Effect of Stemona curtisii root extract on P-glycoprotein and MRP-1 function in multidrug-resistant cancer cells.

Multidrug resistance (MDR) is the result of overexpression of membrane bound proteins that efflux chemotherapeutic drugs from the cells. Two proteins, P-glycoprotein (P-gp) and multidrug-resistance associated protein-1 (MRP-1) efflux chemotherapeutic agents out of the cancer cell that decrease intracellular drug accumulation, thereby decreasing the effectiveness of many chemotherapeutic agents. In the present study, the ethanolic extract of the roots of Stemona curtisii Hook. was tested for the potential ability to modulate the MDR phenotype and function of P-gp and MRP-1. The S. curtisii extract reversed the resistance to putative chemotherapeutic agents, including vinblastine, paclitaxel and colchicine of KB-V1 cells (MDR human cervical carcinoma with high P-gp expression) in a dose-dependent manner, but not in KB-3-1 cells (drug sensitive human cervical carcinoma, which lack P-gp expression). The root extract also increased the intracellular uptake and retention of (3)[H]-vinblastine in KB-V1 cells dose dependently. The extract did not influence MDR phenotype-mediated MRP-1 in MRP1-HEK293 (human embryonic kidney cells stably transfected with pcDNA3.1-MRP1-H10 which show high MRP-1 expression) and pcDNA3.1-HEK293 (wild type). In summary, the S. curtisii root extract modulated P-gp activity but not MRP-1 activity. The result obtained from this study strongly indicated that S. curtisii extract may play an important role as a P-gp modulator as used in vitro and may be effective in the treatment of multidrug-resistant cancers. The purified form of the active components of S. curtisii extract should be investigated in more details in order to explain the molecular mechanisms involved in P-gp modulation. This is the first report of new biological activity in this plant, which could be a potential source of a new chemosensitizer.

Inhibition of P-glycoprotein function and expression by kaempferol and quercetin.

The 170 kDa plasma membrane P-glycoprotein (Pgp) causes the efflux of chemotherapeutic drugs from cells and is believed to be an important mechanism in multidrug resistance (MDR) in human cancer. This study demonstrates that some putative flavonoids, i.e., flavonols (quercetin and kaempferol) and isoflavones (genistein and daidzein) markedly increase the sensitivity of the multidrug-resistant human cervical carcinoma KB-V1 cells (high Pgp expression) to vinblastine and paclitaxel dose-dependently, and also decrease the relative resistance of these anti-cancer-drugs in KB-V1 cells. None of the flavonoids had a significant effect on vinblastine and paclitaxel cytotoxicity in wildtype drug-sensitive KB-3-1 cells (lacking Pgp). These flavonoids also caused an increase in intracellular accumulation, and reduced the efflux of Rh123 and 3[H]vinblastine in KB-V1 cells, but not in KB-3-1 cells. The flavonols increased the inhibitory effectiveness of Pgp activity in MDR KB-V1 cells more than isoflavones. Only treatment with flavonols up to 48 h was able to significantly decrease the Pgp expression in a dose-dependent manner in KB-V1 cells. These findings provide evidence that flavonols reduced Pgp expression and function resulting in the inhibition of Pgp activity, but isoflavones modulated intracellular drug levels by inhibiting Pgp function with no effect on Pgp expression. Among the flavonoids tested, flavonols, particularly kaempferol, exhibit the most potent MDR reversing property in KB-V1 cells.

Biochemical mechanism of modulation of human P-glycoprotein (ABCB1) by curcumin I, II, and III purified from Turmeric powder.

P-glycoprotein (Pgp, ABCB1) is an ATP-dependent drug efflux pump linked to development of multidrug resistance (MDR) in cancer cells. Previously [Biochem Pharmacol 2002;64:573-82], we reported that a curcumin mixture could modulate both function and expression of Pgp. This study focuses on the effect of three major curcuminoids--curcumin I, II and III purified from a curcumin mixture--on modulation of Pgp function in a multidrug resistant human cervical carcinoma cell line (KB-V1). The similar IC(50) values for cytotoxicity of curcuminoids of KB-V1, and KB-3-1 (parental drug sensitive cell line) suggest that these curcuminoids may not be substrates for Pgp. Treating the cells with non-toxic doses of curcuminoids increased their sensitivity to vinblastine only in the Pgp expressing drug resistant cell line, KB-V1, and curcumin I retained the drug in KB-V1 cells more effectively than curcumin II and III, respectively. Effects of each curcuminoid on rhodamine123, calcein-AM, and bodipy-FL-vinblastine accumulation confirmed these findings. Curcumin I, II and III increased the accumulation of fluorescent substrates in a dose-dependent manner, and at 15 microM, curcumin I was the most effective. The inhibitory effect in a concentration-dependent manner of curcuminoids on verapamil-stimulated ATPase activity and photoaffinity labeling of Pgp with the [(125)I]-iodoarylazidoprazosin offered additional support; curcumin I was the most potent modulator. Taken together, these results indicate that curcumin I is the most effective MDR modulator among curcuminoids, and may be used in combination with conventional chemotherapeutic drugs to reverse MDR in cancer cells.

