and monensin (MonH.H2O), revealed that magnesium(II) and calcium(II) monensinates appear to be promising antibacterial agents against Bacillus subtilis, Bacillus cereus and Micrococcus luteus.

Drug Repurposing Strategies for Non-Cancer to Cancer Therapeutics

Global efforts invested for the prevention and treatment of cancer need to be repositioned to develop safe, effective, and economic anticancer therapeutics by adopting rational approaches of drug discovery. Drug repurposing is one of the established approaches to reposition old, clinically approved off patent noncancer drugs with known targets into newer indications. The literature review suggests key role of drug repurposing in the development of drugs intended for cancer as well as noncancer therapeutics. A wide category of noncancer drugs namely, drugs acting on CNS, anthelmintics, cardiovascular drugs, antimalarial drugs, anti-inflammatory drugs have come out with interesting outcomes during preclinical and clinical phases. In the present article a comprehensive overview of the current scenario of drug repurposing for the treatment of cancer has been focused. The details of some successful studies along with examples have been included followed by associated challenges.

Synergistic inhibition of the growth of MDA‑MB‑231 cells in triple‑negative breast cancer by salinomycin combined with 17‑AAG and its mechanism

Salinomycin (SAL), a typical ion carrier antibiotic, inhibits tumor growth and metastasis by inducing apoptosis or autophagy in cancer or cancer stem cells and thus overcomes drug resistance. 17-allylamino-17-demethoxygeldanamycin (17-AAG), a heat shock protein Hsp90 competitive inhibitor, also has a role in inhibiting tumor development. However, their combination on the growth of breast cancer cells and its specific mechanism remains to be elucidated. The present study tested the influence of SAL and 17-AAG on cell growth, apoptosis and autophagy by MTT assays, Annexin V-FITC and propidium iodide double staining assay and immunoelectron microscopy. The influence of SAL and 17-AAG on proteomics was investigated by isobaric tag for relative and absolute quantitation. It was found that SAL combined with 17-AAG synergistically inhibited the cell growth and induced the apoptosis in a concentration-dependent manner, with the expression of caspase 3 and Bcl-2 were decreased while the expression of Bax was increased. In addition, SAL combined with 17-AAG inhibited autophagy, with the expression of microtubule-associated protein 1 light chain 3, Beclin1, p62 being decreased. Mechanistically, SAL combined with 17-AAG synergistically inhibited the reactive oxygen species/JNK signaling pathway. In conclusion, SAL combined with 17-AAG had a synergistic inhibitory effect on cell growth of breast cancer via inducing apoptosis and inhibiting autophagy. The present study might provide a new strategy for potential clinical application of SAL as a new anti-tumor drug especially as a drug combination with other molecular targeting therapeutics.

A DFT/PCM Study on the Affinity of Salinomycin to Bind Monovalent Metal Cations

The affinity of the polyether ionophore salinomycin to bind IA/IB metal ions was accessed using the Gibbs free energy of the competition reaction between SalNa (taken as a reference) and its rival ions: [M+-solution] + [SalNa] → [SalM] + [Na+-solution] (M = Li, K, Rb, Cs, Cu, Ag, Au). The DFT/PCM computations revealed that the ionic radius, charge density and accepting ability of the competing metal cations, as well as the dielectric properties of the solvent, have an influence upon the selectivity of salinomycin. The optimized structures of the monovalent metal complexes demonstrate the flexibility of the ionophore, allowing the coordination of one or two water ligands in SalM-W1 and SalM-W2, respectively. The metal cations are responsible for the inner coordination sphere geometry, with coordination numbers spread between 2 (Au+), 4 (Li+ and Cu+), 5/6 (Na+, K+, Ag+), 6/7 (Rb+) and 7/8 (Cs+). The metals' affinity to salinomycin in low-polarity media follows the order of Li+ > Cu+ > Na+ > K+ > Au+ > Ag+ > Rb+ > Cs+, whereas some derangement takes place in high-dielectric environment: Li+ ≥ Na+ > K+ > Cu+ > Au+ > Ag+ > Rb+ > Cs+.

