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Curcumin, the main chemical part of turmeric, has raised interest because of its activity against inflammation and cancer. These scientists were concerned that curcumin could interfere with anti-cancer drugs. This is because curcumin inhibited two steps in the pathway of these drugs. These steps are, making of reactive oxygen species (ROS) and the c-Jun NH (2)-terminal kinase (JNK) pathway. They are how many cancer drugs start programmed cell death, a process called apoptosis. In their experiments, curcumin inhibited the apoptosis of human breast cancer cells (MCF-7, MDA-MB-231, and BT-4) caused by chemotherapy by up to 70%. They used the anti-cancer drugs; camptothecin-, mechlorethamine-, and doxorubicin. This inhibition was greater when cells were treated with more and longer curcumin. But they saw this inhibition even with short, 3 hours, durations of curcumin. Even the low amount of curcumin, 1 micromole, found in Phase I clinical trials of human, inhibited this apoptosis. In these studies curcumin was an antioxidant. It blocked the activation of JNK and mitochondrial release of cytochrome c in a concentration-dependent manner. They also looked at curcumins effect in mice injected with human breast cancer cells. Curcumin in mouse diets reduced the tumor decreasing effect of the anti-cancer drug, cyclophosphamide. It also blocked the cyclophosamide caused events, activation of apoptosis and JNK. They concluded that curcumin in the diet can interfere with cancer chemotherapy by inhibiting apoptosis. They suggest that additional studies should look at whether curcumin should be avoided by breast cancer patients undergoing chemotherapy.

Dietary curcumin inhibits chemotherapy-induced apo…[Cancer Res. 2002]

Safe compounds that can stop the growth of tumor cells are possible treatments for cancer. Curcumin is the most active part of the spice turmeric (Curcuma longa). It has activity against cancer in animals. In test tube experiments it suppressed steps of gene expression. These were c-jun/Ap-1 and NF-kappaB activation and type 1 human immunodeficiency virus long-terminal repeat-directed gene expression.  These scientists measured the effects of curcumin on the growth of several breast tumor cell lines. These included hormone-dependent and -independent and multidrug-resistant lines. Cell growth was measures by [3H]thymidine incorporation, Trypan blue exclusion, crystal violet dye uptake and flow cytometry. Curcumin inhibited the growth of all the cell lines tested. The effect of curcumin was greater when it was used for longer times and in greater amounts. Curcumin preferentially arrested cells in the G2/S phase of the cell cycle. These are the parts of the cycle when DNA is replicated and the cell is prepared for division. Curcumin-induced cell death was neither due to apoptosis nor to any significant change in the expression of apoptosis-related genes. Apoptosis is a type of programmed, deliberate cell death in which the cell corpses and fragments are safely disposed. Overall these results suggest that curcumin strongly reduces the growth (proliferation) of breast tumor cells and may be a possible anticancer drug.

Antiproliferative effect of curcumin (diferuloylme…[Anticancer Drugs. 1997]

Past studies show that the metabolism (processing) of arachidonic acid (AA) is important in colon (large intestine) cancer. Several enzymes act on AA to produce important signaling molecules such as prostaglandins. These enzymes include tumor phospholipase A2, phospholipase C gamma 1, lipoxygenase, and cyclooxygenase. These scientists looked at the effect of curcumin in the diet on colon cancer in male F344 rats. They tested whether curcumin changed AA metabolism. They intentionally started colon cancer with azoxymethane. Azoxymethane (AOM) is a substance used in cancer research to cause colon tumors in animals. Rats were fed diets of either no curcumin or 2000 parts per million at five weeks of age. This diet was continued for 54 weeks. At seven week of age animals were injected under the skin with AOM once weekly for two weeks. Curcumin resulted in less frequent colon adenocarcinomas (tumors) and fewer invasive, noninvasive, and total adenocarcinomas. Compared with those not given curcumin, those given curcumin had 57% smaller tumor volume. The rats fed curcumin had reduced activity of four AA metabolism enzymes and reduced AA products in their colons and tumors. The steps through which curcumin prevents these chemically caused colon tumors probably includes the metabolism of arachidonic acid.

