Benefit of Asian pigmented rice bioactive compound and its implication in breast cancer: a systematic review

Search strategy

Articles for the current review were acquired from two electronic databases (PubMed and Scopus), considering that they hold the most articles for biomedical and pharmaceutical studies. The database literature search was conducted from November 8 to November 10, 2022. We created the keywords for each database. For PubMed, we used the following keywords; (((((cancer) OR (“breast cancer”)) OR (metastasis)) AND ((((((rice) OR (“pigmented rice”)) OR (“black rice”)) OR (“red rice”)) OR (“purple rice”)) OR (“brown ice”)) AND ((“cancer therapy”) OR (“anti-metastasis”)). Meanwhile for Scopus, the keywords were "Cancer" OR metastasis OR “MCF-7” OR “Breast cancer” OR tumor AND “Pigmented Rice” OR rice OR paddy OR “Oryza sativa” AND “Cancer Therapy” OR medicine OR pharmaceutical OR physicochemical. During literature search, only free access articles were used.

Inclusion criteria

All types of experimental and observational studies written in English language were included. All duplicate studies and literature reviews were excluded from the final selection. Study subjects focused on breast cancer, and any other objects of in vivo and in vitro studies. Study factors included in the studies were the types of pigmented rice, other interventions in the form of extracts, whole grain, bran and hull. The research results include cancer therapy, pharmaceutical, and bioactive compounds as anti-cancer.

Study selection, data extraction, and quality assessment

The aforementioned keyword search resulted in a total of 407 articles, consisting 103 and 304 articles from PubMed and Scopus, respectively. We excluded 32 manuscripts because the article were published more than 10 years ago. After excluding book chapters and papers not in English, we had 278 potential articles to be reviewed. After checking and screening carefully the title and abstract of the manuscript, the duplicate articles were eliminated, then 66 articles were obtained. The authors reviewed the full text of those studies and finally selected 10 of them which met the inclusion criteria. 46 articles did not meet the criteria because duplicated, a book chapter, not accessible, not in English and no full-text. The flow diagram of the selection of study is shown in.^26,27

Characteristics of the articles

The included studies in this review were entirely of Asian. The year of publication ranged from 2013 to 2020. Five studies used black rice extract, two used red jasmine rice extracts, and three used a mixture of Korean rice extracts (black, red and brown rice). All studies were conducted in vitro and three studies were compared with in vivo tests on female mice. The summary of the included study were: tabulated based on the results, active compounds and sample breast cancer cell lines which are presented in Table 1.

Methodological quality

We reviewed results from 10 studies, seven of which involved in vitro experiment and three of which involved both in vitro and in vivo experiment. Unfortunately, there are no specific studies that focus on in vivo experiments. In detail, we report 10 samples from in vitro studies and three samples from in vivo studies.

In vitro

Many different cells have been used in in vitro experiments, including from human and murine breast cancer.^13,18–21 Besides, there are several single-cell in vitro studies, among which are subcutaneous MDA-MB-453 cells,^18,19 MCF-7 cells,¹³ MDA-MB-231 cells,²⁰ and 4T1 cells.²¹ Furthermore, several studies used multiple cells, such as,¹⁵ which used HER2-positive (BT474, MDA-MB-453, and HCC1569 cells) and HER2-negative (MCF-7, SUM190, and MDA-MB- 231) breast cancer cell lines. The HT1080 fibrosarcoma and MDA-MB-231 cell lines were utilized in.^22,23 The cells used by¹⁶ were MCF-7, B16F10, M-3, and YD-38. The cells used by²⁴ were MCF-10A, MCF-7, and MDA-MB-453. In summary, the classification of breast cancer cells used in the 10 articles analyzed in this study were human triple-negative breast cancer (MDA-MB-231), human ERα-positive breast cancer (MCF-7), human HER2-positive breast cancer (BT474, MDA-MB-453, and HCC1569 cells), human HER2-negative (MCF-7, SUM190, and MDA-MB- 231), and murine breast cancer (4T1 and M3). There were also non breast cancer cell line used in this study, such as fibrosarcoma cell lines (HT1080), murine melanoma cell lines (B16F10), and human Squamous cell carcinoma cell lines (YD-38).

