Inflammopharmacology

, Volume 20, Issue 6, pp 307–314

A review of the anticancer and immunomodulatory effects of Lycium barbarum fruit

Authors

  • Wai-Man Tang
    • Food Safety and Technology Research Centre, Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University
  • Enoch Chan
    • Food Safety and Technology Research Centre, Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University
  • Ching-Yee Kwok
    • Food Safety and Technology Research Centre, Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University
  • Yee-Ki Lee
    • Food Safety and Technology Research Centre, Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University
  • Jian-Hong Wu
    • State Key Laboratory of Chinese Medicine and Molecular PharmacologyThe Hong Kong Polytechnic University
  • Chun-Wai Wan
    • Food Safety and Technology Research Centre, Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University
  • Robbie Yat-Kan Chan
    • Division of Science and Technology, Programme of Food Science and TechnologyBeijing Normal University-Hong Kong Baptist University United International College
  • Peter Hoi-Fu Yu
    • Food Safety and Technology Research Centre, Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University
    • State Key Laboratory of Chinese Medicine and Molecular PharmacologyThe Hong Kong Polytechnic University
    • Food Safety and Technology Research Centre, Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University
    • State Key Laboratory of Chinese Medicine and Molecular PharmacologyThe Hong Kong Polytechnic University
Review

DOI: 10.1007/s10787-011-0107-3

Cite this article as:
Tang, W., Chan, E., Kwok, C. et al. Inflammopharmacol (2012) 20: 307. doi:10.1007/s10787-011-0107-3

Abstract

The anticancer effects of traditional Chinese medicine (TCM) have attracted the attention of the public vis-à-vis existing cancer therapies with various side effects. Lycium barbarum fruit, commonly known as Gou Qi Zi in China, is a potential anticancer agent/adjuvant. Its major active ingredients, L. barbarum polysaccharides (LBP), scopoletin and 2-O-β-d-glucopyranosyl-l-ascorbic acid (AA-2βG), are found to have apoptotic and antiproliferative effects on cancer cell lines. Moreover, LBP also contributes to body’s immunomodulatory effects and enhances effects of other cancer therapies. It is not known whether there are any undesirable effects. Further studies on its pharmacological mechanisms and toxicology could facilitate a safe usage of this TCM herb.

Keywords

AnticancerImmunomodulationLycium barbarum fruitTraditional Chinese medicinePharmacologyPolysaccharides

Introduction

Existing cancer therapies include surgery, chemotherapy, radiotherapy, hormone therapy and immunotherapy, all of which have their own disadvantages. Surgery is usually the primary procedure to remove cancerous tumour. Nevertheless, surgical removal of primary tumour may trigger a faster metastatic process in the remaining cancer cells. Both chemotherapy and radiotherapy carry high risks and severe side effects, such as hair loss, nausea and vomiting, infertility and/or even development of secondary neoplasia (Brydoy et al. 2007; Hijiya et al. 2007; Gurgan et al. 2008). Depression of the immune system and cognitive dysfunction (Tannock et al. 2004) occur after chemotherapy in some cases. Diarrhoea, inflammation, heart disease and lymphedema can also result during radiotherapy (Meek 1998; Dearnaley et al. 1999; Taylor et al. 2007). Besides, mucositis as a side effect caused by radiotherapy-induced sub-acute damage or chemotherapy-induced stomatotoxicity is very common (Sonis 1998; Ong et al. 2010). Adverse side effects of hormone therapy for treating prostate cancer include loss of libido, osteopenia, anemia, muscle atrophy, loss of cognitive function and decrease in high-density lipoprotein (Hellerstedt and Pienta 2002).

