Traditional Chinese herbal medicines for treatment of liver fibrosis and cancer: from laboratory discovery to clinical evaluation

Authors


Correspondence
Dr John M. Luk, Department of Surgery, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong, China
e-mail: jmluk@hku.hk

Abstract

Liver disease afflicts over 10% of the world population. This includes chronic hepatitis, alcoholic steatosis, fibrosis, cirrhosis and hepatocellular carcinoma (HCC), which are the most health-threatening conditions drawing considerable attention from medical professionals and scientists. Patients with alcoholism or viral hepatitis are much more likely to have liver cell damage and cirrhosis, and some may eventually develop HCC, which is unfortunately, and very often, a fatal malignancy without cure. While liver surgery is not suitable in many of the HCC cases, patients are mostly given palliative support cares or transarterial chemoembolization or systemic chemotherapies. However, HCC is well known to be a highly chemoresistant tumour, and the response rate is <10–20%. To this end, alternative medicines are being actively sought from other sources with hopes to halt the disease's progression or even eliminate the tumours. Traditional Chinese herbal medicine has begun to gain popularity worldwide for promoting healthcare as well as disease prevention, and been used as conventional or complementary medicines for both treatable and incurable diseases in Asia and the West. In this article, we discuss the laboratory findings and clinical trial studies of Chinese herbal medicines (particularly small molecule compounds) for the treatment of liver disease ranging from fibrosis to liver cancer.

Background

Liver disease, including chronic hepatitis, alcoholic steatosis, fibrosis/cirrhosis, hepatocellular carcinoma (HCC) or liver cancer, afflicts over 10% of the world's population. Approximately 400 million people are chronically infected with hepatitis B virus (HBV); most of them reside in the Asia-Pacific region, such as Southern China and Taiwan, where chronic HBV infection is highly prevalent. Among them, around 25–40% will eventually die of liver disease (viz. cirrhosis with or without HCC) (1). Hence, preventive and therapeutic inventions are necessary to halt or slow down the progression of chronic hepatitis B to cirrhosis, HCC and death. Although nucleoside analogues (e.g. lamivudine, adefovir dipivoxil) and interferon-α (IFN-α) (2) have been clinically proven medicines for curing chronic hepatitis B, there are still no effective therapeutic drugs for fibrosis and HCC. Such unfavourable scenarios have drawn considerable attention from pharmaceutical industries and healthcare professionals.

Liver fibrosis – aetiology, pathogenesis and herbal medicinal compounds

Liver fibrosis is one of the processes that occurs when the liver is damaged, caused by viral activity [particularly, HBV or hepatitis C virus (HCV)], chemicals (e.g. pharmaceuticals, soft drugs, alcohol and pollutants), immune and metabolic disorders or cancer growth. Fibrogenesis is a gradual process of increased secretion and decreased degradation of extracellular materials, which is initiated by activation of hepatic stellate cells (HSCs) (or Ito cells). The damage of hepatocytes, thrombocytes and endothelial cells of the hepatic sinusoid often results in the secretion of multiple cellular factors from the Kupffer cells (resident macrophages line along the liver sinusoids).

Upon activation, the HSCs undergo trans-differentiation into myofibroblasts, with proliferation and massive production (and excretion) of extracellular materials, which gradually accumulate and lead to liver fibrosis. Because fibrosis is a common development in a variety of chronic liver diseases, its prevention is of great importance. Unfortunately, detection of the underlying liver disease is often delayed and uncertain. Targeting of activated HSCs has drawn considerable interest for drug design (3) and development for treatment of liver fibrosis in Western pharmaceutical industries. Nevertheless, through centuries of clinical practices in the Chinese medicines, there are a number of candidate drugs (small molecular compounds) derived from the prevailing herbal formulae or composites that have been proven to be effective and are warranted for further exploration or clinical investigations to treat liver fibrosis.

Salvianolic acid B

Salvia is one of the most commonly used agents for treating fibrosis. Salvianolic acid B (SAB; also called magnesium lithospermate B) is a major water-soluble polyphenolic acid (M.W. 718, Fig. 1A) extracted from Radix Salviae miltiorrhizae (Sm), which is a common herbal medicine that has been clinically used in China for thousands of years as a blood-circulation accelerating and/or antioxidant agent. There are nine activated phenolic hydroxyl groups (4) that may be responsible for the release of active hydrogen to block lipid peroxidation reaction (5). SAB has been shown to improve renal function by accelerating renal blood circulation (6–12). Sm was used in treatment of late-stage schistosomial cirrhosis and splenomegaly in 1958 (13). Later, Yu et al. (14) used its injection to treat hepatitis B in early-stage cirrhosis; biopsy examination before and after treatment indicated that Sm could effectively alleviate the pathological changes of liver fibrosis.

