MG-Pe: A Novel Galectin-3 Ligand with Antimelanoma Properties and Adjuvant Effects to Dacarbazine

Melanoma is a highly metastatic and rapidly progressing cancer, a leading cause of mortality among skin cancers. The melanoma microenvironment, formed from the activity of malignant cells on the extracellular matrix and the recruitment of immune cells, plays an active role in the development of drug resistance and tumor recurrence, which are clinical challenges in cancer treatment. These tumoral metabolic processes are affected by proteins, including Galectin-3 (Gal-3), which is extensively involved in cancer development. Previously, we characterized a partially methylated mannogalactan (MG-Pe) with antimelanoma activities. In vivo models of melanoma were used to observe MG-Pe effects in survival, spontaneous, and experimental metastases and in tissue oxidative stress. Analytical assays for the molecular interaction of MG-Pe and Gal-3 were performed using a quartz crystal microbalance, atomic force microscopy, and contact angle tensiometer. MG-Pe exhibits an additive effect when administered together with the chemotherapeutic agent dacarbazine, leading to increased survival of treated mice, metastases reduction, and the modulation of oxidative stress. MG-Pe binds to galectin-3. Furthermore, MG-Pe antitumor effects were substantially reduced in Gal-3/KO mice. Our results showed that the novel Gal-3 ligand, MG-Pe, has both antitumor and antimetastatic effects, alone or in combination with chemotherapy.

Biocompatible gum arabic-gold nanorod composite as an effective therapy for mistreated melanomas

Advanced melanoma patients that are not included in common genetic classificatory groups lack effective and safe therapeutic options. Chemotherapy and immunotherapy show unsatisfactory results and devastating adverse effects for these called triple wild-type patients. New approaches exploring the intrinsic antitumor properties of gold nanoparticles might reverse this scenario as a safer and more effective alternative. Therefore, we investigated the efficacy and safety of a composite made of gum arabic-functionalized gold nanorods (GA-AuNRs) against triple wild-type melanoma. The natural polymer gum arabic successfully stabilized the nanorods in the biological environment and was essential to improve their biocompatibility. In vivo results obtained from treating triple wild-type melanoma-bearing mice showed that GA-AuNRs remarkably reduced primary tumor growth by 45%. Furthermore, GA-AuNRs induced tumor histological features associated with better prognosis while also reducing superficial lung metastasis depth and the incidence of intrapulmonary metastasis. GA-AuNRs' efficacy comes from their capacity to reduce melanoma cells ability to invade the extracellular matrix and grow into colonies, in addition to a likely immunomodulatory effect induced by gum arabic. Additionally, a broad safety investigation found no evidence of adverse effects after GA-AuNRs treatment. Therefore, this study unprecedentedly reports GA-AuNRs as a potential nanomedicine for advanced triple wild-type melanomas.

Endophytic actinobacteria of Hymenachne amplexicaulis from the Brazilian Pantanal wetland produce compounds with antibacterial and antitumor activities

