Page 12 - Science Focus (issue 15)

Taxol — The Pathway to Cancer Treatment?

紫杉醇 ─ 從自然而來的癌症良藥？

A major breakthrough in Taxol synthesis was genes from the genus Taxus into microorganisms
made in the late 1980s, when Polysciences Inc. such as the bacterium Escherichia coli [6] and
proposed a method of sustainable, large-scale various fungi [9, 10].
production. This involved the isolation of a natural With the help of scientists from multiple
precursor to Taxol, called 10-deacetylbaccatin disciplines, Taxol has gone from being extremely
3
III, from the more easily cultivated and abundant scarce, and possibly endangering Pacific yew trees;
European yew tree, Taxus baccata, and without to now being produced efficiently by fermentation
needing to kill the trees [3]. 10-Deacetylbaccatin III and semisynthesis, and is being prescribed
could then be converted to Taxol in a relatively easy worldwide for chemotherapy to treat breast,
4
manner, without synthesizing from scratch. Overall, ovarian and lung cancers, at a price of around
this approach, known as semisynthesis, had a 50- US$ 4 900 per patient [11]. These approaches in
5
fold increase in purification yield, and is far more the Taxol story may be extended to other herbal
renewable and environmentally friendly compared drug molecules, providing opportunities to make
to extracting Taxol directly from the Pacific yew [8].
treatments more readily available and affordable.
Further advancements in biotechnology
enabled scientists to make attempts to produce
Taxol or closely related precursors from other non-
plant species. Researchers have now managed
to successfully engineer microorganisms that can
produce Taxol, by inserting the Taxol-producing

1 Tumor: An irregular mass of tissue formed by the uncontrollable
growth and division of cells. This is the prominent feature of most
type of cancers.
2 Active ingredient: A substance in a pharmaceutical or medicinal
product that makes the product biologically active. It is believed
that there are some active ingredients in traditional Chinese
medicines that enabled them to exert certain biological effects,
e.g. ginsenosides in ginseng.
3 Precursor: A starting compound (usually having a simpler
structure) that can be converted into the desired final compound
through a series of chemical reactions.
4 Chemotherapy: Cancer treatment by means of chemical
drugs. Other methods are radiotherapy (using radiation) and
immunotherapy (in which the use of antibodies is usually involved).
5 US $4 900 is the price for treating breast cancer.