A chemical derived from a Chinese medical herb shows potential promise as a cancer drug, or at least illustrates possible new strategies for cancer treatment

In a prior post it was noted that certain B vitamins (those studied were thiamin, riboflavin, niacin, pyridoxine, and cobalamin) and certain vitamin antioxidants (those studied were vitamins A, C, and E) had a positive effect by reducing arsenic-related skin lesions.  Now, a recent study reports on identifying a Nrf2-dependent cytoprotective response that provides an improved cell survival after an arsenic challenge.  See http://www.ehponline.org/members/2008/11464/11464.html.  [Nrf1 and Nrf2 positively regulate the human antioxidant response element-mediated expression of the NAD(P)H:quinone oxidoreductase₁ gene.]

The researchers report the identification of a novel class of Nrf2 activators.  Oridonin, also known as rubesecensin A, is a diterpenoid [see http://en.wikipedia.org/wiki/Diterpenoid] purified from the Chinese medicinal herb Rabdosia rubescens.  R. rubescens has been used by Chinese doctors to treat swelling of the throat, insect bites, snake bites, inflammation of the tonsils, and cancer of the esophagus, stomach, liver, prostate, and breast.  The active ingredients in R. rubescens are rubesecensin A (oridonin) and rubesecensin B.  Currently the major research focus on oridonin is in its antiproliferation and antitumor activities.  The anticancer activity of oridonin is thought to rely on its ability to inhibit cell growth, reduce angiogenesis [growth of new blood vessels, necessary for the survival of a cancer mass; see http://en.wikipedia.org/wiki/Angiogenesis], and enhance apoptosis [a form of programmed cell death that some theories believe is rendered inoperative by cancers; see http://en.wikipedia.org/wiki/Apoptosis].  Oridonin has been found to inhibit cell growth and induces apoptotic cell death in many cancer cell lines used by scientists for research.  The reported doses needed for growth inhibition and apoptosis vary significantly among different groups using different cell lines, ranging from 0.5 µM (0.18 µg/mL) in Kasumi-1 cells to 56 µM (20.4 µg/mL) in HPB-ALL cells. In addition, oridonin enhances the efficacy of the cancer drug cisplatin in mouse sarcoma cells. 

The bottom line, obviously, is that the substance has significant potential.  The researchers report that oridonin represents a novel class of Nrf2 activators that has not been demonstrated previously.  It thus holds promise as a significant potential substance in the treatment of various cancers, or at least elucidates a fascinating pathway to be further explored in cancer treatment.