A team of international researchers led by Associate Professor Gautam Sethi from the Department of Pharmacology at the Yong Loo Lin School of Medicine at the National University of Singapore (NUS) reported the findings following a 12-week study on mice.
Nimbolide, a bioactive terpenoid compound derived from Azadirachta indica, more commonly known as the neem plant have a direct effect on cancer cells.
Leaf pastes and extracts from the neem plant are used in skin care products, hair treatment, toothpastes, insect repellants, mouth wash, and many other medicinal uses. Many herbalists recommend chewing the leaves, taking capsules of dried leaf, or drinking the bitter tea. The leaves cleanse the blood, help the gastrointestinal system, support the liver, and strengthen the immune system, to name just some of the most popular benefits.
Prostate cancer is one of the most commonly diagnosed cancers worldwide. However, currently available therapies for metastatic prostate cancer are only marginally effective, said the researchers, writing in the journal Antioxidants & Redox Signaling.
Neem is a natural anti-bacterial, anti-fungal, anti-inflammatory, anti-histamine, anti-viral and anti-microbial. It contains extraordinarily high levels of antioxidants and carotenoids (similar to carotene) which provide high antioxidant compounds that help defend the body against free radicals.
"Although the diverse anti-cancer effects of nimbolide have been reported in different cancer types, its potential effects on prostate cancer initiation and progression have not been demonstrated in scientific studies.
"In this research, we have demonstrated that nimbolide can inhibit tumour cell viability - a cellular process that directly affects the ability of a cell to proliferate, grow, divide, or repair damaged cell components - and induce programmed cell death in prostate cancer cells," said Associate Professor Sethi.
Cell invasion and migration are key steps during tumour metastasis. The NUS-led study revealed that nimbolide can significantly suppress cell invasion and migration of prostate cancer cells, suggesting its ability to reduce tumour metastasis, without exhibiting any significant adverse effects.
"This is possible because a direct target of nimbolide in prostate cancer is glutathione reductase, an enzyme which is responsible for maintaining the antioxidant system that regulates the STAT3 gene in the body. The activation of the STAT3 gene has been reported to contribute to prostate tumour growth and metastasis," he added. "We have found that nimbolide can substantially inhibit STAT3 activation and thereby abrogating the growth and metastasis of prostate tumour."
The neem plant belongs to the mahogany tree family that is originally native to India and the Indian sub-continent. It has been part of traditional Asian medicine for centuries and is typically used in Indian Ayurvedic medicine.
The team is now looking to embark on a genome-wide screening or to perform a large-scale study of proteins to analyse the side-effects and determine other potential molecular targets of nimbolide.