Summary
  • Indole-3-carbinol (I3C) is derived from the hydrolysis (breakdown) of glucobrassicin, a compound found in cruciferous vegetables. (More information)
  • In the acidic environment of the stomach, I3C molecules can combine with each other to form a number of biologically active acid condensation products, such as 3,3'-diindolylmethane (DIM). (More information)
  • I3C has been found to inhibit the development of cancer in animals when given before or at the same time as a carcinogen. However, in some cases, I3C enhanced the development of cancer in animals when administered after a carcinogen. (More information)
  • The contradictory results of animal studies have led some experts to caution against the widespread use of I3C and DIM supplements for cancer prevention in humans until their potential risks and benefits are better understood. (More information)
  • Although I3C and DIM supplementation have been found to alter urinary estrogen metabolite profiles in women, the effects of I3C and DIM on breast cancer risk are not known. (More information)
  • Results of small preliminary trials in humans suggest that I3C supplementation may help treat conditions related to human papilloma virus (HPV) infection, such as cervical intraepithelial neoplasia (CIN) and recurrent respiratory papillomatosis (RRP). However, randomized controlled trials are needed to determine whether I3C supplementation is beneficial. (More information)
Introduction

Cruciferous vegetables differ from other classes of vegetables in that they are rich sources of sulfur-containing compounds known as glucosinolates (see the article on Cruciferous Vegetables). Because epidemiological studies provide some evidence that diets rich in cruciferous vegetables are associated with lower risk of several types of cancer, scientists are interested in the potential cancer-preventive activities of compounds derived from glucosinolates (1). Among these compounds is indole-3-carbinol (I3C), a compound derived from the enzymatic hydrolysis (breakdown) of an indole glucosinolate, commonly known as glucobrassicin (2).

Metabolism and Bioavailability

A number of commonly consumed cruciferous vegetables, including broccoli, Brussels sprouts, and cabbage, are good sources of glucobrassicin—the glucosinolate precursor of I3C. Myrosinase, an enzyme that catalyzes the hydrolysis of glucosinolates, is physically separated from glucosinolates in intact plant cells (3). When plant cells are damaged, as when cruciferous vegetables are chopped or chewed, the interaction of myrosinase and glucobrassicin results in the formation of I3C (Figure 1). In the acidic environment of the stomach, I3C molecules can combine with each other to form a complex mixture of biologically active compounds, known collectively as acid condensation products (4). Although numerous acid condensation products of I3C have been identified, some of the most prominent include the dimer 3,3'-diindolylmethane (DIM) and a cyclic trimer (CT) (Figure 2). The biological activities of individual acid condensation products differ from those of I3C and are responsible for the biological effects attributed to I3C (5). When plant myrosinase is inactivated (e.g., by boiling), glucosinolate hydrolysis still occurs to a lesser degree, due to the myrosinase activity of human intestinal bacteria (6). Thus, when cruciferous vegetables are cooked in a manner that inactivates myrosinase, glucobrassicin hydrolysis by intestinal bacteria still results in some I3C formation (see Food sources). However, acid condensation products are less likely to form in the more alkaline environment of the intestine.

Figure 1. Formation of Indole-3-Carbinol. The hydrolysis of glucobrassicin by myrosinase at neutral pH results in an unstable indole isothiocyanate (indole-3-methyl isothiocyanate) that degrades to form indole-3-carbinol and a thiocyanate ion.

Figure 2. Chemical structures of some acid condensation products of indole-3-carbinol: 3,3'-Diindolylmethane (DIM) , 5,11-dihydroindolo-[3,2-b]carbazole (ICZ), and 5.6.11.12.17.18-hexahydrocyclononal [1,2-b:4,5-b':7,8-b"]triindole (CT).

Biological Activities

Effects on biotransformation enzymes involved in carcinogen metabolism

Biotransformation enzymes play major roles in the metabolism and elimination of many biologically active compounds, including steroid hormones, carcinogens, toxins, and drugs. In general, phase I biotransformation enzymes, including the cytochrome P450 (CYP) family, catalyze reactions that increase the reactivity of hydrophobic (fat-soluble) compounds, which prepares them for reactions catalyzed by phase II biotransformation enzymes. Reactions catalyzed by phase II enzymes generally increase water solubility and promote the elimination of these compounds (7).

Acid condensation products of I3C, particularly DIM and indole[3,2-b]carbazole (ICZ), can bind to a protein in the cytoplasm of cells called the aryl hydrocarbon receptor (AhR) (5, 8). Binding allows the AhR to enter the nucleus where it forms a complex with the Ahr nuclear translocator (Arnt) protein. This Ahr/Arnt complex binds to specific DNA sequences in genes known as xenobiotic response elements (XRE) and enhances their transcription (9). Genes for a number of CYP enzymes and several phase II enzymes are known to contain XREs. Thus, oral consumption of I3C results in the formation of acid condensation products that can increase the activity of certain phase I and phase II enzymes (8, 10, 11). Increasing the activity of biotransformation enzymes is generally considered a beneficial effect because the elimination of potential carcinogens or toxins is enhanced. However, there is a potential for adverse effects because some procarcinogens require biotransformation by phase I enzymes to become active carcinogens (12).

Alterations in estrogen activity and metabolism

Endogenous estrogens, including 17β-estradiol, exert their estrogenic effects by binding to estrogen receptors (ERs). Within the nucleus, the estrogen-ER complex can bind to DNA sequences in genes known as estrogen response elements (EREs), recruit coactivator molecules, and thus enhance the transcription of estrogen-responsive genes (13). Some ER-mediated effects, such as those that promote cellular proliferation in the breast and uterus, can increase the risk of developing estrogen-sensitive cancers (14).

