Non-Polar Myxococcus fulvus KYC4048 Metabolites Exert Anti-Proliferative Effects via Inhibition of Wnt/ß-Catenin Signaling in MCF-7 Breast Cancer Cells.

The Wnt/ß-catenin signaling pathway is involved in breast cancer and Myxococcus fulvus KYC4048 is a myxobacterial strain that can produce a variety of bioactive secondary metabolites. Although a previous study revealed that KYC4048 metabolites exhibit anti-proliferative effects on breast cancer, the biochemical mechanism involved in their effects remains unclear. In the present study, KYC4048 metabolites were separated into polar and non-polar (ethyl acetate and n-hexane) fractions via liquid-liquid extraction. The effects of these polar and non-polar KYC4048 metabolites on the viability of breast cancer cells were then determined by MTT assay. Expression levels of Wnt/ß-catenin pathway proteins were determined by Western blot analysis. Cell cycle and apoptosis were measured via fluorescence-activated cell sorting (FACS). The results revealed that non-polar KYC4048 metabolites induced cell death of breast cancer cells and decreased expression levels of WNT2B, ß-catenin, and Wnt target genes (c-Myc and cyclin D1). Moreover, the n-hexane fraction of non-polar KYC4048 metabolites was found most effective in inducing apoptosis, necrosis, and cell cycle arrest, leading us to conclude that it can induce apoptosis of breast cancer cells through the Wnt/ß-catenin pathway. These findings provide evidence that the n-hexane fraction of non-polar KYC4048 metabolites can be developed as a potential therapeutic agent for breast cancer via inhibition of the Wnt/ß-catenin pathway.

Effects of Myxococcus fulvus KYC4048 Metabolites on Breast Cancer Cell Death.

Using MCF7 breast cancer cells, we tested the anticancer activity of metabolites from 130 strains of myxobacteria newly isolated in South Korea. Of these, three strains whose metabolites had high anticancer activity and low cell toxicity were selected and identified by their fruiting body morphology, cell morphology, and 16S rRNA sequence. Strains KYC4030 and KYC4048 were determined to be Myxococcus fulvus, whereas strain KYC4081 was identified as Corallococcus coralloides. We found that metabolites of M. fulvus KYC4048 demonstrated no toxicity in normal cells but specifically induced cancer cell death by suppressing the expression of WNT2B. This discovery highlights the value of assessing the metabolic and biomedical potential of myxobacteria, even those that are already known but were isolated from new areas, and the possible use of metabolites from M. fulvus KYC4048 in cancer treatment.

Two new ring-contracted congeners of rhizopodin illustrate significance of the ring moiety of macrolide toxins on the actin disassembly-mediated cytotoxicity.

Two new cytotoxic dilactones, bisisorhizopodin (1) and isorhizopodin (2), together with known divalent actin depolymerizer rhizopodin (3), were isolated from the culture broth of a myxobacterium Myxococcus stipitatus. Spectroscopic analyses established that 1 and 2 are doubly and singly acyl-migrated isomers of 3, respectively, and comparison of their cytotoxicity revealed gradual decrease in the activity as the size of the ring contracted. Because the side chains of macrolide toxins uniformly block the contact between the actin protomers, the present result demonstrates substantial contribution of structurally diverse rings to the affinity of macrolide toxins for its target protein.

Myxotyrosides A and B, Unusual rhamnosides from Myxococcus sp.

Myxobacteria are gliding bacteria of the delta-subdivision of the Proteobacteria and known for their unique biosynthetic capabilities. Two examples of a new class of metabolites, myxotyrosides A (1) and B (2), were isolated from a Myxococcus sp. The myxotyrosides have a tyrosine-derived core structure glycosylated with rhamnose and acylated with unusual fatty acids such as (Z)-15-methyl-2-hexadecenoic and (Z)-2-hexadecenoic acid. The fatty acid profile of the investigated Myxococcus sp. (strain 131) is that of a typical myxobacterium with a high similarity to those described for M. fulvus and M. xanthus, with significant concentrations of neither 15-methyl-2-hexadecenoic acid nor 2-hexadecenoic acid being detected.

KR025, a new cytotoxic compound from Myxococcus fulvus.

A new bithiazole, KR-025 (1), was isolated from Myxococcus fulvus. Its structure was elucidated by spectroscopic analysis. In addition to 1, the strain produced relatively large quantities of a second, closely related antibiotic, myxothiazol. These compounds demonstrated potent cytotoxicity against human tumor cells.

Further characterization and in situ localization of chain-like aggregates of the gliding bacteria Myxococcus fulvus and Myxococcus xanthus.

For the first time, chain-like aggregates, called "strands," have been enriched from crude cell wall preparations of liquid-grown vegetative cells of two strains of Myxococcus xanthus. These strands are highly isomorphic to macromolecular structures, previously described for Myxococcus fulvus (Lünsdorf and Reichenbach, J. Gen. Microbiol. 135:1633-1641, 1989). The strands are morphologically composed of ring elements, consisting of six or more peripheral protein masses and possibly three small central masses. The ring elements are linked by two parallel strings of filamentous proteins, called elongated elements, which keep the ring elements at a constant distance. The overall dimensions of the ring elements are 16.6 +/- 1.0 nm (n = 55) for M. xanthus Mx x48 and 16.4 +/- 1.5 nm (n = 37) for M. xanthus DK 1622. The distance between the ring elements, as a measure of the length of the elongated elements, is 16.6 +/- 1.1 nm (n = 59) for strain Mx x48 and 15.5 +/- 0.6 nm (n = 41) for strain DK 1622. Characteristically, the strands and oligomeric forms thereof show a strict association with the outer membrane. In situ studies of freeze-fractured cells of M. fulvus showed ring elements, isomorphic to those described for M. xanthus, within the periplasm; they appeared in parallel rows just below the outer membrane but not in direct contact with the cytoplasmic membrane. A three-dimensional model summarizes the morphological data. It is hypothesized that the chain-like strands, as building blocks of a more complex belt-like continuum, represent the peripheral part of the gliding machinery, which transforms membrane potential energy into mechanical work.

Rhizopodin, a new compound from Myxococcus stipitatus (myxobacteria) causes formation of rhizopodia-like structures in animal cell cultures. Production, isolation, physico-chemical and biological properties.

A new cytostatic compound, rhizopodin, was isolated from the culture broth of the myxobacterium, Myxococcus stipitatus. The compound inhibited growth of various animal cell cultures without killing the cells. The ID50, measured by an MTT assay, was 12 approximately 30 ng/ml, depending on the cell line. Especially cells growing fibroblast-like showed typical morphological changes. They became larger and within hour formed long branching and reticular runners. These morphological changes were irreversible. Rhizopodin suppresses bleb formation in K-562 cells, and therefore could act by interacting with protein phosphorylation.