Common Metabolic Pathways Implicated in Resistance to Chemotherapy Point to a Key Mitochondrial Role in Breast Cancer

OXPHOS inhibition overcomes chemoresistance in triple negative breast cancer

The hypothesis of a significant shift from oxidative phosphorylation (OXPHOS) to glycolysis in a number of solid tumors has been dominant for many years. Recently, however, evidence has begun to accumulate that OXPHOS is the major mode of energy production in many neoplasias, especially those that have undergone chemo- or radiotherapy, and especially in chemoresistant malignancies. In the present work, we demonstrated that chemoresistant triple-negative breast cancer cells prefer to obtain energy via OXPHOS to a greater extent than cells sensitive to chemotherapeutic agents, and therefore the former can be affected by some OXPHOS inhibitors. From a drug library containing several dozen antimicrobials, we selected those that inhibit OXPHOS in resistant TNBC cells and lead to mitochondrial dysfunction. We have also identified several pathways by which inhibition of growth suppression of chemoresistant cells occurs, including increased oxidative stress and mitophagy. Experiments in mice showed that selected OXPHOS inhibitors preferentially suppress tumor growth from chemoresistant but not from chemosensitive cells. The results of the present study suggest combinatorial therapy of such inhibitors and conventional anticancer drugs on resistant forms of tumors, if the latter show enhanced OXPHOS.

Antibacterials exert toxic effects on aquatic organisms by inhibiting respiration, inducing oxidative stress, mitochondrial dysfunction and autophagy

Although bactericidal antibiotics are an integral part of infectious disease medicine, the uncontrolled use of these drugs in recent years is beginning to affect the environment, especially water resources. With the exception of a few well-documented toxic effects, antimicrobials are thought to act mainly on bacteria and, at low doses, have no deleterious effects on eukaryotic organisms. However, since mitochondria are direct ancient relatives of prokaryotes, mitochondrial dysfunction induced by antibiotic exposure can also occur in higher eukaryotes. In this work, we used the microcrustacean Artemia salina to show how some known antibacterial drugs exert toxic effects on mitochondria, suppressing cellular and organismal respiration in aquatic organisms. We have demonstrated that exposure to antimicrobials of different classes, namely kanamycin A, tetracycline hydrochloride, erythromycin, and chloramphenicol, leads to the accumulation of reactive oxygen species and is accompanied by autophagy. Our results suggest that the emergence of antibactericidal drugs, increasingly appearing in wastewater, may have far-reaching consequences for aquatic areas adjacent to large cities.

Mitochondrial bioenergetics of breast cancer

Breast cancer cells exhibit metabolic heterogeneity based on tumour aggressiveness. Glycolysis and mitochondrial respiration are two major metabolic pathways for ATP production. The oxygen flux, oxygen tension, proton leakage, protonmotive force, inner mitochondrial membrane potential, ECAR and electrochemical proton gradient maintain metabolic homeostasis, ATP production, ROS generation, heat dissipation, and carbon flow and are referred to as "sub-domains" of mitochondrial bioenergetics. Tumour aggressiveness is influenced by these mechanisms, especially when breast cancer cells undergo metastasis. These physiological parameters for healthy mitochondria are as crucial as energy demands for tumour growth and metastasis. The instant energy demands are already elucidated under Warburg effects, while these parameters may have dual functionality to maintain cellular bioenergetics and cellular health. The tumour cell might maintain these mitochondrial parameters for mitochondrial health or avoid apoptosis, while energy production could be a second priority. This review focuses explicitly on the crosstalk between metabolic domains and the utilisation of these parameters by breast cancer cells for their progression. Some major interventions are discussed based on mitochondrial bioenergetics that need further investigation. This review highlights the pathophysiological significance of mitochondrial bioenergetics and the regulation of its sub-domains by breast tumour cells for uncontrolled proliferation.

Nanotherapeutics targeting autophagy regulation for improved cancer therapy

The clinical efficacy of current cancer therapies falls short, and there is a pressing demand to integrate new targets with conventional therapies. Autophagy, a highly conserved self-degradation process, has received considerable attention as an emerging therapeutic target for cancer. With the rapid development of nanomedicine, nanomaterials have been widely utilized in cancer therapy due to their unrivaled delivery performance. Hence, considering the potential benefits of integrating autophagy and nanotechnology in cancer therapy, we outline the latest advances in autophagy-based nanotherapeutics. Based on a brief background related to autophagy and nanotherapeutics and their impact on tumor progression, the feasibility of autophagy-based nanotherapeutics for cancer treatment is demonstrated. Further, emerging nanotherapeutics developed to modulate autophagy are reviewed from the perspective of cell signaling pathways, including modulation of the mammalian target of rapamycin (mTOR) pathway, autophagy-related (ATG) and its complex expression, reactive oxygen species (ROS) and mitophagy, interference with autophagosome-lysosome fusion, and inhibition of hypoxia-mediated autophagy. In addition, combination therapies in which nano-autophagy modulation is combined with chemotherapy, phototherapy, and immunotherapy are also described. Finally, the prospects and challenges of autophagy-based nanotherapeutics for efficient cancer treatment are envisioned.