Effects on estrogen receptor activity

When added to breast cancer cells in culture, I3C has been found to inhibit the transcription of estrogen-responsive genes stimulated by 17β-estradiol (15, 16). Acid condensation products of I3C that bind and activate AhR may also inhibit the transcription of estrogen-responsive genes by competing for coactivators or increasing ER degradation (9, 17). In contrast, some studies in cell culture (18, 19) and animal models (20) have found that acid condensation products of I3C actually enhance the transcription of estrogen-responsive genes. Further research is needed to determine the nature of the stimulatory and inhibitory effects of I3C and its acid condensation products on estrogen-responsive gene transcription under conditions that are relevant to human cancer risk (see Cancer).

Effects on estrogen metabolism

The endogenous estrogen 17β-estradiol can be irreversibly metabolized to 16α-hydroxyestrone (16OHE1) or 2-hydroxyestrone (2OHE1). In contrast to 2OHE1, 16OHE1 is highly estrogenic and has been found to stimulate the proliferation of several estrogen-sensitive cancer cell lines (21, 22). It has been hypothesized that shifting the metabolism of 17β-estradiol toward 2OHE1, and away from 16OHE1, could decrease the risk of estrogen-sensitive cancers, such as breast cancer (23). In controlled clinical trials, oral supplementation with 300-400 mg/day of I3C has consistently increased urinary 2OHE1 levels or urinary 2OHE1:16OHE1 ratios in women (24-29). Supplementation with 108 mg/day of DIM also increased urinary 2OHE1 levels in postmenopausal women (30). However, the relationship between urinary 2OHE1:16OHE1 ratios and breast cancer risk is not clear. Although women with breast cancer had lower urinary ratios of 2OHE1:16OHE1 in several small case-control studies (31-33), larger case-control and prospective cohort studies have not found significant associations between urinary 2OHE1:16OHE1 ratios and breast cancer risk (34-36).

Induction of cell cycle arrest

Once a cell divides, it passes through a sequence of stages—collectively known as the cell cycle—before it divides again. Following DNA damage, the cell cycle can be transiently arrested at damage checkpoints, which allows for DNA repair or activation of pathways leading to cell death (apoptosis) if the damage is irreparable (37). Defective cell cycle regulation may result in the propagation of mutations that contribute to the development of cancer. The addition of I3C to prostate and breast cancer cells in culture has been found to induce cell cycle arrest (38, 39). However, the physiological relevance of these cell culture studies is unclear since little or no I3C is available to tissues after oral administration (see Metabolism and Bioavailability) (40).

Induction of apoptosis

Unlike normal cells, cancerous cells lose their ability to respond to death signals that initiate apoptosis. I3C and DIM have been found to induce apoptosis when added to cultured prostate (38), breast (41- 43), pancreatic (44), and cervical cancer cells (45).

Inhibition of tumor invasion and angiogenesis

Limited evidence in cell culture experiments suggests that I3C and DIM can inhibit the invasion of normal tissue by cancer cells (46) and also inhibit the development of new blood vessels (angiogenesis) required by rapidly growing tumors (47, 48).

Disease Prevention

Cancer

Epidemiological studies

Epidemiological studies provide some support for the hypothesis that higher intakes of cruciferous vegetables are associated with lower risk for some types of cancer (49). However, cruciferous vegetables are relatively good sources of other phytonutrients that may have protective effects against cancer, including vitamin C, folate, selenium, carotenoids, and fiber (see the article on Cruciferous Vegetables). Moreover, cruciferous vegetables provide a variety of glucosinolates, in addition to indole-3-carbinol, that may be hydrolyzed to a variety of potentially protective isothiocyanates (e.g., sulforaphane; see the article on Isothiocyanates) (50). Consequently, evidence for an inverse association between cruciferous vegetable intake and cancer risk provides relatively little information about the specific effects of indole-3-carbinol on cancer risk.

Animal studies

In most animal models, exposure to a chemical carcinogen is required to cause cancer. When administered before or at the same time as the carcinogen, oral I3C has been found to inhibit the development of cancer in a variety of animal models and tissues, including cancers of the mammary gland (breast) (51, 52), uterus (53), stomach (54), colon (55, 56), lung (57), and liver (58, 59). However, a number of studies have found that I3C actually promoted or enhanced the development of cancer when administered chronically after the carcinogen (post-initiation). The cancer-promoting effects of I3C were first reported in a trout model of liver cancer (60, 61). However, I3C has also been found to promote cancer of the liver (62-64), thyroid (64), colon (65, 66), and uterus (67) in rats. More recently, inclusion of I3C in the maternal diet was found to protect the offspring from lymphoma and lung tumors induced by dibenzo[a,l]pyrene, a polycyclic aromatic hydrocarbon (68). Polycyclic aromatic hydrocarbons are chemical pollutants formed during incomplete combustion of organic substances, such as coal, oil, wood, and tobacco (69). Although the long-term effects of I3C supplementation on cancer risk in humans are not known, the contradictory results of animal studies have led several experts to caution against the widespread use of I3C and DIM supplements in humans until their potential risks and benefits are better understood (62, 70, 71).

