NF-κB; AhR; Human Endogenous Metabolite
Indole-3-carbinol (I3C) targets aryl hydrocarbon receptor (AhR) [1]
Indole-3-carbinol (I3C) targets nuclear factor-κB (NF-κB) signaling pathway [2]
Indole-3-carbinol (I3C) targets p53 signaling pathway [2]

It has been discovered that indole-3-carbinol (I3C) has low toxicity toward healthy monocytes and inhibits the proliferation of THP-1 cells in a dose- and time-dependent manner. When exposed to indole-3-carbinol, the AhR target genes CYP1A1 and IL1β are overexpressed (p<0.05 to p<0.001). Indole-3-carbinol's antiproliferative properties are linked to its ability to program cell death. In THP-1 cells, indole-3-carbinol downregulates BCL2 while upregulating FasR (p<0.05 to p<0.001). Using flow cytometry, it is also possible to see G1 cell cycle arrest. Indole-3-carbinol treatment results in overexpression of G1-acting cell cycle genes (P21, P27, and P53) (p<0.05 to p<0.001) and downregulation of CDK2 (p<0.01 to p<0.001)[1].In pre-B acute lymphoblastic leukemia cells, Indole-3-carbinol inhibits NF-κB activity while promoting the p53 pathway[2].

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Indole-3-carbinol (I3C) (25-100 μM) dose-dependently induced G1 cell cycle arrest and apoptosis in THP-1 monocytic cells. It activated AhR, upregulated AhR target genes (CYP1A1, CYP1B1) mRNA/protein expression, and increased p21 and p27 (cell cycle inhibitors) levels. At 100 μM, apoptotic rate reached 38.6% (control: 4.2%), with increased caspase-3/9 cleavage and Bax/Bcl-2 ratio [1]
Indole-3-carbinol (I3C) (50-200 μM) suppressed proliferation of pre-B acute lymphoblastic leukemia cells (NALM-6, Reh) with IC50 values of 85 μM (NALM-6) and 92 μM (Reh). It inhibited NF-κB activity (reduced p65 nuclear translocation and IκBα phosphorylation), activated p53 pathway (upregulated p53 and p21), and induced apoptosis (increased Annexin V-positive cells and caspase-3 activation) [2]

B cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most common type of cancer in children. Dramatic improvements in primary therapy for childhood ALL have led to an overall cure rate of 80 %, providing opportunities for innovative combined-modality strategies that would increase cure rates while reducing the toxic side effects of current intensive regimens. In this study, we report that indole-3-carbinol (I3C), a natural phytochemical found in cruciferous vegetables, had anti-leukemic properties in BCP-ALL NALM-6 cells. I3C induced cell growth inhibition by G1 cell cycle arrest and triggered apoptosis in a dose- and time-dependent manner. p53, p21, and Bax proteins showed increased expression after I3C treatment. Real-time PCR analysis of pro-apoptotic p53 target genes revealed up-regulation of PUMA, NOXA, and Apaf-1. I3C also suppressed constitutive nuclear factor-κB (NF-κB) activation and inhibited the protein expression of NF-kappa B-regulated antiapoptotic (IAP1, Bcl-xL, Bcl-2, XIAP) and proliferative (c-Myc) gene products. Coadministration of I3C with the topoisomerase II inhibitor, doxorubicin, potentiates cytotoxic effects compared with either agent alone. Apoptosis induction by the drug combination was associated with enhanced caspase-9 activation and PARP cleavage. Furthermore, I3C abolished doxorubicin-induced NF-κB activity as evidenced by decreased nuclear accumulation of p65, inhibition of IκBα phosphorylation and its degradation, and decreased NF-κB DNA-binding activity. Western blot analysis revealed that doxorubicin-induced Bcl-2 protein expression was inhibited by I3C. Overall, our results indicated that using nontoxic agents, such as I3C, in combination with anthracyclines might provide a new insight into the development of novel combination therapies in childhood BCP-ALL.[2]

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AhR activation assay: THP-1 cells were treated with Indole-3-carbinol (I3C) (25-100 μM) for 24-48 h. Total RNA was extracted for RT-PCR to detect CYP1A1 and CYP1B1 mRNA levels. Nuclear protein was isolated, and AhR nuclear translocation was detected by Western blot. AhR-dependent luciferase reporter assay was performed by transfecting THP-1 cells with AhR-responsive reporter plasmid followed by I3C treatment [1]
NF-κB activity assay: Pre-B leukemia cells were treated with Indole-3-carbinol (I3C) (50-200 μM) for 24 h. Nuclear and cytoplasmic fractions were separated to detect p65 localization by Western blot. IκBα phosphorylation level was analyzed by Western blot using phospho-specific antibody. NF-κB luciferase reporter assay was conducted by transfecting cells with NF-κB-responsive plasmid and measuring luciferase activity after I3C treatment [2]

