Activation of the Aryl Hydrocarbon Receptor–Cytochrome P450 1A1 Axis Mediates the Selective Cytotoxicity of 2-Phenyl-Imidazo[1,2- <i>a</i> ]Pyridine Derivatives in Triple-Negative Breast Cancer Cells

High Resolution Image Download MS PowerPoint Slide Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype associated with poor clinical outcomes and limited treatment options. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that regulates xenobiotic metabolism through the induction of many cytochrome P450 enzymes such as CYP1A1. In this study, we investigated three 2-phenyl-imidazo[1,2- a ]pyridine derivates (X19724, X19728, and X15695), previously developed as selective estrogen receptor degraders, for their activity in TNBC cell lines. All three compounds activated AHR-dependent transcriptional activity and exhibited selective cytotoxicity toward MDA-MB-468 cells among a panel of TNBC and nontumorigenic mammary epithelial cell lines. Nonresponsive TNBC cell lines lacked either detectable AHR expression or inducible CYP1A1 expression. In sensitive MDA-MB-468 cells, cytotoxicity was accompanied by membrane permeabilization. Genetic ablation or pharmacological antagonism of AHR, as well as inhibition of CYP1A1 activity, markedly attenuated compound-induced cytotoxicity. Proteomic analysis further revealed enrichment of pathways related to phospholipid synthesis and base excision repair, along with increased abundance of proteins associated with DNA damage responses. Finally, among the three compounds, X15695 exhibited the greatest metabolic stability following incubation with human liver microsomes. Collectively, these findings support a model in which activation of AHR-CYP1A1 axis contributes to selective cytotoxicity in TNBC cells, highlighting this pathway as a potential mechanistic vulnerability that can be exploited by imidazopyridine derivatives.