Disease Treatment

Diseases related to human papilloma virus infection

Cervical intraepithelial neoplasia

Infection with certain strains of human papilloma virus (HPV) is an important risk factor for cervical cancer (72). Transgenic mice that express cancer-promoting HPV genes develop cervical cancer with chronic 17β-estradiol administration. In this model, feeding I3C markedly reduced the number of mice that developed cervical cancer (73). A small placebo-controlled trial in women examined the effect of oral I3C supplementation on the progression of precancerous cervical lesions classified as cervical intraepithelial neoplasia (CIN) 2 or CIN 3 (74). After 12 weeks, four out of the eight women who took 200 mg/day had complete regression of CIN and four out of the nine who took 400 mg/day had complete regression, while none of the ten who took a placebo had complete regression. HPV was present in seven out of the ten women in the placebo group, seven out of eight women in the 200 mg I3C group, and eight out of nine women in the 400 mg I3C group (74). Although these preliminary results are encouraging, larger controlled clinical trials are needed to determine the efficacy of I3C supplementation for preventing the progression of precancerous lesions of the cervix (75).

Vulvar intraepithelial neoplasia

HPV infection can also lead to vulvar intraepithelial neoplasia (VIN) (76). A small randomized trial in 12 women with VIN found that supplementation with 200 mg/day or 400 mg/day of I3C for six months improved overall symptoms and decreased lesion size and degree of aggressive histopathology (77). While the results of this preliminary trial are promising, more clinical trials are needed to determine whether I3C might be an effective treatment for VIN.

Recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is a rare disease of children and adults, which are characterized by generally benign growths (papillomas) in the respiratory tract caused by HPV infection (78). These papillomas occur most commonly on or around the vocal cords in the larynx (voice box), but they may also affect the trachea, bronchi, and lungs. The most common treatment for RRP is surgical removal of the papillomas. Since papillomas often recur, adjunct treatments may be used to help prevent or reduce recurrences (79). In immune-compromised mice transplanted with HPV-infected laryngeal tissue, only 25% of the mice fed I3C developed laryngeal papillomas compared to 100% of the control mice (80). In a small observational study of RRP patients, increased ratios of urinary 2OHE1:16OHE1 ratios resulting from increased cruciferous vegetable consumption were associated with less severe RRP (81). Most recently, an uncontrolled pilot study examined the effect of I3C supplementation (400 mg/day for adults and 10 mg/kg daily for children) on papilloma recurrence in RRP patients (82). Over a 5-year follow-up period, 11 of the original 49 patients experienced no recurrence, ten experienced a reduction in the rate of recurrence, 12 experienced no improvement, and 12 were lost to follow-up (83). Although the low toxicity of I3C makes it an attractive adjunct therapy for RRP, controlled clinical trials are needed to determine whether I3C is effective in preventing or reducing the recurrence of respiratory papillomas.

Systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by chronic inflammation that may result in damage to the joints, skin, kidneys, heart, lungs, blood vessels, or brain (84). Estrogen is thought to play a role in the pathology of SLE because the disorder is much more common in women than men, and its onset is most common during the reproductive years when endogenous estrogen levels are highest (85). The potential for I3C supplementation to shift endogenous estrogen metabolism toward the less estrogenic metabolite 2OHE1, and away from the highly estrogenic metabolite 16OHE1 (see Estrogen metabolism), led to interest in its use in SLE (24). In an animal model of SLE, I3C feeding decreased the severity of renal (kidney) disease and prolonged survival (86). A small uncontrolled trial of I3C supplementation (375 mg/day) in female SLE patients found that I3C increased urinary 2OHE1:16OHE1 ratios, but the trial found no significant change in SLE symptoms after three months (86). Controlled clinical trials are needed to determine whether I3C supplementation will have beneficial effects in SLE patients.

Sources

Food sources

Glucobrassicin, the glucosinolate precursor of I3C, is found in a number of cruciferous vegetables, including broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, kale, kohlrabi, mustard greens, radish, rutabaga, and turnip (87, 88). Although glucosinolates are present in relatively high concentrations in cruciferous vegetables, glucobrassicin makes up only about 8%-12% of the total glucosinolates (89). Total glucosinolate contents of selected cruciferous vegetables are presented in Table 1 (90). The amount of indole-3-carbinol formed from glucobrassicin in foods is variable and depends, in part, on the processing and preparation of foods.

Effects of cooking

Glucosinolates are water-soluble compounds that may be leached into cooking water. Boiling cruciferous vegetables from 9-15 minutes resulted in 18%-59% decreases in the total glucosinolate content of cruciferous vegetables (90). Cooking methods that use less water, such as steaming or microwaving, may reduce glucosinolate losses. Some cooking practices, including boiling (91), steaming (92), and microwaving at high power (850-900 watts) (93, 94), may inactivate myrosinase, the enzyme that catalyzes glucosinolate hydrolysis. Even in the absence of plant myrosinase activity, the myrosinase activity of human intestinal bacteria results in some glucosinolate hydrolysis (6). However, studies in humans have found that inactivation of myrosinase in cruciferous vegetables substantially decreases the bioavailability of glucosinolate hydrolysis products known as isothiocyanates (91-93). Since the formation of I3C also depends on glucosinolate hydrolysis, it is very likely that the bioavailability of I3C and its acid condensation products would also be decreased by myrosinase inactivation.

