African medicinal plants may stop tumor growth from multi-drug resistant cancers: Research

Wednesday, June 26, 2013 by: David Gutierrez, staff writer
Tags: cancer treatment, African plants, medicinal herbs

(NaturalNews) Traditional African medicinal plants may contain naturally occurring compounds that effectively kill drug-resistant cancers, according to research conducted by Victor Keute of the University of Dschang in Cameroon and Thomas Efferth of Johannes Gutenberg University Mainz in Germany.

"The active substances present in African medicinal plants may be capable of killing off tumor cells that are resistant to more than one drug," Efferth said. "They thus represent an excellent starting point for the development of new therapeutic treatments for cancers that do not respond to conventional chemotherapy regimens."

Investigating nature's pharmacy

Because plants are unable to flee from predators, evolution has imbued them with a wide array of physical and chemical defenses instead. Many of these chemicals are phenomenally complicated and potent venomous and anti-microbial agents, and take the place of the complex cellular immune system found in animals.

Because these compounds evolved to kill many of the same pathogens that afflict human beings, they can often be used as highly effective medicines. The problem is that many plant compounds also evolved to deter animal predators, including large mammals such as ourselves. That means that when analyzing the defensive chemicals produced by plants, scientists need to work hard to distinguish between those that are medicinal and those that are poisonous or harmful.

Efferth and Kuete have been collaborating together for four years, investigating traditional African medicinal plants including the Ethiopian pepper, giant globe thistle, speargrass and wild pepper. So far, they have tested a total of more than 100 plants and spices in search of cytotoxic (cancer-killing) effects.

Promisingly, they have already uncovered at least four naturally occurring chemicals in the family known as the benzophenones that are effective at preventing the proliferation of cancer cells, including multi-drug resistant varieties.

"We have already found an entire series of benzophenones and other phytochemicals that are able to elude resistance mechanisms and thus offer many new opportunities for continued research," Efferth said.

The challenge of drug resistance

Multi-drug-resistant cancer strains are those that fail to respond to more than one standard drug treatment. These cancer varieties are notoriously hard to treat and are far more lethal than standard varieties. Although in some cases, drug resistance can be overcome with higher drug doses, such high doses also increase the risk and magnitude of the often severe side effects associated with cancer treatments.

One of the things that makes drug-resistant cancers so difficult to deal with is that cancers can evolve drug resistance through several separate mechanisms. In their research, Efferth and Kuete are testing the African plants against a cancer cell line that uses three separate drug-resistance strategies. The first, known as transporter-mediated resistance, occurs when a substance called P-glycoprotein causes drugs to be prematurely flushed out of cancer cells. The second, tumor-suppressor-gene-mediated resistance, results from a mutation to protein p53 that makes cancer cells enormously aggressive and resistant. The third, oncogene-mediated resistance, occurs when the epidermal growth factor receptor (EGFR) signals cancerous tumors to accelerate their growth, overwhelming the capacity of drugs to kill them.

Yet the researchers have already discovered substances from the African plants that are effective against all of these strategies. They are now further testing these chemicals in the hopes of developing them into effective drugs.

"The benzophenones investigated are potentially cytotoxic substances that need to be more extensively investigated with the aim of developing new cancer drugs that are effective against susceptible and resistant cancers," they wrote recently in the journal Phytomedicine.

"We are now looking for substances that can both break down tumor resistance and not produce side effects," Efferth said.

Sources for this article include:

http://www.uni-mainz.de/presse/16481_ENG_HTML.php

http://www.eurekalert.org/pub_releases/2013-06/jgum-sfa061013.php