Figure 1.

 Chemical formulae of selected herbal compounds (A) for treating liver fibrosis and (B) for hepatocellular carcinoma therapy.

From 1991, studies of SAB on improving acute and chronic liver injuries were initiated. In a d-galactosamine-induced acute liver injury rat model, SAB significantly decreased the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and enhanced the total prostaglandin content in liver mesenchymal cells in injured rats (15). It also inhibited the cyclooxygenase activity in adherent cells in the rat liver (16). In 1994, Shigematsu et al. (17) also demonstrated that SAB could inhibit collagen secretion of human skin fibroblast.

In a double-blinded, randomized control study (18), 60 patients who had been clinically diagnosed with liver fibrosis with hepatitis B were recruited to receive 6-month regimens of either (i), SAB or (ii), IFN-γ treatments. For the SAB group, the reversal rate of fibrotic stage was 36.67% vs. the IFN-γ group at 30.0%, whereas the inflammatory alleviation rate was 40.0% in the SAB group and 36.67% in the IFN-γ group respectively. Liver fibrotic scores by ultrasound imaging were also lower in the SAB group than the IFN-γ group [hyaluronic acid (HA) 36.7% vs. 80%, type IV collagen (IV-C) 3.3% vs. 23.2%]. As regards the liver function biochemical tests, patients in the SAB group were found to have lower ALT/AST activity and total bilirubin content, and no apparent side effects were observed.

The drug-action mechanisms of SAB in treating liver fibrosis may be multifaceted and very complex. Based on the laboratory research findings, one of the proposed mechanisms is to inhibit the activated HSCs that proliferate and contribute collagen substances to the hepatic extracellular matrix (ECM), forming a fibrotic mass. Another possible mechanism is to induce apoptosis of activated stellate cells (Fig. 2).

Figure 2.

 Schematic model of drug-action mechanisms of herbal compounds for liver disease treatment.

Inhibiting hepatic stellate cell proliferation

Studies of SAB, with special focus on its effect on HSC proliferation, showed that SAB could inhibit HSC proliferation, slowing down ECM deposition. Coculture of rat HSCs with SAB showed that SAB concentrations of 0.1, 1 and 10 μM could inhibit cell proliferation as demonstrated by 3H-thymide incorporation analysis, whereas a dosage of 100 μM would be cytotoxic (19). Primary cultured rat HSCs incubated with 1 and 10 μM SAB arrested cell cycle from the G1 phase to the S phase by suppressing G1 phase cell cycle-related proteins, for example, cyclin D1, cyclin E, CDK2 and CDK4 expressions (20). Platelet-derived growth factor (PDGF) is the most potent mitogen in stimulating HSC proliferation (21); its intracellular signalling involved the mitogen-activated protein kinase (MAPK) pathway in HSCs (22). SAB inhibited PDGF-stimulated primary cultured rats HSC proliferation (21) by inhibiting MAPK activity (23). Oxidative stress is an important factor stimulating HSC proliferation and angiogenesis via COX-2 and hypoxia-inducible factor (HIF)-1α signalling (24). SAB also inhibited malondialdehyde (MDA)-stimulated primary cultured rat HSC proliferation (25), suggesting that the effect of SAB suppressing HSC proliferation is related to its anti-oxidation properties.

Inhibiting hepatic stellate cell collagen production via the transforming growth factor-β–Smad signalling pathway

During liver fibrogenesis upon liver damage, HSCs become the major source of types I and III high-density interstitial collagens, replacing the types IV and VI collagen of low density that is deposited under normal physiologic conditions. Transforming growth factor (TGF)-β1 is the most potent stimulus responsible for stimulation of ECM synthesis in activated HSCs in an autocrine manner (26). In TGF-β1-stimulated primary cultured rat HSCs, the expression of type I collagen gene was markedly suppressed by treatment with various dosages of SAB (27). Primary HSCs stimulated with 100 pM of TGF-β1 increased the basal collagen expression by 207.7% on the fourth day. After treatment with 1 and 10 μM SAB for 24 h, type I collagen expression was reduced by 68.6% and 56.1%, respectively, when compared with placebo control. TGF-β1 transduces its signalling effects in HSC by binding its receptors (types I and II), and the fibrogenic downstream signalling is mediated by the Smad signalling proteins (28). The known antifibrogenic mechanism of SAB is by suppressing the Smad2/3 protein expression and also inhibiting the nuclear translocation of phosphorylated Smad 2 protein (29).

