Doxycycline inhibits the cancer stem cell phenotype and epithelial-to-mesenchymal transition in breast cancer

Navigating the therapeutic landscape for breast cancer: targeting breast cancer stem cells

Breast cancer is a common and deadly malignancy that affects women globally, and breast cancer stem cells (BCSCs) play an important role in tumorigenesis, development, metastasis, and recurrence. Traditional therapies often fail to eliminate BCSCs, leading to treatment resistance and relapse. This review explores the therapeutic strategies which are designed to target BCSCs, including inhibition of key signaling pathway and targeting receptor. This paper also explores the approaches to targeting BCSCs including chemotherapy, phytomedicines, and nanotechnology. Nanotechnology has gained a lot of importance in cancer therapy because of its ability to deliver therapeutic agents with more precision and minimal side effects. Various chemotherapeutic drugs, siRNAs, or gene editing tools are delivered efficiently with the use of nanocarriers which target pathways, receptors, and proteins associated with BCSCs. Over the past few years, stimuli-responsive and receptor-targeted nanocarriers have been explored for better therapeutic effects. In recent times, strategies such as chimeric antigen receptor (CAR) T-cell therapy, ablation therapy, and cell-free therapies are explored for targeting these stem cells. This review provides a recent developmental overview of strategies to attack BCSCs from conventional chemotherapeutic agents to nanotechnological platforms such as polymeric, lipidic, and metal-based nanoparticles and advanced technologies like CAR T cell therapies.

Doxycycline Restores Gemcitabine Sensitivity in Preclinical Models of Multidrug-Resistant Intrahepatic Cholangiocarcinoma

BACKGROUND/OBJECTIVES

Intrahepatic cholangiocarcinoma (iCCA) is a malignant liver tumor with a rising global incidence and poor prognosis, largely due to late-stage diagnosis and limited effective treatment options. Standard chemotherapy regimens, including cisplatin and gemcitabine, often fail because of the development of multidrug resistance (MDR), leaving patients with few alternative therapies. Doxycycline, a tetracycline antibiotic, has demonstrated antitumor effects across various cancers, influencing cancer cell viability, apoptosis, and stemness. Based on these properties, we investigated the potential of doxycycline to overcome gemcitabine resistance in iCCA.

METHODS

We evaluated the efficacy of doxycycline in two MDR iCCA cell lines, MT-CHC01R1.5 and 82.3, assessing cell cycle perturbation, apoptosis induction, and stem cell compartment impairment. We assessed the in vivo efficacy of combining doxycycline and gemcitabine in mouse xenograft models.

RESULTS

Treatment with doxycycline in both cell lines resulted in a significant reduction in cell viability (IC50 ~15 µg/mL) and induction of apoptosis. Doxycycline also diminished the cancer stem cell population, as indicated by reduced cholangiosphere formation. In vivo studies showed that while neither doxycycline nor gemcitabine alone significantly reduced tumor growth, their combination led to marked decreases in tumor volume and weight at the study endpoint. Additionally, metabolic analysis revealed that doxycycline reduced glucose uptake in tumors, both as a monotherapy and more effectively in combination with gemcitabine.

CONCLUSIONS

These findings suggest that doxycycline, especially in combination with gemcitabine, can restore chemotherapy sensitivity in MDR iCCA, providing a promising new strategy for improving outcomes in this challenging disease.

Role of Sam68 in different types of cancer (Review)

Src‑associated in mitosis 68 kDa protein (Sam68) is a protein encoded by the heteronuclear ribonucleoprotein particle K homology (KH) single domain‑containing, RNA‑binding, signal transduction‑associated protein 1 (known as KHDRBS1) gene in humans. This protein contains binding sites for critical components in a variety of cellular processes, including the regulation of gene expression, RNA processing and cell signaling. Thus, Sam68 may play a role in a variety of diseases, including cancer. Sam68 has been widely demonstrated to participate in tumor cell proliferation, progression and metastasis to be involved in the regulation of cancer stem cell self‑renewal. Based on the body of evidence available, Sam68 emerges as a promising target for this disease. The objectives of the present included summarizing the role of Sam68 in cancer murine models and cancer patients, unraveling the molecular mechanisms underlying its oncogenic potential and discussing the effectiveness of antitumor agents in reducing the malignant effects of Sam68 during tumorigenesis.

Synergistic Potential of Antibiotics with Cancer Treatments

Intratumoral microbiota, the diverse community of microorganisms residing within tumor tissues, represent an emerging and intriguing field in cancer biology. These microbial populations are distinct from the well-studied gut microbiota, offering novel insights into tumor biology, cancer progression, and potential therapeutic interventions. Recent studies have explored the use of certain antibiotics to modulate intratumoral microbiota and enhance the efficacy of cancer therapies, showing promising results. Antibiotics can alter intratumoral microbiota's composition, which may have a major role in promoting cancer progression and immune evasion. Certain bacteria within tumors can promote immunosuppression and resistance to therapies. By targeting these bacteria, antibiotics can help create a more favorable environment for chemotherapy, targeted therapy, and immunotherapy to act effectively. Some bacteria within the tumor microenvironment produce immunosuppressive molecules that inhibit the activity of immune cells. The combination of antibiotics and other cancer therapies holds significant promise for creating a synergistic effect and enhancing the immune response against cancer. In this review, we analyze several preclinical studies that have been conducted to demonstrate the synergy between antibiotics and other cancer therapies and discuss possible clinical implications.

Unraveling the Anti-Cancer Mechanisms of Antibiotics: Current Insights, Controversies, and Future Perspectives

Cancer persists as a significant global health challenge, claiming millions of lives annually despite remarkable strides in therapeutic innovation. Challenges such as drug resistance, toxicity, and suboptimal efficacy underscore the need for novel treatment paradigms. In this context, the repurposing of antibiotics as anti-cancer agents has emerged as an attractive prospect for investigation. Diverse classes of antibiotics have exhibited promising anti-cancer properties in both in vitro and in vivo studies. These mechanisms include the induction of apoptosis and cell cycle arrest, generation of reactive oxygen species, and inhibition of key regulators of cell proliferation and migration. Additional effects involve the disruption of angiogenesis and modulation of pivotal processes such as inflammation, immune response, mitochondrial dynamics, ferroptosis, and autophagy. Furthermore, antibiotics have demonstrated the potential to enhance the efficacy of conventional modalities like chemotherapy and radiotherapy, while alleviating treatment-induced toxicities. Nevertheless, the integration of antibiotics into oncological applications remains contentious, with concerns centered on their disruption of gut microbiota, interference with immunotherapeutic strategies, contribution to microbial resistance, and potential association with tumorigenesis. This narrative review explores the mechanisms of antibiotics' anti-cancer activity, addresses controversies about their dual role in cancer biology, and envisions future perspectives that include the development of novel derivatives and innovative frameworks for their incorporation into cancer treatment paradigms.

Constructing a doxycycline-inducible system for an epithelial-to-mesenchymal transition model in MCF10A cells

Epithelial to mesenchymal transition (EMT) has been shown to play an essential role in the early stages of cancer cell invasion and metastasis. Inducible EMT models can initiate EMT in a controlled manner, thereby providing the opportunity to determine whether a cancer-associated gene influences cancer metastasis by triggering EMT. Moreover, different inducible EMT models enable the investigation of specific mechanisms of EMT modulation by various genes, facilitating a more precise understanding of how these genes influence cancer metastasis through the induction of EMT. Unfortunately, current inducible EMT models still present unmet needs. Therefore, we aimed to establish an inducible EMT model in MCF10A cells, a spontaneously immortalized human fibrocystic mammary cell line, by manipulating the expression of mouse Twist1 (mTwist1). In this study, we first compared the EMT induction capacity between human TWIST1 (hTWIST1) and mTwist1, and selected mTwist1 for further investigation. By monitoring the changes in epithelial and mesenchymal markers at different induction time points, we examined the EMT process in both polyclonal and monoclonal MCF10A cells that express doxycycline (DOX)-inducible mTwist1. Furthermore, our results showed that doxycycline-induced mTwist1 expression triggered EMT at a similar rate to TGFβ1-induced EMT in MCF10A cells. Additionally, this process was reversible upon DOX withdrawal. Thus, we have established a robust inducible EMT model in MCF10A cells, which can be used to further study cancer metastasis-driving genes.