The human body exerts protective effect against tumour development mainly through apoptosis, cell cycle arrest and immune responses. Apoptosis, also known as programmed cell death, involves cell blebbing, shrinkage, nuclear fragmentation, chromatin condensation and chromosomal DNA fragmentation. It can be triggered by the activation of tumour suppressor genes, caspase, apoptosis-inducing factor, cytotoxic T cells and natural killer (NK) cells via a Fas ligand- or perforin/granzyme B-dependent pathway (Fadeel and Orrenius 2005). Cell cycle arrest allows verification and repair of DNA damage. The rate-limiting G1/S, intra-S and the G2/M checkpoints in cell cycle prevent cell cycle progression at specific points, and therefore prevent emergence of tumour cells (Elledge 1996). Moreover, cell cycle inhibitor retinoblastoma susceptibility (RB) protein and p53 protein activate the control systems of the checkpoints (Livingstone et al. 1992; Dunaief et al. 1994). However, during the growth of a tumour there is a harmful mutation of genes that regulate cell division, such as activation of oncogenes, p53 and RB protein. Thus, cells can actively and continuously proliferate, leading to benign tumours and then formation of malignant masses.

The innate and adaptive immune systems also exert host-protecting effect against tumour development. When a solid tumour reaches a certain size, its growth becomes invasive and causes minor disruptions within the surrounding tissues, inducing inflammatory signals that lead to recruitment of immune cells such as NK cells, T lymphocytes, macrophages and dendritic cells into the site. These cells are stimulated to produce interferon-γ (IFN-γ), which induces tumour death by its antiproliferative and apoptotic functions. Additionally, IFN-γ induces production of chemokines from tumour cells and surrounding normal host tissues, leading to blockage of angiogenesis and death of the tumour cells. The chemokines produced also recruit NK cells and macrophages to the site. NK cells and macrophages that infiltrate into the tumour can transactivate one another by reciprocal production of IFN-γ and IL-12, killing more cancer cells by tumour necrosis factor-related apoptosis-inducing ligand, perforin and reactive oxygen and nitrogen species. Tumour cell debris formed after apoptosis is ingested by local dendritic cells and migrates to the draining lymph node, thereby inducing tumour-specific IFN-γ-expressing CD4+ T helper cells, which in turn facilitate the development of tumour-specific CD8+ T cells. Afterwards, tumour-specific CD4+ and CD8+ T cells migrate to the tumour site, where CD8+ T cells destroy the remaining antigen-bearing tumour cells whose immunogenicities are enhanced by exposure to IFN-γ. The equilibrium process is a phase when lymphocytes and IFN-γ exert selective pressure on the tumour cells, a pressure that allows the survival of genetically unstable and rapidly mutating tumour cells (Dunn et al. 2002, 2004). Therefore, immunomodulatory agents that can activate immune cells like NK cells, T lymphocytes, macrophages and dendritic cells are potential antitumour agents. It has been proven that polysaccharides and related derivatives isolated from fungi and plants have high potential to be developed into anti-cancer adjuvants because of their anti-tumour and immunomodulatory effects (Chang 2002; Chan et al. 2011).

Lycium barbarum fruit, which is sweet in taste, is mainly found in Ningxia Province, China. Ancient Chinese medical literature extols L. barbarum fruit for its ability to strengthen the eyes, liver, kidneys and lung channels. It is used in its dried form (Fig. 1). There are scientific proofs of its immunomodulation, hypoglycemia, hypolipidemia, antiaging and antitumour properties (Gan et al. 2004; Jing et al. 2009; Zhang et al. 2011). Surprisingly, the herb has also been shown to have synergistic actions with chemotherapy and radiotherapy and reduce their side effects (Zhu 1998).
https://static-content.springer.com/image/art%3A10.1007%2Fs10787-011-0107-3/MediaObjects/10787_2011_107_Fig1_HTML.jpg
Fig. 1

Lycium barbarum fruit in dried form

This review studies recent findings on the anticancer effects and immunomodulatory effects of various major components of Lyciumbarbarum fruit so as to attract the attention of researchers towards this potential anti-cancer agent/adjuvant.

