Designing and utilizing a c-Rel specific bioassay in drug repurposing screen for HNSCC

Authors

• KA Altwegg
• KE King
• D Blivis
• TC Voss
• NJ Martinez
• WC Weinberg
• MJ Henderson

Abstract

Head and neck squamous cell carcinomas (HNSCCs) rank as the 6th most prevalent cancer globally, with approximately 890,000 new cases and a projected 30% increase by 2030. CDKN2A and TP53 mutations are common in HNSCC tumors, with TP53 family members TP63 and TP73 also frequently altered. TP63 produces ΔNp63 and TAp63 isoforms, with ΔNp63α being notably overexpressed in many HNSCCs. We have demonstrated that ΔNp63α impedes differentiation-induced growth arrest by activating and promoting nuclear localization of c-Rel, a member of the nuclear factor-κB (NFκB) family. This interaction selectively affects c-Rel, without influencing other NFκB subunits. In both human HNSCCs and normal keratinocytes overexpressing ΔNp63α, ΔNp63α complexes suppress transcription of the cyclin-dependent kinase inhibitor p21WAF1, indicating a role in growth regulation. We observed strong nuclear co-localization of ΔNp63α and c-Rel in the proliferative zones of primary HNSCCs, underscoring their relationship. Prior studies indicated proteasome inhibitors affect RelA but not c-Rel in clinical trial specimens of HNSCC, prompting our focus on identifying small molecules that block c-Rel nuclear localization. In vitro stimulation of HNSCC cells with TNFα induces nuclear localization of c-Rel. To screen for compounds inhibiting c-Rel localization, we developed and optimized a 384-well and 1536-well format high throughput bioassay using immunocytochemistry and automated image analysis to quantify nuclear c-Rel localization in the presence of TNFα. Using this assay, we interrogated the NCATS Pharmaceutical Collection of 2,998 FDA-approved drugs, resulting in 81 hits for further investigation. Our findings provide insights into therapeutic strategies and drug repurposing targeting ΔNp63α:c-Rel interactions in HNSCC.

Scientific Focus Area: Cancer Biology

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