Diuretic Chinese medicine found to limit tumour growth
CM NEWS – A centuries-old traditional Chinese medicine used commonly as a diuretic and fever fighting drug has been newly discovered as being able to inhibit tumour growth in mice with cervical cancer.
Long kui (??, Solanum nigrum Linne) has been used in traditional Chinese medicine for centuries because of its diuretic and antipyretic effects. The present study was done at the College of Environmental and Chemical Engineering at the Yanshan University in Hebei, China.
The study examined the effect of the crude polysaccharides isolated from long kui on tumour growth.
What are polysaccharides? Polysaccharides (sometimes called glycans) are relatively complex carbohydrates.
They are polymers made up of many monosaccharides joined together by glycosidic linkages. They are therefore very large, often branched, molecules. They tend to be amorphous, insoluble in water, and have no sweet taste.
When all the constituent monosaccharides are of the same type they are termed homopolysaccharides; when more than one type of monosaccharide is present they are termed heteropolysaccharides.
Examples include storage polysaccharides such as starch and glycogen and structural polysaccharides such as cellulose and chitin.
The effect of long kui polysaccarides on a group of tumour-bearing mice with cervical cancer was observed after oral administration of long kui polysaccahrides for 12 days.
Analysis of the tumour inhibition mechanism indicated that the number of apoptotic tumour cells (cells died) increased significantly, i.e. more cancerous cells were killed.
Moreover, the expression of a gene Bcl-2 (B-cell lymphoma 2), which is believed to play a role in resisting conventional cancer treatment, dropped significantly. Mutated gene of p53, which originally is a tumour suppressor but its mutated form is found in most tumour types, also decreased.
On the other side of the token, the expression of cell-death promoting protein Bax increased.
What is Bcl-2 (B-cell lymphoma 2) gene? The Bcl-2 gene has been implicated in a number of cancers, including melanoma, breast, prostate, lung carcinomas, schizophrenia, and autoimmunity. It is also thought to be involved in resistance to conventional cancer treatment. This supports a role for decreased apoptosis in the pathogenesis of cancer.
Apoptosis plays a very important role in regulating a variety of diseases that have enormous social impacts. Bcl-2 is essential to the process of apoptosis because it suppresses the initiation of the cell-death process.
What is p53 gene? The p53 gene is a tumour suppressor gene, i.e., its activity stops the formation of tumours. If a person inherits only one functional copy of the p53 gene from their parents, they are predisposed to cancer and usually develop several independent tumours in a variety of tissues in early adulthood. This condition is rare, and is known as Li-Fraumeni syndrome. However, mutations in p53 are found in most tumour types, and so contribute to the complex network of molecular events leading to tumour formation. It is clear that p53 is just one component of a network of events that culminate in tumour formation.
What is more promising is that the long kui polysaccarides treatment can decrease the level of TNF-alpha, or tumour necrosis factor, in blood serum. These results indicated that the tumour growth inhibition of long kui polysaccarides might correlate with the reduction of TNF-alpha level of blood serum, which resulted in a massive necrosis (accidental death of cells) in tumour tissues and the up-regulation of Bax and down-regulation of Bcl-2 and mutant p53 gene expression, which triggered apoptosis in tumour cells.
What is TNF? Tumour necrosis factor is a protein produced by several of the body’s cell types, such as white blood cells, red blood cells, and other cells that line the blood vessels. It promotes the destruction of some types of cancer cells.
TNF is a type of cytokine released by white blood cells. Cytokines are a group of molecules that are released by many different cells to communicate with other cells and regulate the duration of an immune response.
There are many different kinds of cytokines, each with a different effect on specific target cells. Once a cell releases the cytokines, they bind to corresponding receptors located on target cells, thus causing a change to take place within the target cell.
Tumour necrosis factor is released by special white blood cells called macrophages. Although researchers are still investigating the exact mechanism by which TNF kills cancer cells, it is clear that TNF binds to receptors located on the surface of cancer cells, causing a change and then death of the cell. This was found to be true in animal models. As a result, researchers thought TNF might enhance the reaction of the human immune system to cancer cells.
In addition to tumour cell-killing activity, TNF-? has been noted for its role in the inflammatory response and the body’s resistance to pathogens.
The researchers conclude that long kui polysaccarides can be considered as a potential antitumour agent.
[Phytother Res. 2007 May 8]