Cancer resistance and metastasis are maintained through oxidative phosphorylation

Malignant tumors have increased energy requirements due to growth, differentiation or response to stress. A significant number of studies in recent years have described upregulation of mitochondrial genes responsible for oxidative phosphorylation (OXPHOS) in some tumors. Although OXPHOS is replaced by glycolysis in some tumors (Warburg effect), both processes can occur simultaneously during the evolution of the same malignancies. In particular, chemoresistant and/or cancer stem cells appear to find a way to activate OXPHOS and metastasize. In this paper, we discuss recent work showing upregulation of OXPHOS in chemoresistant tumors and cell models. In addition, we show an inverse correlation of OXPHOS gene expression with the survival time of cancer patients after chemotherapy and discuss combination therapies for resistant tumors.

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.

Correlation between the Warburg effect and progression of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is ineligible for hormonal therapy and Her-2-targeted therapy due to the negative expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2. Although targeted therapy and immunotherapy have been shown to attenuate the aggressiveness of TNBC partially, few patients have benefited from them. The conventional treatment for TNBC remains chemotherapy. Chemoresistance, however, impedes therapeutic progress over time, and chemotherapy toxicity increases the burden of cancer on patients. Therefore, introducing more advantageous TNBC treatment options is a necessity. Metabolic reprogramming centered on glucose metabolism is considered a hallmark of tumors. It is described as tumor cells tend to convert glucose to lactate even under normoxic conditions, a phenomenon known as the Warburg effect. Similar to Darwinian evolution, its emergence is attributed to the selective pressures formed by the hypoxic microenvironment of pre-malignant lesions. Of note, the Warburg effect does not disappear with changes in the microenvironment after the formation of malignant tumor phenotypes. Instead, it forms a constitutive expression mediated by mutations or epigenetic modifications, providing a robust selective survival advantage for primary and metastatic lesions. Expanding evidence has demonstrated that the Warburg effect mediates multiple invasive behaviors in TNBC, including proliferation, metastasis, recurrence, immune escape, and multidrug resistance. Moreover, the Warburg effect-targeted therapy has been testified to be feasible in inhibiting TNBC progression. However, not all TNBCs are sensitive to glycolysis inhibitors because TNBC cells flexibly switch their metabolic patterns to cope with different survival pressures, namely metabolic plasticity. Between the Warburg effect-targeted medicines and the actual curative effect, metabolic plasticity creates a divide that must be continuously researched and bridged.

Chloroquine Sensitizes Esophageal Carcinoma EC109 Cells to Paclitaxel by Inhibiting Autophagy

As an autophagy inhibitor, chloroquine (CQ) showed anti-tumor effect on several types of cancer and paclitaxel (PTX) is widely used in the treatment of esophageal carcinoma patients, but chemoresistance remains a major hurdle for PTX application due to the cytoprotective autophagy. Therefore, the aim of this study was to investigate whether CQ could elevate the anti-tumor effect of PTX on esophageal carcinoma cell line EC109 and explore the potential molecular mechanisms. We confirmed the suppressive effect of PTX on EC109 by MTT, scratch test, transwell and soft agar assay. And, we detected the key proteins in Akt/mTOR pathway, as well as the autophagy marker LC3 and p62 through Western Blot. In addition, GFP-LC3 plasmid was transfected into EC109 cells to monitor the autophagosome after CQ and PTX treatment. Ultimately, we observed the alterations in the proliferation and colony formation abilities of EC109 after knocking down mTOR by shRNA. We confirmed PTX could suppress the proliferation, migration and colony formation (all P < 0.05) abilities of EC109, and CQ could sensitize the inhibition effect of PTX by inhibiting autophagy through Akt/mTOR pathway. Furthermore, inhibiting Akt/mTOR pathway initiated autophagy and enhanced the sensitivity of EC109 to CQ and PTX. In summary, we suggest CQ could be used as a potential chemosensitizer for PTX in esophageal carcinoma treatment.

Transcriptomic and Proteomic Profiles for Elucidating Cisplatin Resistance in Head-and-Neck Squamous Cell Carcinoma

To identify the novel genes involved in chemoresistance in head and neck squamous cell carcinoma (HNSCC), we explored the expression profiles of the following cisplatin (CDDP) resistant (R) versus parental (sensitive) cell lines by RNA-sequencing (RNA-seq): JHU029, HTB-43 and CCL-138. Using the parental condition as a control, 30 upregulated and 85 downregulated genes were identified for JHU029-R cells; 263 upregulated and 392 downregulated genes for HTB-43-R cells, and 154 upregulated and 68 downregulated genes for CCL-138-R cells. Moreover, we crossed-checked the RNA-seq results with the proteomic profiles of HTB-43-R (versus HTB-43) and CCL-138-R (versus CCL-138) cell lines. For the HTB-43-R cells, 21 upregulated and 72 downregulated targets overlapped between the proteomic and transcriptomic data; whereas in CCL-138-R cells, four upregulated and three downregulated targets matched. Following an extensive literature search, six genes from the RNA-seq (CLDN1, MAGEB2, CD24, CEACAM6, IL1B and ISG15) and six genes from the RNA-seq and proteomics crossover (AKR1C3, TNFAIP2, RAB7A, LGALS3BP, PSCA and SSRP1) were selected to be studied by qRT-PCR in 11 HNSCC patients: six resistant and five sensitive to conventional therapy. Interestingly, the high MAGEB2 expression was associated with resistant tumours and is revealed as a novel target to sensitise resistant cells to therapy in HNSCC patients.