Salinomycin induces cell cycle arrest and apoptosis and modulates hepatic cytochrome P450 mRNA expression in HepG2/C3a cells

Salinomycin (SAL) is a monocarboxylic polyether ionophore antibiotic isolated from Streptomyces albus. It exhibits an effective antitumor potential against numerous human cancer cells. This study aimed to assess the antiproliferative effects of SAL in human hepatocellular carcinoma HepG2/C3a cell line. We investigated the effects of SAL on cell growth, DNA damage induction, cell cycle changes and apoptosis; and relative changes in expression of cell cycle-related, apoptosis-related, and CYP450 genes. SAL induced cell cycle arrest in the G2/M phase, upregulation of CDKN1A and GADD45A and downregulation of cyclin genes including CCNB1 and CCNA2. SAL effectively suppressed mRNA levels of CTNNB1 gene, an important oncogene that promotes tumorigenesis. The decrease of HepG2/C3A cells' survival can also be due to downregulation of antiapoptotic BCL-2 expression, thus promoting the induction of apoptosis by SAL. This study also demonstrated the ability of SAL in modulating hepatic cytochrome P450 (CYP) mRNA expression, such that SAL caused the upregulation of CYP1A members and CYP3A5; and downregulation of CYP3A4. Taken together, these data contribute to the understanding of the mechanism of action of SAL, highlighting that metabolizing enzymes modulated by SAL can interfere with chemotherapy treatment and it must be considered in associated treatments.

Synthetic and Naturally Occurring Heterocyclic Anticancer Compounds with Multiple Biological Targets

Cancer is a complex group of diseases initiated by abnormal cell division with the potential of spreading to other parts of the body. The advancement in the discoveries of omics and bio- and cheminformatics has led to the identification of drugs inhibiting putative targets including vascular endothelial growth factor (VEGF) family receptors, fibroblast growth factors (FGF), platelet derived growth factors (PDGF), epidermal growth factor (EGF), thymidine phosphorylase (TP), and neuropeptide Y4 (NY4), amongst others. Drug resistance, systemic toxicity, and drug ineffectiveness for various cancer chemo-treatments are widespread. Due to this, efficient therapeutic agents targeting two or more of the putative targets in different cancer cells are proposed as cutting edge treatments. Heterocyclic compounds, both synthetic and natural products, have, however, contributed immensely to chemotherapeutics for treatments of various diseases, but little is known about such compounds and their multimodal anticancer properties. A compendium of heterocyclic synthetic and natural product multitarget anticancer compounds, their IC50, and biological targets of inhibition are therefore presented in this review.

Single and double modified salinomycin analogs target stem-like cells in 2D and 3D breast cancer models

Breast cancer remains one of the leading cancers among women. Cancer stem cells (CSCs) are tumor-initiating cells which drive progression, metastasis, and reoccurrence of the disease. CSCs are resistant to conventional chemo- and radio-therapies and their ability to survive such treatment enables tumor reestablishment. Metastasis is the main cause of mortality in women with breast cancer, thus advances in treatment will depend on therapeutic strategies targeting CSCs. Salinomycin (SAL) is a naturally occurring polyether ionophore antibiotic known for its anticancer activity towards several types of tumor cells. In the present work, a library of 17 C1-single and C1/C20-double modified SAL analogs was screened to identify compounds with improved activity against breast CSCs. Six single- and two double-modified analogs were more potent (IC50 range of 1.1 ± 0.1-1.4 ± 0.2 µM) toward the breast cancer cell line MDA-MB-231 compared to SAL (IC50 of 4.9 ± 1.6 µM). Double-modified compound 17 was found to be more efficacious than SAL against the majority of cancer cell lines in the NCI-60 Human Tumor Cell Line Panel. Compound 17 was more potent than SAL in inhibiting cell migration and cell renewal properties of MDA-MB-231 cells, as well as inducing selective loss of the CD44+/CD24/low stem-cell-like subpopulation in both monolayer (2D) and organoid (3D) culture. The present findings highlight the therapeutic potential of SAL analogs towards breast CSCs and identify select compounds that merit further study and clinical development.