Harnessing Drug Repurposing to Combat Breast Cancer by Targeting Altered Metabolism and Epithelial-to-Mesenchymal Transition Pathways

Breast cancer remains one of the most prevalent and challenging cancers to treat due to its complexity and heterogenicity. Cellular processes such as metabolic reprogramming and epithelial-to-mesenchymal transition (EMT) contribute to the complexity of breast cancer by driving uncontrolled cell division, metastasis, and resistance to therapies. Strategically targeting these intricate pathways can effectively impede breast cancer progression, thereby revealing significant potential for therapeutic interventions. Among various emerging therapeutic approaches, drug repurposing offers a promising avenue for enhancing clinical outcomes. In recent years, high-throughput screening, QSAR, and network pharmacology have been widely employed to identify promising repurposed drugs. As an outcome, several drugs, such as Metformin, Itraconazole, Pimozide, and Disulfiram, were repurposed to regulate metabolic and EMT pathways. Moreover, strategies such as combination therapy, targeted delivery, and personalized medicine were utilized to enhance the efficacy and specificity of the repurposed drugs. This review focuses on the potential of targeting altered metabolism and EMT in breast cancer through drug repurposing. It also highlights recent advancements in drug screening techniques, associated limitations, and strategies to overcome these challenges.

The superiority of PMFs on reversing drug resistance of colon cancer and the effect on aerobic glycolysis-ROS-autophagy signaling axis

Background

Polymethoxylated flavones (PMFs) are compounds present in citrus peels and other Rutaceae plants, which exhibit diverse biological activities, including robust antitumor and antioxidant effects. However, the mechanism of PMFs in reversing drug resistance to colon cancer remains unknown. In the present study, we aimed to investigate the potential connection between the aerobic glycolysis-ROS-autophagy signaling axis and the reversal of PTX resistance in colon cancer by PMFs.

Methods

MTT Cell viability assay and colony formation assay were used to investigate the effect of PMFs combined with PTX in reversing HCT8/T cell resistance ex vivo; the mRNA and protein levels of the target were detected by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis), quantitative real-time fluorescence polymerase chain reaction (qRT-PCR) and Western blot protein immunoblotting (WB); An HCT8/T cell xenograft model was established to investigate the MDR reversal activity of PMFs in vivo; The extracellular acidification rate (ECAR) and the oxygen consumption rate (OCR) were detected to assess the cellular oxygen consumption rate and glycolytic process.

Results

HCT8/T cells demonstrated significant resistance to PTX, up-regulating the expression levels of ABCB1 mRNA, P-gp, LC3-I, and LC3-II protein, and increasing intracellular reactive oxygen species (ROS) content. PMFs mainly contain two active ingredients, nobiletin, and tangeretin, which were able to reverse drug resistance in HCT8/T cells in a concentration-dependent manner. PMFs exhibited high tolerance in the HCT8/T nude mouse model while increasing the sensitivity of PTX-resistant cells and suppressing tumor growth significantly. PMFs combined with PTX reduced extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) in HCT8/T cells. Additionally, PMFs reduced intracellular ROS content, down-regulated the expression levels of autophagy-related proteins LC3-I, LC3-II, Beclin1, and ATG7, and significantly reduced the number of autophagosomes in HCT8/T cells.

Conclusions

The present study demonstrated that PMFs could potentially reverse PTX resistance in colon cancer by regulating the aerobic glycolysis-ROS-autophagy signaling axis, which indicated that PMFs would be potential potentiators for future chemotherapeutic agents in colon cancer.

Systematic review on the role of the gut microbiota in tumors and their treatment

Tumors present a formidable health risk with limited curability and high mortality; existing treatments face challenges in addressing the unique tumor microenvironment (hypoxia, low pH, and high permeability), necessitating the development of new therapeutic approaches. Under certain circumstances, certain bacteria, especially anaerobes or parthenogenetic anaerobes, accumulate and proliferate in the tumor environment. This phenomenon activates a series of responses in the body that ultimately produce anti-tumor effects. These bacteria can target and colonize the tumor microenvironment, promoting responses aimed at targeting and fighting tumor cells. Understanding and exploiting such interactions holds promise for innovative therapeutic strategies, potentially augmenting existing treatments and contributing to the development of more effective and targeted approaches to fighting tumors. This paper reviews the tumor-promoting mechanisms and anti-tumor effects of the digestive tract microbiome and describes bacterial therapeutic strategies for tumors, including natural and engineered anti-tumor strategies.

Design, Synthesis, and Evaluation of a Novel Conjugate Molecule with Dopaminergic and Neuroprotective Activities for Parkinson's Disease

The escalating prevalence of Parkinson's disease (PD) underscores the need for innovative therapeutic interventions since current palliative measures, including the standard l-Dopa formulations, face challenges of tolerance and side effects while failing to address the underlying neurodegenerative processes. Here, we introduce DAD9, a novel conjugate molecule that aims to combine symptomatic relief with disease-modifying strategies for PD. Crafted through knowledge-guided chemistry, the molecule combines a nonantibiotic doxycycline derivative with dopamine, preserving neuroprotective attributes while maintaining dopaminergic agonism. This compound exhibited no off-target effects on PD-relevant cell functions and sustained antioxidant and anti-inflammatory properties of the tetracycline precursor. Furthermore, it effectively interfered with the formation and seeding of toxic α-synuclein aggregates without producing detrimental oxidative species. In addition, DAD9 was able to activate dopamine receptors, and docking simulations shed light onto the molecular details of this interaction. These findings position DAD9 as a potential neuroprotective dopaminergic agonist, promising advancements in PD therapeutics.

Novel Anti-Cancer Stem Cell Compounds: A Comprehensive Review

Cancer stem cells (CSCs) possess a significant ability to renew themselves, which gives them a strong capacity to form tumors and expand to encompass additional body areas. In addition, they possess inherent resistance to chemotherapy and radiation therapies used to treat many forms of cancer. Scientists have focused on investigating the signaling pathways that are highly linked to the ability of CSCs to renew themselves and maintain their stem cell properties. The pathways encompassed are Notch, Wnt/β-catenin, hedgehog, STAT3, NF-κB, PI-3K/Akt/mTOR, sirtuin, ALDH, MDM2, and ROS. Recent studies indicate that directing efforts towards CSC cells is essential in eradicating the overall cancer cell population and reducing the likelihood of tumor metastasis. As our comprehension of the mechanisms that stimulate CSC activity, growth, and resistance to chemotherapy advances, the discovery of therapeutic drugs specifically targeting CSCs, such as small-molecule compounds, holds the potential to revolutionize cancer therapy. This review article examines and analyzes the novel anti-CSC compounds that have demonstrated effective and selective targeting of pathways associated with the renewal and stemness of CSCs. We also discussed their special drug metabolism and absorption mechanisms. CSCs have been the subject of much study in cancer biology. As a possible treatment for malignancies, small-molecule drugs that target CSCs are gaining more and more attention. This article provides a comprehensive review of the current state of key small-molecule compounds, summarizes their recent developments, and anticipates the future discovery of even more potent and targeted compounds, opening up new avenues for cancer treatment.

A doxycycline-loaded microfiber of poly-metformin/PCL for eradicating melanoma stem cells

Nowadays, electrospun fibrous mats are used as drug delivery systems for loading of potential drugs in order to kill cancer cells. In the study, a skin patch for treating melanoma cancer after surgery was made using polycaprolactone and polymetformin microfibers that were loaded with doxycycline (PolyMet/PCL@DOX), an anti-cancer stem cell agent. The morphology, structure, mechanical characteristics, swelling, and porosity of the electrospun microfibers were examined. Drug release andanticancereffectiveness of PolyMet/PCL@DOXwas evaluated against A375 melanoma cancer stem cells using the MTS, Flow cytometry, colony formation and CD44 expression assays. Scanning electron microscopy (SEM) verified the micro fibrous structure with a diameter of about 2.31 µm. The porosity and swelling percentages for microfibers was 73.5 % and 2.9 %, respectively. The tensile strength at the breaking point was equal to 3.84 MPa. The IC50 of PolyMet/PCL@DOX was 7.4 μg/mL. The survival rate of A375 cells after 72 h of PolyMet/PCL@DOX treatment was 43.9 %. The colony formation capacity of A375 cells decreased after PolyMet/PCL@DOX treatment. The level of CD44 expression in the PolyMet/PCL@DOX group decreased compared to the control group. Generally, PolyMet/PCL@DOX microfibers can be a promising candidate as a patch after surgery to eradicate cancer stem cells, effectively.