Mechanism underlying linezolid-induced peripheral neuropathy in multidrug-resistant tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) remains a main global health concern as there is no comprehensive therapeutic intervention yet and numerous adverse effects follow the therapeutic process. In recent years, linezolid has been frequently used for treating MDR-TB. However, peripheral neuropathy associated with linezolid has reduced patient compliance. The current study explored the mechanism underlying linezolid-induced peripheral neuropathy in MDR-TB. Autophagy plays a neuroprotective role against peripheral nerve injury. We hypothesized that autophagy might also play a neuroprotective role against linezolid-induced peripheral neuropathy. In this study, we collected 12 questionnaires from MDR-TB patients in our hospital, and 10 of them developed linezolid-induced pain. The pain is mainly concentrated in the feet and accompanied by numbness. Subsequently, we used Sprague-Dawley (SD) rats and Schwann cells (SCs) to explore the mechanism. We found that linezolid causes a sparse arrangement of sciatic nerve tissue with associated loss of neurons, myelin sheaths, and down-regulation of LC3B expression. These results were also confirmed by in vitro experiments, showing that linezolid inhibited the proliferation of SCs. And the expression of P-AKT and P62 was elevated, and the expression of LC3B declined compared with the control group. Moreover, chloroquine (CQ), an autophagy inhibitor, also exhibited experimental results similar to linezolid. In summary, we conclude that linezolid-induced peripheral neuropathy is associated with the inhibition of autophagy flux.

Advances in the Current Understanding of the Mechanisms Governing the Acquisition of Castration-Resistant Prostate Cancer

Despite aggressive treatment and androgen-deprivation therapy, most prostate cancer patients ultimately develop castration-resistant prostate cancer (CRPC), which is associated with high mortality rates. However, the mechanisms governing the development of CRPC are poorly understood, and androgen receptor (AR) signaling has been shown to be important in CRPC through AR gene mutations, gene overexpression, co-regulatory factors, AR shear variants, and androgen resynthesis. A growing number of non-AR pathways have also been shown to influence the CRPC progression, including the Wnt and Hh pathways. Moreover, non-coding RNAs have been identified as important regulators of the CRPC pathogenesis. The present review provides an overview of the relevant literature pertaining to the mechanisms governing the molecular acquisition of castration resistance in prostate cancer, providing a foundation for future, targeted therapeutic efforts.

Targeting cancer stem cells with antibiotics inducing mitochondrial dysfunction as an alternative anticancer therapy

Traditional cancer treatments based on chemo- and/or radiotherapy effectively kill only differentiated cancer cells, while metastasis and recurrences are caused by surviving cancer resistant cells (CRC) or a special subpopulation of cancer cells known as cancer stem cells (CSC). Both of these cell types compromise anticancer treatment through various mechanisms, including withdrawal of the anticancer drug through ATP-binding cassette transporters, increased expression of DNA repair genes, or transition to a quiescent phenotype. In contrast to many cancers, where energy consumption is due to glycolysis (Warburg effect), the bioenergetics of CSC and CRC is most often related to oxidative phosphorylation, that is, dependent on mitochondrial function. Therefore, compounds that induce mitochondrial dysfunction (MDF), such as some antibiotics, may represent an alternative approach to anticancer therapy. This review summarizes the major recent works on the use of antibiotics to target tumors via CSC and suggests next steps for developing this approach.

Movement of Mitochondria with Mutant DNA through Extracellular Vesicles Helps Cancer Cells Acquire Chemoresistance

Triple negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer with the worst prognosis after chemo- or radiation therapy. This is mainly due to the development of cancer chemoresistance accompanied by tumor recurrence. In this work, we investigated a new mechanism of acquired chemoresistance of TNBC cells. We showed that extracellular vehicles (EVs) of chemoresistant TNBC cells can transfer mitochondria to sensitive cancer cells, thus increasing their chemoresistance. Such transfer, but with less efficiency, can be carried out over short distances using tunneling nanotubes. In addition, we showed that exosome fractions carrying mitochondria from resistant TNBC cells contribute to acquired chemoresistance by increasing mtDNA levels with mutations in the mtND4 gene responsible for tumorigenesis. Blocking mitochondrial transport by exosome inhibitors, including GW4869, reduced acquired TNBC chemoresistance. These results could lead to the identification of new molecular targets necessary for more effective treatment of this type of cancer.

Thermosensitive hydrogel for in situ-controlled methotrexate delivery

Methotrexate (MTX) is widely used for the treatment of various types of cancer; however, it has drawbacks such as low solubility, lack of selectivity, premature degradation, and side effects. To solve these weaknesses, a hydrogel with the ability to contain and release MTX under physiological conditions without burst release was synthesized. The hydrogel was fabricated with a poly(ɛ-caprolactone)-b-poly(ethylene glycol)-b-poly(ɛ-caprolactone) (PCL–PEG–PCL) triblock copolymer, synthesized by ring-opening polymerization. The characterizations by proton nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectrometry confirmed the copolymer assembly, whereas the molecular weight analysis validated the PCL2000–PEG1000–PCL2000 structure. The copolymer aqueous solution exhibited sol–gel phase transition at 37°C and injection capacity. The hydrogel supported a load of 1,000 μg MTX·mL−1, showing a gradual and sustained release profile of the drug for 14 days, with a delivery up to 92% at pH 6.7. The cytotoxicity of the MTX-loaded hydrogel was performed by the methyl thiazole tetrazolium assay, showing a mean inhibitory concentration of 50% of MCF-7 cells (IC50) at 43 µg MTX·mL−1.