Anticancer Mechanisms of Salinomycin in Breast Cancer and Its Clinical Applications

Breast cancer (BC) is the most frequent cancer among women worldwide and is the leading cause of cancer-related deaths in women. Cancer cells with stem cell-like features and tumor-initiating potential contribute to drug resistance, tumor recurrence, and metastasis. To achieve better clinical outcomes, it is crucial to eradicate both bulk BC cells and breast cancer stem cells (BCSCs). Salinomycin, a monocarboxylic polyether antibiotic isolated from Streptomyces albus, can precisely kill cancer stem cells (CSCs), particularly BCSCs, by various mechanisms, including apoptosis, autophagy, and necrosis. There is increasing evidence that salinomycin can inhibit cell proliferation, invasion, and migration in BC and reverse the immune-inhibitory microenvironment to prevent tumor growth and metastasis. Therefore, salinomycin is a promising therapeutic drug for BC. In this review, we summarize established mechanisms by which salinomycin protects against BC and discuss its future clinical applications.

Salinomycin-Based Drug Delivery Systems: Overcoming the Hurdles in Cancer Therapy

Cancer stem cells (CSCs) are reportedly responsible for the initiation and propagation of cancer. Since CSCs are highly resistant to conventional chemo- and radiotherapy, they are considered the main cause of cancer relapse and metastasis. Salinomycin (Sali), an anticoccidial polyether antibiotic, has emerged as a promising new candidate for cancer therapy, with selective cytotoxicity against CSCs in various malignancies. Nanotechnology provides an efficient means of delivering Sali to tumors in view of reducing collateral damage to healthy tissues and enhancing the therapeutic outcome. This review offers an insight into the most recent advances in cancer therapy using Sali-based nanocarriers.

Tetracationic porphyrin derivatives against human breast cancer

Photodynamic therapy (PDT) is an approved therapeutic approach and an alternative to conventional chemotherapy for the treatment of several types of cancer with the advantages of reducing the side effects and developing resistance mechanisms. Here, was evaluated the photosensitization capabilities of 5,10,15,20-tetrakis[4-(pyridinium-1-yl-methyl)phenyl]porphyrin (3), its N-confused isomer (4) and of the neutral precursors (1) and (2) and the results were compared with the ones obtained with the cationic 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP). Both regular porphyrin derivatives 1 and 3 showed higher efficiency to generate singlet oxygen than TMPyP. The PDT assays towards MCF-7 cells under red light irradiation (λ > 640 nm, 23.7 mW cm^-2) demonstrated that the cationic porphyrin 3 is an efficient photosensitizer to kill MCF-7 breast cancer cells. The study of the cell death mechanisms induced by the photodynamic process showed that the studied porphyrin 3 and TMPyP caused cell death by autophagic flux and necrosis.

Salinomycin triggers prostate cancer cell apoptosis by inducing oxidative and endoplasmic reticulum stress via suppressing Nrf2 signaling

