Garlic essential oil protects against obesity-triggered nonalcoholic fatty liver disease through modulation of lipid metabolism and oxidative stress.

This study investigated the protective properties of garlic essential oil (GEO) and its major organosulfur component (diallyl disulfide, DADS) against the development of nonalcoholic fatty liver disease (NAFLD). C57BL/6J mice were fed a normal or high-fat diet (HFD) with/without GEO (25, 50, and 100 mg/kg) or DADS (10 and 20 mg/kg) for 12 weeks. GEO and DADS dose-dependently exerted antiobesity and antihyperlipidemic effects by reducing HFD-induced body weight gain, adipose tissue weight, and serum biochemical parameters. Administration of 50 and 100 mg/kg GEO and 20 mg/kg DADS significantly decreased the release of pro-inflammatory cytokines in liver, accompanied by elevated antioxidant capacity via inhibition of cytochrome P450 2E1 expression during NAFLD development. The anti-NAFLD effects of GEO and DADS were mediated through down-regulation of sterol regulatory element binding protein-1c, acetyl-CoA carboxylase, fatty acid synthase, and 3-hydroxy-3-methylglutaryl-coenzyme A reductase, as well as stimulation of peroxisome proliferator-activated receptor α and carnitine palmitoyltransferase-1. These results demonstrate that GEO and DADS dose-dependently protected obese mice with long-term HFD-induced NAFLD from lipid accumulation, inflammation, and oxidative damage by ameliorating lipid metabolic disorders and oxidative stress. The dose of 20 mg/kg DADS was equally as effective in preventing NAFLD as 50 mg/kg GEO containing the same amount of DADS, which demonstrates that DADS may be the main bioactive component in GEO.

Molecular mechanisms of garlic-derived allyl sulfides in the inhibition of skin cancer progression.

Skin cancer is a serious concern whose incidence is increasing at an alarming rate. Allyl sulfides-i.e., sulfur metabolites in garlic oil-have been demonstrated to have anticancer activity against several cancer types, although the mechanisms underlying these effects remain enigmatic. Our previous study showed that diallyl trisulfide (DATS) is more potent than mono- and disulfides against skin cancer. DATS inhibits cell growth of human melanoma A375 cells and basal cell carcinoma (BCC) cells by increasing the levels of intracellular reactive oxygen species (ROS) and DNA damage and by inducing G2/M arrest, endoplasmic reticulum (ER) stress, and mitochondria-mediated apoptosis, including the caspase-dependent and -independent pathways. This short review focuses on the molecular mechanisms of garlic-derived allyl sulfides on skin cancer prevention.

Diallyl trisulfide induces apoptosis of human basal cell carcinoma cells via endoplasmic reticulum stress and the mitochondrial pathway.

Diallyl trisulfide (DATS), an active component of garlic oil, has attracted much attention because of its anticancer effect on several types of cancers. However, the mechanism of DATS-induced apoptosis of basal cell carcinoma (BCC) is not fully understood. In the present study, we revealed that DATS-mediated dose-dependent induction of apoptosis in BCC cells was associated with intracellular reactive oxygen species accumulation and disrupted mitochondrial membrane potential. Western analysis demonstrated concordant expression of molecules involved in mitochondrial apoptosis, including DATS-associated increases in phospho-p53, proapoptotic Bax, and decreases in antiapoptotic Bcl-2 and Bcl-xl in BCC cells. Moreover, DATS induced the release of cytochrome c, apoptosis-inducing factor, and HtrA2/Omi into the cytoplasm, and activated factors downstream of caspase-dependent and caspase-independent apoptosis, including nuclear translocation of apoptotic-inducing factor and endonuclease G and the caspase cascade. These results were confirmed by pretreatment with the antioxidant N-acetyl-L-cysteine and the caspase inhibitor (z-VAD-fmk), the latter of which did not completely enhance the viability of DATS-treated BBC cells. Exposure to DATS additionally induced endogenous endoplasmic reticulum stress markers and intracellular Ca2⁺ mobilization, upregulation of Bip/GRP78 and CHOP/GADD153, and activation of caspase-4. Our findings suggest that DATS exerts chemopreventive potential via ER stress and the mitochondrial pathway in BCC cells.

2-(3-Methoxyphenyl)-6, 7-methylenedioxoquinolin-4-one, a novel synthetic compound, inhibited migration and invasion in TSGH8301 human bladder cancer cells.