Table 1. Glucosinolate Content of Selected Cruciferous Vegetables (90)
Food (raw) Serving Total Glucosinolates
(mg/g of food)
Garden cress ½ cup (25 g)
3.9
Mustard greens ½ cup, chopped (28 g)
2.8
Brussels sprouts ½ cup (44 g)
2.4
Horseradish 1 tablespoon (15 g)
1.6
Kale 1 cup, chopped (67 g)
1.0
Watercress 1 cup, chopped (34 g)
0.9
Turnip ½ cup, cubes (65 g)
0.9
Cabbage, savoy ½ cup, chopped (45 g)
0.8
Cabbage, red ½ cup, chopped (45 g)
0.6
Broccoli ½ cup, chopped (44 g)
0.6
Kohlrabi ½ cup, chopped (67 g)
0.5
Bok choi (pak choi) ½ cup, chopped (35 g)
0.5
Cauliflower ½ cup, chopped (50 g)
0.4

Supplements

Indole-3-Carbinol (I3C)

I3C is available without a prescription as a dietary supplement. I3C supplementation increased urinary 2OHE1 levels in adults at doses of 300-400 mg/day (28). I3C doses of 200 mg/day or 400 mg/day improved the regression of cervical intraepithelial neoplasia (CIN) in a preliminary clinical trial (74). I3C in doses up to 400 mg/day has been used to treat recurrent respiratory papillomatosis (82, 83). These supplemental levels are well above levels dietary levels, which commonly range from 20-120 mg daily (95).

3,3'-Diindolylmethane (DIM)

DIM is available without a prescription as a dietary supplement. In a small clinical trial, DIM supplementation at a dose of 108 mg/day for 30 days increased urinary 2OHE1 excretion in postmenopausal women with a history of breast cancer (30).

Safety

Adverse effects

Slight increases in the serum concentrations of a liver enzyme (alanine aminotransferase; ALT) were observed in two women who took unspecified doses of I3C supplements for four weeks (28). One person reported a skin rash while taking 375 mg/day of I3C (24). High doses of I3C (800 mg/day) were associated with symptoms of disequilibrium and tremor, which resolved when the dose was decreased (82). I3C supplementation enhanced the development of cancer in some animal models when given after the carcinogen (62, 64, 65, 67) (see Cancer). The effects of I3C or DIM supplementation on cancer risk in humans are not known.

Pregnancy and lactation

The safety of I3C or DIM supplements during pregnancy or lactation has not been established.

Drug interactions

No drug interactions in humans have been reported. However, preliminary evidence that I3C and DIM can increase the activity of CYP1A2 (96, 97) suggests the potential for I3C or DIM supplementation to decrease serum concentrations of medications metabolized by CYP1A2. Both I3C and DIM modestly increase the activity of CYP3A4 in rats when administered chronically (98). This observation raises the potential for adverse drug interactions in humans since CYP3A4 is involved in the metabolism of approximately 50% of therapeutic drugs.

Authors and Reviewers

Originally written in 2005 by:
Jane Higdon, Ph.D.
Linus Pauling Institute
Oregon State University

Updated in December 2008 by:
Victoria J. Drake, Ph.D.
Linus Pauling Institute
Oregon State University

Reviewed in December 2008 by:
David E. Williams, Ph.D.
Principal Investigator, Linus Pauling Institute
Professor, Department of Environmental and Molecular Toxicology
Oregon State University

Copyright 2005-2015  Linus Pauling Institute 

References

1.  Verhoeven DT, Verhagen H, Goldbohm RA, van den Brandt PA, van Poppel G. A review of mechanisms underlying anticarcinogenicity by brassica vegetables. Chem Biol Interact. 1997;103(2):79-129.  (PubMed)

2.  Kim YS, Milner JA. Targets for indole-3-carbinol in cancer prevention. J Nutr Biochem. 2005;16(2):65-73.  (PubMed)

3.  Holst B, Williamson G. A critical review of the bioavailability of glucosinolates and related compounds. Nat Prod Rep. 2004;21(3):425-447.  (PubMed)

4.  Shertzer HG, Senft AP. The micronutrient indole-3-carbinol: implications for disease and chemoprevention. Drug Metabol Drug Interact. 2000;17(1-4):159-188.  (PubMed)

5.  Bjeldanes LF, Kim JY, Grose KR, Bartholomew JC, Bradfield CA. Aromatic hydrocarbon responsiveness-receptor agonists generated from indole-3-carbinol in vitro and in vivo: comparisons with 2,3,7,8-tetrachlorodibenzo-p-dioxin. Proc Natl Acad Sci U S A. 1991;88(21):9543-9547.  (PubMed)

6.  Shapiro TA, Fahey JW, Wade KL, Stephenson KK, Talalay P. Human metabolism and excretion of cancer chemoprotective glucosinolates and isothiocyanates of cruciferous vegetables. Cancer Epidemiol Biomarkers Prev. 1998;7(12):1091-1100.  (PubMed)

7.  Lampe JW, Peterson S. Brassica, biotransformation and cancer risk: genetic polymorphisms alter the preventive effects of cruciferous vegetables. J Nutr. 2002;132(10):2991-2994.  (PubMed)

8.  Bonnesen C, Eggleston IM, Hayes JD. Dietary indoles and isothiocyanates that are generated from cruciferous vegetables can both stimulate apoptosis and confer protection against DNA damage in human colon cell lines. Cancer Res. 2001;61(16):6120-6130.  (PubMed)

9.  Safe S. Molecular biology of the Ah receptor and its role in carcinogenesis. Toxicol Lett. 2001;120(1-3):1-7.  (PubMed)

10.  Nho CW, Jeffery E. The synergistic upregulation of phase II detoxification enzymes by glucosinolate breakdown products in cruciferous vegetables. Toxicol Appl Pharmacol. 2001;174(2):146-152.  (PubMed)

11.  Wallig MA, Kingston S, Staack R, Jefferey EH. Induction of rat pancreatic glutathione S-transferase and quinone reductase activities by a mixture of glucosinolate breakdown derivatives found in Brussels sprouts. Food Chem Toxicol. 1998;36(5):365-373.  (PubMed)

12.  Baird WM, Hooven LA, Mahadevan B. Carcinogenic polycyclic aromatic hydrocarbon-DNA adducts and mechanism of action. Environ Mol Mutagen. 2005;45(2-3):106-114.  (PubMed)