Active ingredients found in Lycium barbarum fruit

The major active ingredients isolated from this herb are L. barbarum polysaccharides (LBP), scopoletin and 2-O-β-d-glucopyranosyl-l-ascorbic acid (AA-2βG). There are 19 different constituents of LBP isolated from L. barbarum (Table 1). The pharmacological effects of the ingredients are summarised in Table 2. L. barbarum fruit also contains various common ingredients apart from aforementioned compounds (Table 3).
Table 1

Constituents of LBP purified from the fruit of Lycium barbarum

Glycoconjugate

MW (kDa)

Carbohydrate content (%)

Monosaccharides (molar ratio or %)

Immunomodulatory effect

Reference

LbGp2

68.2

90.71

Ara, Gal (4:5)

 

(Peng and Tian 2001)

LbGp3

92.5

93.6

Ara, Gal (1:1)

 

(Huang et al. 1998)

LbGp4

214.8

85.6

Ara, Gal, Rha, Glc (1.5:2.5:0.43:0.23)

Immuno-stimulatory effect by activating the expression of NF-κB and activator protein 1 (AP-1).

(Huang et al. 1998; Peng et al. 2001a)

LbGp5

23.7

8.6

Rha, Ara, Xyl, Gal, Man, Glc (0.33:0.52:0.42:0.94:0.85:1)

 

(Huang et al. 1998)

LbGp5B

23.7

 

Rha, Ara, Glc, Gal (0.1:1:1.2:0.3); Galu (0.9%)

 

(Peng et al. 2001b)

LBP1a-1

115

 

Glc

 

(Duan et al. 2001)

LBP1a-2

94

 

Glc

 

LBP3a-1

103

 

GalA

 

LBP3a-2

82

 

GalA

 

LBP3p

157

92.4

Gal, Glc, Rha, Ara, Man, Xyl (1:2.12:1.25:1.10:1.95:1.76)

Inducing immune responses by increasing the expression of IL-2 and TNF-α at both mRNA and protein levels; inhibiting the growth of transplantable sarcoma while increasing macrophage phagocytosis, spleen lymphocyte proliferation and CTL activity

(Gan et al. 2003, 2004)

LBPA3

66

   

(Zhao et al. 1997)

LBPB1

18

   

LBPC2

12

   

LBPC4

10

 

Glc

 

LBPF1

150

48.2

 

Immuno-enhancement effects:

(Chen et al. 2008)

LBPF2

150

30.5

 

LBPF3

150

34.5

 

LBPF1-5: Activating transcription factors NF-κB and AP-1 in RAW264.7 macrophage cells; inducing TNF-α, IL-1β, IL-12p40 mRNA expression.

(Chen et al. 2009b)

LBPF4

150

20.3

 

LBPF5

290

23.5

 

LBPF4-5: Stimulating mouse splenocyte proliferation; activating transcription factors NFAT and AP-1, increasing CD25 expression and induction of IL-2 and IFN-γ mRNA and protein levels.

Table 2

General compounds related to the anticancer effects of the fruit of Lycium barbarum reported in the literature

Classification

Compound

Molecular formula

MW

Effect

Reference

Proteoglycans

Lycium Barbarum polysaccharides (LBP)

  

Antioxidant and cytoprotective effects on normal cells; apoptotic and antiproliferative effect on cancer cells, such as HL-60, PC3, DU145 and HeLa cells; immunomodulatory effects; enhanced effects on other cancer therapies

(Wanga et al. 2009; Ho et al. 2009; Wu et al. 2010; Gan et al. 2001; Zhu et al. 2010; Luo et al. 2009; Gan et al. 2003)

Phytoalexin

Scopoletin

https://static-content.springer.com/image/art%3A10.1007%2Fs10787-011-0107-3/MediaObjects/10787_2011_107_Figa_HTML.gif

C10H8O4

192.17

Apoptotic and antiproliferative effects on PC3 and HL-60; antioxidant, anti-inflammatory and spasmolytic activities

(Liu et al. 2000; Kim et al. 2005; Shaw et al. 2003; Kim et al. 2004; Oliveira et al. 2001)

Vitamin C analogue

2-O-β-d-Glucopyranosyl-l-ascorbic acid (AA-2βG)

https://static-content.springer.com/image/art%3A10.1007%2Fs10787-011-0107-3/MediaObjects/10787_2011_107_Figb_HTML.gif