In-house direct cELISA for determining aflatoxin B1 in Thai corn and peanuts.

To overcome the problem of aflatoxins (AF) in Thai foods, a sensitive in-house direct cELISA using monoclonal antibody (mAb) was established and compared with a commercial ELISA kit and thin-layer chromatography for the determination of AFB(1) levels in corn and peanuts. Among eight in-house mAbs (AF1-8), AF5 was used in the direct cELISA owing to its excellent specificity and sensitivity with the detection limit of 4 microg kg(-1). The recovery of AFB(1) spiked at 5, 10, 20, 40 and 80 microg kg(-1) ranged from 88.1 to 99.5%. Correlation coefficients of the ELISA with the commercial ELISA kit and thin-layer chromatography were 0.912 and 0.802 for corn, and 0.941 and 0.832 for peanuts, respectively (p<0.05). The cost per sample was estimated to be about 16 times lower than the commercial ELISA kit. Subsequently, the in-house direct cELISA was successfully applied to screen the contamination of AFB(1) in Thai corn and peanuts. Mean levels of AFB(1) (per cent positive) were 73 microg kg(-1) (85.7%) in corn and 102 microg kg(-1) (67.9%) in peanuts, for which 46.4% of both foods were above the Thailand regulation limit (20 microg kg(-1)).

Inhibition of carcinogen induced c-Ha-ras and c-fos proto-oncogenes expression by dietary curcumin.

BACKGROUND: We investigated the chemopreventive action of dietary curcumin on 7,12-dimethylbenz(a)anthracene (DMBA)-initiated and 12,0-tetradecanoylphorbol-13-acetate (TPA)-promoted skin tumor formation in Swiss albino mice. Curcumin, a yellow coloring matter isolated from roots of Curcuma longa Linn, is a phenolic compound possessing antioxidant, free radical scavenger, and antiinflammatory properties. It has been shown by previously reported work that TPA-induced skin tumors were inhibited by topical application of curcumin, and curcumin has been shown to inhibit a variety of biological activities of TPA. Topical application of curcumin was reported to inhibit TPA-induced c-fos, c-jun and c-myc gene expression in mouse skin. This paper reports the effects of orally administered curcumin, which was consumed as a dietary component at concentrations of 0.2 % or 1 %, in ad libitum feeding. RESULTS: Animals in which tumors had been initiated with DMBA and promoted with TPA experienced significantly fewer tumors and less tumor volume if they ingested either 0.2% or 1% curcumin diets. Also, the dietary consumption of curcumin resulted in a significantly decreased expression of ras and fos proto-oncogenes in the tumorous skin, as measured by enhanced chemiluminesence Western blotting detection system (Amersham). CONCLUSIONS: Whereas earlier work demonstrated that topical application of curcumin to mouse skin inhibited TPA-induced expression of c-fos, c-jun and c-myc oncogenes, our results are the first to show that orally consumed curcumin significantly inhibited DMBA- and TPA-induced ras and fos gene expression in mouse skin.

Risk factors for lung cancer among Northern Thai women: epidemiological, nutritional, serological, and bacteriological surveys of residents in high- and low-incidence areas.