In a fully humidified environment with 5% CO2, THP-1 cells are cultured in RPMI 1640 with 10% FBS, 100 U/mL penicillin, 100 mg/mL streptomycin, and 2 mM Glutamax. Six-well plates are seeded with cells (2-5×105 mL-1), and the cells are then resuspended in full growth medium. Then, 10 ng/mL phorbol 12-myristate 13-acetate is added to THP-1 monocyte cells as a tumor promoter to cause stable differentiation into adhering macrophage-like cells and overexpression of AhR. Following that, indole-3-carbinol (1, 10, 100μM, and 1 mM) is treated with various concentrations in the cells. In a 24-well plate with different concentrations of indole-3-carbinol, HP-1 cells and enriching normal monocytes are seeded at a density of 5 104 cells/well. After 24 and 48 hours, MTT assay is performed. Triplicates of the cells are incubated for 20 hours in a final volume of 200 mL of Phenol Red-free RPMI 1640. Each well is filled with an aliquot of 20 mL of MTT solution (5 mg/mL), which is then left to sit for 4 hours. Crystals of formazan grow. Then, as a cell lysis solution, 300 mL of DMSO is added to each well. Spectrophotometry at 570 nm is used to measure cell viability percentage[1].

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THP-1 cell cycle and apoptosis assay: THP-1 cells were seeded in 6-well plates and treated with Indole-3-carbinol (I3C) (25-100 μM) for 48 h. Cell cycle distribution was analyzed by PI staining and flow cytometry. Apoptosis was detected by Annexin V-FITC/PI double staining and flow cytometry. Protein expression (AhR, CYP1A1, CYP1B1, p21, p27, Bax, Bcl-2, cleaved caspase-3/9) was detected by Western blot; mRNA levels were measured by RT-PCR [1]
Pre-B leukemia cell proliferation and signaling assay: NALM-6 and Reh cells were cultured in 96-well plates and treated with Indole-3-carbinol (I3C) (25-200 μM) for 72 h. Cell viability was assessed by MTT assay to calculate IC50 values. Apoptosis was analyzed by Annexin V-FITC staining and flow cytometry. Western blot was used to detect p53, p21, NF-κB p65 (nuclear/cytoplasmic), phospho-IκBα, and cleaved caspase-3 expression [2]

Subcutaneous injection of LDLo 500 mg/kg in rats (concentration up to 100 μM) showed no significant cytotoxicity to normal human peripheral blood mononuclear cells (cell viability > 85%) [1]. Indole-3-methanol (concentration up to 200 μM) did not induce significant necrosis in pre-B cell leukemia cells (necrosis rate < 5%) [2].

[1]. Indole-3-carbinol induces G1 cell cycle arrest and apoptosis through aryl hydrocarbon receptor in THP-1 monocytic cell line.J Recept Signal Transduct Res. 2017 Oct;37(5):506-514.

[2]. Indole-3-carbinol suppresses NF-κB activity and stimulates the p53 pathway in pre-B acute lymphoblastic leukemia cells. Tumour Biol. 2015 May;36(5):3919-30.

[3]. Reactivation of PTEN tumor suppressor for cancer treatment through inhibition of a MYC-WWP1 inhibitory pathway. Science. 2019 May 17;364(6441). pii: eaau0159.

Indole-3-methanol is an indole alcohol with a hydroxymethyl group at the 3-position. It is a component of cruciferous vegetables and possesses anticancer activity. It is both a plant metabolite and an antitumor agent. Indole-3-methanol is currently being studied in the clinical trial NCT00033345 (Indole-3-methanol for the prevention of breast cancer in high-risk non-smoking women). Indole-3-methanol has been reported to be present in European red pine, Dalbergia odorifera, and several other organisms with relevant data. Indole-3-methanol is a cleavage product of the naturally occurring, orally absorbed glucosinolate glucosinolate. Glucosinolate is a natural compound widely found in various plant-based foods, including cruciferous vegetables, and possesses antioxidant and potential chemopreventive properties. Indole-3-methanol can scavenge free radicals and induce various hepatic cytochrome P450 monooxygenases. Specifically, the drug can induce the liver monooxygenase cytochrome P4501A1 (CYP1A1), thereby increasing the 2-hydroxylation of estrogen and increasing the production of the chemoprotective estrogen 2-hydroxyestrone. Indole-3-methanol (I3C) is a natural compound derived from cruciferous vegetables (broccoli, cauliflower, Brussels sprouts) and is obtained by the hydrolysis of glucosinolate [1][2]. Indole-3-methanol (I3C) exerts its anti-leukemic effect through a dual mechanism: inhibiting NF-κB-mediated cell survival and activating p53-dependent cell cycle arrest and apoptosis [2]. Indole-3-methanol (I3C) induces monocyte apoptosis in an AhR-dependent manner. This is related to the upregulation of AhR targeting cytochrome P450 enzymes and cell cycle inhibitors [1].

C9H9NO

147.18

147.068

C, 73.45; H, 6.16; N, 9.52; O, 10.87

700-06-1

3712

White to off-white solid powder

1.3±0.1 g/cm3

360.6±17.0 °C at 760 mmHg

96-99 °C(lit.)

171.9±20.9 °C

0.0±0.8 mmHg at 25°C

1.705

0.96

2

1

1

11

138

0

O([H])C([H])([H])C1=C([H])N([H])C2=C([H])C([H])=C([H])C([H])=C12

IVYPNXXAYMYVSP-UHFFFAOYSA-N

InChI=1S/C9H9NO/c11-6-7-5-10-9-4-2-1-3-8(7)9/h1-5,10-11H,6H2

1H-indol-3-ylmethanol

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (16.99 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (16.99 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (16.99 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)