BTK Isoforms p80 and p65 Are Expressed in Head and Neck Squamous Cell Carcinoma (HNSCC) and Involved in Tumor Progression

DTL promotes head and neck squamous cell carcinoma progression by mediating the degradation of ARGLU1 to regulate the Notch signaling pathway

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, with a high incidence in squamous epithelium. The E3 ubiquitin ligase DTL is a component of the CRL4A complex and is widely involved in tumor progression. We aimed to analyze the role of DTL in HNSCC and to explore its mechanism of action. Through clinical analysis, we found that DTL is upregulated in HNSCC tissues and is associated with the tumor microenvironment and poor survival in patients. Through gain-of-function and loss-of-function assays, we showed that DTL promotes cell proliferation and migration in vitro and tumor growth in vivo. Mass spectrometry analysis and immunoprecipitation assays showed that DTL interacts with ARGLU1 to promote K11-linked ubiquitination-mediated degradation of ARGLU1, thereby promoting the activation of the CSL-dependent Notch signaling pathway. Furthermore, siARGLU1 blocks the inhibitory effects of DTL knockdown on HNSCC cells. In this study, we showed that DTL promotes HNSCC progression through K11-linked ubiquitination of ARGLU1 to activate the CSL-dependent Notch pathway. These findings identify a promising therapeutic target for HNSCC.

Influence of Bruton's Tyrosine Kinase (BTK) on Epithelial-Mesenchymal Transition (EMT) Processes and Cancer Stem Cell (CSC) Enrichment in Head and Neck Squamous Cell Carcinoma (HNSCC)

Constitutively active kinases play a crucial role in carcinogenesis, and their inhibition is a common target for molecular tumor therapy. We recently discovered the expression of two oncogenic isoforms of Bruton's Tyrosine Kinase (BTK) in head and neck squamous cell carcinoma (HNSCC), Btk-p80 and BTK-p65. However, the precise role of BTK in HNSCC remains unclear. Analyses of a tissue microarray containing benign and malignant as well as inflammatory tissue samples of the head and neck region revealed the preferential expression of BTK-p80 in malignant tissue, whereas BTK-p65 expression was confirmed in over 80% of analyzed metastatic head and neck tumor cases. Therefore, processes associated with metastasis, like cancer stem cell (CSC) enrichment and the epithelial-mesenchymal transition (EMT), which in turn depend on an appropriate cytokine milieu, were analyzed. Treatment of HNSCC-derived cell lines cultured under 3D conditions with the BTK inhibitor AVL-292 caused reduced sphere formation, which was accompanied by reduced numbers of ALDH1A1+ CSCs as well as biological changes associated with the EMT. Moreover, we observed reduced NF-κB expression as well as altered NF-κB dependent pro-tumorigenic and EMT-associated cytokine release of IL-6, IFNγ, and TNFα when BTK activity was dampened. Therefore, an autocrine regulation of the oncogenic BTK-dependent process in HNSCC can be suggested, with BTK inhibition expected to be an effective treatment option for HNSCC.

Bruton's Tyrosine Kinase Inhibitors (BTKIs): Review of Preclinical Studies and Evaluation of Clinical Trials

In the last few decades, there has been a growing interest in Bruton's tyrosine kinase (BTK) and the compounds that target it. BTK is a downstream mediator of the B-cell receptor (BCR) signaling pathway and affects B-cell proliferation and differentiation. Evidence demonstrating the expression of BTK on the majority of hematological cells has led to the hypothesis that BTK inhibitors (BTKIs) such as ibrutinib can be an effective treatment for leukemias and lymphomas. However, a growing body of experimental and clinical data has demonstrated the significance of BTK, not just in B-cell malignancies, but also in solid tumors, such as breast, ovarian, colorectal, and prostate cancers. In addition, enhanced BTK activity is correlated with autoimmune disease. This gave rise to the hypothesis that BTK inhibitors can be beneficial in the therapy of rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), Sjögren's syndrome (SS), allergies, and asthma. In this review article, we summarize the most recent findings regarding this kinase as well as the most advanced BTK inhibitors that have been developed to date and their clinical applications mainly in cancer and chronic inflammatory disease patients.