Mitochondrial and glycolytic extracellular flux analysis optimization for isolated pig intestinal epithelial cells

Intestinal epithelial cells (IECs) are crucial to maintain intestinal function and the barrier against the outside world. To support their function they rely on energy production, and failure to produce enough energy can lead to IEC malfunction and thus decrease intestinal barrier function. However, IEC metabolic function is not often used as an outcome parameter in intervention studies, perhaps because of the lack of available methods. We therefore developed a method to isolate viable IECs, suitable to faithfully measure their metabolic function by determining extracellular glycolytic and mitochondrial flux. First, various methods were assessed to obtain viable IECs. We then adapted a previously in-house generated image-analysis algorithm to quantify the amount of seeded IECs. Correcting basal respiration data of a group of piglets using this algorithm reduced the variation, showing that this algorithm allows for more accurate analysis of metabolic function. We found that delay in metabolic analysis after IEC isolation decreases their metabolic function and should therefore be prevented. The presence of antibiotics during isolation and metabolic assessment also decreased the metabolic function of IECs. Finally, we found that primary pig IECs did not respond to Oligomycin, a drug that inhibits complex V of the electron transport chain, which may be because of the presence of drug exporters. A method was established to faithfully measure extracellular glycolytic and mitochondrial flux of pig primary IECs. This tool is suitable to gain a better understanding of how interventions affect IEC metabolic function.

Combinatorial Strategies to Target Molecular and Signaling Pathways to Disarm Cancer Stem Cells

Cancer is an urgent public health issue with a very huge number of cases all over the world expected to increase by 2040. Despite improved diagnosis and therapeutic protocols, it remains the main leading cause of death in the world. Cancer stem cells (CSCs) constitute a tumor subpopulation defined by ability to self-renewal and to generate the heterogeneous and differentiated cell lineages that form the tumor bulk. These cells represent a major concern in cancer treatment due to resistance to conventional protocols of radiotherapy, chemotherapy and molecular targeted therapy. In fact, although partial or complete tumor regression can be achieved in patients, these responses are often followed by cancer relapse due to the expansion of CSCs population. The aberrant activation of developmental and oncogenic signaling pathways plays a relevant role in promoting CSCs therapy resistance. Although several targeted approaches relying on monotherapy have been developed to affect these pathways, they have shown limited efficacy. Therefore, an urgent need to design alternative combinatorial strategies to replace conventional regimens exists. This review summarizes the preclinical studies which provide a proof of concept of therapeutic efficacy of combinatorial approaches targeting the CSCs.

Filtering of the Gene Signature as the Predictors of Cisplatin-Resistance in Ovarian Cancer

BACKGROUND

Gene expression profiling and prediction of drug responses based on the molecular signature indicate new molecular biomarkers which help to find the most effective drugs according to the tumor characteristics.

OBJECTIVES

In this study two independent datasets, GSE28646 and GSE15372 were subjected to meta-analysis based on Affymetrix microarrays.

MATERIAL AND METHODS

In-silico methods were used to determine differentially expressed genes (DEGs) in the previously reported sensitive and resistant A2780 cell lines to Cisplatin. Gene Fuzzy Scoring (GFS) and Principle Component Analysis (PCA) were then used to eliminate batch effects and reduce data dimension, respectively. Moreover, SVM method was performed to classify sensitive and resistant data samples. Furthermore, Wilcoxon Rank sum test was performed to determine DEGs. Following the selection of drug resistance markers, several networks including transcription factor-target regulatory network and miRNA-target network were constructed and Differential correlation analysis was performed on these networks.

RESULTS

The trained SVM successfully classified sensitive and resistant data samples. Moreover, Performing DiffCorr analysis on the sensitive and resistant samples resulted in detection of 27 and 25 significant (with correlation ≥|0.9|) pairs of genes that respectively correspond to newly constructed correlations and loss of correlations in the resistant samples.

CONCLUSIONS

Our results indicated the functional genes and networks in Cisplatin resistance of ovarian cancer cells and support the importance of differential expression studies in ovarian cancer chemotherapeutic agent responsiveness.

Dual mTORC1/mTORC2 Inhibition as a Host-Directed Therapeutic Target in Pathologically Distinct Mouse Models of Tuberculosis

Efforts to develop more effective and shorter-course therapies for tuberculosis have included a focus on host-directed therapy (HDT). The goal of HDT is to modulate the host response to infection, thereby improving immune defenses to reduce the duration of antibacterial therapy and/or the amount of lung damage. As a mediator of innate and adaptive immune responses involved in eliminating intracellular pathogens, autophagy is a potential target for HDT in tuberculosis. Because Mycobacterium tuberculosis modulates mammalian target of rapamycin (mTOR) signaling to impede autophagy, pharmacologic mTOR inhibition could provide effective HDT. mTOR exists within two distinct multiprotein complexes, mTOR complex-1 (mTORC1) and mTOR complex-2 (mTORC2). Rapamycin and its analogs only partially inhibit mTORC1. We hypothesized that novel mTOR kinase inhibitors blocking both complexes would have expanded therapeutic potential. We compared the effects of two mTOR inhibitors, rapamycin and the orally available mTOR kinase domain inhibitor CC214-2, which blocks both mTORC1 and mTORC2, as adjunctive therapies against murine TB when added to the first-line regimen (isoniazid, rifampin, pyrazinamide, and ethambutol [RHZE]) or the novel bedaquiline-pretomanid-linezolid (BPaL) regimen. Neither mTOR inhibitor affected lung CFU counts after 4 to 8 weeks of treatment when combined with BPaL or RHZE. However, addition of CC214-2 to BPaL and RHZE was associated with significantly fewer relapses in C3HeB/FeJ mice compared to addition of rapamycin and, in RHZE-treated mice, resulted in fewer relapses than RHZE alone. Therefore, CC214-2 and related mTOR kinase inhibitors may be more effective candidates for HDT than rapamycin analogs and may have the potential to shorten the duration of TB treatment.