13.  Jordan VC, Gapstur S, Morrow M. Selective estrogen receptor modulation and reduction in risk of breast cancer, osteoporosis, and coronary heart disease. J Natl Cancer Inst. 2001;93(19):1449-1457.  (PubMed)

14.  Liehr JG. Is estradiol a genotoxic mutagenic carcinogen? Endocr Rev. 2000;21(1):40-54.  (PubMed)

15.  Ashok BT, Chen Y, Liu X, Bradlow HL, Mittelman A, Tiwari RK. Abrogation of estrogen-mediated cellular and biochemical effects by indole-3-carbinol. Nutr Cancer. 2001;41(1-2):180-187.  (PubMed)

16.  Meng Q, Yuan F, Goldberg ID, Rosen EM, Auborn K, Fan S. Indole-3-carbinol is a negative regulator of estrogen receptor-alpha signaling in human tumor cells. J Nutr. 2000;130(12):2927-2931.  (PubMed)

17.  Chen I, McDougal A, Wang F, Safe S. Aryl hydrocarbon receptor-mediated antiestrogenic and antitumorigenic activity of diindolylmethane. Carcinogenesis. 1998;19(9):1631-1639.  (PubMed)

18.  Leong H, Riby JE, Firestone GL, Bjeldanes LF. Potent ligand-independent estrogen receptor activation by 3,3'-diindolylmethane is mediated by cross talk between the protein kinase A and mitogen-activated protein kinase signaling pathways. Mol Endocrinol. 2004;18(2):291-302.  (PubMed)

19.  Riby JE, Feng C, Chang YC, Schaldach CM, Firestone GL, Bjeldanes LF. The major cyclic trimeric product of indole-3-carbinol is a strong agonist of the estrogen receptor signaling pathway. Biochemistry. 2000;39(5):910-918.  (PubMed)

20.  Shilling AD, Carlson DB, Katchamart S, Williams DE. 3,3'-Diindolylmethane, a major condensation product of indole-3-carbinol, is a potent estrogen in the rainbow trout. Toxicol Appl Pharmacol. 2001;170(3):191-200.  (PubMed)

21.  Telang NT, Suto A, Wong GY, Osborne MP, Bradlow HL. Induction by estrogen metabolite 16 alpha-hydroxyestrone of genotoxic damage and aberrant proliferation in mouse mammary epithelial cells. J Natl Cancer Inst. 1992;84(8):634-638.  (PubMed)

22.  Yuan F, Chen DZ, Liu K, Sepkovic DW, Bradlow HL, Auborn K. Anti-estrogenic activities of indole-3-carbinol in cervical cells: implication for prevention of cervical cancer. Anticancer Res. 1999;19(3A):1673-1680.  (PubMed)

23.  Bradlow HL, Telang NT, Sepkovic DW, Osborne MP. 2-Hydroxyestrone: the 'good' estrogen. J Endocrinol. 1996;150 Suppl:S259-265.  (PubMed)

24.  McAlindon TE, Gulin J, Chen T, Klug T, Lahita R, Nuite M. Indole-3-carbinol in women with SLE: effect on estrogen metabolism and disease activity. Lupus. 2001;10(11):779-783.  (PubMed)

25.  Bradlow HL, Michnovicz JJ, Halper M, Miller DG, Wong GY, Osborne MP. Long-term responses of women to indole-3-carbinol or a high fiber diet. Cancer Epidemiol Biomarkers Prev. 1994;3(7):591-595.  (PubMed)

26.  Michnovicz JJ. Increased estrogen 2-hydroxylation in obese women using oral indole-3-carbinol. Int J Obes Relat Metab Disord. 1998;22(3):227-229.  (PubMed)

27.  Michnovicz JJ, Adlercreutz H, Bradlow HL. Changes in levels of urinary estrogen metabolites after oral indole-3-carbinol treatment in humans. J Natl Cancer Inst. 1997;89(10):718-723.  (PubMed)

28.  Wong GY, Bradlow L, Sepkovic D, Mehl S, Mailman J, Osborne MP. Dose-ranging study of indole-3-carbinol for breast cancer prevention. J Cell Biochem Suppl. 1997;28-29:111-116.  (PubMed)

29.  Reed GA, Peterson KS, Smith HJ, et al. A phase I study of indole-3-carbinol in women: tolerability and effects. Cancer Epidemiol Biomarkers Prev. 2005;14(8):1953-1960.  (PubMed)

30.  Dalessandri KM, Firestone GL, Fitch MD, Bradlow HL, Bjeldanes LF. Pilot study: effect of 3,3'-diindolylmethane supplements on urinary hormone metabolites in postmenopausal women with a history of early-stage breast cancer. Nutr Cancer. 2004;50(2):161-167.  (PubMed)

31.  Ho GH, Luo XW, Ji CY, Foo SC, Ng EH. Urinary 2/16 alpha-hydroxyestrone ratio: correlation with serum insulin-like growth factor binding protein-3 and a potential biomarker of breast cancer risk. Ann Acad Med Singapore. 1998;27(2):294-299.  (PubMed)

32.  Kabat GC, Chang CJ, Sparano JA, et al. Urinary estrogen metabolites and breast cancer: a case-control study. Cancer Epidemiol Biomarkers Prev. 1997;6(7):505-509.  (PubMed)

33.  Schneider J, Kinne D, Fracchia A, et al. Abnormal oxidative metabolism of estradiol in women with breast cancer. Proc Natl Acad Sci U S A. 1982;79(9):3047-3051.  (PubMed)

