Enhancement of Ad-p53 therapy with docetaxel in head and neck cancer

Objective. The objective of this project was to determine the mechanisms in which docetaxel enhances Ad-p53 tumor suppressive effects in head and neck cancer. Background: In advanced head and neck squamous cell carcinoma (HNSCC), the 5-year survival rate is less than 40%. Because patients with advanced HNSCC have a high rate of local-regional failure (40-60%) with existing treatment modalities, aggressive local therapy approaches need to be developed. Previous data show that docetaxel or Ad-p53 alone have significant anti-tumor activity in HNSCC. Before testing whether a combination approach (Ad-p53 and docetaxel) could be developed in clinical trials, preclinical experiments were performed. Methods: The p53 gene was overexpressed in 2 head and neck squamous carcinoma (HNSCC) cell lines, HN30 and HN12, and a murine Balb/c mucoepidermoid carcinoma (BMEC) cell line. Docetaxel's enhancement of adenoviral transduction (bGAL expression), coxsakie-adenovirus receptor (CAR) expression, and Ad-p53 induction of apoptosis (Annexin V expression) were measured. The modulation of regulators in the cell cycle, apoptosis and signal transduction pathways were measured using Western blot. Results: Docetaxel increased adenoviral transduction, which was dependent on the dose of docetaxel and levels of Ad-bGAL. The enhanced viral transduction was due in part to the upregulation of the CAR protein. Pretreatment with docetaxel enhanced Ad-p53-induced apoptosis through increased expression of exogenous p53. Together, the combination of docetaxel and Ad-p53 altered expression of key regulators in the cell cycle, apoptosis and signal transduction pathways with an increase in the expression of p53, bax, cleaved PARP, cleaved caspase-3 and phosphorylation of c-Jun at position at (63)Ser. Cyclin A and B1 expression were down regulated by docetaxel and Ad-p53. When comparing the docetaxel-resistant to sensitive cell lines, the altered expression of p27 and skp1 by docetaxel and Ad-p53 were dissimilar between these cell lines. Conclusions: Docetaxel enhanced Ad-p53 transduction and increased expression of exogenous p53 gene transfer, apoptosis, and antitumor mechanisms. These results support a clinical combination of docetaxel with p53 gene therapy in patients with head and neck cancer.