Oxymatrine [C15H24N2O2·H2O; MW: 282] (Fig. 1A)

Oxymatrine (OM; also named kwoninone), a kind of alkaloid extracted from Chinese herbs Sophora alopecuraides L or Sophora flavescens Ait, has extensive pharmacological effects, i.e., anti-inflammation, antibacteria, antivirus, antitumour and immunosuppression. Among all these biological effects, the antiviral activity of OM warrants its implication as a prophylactic agent that potentially prevents fibrosis from development among chronic hepatitis cohorts, and indeed there were in vitro and clinical studies concerning its antihepatitis effect. In an in vivo study using cells that stably expressed HCV, intracellular HCV RNA was found to be suppressed by OM treatment significantly. (30). The antiviral effect of OM was further demonstrated in a clinical trial of a total of 46 hepatitis patients. Approximately 47% of those who received an intramuscular injection of OM for three months demonstrated serological conversion of HCV RNA from positive to negative, compared with the conversion rate of about 5.6% among those who received liver-protective agents alone (31). These encouraging results set the stage for the more systemic, large-scale clinical trial with a total of 216 chronic hepatitis B patients of whom 108 received an OM capsule, 36 received an OM injection and 72 received placebo. After the 24-week treatment, the complete response rate was about 25–33% among patients receiving either OM capsule or injection, who showed negative HBV DNA and hepatitis B early antigen (HBeAg) levels and whose ALT level returned to normal (32).

In addition to its antiviral activity, OM has been determined to be capable of acting directly on fibrosis development. In a randomized, double-blind controlled, multicentre clinical study, 144 patients participated in a 52-week course of an OM regimen. Significant improvement in hepatic fibrosis and inflammatory activity based on a semi-quantitative scoring system was achieved in the OM group when compared with the placebo. The total effective rate of the treatment was 48.00%, whereas that in the placebo group was 4.17%. Serum markers of hepatic fibrosis such as HA and type III procollagenic peptide in the OM group were also improved (33).

In the hepatic fibrosis animal model, carbon tetrachloride (CCl4) stimulates the secretion of tumour necrosis factor-α (TNF-α) and interleukin-10 (IL-10) by Kupffer cells. TNF-α plays a bridging role between inflammatory reaction and immune response, and induces the activation of intrahepatic T-helper type 2 (Th2) cells and thus increases the IL-10 level in liver tissues (34). Subsequently, IL-10 inhibits the Th1 activity and reduces the Th1 cytokines, IFN-γ and IL-2 levels. Herein, IFN-γ is a strong antifibrotic factor, while IL-2 plays a central role in the immune responses. OM was found to upregulate the expression of IFN-γ and IL-2, and downregulate the expression of TNF-α and IL-10 in liver tissues (35). In rat liver tissues undergoing CCl4-induced fibrogenesis, the matrix metalloproteinases (MMPs)/tissue inhibitor of metalloproteinases (TIMPs) balance involved in the ECM remodelling was severely perturbed. OM effectively inhibited the expression of the TIMP-1 (36) and MMP2 (37), and by inhibiting the expression of Smad 3 protein, thus modulating TGF-β1 signal transduction (38).

Oxymatrine could also inhibit fibroblastic proliferation and its expression of type III collagen mRNA in vivo (39). When comparing the effects of OM and IFN-α on cultured rat HSCs in vitro, OM was found to have inhibitory effects similar to IFN-α (40, 41). Prophylactic effects on d-galactosamine-induced rat liver fibrosis by suppressing HSC activation probably through antilipoperoxidation activity have also been reported (42).

