Melatonin decreases in vitro viability and migration of spheres derived from CF41.Mg canine mammary carcinoma cells

Effect of Melatonin on Chemoresistance Exhibited by Spheres Derived from Canine Mammary Carcinoma Cells

Mammary cancer is a frequent disease in female dogs, where a high proportion of cases correspond to malignant tumors that may exhibit drug resistance. Within the mammary tumor microenvironment, there is a cell subpopulation called cancer stem cells (CSCs), which are capable of forming spheres in vitro and resisting anti-tumor treatments, partly explaining the recurrence of some tumors. Previously, it has been described that spheres derived from canine mammary carcinoma cells CF41.Mg and REM 134 exhibit stemness characteristics. Melatonin has shown anti-tumor effects on mammary tumor cells; however, its effects have been poorly evaluated in canine mammary CSCs. This study aimed to analyze the effect of melatonin on the chemoresistance exhibited by stem-like neoplastic cells derived from canine mammary carcinoma to cytotoxic drugs such as doxorubicin and mitoxantrone. CF41.Mg and REM 134 cells were cultured in high-glucose DMEM supplemented with fetal bovine serum and L-glutamine. The spheres were cultured in ultra-low attachment plates in DMEM/F12 medium without fetal bovine serum and with different growth factors. The CD44+/CD24-/low phenotype was analyzed by flow cytometry. The viability of sphere-derived cells (MTS reduction) was studied in the presence of melatonin (0.1 or 1 mM), doxorubicin, mitoxantrone, and luzindole. In addition, the gene (RT-qPCR) of the multidrug resistance bombs MDR1 and ABCG2 were analyzed in the presence of melatonin. Both cell types expressed the MT1 gene, which encodes the melatonin receptor MT1. Melatonin 1 mM does not modify the CD44+/CD24-/low phenotype; however, the hormone reduced viability (p < 0.0001) only in CF41.Mg spheres, without inducing an additive effect when co-incubated with cytotoxic drugs. These effects were independent of the binding of the hormone to its receptor MT1, since, by pharmacologically inhibiting them, the effect of melatonin was not blocked. In CF41.Mg spheres, the relative gene expression of ABCG2 and MDR1 was decreased in response to the hormone (p < 0.001). These results indicate that melatonin negatively modulates the cell survival of spheres derived from CF41.Mg cells, in a way that is independent of its MT1 receptor. These effects did not counteract the resistance to doxorubicin and mitoxantrone, even though the hormone negatively regulates the gene expression of MDR1 and ABCG2.

Melatonin attenuates dimethyl sulfoxide- and Zika virus-induced degeneration of porcine induced neural stem cells

Domestic pigs have become increasingly popular as a model for human diseases such as neurological diseases. Drug discovery platforms have increasingly been used to identify novel compounds that combat neurodegeneration. Currently, bioactive molecules such as melatonin have been demonstrated to offer a neuroprotective effect in several studies. However, a neurodegenerative platform to study novel compounds in a porcine model has not been fully established. In this study, characterized porcine induced neural stem cells (iNSCs) were used for evaluation of the protective effect of melatonin against chemical and pathogenic stimulation. First, the effects of different concentrations of melatonin on the proliferation of porcine iNSCs were studied. Second, porcine iNSCs were treated with the appropriate concentration of melatonin prior to induced degeneration with dimethyl sulfoxide or Zika virus (ZIKV). The results demonstrated that the percentages of Ki67 expression in porcine iNSCs cultured in 0.1, 1, and 10 nM melatonin were not significantly different from that in the control groups. Melatonin at 1 nM protected porcine iNSCs from DMSO-induced degeneration, as confirmed by a dead cell exclusion assay and mitochondrial membrane potential (ΔΨm) analysis. In addition, pretreatment with melatonin reduced the percentage of dead porcine iNSCs after ZIKV infection. Melatonin increased the ΔΨm, resulting in a decrease in cell degeneration. However, pretreatment with melatonin was unable to suppress ZIKV replication in porcine iNSCs. In conclusion, the present study demonstrated the anti-degenerative effect of melatonin against DMSO- and ZIKV-induced degeneration in porcine iNSCs.