Matrix metalloproteinases (MMPs) play an important role in the invasion, metastasis and angiogenesis of cancer cells. Many agents have been shown to inhibit the cancer cell migration and invasion by suppression of MMPs. 2-(3-Methoxyphenyl)-6,7-methylenedioxoquinolin-4-one (MMEQ) is a derivative compound synthesized from quinolin and the purpose of this study is to determine whether or not cell migration would be reduced in human bladder cancer TSGH8301 cells after MMEQ treatment. Wound healing assay and boyden chamber assay were used in cell migration and invasion determinations. Cell migration and invasion inhibited by MMEQ exerted an inhibitory effect on the sevenless homolog-1 (SOS-1), protein kinase c (PKC), extracellular signal-regulated kinase (ERK) and Rho A for causing the inhibitions of MMP-2 and -9, and then followed by the inhibitions of invasion and migration. MMEQ also affected FAK, PI3K or inhibited growth factor receptor-bound protein 2 (GRB2), nuclear factor kappaB (NF-κB), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) for cell proliferation inhibition. Therefore, MMEQ may serve as a drug in the prevention of tumor metastasis of bladder cancer in the future.

Dietary effect of Antrodia Camphorate extracts on immune responses in WEHI-3 leukemia BALB/c mice.

Antrodia camphorata has been recognized to be a traditional Chinese medicine for abdominal pain, diarrhea, and to protect against hepatitis virus infection. Several ingredients derived from A. camphorata possess various pharmacological and biological activities such as antioxidant and anticancer. In this study, its ability to promote immune responses and to exhibited antileukemia activity in WEHI-3 leukemia BALB/c mice were investigated. The results indicated A. camphorata significantly prolonged the survival rate and prevented the body weight loss in leukemia mice. Four mg/kg of A. camphorata treatment significantly decreased the weight of the spleen. Both doses (2 and 4 mg/kg) of A. camphorata did not affect Mac-3 marker in leukocytes. However, the 4 mg/kg of A. camphorata decreased the levels of CD11b and both doses of treatment increased CD3 and CD19. With lipopolysaccharide stimulation, the 4 mg/kg of A. camphorata promoted the significant proliferation of leukocytes; but with concanavalin A stimulation, both doses promoted the significant proliferation of leukocytes. YAC-1 target cells were killed by NK cells from the mice after treatment with A. camphorata at 4 mg/kg in target cells at a ratio of 50:1. The percentage of macrophages with phagocyted at A. camphorata treatment increased, and these effects were in dose-dependent manners.

Gallic acid inhibits murine leukemia WEHI-3 cells in vivo and promotes macrophage phagocytosis.

Gallic acid is a polyhydroxyphenolic compound which can be found in various natural products. It is recognized to be an excellent free radical scavenger and has been shown to induce apoptosis in lung cancer and leukemia cells. No report has addressed whether gallic acid affects mouse leukemia cells in vivo. In this study, we examined the in vivo effects of gallic acid on leukemia WEHI-3 cells and on macrophage phagocytosis. Gallic acid caused a significant decrease in the weights of the spleens and livers from BALB/c mice. One of the major characteristic of WEHI-3 leukemia is the enlarged spleen in mice after i.p. injection of WEHI-3 cells. Gallic acid did not affect the percentages of CD3, CD11 and CD19 markers but decreased the percentage of Mac-3 in a high-dose (80 mg/kg) treatment while promoting Mac-3 levels in a low-dose (40 mg/kg) treatment. Gallic acid promoted the activity of macrophage phagocytosis in the white blood cells from peripheral blood mononuclear cells (PBMCs) at 40 and 80 mg/kg treatment doses, but decreased the macrophage phagocytosis in isolated peritoneal cells at the 80 mg/kg dose.

Emodin induces apoptosis of human tongue squamous cancer SCC-4 cells through reactive oxygen species and mitochondria-dependent pathways.

