Page 10 - Science Focus (issue 15)
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Cancer is often regarded as a grim The NCI carried out further testing to study the
and dreadful state of human health in our modern anti-cancer activity of Taxol during the next 10
society – with millions of new diagnoses annually; years. It was found to be a very potent substance,
statistics estimated that more than one in three showing significant activity against lung, ovarian
people will develop cancer at some stages of and mammary cancers, at various stages of
their lives [1]. Cancer is a group of diseases that progression when tested in mice [3]. Furthermore,
commences when certain cells start mixing up Dr. Susan Horwitz of Yeshiva University revealed
signals and instructions, causing the cells to grow that Taxol works by targeting rapidly dividing cells,
and divide abnormally, with the potential of getting inside of them and attaching to a tubular
spreading throughout the body causing numerous scaffold structure called microtubules, preventing
complications. Although a lot remained unknown the cells from dividing [4].
regarding its mechanism, scientists work extremely It seems to be going so well! Taxol stops the
hard to save the lives of as many patients as division of cancer cells, which could counter the
possible! And of course, they would always be rising cases of cancer, however…
hoping to discover a substance to “cure” cancer….
In 1983, further experiments with Taxol were
In the early 1960s, the American National
Cancer Institute (NCI) initiated a wide anti-cancer halted quickly due to a shortage of supplies. In
fact, Taxol is found only in small amounts in nature,
screening, where they analyzed thousands of plant and along with many difficulties in harvesting and
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species for their ability to stop tumor growth. One extraction – only 0.5 g of Taxol was isolated from 12
source that displayed promising activity against kg of Pacific yew tree samples (equivalent to 0.004
cancer was the stem and bark of Pacific yew trees, % yield), requiring the removal of six 100-year old
Taxus brevifolia. Drs. Monroe Wall and Mansukh trees to treat one patient [5]. On top of that, these
Wani’s team at the Natural Products Laboratory trees are amongst the slowest growing trees in the
spent years concentrating and purifying the active world and were already on the brink of extinction.
anti-cancer component, with repeated careful Complete chemical synthesis was not commercially
organic solvents partitioning. Eventually, in 1967, viable – Taxol has a very complex structure,
they managed to collect a pure form of the active requiring 35 to 51 steps for its total synthesis, resulting
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ingredient – a very complex, non-polar molecule, in a low yield (0.4 %) and very high costs [6, 7]. This
which they named paclitaxel, later known by its pressured scientists to find more efficient
tradename Taxol [2].
ways to obtain Taxol.
Taxol
— The Pathway to Cancer Treatment?
紫杉醇 ─ 從自然而來的癌症良藥？
By Yasine Malki 馬建生