Triphenilphosphonium Analogs of Chloramphenicol as Dual-Acting Antimicrobial and Antiproliferating Agents

In the current work, in continuation of our recent research, we synthesized and studied new chimeric compounds, including the ribosome-targeting antibiotic chloramphenicol (CHL) and the membrane-penetrating cation triphenylphosphonium (TPP), which are linked by alkyl groups of different lengths. Using various biochemical assays, we showed that these CAM-Cn-TPP compounds bind to the bacterial ribosome, inhibit protein synthesis in vitro and in vivo in a way similar to that of the parent CHL, and significantly reduce membrane potential. Similar to CAM-C4-TPP, the mode of action of CAM-C10-TPP and CAM-C14-TPP in bacterial ribosomes differs from that of CHL. By simulating the dynamics of CAM-Cn-TPP complexes with bacterial ribosomes, we proposed a possible explanation for the specificity of the action of these analogs in the translation process. CAM-C10-TPP and CAM-C14-TPP more strongly inhibit the growth of the Gram-positive bacteria, as compared to CHL, and suppress some CHL-resistant bacterial strains. Thus, we have shown that TPP derivatives of CHL are dual-acting compounds targeting both the ribosomes and cellular membranes of bacteria. The TPP fragment of CAM-Cn-TPP compounds has an inhibitory effect on bacteria. Moreover, since the mitochondria of eukaryotic cells possess qualities similar to those of their prokaryotic ancestors, we demonstrate the possibility of targeting chemoresistant cancer cells with these compounds.

3-Methyladenine-enhanced susceptibility to sorafenib in hepatocellular carcinoma cells by inhibiting autophagy

As an effective targeted therapy for advanced hepatocellular carcinoma (HCC), sorafenib resistance has been frequently reported in recent years, with the activation of autophagy by cancer cells under drug stress being one of the crucial reasons. Sorafenib treatment could enhance autophagy in HCC cells and autophagy is also considered as an important mechanisms of drug resistance. Therefore, the inhibition of autophagy is a potential way to improve the sensitivity and eliminate drug resistance to restore their efficacy. To determine whether autophagy is involved in sorafenib resistance and investigate its role in the regulation of HepG2 cells' (an HCC cell line) chemosensitivity to sorafenib, we simultaneously treated HepG2 with sorafenib and 3-Methyladenine (3-MA) (a common autophagy inhibitor). First, by performing cell counting kit 8 cell viability assay, Hoechst 33342 apoptosis staining, and Annexin V-fluorescein isothiocyanate/propidium iodide apoptosis kit detection, we found that both sorafenib and 3-MA effectively inhibitted the proliferative activity of HepG2 cells and induced their apoptosis to a certain extent. This effect was significantly enhanced after these two drugs were combined, which was also confirmed by the increased expression of apoptosis-related proteins. Subsequently, by using AAV-GFP-LC3 transfection methods and transmission electron microscopy, we found that both the number and activity of autophagosomes in HepG2 cells in sorafenib and 3-MA group were significantly reduced, suggesting that autophagy activity was inhibited, and this result was consistent with the expression results of autophagy-related proteins. Therefore, we conclude that 3-MA may attenuate the acquired drug resistance of sorafenib by counteracting its induction of autophagy activity, thus enhancing its sensitivity to advanced HCC therapy.

Enhanced DNA damage response through RAD50 in triple negative breast cancer resistant and cancer stem-like cells contributes to chemoresistance

A growing body of evidence supports the notion that cancer resistance is driven by a small subset of cancer stem cells (CSC), responsible for tumor initiation, growth, and metastasis. Both CSC and chemoresistant cancer cells may share common qualities to activate a series of self-defense mechanisms against chemotherapeutic drugs. Here, we aimed to identify proteins in chemoresistant triple-negative breast cancer (TNBC) cells and corresponding CSC-like spheroid cells that may contribute to their resistance. We have identified several candidate proteins representing the subfamilies of DNA damage response (DDR) system, the ATP-binding cassette, and the 26S proteasome degradation machinery. We have also demonstrated that both cell types exhibit enhanced DDR when compared to corresponding parental counterparts, and identified RAD50 as one of the major contributors in the resistance phenotype. Finally, we have provided evidence that depleting or blocking RAD50 within the Mre11-Rad50-NBS1 (MRN) complex resensitizes CSC and chemoresistant TNBC cells to chemotherapeutic drugs.

Selective toxicity of antibacterial agents-still a valid concept or do we miss chances and ignore risks?

BACKGROUND

Selective toxicity antibacteribiotics is considered to be due to interactions with targets either being unique to bacteria or being characterized by a dichotomy between pro- and eukaryotic pathways with high affinities of agents to bacterial- rather than eukaryotic targets. However, the theory of selective toxicity oversimplifies the complex modes of action of antibiotics in pro- and eukaryotes.