Salinomycin is a polyether antiprotozoal antibiotic that is widely used as an animal food additive. Some antifungal, antiparasitic, antiviral and anti-inflammatory activities have been reported for salinomycin. Recently, the anti-cancer effect of salinomycin has been demonstrated in breast cancer; however, the underlying mechanism remains unknown. The present study aimed to investigate the functional roles of salinomycin in the progression of prostate cancer cells using the DU145 and PC-3 cell lines. Western blotting and reverse transcription-quantitative polymerase chain reaction were performed to detect the expression of oxidative stress and endoplasmic reticulum stress-related molecules, and flow cytometry was performed to detect the apoptosis rate of DU145 and PC-3 cells after salinomycin treatment. The results demonstrated that salinomycin inhibited the viability and induced the apoptosis of PC-3 and DU145 cells in a dose-dependent manner. Furthermore, salinomycin increased the production of reactive oxygen species (ROS) and 8-hydroxy-2'-deoxyguanosine (8-OH-dG) and the lipid peroxidation. In addition, salinomycin induced the activation of unfolded protein response and endoplasmic reticulum stress in DU145 and PC-3 cells, as indicated by the elevated expression of binding immunoglobulin protein, activating transcription factor 4, phosphorylated eukaryotic initiation factor 2α, phosphorylated protein kinase RNA-like endoplasmic reticulum kinase and C/EBP homologous protein. In addition, salinomycin significantly downregulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1, NAD(P)H quinone dehydrogenase 1 and glutamate-cysteine ligase catalytic subunit and decreased the activity of the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase in PC-3 and DU145 cells. Furthermore, the Nrf2 activator, tert-butylhydroquinone, significantly reversed the therapeutic effects of salinomycin by stimulating the Nrf2 pathway and increasing the activity of antioxidant enzymes. Taken together, these findings demonstrated that salinomycin may trigger apoptosis by inducing oxidative and ER stress in prostate cancer cells via suppressing Nrf2 signaling.

Evaluation of Variances in VEGF-A-D and VEGFR-1-3 Expression in the Ishikawa Endometrial Cancer Cell Line Treated with Salinomycin and Anti-Angiogenic/Lymphangiogenic Effect

BACKGROUND

In cancer, an excessive and uncontrolled process of creating new blood and lymphatic vessels that play a key role in the metastasis process can be observed. The Vascular Endothelial Growth Factor (VEGF-A,-B,-C,-D) family together with their specific receptors (VEGFR-1,-2,- 3) plays a key role in these processes, therefore, it would be reasonable to determine the correct pattern of their expression.

OBJECTIVES

The study aimed to assess the use of salinomycin as an anti-angiogenic and anti-lymphangiogenic drug during endometrial cancer by examining changes in the expression pattern of VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGFR-1, VEGFR-2 and VEGFR-3 depending on the treatment period of the Ishikawa endometrial cancer cells with salinomycin in comparison to the control culture.

MATERIALS AND METHODS

To determine how influential salinomycin was on the expression of both mRNAs, 1 μM of the drug was added to the cell culture and then it was cultured all together for 12, 24 and 48 hour periods. The cells that made up the control culture were not treated with salinomycin. To determine the changes in the expression profile of the selected genes, we used the microarray, techniques: RTqPCR and ELISA (p<0.05).

RESULTS

For all isoforms of VEGF-A-D as well as receptors of VEGFR-1-3, a decrease in expression under the influence of salinomycin was noted. For VEGF-A and VEGFR-1, the difference in the expression between the culture treated with salinomycin in comparison to the control was statistically significant (p=0.0004). In turn, for VEGF-B, the difference between the culture exposed for 24 hours in comparison to the control (p=0.00000) as well as the comparison between H48 vs. C (p=0.00000) was statistically significant. In reference to VEGF-C, VEGFR-2 and VEGFR-3, the statistical analysis showed the significant difference in expression between the culture incubated with the drug for 12, 24 and 48 hours in comparison to the control as well as between the selected times. For all of these comparisons, p=0.00000 was utilized.

CONCLUSION

Salinomycin changes the expression pattern of VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGFR-1, VEGFR-2, and VEGFR-3 in endometrial cancer cells. The obtained results suggest that salinomycin might exert the effect via VEGF signaling pathways.

Combined Anticancer Effect of Plasma-Activated Infusion and Salinomycin by Targeting Autophagy and Mitochondrial Morphology

