Potential benefits of traditional Maori plant extracts for prostate cancer control, modelled in prostate cancer cell lines

Abstract

Despite continuous cancer research and evolution of therapies over the years in New Zealand, we still have the highest incidence of prostate cancer (PC) in the world, resulting in a significant public health burden. PC was the most commonly registered cancer (3129) and one of the biggest causes of cancer death in New Zealand, claiming 647 lives in 2013. Currently there is a PC survival disparity between Maori and European populations in New Zealand. More Maori men are diagnosed with severe cases of PC than non-Maori men and death rates from PC are higher for Māori men compared to other ethnic groups in New Zealand. Traditional Maori diets are thought to be abundant in many beneficial edible plants, herbs and roots, which aided in the prevention of various diseases including cancer. Plants, such as kawakawa, puha, kumarahou and watercress have thought to be used frequently by Maori to treat various ailments. There may be several reasons to explain the severity in PC observed in Maori populations, however, deviation from their traditional diet and lifestyle, along with acquiring a westernized diet and lifestyle may have played a key role. This study aimed to identify possible protective effects of traditional Maori medicinal plants using PC cell lines models LnCaP and its analogue that overexpresses aldo-keto reductace1C3 (AKR1C3) (LnCaP+ cell line) depicting PC aggressiveness. Using prostatespecific antigen (PSA) measurements, AKR1C3 activity, DNA damage assessments through the comet assay, and gene expression assessed through real time PCR, we investigated the effects of several Maori traditional food plants (puha, kawakawa, kumarahou and watercress). Additionally, their benefits in the presence of a tobacco metabolite. We have shown that kawakawa extract is a potential candidate towards reducing PSA levels and DNA damage. Upon kawakawa treatment, gene expression of nuclear signalling factors peroxisome proliferator-activated receptor gamma (PPAR gamma) and androgen receptor (AR) were significantly increased in LnCaP+ cells, while recording a significant decrease PPAR gamma was in LnCaP cells. Future direction for work with kawakawa is suggested including studies with other AKR1C3 overexpressing cancer cell lines.