Anti-cancer Drug from Transgenic Moss

Scientists at the Southern Illinois University and Washington University in the U.S. have developed transgenic moss (Phsycomitrella patens) accumulating high levels of paclitaxel, a potent anti-cancer drug. Paclitaxel, or more commonly known by its brand name Taxol, is widely prescribed to patients with lung, breast and ovarian cancer as well as to patients with advanced form of Kaposi's sarcoma. First isolated from the bark of Pacific yew (Taxus brevifolia), paclitaxel inhibits the proliferation of cancer cells by disrupting microtubule disassembly during cell division.

Extremely low levels of paclitaxel in Pacific yew prompted researchers to develop chemical methods to synthesize the anti-cancer agent. Transgenic expression systems, especially using bacteria and yeasts, have also been used to produce paclitaxel precursors. But none of these methods are suitable for large-scale commercial production of paclitaxel. Currently, the drug is manufactured from a precursor compound isolated from the needles of European yew.

Compared to other plant expression systems, the transgenic moss that  the scientists developed accumulated higher levels of the paclitaxel precursor taxa-4(5),11(12)-diene (up to 0.05% fresh weight of tissue).  Although this is lower than what can be achieved when yeasts and bacteria are used, the scientists noted that microbes have different post-translational modification mechanisms which may affect the activity of the paclitaxel precursor.

The complete article published by Transgenic Research is available for download at http://dx.doi.org/10.1007/s11248-009-9252-5