C12H18O11

338.27

Apoptotic effect on HeLa cells

(Toyoda-Ono et al. 2004; Zhang et al. 2010)

Table 3

Other ingredients contained in the fruit of Lycium barbarum

Types

Nutrient ingredients

References

Vitamins

B1, B2, B3, B6, C, E

(Qun et al. 1998; Yin and Dang 2008)

Amino acids

18 kinds of amino acids, including all 8 essential amino acids

(Yin and Dang 2008)

Non-proteinogenic amino acids

Taurine, γ-aminobutyric acid, betaine

(Qun et al. 1998; Cao et al. 2003)

Trace minerals

21 trace minerals, such as zinc, iron, copper, calcium, germanium, selenium, and phosphorus

(Yin and Dang 2008)

Essential oil and fatty acid

Hexadecanoic acid, linoleic acid, β-elemene, myristic acid, ethylhexadecanoate

(Altintas et al. 2006)

Carotenoids

Zeaxanthin dipalmitate, β-cryptoxanthin palmitate, zeaxanthin monopalmitate, zeaxanthin, β-carotene, β-cryptoxanthin

(Weller and Breithaupt 2003; Peng et al. 2005; Inbaraj et al. 2008)

Flavonoids

Myricetin, quercetin, kaempferol

(Le et al. 2007)

Others

β-sitosterol, daucositerol, p-coumaric acid, lyciumide A, l-monomenthyl succinate

(Xie et al. 2001; Zou et al. 1999; Hiserodt et al. 2004)

Pharmacological effects against tumour or cancer cells

Apoptosis and cell cycle arrest are the essential mechanisms of the anti-tumourigenesis action of L. barbarum fruit. LBP also contributes to its immunomodulatory and anti-tumour effects. Additionally, reduction of side effects and enhancement of therapeutic effects of other cancer therapies have been reported (Lu and Cheng 1991; Mizuno et al. 2000; Gong et al. 2005).

Anti-tumourigenesis mediated by apoptosis

The antiproliferative or cytotoxic effects of L. barbarum fruit were the focus of several recent investigations. A study found that high doses of crude Lyciumbarbarum extract (≥5 g/L) mediated apoptosis of hepatocellular carcinoma cells by stimulating p53 (Chao et al. 2006).

One of the active ingredients in the fruit of L. barbarum is scopoletin (6-methoxy-7-hydroxycoumarin), which is also named chrysatropic acid, ecopoletin, gelseminic acid and scopoletol. It is a phenolic coumarin and a member of the phytoalexins. Scopoletin has antioxidant properties (Shaw et al. 2003), anti-inflammatory activity (Kim et al. 2004) and spasmolytic action (Oliveira et al. 2001). It exerts apoptotic and antiproliferative effects on prostate cancer cell line (Liu et al. 2000).

The effect of scopoletin on cell proliferation and apoptosis of PC3 cells, human androgen-independent prostate adenocarcinoma cell, was investigated (Liu et al. 2001). Results showed that scopoletin induced a marked time- and dose-dependent inhibition of PC3 cell proliferation. Both reduced protein content and apoptotic morphological changes were observed. Another study demonstrated that scopoletin-induced apoptosis in HL-60 human promyleloleukemic cells accompanied by activation of NF-κB and caspase-3, followed by PARP cleavage and finally DNA fragmentation (Kim et al. 2005).

The recently discovered AA-2βG is another major biologically active component of L. barbarum fruit (Toyoda-Ono et al. 2004). It is a novel stable vitamin C analogue. It was proposed that AA-2βG and vitamin C may share a similar mechanism in upregulating p53 protein expression to induce apoptosis in HeLa cells (Zhang et al. 2010).