Non-thermal atmospheric pressure plasma (NTAPP)-activated liquids have emerged as new promising anticancer agents because they preferentially injure malignant cells. Here, we report plasma-activated infusion (PAI) as a novel NTAPP-based anti-neoplastic agent. PAI was prepared by irradiating helium NTAP to form a clinically approved infusion fluid. PAI dose-dependently killed malignant melanoma and osteosarcoma cell lines while showing much lower cytotoxic effects on dermal and lung fibroblasts. We found that PAI and salinomycin (Sal), an emerging anticancer stem cell agent, mutually operated as adjuvants. The combined administration of PAI and Sal was much more effective than single-agent application in reducing the growth and lung metastasis of osteosarcoma allografts with minimal adverse effects. Mechanistically, PAI explicitly induced necroptosis and increased the phosphorylation of receptor-interacting protein 1/3 rapidly and transiently. PAI also suppressed the ambient autophagic flux by activating the mammalian target of the rapamycin pathway. PAI increased the phosphorylation of Raptor, Rictor, and p70-S6 kinase, along with decreased LC3-I/II expression. In contrast, Sal promoted autophagy. Moreover, Sal exacerbated the mitochondrial network collapse caused by PAI, resulting in aberrant clustering of fragmented mitochondrial in a tumor-specific manner. Our findings suggest that combined administration of PAI and Sal is a promising approach for treating these apoptosis-resistant cancers.

Epithelial-mesenchymal transition sensitizes breast cancer cells to cell death via the fungus-derived sesterterpenoid ophiobolin A

The epithelial-mesenchymal transition (EMT) imparts properties of cancer stem-like cells, including resistance to frequently used chemotherapies, necessitating the identification of molecules that induce cell death specifically in stem-like cells with EMT properties. Herein, we demonstrate that breast cancer cells enriched for EMT features are more sensitive to cytotoxicity induced by ophiobolin A (OpA), a sesterterpenoid natural product. Using a model of experimentally induced EMT in human mammary epithelial (HMLE) cells, we show that EMT is both necessary and sufficient for OpA sensitivity. Moreover prolonged, sub-cytotoxic exposure to OpA is sufficient to suppress EMT-imparted CSC features including sphere formation and resistance to doxorubicin. In vivo growth of CSC-rich mammary cell tumors, is suppressed by OpA treatment. These data identify a driver of EMT-driven cytotoxicity with significant potential for use either in combination with standard chemotherapy or for tumors enriched for EMT features.

Bacteria as a treasure house of secondary metabolites with anticancer potential

Cancer stands in the frontline among leading killers worldwide and the annual mortality rate is expected to reach 16.4 million by 2040. Humans suffer from about 200 different types of cancers and many of them have a small number of approved therapeutic agents. Moreover, several types of major cancers are diagnosed at advanced stages as a result of which the existing therapies have limited efficacy against them and contribute to a dismal prognosis. Therefore, it is essential to develop novel potent anticancer agents to counteract cancer-driven lethality. Natural sources such as bacteria, plants, fungi, and marine microorganisms have been serving as an inexhaustible source of anticancer agents. Notably, over 13,000 natural compounds endowed with different pharmacological properties have been isolated from different bacterial sources. In the present article, we have discussed about the importance of natural products, with special emphasis on bacterial metabolites for cancer therapy. Subsequently, we have comprehensively discussed the various sources, mechanisms of action, toxicity issues, and off-target effects of clinically used anticancer drugs (such as actinomycin D, bleomycin, carfilzomib, doxorubicin, ixabepilone, mitomycin C, pentostatin, rapalogs, and romidepsin) that have been derived from different bacteria. Furthermore, we have also discussed some of the major secondary metabolites (antimycins, chartreusin, elsamicins, geldanamycin, monensin, plicamycin, prodigiosin, rebeccamycin, salinomycin, and salinosporamide) that are currently in the clinical trials or which have demonstrated potent anticancer activity in preclinical models. Besides, we have elaborated on the application of metagenomics in drug discovery and briefly described about anticancer agents (bryostatin 1 and ET-743) identified through the metagenomics approach.

