[Show abstract][Hide abstract] ABSTRACT: Head and neck squamous cell carcinoma (HNSCC) is an aggressive epithelial malignancy. It is known to be the most common neoplasm appearing in the upper aerodigestive tract. The poor 5‑year survival rate has remained unchanged in the last decades even though improved techniques in surgery, radiation and chemotherapy have been established. In contrast to the overall decreasing incidence of head and neck cancer in the US, the incidence of HPV-associated oropharyngeal cancer is increasing, indicating the importance of viral etiology. Furthermore, growth and invasion of HNSCC are strongly influenced by the extracellular matrix (ECM). Matrix metalloproteinases (MMP) have been shown to play key roles in the remodeling of the ECM. Imatinib (STI 571) was originally designed to inhibit the BCR-ABL tyrosine kinase in chronic myeloid leukaemia. But it also has an inhibitory impact, e.g., on the protein-tyrosine-kinase (PTK) receptor c-kit and on its PTK activity in HNSCC. In this study, we incubated the HNSCC cell lines HNSCC 11A and 14C and the p16-positive SCC line CERV196 with increasing concentrations of imatinib or carboplatin. After an incubation time of up to 10 days, we evaluated MMP-2 and -14 expression by ELISA techniques and immunohistochemistry. MMP-2 and -14 expression was demonstrated in all incubated tumor cell lines. Especially incubation with imatinib resulted in a significant decrease in MMP expression in incubated cell lines. Our results indicate that the expression of MMP-2 and -14 is suppressed in the presence of imatinib. Thus, imatinib may exert in part its inhibitory effect on malignant cell growth via the blockage of the signal transduction of PTK receptors. Further studies are warranted, especially keeping in mind the moderate toxicity of imatinib.
[Show abstract][Hide abstract] ABSTRACT: The most common neoplasm arising in the upper aerodigestive tract is head and neck squamous cell carcinoma (HNSCC). Tumor growth, invasion and systemic dissemination is a multistep process of dysregulated cellular signaling pathways and an altered cell-cell and cell-matrix interaction. Aberrant Wnt/β-catenin signaling is linked to tumor development and dissemination in several tumor entities. β-catenin is a multifunctional protein within the canonical Wnt pathway, which is an important factor for reducing cell-cell adhesion in malignant tissue and for triggering cell cycle progression and unscheduled proliferation. Another pivotal factor in carcinogenesis is the tyrosine kinase receptor c-kit, which in the case of dysregulated expression is associated with neoplastic transformation in epithelial tissue. This study evaluates the expression pattern of secreted and nuclear β-catenin and c-kit in p16-positive and HPV-negative squamous cell carcinomas (SCC) and the vulnerability of therapy with the tyrosine kinase inhibitor imatinib as a potential targeted treatment modality compared to platinum-based chemotherapeutic drugs. The different squamous tumor cell lines were incubated with increasing concentrations of carboplatin (3 or 7.5 µmol/ml) and imatinib (18 or 30 µmol/ml). ELISA and immunohistochemical methods were carried out after 48, 72, 120, 192 and 240 h. We detected a reliable trend towards significantly decreased cytosolic and nuclear β-catenin and c-kit expression levels in p16-positive SCC and non-HPV HNSCC cells induced by imatinib exposure for an extended incubation period, whereas platinum-based agents had no or, at best, a slight influence. Virus-transformed squamous cell carcinoma (CERV196) cells were characterized by a reduced susceptibility to an imatinib-altered β-catenin expression. Further studies are planned to investigate this observance in HPV-positive HNSCC in vitro. The implementation of a selective molecular therapy in established chemotherapeutic regimes may enhance the efficacy of platinum-based chemotherapy without increased toxicity and could thus improve the clinical outcome in HNSCC, irrespective of the HPV status.