Emodin was isolated from Rheum palmatum L. and exhibits an anticancer effect on human cancer cell lines, however, the molecular mechanisms of emodin-mediated apoptosis in human tongue cancer cells have not been fully investigated. In this study, treatment of human tongue cancer SCC-4 cells with various concentrations of emodin led to G2/M arrest through promoted p21 and Chk2 expression but inhibited cyclin B1 and cdc2; it also induced apoptosis through the pronounced release of cytochrome c from mitochondria and activations of caspase-9 and caspase-3. These events were accompanied by the generation of reactive oxygen species (ROS), disruption of mitochondrial membrane potential (delta psi(m)) and a decrease in the ratio of mitochondrial Bcl-2 and Bax content; emodin also promoted the levels of GADD153 and GRP78. The free radical scavenger N-acetylcysteine and caspase inhibitors markedly blocked emodin-induced apoptosis. Taken together, these findings suggest that emodin mediated oxidative injury (DNA damage) based on ROS production and ER stress based on the levels of GADD153 and GRP78 that acts as an early and upstream change in the cell death cascade to caspase- and mitochondria-dependent signaling pathways, triggers mitochondrial dysfunction from Bcl-2 and Bax modulation, mitochondrial cytochrome c release and caspase activation, consequently leading to apoptosis in SCC-4 cells.

Diallyl disulfide (DADS) induces apoptosis in human cervical cancer Ca Ski cells via reactive oxygen species and Ca2+-dependent mitochondria-dependent pathway.

The mechanisms of apoptosis induced by diallyl disulfide (DADS) were explored in human cervical cancer Ca Ski cells. Flow cytometric analysis, DNA gel electrophoresis and DAPI staining demonstrated that DADS induced apoptosis in Ca Ski cells. DADS induced apoptosis through the production of reactive oxygen species and Ca2+, and induced abrogation of mitochondrial membrane potential (Deltapsim) and cleavage of Bid protein (t-Bid). DADS increased the levels of p53, p21 and Bax, but caused a decrease in the level of Bcl-2. DADS also promoted the activities of caspase-3 leading to DNA fragmentation, thus indicating that DADS-induced apoptosis is caspase-3 dependent. In addition, DADS induced an increase in the level of cytochrome c in the cytoplasm, which was released from mitochondria. BAPTA attenuated the Deltapsim abrogation and significantly diminished the occurrence of DADS-induced apoptosis in Ca Ski cells. In conclusion, DADS-induced apoptosis occurs via production of ROS and caspase-3 and a mitochondria-dependent pathway in Ca Ski cells.

The role of mitochondria in bee venom-induced apoptosis in human breast cancer MCF7 cells.

Our previous studies have shown that bee venom (BV) can induce apoptosis in human cervical cancer Ca Ski cells, but it can also affect human breast cancer cells, though its molecular mechanisms are not precisely known. In this study, the molecular mechanisms of apoptosis induced by BV in human breast cancer MCF7 cells were investigated. BV induced morphological changes (examined by phase-contrast microscopy) and inhibited the proliferation (examined by MTT assay) of MCF7 cells; both effects occurred in a dose- and time-dependent manner. Flow cytometric analysis demonstrated that BV induced the production of reactive oxygen species (ROS) and dysfunction of the mitochondrial membrane potential (Azm), and led to cytochrome c release, an increase in the levels of caspase-9 and Poly (ADP-ribose) polymerase (PARP) and then apoptosis. It also showed that BV induced S-phase arrest in MCF7 cells which may occur through the promotion of p53, p21, p27 and the exhibition of Cdk2. Western blotting demonstrated that BV reduced Bcl-2 and increased Bax protein levels which may have caused the changes of delta psi m. BV treatment led to ROS production up to but after treatment led to a decrease in the levels of ROS, which may be associated with the observations of BVaffecting glutathion S-transferase (GST), Zn-superoxide dismutase (Zn-SOD), Cu/Zn-superoxide dismutase (Cu/Zn-SOD) and catalase. The Comet assay also showed that BV induced DNA damage while DAPI staining also confirmed that BV induced apoptosis in examined MCF7 cells. Our results also showed that BV increased the levels of AIF and EndoG in MCF7 cells. In conclusion, our data demonstrated that BV induced apoptosis via a mitochondria-dependent pathway based on the changes of delta psi m, AIF and EndoG release in MCF7 cells.

Curcumin inhibits WEHI-3 leukemia cells in BALB/c mice in vivo.

