Roxithromycin and clarithromycin, 14-membered ring macrolides, potentiate the antitumor activity of cytotoxic agents against mouse B16 melanoma cells

Clarithromycin effectively enhances doxorubicin-induced cytotoxicity and apoptosis in MCF7 cells through dysregulation of autophagy

PURPOSE

Use of autophagy inhibitors in combination with chemotherapy has become a novel chemotherapeutic strategy. In this study, we aimed to determine whether the effectiveness of doxorubicin (DOX) is augmented by clarithromycin (CAM) in MCF7 cells and the molecular mechanisms involved.

MATERIALS AND METHODS

Combined cytotoxicity of CAM and DOX was assessed by MTT assay and was analyzed using the Chou-Talalay's method. To clarify the underlying mechanisms, several factors, including apoptosis (Annexin V/propidium iodide staining), intracellular level of DOX (spectrofluorimetry) and P-glycoprotein activity (Rhodamin 123 efflux assay) were measured. In addition, autophagy was evaluated by intracellular labeling with anti-LC3II and LysoTrackerGreen (LTG) staining and analyzed by flowcytometry.

RESULTS

The anti-proliferation effect of DOX was synergistically enhanced by CAM in MCF7 cells and was associated with an increase in the apoptotic cell death. However, the intracellular level of DOX remained unchanged in the presence of CAM. Based on the findings, 100 μM of CAM did not exhibit any inhibitory effects on P-glycoprotein activity. Flow cytometric analysis indicated that DOX at IC₂₀ concentration induced the autophagy flux, as confirmed by the increased level of LC3II and LTG signals. Moreover, combined treatment with DOX and CAM resulted in more pronounced LTG signals, but no change in LC3II. These results indicate that CAM blocks the autophagy flux induced by DOX.

CONCLUSIONS

These findings suggest that suppression of autophagy by CAM may promote chemotherapeutic outcome in breast cancer. However, further investigations are needed to evaluate the application of CAM in adjuvant breast cancer therapy.

In vitro cytogenetic evaluation of the particular combination of flurbiprofen and roxithromycin

Flurbiprofen (FLB) (anti-inflammatory and analgesic drug) and roxithromycin (RXM) (antibiotic) were widely used in world wide. This study deals with investigation of genotoxicity, cytotoxicity, and oxidative stress effects of a particular combination of these drugs in human cultured lymphocytes. Also, DNA damaging-protective effects of combination of these drugs were analyzed on plasmid DNA. Human lymphocytes were treated with different concentrations (FLB + RXM; 10 μg/mL + 25 μg/mL, 15 μg/mL + 50 μg/mL, and 20 μg/mL + 100 μg/mL) of the drugs following by study of their genotoxic and cytotoxic effects by analysis of cytokinesis-block micronucleus test and nuclear division index, respectively. The effect of the combination in aspect of anti-oxidative and DNA damaging activity was evaluated on Pet-22b plasmid. According to our results, the combination of FLB and RXM did not show a notable genotoxic effect on cells. Although each of the substances had been shown as a cytotoxic agent by previous researchers, in this research, the combination of these drugs did not exhibit any adverse effect on cell division. FLB had DNA protection effect against H₂O₂ while in combination with RXM had not the same effect on the plasmid.

Development of Novel Erythromycin Derivatives with Inhibitory Activity against Proliferation of Tumor Cells

In our continuing structure-activity relationship study of a new class of erythromycin A (EM-A) derivatives with antiproliferative activity, a new series of de(N-methyl) EM-A dimers jointed by a four-atom linker, -CH₂CH = CHCH₂-, were prepared and their antiproliferative activity against three human tumor cell lines was evaluated by MTT assay. The most active EM-A dimer, compound 1b, that carrying C6 methoxyl groups was further investigated and showed potent antiproliferative activity in six other human tumor cell lines. Flow cytometry analysis of 1b treated HeLa and MCF-7 cells indicated that the four-atom EM-A dimers induced the SubG₁ phase cell cycle arrest and cell apoptosis, in time- and dose-dependent manners. Further experiments including morphologic observation, DNA agarose gel electrophoresis, mitochondrial potential alternation and western blot analysis revealed that the antiproliferative mechanism may involve the induction of apoptosis in activating the mitochondrial pathway, and regulation of apoptotic proteins.

