CH-223191

Disruption of the epidermal barrier contributes to skin disorders such as atopic dermatitis and psoriasis. The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, plays a key role in skin homeostasis and immune regulation. While traditionally associated with toxicity, AhR has emerged as a promising therapeutic target, particularly via tryptophan-derived indoles. To support AhR research in a dermatological context, we developed AhaRaCaT, a stable luciferase-based reporter cell line derived from human keratinocytes (HaCaT), enabling the assessment of AhR transcriptional activity in a skin-relevant model. We characterized the inducibility of AhaRaCaT in response to model AhR ligands (TCDD, BaP, FICZ) in dose- and time-dependent assays. Antagonist profiling with MNF, CH223191, GNF, carvone, and jasmone yielded IC50 values over 4- and 24-hour exposures. A panel of indoles previously studied in other models was evaluated for AhR activation, revealing a robust luciferase response at 4 h that declined at 24 h, consistent with trends observed in other cell types. Selected indoles also induced CYP1A1 mRNA expression and reversed cytokine-induced downregulation of filaggrin in HaCaT cells, highlighting their potential in mitigating inflammation-associated skin barrier defects. In summary, the AhaRaCaT cell line offers a sensitive and physiologically relevant tool for studying AhR signaling in skin, with broad applications in toxicology, dermatological research, and the development of AhR-targeted therapies for inflammatory skin diseases.

Lenvatinib serves as a first-line systemic therapy for advanced hepatocellular carcinoma (HCC), yet the development of resistance poses a major clinical challenge. The purpose of this study is to investigate the mechanisms underlying lenvatinib resistance in HCC and identify potential interventions. We established lenvatinib-resistant HuH7 and Hep3B cell lines and conducted in vitro, bioinformatics, and biochemical assays to explore and validate the mechanisms underlying acquired resistance to lenvatinib in HCC. Additionally, cellular xenograft models of lenvatinib-resistant HCC were utilized to assess tumor responses to a novel drug treatment regimen. Our findings revealed a shift from suppression to activation in the expression of p-ERK1/2 and Cyclin D1 in HCC cells as they transitioned from sensitivity to resistance to lenvatinib. Furthermore, we demonstrated that targeting ERK1/2 with ravoxertinib (an ERK1/2 inhibitor) could significantly enhance the sensitivity of resistant HCC cells to lenvatinib therapy. Through transcriptome data analysis and experimental validation, we identified amphiregulin (AREG), induced autocrinely by lenvatinib, as a critical mediator that activates the EGFR-ERK1/2 signaling pathway, leading to increased Cyclin D1 expression in HCC cells. Mechanistically, lenvatinib promotes aryl hydrocarbon receptor (AHR) nuclear translocation, directly activating AREG transcription. Using in vivo models, we further confirmed that inhibiting ERK1/2 with ravoxertinib or AHR with CH-223191 (an AHR inhibitor) could overcome lenvatinib resistance in HCC. Overall, lenvatinib-induced AHR activation promotes AREG expression, which subsequently facilitates the acquisition of drug resistance in HCC via the EGFR-ERK1/2-CyclinD1 signaling axis. Targeting ERK1/2 and AHR effectively improved the response to lenvatinib treatment in resistant HCC.