The complex interaction of anti-canerous substances in mushroom Ganoderma lucidum (ling zhi, picture) and green tea has been shown to suppress progression and invasiveness of metastatic breast cancers, according to a study done at the Cancer Research Laboratory, Methodist Research Institute, Indianapolis. Epidemiological studies have suggested that consumption of green tea may decrease the risk of a variety of cancers. In addition, Ganoderma lucidum has been used for the promotion of health, longevity and treatment of cancer in traditional Chinese medicine.
In the present study, the researchers showed that that extract from green tea increased the anticancer effect of Ganoderma lucidum extract on cell proliferation as well as colony formation of breast cancer cells.
This effect was mediated by the down-regulation of expression of oncogene c-myc in breast cancer cells (MDA-MB-231 cells), i.e. desensitized genes that increase the malignancy of a tumour cell.
Down regulation is the process by which a cell decreases the number of receptors to a given hormone or neurotransmitter to reduce its sensitivity to this molecule. This is a locally acting negative feedback mechanism. An increase of receptors is called up regulation.
What is oncogene c-myc? c-myc is a proto-oncogene. An oncogene is a modified gene, or a set of nucleotides that codes for a protein, that increases the malignancy of a tumour cell. Some oncogenes, usually involved in early stages of cancer development, increase the chance that a normal cell develops into a tumour cell, possibly resulting in cancer. The proto-oncogene c-myc may play a role in controlling the growth and division of normal cells, and abnormalities of the gene have been implicated in the genesis of a substantial variety of human tumours.
c-myc is expressed in proliferating cells in the body, such as keratinocytes, hepatocytes, bone marrow cells, fibroblasts, and vascular smooth muscle cells. It is repressed when these cells withdraw from the cell cycle.
Although individual extract from green tea and Ganoderma lucidum extract independently inhibited adhesion, migration and invasion of the breast cancer cells, their combination demonstrated a synergistic effect, which was mediated by the suppression of secretion of urokinase plasminogen activator (uPA) from breast cancer cells, which plays an important role in malignant tumour progression.
What is urokinase plasminogen activator receptor (uPAR)? uPAR is a cell-surface molecule that urokinase plasminogen activator (uPA) binds to. When bound to uPAR, uPA is activated converting plasminogen into plasmin. Plasmin digests fibrin, allowing room for endothelial tube formation. The urokinase plasminogen activator system plays a central role in malignant tumour progression.
The researchers suggest combined green tea and G. lucidum extracts has the potential to suppress growth and invasiveness of metastatic breast cancers.
[Int J Oncol. 2007 Apr30(4):963-9.]
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