Unravelling the Therapeutic Potential of Antibiotics in Hypoxia in a Breast Cancer MCF-7 Cell Line Model.

Antibiotics inhibit breast cancer stem cells (CSCs) by suppressing mitochondrial biogenesis. However, the effectiveness of antibiotics in clinical settings is inconsistent. This inconsistency raises the question of whether the tumor microenvironment, particularly hypoxia, plays a role in the response to antibiotics. Therefore, the goal of this study was to evaluate the effectiveness of five commonly used antibiotics for inhibiting CSCs under hypoxia using an MCF-7 cell line model. We assessed the number of CSCs through the mammosphere formation assay and aldehyde dehydrogenase (ALDH)-bright cell count. Additionally, we examined the impact of antibiotics on the mitochondrial stress response and membrane potential. Furthermore, we analyzed the levels of proteins associated with therapeutic resistance. There was no significant difference in the number of CSCs between cells cultured under normoxic and hypoxic conditions. However, hypoxia did affect the rate of CSC inhibition by antibiotics. Specifically, azithromycin was unable to inhibit sphere formation in hypoxia. Erythromycin and doxycycline did not reduce the ratio of ALDH-bright cells, despite decreasing the number of mammospheres. Furthermore, treatment with chloramphenicol, doxycycline, and tetracycline led to the overexpression of the breast cancer resistance protein. Our findings suggest that hypoxia may weaken the inhibitory effects of antibiotics on the breast cancer model.

Tuning the Envelope Structure of Enzyme Nanoreactors for In Vivo Detoxification of Organophosphates.

Encapsulated phosphotriesterase nanoreactors show their efficacy in the prophylaxis and post-exposure treatment of poisoning by paraoxon. A new enzyme nanoreactor (E-nRs) containing an evolved multiple mutant (L72C/Y97F/Y99F/W263V/I280T) of Saccharolobus solfataricus phosphotriesterase (PTE) for in vivo detoxification of organophosphorous compounds (OP) was made. A comparison of nanoreactors made of three- and di-block copolymers was carried out. Two types of morphology nanoreactors made of di-block copolymers were prepared and characterized as spherical micelles and polymersomes with sizes of 40 nm and 100 nm, respectively. The polymer concentrations were varied from 0.1 to 0.5% (w/w) and enzyme concentrations were varied from 2.5 to 12.5 µM. In vivo experiments using E-nRs of diameter 106 nm, polydispersity 0.17, zeta-potential -8.3 mV, and loading capacity 15% showed that the detoxification efficacy against paraoxon was improved: the LD50 shift was 23.7xLD50 for prophylaxis and 8xLD50 for post-exposure treatment without behavioral alteration or functional physiological changes up to one month after injection. The pharmacokinetic profiles of i.v.-injected E-nRs made of three- and di-block copolymers were similar to the profiles of the injected free enzyme, suggesting partial enzyme encapsulation. Indeed, ELISA and Western blot analyses showed that animals developed an immune response against the enzyme. However, animals that received several injections did not develop iatrogenic symptoms.

Quinazoline Ligands Induce Cancer Cell Death through Selective STAT3 Inhibition and G-Quadruplex Stabilization.

The signal transducer and activator of transcription 3 (STAT3) protein is a master regulator of most key hallmarks and enablers of cancer, including cell proliferation and the response to DNA damage. G-Quadruplex (G4) structures are four-stranded noncanonical DNA structures enriched at telomeres and oncogenes' promoters. In cancer cells, stabilization of G4 DNAs leads to replication stress and DNA damage accumulation and is therefore considered a promising target for oncotherapy. Here, we designed and synthesized novel quinazoline-based compounds that simultaneously and selectively affect these two well-recognized cancer targets, G4 DNA structures and the STAT3 protein. Using a combination of in vitro assays, NMR, and molecular dynamics simulations, we show that these small, uncharged compounds not only bind to the STAT3 protein but also stabilize G4 structures. In human cultured cells, the compounds inhibit phosphorylation-dependent activation of STAT3 without affecting the antiapoptotic factor STAT1 and cause increased formation of G4 structures, as revealed by the use of a G4 DNA-specific antibody. As a result, treated cells show slower DNA replication, DNA damage checkpoint activation, and an increased apoptotic rate. Importantly, cancer cells are more sensitive to these molecules compared to noncancerous cell lines. This is the first report of a promising class of compounds that not only targets the DNA damage cancer response machinery but also simultaneously inhibits the STAT3-induced cancer cell proliferation, demonstrating a novel approach in cancer therapy.