Tetrandrine (Fig. 1A)

Tetrandrine (Tet) is a bis-benzyl isoquinoline alkaloid derived from Stephania tetrandra S. Moore, a Chinese herbal medicine, and is a calcium ion-channel blocker (43), which has been used in China to treat liver and lung fibrosis in clinics. After taking Tet orally for 18 months, serum procollagen III peptide and HA concentration were significantly reduced in 33 patients with liver cirrhosis. Deposition of ECM and collagen (both types I and III) were obviously attenuated (44). Among the 115 chronic hepatitis patients taking Tet orally up to 6 months, serum HA and procollagen peptide were obviously reduced, inflammatory cell infiltration had lessened, liver fibrosis had disappeared in 14 of 115 patients, collagen deposition in liver tissues was attenuated in 54 of 115 patients and the numbers of HSC had reduced (43). Among cirrhotic patients taking Tet orally for two consecutive years, the oesophageal variceal pressure and the portal blood flow with portal hypertension were significantly reduced. The proportion of patients with no recurrent gastrointestinal bleeding who were taking Tet for 2 years was 87.9%. All these results suggested that Tet would be effective for cirrhotic patients (45).

Treatment with Tet in bile duct ligation (BDL)-induced fibrotic rats reduced serum AST, ALT and alkaline phosphatase levels to 72%, 52% and 51%, respectively, when compared with no treatment. The liver hydroxyproline contents in Tet-treated rats were also reduced to 65% of that in control animals. The morphological features of fibrotic liver were also improved in the Tet-treated group (46). Similarly, necrosis and fibrogenesis in Tet-treated rat livers were significantly attenuated (47). The proposed antifibrotic mechanisms are associated with decreased nitric oxide (NO) production and lower inducible NO synthase (iNOS) activity (48, 49). Portal hypertension is one of the significant pathologic manifestations of cirrhosis patients. Upper gastrointestinal haemorrhage caused by portal hypertension commonly leads to the patient mortality. In a dose-dependent manner in a bolus infusion, Tet could lower the portal venous pressure, mean arterial pressure and total peripheral resistance. The effects of Tet on portal hypotension can be attributed to its actions of i, blocking voltage- and receptor-operated Ca2+ channels in vascular smooth muscle cells; ii, inhibiting intracellular Ca2+ mobilization and iii, dilating peripheral blood vessels (50–53).

The effect of Tet on HSC activation and proliferation has also been addressed. Animals receiving Tet treatment had a lower number of HSC and smooth muscle α-actin expression in CCl4-induced liver fibrotic tissues (54). Furthermore, Tet was shown to markedly attenuate the collagen and DNA synthesis in primary cultured rat HSC, by suppressing HSC activation (55), blocking PDGF signalling (56), apoptosis induction (57), downregulation of the autocrine of the TGF-β1–PDGF–PDGF-Rβ1 loop (58) and upregulation of Smad 7 protein to inhibit TGF-mediated matrix synthesis (55, 59). There is also a report that Tet could improve mitochondria membrane fluidity and lessen the Ca2+ concentration by inhibiting lipid peroxidation (60).

Curcumin (Fig. 1A)

Curcumin is a polyphenol compound from the Chinese herb, Curcuma longa L, which is used for wound healing as well as skin and gut diseases. Its molecular structure is composed of both phenol and diarylheptanoid (61), and is regarded as a natural potent antioxidant with other pharmacological properties, such as antitumour, anti-inflammation and antifibrosis (62). Dietary administration of curcumin was shown to improve both acute and subacute liver injuries (63) as well as liver fibrosis induced by CCl4 (64). The possible drug action mechanisms included inhibition of HSC proliferation (65–70) and activation (71), and apoptosis induction (68, 72). Curcumin could also inhibit ECM secretion by HSCs (66) by modulating the expressions and activities of MMPs (73).

Incubation of HSCs with the ferric nitrilotriacetate complex produces reactive oxygen species, leading to significant increases in intracellular MDA and glutathione (GSH) that are associated with decreased superoxide dismutase and glutathione peroxidase (GSH-PX) activities. These unfavourable effects could be reversed by curcumin (74). Oxidative stress causes HSC activation and liver fibrogenesis. Peroxisome proliferation-activated receptors (PPARs) belong to the superfamily of nuclear receptors, and expression of PPARγ inhibited PDGF-induced cell proliferation (75, 76). The level of PPARγ and its trans-activing activity are diminished during HSC activation in vitro (77). Curcumin enhanced PPARγ gene expression and its activity in activated HSC in vitro (68), and reduced apoptosis and the extracellular gene expression of HSC (70).