Drug Repurposing of Selected Antibiotics: An Emerging Approach in Cancer Drug Discovery

Drug repurposing is a method of investigating new therapeutic applications for previously approved medications. This repurposing approach to "old" medications is now highly efficient, simple to arrange, and cost-effective and poses little risk of failure in treating a variety of disorders, including cancer. Drug repurposing for cancer therapy is currently a key topic of study. It is a way of exploring recent therapeutic applications for already-existing drugs. Theoretically, the repurposing strategy has various advantages over the recognized challenges of creating new molecular entities, including being faster, safer, easier, and less expensive. In the real world, several medications have been repurposed, including aspirin, metformin, and chloroquine. However, doctors and scientists address numerous challenges when repurposing drugs, such as the fact that most drugs are not cost-effective and are resistant to bacteria. So the goal of this review is to gather information regarding repurposing pharmaceuticals to make them more cost-effective and harder for bacteria to resist. Cancer patients are more susceptible to bacterial infections. Due to their weak immune systems, antibiotics help protect them from a variety of infectious diseases. Although antibiotics are not immune boosters, they do benefit the defense system by killing bacteria and slowing the growth of cancer cells. Their use also increases the therapeutic efficacy and helps avoid recurrence. Of late, antibiotics have been repurposed as potent anticancer agents because of the evolutionary relationship between the prokaryotic genome and mitochondrial DNA of eukaryotes. Anticancer antibiotics that prevent cancer cells from growing by interfering with their DNA and blocking growth of promoters, which include anthracyclines, daunorubicin, epirubicin, mitoxantrone, doxorubicin, and idarubicin, are another type of FDA-approved antibiotics used to treat cancer. According to the endosymbiotic hypothesis, prokaryotes and eukaryotes are thought to have an evolutionary relationship. Hence, in this study, we are trying to explore antibiotics that are necessary for treating diseases, including cancer, helping people reduce deaths associated with various infections, and substantially extending people's life expectancy and quality of life.

Modification of the Antibiotic, Colistin, with Dextrin Causes Enhanced Cytotoxicity and Triggers Apoptosis in Myeloid Leukemia

Introduction

Acute myeloid leukemia (AML) remains difficult to treat due to its heterogeneity in molecular landscape, epigenetics and cell signaling alterations. Precision medicine is a major goal in AML therapy towards developing agents that can be used to treat patients with different 'subtypes' in combination with current chemotherapies. We have previously developed dextrin-colistin conjugates to combat the rise in multi-drug resistant bacterial infections and overcome dose-limiting nephrotoxicity. Recent evidence of colistin's anticancer activity, mediated through inhibition of intracellular lysine-specific histone demethylase 1 (LSD1/KDM1A), suggests that dextrin-colistin conjugates could be used to treat cancer cells, including AML. This study aimed to evaluate whether dextrin conjugation (which reduces in vivo toxicity and prolongs plasma half-life) could enhance colistin's cytotoxic effects in myeloid leukemia cell lines and compare the intracellular uptake and localization of the free and conjugated antibiotic.

Results

Our results identified a conjugate (containing 8000 g/mol dextrin with 1 mol% succinoylation) that caused significantly increased toxicity in myeloid leukemia cells, compared to free colistin. Dextrin conjugation altered the mechanism of cell death by colistin, from necrosis to caspase 3/7-dependent apoptosis. In contrast, conjugation via a reversible ester linker, instead of an amide, had no effect on the mechanism of the colistin-induced cell death. Live cell confocal microscopy of fluorescently labelled compounds showed both free and dextrin-conjugated colistins were endocytosed and co-localized in lysosomes, and increasing the degree of modification by succinoylation of dextrin significantly reduced colistin internalization.

Discussion

Whilst clinical translation of dextrin-colistin conjugates for the treatment of AML is unlikely due to the potential to promote antimicrobial resistance (AMR) and the relatively high colistin concentrations required for anticancer activity, the ability to potentiate the effectiveness of an anticancer drug by polymer conjugation, while reducing side effects and improving biodistribution of the drug, is very attractive, and this approach warrants further investigation.

Breast Tumor Metastasis and Its Microenvironment: It Takes Both Seed and Soil to Grow a Tumor and Target It for Treatment

Metastasis remains a major challenge in treating breast cancer. Breast tumors metastasize to organ-specific locations such as the brain, lungs, and bone, but why some organs are favored over others remains unclear. Breast tumors also show heterogeneity, plasticity, and distinct microenvironments. This contributes to treatment failure and relapse. The interaction of breast cancer cells with their metastatic microenvironment has led to the concept that primary breast cancer cells act as seeds, whereas the metastatic tissue microenvironment (TME) is the soil. Improving our understanding of this interaction could lead to better treatment strategies for metastatic breast cancer. Targeted treatments for different subtypes of breast cancers have improved overall patient survival, even with metastasis. However, these targeted treatments are based upon the biology of the primary tumor and often these patients' relapse, after therapy, with metastatic tumors. The advent of immunotherapy allowed the immune system to target metastatic tumors. Unfortunately, immunotherapy has not been as effective in metastatic breast cancer relative to other cancers with metastases, such as melanoma. This review will describe the heterogeneic nature of breast cancer cells and their microenvironments. The distinct properties of metastatic breast cancer cells and their microenvironments that allow interactions, especially in bone and brain metastasis, will also be described. Finally, we will review immunotherapy approaches to treat metastatic breast tumors and discuss future therapeutic approaches to improve treatments for metastatic breast cancer.

PGC1-α-driven mitochondrial biogenesis contributes to a cancer stem cell phenotype in melanoma

Little is known about the metabolic regulation of cancer stem cells (CSCs) in melanoma. Here, we used A375 and WM115 cell lines to dissect the role of mitochondria in conferring CSC traits. Notably, we observed that A375 and WM115 melanospheres, known to be enriched in ABCG2+ CSCs, showed higher mitochondrial mass compared with their adherent counterpart. In particular, they displayed increased PGC1-α expression and oxidative phosphorylation (OXPHOS) complex levels, leading to a metabolic switch characterized by enhanced mitochondrial membrane potential, oxygen consumption, ATP synthesis and ROS production. Interestingly, PGC1-α silencing resulted in the suppression of CSC features, including clonogenic ability, migration, spheroid formation and ABCG2 enrichment. Similarly, XCT790 and SR-18292, two PGC1-α inhibitors, were able not only to reduce melanoma tumorigenicity and invasion but also to block melanosphere growth and propagation and ABCG2+ cell proliferation. In conclusion, improved mitochondrial biogenesis is associated with a stem-like phenotype in melanoma, and therapeutically targeting the mitochondria-enriched CSC subpopulation might overcome tumor progression.

Drug repurposing: A novel strategy to target cancer stem cells and therapeutic resistance

Chemotherapy is an effortless and frequently used approach in cancer therapy. However, in most cases, it can only prolong life expectancy and does not guarantee a complete cure. Furthermore, chemotherapy is associated with severe adverse effects, one of the major complications of effective cancer therapy. In addition, newly published research outputs show that cancer stem cells are involved in cancer disease progression, drug resistance, metastasis, and recurrence and that they are functional in the trans-differentiation capacity of cancer stem cells to cancer cells in response to treatments. Novel strategies are therefore required for better management of cancer therapy. The prime approach would be to synthesize and develop novel drugs that need extensive resources, time, and endurance to be brought into therapeutic use. The subsequent approach would be to screen the anti-cancer activity of available non-cancerous drugs. This concept of repurposing non-cancer drugs as an alternative to current cancer therapy has become popular in recent years because using existing anticancer drugs has several adverse effects. Micronutrients have also been investigated for cancer therapy due to their significant anti-cancer effects with negligible or no side effects and availability in food sources. In this paper, we discuss an ideal hypothesis for screening available non-cancerous drugs with anticancer activity, with a focus on cancer stem cells and their clinical application for cancer treatment. Further, drug repurposing and the combination of micronutrients that can target both cancers and cancer stem cells may result in a better therapeutic approach leading to maximum tumor growth control.