In vivo

Experiments in vivo using same species of mouse, naked female mice, were carried out with different cancer cells. Two studies employed 4-week-old mice,^18,21 while one used 6-7-week-old mice.¹⁵ In these experiments, several cells types were used and injected into the flank of mammary fat pad of mice to construct the breast cancer mice model. HER2-positive MDA-MB-453 cells were employed in one study.¹⁵ Besides, the previous study,¹⁸ found MDA-MB-453 (ErbB2-positive) was employed alongside MCF-7 (ErbB2-negative) and MCF-10A (normal) cells. In the last study, 4T1 cells were used to be transplanted to the mice.²¹

The benefit of Asian pigmented rice bioactive compound

Pigmented rice cultivars differ in terms of both qualitative and quantitative characteristics.^10–12 This rice variety is distinguished by its mostly red, black, or purple pericarps. Wide-color rice varieties have drawn more attention because of their many biological functions. The pigments serve as sources of phytochemicals when contrasting the nutritional value of colored rice with white rice brans. Anthocyanidins, ferulic acid, diferulates, anthocyanins, and polymeric proanthocyanidins are some of the phenolic chemicals.^10,11

Pigmented rice residues are attractive sources of bioactive substances such as phenolic antioxidants and anticancer agents for the benefit of human health.^12,13 Anthocyanin is found in the bran layers of the rice kernel, whereas phenolic acids are primarily present in the bran layers of rice in their free, conjugated, and bound forms.¹⁶ The two primary bioactive phenolic chemicals found in cereal grains, mostly found in the pericarp of colored types, are anthocyanins and proanthocyanidins.¹⁴ Anthocyanins, which are primary metabolites found in the bran layers of rice kernels, have been identified as functional dietary components that promote good health and have anticancer, antioxidant, hypoglycemic, and anti-inflammatory activities.¹¹

Considering the numerous health benefits connected with functional components, such as anti-inflammatory, antioxidative, and anticancer properties, pigmented rice is considered an available food and food ingredient in many Asian countries.^10–14 The anticancer effect is suggested partly through the enhancement of bioactive substances such as vitamin E, phytic acid, γ-aminobutyric acid (GABA), γ-oryzanol, and phenolics.⁹

Black rice

A traditional and healthy cuisine, black rice is mostly grown in East Asia. Phytochemicals, tocopherols, polyphenols, B vitamins, and anthocyanins are only a few examples of the water-soluble bioactive substances abundant in black rice.²¹ These substances might help your health and shield you against long-term conditions linked to oxidative stress and antioxidant activity.¹⁰ A significant amount of phytochemicals are present in black rice bran, giving it strong medicinal properties. Black rice extract anthocyanins dramatically decreased the metastasis of breast cancer, according to seven research that were considered. The aleurone layer of black rice is where black rice anthocyanins (BRACs) are found. Human breast cancer cells that are ErbB2-positive can be prevented from metastasizing by BRAC.¹⁸ Additionally, Liu et al. (2013) demonstrated that black rice extract includes peonidin-3-glucoside and cyanidin-3-glucoside, which can diminish the tumor size and volume.¹⁵

Red rice

Two studies found that red jasmine rice, which contains proanthocyanidins, inhibits breast cancer cell proliferation. Most of the phenolic chemicals in red rice, which are responsible for the red coloring of the pericarp, are proanthocyanidins and catechins.^20,22 Proanthocyanidin from red rice (PRFR) contains procyanidins and prodelphinidins.²² Moreover, red rice extract also has a high concentration of γ-oryzanol and γ-tocotrienol in the Hex and DCM fractions.²⁰

Purple rice

A variety of rice varieties, including glutinous rice, are referred to as purple rice and have historically been eaten throughout Eastern and Southeast Asia.²³ The pigments are naturally occurring compounds belonging to the flavonoid family in which cyanidin, pelargonidin, peonidin, delphinidin, petunidin, and malvidin represent the most commonly occurring anthocyanin aglycone.¹¹ One study found that purple rice hulls contained the highest phenolic compound.²³ Cinnamic acid and its derivatives are the primary ingredients for breast cancer cell growth suppression and cell cycle arrest.¹³

Implication of bioactive compound in breast cancer

Phenolic and flavonoid chemicals act as an antioxidant to protect cells from oxidative damage, which is a common cause of aggressive diseases like cancer.¹⁶ However, the anticancer activities were not directly correlated with total phenolic or total flavonoid content values.¹⁶ So, phenolic and flavonoid from many types of pigmented rice have also been tested for apoptotic activity revealing that cell shrinkage and nuclear condensation occur in human breast cancer cell line MCF-7.¹⁶ The antioxidant activity of rice phenolic compounds is detectable in parallel with the inhibition of proliferation of MCF-7 cells through G1 cell cycle arrest and comparable to quercetin as an antioxidant standart.¹³