Cancer Stem Cells and Neovascularization

Cancer stem cells (CSCs) refer to a subpopulation of cancer cells responsible for tumorigenesis, metastasis, and drug resistance. Increasing evidence suggests that CSC-associated tumor neovascularization partially contributes to the failure of cancer treatment. In this review, we discuss the roles of CSCs on tumor-associated angiogenesis via trans-differentiation or forming the capillary-like vasculogenic mimicry, as well as the roles of CSCs on facilitating endothelial cell-involved angiogenesis to support tumor progression and metastasis. Furthermore, we discuss the underlying regulation mechanisms, including the intrinsic signals of CSCs and the extrinsic signals such as cytokines from the tumor microenvironment. Further research is required to identify and verify some novel targets to develop efficient therapeutic approaches for more efficient cancer treatment through interfering CSC-mediated neovascularization.

Analysis of the Differences in the Expression of mRNAs and miRNAs Associated with Drug Resistance in Endometrial Cancer Cells Treated with Salinomycin

Background:

It is important to understand the molecular mechanisms involved in cancer drug resistance and to study the activity of new drugs, e.g. salinomycin.

Objective:

The purpose of the study was to analyze changes in the expression of genes associated with drug resistance in the Ishikawa endometrial cancer cell line when treated with salinomycin. In addition, changes in the level of miRNA potentially regulating these mRNAs were evaluated.

Materials and Methods:

Endometrial cancer cells were treated with 1 μM of salinomycin for 12, 24 and 48 hours periods. Untreated cells were a control culture. The molecular analysis consists of mRNA and miRNA microarray analysis and the RTqPCR technique.

Results:

The following was observed about the number of mRNAs differentiating the cell culture exposed to the drug compared to a control culture: H-12 vs. C - 9 mRNAs, H_24 vs. C - 6 mRNAs, and H_48 vs. C - 1 mRNA. It was noted that 4 of the 9 differentiating mRNAs were characteristic for 12 hours of exposure to salinomycin and they correspond to the following genes: TUFT1, ABCB1, MTMR11, and MX2. After 24 hours, 2 mRNAs were characteristic for this time of incubation cells with salinomycin: TUFT1 and MYD88 and after 48 hours, SLC30A5 could also be observed.

Discussion:

The highest differences in expression were indicated for TUFT1, MTMR11, and SLC30A5. The highest influence probability was determined between TUFT1 and hsa- miR-3188 (FC + 2.48), MTMR11and has-miR-16 (FC -1.74), and between SLC30A5 and hsa-miR-30d (FC -2.01).

Conclusions:

Salinomycin induces changes in the activity of mRNA and miRNA participating in drug resistance; however, the observed changes in character are the expected result of anti-cancer treatment.

Lipid nanocapsules co-encapsulating paclitaxel and salinomycin for eradicating breast cancer and cancer stem cells

Cancer stem cells (CSCs) comprise a diminutive population of the tumor but pose major obstacles in cancer treatment, often their presence being correlated with poor prognosis, therapeutic resistance and relapse. Nanocarriers of combined drugs regimes demonstrate improved pharmacokinetics and decreased systemic toxicity by targeting the bulk tumor cells along with CSCs, holding the key to future successful chemotherapy. Herein, we developed lipid nanocapsules (LNCs) with co-encapsulated paclitaxel (PTX) and salinomycin (SAL) to eliminate breast cancer cells (MCF-7; non-bCSCs) and cancer stem cells (bCSCs) respectively. LNCs loaded with either PTX or SAL alone or in combination were fabricated by the phase inversion temperature (PIT) method. Physicochemical properties such as nano-size (90 ± 5 nm) and spherical morphology of LNCs were confirmed by dynamic light scattering (DLS) and scanning electron microscopy (SEM) respectively. More than 98 % encapsulation efficiency of drug, alone or in combination, and their controlled drug release was obtained. Drug loaded LNCs were efficiently internalized and exhibited cytotoxicity in non-bCSCs and bCSCs, with dual drug loaded LNCs offering superior cytotoxicity and anti-bCSCs property. Drug loaded nanocapsules induced apoptosis in bCSCs, potentiated with the co-delivery of paclitaxel and salinomycin. Synergistic cytotoxic effect on both cells, non-bCSCs and bCSCs and effective reduction of the tumor mammospheres growth by co-encapsulated paclitaxel and salinomycin suggest LNCs to be promising for treatment of breast cancer.