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.

Tetracycline antibiotics: Potential anticancer drugs

In recent years, research on tetracycline antibiotics has gradually shifted from their antibacterial effects to anticancer effects. Doxycycline, minocycline, and tigecycline as the US Food and Drug Administration (FDA) approved tetracycline antibiotics have been the main subjects of studies. Evidence indicated that they have anticancer properties and are able to control cancer progression through different mechanisms, such as anti-proliferation, anti-metastasis, and promotion of autophagy or apoptosis. In addition, studies have shown that these three tetracycline antibiotics can be utilized in conjunction with chemotherapeutic and targeted drugs to inhibit cancer progression and improve the quality of patient survival. Therefore, doxycycline, minocycline, and tigecycline are taken as examples in this work. Their mechanisms of action in different cancers and related combination therapies are introduced. Their current roles in alleviating the suffering of patients undergoing chemotherapy when used as adjuvant drugs in clinical treatment are also described. Finally, the research gaps and potential research directions at this stage are briefly summarized.

Unlocking therapeutic potential: integration of drug repurposing and immunotherapy for various disease targeting

Drug repurposing, also known as drug repositioning, entails the application of pre-approved or formerly assessed drugs having potentially functional therapeutic amalgams for curing various disorders or disease conditions distinctive from their original remedial indication. It has surfaced as a substitute for the development of drugs for treating cancer, cardiovascular diseases, neurodegenerative disorders, and various infectious diseases like Covid-19. Although the earlier lines of findings in this area were serendipitous, recent advancements are based on patient centered approaches following systematic, translational, drug targeting practices that explore pathophysiological ailment mechanisms. The presence of definite information and numerous records with respect to beneficial properties, harmfulness, and pharmacologic characteristics of repurposed drugs increase the chances of approval in the clinical trial stages. The last few years have showcased the successful emergence of repurposed drug immunotherapy in treating various diseases. In this light, the present review emphasises on incorporation of drug repositioning with Immunotherapy targeted for several disorders.

Autophagy and Breast Cancer: Connected in Growth, Progression, and Therapy

Despite an increase in the incidence of breast cancer worldwide, overall prognosis has been consistently improving owing to the development of multiple targeted therapies and novel combination regimens including endocrine therapies, aromatase inhibitors, Her2-targeted therapies, and cdk4/6 inhibitors. Immunotherapy is also being actively examined for some breast cancer subtypes. This overall positive outlook is marred by the development of resistance or reduced efficacy of the drug combinations, but the underlying mechanisms are somewhat unclear. It is interesting to note that cancer cells quickly adapt and evade most therapies by activating autophagy, a catabolic process designed to recycle damaged cellular components and provide energy. In this review, we discuss the role of autophagy and autophagy-associated proteins in breast cancer growth, drug sensitivity, tumor dormancy, stemness, and recurrence. We further explore how autophagy intersects and reduces the efficacy of endocrine therapies, targeted therapies, radiotherapy, chemotherapies as well as immunotherapy via modulating various intermediate proteins, miRs, and lncRNAs. Lastly, the potential application of autophagy inhibitors and bioactive molecules to improve the anticancer effects of drugs by circumventing the cytoprotective autophagy is discussed.

Targeting Mitochondria with ClpP Agonists as a Novel Therapeutic Opportunity in Breast Cancer

Breast cancer is the most frequently diagnosed malignancy worldwide and the leading cause of cancer mortality in women. Despite the recent development of new therapeutics including targeted therapies and immunotherapy, triple-negative breast cancer remains an aggressive form of breast cancer, and thus improved treatments are needed. In recent decades, it has become increasingly clear that breast cancers harbor metabolic plasticity that is controlled by mitochondria. A myriad of studies provide evidence that mitochondria are essential to breast cancer progression. Mitochondria in breast cancers are widely reprogrammed to enhance energy production and biosynthesis of macromolecules required for tumor growth. In this review, we will discuss the current understanding of mitochondrial roles in breast cancers and elucidate why mitochondria are a rational therapeutic target. We will then outline the status of the use of mitochondria-targeting drugs in breast cancers, and highlight ClpP agonists as emerging mitochondria-targeting drugs with a unique mechanism of action. We also illustrate possible drug combination strategies and challenges in the future breast cancer clinic.

A metabolism targeting three-pronged attack significantly attenuates breast cancer stem cell related markers toward therapeutic application

Tumor metabolism has provided researchers with a promising window to cancer therapy. The metabolic pathways adopted by cancer cells are different from those of normal cells. Thus, metabolism can be considered a linchpin in targeted cancer therapy. Glycolysis, pentose phosphate pathway, and mitochondria represent three critical metabolic spots with important roles in cancer cell survival and proliferation. In the present study, we aimed to target these pathways using three different inhibitors: 2-deoxyglucose, 6-aminonicotinamide, and doxycycline, separately and in combination. Accordingly, cell viability, lactate production, cell cycle profile, apoptotic profile, and expression of surface and molecular markers of MCF-7 and MDA-MB-231 breast cancer cell lines were investigated under adherent and sphere conditions. Our results from our set conditions indicated various inhibitory effects of these compounds on the breast cancer cell lines. Based on this all-around attack, the combination of drugs demonstrated the most effective inhibitory action compared to separate usage. This study suggests the combined application of these drugs in future investigations and more experimental settings in order to introduce this therapeutic strategy as an efficient anti-cancer treatment.

Genetic heterogeneity of colorectal cancer and the microbiome

In 2020, the International Agency for Research on Cancer and the World Health Organization's GLOBOCAN database ranked colorectal cancer (CRC) as the third most common cancer in the world. Most cases of CRC (> 95%) are sporadic and develop from colorectal polyps that can progress to intramucosal carcinoma and CRC. Increasing evidence is accumulating that the gut microbiota can play a key role in the initiation and progression of CRC, as well as in the treatment of CRC, acting as an important metabolic and immunological regulator. Factors that may determine the microbiota role in CRC carcinogenesis include inflammation, changes in intestinal stem cell function, impact of bacterial metabolites on gut mucosa, accumulation of genetic mutations and other factors. In this review, I discuss the major mechanisms of the development of sporadic CRC, provide detailed characteristics of the bacteria that are most often associated with CRC, and analyze the role of the microbiome and microbial metabolites in inflammation initiation, activation of proliferative activity in intestinal epithelial and stem cells, and the development of genetic and epigenetic changes in CRC. I consider long-term studies in this direction to be very important, as they open up new opportunities for the treatment and prevention of CRC.

Doxycycline-Induced Changes in Circulating MMP or TIMP2 Levels Are Not Associated with Skeletal-Related Event-Free or Overall Survival in Patients with Bone Metastases from Breast Cancer

Doxycycline is often used as a promoter of inducible gene expression in preclinical models; however, it can also have direct effects on tumor growth and survival. This is due in part to its ability to inhibit cell invasion and regulate matrix metalloproteinase (MMP) expression. Given that doxycycline is also osteotropic, a clinical study to assess its effects on modulation of tumor progression or prevention of skeletal-related events (SRE) in patients with bone metastases from breast cancer (the Achilles trial) was undertaken. Patients received 100 mg of oral doxycycline twice daily for 12 weeks, with serum obtained at baseline and 4, 8 and 12 weeks post-initiation of doxycycline treatment. Exploratory analysis of the effects of doxycycline on circulating levels of MMP or tissue inhibitor of matrix metalloproteinase 2 (TIMP2) was performed in enrolled patients. Statistically significant associations were observed between MMP2, MMP9 and TIMP2 at baseline with significant associations maintained between absolute levels and changes in levels of MMP2 and TIMP2 at weeks 4-12 post initiation of doxycycline. Treatment with doxycycline generally resulted in decreases in MMP2 and MMP9 levels with concurrent upregulation of TIMP2 at 12 weeks post-initiation of doxycycline treatment. Despite this, we observed no association with the levels of any of these factors with either SRE-free or overall survival in this patient cohort. In summary, despite observing hypothesized effects of doxycycline administration on surrogate markers of its anti-tumor activity, measures of circulating levels of these biomarkers were not prognostic in this patient population.

