Natural anticancer compounds: Studies examine potential of Boswellia, soy and green tea

16 Jan 2024 --- Although breast cancer treatment and early detection methods continue to advance, researchers call for alternative therapies to complement current treatments, as they note that many have long-term adverse side effects. In an early-stage clinical trial, they identified the antiproliferative effects of Boswellia serrata extract against breast cancer. 

Breast cancer patients consumed an extract of the Indian frankincense tree each day until their surgery. The research team compared the activity of cancer cells in each tumor removed during this surgery with that of tumor pieces removed during the patients’ biopsy. They also compared biopsy and timer samples of women who did not take the Boswellia extract. 

“We saw a statistically significant reduction in tumor proliferation compared to the non-treated group, so the implications are that Boswellia, this extract of frankincense, does have anticancer activity in humans,” says co-author Nancy Klauber-DeMore, MD, a surgical oncologist and co-leader of Developmental Cancer Therapeutics at Hollings Cancer Center, US. 

Meanwhile, researchers from the Johns Hopkins Kimmel Cancer Center reviewed studies on the effect of various phytonutrients on breast cancer. Though pointing to a need for more research, they concluded that soy, enterolactone — a compound metabolized from lignans found in plants, seeds and nuts — and green tea demonstrated “significant risk reductions in outcomes following breast cancer.” 

“These findings were graded probable, which means there is strong research showing that they contributed to the results we are seeing,” says lead study author Diana van Die, Ph.D., of the NICM Health Research Institute at Western Sydney University, Australia. 

Reducing tumors 
For the study published in Breast Cancer Research and Treatment, 18 patients with invasive breast cancer were treated with B. serrata extracts for 2400 mg/daily for an average of eleven days until the night before surgery. 

“We looked at differences in the growth rate of the tumors before and after treatment, and we found that the tumors after treatment had a lower growth rate than before treatment,” explains Klauber-DeMore. 

She emphasizes that the preliminary study is only meant to determine whether there was an effect; more work is needed to leverage the promising results. 

“This study was not designed to look at survival or recurrence — it was designed to see if this supplement has anticancer activity in humans. Since this was a positive trial, larger studies to look at endpoints of survival and recurrence are warranted,” explains Klauber-DeMore. “This does not imply that patients should take Boswellia in place of standard breast cancer treatment.”

In addition, the trial patients experienced minimal side effects from the extract. “This is part of the drug development process, and this shows us that there’s activity, which means that we need to do future studies to see if Boswellia prolongs survival,” adds Klauber-DeMore. 

The clinical trial results suggest that Boswellia extracts, from the Indian frankincense tree, reduce tumor proliferation.Drug development 
Researcher Mark Hamann of the Hollings Cancer Center explains that many anticancer and other drugs started as traditional plant medicines, such as Taxol — a chemotherapy drug developed from the Pacific yew tree — and vinblastine and vincristine, chemo drugs derived from the Madagascar periwinkle. 

He adds that although the resin has probably been used in medicine longer than any other plant-based product, there aren’t any purified active drug products from the plant. “It is disappointing — but based on our difficulty in identifying the active pharmaceutical ingredient, perhaps not surprising.”

The team is working on further developing the research, starting with purifying molecules isolated in Boswellia and reformulating these into a standardized oral medication for testing. 

They also added some Boswellia extract to a cancer cell sample to determine whether it showed anticancer activities directly on the cancer cells. While that approach failed to reveal the active pharmaceutical ingredient, the lab used an informatics approach to compare all known molecules against all known breast cancer targets. This resulted in two molecules of interest for future studies. 

Commonly used for joint health, B. serrata is also used in natural pain management as its boswellic acids have anti-inflammatory effects. 

Analyzing foods and phytonutrients 
International researchers reviewed 22 published observational studies to examine the impact of soybeans, lignans, cruciferous or cabbage-family vegetables, green tea and the phytonutrients from these substances on breast cancer recurrence and mortality, plus mortality from all causes. 

“It is critically important to stress that these studies were conducted on women who received medical or surgical treatment for breast cancer and that these foods and phytonutrients should not be considered as alternatives to treatment,” says Van Die. 

Senior study author Channing Paller, M.D., director of prostate cancer clinical research and an associate professor of oncology at Johns Hopkins, adds: “This research highlights the need for more robust studies looking at the most effective dosages of these compounds and whether consuming them after diagnosis has the same effect as a lifelong dietary habit before diagnosis. This is what patients are looking for.” 

Consuming 60 mg of soy isoflavones reduced breast cancer occurrence — equivalent to two to three cups of soy milk, or 1.5 cups of cooked soybeans.The review, published in JNCI Cancer Spectrum, linked soy isoflavones — plant-derived compounds — with a 26% reduction in breast cancer recurrence, based on six studies on a total of 11,837 women. The results were most robust among postmenopausal survivors at a consumption of 60 mg per day. This is equivalent to two to three servings of a cup of soy milk, three ounces of tofu or a half-cup of cooked soybeans. 

In terms of reducing all-mortality risk, the reduction was most robust at a consumption of 20 to 40 mg daily. 

Further research needs
Moreover, the review found that enterolactone reduced the risk of breast cancer-specific mortality by 28% and death from any cause by 31%, again most notably in postmenopausal women. This compound is metabolized from lignans, of which high levels are found in flaxseeds, cashew nuts, broccoli and Brussels sprouts. 

At the same time, the researchers caution it is impossible to calculate the effective dose of lignans in the diet as the gut microbiome, which plays a role in their metabolism, varies among individuals. 

The effects of lignans are likely dependent on the hormonal environment, as consumption by pre-menopausal women suggested an increased risk of mortality. The researchers caution that more research is required. 

Meanwhile, data suggests that green tea consumption reduces breast cancer occurrence by 44% in women with stage I or II. Consuming at least three cups a day was found to have the most significant effect. 

Data on the impact of cruciferous vegetables was inconclusive. Due to a lack of data, the researchers also were not able to determine whether consumption of these foods and phytonutrients before or after breast cancer diagnosis made a difference. 

By Jolanda van Hal