Repurposing Drugs in Oncology (ReDO)-clarithromycin as an anti-cancer agent

Clarithromycin (CAM) is a well-known macrolide antibiotic available as a generic drug. CAM is traditionally used for many types of bacterial infections, treatment of Lyme disease and eradication of gastric infection with Helicobacter pylori. Extensive preclinical and clinical data demonstrate a potential role for CAM to treat various tumours in combination with conventional treatment. The mechanisms of action underlying the anti-tumour activity of CAM are multiple and include prolonged reduction of pro-inflammatory cytokines, autophagy inhibition, and anti-angiogenesis. Here, we present an overview of the current preclinical (in vitro and in vivo) and clinical evidence supporting the role of CAM in cancer. Overall these findings justify further research with CAM in many tumour types, with multiple myeloma, lymphoma, chronic myeloid leukaemia (CML), and lung cancer having the highest level of evidence. Finally, a series of proposals are being made to further investigate the use of CAM in clinical trials which offer the greatest prospect of clinical benefit to patients.

Multimodal biopanning of T7 phage-displayed peptides reveals angiomotin as a potential receptor of the anti-angiogenic macrolide Roxithromycin

Roxithromycin (RXM) is a semi-synthetic fourteen-membered macrolide antibiotic that shows anti-angiogenic activity in solid tumors. In the present study, we conducted biopanning of T7 phage-displayed peptides either on a 96-well formatted microplate, a flow injection-type quartz-crystal microbalance (QCM) biosensor, or a cuvette-type QCM. RXM-selected peptides of different sequence, length and number were obtained from each mode of screening. Subsequent bioinformatics analysis of the RXM-selected peptides consistently gave positive scores for the extracellular domain (E458-T596) of angiomotin (Amot), indicating that this may comprise a binding region for RXM. Bead pull down assay and QCM analysis confirmed that RXM directly interacts with Amot via the screen-guided region, which also corresponds to the binding site for the endogenous anti-angiogenic inhibitor angiostatin (Anst). Thus, multimodal biopanning of T7PD revealed that RXM binds to the extracellular domain on Amot as a common binding site with Anst, leading to inhibition of angiogenesis-dependent tumor growth and metastasis. These data might explain the molecular basis underlying the mechanism of action for the anti-angiogenic activity of RXM.

Macrolide antibiotics block autophagy flux and sensitize to bortezomib via endoplasmic reticulum stress-mediated CHOP induction in myeloma cells

The specific 26S proteasome inhibitor bortezomib (BZ) potently induces autophagy, endoplasmic reticulum (ER) stress and apoptosis in multiple myeloma (MM) cell lines (U266, IM-9 and RPMI8226). The macrolide antibiotics including concanamycin A, erythromycin (EM), clarithromycin (CAM) and azithromycin (AZM) all blocked autophagy flux, as assessed by intracellular accumulation of LC3B-II and p62. Combined treatment of BZ and CAM or AZM enhanced cytotoxicity in MM cell lines, although treatment with either CAM or AZM alone exhibited almost no cytotoxicity. This combination also substantially enhanced aggresome formation, intracellular ubiquitinated proteins and induced the proapoptotic transcription factor CHOP (CADD153). Expression levels of the proapoptotic genes transcriptionally regulated by CHOP (BIM, BAX, DR5 and TRB3) were all enhanced by combined treatment with BZ plus CAM, compared with treatment with each reagent alone. Like the MM cell lines, the CHOP+/+ murine embryonic fibroblast (MEF) cell line exhibited enhanced cytotoxicity and upregulation of CHOP and its transcriptional targets with a combination of BZ and one of the macrolides. In contrast, CHOP-/- MEF cells exhibited resistance against BZ and almost completely canceled enhanced cytotoxicity with a combination of BZ and a macrolide. These data suggest that ER stress-mediated CHOP induction is involved in pronounced cytotoxicity. Simultaneously targeting two major intracellular protein degradation systems such as the ubiquitin-proteasome system by BZ and the autophagy-lysosome system by a macrolide antibiotic enhances ER stress-mediated apoptosis in MM cells. This result suggests the therapeutic possibility of using a macrolide antibiotic with a proteasome inhibitor for MM therapy.

Clarithromycin enhances bortezomib-induced cytotoxicity via endoplasmic reticulum stress-mediated CHOP (GADD153) induction and autophagy in breast cancer cells