The Role of Cancer Stem Cells and Their Extracellular Vesicles in the Modulation of the Antitumor Immunity

Cancer stem cells (CSCs) are a population of tumor cells that share similar properties to normal stem cells. CSCs are able to promote tumor progression and recurrence due to their resistance to chemotherapy and ability to stimulate angiogenesis and differentiate into non-CSCs. Cancer stem cells can also create a significant immunosuppressive environment around themselves by suppressing the activity of effector immune cells and recruiting cells that support tumor escape from immune response. The immunosuppressive effect of CSCs can be mediated by receptors located on their surface, as well as by secreted molecules, which transfer immunosuppressive signals to the cells of tumor microenvironment. In this article, the ability of CSCs to regulate the antitumor immune response and a contribution of CSC-derived EVs into the avoidance of the immune response are discussed.

Doxycycline Hydrochloride Regulates Cytoskeletal Rearrangement and Epithelial-To-Mesenchymal Transition in Malignant Rhabdoid Tumour of the Kidney

Objective. As a highly malignant tumour, malignant rhabdoid tumours of the kidney (MRTK) are prone to metastasis and invasion, while tumour metastasis and invasion are inseparable from matrix metalloproteinases (MMPs) and epithelial-mesenchymal transformation (EMT). Moreover, the key to EMT is remodelling of the cytoskeleton. Therefore, our study is aimed at investigating whether doxycycline hydrochloride (DCH), an inhibitor of MMPs, could reverse EMT in MRTK to exert an antitumour effect by regulating MMPs and the cytoskeleton. Methods. The existence of EMT in MRTK cells was verified by bioinformatics analysis, immunofluorescence, and western blotting (WB). In vitro, the proliferation, migration, and invasion abilities of G401 cells were examined by Cell Counting Kit-8 (CCK-8), scratch, and Transwell assays, respectively. The effect of DCH on tumour growth in tumour-bearing mice was explored in in vivo experiments, and the expression of MMP2 and MMP9 and EMT correlation indexes was measured by immunofluorescence and WB, and the changes in cytoskeletal F-actin and β-tubulin were measured by fluorescence. Results. The altered extracellular matrix (ECM) composition, EMT, and high expression of MMP2 and MMP9 existed in MRTK. DCH inhibited the proliferation, migration, and invasion of G401 cells in vitro. In vivo, DCH inhibited tumour growth in mice, downregulated the expression of MMP2 and MMP9, and partially reversed EMT. Alternatively, DCH resulted in cytoskeletal rearrangements of G401 cells. Conclusions. DCH, as an MMP inhibitor, is used for the first time in MRTK research, showing good antitumour effects by reversing EMT and potentially providing new therapeutic measures for MRTK treatment.

Overcoming therapeutic resistance to platinum-based drugs by targeting Epithelial–Mesenchymal transition

Platinum-based drugs (PBDs), including cisplatin, carboplatin, and oxaliplatin, have been widely used in clinical practice as mainstay treatments for various types of cancer. Although there is firm evidence of notable achievements with PBDs in the management of cancers, the acquisition of resistance to these agents is still a major challenge to efforts at cure. The introduction of the epithelial-mesenchymal transition (EMT) concept, a critical process during embryonic morphogenesis and carcinoma progression, has offered a mechanistic explanation for the phenotypic switch of cancer cells upon PBD exposure. Accumulating evidence has suggested that carcinoma cells can enter a resistant state via induction of the EMT. In this review, we discussed the underlying mechanism of PBD-induced EMT and the current understanding of its role in cancer drug resistance, with emphasis on how this novel knowledge can be exploited to overcome PBD resistance via EMT-targeted compounds, especially those under clinical trials.

Drug repurposing-an emerging strategy in cancer therapeutics

Cancer is a complex disease affecting millions of people around the world. Despite advances in surgical and radiation therapy, chemotherapy continues to be an important therapeutic option for the treatment of cancer. The current treatment is expensive and has several side effects. Also, over time, cancer cells develop resistance to chemotherapy, due to which there is a demand for new drugs. Drug repurposing is a novel approach that focuses on finding new applications for the old clinically approved drugs. Current advances in the high-dimensional multiomics landscape, especially proteomics, genomics, and computational omics-data analysis, have facilitated drug repurposing. The drug repurposing approach provides cheaper, effective, and safe drugs with fewer side effects and fastens the process of drug development. The review further delineates each repurposed drug's original indication and mechanism of action in cancer. Along with this, the article also provides insight upon artificial intelligence and its application in drug repurposing. Clinical trials are vital for determining medication safety and effectiveness, and hence the clinical studies for each repurposed medicine in cancer, including their stages, status, and National Clinical Trial (NCT) identification, are reported in this review article. Various emerging evidences imply that repurposing drugs is critical for the faster and more affordable discovery of anti-cancerous drugs, and the advent of artificial intelligence-based computational tools can accelerate the translational cancer-targeting pipeline.

PFKFB4 interacts with FBXO28 to promote HIF-1α signaling in glioblastoma

Glioblastoma is a highly aggressive brain tumor for which there is no cure. The metabolic enzyme 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 4 (PFKFB4) is essential for glioblastoma stem-like cell (GSC) survival but its mode of action is unclear. Understanding the role of PFKFB4 in tumor cell survival could allow it to be leveraged in a cancer therapy. Here, we show the importance of PFKFB4 for glioblastoma growth in vivo in an orthotopic patient derived mouse model. In an evaluation of patient tumor samples of different cancer entities, PFKFB4 protein was found to be overexpressed in prostate, lung, colon, mammary and squamous cell carcinoma, with expression level correlating with tumor grade. Gene expression profiling in PFKFB4-silenced GSCs revealed a downregulation of hypoxia related genes and Western blot analysis confirmed a dramatic reduction of HIF (hypoxia inducible factor) protein levels. Through mass spectrometric analysis of immunoprecipitated PFKFB4, we identified the ubiquitin E3 ligase, F-box only protein 28 (FBXO28), as a new interaction partner of PFKFB4. We show that PFKFB4 regulates the ubiquitylation and subsequent proteasomal degradation of HIF-1α, which is mediated by the ubiquitin ligase activity of FBXO28. This newly discovered function of PFKFB4, coupled with its cancer specificity, provides a new strategy for inhibiting HIF-1α in cancer cells.

Assessment of the In Vitro Cytotoxic Profile of Two Broad-Spectrum Antibiotics-Tetracycline and Ampicillin-On Pharyngeal Carcinoma Cells

Background and Objectives: In spite of the fact that antibiotics are considered to be the cornerstone of modern medicine, their use in the treatment of cancer remains controversial. In the present study, the main objective was to examine the effects of two antibiotics—tetracycline and ampicillin—on the viability, morphology, migration, and organization and structure of the nuclei and the actin fiber network of pharyngeal carcinoma cells—Detroit-562. Materials and Methods: In order to determine the viability of the cells, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method was applied after the cells were stimulated with five concentrations of tetracycline and ampicillin (10, 25, 50, 75, and 100 μM) for 72 h. A scratch assay was used to assess the migration ability of the cells. For the visualization of the nuclei and actin fibers, 4,6-diamidino-2-phenylindole (Dapi) and Rhodamine-Phalloidin were used. Results: There are different effects of tetracycline and ampicillin. Thus, tetracycline: (i) exhibited a concentration-dependent cytotoxic effect, decreasing cell viability to approximately 46%; (ii) inhibits cellular migration up to 16% compared to 60% for control cells; and (iii) induces changes in cell morphology as well as apoptotic changes in the nucleus and F-actin fibers. In contrast, in the case of ampicillin, an increase in viability up to 113% was observed at 10 μM, while a decrease in viability up to approximately 94% was observed at the highest concentration tested (100 μM). Conclusions: The results indicated a different effect regarding the impact on pharyngeal carcinoma cells. Thus, tetracycline has a concentration-dependent cytotoxic effect, while in the case of ampicillin a slight stimulation of cell viability was observed.