The increase in the number of deaths from infections caused by multidrug-resistant bacteria and cancer diseases highlights the need for new molecules with biological activity. Actinobacteria represent a potential source of new compounds, as these microorganisms have already produced a great diversity of clinically employed antibiotics. Endophytes from unexplored biomes, such as the Pantanal (the largest wetland in the world), can be a source of new molecules. Hymenachne amplexicaulis is among the unexplored native plants of the Pantanal in terms of its endophytic community. This plant is considered a weed in other countries due to its ability to adapt and compete with native plants, and there is evidence to suggest that the endophytic community of H. amplexicaulis plays an important role in this competitiveness. To explore its therapeutic potential, the present study isolated, identified (using partial sequence of the 16S rDNA) and bioprospected H. amplexicaulis endophytic actinobacteria. Ten isolates belonging to the genera Streptomyces, Microbispora, Leifsonia, and Verrucosispora were obtained from root fragments. The susceptibility profile of the isolates to the different classes of antibiotics was evaluated, with 80 % of the isolates showing resistance to the antibiotics Nalidixic Acid, Ampicillin, Chloramphenicol, Oxacillin, and Rifampicin. To assess antibacterial and antitumor activities, methanolic extracts were obtained by fermentation in SG culture medium at 36 °C at 180 rpm for 10 days. The extract produced from the S. albidoflavus CMRP4854 isolate was the only one to show activity against the Gram-negative bacterium Acinetobacter baumanii. Due to the great clinical importance of this pathogen and the difficulty in obtaining active compounds against it, the CMRP4854 isolate should be further investigated for the identification of active compounds and mode of action. We also emphasize the results obtained by the extract of the isolates Streptomyces albidoflavus CMRP4852 and Verrucosispora sp. CMRP4860 that presented antibacterial effect against Methicilin-resistant Staphylococcus aureus (MRSA) (MIC: 1.5 μg/mL and 13 μg/mL, respectively) and Vancomycin-resistant Enterococcus (VRE) (MIC: 40 μg/mL for both extracts). Extracts (200 μg/mL) of these two endophytes also showed selective cytotoxicity action against murine B16-F10 melanoma cells. However, the CMRP4852 extract also affected the density of normal cells. Due to these results, the crude extract of isolate CMRP4860 Verrucosispora sp., which was the only one that presented cytotoxicity and reduced cell density only in tumor cells, was selected for subsequent analysis involving scale-up fermentation of the CMRP4860 resulting in 9 fractions that were tested against both bacteria and tumor cells, with particular fractions showing promise and meriting further investigation. Taken together, the results of this study not only show for the first time that the endophytic community of H. amplexicaulis actinobacteria can produce secondary metabolites that potentially possess important antibacterial and cytotoxic properties, but also reinforce the pressing need to conserve biomes such as the Brazilian Pantanal.

Non-Cytotoxic Sulfated Heterorhamnan from Gayralia brasiliensis Green Seaweed Reduces Driver Features of Melanoma Metastatic Progression

Melanoma is a form of skin cancer with high mortality owing to its fast progression and metastatic capacity. The treatments available nowadays are only palliative in advanced stages of the disease. Thus, alternative therapies for cancer treatment are in demand, and molecules from natural sources, such as polysaccharides, could represent new possible therapeutic approaches. Polysaccharides of freshwater and marine algae with biological activities, such as antitumor properties, are greatly reported in the scientific literature. In the present study, a sulfated heterorhamnan obtained from the green seaweed Gayralia brasiliensis (Gb1 fraction) was chemically characterized and its biological activities in the B16-F10 murine melanoma cell line were evaluated. The Gb1 polysaccharidic fraction tested concentrations presented low or absence of cytotoxicity to B16-F10 cells and neither cell proliferation nor cell cycle were altered. Interestingly, Gb1 treatment decreased B16-F10 cells migration and invasion capabilities and CD44 labeling, showing to be a promising compound for further in vitro and in vivo antitumor studies.

The aminoglycoside antibiotic gentamicin is able to alter metabolic activity and morphology of MDCK-C11 cells: a cell model of intercalated cells

It is well known that the aminoglycoside antibiotic gentamicin is capable of causing damage to kidney cells. Given the known involvement of Ca²⁺ in the nephrotoxic action of gentamicin, the purpose of this study was to establish a relationship between the concentration of intracellular Ca²⁺ ([Ca²⁺]_i) and cellular cytotoxicity using MDCK-C11 cells, a clone that has several properties that resemble those of intercalated cells of the distal nephron. Changes in [Ca²⁺]_i was determined using fluorescence microscopy. Cell viability was evaluated by the neutral red method, and cell cytotoxicity by the MTT method. The [Ca²⁺]_i gradually increased when cells were exposed to 0.1 mM gentamicin for 10, 20, and 30 min. The presence of extracellular Ca²⁺ was found to be necessary to stimulate the increase in [Ca²⁺]_i induced by gentamicin, since this stimulus disappeared by using 1.8 mM EGTA (a Ca²⁺ chelator). Morphological changes were observed with scanning electron microscopy in epithelial cells exposed to the antibiotic. Furthermore, with the MTT method, a decrease in metabolic activity induced by gentamicin was observed, which indicates a cytotoxic effect. In conclusion, gentamicin was able to alter [Ca²⁺]_i, change the morphology of MDCK-C11 cells, and promote cytotoxicity.