LBP is a mixture of proteoglycans and polysaccharides. It mainly consists of arabinose, galactose, glucose, xylose, and a little amount of rhamnose, mannose, and galacturonic acid as its glycosidic part. It was found to have bioactivities such as antioxidant, anticancer, immunological activities and cytoprotective effects on normal cells (Ho et al. 2009; Wu et al. 2010). LBP can dose-dependently suppress cell growth of human leukemia HL-60 cells and human cervical carcinoma HeLa cells (Gan et al. 2001; Zhu et al. 2010). In addition, LBP can concentration- and time-dependently inhibit the proliferation of human prostate cancer cell lines (both PC-3 and DU-145 cells). LBP was found to cause the breakage of DNA strands of PC-3 and DU-145 cells and markedly induce PC-3 and DU-145 cell apoptosis. The ratio of Bcl-2/Bax protein expression after LBP treatments decreases significantly with a dose-response relationship, suggesting modulation of the expression of Bcl-2 and Bax by LBP. In vivo experimental results indicated that LBP significantly inhibited PC-3 tumour growth in nude mice, showing significant reduction in tumour volume and weight in the LBP-treated group (Luo et al. 2009).

Regarding the anticancer mechanism of L. barbarum fruit, calcium may be a potential signaling molecule that takes part in the apoptosis pathways as a result of upstream MAP kinase activation (Zhang et al. 2005). This suggests that LBP boosts the cellular calcium ions concentration which is strongly associated with the signal transduction pathway of apoptosis and affects the chemosensitivity of tumour cells to anticancer agents. Though the direct relationship between LBP and apoptosis is still unclear, this study provides clues that some active ingredients in L. barbarum can mediate apoptosis.

Anti-tumourigenesis mediated by cell cycle arrest

The anti-cancer effects of L. barbarum fruit extract, apart from induction of cancer cell apoptosis, also include inhibition of cancer cell proliferation. A study reported that the extract promoted G2/M phase arrest in hepatocellular carcinoma cells in a dose-dependent manner (Chao et al. 2006). It suggested that the effect may be due to inhibition of NF-κB that alters the expression of regulatory cell cycle proteins like cyclin B and p21WAF1/Cip1.

An investigation (Zhang et al. 2010) had been conducted to study the cell type-, time-, and dose-dependent cytotoxic and antiproliferative activity of AA-2βG on different cancer cells with vitamin C as a control. Both AA-2βG and vitamin C had cytotoxic effects on HS-746T, Colo-320, and HeLa cell lines, and they showed an inhibitory effect on the proliferation of primary vascular endothelial cells and liver cancer cells Bel-7402. AA-2βG-induced cytotoxic effect was the most significant in HeLa cells. The results suggested that AA-2βG, like vitamin C, induced HeLa cell cycle arrest at the G0/G1 phase via downregulating the expression of cell proliferation proteins [such as HSP 27 and HSP 60, muscle pyruvate kinase 2 (PKM2), aldolase A, hnRNP-H1, α-tubulin and mitochondrial inner membrane protein (mitofilin)]. These results also suggest that L. barbarum fruit is an anticancer agent for preventing and treating cervical cancer.

Several studies on the antitumour effects of LBP showed that it can induce cell cycle arrest in S or G0/G1 phase. LBP arrests human hepatoma QGY7703 cells in S phase (Zhang et al. 2005), human gastric cancer MGC-803 and SGC-7901 cells in the G0/G1 and S phases, respectively (Miao et al. 2009), and human colon cancer (both SW480 and Caco-2) cells in G0/G1 phase (Mao et al. 2010). In these studies, LBP had a long-term anti-proliferative effect. Furthermore, changes in cell-cycle-associated protein, cyclins, and cyclin-dependent kinases (CDKs) were consistent with changes in cell-cycle distribution.