The specific 26S proteasome inhibitor, bortezomib (BZ) potently induces apoptosis as well as autophagy in metastatic breast cancer cell lines such as MDA-MB-231 and MDA-MB-468. The combined treatment of clarithromycin (CAM) and BZ significantly enhances cytotoxicity in these cell lines. Although treatment with up to 100 μg/ml CAM alone had little effect on cell growth inhibition, the accumulation of autophagosomes and p62 was observed after treatment with 25 μg/ml CAM. This result indicated that CAM blocked autophagy flux. However, the combined treatment of BZ and CAM resulted in more pronounced autophagy induction, as assessed by increased expression ratios of LC3B-II to LC3B-I and clearance of intracellular p62, than treatment with BZ alone. This combination further enhanced induction of the pro-apoptotic transcription factor CHOP (CADD153) and the chaperone protein GRP78. Knockdown of CHOP by siRNA attenuated the death-promoting effect of BZ in MDA-MB-231 cells. A wild-type murine embryonic fibroblast (MEF) cell line also exhibited enhanced BZ-induced cytotoxicity with the addition of CAM, whereas a Chop knockout MEF cell line completely abolished this enhancement and exhibited resistance to BZ treatment. These data suggest that endoplasmic reticulum (ER)-stress mediated CHOP induction is involved in pronounced cytotoxicity by combining these reagents. Simultaneously targeting two major intracellular protein degradation pathways such as the ubiquitin-proteasome system by BZ and the autophagy-lysosome pathway by CAM may improve the therapeutic outcome in breast cancer patients via ER-stress mediated apoptosis.

Novel concepts in evaluating antimicrobial therapy for bacterial lung infections in patients with cystic fibrosis

Cystic fibrosis (CF) patients suffer typically from bacterial infections of their airways. Whilst current antibiotic-based treatment of these infections has brought much benefit to patients, it has been difficult to make either direct or indirect assessments of the in vivo efficacy of any specific treatment used. Traditional culture-based assessment has for example been rarely used to determine the direct impact of therapy on the bacteria in the airways. Instead, the "success" of a treatment is most often gauged through measures of respiratory and general health. New culture-independent approaches though are emerging that offer much promise here however in allowing a more comprehensive evaluation of antimicrobial efficacy. These new methods offer an opportunity to examine bacterial outcomes rather than host outcomes alone. Application of these novel techniques in a systematic way will lead to the rationalisation and, likely greater still individualisation, of therapy for CF patients. This review discusses host and microbiological factors that may influence antibiotic efficacy. Moreover, the degree to which the inherent complexity of CF respiratory infections complicates the process of determining treatment impact and the need to identify more robust microbiological outcome measures will also be reviewed.

Natural glycoconjugates with antitumor activity

Cancer is one of the major causes of death worldwide. As a consequence, many different therapeutic approaches, including the use of glycosides as anticancer agents, have been developed. Various glycosylated natural products exhibit high activity against a variety of microbes and human tumors. In this review we classify glycosides according to the nature of their aglycone (non-saccharidic) part. Among them, we describe anthracyclines, aureolic acids, enediyne antibiotics, macrolide and glycopeptides presenting different strengths and mechanisms of action against human cancers. In some cases, the glycosidic residue is crucial for their activity, such as in anthracycline, aureolic acid and enediyne antibiotics; in other cases, Nature has exploited glycosylation to improve solubility or pharmacokinetic properties, as in the glycopeptides. In this review we focus our attention on natural glycoconjugates with anticancer properties. The structure of several of the carbohydrate moieties found in these conjugates and their role are described. The structure–activity relationship of some of these compounds, together with the structural features of their interaction with the biological targets, are also reported. Taken together, all this information is useful for the design of new potential anti-tumor drugs.

The role of azithromycin in patients with cystic fibrosis

Interest in azithromycin in the management of patients with cystic fibrosis has grown over the last decade. Uniquely this drug has both antibacterial and immune modulating effects which appear to be the reason for its clinical benefit as proven in several well designed clinical studies. In this review we discuss the proposed mechanisms of action of azithromycin and review the evidence for its clinical effectiveness and safety in cystic fibrosis.

Macrolide antibiotics: current and future uses

After a long history of anti-infective therapeutic use, macrolide antibiotics have not yet given up all their secrets. Interest in their therapeutic potential in inflammatory diseases (possibly including non-infectious diseases) has generated abundant fundamental research and therapeutic trials worldwide. The main question regarding the future prospects of this class of drugs is whether some macrolides are beneficial in such settings because they modulate host inflammatory responses (and cellular targets) or rather because they eliminate a latent, unidentified pathogen which triggers chronic inflammation. However, no clearcut results have yet been obtained.

Anti-inflammatory effects of macrolide antibiotics

Macrolides are widely used as antibacterial drugs. Clinical and experimental data, however, indicate that they also modulate inflammatory responses, both contributing to the treatment of infective diseases and opening new opportunities for the therapy of other inflammatory conditions. Considerable evidence, mainly from in vitro studies, suggests that leukocytes and neutrophils in particular, are important targets for modulatory effects of macrolides on host defense responses. This underlies the use of the 14-membered macrolide erythromycin for the therapy of diffuse panbronchiolitis. A variety of other inflammatory mediators and processes are also modulated by macrolides, suggesting that the therapeutic indications for these drugs may be extended significantly in future.