34.  Cauley JA, Zmuda JM, Danielson ME, et al. Estrogen metabolites and the risk of breast cancer in older women. Epidemiology. 2003;14(6):740-744.  (PubMed)

35.  Meilahn EN, De Stavola B, Allen DS, et al. Do urinary oestrogen metabolites predict breast cancer? Guernsey III cohort follow-up. Br J Cancer. 1998;78(9):1250-1255.  (PubMed)

36.  Ursin G, London S, Stanczyk FZ, et al. Urinary 2-hydroxyestrone/16alpha-hydroxyestrone ratio and risk of breast cancer in postmenopausal women. J Natl Cancer Inst. 1999;91(12):1067-1072.  (PubMed)

37.  Stewart ZA, Westfall MD, Pietenpol JA. Cell-cycle dysregulation and anticancer therapy. Trends Pharmacol Sci. 2003;24(3):139-145.  (PubMed)

38.  Chinni SR, Li Y, Upadhyay S, Koppolu PK, Sarkar FH. Indole-3-carbinol (I3C) induced cell growth inhibition, G1 cell cycle arrest and apoptosis in prostate cancer cells. Oncogene. 2001;20(23):2927-2936.  (PubMed)

39.  Cover CM, Hsieh SJ, Tran SH, et al. Indole-3-carbinol inhibits the expression of cyclin-dependent kinase-6 and induces a G1 cell cycle arrest of human breast cancer cells independent of estrogen receptor signaling. J Biol Chem. 1998;273(7):3838-3847.  (PubMed)

40.  Stresser DM, Williams DE, Griffin DA, Bailey GS. Mechanisms of tumor modulation by indole-3-carbinol. Disposition and excretion in male Fischer 344 rats. Drug Metab Dispos. 1995;23(9):965-975.  (PubMed)

41.  Hong C, Firestone GL, Bjeldanes LF. Bcl-2 family-mediated apoptotic effects of 3,3'-diindolylmethane (DIM) in human breast cancer cells. Biochem Pharmacol. 2002;63(6):1085-1097.  (PubMed)

42.  Howells LM, Gallacher-Horley B, Houghton CE, Manson MM, Hudson EA. Indole-3-carbinol inhibits protein kinase B/Akt and induces apoptosis in the human breast tumor cell line MDA MB468 but not in the nontumorigenic HBL100 line. Mol Cancer Ther. 2002;1(13):1161-1172.  (PubMed)

43.  Rahman KW, Sarkar FH. Inhibition of nuclear translocation of nuclear factor-{kappa}B contributes to 3,3'-diindolylmethane-induced apoptosis in breast cancer cells. Cancer Res. 2005;65(1):364-371.  (PubMed)

44.  Abdelrahim M, Newman K, Vanderlaag K, Samudio I, Safe S. 3,3'-diindolylmethane (DIM) and its derivatives induce apoptosis in pancreatic cancer cells through endoplasmic reticulum stress-dependent upregulation of DR5. Carcinogenesis. 2006;27(4):717-728.  (PubMed)

45.  Chen D, Carter TH, Auborn KJ. Apoptosis in cervical cancer cells: implications for adjunct anti-estrogen therapy for cervical cancer. Anticancer Res. 2004;24(5A):2649-2656.  (PubMed)

46.  Meng Q, Goldberg ID, Rosen EM, Fan S. Inhibitory effects of Indole-3-carbinol on invasion and migration in human breast cancer cells. Breast Cancer Res Treat. 2000;63(2):147-152.  (PubMed)

47.  Chang X, Tou JC, Hong C, et al. 3,3'-Diindolylmethane inhibits angiogenesis and the growth of transplantable human breast carcinoma in athymic mice. Carcinogenesis. 2005;26(4):771-778.  (PubMed)

48.  Wu HT, Lin SH, Chen YH. Inhibition of cell proliferation and in vitro markers of angiogenesis by indole-3-carbinol, a major indole metabolite present in cruciferous vegetables. J Agric Food Chem. 2005;53(13):5164-5169.  (PubMed)

49.  Verhoeven DT, Goldbohm RA, van Poppel G, Verhagen H, van den Brandt PA. Epidemiological studies on brassica vegetables and cancer risk. Cancer Epidemiol Biomarkers Prev. 1996;5(9):733-748.  (PubMed)

50.  Fahey JW, Zalcmann AT, Talalay P. The chemical diversity and distribution of glucosinolates and isothiocyanates among plants. Phytochemistry. 2001;56(1):5-51.  (PubMed)

51.  Grubbs CJ, Steele VE, Casebolt T, et al. Chemoprevention of chemically-induced mammary carcinogenesis by indole-3-carbinol. Anticancer Res. 1995;15(3):709-716.  (PubMed)

52.  Bradlow HL, Michnovicz J, Telang NT, Osborne MP. Effects of dietary indole-3-carbinol on estradiol metabolism and spontaneous mammary tumors in mice. Carcinogenesis. 1991;12(9):1571-1574.  (PubMed)

53.  Kojima T, Tanaka T, Mori H. Chemoprevention of spontaneous endometrial cancer in female Donryu rats by dietary indole-3-carbinol. Cancer Res. 1994;54(6):1446-1449.  (PubMed)

54.  Wattenberg LW, Loub WD. Inhibition of polycyclic aromatic hydrocarbon-induced neoplasia by naturally occurring indoles. Cancer Res. 1978;38(5):1410-1413.  (PubMed)

55.  Wargovich MJ, Chen CD, Jimenez A, et al. Aberrant crypts as a biomarker for colon cancer: evaluation of potential chemopreventive agents in the rat. Cancer Epidemiol Biomarkers Prev. 1996;5(5):355-360.  (PubMed)

