Cell experiment:

THP-1 cells are cultured in RPMI 1640 supplemented with 10% FBS, 100 U/mL penicillin, 100 mg/mL streptomycin and 2 mM Glutamax in a fully humidified atmosphere with 5% CO2. Cells (2-5×105 mL-1) are seeded in six well plates followed by resuspension in complete growth media. THP-1 monocyte cells are then treated with 10 ng/mL phorbol 12-myristate 13-acetate as a tumor promoter to induce stable differentiation into attaching macrophage-like cells and overexpression of AhR. The cells are then treated with varying concentrations of Indole-3-carbinol (1, 10 and 100 μM, and 1 mM). THP-1 cells and enriching normal monocytes are seeded at 5×104 cells/well in 24-well plate with different concentrations of Indole-3-carbinol and observed for 24 and 48 h followed by MTT assay. The cells are incubated in triplicates in a final volume of 200 mL of Phenol Red free RPMI 1640 for 20 h . An aliquot of 20 mL of MTT solution (5 mg/mL) is added to each well and incubated for 4 h. Formazan crystals are formed. An amount of 300 mL DMSO is then added to each well as a cell lysis solution. Percentage of cell viability is assessed by spectrophotometry at 570 nm[1].

Indole-3-carbinol (I3C) inhibits NF-κB activity and also is an Aryl hydrocarbon receptor (AhR) agonist, and an inhibitor of WWP1 (WW domain-containing ubiquitin E3 ligase 1).

It is found that Indole-3-carbinol (I3C) inhibits the proliferation of THP-1 cells in a dose- and time dependent manner with minimal toxicity over normal monocytes. The AhR target genes (CYP1A1, IL1β) are overexpressed upon Indole-3-carbinol treatment (p<0.05 to p<0.001). The antiproliferative effects of Indole-3-carbinol are in association with programing cell death. Indole-3-carbinol downregulates BCL2 and upregulates FasR in THP-1 cells (p<0.05 to p<0.001). G1 cell cycle arrest is also observed using flow cytometry. G1-acting cell cycle genes (P21, P27 and P53) are overexpressed (p<0.05 to p<0.001), while CDK2 is downregulated upon Indole-3-carbinol treatment (p<0.01 to p<0.001)[1].Indole-3-carbinol suppresses NF-κB activity and stimulates the p53 pathway in pre-B acute lymphoblastic leukemia cells[2].

References:
[1]. Mohammadi S, et al. 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]. Safa M, et al. 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]. Lee YR, et al. Reactivation of PTEN tumor suppressor for cancer treatment through inhibition of a MYC-WWP1 inhibitory pathway. Science. 2019 May 17;364(6441). pii: eaau0159.