Curcumin (1, 7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5- dione), a natural polyphenol product of the plant Curcuma longa, exhibited potent inhibitory activities against proliferation, induced cell cycle arrest and exhibited the induction of apoptosis in several tumor cell lines. In our previous studies, we have shown that curcumin induced cell cycle arrest and apoptosis on human leukemia HL-60 and mouse leukemia WEHI-3 cells; there are no reports regarding whether or not it affects leukemia cells in vivo. In the present study, we investigated the effects of curcumin on WEHI-3 in BALB/c mice and the results indicated that curcumin reduces the percentage of Mac-3 marker, which is the precursor of macrophage. Curcumin induced significant effects on the population of B cells from murine leukemia in vivo. We also investigated the weights of spleen and liver from murine leukemia and the results showed that curcumin reduced the weight of the liver and spleen. From the pathological examinations, the effects of curcumin on the liver and spleen from mice after being injected with WEHI-3 cells were apparent. Both organs were enlarged. In conclusion, curcumin affect WEHI-3 cells in vivo.

Effects of luteolin on distribution and metabolism of 2-aminofluorene in male Sprague-Dawley rats.

The effects of oral luteolin on the N-acetylation and metabolism of 2-aminofluorene (AF) in vivo were investigated in bladder, blood, colon, kidney, liver, feces, urine, cerebrum, cerebellum and pineal gland from male Sprague-Dawley rats. Major metabolites such as AAF, 1-OH-AAF, 3-OH-AAF, 8-OH-AAF and 9-OH-AAF were found in bladder tissues; AAF, 1-OH-AAF, 5-OH-AAF and 8-OH-AAF were found in blood samples; AAF, 1-OH-AAF, 3-OH-AAF, 5-OH-AAF, 8-OH-AAF and 9-OH-AAF were found in colon tissues; AAF, 1-OH-AAF, 3-OH-AAF and 9-OH-AAF were found in kidney tissues; AAF, 1-OH-AAF, 3-OH-AAF and 8-OH-AAF were found in liver tissues, AAF, 1-OH-AAF, 3-OH-AAF, 5-OH-AAF, 7-OH-AAF, 8-OH-AA and 9-OH-AAF were found in feces and urine samples; AAF, 1-OH-AAF, 3-OH-AAF and 8-OH-AAF were found in cerebrum tissues; AAF, 1-OH-AAF, 3-OH-AAF and 7-OH-AAF were found in cerebellum tissues; but only AF and AAF were found in pineal gland in rats treated with AF (50 mg/kg) for 24 h. Pretreatment of rats with luteolin (30 mg/kg) 24 h prior to the administration of AF (50 mg/kg) and luteolin given with AF concomitantly led to a decrease in the amounts of 3-OH-AAF and 9-OH-AAF and an increase in the amounts of 1-OH-AAF and 8-OH-AAF in bladder tissues. In blood samples, there were significant decreases of AAF, 1-OH-AAF and 8-OH-AAF after rats were treated with luteolin for 24 h prior to AF but luteolin with AF at the same time caused an increase in 1-OH-AAF. In colon tissues, there were significant decreases of AF, 1-OH-AAF, 3-OH-AAF, 5-OH-AAF and 9-OH-AAF after rats were treated with luteolin for 24 h then AF but the amounts of AF, 1-OH-AAF, 5-OH-AAF and 9-OH-AAF decreased and AAF and 8-OH-AAF increased in rats treated with luteolin and AF at the same time. In kidney tissues, there were significant decreases of AF, AAF and 3-OH-AAF after rats were treated with both compounds at the same time, but luteolin for 24 h then AF treatment led to significant decreases of 3-OH-AAF. In liver samples, after rats were treated with luteolin and AF at the same time, the amounts of AAF and 1-OH-AAF significantly decreased but 8-OH-AAF increased. However, rats treated with luteolin for 24 h then with AF led to significant decreases of AAF, 1-OH-AAF and 3-OH-AAF. In feces samples, there were significant increases of AAF, 3-OH-AAF, 7-OH-AAF, 8-OH-AAF and 9-OH-AAF after rats were treated with both compounds at the same time but luteolin for 24 h then AF treatment led to a significant increase of AF, 1-OH-AAF and 8-OH-AAF and a decrease AAF and 3-OH-AAF. In urine samples, there were significant increases of AF, AAF, 1-OH-AAF, 3-OH-AAF, 5-OH-AAF and 9-OH-AAF but a decrease of 8-OH-AAF after rats were treated with both compounds at the same time. However, the luteolin for 24 h then AF treatment led to significant increases of AF, AAF and 1-OH-AAF but decreases of 3-OH-AAF and 5-OH-AAF. In cerebrum samples, there were significant increases ofAF but decreases of 1-OH-AAF and 8-OH-AAF after rats were treated with both compounds at the same time; luteolin for 24 h then AF treatment of rats led to significant increase of 1-OH-AAF and decreases AF, AAF and 8-OH-AAF. In cerebellum samples, there were significant increases of AAF and decreases of 1-OH-AAF and 3-OH-AAF after rats were treated with both compounds at the same time, there is a significant increase of AAF but decrease of 1-OH-AAF, 3-OH-AAF and 7-OH-AAF after the luteolin treated for 24 h then AF were treated to the rats. In pineal gland samples, there were significant increases ofAAF after rats were treated with both compounds at the same time. However, luteolin treated for 24 h then AF were treated to the rats which increase AAF but decrease AF.