Immunomodulatory effects of LBP and their contribution to the anti-tumour effects

Discovering new antitumour therapeutics that can promote immune function has become an important target in cancer immunology. The pharmacological effects of L. barbarum fruit are greatly related to LBP. It was reported that LBP increases the expression of interleukin-2 (IL-2) and tumour necrosis factor-α (TNF-α) both in the mRNA level and protein level in human peripheral blood mononuclear cells (Gan et al. 2003). LBP could also significantly inhibit the growth of transplantable sarcoma S180 while increasing macrophage phagocytosis, spleen lymphocyte proliferation, cytotoxic T lymphocyte (CTL) activity and IL-2 mRNA level. LBP could also suppress lipid peroxidation of immune cells in S180-bearing mice, and such suppression provides an indirect evidence of the improved immune function in S180-bearing mice (Gan et al. 2004). It was reported in a cell cycle study that LBP markedly reduces the percentage of apoptotic cells among splenocytes of mice treated with LBP. Moreover, LBP was found to have higher levels of activated transcription factors NFAT and AP-1, increased CD25 expression, induction of IL-2 and IFN-γ mRNA and protein level (Chen et al. 2008). LBP was demonstrated to activate macrophages by activating transcription factors NF-κB and AP-1, inducing TNF-α production and up-regulating MHC class II molecules (Chen et al. 2009b). LBP-induced maturation of dendritic cells, which are important antigen-presenting cells, by up-regulating expression of CD40, CD80, CD86 and MHC class II molecules, and down-regulating antigen uptake by dendritic cells. The stimulatory activity of dendritic cells to allogenic T cell was elevated as well (Zhu et al. 2007; Chen et al. 2009a).

Reducing side effects and enhancing therapeutic effects of other cancer therapies

LBP could serve as a very useful adjunct to other cancer therapies such as chemotherapy, radiotherapy, and immunotherapy. For instance, rats with LBP pretreatment suffer less cytotoxicity given by doxorubicin (DOX), which is an effective chemotherapeutic agent for treating solid and hematopoietic tumours, without any attenuation on the anti-tumour activity of DOX (Xin et al. 2007, 2010). Pretreatment animals with LBP prevented the loss of myofibrils, improved arrhythmias, normalised serum AST and CK, increased SOD and GSH-Px activity, decreased the MDA level of heart tissues, and reduced mortality in the DOX-treated rats significantly. Another study proposed that 50 mg/kg LBP promoted the peripheral blood recovery from irradiation of 550 cGy X-ray or chemotherapy [by injected with carboplatin (CB)] induced myelosuppressive mice via stimulation of PBMCs to produce G-CSF (Gong et al. 2005). Besides, the effect of treatments lasted significantly longer in patients with different kinds of carcinoma when LAK/IL-2 was combined with LBP (Cao et al. 1994). It showed the response rate of patients treated with LAK/IL-2 and LBP was 24.8% higher than that of patients treated with LAK/IL-2 alone, and the combined treatment also enhanced NK and LAK cell activity. LBP also exerted radiation enhancement effects to acute hypoxic cells of Lewis lung cancer on C57 BL mice (Lu and Cheng 1991).

Lycium barbarum fruit in perspectives

While L. barbarum fruit is widely used in the Chinese communities, there is still a lack of in-depth study on the pharmacological effects of its active ingredients, especially those that exert anticancer functions. Further mechanistic studies can be carried out so as to evaluate the antiproliferative and apoptotic effects of L. barbarum fruit on more cancer cell lines and to reveal the relationship between its active ingredients and its anticancer effects.

Although there are no reports on the toxicity of the herb, two cases of possible interaction with warfarin indicate a potential risk of drug interaction (Lam et al. 2001, 2008). Since the undesirable effects of overdose and the sensitivity of L. barbarum compounds are still unknown, toxicology test is a must to examine its potential harmful effect on normal human cells.

For effective commercialisation of L. barbarum-related health products, standardised protocols for isolating the active ingredients from such a widely available herb are necessary. It is essential to develop formulations to ensure the maximum efficacy and effectiveness of L. barbarum-related health products.

Acknowledgments

This research was financially supported by the Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University and State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Shenzhen. The authors would like to thank Hoi Tin Tong (Hong Kong, China) for providing the herb and support on this project. Special thanks go to Ms. Josephine Hong-Man Leung for proofreading and providing critical comments on the manuscript.

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