Oxidative stress, autophagy, and apoptosis induced by doxycycline in loach fin cells in vitro

Cytotoxicity, molecular function disorder, mitophagy, and apoptosis were studied in loach fin cells in vitro after exposure to doxycycline (DOX). The semi-lethal concentration of DOX in loach cells was calculated as 668.96 ± 2.83 mol/L. Loss of cell viability and increases in vacuoles and autolysosomes were evident in cells exposed to DOX at 200 and 400 μmol/L, and apoptotic bodies occurred at 600 μmol/L. In addition, Superoxide Dismutase (SOD), catalase (CAT), Na⁺-K⁺-ATPase, and Ca²⁺-ATPase activities increased significantly in cells exposed to 200 μmol/L DOX, and dose-dependent inhibitory effects on activities were observed in cells exposed to 400 and 600 μmol/L DOX. Quantitative gene expression showed that 400 and 600 μmol/L DOX could induce caspase-3- and caspase-8-mediated apoptosis as well as caspase-activated DNase in loach cells. Transcriptome sequencing in DOX vs. control groups found 16,288 differentially expressed genes, among which protein binding (2633, 31.91%) was the most significant in Gene Ontology terms. Furthermore, 11,930 genes were enriched in 298 Kyoto Encyclopedia of Genes and Genomes (KEGG)pathways. The top three upregulated pathways included "lysosome", "protein processing in endoplasmic reticulum", and "proteasome". FPKM analysis indicated that most genes associated with autophagy and in "protein processing in the endoplasmic reticulum", "TNF signaling pathway", and "NF-kappa B signaling pathway" were upregulated. This suggests that at lower concentrations, DOX induces reactive oxidative species (ROS) in loach fin cells to reduce cell proliferation. ROS in turn stimulate oxidant stress, ion excretion capability and mitophagy to maintain cell homeostasis. Apoptosis was induced in cells subjected to higher concentrations of DOX. The transcriptome data and pathways determined in this study will provide a foundation for the analysis of DOX toxicity in loach cells, which must be examined thoroughly to further understand the cytotoxic mechanism of antibiotics in fish cells.

Targeting mitochondrial metabolism for metastatic cancer therapy

Primary tumors evolve metabolic mechanisms favoring glycolysis for adenosine triphosphate (ATP) generation and antioxidant defenses. In contrast, metastatic cells frequently depend on mitochondrial respiration and oxidative phosphorylation (OxPhos). This reliance of metastatic cells on OxPhos can be exploited using drugs that target mitochondrial metabolism. Therefore, therapeutic agents that act via diverse mechanisms, including the activation of signaling pathways that promote the production of reactive oxygen species (ROS) and/or a reduction in antioxidant defenses may elevate oxidative stress and inhibit tumor cell survival. In this review, we will provide (1) a mechanistic analysis of function-selective extracellular signal-regulated kinase-1/2 (ERK1/2) inhibitors that inhibit cancer cells through enhanced ROS, (2) a review of the role of mitochondrial ATP synthase in redox regulation and drug resistance, (3) a rationale for inhibiting ERK signaling and mitochondrial OxPhos toward the therapeutic goal of reducing tumor metastasis and treatment resistance. Recent reports from our laboratories using metastatic melanoma and breast cancer models have shown the preclinical efficacy of novel and rationally designed therapeutic agents that target ERK1/2 signaling and mitochondrial ATP synthase, which modulate ROS events that may prevent or treat metastatic cancer. These findings and those of others suggest that targeting a tumor's metabolic requirements and vulnerabilities may inhibit metastatic pathways and tumor growth. Approaches that exploit the ability of therapeutic agents to alter oxidative balance in tumor cells may be selective for cancer cells and may ultimately have an impact on clinical efficacy and safety. Elucidating the translational potential of metabolic targeting could lead to the discovery of new approaches for treatment of metastatic cancer.

Posaconazole inhibits the stemness of cancer stem-like cells by inducing autophagy and suppressing the Wnt/β-catenin/survivin signaling pathway in glioblastoma

Posaconazole (POS) has been reported to present potential antitumor activity for glioblastoma (GBM). However, its molecular mechanisms remain unclear. In this study, we found that POS has potent cytotoxicity and inhibits cell viability and proliferation in GBM. In addition, we adopted a sphere formation assay to detect the self-renewal capacity, performed western blotting to measure cancer stem-like cells (CSCs) marker proteins (CD133, SOX2, Nanog and Oct4) and applied flow cytometry to monitor the subpopulation of CD144⁺/CD33⁺ cells, and the results all demonstrated that POS can remarkably weaken CSCs stemness. Furthermore, western blotting, immunoflurescence, transmission electron microscopy and acridine orange staining were performed to detect autophagy-related proteins (LC3, SQSTM1, Beclin 1 and Atg5), count the numbers of endogenous LC3 puncta, visually observe the ultrastructural morphology of autophagosomes and judge the formation of acidic vesicular organelles, respectively, and the results validated that POS promotes autophagy induction. Importantly, the suppressive effect of POS on CSCs stemness was partially relieved when autophagy was blocked by the autophagy inhibitor chloroquine (CQ) or Atg5 shRNA. Bioinformatic techniques, including weighted gene coexpression network analysis (WGCNA), gene set difference analysis (GSVA) and KEGG pathway analysis, combined with experimental validations showed that survivin, which is implicated in both autophagy and the stem cell index, is one of the target proteins of POS and that POS weakens CSCs stemness via suppressing the Wnt/β-catenin signaling pathway in GBM. Besides, POS-induced autophagy and the Wnt/β-catenin signaling pathway are negative regulators for each other. Finally, the antitumor activity of POS was confirmed in GBM xenograft models in vivo. Consistent with the in vitro conclusions, POS upregulated the expression of LC3 and decreased the expression of CD133, survivin and β-catenin, as shown by the immunohistochemistry analysis. In summary, this work provides an experimental foundation for exploiting POS as a CSCs-targeting antitumor drug for GBM treatment.

External oxidant-free and transition metal-free synthesis of 5-amino-1,2,4-thiadiazoles as promising antibacterials against ESKAPE pathogen strains

A new route to 5-amino-1,2,4-thiadiazole derivatives via reaction of N-chloroamidines with isothiocyanates has been proposed. The advantages of this method are high product yields (up to 93%), the column chromatography-free workup procedure, scalability and the absence of additive oxidizing agents or transition metal catalysts. The 28 examples of 5-amino-1,2,4-thiadiazole derivatives obtaining via the proposing protocol were evaluated in vitro against ESKAPE pathogens strains (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter cloacae). It was found that compounds 5ba, 5bd, 6a, 6d and 6c have potent antibacterial activity (MIC values 0.09-1.5 μg mL^-1), which is superior to the activity of commercial antibiotics such as pefloxacin (MIC 4-8 μg mL^-1) and streptomycin (MIC 2-32 μg mL^-1). The additional cytotoxic assay of hit compounds on PANC-1 cell line demonstrated the low or non-cytotoxicity activity at the same level of concentrations. Thus, these 5 compounds are promising starting point for further antimicrobial drug development.

Tumour Stem Cells in Breast Cancer

Tumour stem cells (CSCs) are a self-renewing population that plays important roles in tumour initiation, recurrence, and metastasis. Although the medical literature is extensive, problems with CSC identification and cancer therapy remain. This review provides the main mechanisms of CSC action in breast cancer (BC): CSC markers and signalling pathways, heterogeneity, plasticity, and ecological behaviour. The dynamic heterogeneity of CSCs and the dynamic transitions of CSC⁻ non-CSCs and their significance for metastasis are considered.