METHODS AND OBJECTIVE

This review summarizes data describing multiple modes of action of antibiotics in eukaryotes.

RESULTS

Aminoglycosides, macrolides, oxazolidinones, chloramphenicol, clindamycin, tetracyclines, glycylcyclines, fluoroquinolones, rifampicin, bedaquillin, ß-lactams inhibited mitochondrial translation either due to binding to mitosomes, inhibition of mitochondrial RNA-polymerase-, topoisomerase 2ß-, ATP-synthesis, transporter activities. Oxazolidinones, tetracyclines, vancomycin, ß-lactams, bacitracin, isoniazid, nitroxoline inhibited matrix-metalloproteinases (MMP) due to chelation with zinc and calcium, whereas fluoroquinols fluoroquinolones and chloramphenicol chelated with these cations, too, but increased MMP activities. MMP-inhibition supported clinical efficacies of ß-lactams and daptomycin in skin-infections, and of macrolides, tetracyclines in respiratory-diseases. Chelation may have contributed to neuroprotection by ß-lactams and fluoroquinolones. Aminoglycosides, macrolides, chloramphenicol, oxazolidins oxazolidinones, tetracyclines caused read-through of premature stop codons. Several additional targets for antibiotics in human cells have been identified like interaction of fluoroquinolones with DNA damage repair in eukaryotes, or inhibition of mucin overproduction by oxazolidinones.

CONCLUSION

The effects of antibiotics on eukaryotes are due to identical mechanisms as their antibacterial activities because of structural and functional homologies of pro- and eukaryotic targets, so that the effects of antibiotics on mammals are integral parts of their overall mechanisms of action.

Androgen Deprivation Induces Transcriptional Reprogramming in Prostate Cancer Cells to Develop Stem Cell-Like Characteristics

Enzalutamide, an antiandrogen, is approved for therapy of castration resistant prostate cancer. Clinical applications have shown that approximately 30% of patients acquire resistance after a short period of treatment. However, the molecular mechanisms underlying this resistance is not completely understood. To identify transcriptomic signatures associated with acquisition of drug resistance we profiled gene expression of paired enzalutamide sensitive and resistant human prostate cancer LNCaP (lymph node carcinoma of the prostate) and C4-2B cells. Overlapping genes differentially regulated in the enzalutamide resistant cells were ranked by Ingenuity Pathway Analysis and their functional validation was performed using ingenuity knowledge database followed by confirmation to correlate transcript with protein expression. Analysis revealed that genes associated with cancer stem cells, such as POU5F1 (OCT4), SOX2, NANOG, BMI1, BMP2, CD44, SOX9, and ALDH1 were markedly upregulated in enzalutamide resistant cells. Amongst the pathways enriched in the enzalutamide-resistant cells were those associated with RUNX2, hedgehog, integrin signaling, and molecules associated with elastic fibers. Further examination of a patient cohort undergoing ADT and its comparison with no-ADT group demonstrated high expression of POU5F1 (OCT4), ALDH1, and SOX2 in ADT specimens, suggesting that they may be clinically relevant therapeutic targets. Altogether, our approach exhibits the potential of integrative transcriptomic analyses to identify critical genes and pathways of antiandrogen resistance as a promising approach for designing novel therapeutic strategies to circumvent drug resistance.

Identification of metabolic changes leading to cancer susceptibility in Fanconi anemia cells

Fanconi anemia (FA) is a chromosomal instability disorder of bone marrow associated with aplastic anemia, congenital abnormalities and a high risk of malignancies. The identification of more than two dozen FA genes has revealed a plethora of interacting proteins that are mainly involved in repair of DNA interstrand crosslinks (ICLs). Other important findings associated with FA are inflammation, oxidative stress response, mitochondrial dysfunction and mitophagy. In this work, we performed quantitative proteomic and metabolomic analyses on defective FA cells and identified a number of metabolic abnormalities associated with cancer. In particular, an increased de novo purine biosynthesis, a high concentration of fumarate, and an accumulation of purinosomal clusters were found. This was in parallel with decreased OXPHOS and altered glycolysis. On the whole, our results indicate an association between the need for nitrogenous bases upon impaired DDR in FA cells with a subsequent increase in purine metabolism and a potential role in oncogenesis.

pH-responsive polymer micelles for methotrexate delivery at tumor microenvironments

Methotrexate (MTX) anticancer drug was successfully loaded and released in a controlled manner from polymer micelles made of a diblock copolymer of poly(monomethoxy ethylene glycol)-b-poly(ε-caprolactone) (mPEG-PCL). The empty and MTX-loaded micelles (MTX/mPEG-PCL) were characterized by electron microscopy. The drug release dependence upon pH 5.4, 6.5, and 7.4 for 30 days was proven and characterized by UV-Vis spectroscopy. The cytotoxic effect of MTX/mPEG-PCL micelles on MCF-7 breast cancer cells was evaluated through an MTT assay. The morphological analysis indicated the successful formation of micelles of 76 and 131 nm for empty and MTX-loaded micelles, respectively. An encapsulation efficiency of 70.2% and a loading capacity of 8.8% were obtained. The in vitro release of MTX showed a gradual and sustained profile over 22 days, with a clear trend to much higher release at acidic pH (80 and 90% for pH 6.7 and 5.5, respectively). The MTX/mPEG-PCL micelles showed an IC50 of MCF-7 cells at 30 µg mL−1. The results suggested that MTX/mPEG-PCL could be a promising drug delivery system for cancer treatment.

