The role of plants and their substances has tremendously increased in cancer treatment. More and more doctors and scientists are looking for new compounds focusing on plants used in traditional medicine.
Many chemotherapies to fight cancer applied in modern medicine are natural products or were developed on the basis of natural substances.
For instance, taxanes used in prostate and breast cancer treatment are made from yew trees.
The popular periwinkle plant, which grows along the ground of many front yards, is the source of vinca alkaloids that are effective, for example, against malignant lymphomas. The modern anti-cancer drugs topotecan and irinotecan are derived from a constituent of the Chinese Happy Tree.
In search for active ingredients, Professor Dr. Thomas Efferth of the DKFZ has been concentrating on herbal remedies from traditional Chinese medicine with particularly well-documented application range.
Efferth launched a systematic compound search in 76 Chinese medicinal plants that are believed to be effective against malignant tumors and other growths.
Extracts from 18 of the plants under investigation were found to substantially suppress the growth of a cancer cell line in the culture dish.
"With this success rate of about 24 percent, we are way above the results that could be expected from searching through large chemical substance libraries," Efferth said.
The research team proceeded to chemically separate, step by step, all active extracts, tracing the active component after each separation step by cell tests.
The chemical structure of the compounds is analyzed using nuclear magnetic resonance and mass spectroscopy.
"We are combining natural substance research with advanced analytical and molecular-biological methods. Plant constituents that seem particularly promising are immediately subjected to further tests," Efferth said.
Such constituents include, for example, substances derived from the Rangoon Creeper, an ornamental plant with red flowers, or from Red-Root Sage.
The substances were found to suppress the growth of a specific tumor cell line that is particularly resistant to many commonly used cytotoxins due to overproduction of a transport protein in the cell wall. In contrast, a whole range of standard anti-cancer drugs fail to be effective against this cell.
"We can expect to find many interesting, yet unknown working mechanisms among the chemically highly diverse natural substances. Currently, we are aligning the effectiveness of the substances on 60 different cancer cell lines with the gene activity profiles of these cells. Thus, we can determine the exact gene products that are the cellular targets of our compounds. Thereby, it may be possible to discover whole new Achilles' heels of the cancer cell," Efferth said.