Zn(II) 5,5-Diethylbarbiturate Complex Selectively Induces Apoptosis in Breast Cancer and Breast Cancer Stem-Like Cells

The biological activities of Zn(II) compounds have been extensively studied in recent years. In this study, the growth suppressive effect of Zn(II) 5,5-diethylbarbiturate complex on MCF-7 and MDA-MB-231 human breast cancer cells was determined by SRB and ATP viability assays and apoptosis-inducing effect by double staining method. Significant increase in cytokeratin 18 level, caspase 3/7 activity and annexin-V upregulation prove that Zn(II) complex has apoptotic effect in breast cancer cells. Intrinsic apoptosis pathway in MCF-7 cells and extrinsic apoptosis pathway in MDA-MB-231 cells was determined by Western blot (PARP, Cleave PARP, BAX, COX4, RIP, Caspase 8, Split Caspase 8, DR4 and B-Actin) and RT-PCR (PARP, Fas, Bcl-2, TNF10A, P53) analysis. No reduction of viability was found in MCF-710A healthy breast cells treated with Zn(II) complex. In breast cancer stem-like cells (MCF-7s), the Zn(II) complex was found to have a cytotoxic effect and to activate the apoptotic pathway. As a result, it was concluded that Zn(II) complex has anti-proliferative and apoptotic effects on breast cancer and breast cancer stem-like cells. Also this complex prevents the metastatic effect of cancer cells and does not effect to healthy cells so this complex has a specific effect on cancer cells. These findings might shed light on the discovery of new chemotherapeutic agents.

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.

Role of Integrin αvβ3 in Doxycycline-Induced Anti-Proliferation in Breast Cancer Cells

Doxycycline, an antibiotic, displays the inhibition of different signal transduction pathways, such as anti-inflammation and anti-proliferation, in different types of cancers. However, the anti-cancer mechanisms of doxycycline via integrin αvβ3 are incompletely understood. Integrin αvβ3 is a cell-surface anchor protein. It is the target for estrogen, androgen, and thyroid hormone and plays a pivotal role in the proliferation, migration, and angiogenic process in cancer cells. In our previous study, thyroxine hormones can interact with integrin αvβ3 to activate the extracellular signal-regulated kinase 1/2 (ERK1/2), and upregulate programmed death-ligand 1 (PD-L1) expression. In the current study, we investigated the inhibitory effects of doxycycline on proliferation in two breast cancer cell lines, MCF-7 and MDA-MB-231 cells. Doxycycline induces concentration-dependent anti-proliferation in both breast cancer cell lines. It regulates gene expressions involved in proliferation, pro-apoptosis, and angiogenesis. Doxycycline suppresses cell cyclin D1 (CCND1) and c-Myc which play crucial roles in proliferation. It also inhibits PD-L1 gene expression. Our findings show that modulation on integrin αvβ3 binding activities changed both thyroxine- and doxycycline-induced signal transductions by an integrin αvβ3 inhibitor (HSDVHK-NH₂). Doxycycline activates phosphorylation of focal adhesion kinase (FAK), a downstream of integrin, but inhibits the ERK1/2 phosphorylation. Regardless, doxycycline-induced FAK phosphorylation is blocked by HSDVHK-NH₂. In addition, the specific mechanism of action associated with pERK1/2 inhibition via integrin αvβ3 is unknown for doxycycline treatment. On the other hand, our findings indicated that inhibiting ERK1/2 activation leads to suppression of PD-L1 expression by doxycycline treatment. Furthermore, doxycycline-induced gene expressions are disturbed by a specific integrin αvβ3 inhibitor (HSDVHK-NH₂) or a mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinases (ERK) kinase (MAPK/ERK, MEK) inhibitor (PD98059). The results imply that doxycycline may interact with integrin αvβ3 and inhibits ERK1/2 activation, thereby regulating cell proliferation and downregulating PD-L1 gene expression in estrogen receptor (ER)-negative breast cancer MDA-MB-231 cells.

A Brief look at antitumor effects of doxycycline in the treatment of colorectal cancer and combination therapies

Colorectal cancer (CRC) is considered the second most frequent cancer globally and one of the deadliest malignancies in humans. On the other hand, over time and facing the challenges of cancer treatment, several therapeutic approaches, including surgery, radiotherapy, chemotherapy, and immunotherapy, are being developed. Evidence showed that combination therapies had given relatively satisfactory clinical outcomes in inhibiting tumor progression and increasing patient survival compared with monotherapy. Among the available compounds and drugs used in chemotherapy, doxycycline, an antimicrobial drug, has been suitable for treating several malignancies such as CRC. It has been revealed that doxycycline has anti-tumor properties and can help control tumor growth in various mechanisms, such as inhibiting anti-apoptotic and angiogenic proteins. In addition, studies have shown that combination therapy with doxycycline and other anti-tumor drugs, such as doxorubicin, anti-angiogenic factors, and anti-check-point blockers, can inhibit tumor progression. Therefore, this review summarized the anti-tumor mechanisms of doxycycline in CRC treatment and related combination therapies.

The Anticancer Potential of Doxycycline and Minocycline-A Comparative Study on Amelanotic Melanoma Cell Lines

Malignant melanoma is still a serious medical problem. Relatively high mortality, a still-growing number of newly diagnosed cases, and insufficiently effective methods of therapy necessitate melanoma research. Tetracyclines are compounds with pleiotropic pharmacological properties. Previously published studies on melanotic melanoma cells ascertained that minocycline and doxycycline exerted an anti-melanoma effect. The purpose of the study was to assess the anti-melanoma potential and mechanisms of action of minocycline and doxycycline using A375 and C32 human amelanotic melanoma cell lines. The obtained results indicate that the tested drugs inhibited proliferation, decreased cell viability, and induced apoptosis in amelanotic melanoma cells. The treatment caused changes in the cell cycle profile and decreased the intracellular level of reduced thiols and mitochondrial membrane potential. The exposure of A375 and C32 cells to minocycline and doxycycline triggered the release of cytochrome c and activated initiator and effector caspases. The anti-melanoma effect of analyzed drugs appeared to be related to the up-regulation of ERK1/2 and MITF. Moreover, it was noticed that minocycline and doxycycline increased the level of LC3A/B, an autophagy marker, in A375 cells. In summary, the study showed the pleiotropic anti-cancer action of minocycline and doxycycline against amelanotic melanoma cells. Considering all results, it could be concluded that doxycycline was a more potent drug than minocycline.

The Role of RNA Methylation in Regulating Stem Cell Fate and Function-Focus on m6A

The biological role of RNA methylation in stem cells has attracted increasing attention. Recent studies have demonstrated that RNA methylation plays a crucial role in self-renewal, differentiation, and tumorigenicity of stem cells. In this review, we focus on the biological role of RNA methylation modifications including N6-methyladenosine, 5-methylcytosine, and uridylation in embryonic stem cells, adult stem cells, induced pluripotent stem cells, and cancer stem cells, so as to provide new insights into the potential innovative treatments of cancer or other complex diseases.

Modulation of Immune Components on Stem Cell and Dormancy in Cancer

Cancer stem cells (CSCs) refer to a certain subpopulation within the tumor entity that is characterized by restricted cellular proliferation and multipotent differentiation potency. The existence of CSCs has been proven to contribute to the heterogeneity of malignancies, accounting for intensified tumorigenesis, treatment resistance, and metastatic spread. Dormancy was proposed as a reversible state of cancer cells that are temporarily arrested in the cell cycle, possessing several hallmarks that facilitate their survival within a devastating niche. This transient period is evoked to enter an actively proliferating state by multiple regulatory alterations, and one of the most significant and complex factors comes from local and systemic inflammatory reactions and immune components. Although CSCs and dormant cancer cells share several similarities, the clear relationship between these two concepts remains unclear. Thus, the detailed mechanism of immune cells interacting with CSCs and dormant cancer cells also warrants elucidation for prevention of cancer relapse and metastasis. In this review, we summarize recent findings and prospective studies on CSCs and cancer dormancy to conclude the relationship between these two concepts. Furthermore, we aim to outline the mechanism of immune components in interfering with CSCs and dormant cancer cells to provide a theoretical basis for the prevention of relapse and metastasis.

Doxycycline sensitizes renal cell carcinoma to chemotherapy by preferentially inhibiting mitochondrial translation

Objectives

The anti-cancer activity of doxycycline has been reported in many cancers but not renal cell carcinoma (RCC). This study aimed to determine the efficacy of doxycycline alone and in combination with paclitaxel and analyze the underlying mechanism in RCC.

Methods

Proliferation, colony formation and apoptosis assays were performed in RCC cell lines after drug treatments. An RCC xenograft mouse model was generated, and tumor growth was monitored. Mechanistic studies focused on mitochondrial translation and functions.