Proanthocyanidins are monomeric flavan-3-ol oligo- or polymers that are created as a byproduct of the flavonoid biosynthesis process.²⁰ Proanthocyanidins, which are essentially concentrated tannins, are made by cytosolic multienzyme complexes acting along the phenylpropanoid route.²² By incorporating sugars, anthocyanidins are transformed into anthocyanins.¹⁹ Proanthocyanidins turn into anthocyanins when heated in an acidic medium. As byproducts of the flavonoid pathway, proanthocyanidins and anthocyanins have the same metabolic intermediates. Proanthocyanidins, in the form of procyanidin (catechin and/or epicatechin) and prodelphinidin (epigallocatechin and/or gallocatechin) showed anti-metastatic effects in cancer breast MDA-MB-231 and HT1080 cells.²² It reduces the cell invasion and migration in a dose dependent manner with IC₅₀ at 7.52±1.42 μg/mL and 10.6±0.59 μg/mL respectively and as a molecular mechanism of metastasis it inhibits collagenase activity.²⁰ Suppression of breast cancer metastasis including inhibition the mRNA expression of their signaling pathway has also been known.¹⁹

The anthocyanins pigment such as cyanin-3-glucosides or peonidin-3-glucosides known to dose-dependent inhibition of cell proliferation and suppress the tumour growth in HER2-positive cancer lines which associated with breast cancer.¹⁵ Inherent with the previously studied that both compounds inhibit cell human ductal breast carcinoma HS578T growth by blocking cell proliferation at the G(2)/M phase so that it cannot form a normal mitotic apparatus, lowering some cancer response proteins, and chromatin condensation leads to cell death.²³ Anti-metastasis action prevents cancer cells from invading the blood or lymphatic vessel and spreading to other tissues or organs, among other benefits. The anthocyanins found in black rice are able to lower almost 40% of tumour nodules with in vivo studies and about 10% inhibits invasion of cancer breast MDA-MB-453 cells.¹⁸ Aprevious study reported a higher invasive inhibition of cells by 68% and also a decrease in the migration distance of MDA-MB-453 cells by 37% with anthocyanins compared to untreated cells after 24 hours.²⁴

Strengths and limitations of the review

Several bioactive substances with the potential to operate as anti-metastatic agents, including anthocyanins, phenolics, and flavonoids found in different kinds of pigmented rice, are among the articles employed. To ensure the efficacy of each bioactive chemical, however, more in vivo research or randomized clinical trials with multicenter investigations are required as the majority of them are in vitro studies.

Significance of the findings and possible mechanism

Breast cancer is a complex and multifactorial disease that involves many cellular and molecular pathways. Weinberg and Hanahan in 2000 stated 6 hallmarks of cancer, (1) continuous proliferative signaling, (2) escaping growth suppression, (3) countering cell death, (4) sustaining replicative immortality, (5) promoting angiogenesis, and (6) metastasis.²⁵ To overcome this complex phenomenon, an effective therapy needs to be found. Due to the multi-target cancer therapy, natural product consumption is currently a major problem. As a result, this study investigated the bioactive chemicals found in Asian pigmented rice that were intended to target many pathways in the treatment of cancer (Figure 1).

Figure 1. Pigmented rice bioactive compound possible mechanism from breast cancer.²⁸

This study found that bioactive compounds from the 10 articles reviewed, involved in several pathways on breast cancer, such as metastasis, cell growth and proliferative signaling, cell cycle progression and apoptosis.^13,15–24

Black rice extract with unidentified compounds has anti-metastatis activity through the reduction of anti-metastasis related protein expression such as snail, vimentin, and E-cadherin.²¹ Besides, peonidin-3-glucoside, cyaniding-3-glucoside from black rice, and cinnamic acid from WD-3 varieties of Korean rice showed anti-proliferative activity on breast cancer.¹⁵ Peonidin-3-glucoside and cyaniding-3-glucoside of black rice also promoted apoptotic activity through the induction of caspase 3/7.^15,16 Anti-metastatic pathway was mostly found to be involved in the implication of pigmented rice bioactive compounds against breast cancer.²² This study found that γ-oryzanol, γ-tocotrienol, and proanthocyanidin from red rice reduced MMP2 and -9 secretion.²² In addition, MMP9 along with ICAM, IL-6, and NFkB were reduced after treated by red jasmine rice that contained proanthocyanidin.²⁰ Anti-metastasis also mediated by black rice anthocyanins through the reduction of FAK, cSrc and p130Cas phosphorylation. Black rice anthocyanins also posed anti-metastatic activity through the suppression RAF/MEK/ERK pathway and MMP2,-9 downregulation.¹⁹ Lastly, black rice anthocyanins can suppressed u-PA involved in tumor invasion.¹⁸