Composite formula

Besides the promising small molecule compounds isolated or derived from the Chinese medicines, it is also worth mentioning that some complex formulas, single herbs and active components are still being prescribed by Chinese medicine practitioners for treating liver fibrosis. They are summarized as follows:

  • (i)Modified minor bupleurum combination (Xiao Chaihu Tang) plus salvia injection for patients with chronic hepatitis B.
  • (ii)Bupleurum granules (Chaihu Chongji), with undisclosed ingredients other than bupleurum for chronic hepatitis B.
  • (iii)Modified persica and carthamus combination (Tao Hong Siwu Tang) for chemical-induced liver damage.
  • (iv)861 granules, also called composite salvia granules (comprised of 10 herbs, the main ones being astragalus, salvia and spatholobus), for patients with chronic liver diseases.
  • (v)Ruangan Yin (see the above report on ruangan granules, which includes the list of ingredients); the review includes earlier work with this formula.
  • (vi)Guzhang tablet (which includes notoginseng, salvia, red peony, tang-kuei and curcuma) for patients with liver cirrhosis.
  • (vii)Fuganjang granules (which includes salvia, red peony, tang-kuei, bupleurum, astragalus and curcuma).
  • (viii)Persica extract and cordyceps inducing inhibition of fibrosis.
  • (ix)Notoginseng (sanqi).

Current uses of traditional Chinese medicine in treating HCC

Hepatocellular carcinoma is the second leading cause of cancer death in southern China. The late detection of HCC often results in the poor prognosis of HCC patients. Aetiological studies have revealed chronic viral hepatitis infection by hepatitis B or C virus, alcohol abuse, environmental chemical insults and genetic alternation are risk factors of developing HCC (78). Treatment of HCC heavily relies on surgical interventions including hepatectomy and percutaneous radiofrequency ablation (79, 80), while there are still no effective chemotherapeutics for HCC, which is well known for its resistance to many of the current drugs.

Thus, development of novel therapeutic approaches has attracted considerable interest and this area of research has gained momentum from recent studies on the mechanistic link between cancer and inflammation. It is now the current paradigm that inflammatory cells infiltrate into the stromal microenvironment of tumour where pro-inflammatory cytokines play important roles in promoting tumour cell proliferation, invasion, migration and metastasis (81, 82). Novel therapeutic candidates targeting the inflammatory signalling pathway, especially the nuclear factor-κB (NF-κB), demonstrated certain inhibitory effects on cytokine productions responsible for tumour proliferation (83, 84).

Certain Chinese herbal medicines have been administrated as an anti-inflammatory regimen for many years, and some of their active components or ingredients have been extracted and characterized, enhancing our knowledge about their biologic functions through in vitro and in vivo studies. Four most commonly used active components, glycyrrhizin (GL), triptolide, celastrol and berberine, are discussed in the following, which demonstrate both anti-inflammatory and antineoplastic properties, such characteristics rendering them attractive candidates for the development of novel chemotherapeutics inflammation-related HCC.

Glycyrrhizin (Fig. 1B)

Licorice root (Glycyrrhizia uralensis) has been used in an anti-inflammatory regimen in Chinese medicine for a long period of time, and its active component glycyrrhizin (GL) is responsible for the immunomodulatory property. The extracted substance, glycyrrhizin sulphate, has been observed in laboratory tests to inhibit HIV replication, interfere with virus-to-cell binding and cell-to-cell infection, and induce IFN activity (85). The mechanisms of hepatoprotection are diverse and include antioxidant activity, direct antiviral effects, enhancement of IFN production, enhanced antibody production and enhancement of extrathymic T-Cell activity in the liver (86, 87). In most Japanese trials for the treatment of hepatitis, strong neominophagen-C (SNMC), which contains 40 mg glyzyhhrizin, 20 mg cysteine and 400 mg glycine in 20 mL of saline solution, was used for intravenous infusion. Comparable therapeutic levels of GL are also available in tablet form for oral administration to treat a wide variety of conditions such as gastric ulcers, gastritis, inflammatory disorders and female hormone-related problems.