Effects of curcumin on N-bis(2-hydroxypropyl) nitrosamine (DHPN)-induced lung and liver tumorigenesis in BALB/c mice in vivo.

Curcumin (diferuloylmethane), a phenolic compound from the plant Curcuma longa (Linn.) has been shown to exhibit antitumor activity and apoptosis in many human cancer cell lines including that of lung and liver cancer. In this study, curcumin was evaluated in BALB/c mice for its ability to inhibit pulmonary and liver adenoma formation and growth after they were orally treated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). Animals were treated with DHPN in water for approximately 14 days before multiple doses of curcumin were given intraperitoneally. It was found that 200 microM curcumin reduced lung and liver tumor multiplicity by 37% (p<0.05) and 30% (p<0.05) respectively. The results indicated that curcumin significantly inhibited pulmonary and liver adenoma formation and growth in BALB/c mice. The precise mechanism by which curcumin inhibits lung and liver tumorigenesis remains to be elucidated. Thus, curcumin appears to be a promising new chemotherapeutic and preventive agent for lung and liver cancer induced by DHPN.

The role of Ca+2 on rhein-induced apoptosis in human cervical cancer Ca Ski cells.

Apoptosis induced by rhein, an active component of senna, has been reported in various human cancer cells, however, its molecular mechanisms are not precisely known. In this study, the mechanisms of apoptosis by which rhein acts on human cervical cancer Ca Ski cells were examined. Flow cytometric analysis demonstrated that rhein induced the abrogation of mitochondrial membrane potential (MMP) and cleavage of Bid protein. Rhein also induced an increase in the levels of Fas, p53, p21 and Bar, but a decrease in the level of Bcl-2. The activities of both caspase-8 and -9 were enhanced by rhein, promoting caspase-3 activation, leading to DNA fragmentation, thus, indicating that rhein-induced apoptosis is caspase-dependent. In addition, rhein induced an increase in the level of cytoplasmic Ca2+, which was inhibited by BAPTA (a calcium chelator). BAPTA attenuated the MMP abrogation and significantly dinimished the occurrence of rhein-induced apoptosis in Ca Ski cells. In conclusion, our data demonstrate that rhein-induced apoptosis occurs via a caspase-dependent and mitochondria-dependent pathway which is closely related to the level of cytoplasmic Ca2+ in Ca Ski cells.

Sodium ascorbate inhibits growth via the induction of cell cycle arrest and apoptosis in human malignant melanoma A375.S2 cells.

Vitamin C has been reported to be useful in the treatment and prevention of cancer. Inconsistent effects from growth stimulation to induction of apoptosis of malignant tumor cells, however, have been reported. Melanoma is an increasingly common and potentially lethal malignancy. It was reported that melanoma cells were more susceptible to ascorbate toxicity than any other tumor cells. The mechanisms accounting for ascorbate-induced apoptosis in human melanoma cells, however, have remained unclear. This study was undertaken to investigate the effect of sodium ascorbate on cytotoxicity and apoptosis in human malignant melanoma A375.S2 cells. A375.S2 cells were incubated with a certain range of concentrations of sodium ascorbate for various time periods. In order to examine the effects of sodium ascorbate on cell proliferation, cell cycle, apoptosis and necrosis, we performed 4,6-diamidino-2-phenylindole dihydrochloride assays and flow cytometry analysis. Polymerase chain reaction was used to examine the mRNA levels of p53, p21, p27, cyclin A, cyclin E, CDK2 and CDK4, which are associated with cell cycle S-phase arrest and apoptosis. Flow cytometric analysis showed that sodium ascorbate significantly induced cell cycle arrest and apoptosis in the A375.S2 cell line in a dose-dependent manner. The increased expressions of p53 and p21, and the decreased expressions of cyclin A, cyclin E, CDK2 and CDK4, indicated the cell cycle arrest at G1/S phase after the cells had been treated with sodium ascorbate. Induction of apoptosis involved an increase in the levels of p53, p21 and cellular Ca, and a decrease in mitochondrial membrane potential and activation of caspase 3 before culminating in apoptosis in sodium ascorbate-treated A375.S2 cells.

