Could SA plants hold the secret to a new cancer drug?

The CSIR bioprospecting research group has tested more than 7 000 randomly-selected South African plants


About nine million people worldwide will die from cancer in 2015, while a further 11,4 million are expected to perish from the disease in 2030. The World Health Organization believes these grim estimates are likely to become a reality, based on the 58 million deaths in 2005, of which cancer accounted for 7,6 million or 13%. The Cancer Association of South Africa predicts that one in four South Africans will be affected by cancer in his/her lifetime. Cancer is a generic term for a group of more than 100 diseases that can affect any part of the body.

The research

For the past decade, CSIR scientist Dr Gerda Fouché and her colleagues in the organisation's bioprospecting research group have been generating knowledge for potential anti-cancer drugs. In collaboration with the National Cancer Institute (NCI) in the USA, they have been investigating drug leads from plants reportedly containing medicinal properties, including validating remedies and testimonies from traditional healers who claim to have cured or treated cancer with specific plants.

From late 1998 to 2005, the CSIR coordinated the collection of about 11 000 plant species. South Africa has some 24 000 plant species unique to the country. To date, more than 7 000 randomly-selected plant extracts have been tested. This despite working with limited financial support for cancer research by funding bodies - something that Fouché says has started changing recently.

"Cancer is not a disease that Africa really focuses on. It doesn't even rank highly on the list of major diseases on the continent and therefore funding opportunities are usually limited, although this appears to be changing," says Fouché, who has witnessed the inverse situation at international conferences where HIV/Aids takes a back seat to cancer research. Fouché and members of the CSIR's bioprospecting research group, led by Dr Vinesh Maharaj, have 15 plant leads in development thus far for therapeutic areas including cancer, benign prostatic hyperplasia, arthritis, HIV, malaria, tuberculosis, mosquito repellency, asthma, inflammation and wound-healing.

The potential of using natural products as anticancer agents was recognised in the 1950s by the NCI. In 1998 a collaborative research programme for the screening of plant extracts and identification of potentially new anticancer drug leads was initiated between the CSIR and the NCI. The following year an in-house anticancer screening programme based on NCI technology was implemented at the CSIR with a panel of three human cancer cell lines - breast, renal and melanoma. These three cell lines are used because of high sensitivity to detect anticancer activity. Plant extracts that exhibit anticancer activity are screened by the NCI against 60 human cancer cell lines organised into sub-panels representing leukaemia, melanoma, cancer of the lung, colon, kidney, ovary and central nervous system.

Dr Gerda Fouché analysing samples with colleague Natasha Kolesnikova who manages the CSIR's cancer screening laboratory

"Two different approaches are used to investigate extracts and arrive at active compounds," explains Fouché, a chemist who focused on the synthesis and stereochemistry of compounds for her PhD studies. She has 13 publications - one on the investigation of South African plants for anticancer properties - and three provisional patents to her name. "Most cancer screening is conducted through the random approach. We also follow the anecdotal approach when, for example, a traditional healer submits a plant claiming to treat a specific type of cancer with it."

"Extracts are classified as either potent, moderate or weak," explains this former University of Venda lecturer. "We focus on extracts showing potent and moderate activity," she says before dissecting the nitty-gritty of the procedure of preparing extracts in two different solvents that ultimately lead to the screening of promising plant compounds. However, a potential drug from this laboratory is not yet imminent. "Most of the compounds we isolate have been patented or reported on in scientific publications and screened by the NCI. Cancer is well researched in developed countries and it is difficult for scientists in developing countries to come up with novel, active compounds. But in South Africa we are motivated to continue with the research because of our unique biodiversity."

The future

What about the 15 plant leads in development for cancer and other ailments? The next step, according to Fouché, would be to further investigate the leads in a suitable in vivo (animal) model before any of these can be submitted for preclinical studies. This would be achieved through collaboration with the NCI and other South African research institutions.

Last year, in the interest of racing against the clock, Fouché and her team decided to narrow their screening of plants by using a targeted approach specifically investigating South African plants containing alkaloids - proof of Fouché's 'never-say-die' attitude under the toughest of circumstances.

"I enjoy the challenge; something new is derived from conducting research. For instance, the cure for prostate cancer is still an open field," she says.

And discovering the unknown to possibly help thousands of men, women and children who are suffering or will suffer from cancer is all the motivation she needs to continue working with medicinal plants for cancer research.

"It's an unknown field. South Africa's biodiversity remains a great source of interest to the scientists and you work with plant extracts that have never been investigated before. There must be something out there that can be used to treat cancer," she concludes.- CSIR


March 2008