56.  Guo D, Schut HA, Davis CD, Snyderwine EG, Bailey GS, Dashwood RH. Protection by chlorophyllin and indole-3-carbinol against 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced DNA adducts and colonic aberrant crypts in the F344 rat. Carcinogenesis. 1995;16(12):2931-2937.  (PubMed)

57.  Morse MA, LaGreca SD, Amin SG, Chung FL. Effects of indole-3-carbinol on lung tumorigenesis and DNA methylation induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and on the metabolism and disposition of NNK in A/J mice. Cancer Res. 1990;50(9):2613-2617.  (PubMed)

58.  Dashwood RH, Arbogast DN, Fong AT, Hendricks JD, Bailey GS. Mechanisms of anti-carcinogenesis by indole-3-carbinol: detailed in vivo DNA binding dose-response studies after dietary administration with aflatoxin B1. Carcinogenesis. 1988;9(3):427-432.  (PubMed)

59.  Oganesian A, Hendricks JD, Williams DE. Long term dietary indole-3-carbinol inhibits diethylnitrosamine-initiated hepatocarcinogenesis in the infant mouse model. Cancer Lett. 1997;118(1):87-94.  (PubMed)

60.  Dashwood RH, Fong AT, Williams DE, Hendricks JD, Bailey GS. Promotion of aflatoxin B1 carcinogenesis by the natural tumor modulator indole-3-carbinol: influence of dose, duration, and intermittent exposure on indole-3-carbinol promotional potency. Cancer Res. 1991;51(9):2362-2365.  (PubMed)

61.  Oganesian A, Hendricks JD, Pereira CB, Orner GA, Bailey GS, Williams DE. Potency of dietary indole-3-carbinol as a promoter of aflatoxin B1-initiated hepatocarcinogenesis: results from a 9000 animal tumor study. Carcinogenesis. 1999;20(3):453-458.  (PubMed)

62.  Stoner G, Casto B, Ralston S, Roebuck B, Pereira C, Bailey G. Development of a multi-organ rat model for evaluating chemopreventive agents: efficacy of indole-3-carbinol. Carcinogenesis. 2002;23(2):265-272.  (PubMed)

63.  Kim DJ, Lee KK, Han BS, Ahn B, Bae JH, Jang JJ. Biphasic modifying effect of indole-3-carbinol on diethylnitrosamine-induced preneoplastic glutathione S-transferase placental form-positive liver cell foci in Sprague-Dawley rats. Jpn J Cancer Res. 1994;85(6):578-583.  (PubMed)

64.  Kim DJ, Han BS, Ahn B, et al. Enhancement by indole-3-carbinol of liver and thyroid gland neoplastic development in a rat medium-term multiorgan carcinogenesis model. Carcinogenesis. 1997;18(2):377-381.  (PubMed)

65.  Pence BC, Buddingh F, Yang SP. Multiple dietary factors in the enhancement of dimethylhydrazine carcinogenesis: main effect of indole-3-carbinol. J Natl Cancer Inst. 1986;77(1):269-276.  (PubMed)

66.  Suzui M, Inamine M, Kaneshiro T, et al. Indole-3-carbinol inhibits the growth of human colon carcinoma cells but enhances the tumor multiplicity and volume of azoxymethane-induced rat colon carcinogenesis. Int J Oncol. 2005;27(5):1391-1399.  (PubMed)

67.  Yoshida M, Katashima S, Ando J, et al. Dietary indole-3-carbinol promotes endometrial adenocarcinoma development in rats initiated with N-ethyl-N'-nitro-N-nitrosoguanidine, with induction of cytochrome P450s in the liver and consequent modulation of estrogen metabolism. Carcinogenesis. 2004;25(11):2257-2264.  (PubMed)

68.  Yu Z, Mahadevan B, Lohr CV, et al. Indole-3-carbinol in the maternal diet provides chemoprotection for the fetus against transplacental carcinogenesis by the polycyclic aromatic hydrocarbon dibenzo[a,l]pyrene. Carcinogenesis. 2006;27(10):2116-2123.  (PubMed)

69.  ATSDR. Toxicological Profile for Polycyclic Aromatic Hydrocarbons (PAHs). Agency for Toxic Substances and Disease Registry, US Department of Health and Human Services. Atlanta, GA. August 1995.

70.  Dashwood RH. Indole-3-carbinol: anticarcinogen or tumor promoter in brassica vegetables? Chem Biol Interact. 1998;110(1-2):1-5.  (PubMed)

71.  Lee BM, Park KK. Beneficial and adverse effects of chemopreventive agents. Mutat Res. 2003;523-524:265-278.  (PubMed)

72.  Bosch FX, de Sanjose S. Chapter 1: Human papillomavirus and cervical cancer—burden and assessment of causality. J Natl Cancer Inst Monogr. 2003(31):3-13.  (PubMed)

73.  Jin L, Qi M, Chen DZ, et al. Indole-3-carbinol prevents cervical cancer in human papilloma virus type 16 (HPV16) transgenic mice. Cancer Res. 1999;59(16):3991-3997.  (PubMed)

74.  Bell MC, Crowley-Nowick P, Bradlow HL, et al. Placebo-controlled trial of indole-3-carbinol in the treatment of CIN. Gynecol Oncol. 2000;78(2):123-129.  (PubMed)

75.  Stanley M. Chapter 17: Genital human papillomavirus infections--current and prospective therapies. J Natl Cancer Inst Monogr. 2003(31):117-124.  (PubMed)

76.  Hording U, Junge J, Poulsen H, Lundvall F. Vulvar intraepithelial neoplasia III: a viral disease of undetermined progressive potential. Gynecol Oncol. 1995;56(2):276-279.  (PubMed)

77.  Naik R, Nixon S, Lopes A, Godfrey K, Hatem MH, Monaghan JM. A randomized phase II trial of indole-3-carbinol in the treatment of vulvar intraepithelial neoplasia. Int J Gynecol Cancer. 2006;16(2):786-790.  (PubMed)

78.  What is recurrent respiratory papillomatosis? Recurrent Respiratory Papillomatosis Foundation [Web page]. Available at: http://rrpf.org/whatisRRP.html. Accessed January 31, 2005.