Chemoprevention of colon carcinogenesis by dietary…[Cancer Res. 1995]

Four natural plant products; turmeric, beta-carotene, catechin, and betel leaf extract were tested for their activity against tumors in two animal models of cancer. The first model was mammary (breast) tumor expressing C3H (Jax) mice. These mice had mammary tumor virus from birth. Researchers gave virgin female C3H mice turmeric in their diet and beta-carotene, catechin, and betel leaf extract in their drinking water. This resulted in less frequent tumors and smaller tumor size. Giving 5% turmeric in the diet from 2 months of age stopped activity of the enzyme, mammary tumor virus-related reverse transcriptase, and early tumor-like changes in the mammary glands. Also, feeding turmeric from 6 months of age resulted in a 100% inhibition of mammary tumors. The second animal model was Wistar rats treated with the cancer-producing chemical 7-12-dimethylbenz(a)anthracene (DMBA). In this model giving the four plant products resulted in less frequent tumors and smaller tumor size. It also delayed the start of mammary tumors.

Chemoprevention of mammary tumor virus-induced an.d..[Breast Cancer Res Treat. 1994]

These scientists looked at the effect of curcumin, the active component of tumeric, on colon (large intestine) cancer of male F344 rats. Azoxymethane is a substance used in cancer research to cause colon tumors in animals. In the this study azoxymethane (AOM) was used to stimulate the cancer pathways, including the ornithine decarboxylase (ODC) and tyrosine protein kinase (TPK). It also increased the arachidonic acid cascade (another cancer pathway) and produced aberrant crypt foci in the colon. These foci  are an early change in the colon leading to cancer. Group of rats were fed diets containing either no curcumin or 2000 parts per million at five weeks of age. Two weeks later all animals were injected under the skin with AOM once weekly for two weeks. Curcumin significantly decreased the levels of ODC and TPK activity, and the formation of numerous arachidonic acid cascade products in the liver and colon. These products included 5(S)-, 8(S)-, 12(S)- and 15(S)-hydroxyeicosatetraenoic acids, thromboxane and prostaglandins. Also, dietary curcumin reduced the formation of these products in the test tube, in liver and colon cells taken from the treated rats. A greater dose of curcumin reduced the products more. Aberrant crypt foci caused by AOM were significantly less in the animals fed curcumin. These findings show that curcumin inhibits precancerous lesions and pathways caused by AOM in the colon of rats.

Inhibition by dietary curcumin of azoxymethane-ind…[Carcinogenesis. 1993]

Tumeric, a yellow spice used in Indian foods, contains a chemical, Curcumin. Curcumin is known to act as an anti-oxidant, anti-mutagen and anti-carcinogen in experimental animals. Anti-oxidants are chemicals that reduce free radicals. Because free radicals cause chain reactions that damage cells, anti-oxidants are thought to help in a number of illnesses. Anti-carcinogens reduce the impact of carcinogens in the start or growth of cancer. Anti-mutagens reduce or inhibit mutagens. Mutagens increased the number of mutations, that is, mistakes in the copying of genetic information, usually DNA. Since mutations can lead to cancer, mutagens can cause cancer. These scientists tested whether turmeric reduced mutagens in 16 long term smokers. Tumeric was giving for 30 days, 1.5 grams per day. After this dose the amount of mutagens in the urine of the smokers was significantly less. In comparison in six untreated non-smokers, there was no change in the amount of mutagens in their urine after 30 days. The scientists did blood tests to see if tumeric had any liver, diabetic, kidney or lipid side effects. Turmeric had no significant effect on the blood tests; serum aspartate aminotransferase and alanine aminotransferase, blood glucose, creatinine and lipid profile. These findings imply that dietary turmeric is an effective anti-mutagen and it may be useful in prevention of cancer.

Effect of turmeric on urinary mutagens in smokers. [Mutagenesis. 1992]