MUC1-C PROMOTES CHRONIC INFLAMMATION IN THE PROGRESSION OF HEAD AND NECK SQUAMOUS CELL CARCINOMAS
Mucin 1 (MUC1) is aberrantly expressed in adenocarcinomas of epithelial barrier tissues and contributes to their progression. Less is known about involvement of MUC1 in the pathogenesis of squamous cell carcinomas (SCCs). The present work demonstrates that the MUC1 gene is upregulated in advanced head and neck SCCs (HNSCCs) and, as determined by scRNA-seq analysis, is expressed in the malignant cell populations of HNSCC tumors. Studies of HNSCC cell lines demonstrate that the MUC1-C subunit regulates expression of (i) RIG-I and MDA5 pattern recognition receptors, (ii) STAT1 and interferon (IFN) regulatory factors, and (iii) downstream IFN-stimulated genes (ISGs). MUC1-C integrates STAT1 with induction of the ?Np63 and SOX2 genes that are aberrantly expressed in HNSCCs. We also show that MUC1-C/STAT1 signaling activates the NFE2L2 gene and, in turn, MUC1-C binds directly to NRF2 in regulating redox balance. In extending these HNSCC cell dependencies, we demonstrate that MUC1-C is necessary for NOTCH3 expression, self-renewal capacity and tumorigenicity. These results indicate that MUC1-C is a common effector that integrates STAT1-mediated chronic inflammation with regulation of the ?Np63, SOX2, NRF2 and NOTCH3 TFs. Our findings indicate that MUC1-C drives progression of the HNSCC CSC state and is a target for advanced HNSCC treatment. Overall design: RNA sequencing analysis was used to identify changes in HNSCC cells (CAL27 & HSC3) after doxycycline inducible knockdown of MUC1