Bortezomib inhibits cell-cell adhesion and cell migration and enhances epidermal growth factor receptor inhibitor-induced cell death in squamous cell cancer

• Published in: Cancer research (Chicago, Ill.) Vol. 67; no. 2; pp. 727 - 734
• Main Authors: LORCH, Jochen H, THOMAS, Tarita O, SCHMOLL, Hans-Joachim
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 15-01-2007
• Subjects: Adherens Junctions - drug effects; Adherens Junctions - metabolism; Antineoplastic agents; Antineoplastic Agents - pharmacology; Biological and medical sciences; Boronic Acids - pharmacology; Bortezomib; Carcinoma, Squamous Cell - drug therapy; Carcinoma, Squamous Cell - metabolism; Carcinoma, Squamous Cell - pathology; Cell Adhesion - drug effects; Cell Line, Tumor; Cell Movement - drug effects; Desmoglein 2 - metabolism; Desmoplakins - metabolism; Desmosomal Cadherins - metabolism; Drug Synergism; Focal Adhesion Kinase 1 - metabolism; Humans; Medical sciences; Pharmacology. Drug treatments; Pyrazines - pharmacology; Receptor, Epidermal Growth Factor - antagonists & inhibitors; Tongue Neoplasms - drug therapy; Tongue Neoplasms - metabolism; Tongue Neoplasms - pathology; Tumors; Antineoplastic agent; Squamous cell carcinoma; Growth factor receptor; Bortezomib; Cell death; Analog; Migration; Dipeptides; Cell cell interaction; Malignant tumor; Epidermal growth factor receptor; Apoptosis
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.can-06-2162

The lack of cell-cell adhesion and increased migration are key characteristics of cancer cells. The loss of expression of cell adhesion components and overexpression of components critical for cell migration, such as focal adhesion kinase (FAK), correlate with poor prognosis. Because alteration of protein turnover affects the expression levels and, in turn, may influence protein function, we investigated the effects of the proteasome inhibitor bortezomib on cell adhesion and migration in oral squamous cell cancer cell lines SCC68 and SCC15. Following treatment with bortezomib, protein levels of adherens junction components such as E-cadherin were unchanged. The desmosomal linker protein desmoplakin level was increased, whereas the protein level of the desmosomal cadherin, desmoglein 2, was diminished. Reduced desmoglein 2 levels correlated with the diminished strength of mechanical cell-cell adhesion. The protein level of the epidermal growth factor receptor (EGFR) increased after proteasome inhibition and EGFR inhibition with the EGFR-specific tyrosine kinase inhibitor PKI166 was able to restore cell-cell adhesion. Furthermore, we found that the combination of PKI166 with bortezomib enhanced the rate of cell death. Although the FAK protein level was unchanged following bortezomib treatment, recruitment of FAK phosphorylated at tyrosine residue 397 to the periphery of the cell was induced. Migration was reduced following treatment with bortezomib, which could potentially be explained by a prominent but disorganized actin fiber network revealed through immunofluorescence. Collectively, our results suggest that proteasome inhibition using bortezomib affects cell adhesion and cell migration profoundly and provides a rationale for its clinical use in conjunction with an EGFR inhibitor.