DISCUSSION

These preliminary results are encouraging, showing that the plant extracts from CED Tech Health Ltd. do contain cytotoxic substances that have differential effects against several human tumor cell lines examined.

One leukemia cell line, CEM, was included in the tumor panel and found to be the most sensitive cell line. Some of the solid tumor cell line panel showed appreciable sensitivity while others showed marked resistance. This data indicates that the cytotoxic substances in the plant extracts are not necessarily just anti-leukemia agents.

The cellular or molecular target of these plant compounds may not be restricted to any one type of cancer.

The additional information on the cytotoxicity of these plant extracts in tumor cells known to be multi-drug resistant (MDR) is very interesting. Our data showed that in the MDR tumor cells, all the plant extracts tested were nearly as potent as in the drug-sensitive parent cell line. Therefore, the active substances in these plant extracts would not be subject to elimination from tumor cells due to an over-expression of the MDR gene, thereby reducing its effective intracellular concentration. The active plant extract components do not appear to resemble many conventional drugs that have proven limited in their efficiency due to clinical drug resistance. The importance of this finding can be appreciated when one realizes that even the latest "successful" anticancer drug discovery, taxol (which is a natural plant product), can be limited in its efficacy in cancers that have become multi-drug resistant.