Lung cancer incidence among Northern Thai women is one of the highest in Asia (an annual age-adjusted incidence rate of 37.4 per 100,000), and the incidence rate significantly differs by geographical districts. Therefore, we conducted a comparative study of women living in the Sarapee area, which showed the highest (crude incidence rate, 40.9), and the Chom Tong area, which had one of the lowest incidence rates (8.5) in Chiang Mai Province, despite the two areas' geographical and cultural closeness. The women in this study were either family members of lung cancer patients or their neighbors. To find clues to the etiology of lung cancer, this study used various epidemiological and biochemical approaches: interviewing on lifestyle factors, duplicate meals, chemical examination of drinking water, biochemical analysis of sera, mutagenicity test of urine, and monitoring of fungi and bacteria in the living environment. We found that tobacco smoking (Khiyo, local cigars) was less frequently observed in Sarapee (high incidence), compared with Chom Tong (low incidence), and that the history of chronic benign respiratory diseases was the most distinct event among women in Sarapee, resulting in a significantly increased percentage of those with a history of both benign respiratory diseases and tobacco smoking. This population revealed increased levels of serum tumor necrosis factor (TNF)-alpha, an endogenous tumor promoter. Furthermore, significantly increased urine mutagenicity was found to be closely associated with history of benign respiratory disease in Sarapee. The fungus which was most commonly found in the air inside houses in Sarapee was identified as Microsporum canis. Additionally, significantly increased serum concentrations of a constituent of the fungus were found in Sarapee women, compared with those in Chom Tong. Our results suggest that tobacco (Khiyo) smoking alone may not be able to explain the very high incidence of female lung cancer in Northern Thailand, and that chronic benign respiratory disease, possibly caused by the infection of fungi such as M. canis, is likely to be involved in the etiology of female lung cancer in North Thailand.

Comparison of diets among elderly female residents in two suburban districts in Chiang Mai Province, Thailand, in dry season--survey on high- and low-risk districts of lung cancer incidence.

By means of duplicate meals, we collected food samples of general female residents, aged 50 to 74 years at two suburban districts in Chiang Mai Province, which are distinguished by very high and low incidence rates of lung cancer. Then, on the basis of analyses of their consumption of foods by food groups, we compared their dietary habits in the dry season of northern Thailand with special reference to the difference in lung cancer incidence. In brief, the following features and difference in their dietary habits were found; 1) Rice, vegetables, and pork were most frequently eaten in both the districts. 2) Consumption of fruits, in both quantity and variety, at a high-risk district was much less than that at a low-risk district. 3) Female residents at a low-risk district consumed more variety of green and yellow vegetables than those at a high-risk district. 4). Potato was not found in food samples of a high-risk district. 5) confectionery was more prevalent in a low-risk district than at a high-risk district.

Inhibitory effect of dietary curcumin on skin carcinogenesis in mice.

Laboratory animal model studies have suggested that curcumin may play an important role in inhibiting the process of carcinogenesis. Curcumin, the yellow pigment that is obtained from rhizomes of the plant Curcuma longa Linn (Family Zingiberaceae), is commonly used as a spice and food coloring agent. The present study was designed to investigate the chemopreventive action of dietary curcumin on 7,12-dimethylbenz[a]anthracene (DMBA)-initiated and 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted skin tumor formation in male Swiss ablino mice. At 6 weeks of age, groups of animals were fed the standard (modified AIN-76 A) diet or a diet containing 1% curcumin. At 8 weeks of age, all animals, except those in the vehicle (acetone)-treated groups, received 100 microg of DMBA dissolved in 100 microl of acetone in a single application to the skin of the back. From 1 week after DMBA application, tumor promoter (2.5 microg of TPA dissolved in 100 microl of acetone) was applied to the same areas on mouse skin twice a week for 26 weeks. All groups continued on their respective dietary regimen until the termination of the experiment. The results indicate that dietary administration of curcumin significantly inhibited the number of tumors per mouse (P < 0.05) and the tumor volume (P < 0.01). The percentage of tumor-bearing mice tended to be lower in the mice on the curcumin diet than those on the standard diet. There was no difference in growth between mice of the standard and 1% curcumin groups. The results indicate the safety and the anti-carcinogenic effect of curcumin in mice.

Suppressive effect of soybean milk protein on experimentally induced skin tumor in mice.

We studied the effect of soybean milk protein (SMP) in a two-stage carcinogenesis experiment on mouse skin. Mice were given soybean protein isolate (SPI) diet or SPI diet supplemented with SMP. After 4 weeks on the diets, the mice were shaved and a tumor initiator was applied. A tumor promotor was then applied twice a week on the same area of the skin throughout the experiment. After 20 weeks on the treatment, the percentage of tumor-bearing mice and the volume of tumor tended to be lower in the mice on the SMP diet than those on the SPI diet. The number of tumor was also significantly lower in the former group as compared to the latter group. There was no difference in growth between mice of the SPI and SMP groups. The results indicate the safety and the anti-carcinogenic effect of SMP in mice.