A flavanone compound in milk thistle, silibinin, may stop the growth and spread of liver cancer, suggests a laboratory study from the University of California, Irvine.

The in vitro study used human liver cancer cells exposed to different doses of silibinin, and found that the milk thistle compound could inhibit the spread of the cells and promote programmed cell death (apoptosis).

It should be stressed that the new research, published in the World Journal of Gastroenterology, did not use milk thistle dietary supplements, but pure silibinin, the active component in milk thistle.

Liver cancer is the sixth most commonly diagnosed cancer in the world, and third most common cause of death from cancer, according to Cancer Research UK. Despite these figures, the cancer remains relatively rare, with 18,500 new cases in the US every year, and about 3,000 in the UK.

The highest incidences of the disease are in east and Southeast Asia, particularly China, and for this reason the current researchers looked at the effects of probiotic supplements on markers for the disease.

Ke-Qin Hu and his research team tested doses of silibinin ranging from 10 to 240 micromoles per litre for the human liver cancer cell lines, HuH7, HepG2, Hep3B, and PLC/PRF/5.

The researchers report a dose-dependent response at levels above 180 micromoles per litre, and an IC50 value, a measure of the extract concentration under which 50 per cent of the cell population growth was inhibited, of 240 micromoles per litre.

Additional study was limited to the HuH7 cell line, "because the HuH7 cell line is one of the most commonly used human (hepatocellular carcinoma) HCC lines," said the researchers.

A mechanistic study indicated that the milk thistle compound was associated with an increase in histone acetylation. The significance of this increase is that histone acetylation is reportedly involved in cell proliferation, differentiation, and cell cycle regulation.

Indeed, measurements of apoptosis showed that, at a dose of 240 micromoles per litre, silibinin increased programmed cell death of the cancer cells by a factor of nine.

Hu and co-workers state that further work is necessary to full elucidate the mechanism. It is also not known if the doses required to offer the potential anti-cancer benefits could be achieved using milk thistle supplements.

"Our findings not only indicate silibinin's novel anti-cancer mechanisms, but also provide additional targets for searching new agents for HCC chemoprevention," concluded the researchers.

Milk thistle (Silybum marianum) has been used for a long time as a food in Europe. Young leaves are used in salads, the stalks eaten like asparagus, and the heads boiled like artichoke.

According to the Manitoba Agriculture, Food and Rural Initiatives (Canada) milk thistle ranked 12th among the top selling herb supplements in the US mass market, with sales of over $3m in 1997.

Previously, silibinin has linked to similar benefits against lung cancer growth (Journal of the National Cancer Institute, Vol. 98, pp. 846-85).

Source: World Journal of Gastroenterology
Volume 13, Issue 40, Pages 5299-5305
"Effects and mechanisms of silibinin on human hepatoma cell lines"
Authors: J.J. Lah, W. Cui, K.Q. Hu