LAUSR

Simple Summary Treatment success of head and neck cancers (HNSCC) is often hindered by chemoresistance. In this study, next-generation sequencing transcriptomics and CRISPR/Cas9 knockout strategies were used to identify cisplatin resistance mechanisms and potential (personalized) biomarkers. Moreover, employing a tiered experimental pipeline, the cisplatin uptake transporter VRAC was found to be critical for cisplatin sensitivity and specificity in 2D/3D-HNSCC cell culture models as well as for tumor relapses in the clinical setting. Our study suggests exploiting VRAC as a potential drug target as well as a personalized prognostic biomarker to improve the treatment of HNSCC patients in the future. Abstract Treatment success of head and neck cancers (HNSCC) is often hindered by tumor relapses due to therapy resistances. This study aimed at profiling cisplatin resistance mechanisms and identifying biomarkers potentially suitable as drug targets and for patient stratification. Bioinformatic analyses of suggested resistance factors in a cohort of 565 HNSCC patients identified the VRAC ion channel as a clinically relevant indicator for recurrent diseases following radiochemotherapy (p = 0.042). Other drug import/export transporters, such as CTR1, OCT1, or MRP1, were found to be less relevant. To experimentally verify VRAC’s critical role for cisplatin resistance, we used CRISPR/Cas9 knockout resulting in cisplatin-resistant HNSCC cells, which could be resensitized by VRAC expression. Next-generation sequencing further underlined VRAC’s importance and identified VRAC-regulated signaling networks, potentially also contributing to cisplatin resistance. CTR1, OCT1, or MRP1 did not contribute to increased cisplatin resistance. In addition to two-dimensional HNSCC models, three-dimensional tumor spheroid cultures confirmed VRAC’s unique role for cisplatin sensitivity. Here, resistance correlated with DNA damage and downstream apoptosis. The cisplatin specificity of the identified VRAC pathway was verified by testing paclitaxel and doxorubicin. Our results were independently confirmed in naturally occurring, cisplatin-resistant HNSCC cancer cell models. Collectively, we here demonstrate VRAC’s role for cisplatin resistance in HNSCC and its relevance as a potential drug target and/or prognostic biomarker for chemotherapy resistance.