79.  Auborn KJ. Therapy for recurrent respiratory papillomatosis. Antivir Ther. 2002;7(1):1-9.  (PubMed)

80.  Newfield L, Goldsmith A, Bradlow HL, Auborn K. Estrogen metabolism and human papillomavirus-induced tumors of the larynx: chemo-prophylaxis with indole-3-carbinol. Anticancer Res. 1993;13(2):337-341.  (PubMed)

81.  Auborn K, Abramson A, Bradlow HL, Sepkovic D, Mullooly V. Estrogen metabolism and laryngeal papillomatosis: a pilot study on dietary prevention. Anticancer Res. 1998;18(6B):4569-4573.  (PubMed)

82.  Rosen CA, Woodson GE, Thompson JW, Hengesteg AP, Bradlow HL. Preliminary results of the use of indole-3-carbinol for recurrent respiratory papillomatosis. Otolaryngol Head Neck Surg. 1998;118(6):810-815.  (PubMed)

83.  Rosen CA, Bryson PC. Indole-3-carbinol for recurrent respiratory papillomatosis: long-term results. J Voice. 2004;18(2):248-253.  (PubMed)

84.  Nass T. Lupus: A Patient Care Guide for Nurses and Other Health Professionals. National Institute of Arthritis and Musculoskeletal and Skin Diseases [Web page]. May 2001. Available at: http://www.niams.nih.gov/hi/topics/lupus/lupusguide/outline.htm. Accessed February 8, 2005.

85.  McMurray RW, May W. Sex hormones and systemic lupus erythematosus: review and meta-analysis. Arthritis Rheum. 2003;48(8):2100-2110.  (PubMed)

86.  Auborn KJ, Qi M, Yan XJ, et al. Lifespan is prolonged in autoimmune-prone (NZB/NZW) F1 mice fed a diet supplemented with indole-3-carbinol. J Nutr. 2003;133(11):3610-3613.  (PubMed)

87.  Carlson DG, Kwolek WF, Williams PH. Glucosinolates in crucifer vegetables: broccoli, Brussels sprouts, cauliflower, collards, kale, mustard greens, and kohlrabi. J Amer Soc Hort Sci. 1987;112(1):173-178.

88.  Fenwick GR, Heaney RK, Mullin WJ. Glucosinolates and their breakdown products in food and food plants. Crit Rev Food Sci Nutr. 1983;18(2):123-201.  (PubMed)

89.  Kushad MM, Brown AF, Kurilich AC, et al. Variation of glucosinolates in vegetable crops of Brassica oleracea. J Agric Food Chem. 1999;47(4):1541-1548.  (PubMed)

90.  McNaughton SA, Marks GC. Development of a food composition database for the estimation of dietary intakes of glucosinolates, the biologically active constituents of cruciferous vegetables. Br J Nutr. 2003;90(3):687-697.  (PubMed)

91.  Shapiro TA, Fahey JW, Wade KL, Stephenson KK, Talalay P. Chemoprotective glucosinolates and isothiocyanates of broccoli sprouts: metabolism and excretion in humans. Cancer Epidemiol Biomarkers Prev. 2001;10(5):501-508.  (PubMed)

92.  Conaway CC, Getahun SM, Liebes LL, et al. Disposition of glucosinolates and sulforaphane in humans after ingestion of steamed and fresh broccoli. Nutr Cancer. 2000;38(2):168-178.  (PubMed)

93.  Rouzaud G, Young SA, Duncan AJ. Hydrolysis of glucosinolates to isothiocyanates after ingestion of raw or microwaved cabbage by human volunteers. Cancer Epidemiol Biomarkers Prev. 2004;13(1):125-131.  (PubMed)

94.  Verkerk R, Dekker M. Glucosinolates and myrosinase activity in red cabbage (Brassica oleracea L. var. Capitata f. rubra DC.) after various microwave treatments. J Agric Food Chem. 2004;52(24):7318-7323.  (PubMed)

95.  Indole-3-Carbinol. Natural Medicines Online Database. 2008. Available at: http://naturaldatabase.com. Accessed December 2, 2008. 

96.  He YH, Friesen MD, Ruch RJ, Schut HA. Indole-3-carbinol as a chemopreventive agent in 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) carcinogenesis: inhibition of PhIP-DNA adduct formation, acceleration of PhIP metabolism, and induction of cytochrome P450 in female F344 rats. Food Chem Toxicol. 2000;38(1):15-23.  (PubMed)

97.  Lake BG, Tredger JM, Renwick AB, Barton PT, Price RJ. 3,3'-Diindolylmethane induces CYP1A2 in cultured precision-cut human liver slices. Xenobiotica. 1998;28(8):803-811.  (PubMed)

98.  Leibelt DA, Hedstrom OR, Fischer KA, Pereira CB, Williams DE. Evaluation of chronic dietary exposure to indole-3-carbinol and absorption-enhanced 3,3'-diindolylmethane in sprague-dawley rats. Toxicol Sci. 2003;74(1):10-21.  (PubMed)