TSPAN1: A Novel Protein Involved in Head and Neck Squamous Cell Carcinoma Chemoresistance

Simple Summary

Therapy resistance in head and neck squamous cell carcinoma (HNSCC) patients is the main obstacle to achieve more effective treatments that improve survival and quality of life of these patients. Therefore, it is of vital importance to unravel the molecular and cellular mechanisms by which tumor cells acquire resistance to chemotherapy. We conducted a comparative proteomic study involving cisplatin-resistant cells and cancer stem cells with the aim of identifying proteins potentially implicated in the acquisition of cisplatin resistance. Through this study, we identified for the first time tetraspanin-1 (TSPAN1) as an important protein involved in the development, progression and chemoresistance of HNSCC tumors.

Abstract

Sensitization of resistant cells and cancer stem cells (CSCs) represents a major challenge in cancer therapy. A proteomic study revealed tetraspanin-1 (TSPAN1) as a protein involved in acquisition of cisplatin (CDDP) resistance (Data are available via ProteomeXchange with identifier PXD020159). TSPAN1 was found to increase in CDDP-resistant cells, CSCs and biopsies from head and neck squamous cell carcinoma (HNSCC) patients. TSPAN1 depletion in parental and CDDP-resistant HNSCC cells reduced cell proliferation, induced apoptosis, decreased autophagy, sensitized to chemotherapeutic agents and inhibited several signaling cascades, with phospho-SRC inhibition being a major common target. Moreover, TSPAN1 depletion in vivo decreased the size and proliferation of parental and CDDP-resistant tumors and reduced metastatic spreading. Notably, CDDP-resistant tumors showed epithelial–mesenchymal transition (EMT) features that disappeared upon TSPAN1 inhibition, suggesting a link of TSPAN1 with EMT and metastasis. Immunohistochemical analysis of HNSCC specimens further revealed that TSPAN1 expression was correlated with phospho-SRC (pSRC), and inversely with E-cadherin, thus reinforcing TSPAN1 association with EMT. Overall, TSPAN1 emerges as a novel oncogenic protein and a promising target for HNSCC therapy.

Down Syndrome Is a Metabolic Disease: Altered Insulin Signaling Mediates Peripheral and Brain Dysfunctions

Down syndrome (DS) is the most frequent chromosomal abnormality that causes intellectual disability, resulting from the presence of an extra complete or segment of chromosome 21 (HSA21). In addition, trisomy of HSA21 contributes to altered energy metabolism that appears to be a strong determinant in the development of pathological phenotypes associated with DS. Alterations include, among others, mitochondrial defects, increased oxidative stress levels, impaired glucose, and lipid metabolism, finally resulting in reduced energy production and cellular dysfunctions. These molecular defects seem to account for a high incidence of metabolic disorders, i.e., diabetes and/or obesity, as well as a higher risk of developing Alzheimer’s disease (AD) in DS. A dysregulation of the insulin signaling with reduced downstream pathways represents a common pathophysiological aspect in the development of both peripheral and central alterations leading to diabetes/obesity and AD. This is further strengthened by evidence showing that the molecular mechanisms responsible for such alterations appear to be similar between peripheral organs and brain. Considering that DS subjects are at high risk to develop either peripheral or brain metabolic defects, this review will discuss current knowledge about the link between trisomy of HSA21 and defects of insulin and insulin-related pathways in DS. Drawing the molecular signature underlying these processes in DS is a key challenge to identify novel drug targets and set up new prevention strategies aimed to reduce the impact of metabolic disorders and cognitive decline.

The influence of mitochondrial-directed regulation of Wnt signaling on tumorigenesis

Mitochondria are dynamic organelles that play a key role in integrating cellular signaling. Mitochondrial alterations are evident in all stages of tumorigenesis and targeting mitochondrial pathways has emerged as an anticancer therapeutic strategy. The Wnt-signaling pathway regulates many fundamental cellular functions such as proliferation, survival, migration, stem-cell maintenance, and mitochondrial metabolism and dynamics. Emerging evidence demonstrates that mitochondrial-induced regulation of Wnt signaling provides an additional mechanism to influence cell-fate decisions. Crosstalk between mitochondria and Wnt signaling presents a feedforward loop in which Wnt activation regulates mitochondrial function that, in turn, drives Wnt signaling. In this mini-review, we will discuss the recent evidence revealing the mitochondrial control of Wnt signaling and its implications for tumorigenesis and anticancer therapeutic targeting.

Nuclear Factor Erythroid-Derived 2-Like 2-Induced Reductive Stress Favors Self-Renewal of Breast Cancer Stem-Like Cells via the FoxO3a-Bmi-1 Axis