Effect of inhibition of aloe-emodin on N-acetyltransferase activity and gene expression in human malignant melanoma cells (A375.S2).

Arylamine carcinogens and drugs are N-acetylated by cytosolic N-acetyltransferase (NAT), which uses acetyl-coenzyme A as a cofactor. NAT plays an initial role in the metabolism of these arylamine compounds. 2-Aminofluorene is one of the arylamine carcinogens which have been demonstrated to undergo N-acetylation in laboratory animals and humans. Our previous study showed that human cancer cell lines (colon cancer, colo 205; liver cancer, Hep G2; bladder cancer, T24; leukemia, HL-60; prostate cancer, LNCaP; osteogenic sarcoma, U-2 OS; malignant melanoma, A375.S2) displayed NAT activity, which was affected by aloe-emodin in human leukemia cells. The purpose of this study was to determine whether aloe-emodin could affect the enzyme activity and gene expression of NAT at the mRNA and protein levels in malignant human melanoma A375.S2 cells. The results showed that aloe-emodin inhibited NAT1 activity (decreased N-acetylation of 2-aminofluorene) in intact cells in a dose-dependent manner. The effect of aloe-emodin on NAT1 at the protein level was determined by Western blotting and the mRNA levels were examined by polymerase chain reaction (PCR) and cDNA microarray. These results clearly indicate that aloe-emodin inhibits the mRNA expression and enzyme activity of NAT1 in A375.S2 cells.

The inhibition of N-acetyltransferase activity and gene expression in human bladder cancer cells (T24) by shikonin.

Shikonin has the potential to prevent, or be used in the treatment of, bladder transitional cell carcinoma induced by arylamines. We evaluated its effectiveness by measuring the amount of acetylated 2-aminofluorene (AF), AF-DNA adducts, changes of NAT mRNA and the amount of NAT enzyme. T24 human bladder cancer cells were incubated with 30 microM AF with different concentrations of shikonin for various times. T24 cells treated with shikonin (16 microM) were then harvested and used in 2 experiments: 1). T24 cells were incubated with 22.5 microM AF and shikonin (0, 16 microM) (co-treatment) for 6, 12, 18, 24 and 48 h. 2). T24 cells were incubated with various concentrations of AF and shikonin (0, 16 microM) for 24 h. AF and AAF were measured by HPLC. Then in the prepared human T24 cell cytosols different concentrations of AF and shikonin were added to measure the kinetic constants of NAT. Next, AF-DNA adducts in human T24 cells with or without treatment with shikonin were detected and measured. The final two steps included measuring the NAT Ag-Ab complex after treatment with and without shikonin and evaluating the effect of shikonin on the NAT genes. Higher concentrations of shikonin induced decreasing AF acetylation. We found that the longer the culture period, the greater the difference in AF acetylation in the same shikonin concentrations. It was also noted that increase in AAF was proportional to incubation time. In the presence of 16 microM of shikonin, N-acetylation of AF decreased by up to 72-84%. Shikonin decreased the amount of AAF production in human T24 cells in all examined AF doses. Both Km and Vmax values in the cytosolic NAT decreased after the addition of shikonin to the cytosol. Finally, shikonin decreased the amount of AAF production and AF-DNA adducts formation in human 724 cells in all examined AF doses. The percentage of cells stained by antibody was significantly different after treatment with shikonin, especially with the higher shikonin concentrations. The NAT1 mRNA level and the NAT1/beta-actin ratio decreased significantly with higher concentrations (16-24 microM) of shikonin. Shikonin affected NAT activity, gene expression (NAT1 mRNA), AF-DNA adducts formation and formation of NAT Ag-Ab in human bladder tumor T24 cells. Therefore, shikonin should be considered as a candidate agent for the prevention or treatment of transitional cell carcinoma.