Cohorts of viral hepatitis are at a high risk of developing liver cirrhosis and HCC. The beneficial effects of GL on treating chronic inflammatory liver disease have been investigated, and preliminary findings from both animal models and clinical study among hepatitis cohorts appear to be promising. Diethyl nitrosamine (DEN)-treated mice represent a model of chronic viral hepatitis as it mimics the biochemical presentation of hepatitis patients, in whom synthesis of nitrate and nitrosamine is upregulated (88, 89). A study on DEN-treated mice demonstrated that GL could reduce the carcinogenesis rate of HCC by 40% (90). Later, a clinical study demonstrated that an intravenous injection of GL was effective in lowering the incidence rate of HCC among chronic hepatitis C cohorts who were resistant to IFN-γ treatment. Liver functions among these patients were significantly improved as indicated by the serum liver enzyme levels (91, 92). Some suggested that the protective effect of GL might be attributed to its anti-oxidizing property (93). Another possible mechanism is to alter the viral antigen expression on hepatocytes, thereby reducing the inflammation in liver. GL has been used for the treatment of chronic hepatitis B in Japan and has been found to improve liver functions, with occasional complete recovery from hepatitis (86). Despite the clinical benefits, the long-term use of GL for treatment of chronic hepatic fibrosis has been limited by its potential side effects of systemic mineralocorticoid action or aldosteronism after an intravenous administration (3). GL is metabolized into glycyrrhetic acid (GA) in the gastrointestinal tract after oral intake. The structure–bioactivity relationship of GL and GA has been determined, and the GA was found to be the most active moiety. Therefore, it would be worth determining whether GA also exerts a similar prophylactic effect on HCC occurrence among chronic hepatitis patients, and to evaluate its toxicity.

The roles of GL or GA in the prevention of HCC aetiology have been examined through in vitro and animal models of HCC. GL also protects liver against chemical-induced carcinogenicity, as revealed by studies on CCl4– and aflatoxin B1 (AFB1)-treated animal models. CCl4 is a well-known hepatotoxin, which acts as a free radical-forming agent that causes lipid peroxidation of the plasma membrane. The damaged liver is susceptible to further progression towards cirrhosis and HCC (94). GL was shown to protect hepatocytes against CCl4-induced hepatocellular necrosis in rats (95). AFB1 is a potent carcinogenic agent because of its ability to produce free radicals that cause chromosomal damages (96). On the other hand, an in vitro study suggested that GA could protect liver cells through metabolic upregulations of detoxifying enzyme systems including the glutathione S-transferase and cytochrome P450 system, facilitating biotransformations and eliminations of mycotoxin (97).

In spite of these beneficial effects, the pharmacologic actions of GA and GL remain sketchy. GL has been proposed to induce apoptosis in the hepatoma cell line HLE or act on an activator protein-1 (AP-1)-responsive element to inhibit cellular transformation (98, 99). Global genomic analysis of licorice-treated hepatocytes revealed over-expressions of genes relating to biotransformation phase II enzymes (DT-diaphorase and glutathione S-transferase Pi subunit) and cell motility (urokinase-type plasminogen activator surface receptor and plasminogen activator inhibitor-1) (100).

Tripterygium wilfordii active components

Tripterygium wilfordii (TW), also called ‘Thunder of God Vine’, is well known for its anti-inflammatory property, which has widely been used in the treatment of various immunologic disorders (101, 102) and potential use in organ transplantation (3). More interestingly, two active components isolated from TW; triptolide and celastrol (Fig. 1B), were demonstrated to display antineoplastic activity towards different cancerous types including HCC.

Triptolide was first demonstrated to exhibit an antileukaemic property (103, 104), and later, was also effective in eradicating other cancers such as breast (105), lung (106), T-lymphocyte and liver (107). Possible drug action is focused on apoptosis induction in the HCC cell line (107), and sensitization of cancer cells to TNF-α-induced apoptosis by suppressing the NF-κB activation in tumour cells (106).

Celastrol has also been investigated for its antitumour function acting on different cancer cell lines for its antiproliferation and pro-apoptosis activities (108). The antineoplastic activity of celastrol on HCC has not been documented; however, it has a broad spectrum of target cancer cell types, making it a promising candidate for a novel intervention for manifestation of any neoplasm secondary to HCC. The mechanism of celastrol action on various cancers remains to be fully understood. An in vivo study using nude mice inoculated with human prostate cancer cells led to the idea that celastrol is a potent proteasome inhibitor that inhibits endogenous protein degradation through a ubiquitin/proteasome pathway (19). Inhibition of such a degradation led to cellular accumulation of certain proteins that may trigger apoptotic events (109–111).