Aims: A subpopulation of cancer cells, termed cancer stem cells (CSCs), has stemness properties, such as self-renewal and differentiation, which drive cancer recurrence and tumor resistance. CSCs possess enhanced protection capabilities to maintain reduced intracellular levels of reactive oxygen species (ROS) compared with nonstem-like cancer cells. This study investigated whether reductive stress could regulate self-renewal activity in breast CSCs. Results: We found that manifestation of stemness in breast cancer stem-like cells was associated with an elevated production of reduced glutathione (GSH) maintained by upregulation of glutamate cysteine ligase catalytic subunit (GCLC) and consequently, lowered ROS levels. This was accompanied by upregulation of phospho-AMP-activated protein kinase, FoxO3a, and Bmi-1. Notably, expression of nuclear factor erythroid-derived 2-like 2 (Nrf2) protein was substantially increased in cells undergoing sphere formation. We noticed that expression of Bmi-1 was inhibited after introduction of Nrf2 short interfering RNA into MCF-7 mammosphere cells. Silencing of Nrf2 expression suppressed the xenograft growth of subcutaneously or orthotopically injected human breast cancer cells. Innovation: Association between Nrf2 and self-renewal signaling in CSCs has been reported, but the underlying molecular mechanism remains largely unresolved. This study demonstrates the Nrf2-mediated signaling pathway in maintenance of reductive stress in breast CSCs. Conclusion: Nrf2 overactivation in breast CSCs upregulates GCLC expression and consequently enhances GSH biosynthesis with concurrent reduction in intracellular ROS accumulation, thereby provoking the reductive stress. The consequent upregulation of nuclear FoxO3a and its binding to the promoter of the gene encoding Bmi-1 account for the self-renewal activity of breast cancer stem-like cells and their growth in a xenograft mouse model.

Targeting Cancer Metabolism to Resensitize Chemotherapy: Potential Development of Cancer Chemosensitizers from Traditional Chinese Medicines

Cancer is a common and complex disease with high incidence and mortality rates, which causes a severe public health problem worldwide. As one of the standard therapeutic approaches for cancer therapy, the prognosis and outcome of chemotherapy are still far from satisfactory due to the severe side effects and increasingly acquired resistance. The development of novel and effective treatment strategies to overcome chemoresistance is urgent for cancer therapy. Metabolic reprogramming is one of the hallmarks of cancer. Cancer cells could rewire metabolic pathways to facilitate tumorigenesis, tumor progression, and metastasis, as well as chemoresistance. The metabolic reprogramming may serve as a promising therapeutic strategy and rekindle the research enthusiasm for overcoming chemoresistance. This review focuses on emerging mechanisms underlying rewired metabolic pathways for cancer chemoresistance in terms of glucose and energy, lipid, amino acid, and nucleotide metabolisms, as well as other related metabolisms. In particular, we highlight the potential of traditional Chinese medicine as a chemosensitizer for cancer chemotherapy from the metabolic perspective. The perspectives of metabolic targeting to chemoresistance are also discussed. In conclusion, the elucidation of the underlying metabolic reprogramming mechanisms by which cancer cells develop chemoresistance and traditional Chinese medicines resensitize chemotherapy would provide us a new insight into developing promising therapeutics and scientific evidence for clinical use of traditional Chinese medicine as a chemosensitizer for cancer therapy.

Insights into new mechanisms and models of cancer stem cell multidrug resistance

The acquisition of genetic alterations, clonal evolution, and the tumor microenvironment promote cancer progression, metastasis and therapy resistance. These events correspond to the establishment of the great phenotypic heterogeneity and plasticity of cancer cells that contribute to tumor progression and resistant disease. Targeting resistant cancers is a major challenge in oncology; however, the underlying processes are not yet fully understood. Even though current treatments can reduce tumor size and increase life expectancy, relapse and multidrug resistance (MDR) ultimately remain the second cause of death in developed countries. Recent evidence points toward stem-like phenotypes in cancer cells, promoted by cancer stem cells (CSCs), as the main culprit of cancer relapse, resistance (radiotherapy, hormone therapy, and/or chemotherapy) and metastasis. Many mechanisms have been proposed for CSC resistance, such as drug efflux through ABC transporters, overactivation of the DNA damage response (DDR), apoptosis evasion, prosurvival pathways activation, cell cycle promotion and/or cell metabolic alterations. Nonetheless, targeted therapy toward these specific CSC mechanisms is only partially effective to prevent or abolish resistance, suggesting underlying additional causes for CSC resilience. This article aims to provide an integrated picture of the MDR mechanisms that operate in CSCs' behavior and to propose a novel model of tumor evolution during chemotherapy. Targeting the pathways mentioned here might hold promise and reveal new strategies for future clinical therapeutic approaches.

Autophagy inhibition as a promising therapeutic target for laryngeal cancer

To identify the putative relevance of autophagy in laryngeal cancer, we performed an immunohistochemistry study to analyze the expression of the proteins involved in this process, namely, LC3, ATG5 and p62/SQSTM1. Additionally, Prostate tumor-overexpressed gene 1 protein (PTOV1) was included due to its potential relevance in laryngeal cancer. Moreover, as cancer resistance might involve autophagy in some circumstances, we studied the intrinsic drug resistance capacity of primary tumor cultures derived from 13 laryngeal cancer biopsies and their expression levels of LC3, ATG5, p62 and PTOV1. Overall, our results suggest that (i) cytoplasmic p62 and PTOV1 can be considered prognostic markers in laryngeal cancer, (ii) the acquisition of resistance seems to be related to PTOV1 and autophagy-related protein overexpression, (iii) by increasing autophagy, PTOV1 might contribute to resistance in this model and (iv) the expression of autophagy-related proteins could classify a subgroup of laryngeal cancer patients who will benefit from a therapy based upon autophagy inhibition. Our study suggests that autophagy inhibition with hydroxychloroquine could be a promising strategy for laryngeal cancer patients, particularly those patients with high resistance to the CDDP treatment that in addition have autophagy upregulation.