pki-166 and Mouth-Neoplasms

The epidermal growth factor receptor (EGFR) has been proposed as a key modulator of cadherin-containing intercellular junctions, particularly in tumors that overexpress this tyrosine kinase. Here the EGFR tyrosine kinase inhibitor PKI166 and EGFR blocking antibody C225, both of which are used clinically to treat head and neck cancers, were used to determine the effects of EGFR inhibition on intercellular junction assembly and adhesion in oral squamous cell carcinoma cells. EGFR inhibition resulted in a transition from a fibroblastic morphology to a more epithelial phenotype in cells grown in low calcium; under these conditions cadherin-mediated cell-cell adhesion is normally reduced, and desmosomes are absent. The accumulated levels of desmoglein 2 (Dsg2) and desmocollin 2 increased 1.7-2.0-fold, and both desmosomal cadherin and plaque components were recruited to cell-cell borders. This redistribution was paralleled by an increase in Dsg2 and desmoplakin in the Triton-insoluble cell fraction, suggesting that EGFR blockade promotes desmosome assembly. Importantly, E-cadherin expression and solubility were unchanged. Furthermore, PKI166 blocked tyrosine phosphorylation of Dsg2 and plakoglobin following epidermal growth factor stimulation, whereas no change in phosphorylation was detected for E-cadherin and beta-catenin. The increase in Dsg2 protein was in part due to the inhibition of matrix metalloproteinase-dependent proteolysis of this desmosomal cadherin. These morphological and biochemical changes were accompanied by an increase in intercellular adhesion based on functional assays at all calcium concentrations tested. Our results suggest that EGFR inhibition promotes desmosome assembly in oral squamous cell carcinoma cells, resulting in increased cell-cell adhesion.

Topics: Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Cadherins; Calcium; Carcinoma, Squamous Cell; Cell Adhesion; Cell Communication; Cell Line, Tumor; Cetuximab; Culture Media, Conditioned; Cytoskeletal Proteins; Desmocollins; Desmoglein 2; Desmogleins; Desmoplakins; Desmosomes; Dose-Response Relationship, Drug; ErbB Receptors; gamma Catenin; Humans; Immunoblotting; Microscopy, Phase-Contrast; Mouth Neoplasms; Phenotype; Phosphorylation; Precipitin Tests; Pyrimidines; Pyrroles; Subcellular Fractions; Tyrosine

Because survival for patients with oral cancer has not improved over the past 25 years, new approaches for treatment are needed. Targeted molecular therapy against epidermal growth factor receptor (EGFR) has shown promise as an adjuvant therapy in preliminary studies in several solid tumors, including head and neck cancer. The objective of this study was to determine the efficacy of paclitaxel and PKI166, a novel inhibitor of EGFR, against oral cavity cancer.. JMAR human oral cancer cells were pretreated for 1 h with PKI166 and then stimulated with epidermal growth factor. EGFR-specific tyrosine kinase autophosphorylation measured by Western immunoblotting was inhibited by PKI166 in a dose-dependent fashion at all doses tested (0.01-1 micro M). Next, the induction of apoptosis in JMAR cells treated with paclitaxel (0.001 to 0.1 micro M) with or without PKI166 (0, 1, or 2 micro M) was determined using a propidium iodide assay. The addition of 2.0 micro M PKI166 significantly increased tumor cell death, shifting the amount of paclitaxel needed to induce apoptosis in 50% of cells from 0.1 to 0.001 micro M. These in vitro findings were confirmed using an orthotopic model of oral cancer. JMAR oral cancer cells were implanted into the tongues of nude mice. After lingual tumors developed, mice were randomized into four groups (n = 10): (a) oral PKI166 (100 mg/kg); (b) i.p. paclitaxel (200 micro g/wk); (c) PKI166 and paclitaxel; or (d) placebo. Mice treated with PKI166/paclitaxel demonstrated a significant increase in survival (P = 0.028). After necropsy, all tongue tumors were evaluated for apoptosis by the terminal deoxynucleotidyl transferase-mediated nick end labeling assay. A greater apoptotic fraction of tumor cells was found in tumors of mice treated with paclitaxel and PKI166 as compared with the other treatment groups (136.4 versus 37.8; P = 0.016).. Combination therapy with paclitaxel and PKI166 prolongs survival in an orthotopic preclinical model of tongue cancer by increasing programmed cell death of oral cancer.

Topics: Animals; Antineoplastic Agents, Phytogenic; Apoptosis; Blotting, Western; Cell Death; Cell Line, Tumor; Dose-Response Relationship, Drug; ErbB Receptors; Head and Neck Neoplasms; Humans; In Situ Nick-End Labeling; Ligands; Male; Mice; Mice, Nude; Microscopy, Fluorescence; Mouth Neoplasms; Neoplasms; Paclitaxel; Phosphorylation; Propidium; Pyrimidines; Pyrroles; Tongue; Tongue Neoplasms; Tyrosine