Berberine

An active component of Coptis chinensis, berberine (Fig. 1B), was shown to be capable of protecting liver cells against chemical carcinogenesis. In animals treated with either 20-methylcholanthrene- or N-nitrosodiethylamine, berberine was able to prevent liver injury as exemplified by decreased levels of γ-glutamyl transpeptidase and glutathione S-transferase, markers for liver injury (112). It was also shown to inhibit tert-butyl hydroperoxide (t-BHP)-induced cytotoxicity and lipid peroxidation of rat livers (113). The protective capacity described can probably be attributed to its role as a free radical scavenger.

Besides, berberine is cytotoxic to a variety of HCC cell lines, by inducing apoptosis through the caspases–mitochondria pathway (22), inhibiting tumour cell proliferation (114) and shortening the S phase of the cell cycle (16). Berberine may have a biological function of inhibiting the AP-1 (115) and cyclooxygenase-2 (COX-2) activity (116). These are key regulators in cellular proliferation, carcinogenesis and angiogenesis respectively.

Further study on COX-2 expression in HCC revealed its clinical correlation with tumour differentiation grades. Administration of a specific COX-2 inhibitor resulted in the suppression of angiogenesis and in vivo tumour growth in gastrointestinal cancer xenograft (117). COX-2 inhibition by berberine in HCC has not yet been addressed, however, there exists a similar report in colon cancer cells (118).

Summary

Despite studies for decades as well as advancement of our understanding of the molecular pathogenesis and novel lead drug candidates, there are still limited effective therapeutic interventions for liver fibrosis, cirrhosis and HCC.

According to the encyclopaedic knowledge on herbal medicine regimen and clinical experience accumulated for centuries, TCM can provide new avenues for alternative treatments of liver disease (Table 1). This article provided a systemic review of active compounds isolated from herbal medicine, such as SAB, OM, Tet and curcumin, which have been found to suppress ECM deposition through their modulating effects on HSC activation and proliferation. The protective effect of GL against chemical-induced carcinogenicity has been described, and berberine has been shown to display a cytotoxic effect on HCC. Nevertheless, it is necessary to address the fact that the anti-HCC effect of these compounds may be a result of subsiding chronic liver inflammation as well. Recent studies on the mechanistic link between inflammation and cancer have readily shed light on those well-known anti-inflammatory agents like triptolide and celastrol for their potential antineoplastic effect on HCC. The clinical applications of these active compounds warrant further randomized, controlled clinical trials from multiple centres on different patient cohorts of liver diseases.

Table 1.   Summary of traditional Chinese medicines' drug actions on hepatic fibrogenesis and carcinogenesis
Pharmacological actionsActive compoundHerbal source
  1. HBV, hepatitis B virus; HCV, hepatitis C virus; HSC, hepatic stellate cell.

Apoptosis inductionBerberineCoptis chinensis
CelastrolTripterygium wilfordii
CurcuminCurcuma longa L
Chemical-induced carcinogenesisBerberineCoptis chinensis
GlycyrrhizinGlycyrrhizia uralensis
Glycyrrhetic acidGlycyrrhizia uralensis
Immunomodulation/immunosuppressionCurcuminCurcuma longa L
GlycyrrhizinGlycyrrhizia uralensis
OxymatrineSophora alopecuraides L
TetrandrineStephania tetrandra S
TriptolideTripterygium wilfordii
Lipid peroxidationSalvianolic acidRadix Salviae miltiorrhizae
GlycyrrhizinGlycyrrhizia uralensis
BerberineCoptis chinensis
TetrandrineStephania tetrandra S
OxymatrineSophora alopecuraides L
HSC activation and proliferationCelastrolTripterygium wilfordii
Salvianolic acidRadix Salviae miltiorrhizae
Antiviral activities (both HBV and HCV)OxymatrineSophora alopecuraides L
GlycyrrhizinGlycyrrhizia uralensis

Acknowledgements

This work was supported by the Research Grants Council of Hong Kong (HKU7320/02M) and the CRCG seed funding grant and the Sun Chieh Yeh Research Foundation for Hepatobiliary and Pancreatic and Surgery of the University of Hong Kong. The authors would also like to thank Dr Li Kwok Sing for his comments and suggestions.

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