Taxanes are a class of

diterpene Diterpenes are a class of terpenes composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being a primary ...

s. They were originally identified from plants of the genus ''

Taxus ''Taxus'' is a genus of coniferous trees or shrubs known as yews in the family Taxaceae. Yews occur around the globe in temperate zones of the northern hemisphere, northernmost in Norway and southernmost in the South Celebes. Some populations ex ...

'' (yews), and feature a taxadiene core.

Paclitaxel Paclitaxel, sold under the brand name Taxol among others, is a chemotherapy medication used to treat ovarian cancer, esophageal cancer, breast cancer, lung cancer, Kaposi's sarcoma, cervical cancer, and pancreatic cancer. It is administered b ...

(Taxol) and

docetaxel Docetaxel (DTX or DXL), sold under the brand name Taxotere among others, is a chemotherapy medication used to treat a number of types of cancer. This includes breast cancer, head and neck cancer, stomach cancer, prostate cancer and non-small-cel ...

(Taxotere) are widely used as

chemotherapy Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...

agents. Cabazitaxel was FDA approved to treat hormone-refractory

prostate cancer Prostate cancer is the neoplasm, uncontrolled growth of cells in the prostate, a gland in the male reproductive system below the bladder. Abnormal growth of the prostate tissue is usually detected through Screening (medicine), screening tests, ...

. Taxanes present difficulties in

formulation Formulation is a term used in various senses in various applications, both the material and the abstract or formal. Its fundamental meaning is the putting together of components in appropriate relationships or structures, according to a formula ...

as medicines because they are poorly soluble in water.

Production

As their name suggests, taxanes were first derived from natural sources, but some have been semisynthesized. Paclitaxel was originally derived from the Pacific yew tree. Taxanes are difficult to synthesize because of their numerous

chiral Chirality () is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek language, Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is dist ...

centres—taxol has 11 of these. Recently, the presence of taxanes in the shells and leaves of ''

Corylus avellana ''Corylus avellana'', the common hazel, is a species of flowering plant in the birch tree, birch family Betulaceae. The shrubs usually grow tall. The nut is round, in contrast to the longer Corylus maxima, filbert nut. Common hazel is native to E ...

'' (the common hazel plant) has been reported.

Mechanism of action

The principal mechanism of action of the taxane class of drugs is the disruption of

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nanometer, nm and have an inner diameter bet ...

function. Microtubules are essential to cell division, and taxanes stabilize GDP-bound

tubulin Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytosk ...

in the microtubule, thereby inhibiting the process of cell division as ''depolymerization'' is prevented. Thus, in essence, taxanes are mitotic inhibitors. In contrast to the taxanes, the

vinca alkaloids ''Vinca'' alkaloids are a set of anti-mitotic and anti-microtubule alkaloid agents originally derived from the periwinkle plant '' Catharanthus roseus'' (basionym ''Vinca rosea'') and other ''vinca'' plants. They block beta-tubulin polymeriza ...

prevent

mitotic spindle In cell biology, the spindle apparatus is the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells. It is referred to as the mitotic spindle during mitosis, a process ...

formation through inhibition of

''polymerization''. Both taxanes and vinca alkaloids are, therefore, named

spindle poison A spindle poison, also known as a spindle toxin, is a poison that disrupts cell division by affecting the protein threads that connect the centromere regions of chromosomes, known as spindles. Spindle poisons effectively cease the production of new ...

s or mitosis poisons, but they act in different ways. Taxanes are also thought to be radiosensitizing.

Substances

Hongdoushans A–C are oxygenated taxane diterpenes, isolated from the wood of '' Taxus wallichiana''. Hongdoushan A (C₂₉H₄₄O₇), hongdoushan B (C₂₇H₄₀O₇), and hongdoushan C (C₂₇H₄₂O₆) are reported to have anticancer activity ''in vitro''. Taxuspines A–D have been isolated from ''Taxus''.

Names

Taxanes are usually treated as

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

ous with taxoids. The name "taxol" began as a common noun (analogous with other terms in which a genus name root was

suffix In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns and adjectives, and verb endings, which form the conjugation of verbs. Suffixes can ca ...

ed with '' -ol'' or '' -in''), but it was later capitalized as a trade name, and the international nonproprietary name of the compound is paclitaxel.

References

External links