Bacterium from dirt could fight melanoma

Posted Jan 9, 2018 by Tim Sandle
Scientists have identified a type of organism found in the soil which has the potential to induce the death of melanoma cells. This is through a molecule made as a metabolite from the organism.
Another view of St Ives  showing its beach and cove.
Another view of St Ives, showing its beach and cove.
The organism in question is Streptomyces bottropensis. This organism is commonly found in the soil. Over 500 species of Streptomyces bacteria have been described, although not all have therapeutic value; however, a number of species produce over two-thirds of the clinically useful antibiotics of natural origin.
Skin cancer is a condition of global medical importance and there are over 80,000 new cases of melanoma diagnosed each year in the U.S. alone, based on data from the U.S. Centers for Disease Control and Prevention (CDC).
With the new finding, researchers Professor Sandra Loesgen and Terence Bradshaw have discovered the natural chemical mensacarcin, produced by the bacterium, is capable of attacking the mitochondria with a melanoma cell. The molecule is a secondary metabolite, and can be obtained in large amounts from its producing organism.
Farmer working on his field of oats.
Farmer working on his field of oats.
The mitochondria are organelles in cells which generate power. Without functioning mitochondria, cells cannot live. This makes mitochondria a potential therapeutic target. This can happen because the mitochondria of cancer cells have a different structure to mitochondria located in normal (that is, non-cancerous cells).
Speaking with the science website Laboratory Roots, Professor Loesgen said: “Mensacarcin has potent anticancer activity, with selectivity against melanoma cells.”
She added: “It shows powerful anti-proliferative effects in all tested cancer cell lines in the U.S. Cancer Institute's cell line panel, but inhibition of cell growth is accompanied by fast progression into cell death in only a small number of cell lines, such as melanoma cells."
The researchers wanted to know how mensacarcin acted on melanoma on the subcellular level, so they created a fluorescent probe to follow it. "The probe was localized to mitochondria within 20 minutes of treatment," she revealed. "The localization together with mensacarcin's unusual metabolic effects in melanoma cells provide evidence that mensacarcin targets mitochondria."
By Nephron via Wikimedia Commons
Based on the bioenergetic changes, the researchers showed how mensacarcin can quickly disrupt the function of the cancerous cell mitochondria. This stops the production of energy and triggering what the researchers describe as mitochondrial dysfunction and eventual cell apoptosis (cell death).
The findings have been reported to the Journal of Biological Chemistry. The article is titled “The natural product mensacarcin induces mitochondrial toxicity and apoptosis in melanoma cells.”