Results

Doxycycline at clinically achievable concentrations inhibited proliferation and colony formation and induced apoptosis in RCC cell lines. In normal kidney cells, doxycycline at the same concentrations either had no effect or was less effective. The combination index value demonstrated that doxycycline and paclitaxel were synergistic in vitro. Consistently, this combination therapy was significantly more effective than the monotherapy in RCC xenograft mice without causing significant toxicity. Mechanistic studies revealed that doxycycline acts on RCC cells via preferentially inhibiting mitochondrial DNA translation, thereby disrupting multiple mitochondrial complexes and impairing mitochondrial respiration.

Conclusions

Doxycycline is a useful addition to the treatment strategy for RCC. Our work also highlights the therapeutic value of mitochondrial translation inhibition in sensitizing RCC to chemotherapy.

Activation of the integrated stress response confers vulnerability to mitoribosome-targeting antibiotics in melanoma

The ability to adapt to environmental stress, including therapeutic insult, contributes to tumor evolution and drug resistance. In suboptimal conditions, the integrated stress response (ISR) promotes survival by dampening cytosolic translation. We show that ISR-dependent survival also relies on a concomitant up-regulation of mitochondrial protein synthesis, a vulnerability that can be exploited using mitoribosome-targeting antibiotics. Accordingly, such agents sensitized to MAPK inhibition, thus preventing the development of resistance in BRAFV600E melanoma models. Additionally, this treatment compromised the growth of melanomas that exhibited elevated ISR activity and resistance to both immunotherapy and targeted therapy. In keeping with this, pharmacological inactivation of ISR, or silencing of ATF4, rescued the antitumoral response to the tetracyclines. Moreover, a melanoma patient exposed to doxycycline experienced complete and long-lasting response of a treatment-resistant lesion. Our study indicates that the repurposing of mitoribosome-targeting antibiotics offers a rational salvage strategy for targeted therapy in BRAF mutant melanoma and a therapeutic option for NRAS-driven and immunotherapy-resistant tumors.

Synthesis of Silver-Doxycycline Complex Nanoparticles and Their Biological Evaluation on MCF-7 Cell Line of the Breast Cancer

In the current study, we aim to evaluate the effect of the combination of silver and doxycycline (silver-doxycycline complex) on the viability of the MCF-7 cell line of the breast in comparison with each of them. The Ag-doxycycline NPs were synthesized using silver nitrate and doxycycline solutions. The synthesized Ag-doxycycline NPs were characterized with several analyses. Ag-doxycycline NPs with a concentration of 25 μM is significantly more effective in decreasing the viability of MCF-7 cells than Ag with the same concentration ( $P<0.05$ ). Doxycycline with a concentration of 6.25 μM also has a more potent effect on the viability of MCF-7 cells than Ag with the same concentration ( $P<0.05$ ). Ag-doxycycline NPs with a 25 μM concentration is more effective than the concentration of 3.125 μM ( $P<0.05$ ). Ag-doxycycline NPs were found to be more effective than AgNPs alone in inhibiting the growth of the MCF-7 cells. Also, the increasing utility of nanotechnology in multiple aspects of medicine can lead to using this technology in the treatment of different types of cancer in the future.

Repurposing of Antimicrobial Agents for Cancer Therapy: What Do We Know?

The substantial costs of clinical trials, the lengthy timelines of new drug discovery and development, along the high attrition rates underscore the need for alternative strategies for finding quickly suitable therapeutics agents. Given that most approved drugs possess more than one target tightly linked to other diseases, it encourages promptly testing these drugs in patients. Over the past decades, this has led to considerable attention for drug repurposing, which relies on identifying new uses for approved or investigational drugs outside the scope of the original medical indication. The known safety of approved drugs minimizes the possibility of failure for adverse toxicology, making them attractive de-risked compounds for new applications with potentially lower overall development costs and shorter development timelines. This latter case is an exciting opportunity, specifically in oncology, due to increased resistance towards the current therapies. Indeed, a large body of evidence shows that a wealth of non-cancer drugs has beneficial effects against cancer. Interestingly, 335 drugs are currently being evaluated in different clinical trials for their potential activities against various cancers (Redo database). This review aims to provide an extensive discussion about the anti-cancer activities exerted by antimicrobial agents and presents information about their mechanism(s) of action and stage of development/evaluation.

Cross talk between autophagy and oncogenic signaling pathways and implications for cancer therapy

Autophagy is a highly conserved metabolic process involved in the degradation of intracellular components including proteins and organelles. Consequently, it plays a critical role in recycling metabolic energy for the maintenance of cellular homeostasis in response to various stressors. In cancer, autophagy either suppresses or promotes cancer progression depending on the stage and cancer type. Epithelial-mesenchymal transition (EMT) and cancer metastasis are directly mediated by oncogenic signal proteins including SNAI1, SLUG, ZEB1/2, and NOTCH1, which are functionally correlated with autophagy. In this report, we discuss the crosstalk between oncogenic signaling pathways and autophagy followed by possible strategies for cancer treatment via regulation of autophagy. Although autophagy affects EMT and cancer metastasis, the overall signaling pathways connecting cancer progression and autophagy are still illusive. In general, autophagy plays a critical role in cancer cell survival by providing a minimum level of energy via self-digestion. Thus, cancer cells face nutrient limitations and challenges under stress during EMT and metastasis. Conversely, autophagy acts as a potential cancer suppressor by degrading oncogenic proteins, which are essential for cancer progression, and by removing damaged components such as mitochondria to enhance genomic stability. Therefore, autophagy activators or inhibitors represent possible cancer therapeutics. We further discuss the regulation of autophagy-dependent degradation of oncogenic proteins and its functional correlation with oncogenic signaling pathways, with potential applications in cancer therapy.

Navigating metastatic colorectal treatment options in the USA: a survey of patient acceptance of skin toxicities associated with Vectibix

Abstract

Purpose

To understand the extent to which metastatic colorectal cancer (mCRC) patients receive education on the prevention and management associated with skin rash following Vectibix treatment. Furthermore, to investigate how this adverse event affects a patient’s quality of life (QoL) and influences their treatment decisions.

Methods

A cross-sectional survey was administered to 200 mCRC patients (100 Vectibix users and 100 Vectibix non-users). After excluding respondents who had used cetuximab, 61 Vectibix users and 56 Vectibix non-users remained.

Results

Most Vectibix users (79%) experienced a skin rash in response to treatment of which 65% considered the rash moderate, 27% mild, and 8% severe. Vectibix users generally felt they were adequately informed about the rash (83%), with the most common messages received related to sun protection. However, sunscreen was used by only 42% of patients prior to rash and 60% of patients following the appearance of rash. The use of oral antibiotics was low prior to rash (21%) and following rash (46%). Among patients experiencing a rash within the past week (n=16), 75% reported the rash had a large negative impact on their QoL based on the Dermatology Life Quality Index.

Conclusion

There was a disconnect between patients feeling they were adequately informed and use of prevention and management strategies such as sun protection. This suggests a gap in patient education and adoption currently exists on management strategies both prior to and following the appearance of rash. Given the negative impact that skin toxicity has on the patient’s quality of life, it is essential that patients receive and subsequently utilize all information that can minimize rash severity.

Advances in Multiple Stimuli-Responsive Drug-Delivery Systems for Cancer Therapy

Nanomedicines afford unique advantages in therapeutic intervention against tumors. However, conventional nanomedicines have failed to achieve the desired effect against cancers because of the presence of complicated physiological fluids and the tumor microenvironment. Stimuli-responsive drug-delivery systems have emerged as potential tools for advanced treatment of cancers. Versatile nano-carriers co-triggered by multiple stimuli in different levels of organisms (eg, extracorporeal, tumor tissue, cell, subcellular organelles) have aroused widespread interest because they can overcome sequential physiological and pathological barriers to deliver diverse therapeutic “payloads” to the desired targets. Furthermore, multiple stimuli-responsive drug-delivery systems (MSR-DDSs) offer a good platform for co-delivery of agents and reversing multidrug resistance. This review affords a comprehensive overview on the “landscape” of MSR-DDSs against tumors, highlights the design strategies of MSR-DDSs in recent years, discusses the putative advantage of oncotherapy or the obstacles that so far have hindered the clinical translation of MSR-DDSs.