Gene therapy for head and neck cancer. Comparing the tumor suppressor gene p53 and a cell cycle regulator WAF1/CIP1 (p21).

Objective: To compare the efficacy of the tumor suppressor gene wild-type p 53 with that of cell-cycle regulator WAF1/CIP1 as single-agent gene therapy for squamous cell carcinoma of the head and neck. Experimental Methods and Design: Recombinant cytomegalovirus-promoted adenoviruses containing the wild-type p 53 or WAF1/CIP1 ( p 21) genes were transiently introduced into squamous cell carcinoma of the head and neck cell lines. Standard Western blot analysis was used to determine expression in these cells of the proteins encoded by these genes. A nude mouse xenograft model of squamous cell carcinoma of the head and neck was used to investigate the in vivo efficacy of repeated gene therapy interventions. Results: Western blot analysis showed marked induction of the WAF1/CIP1 tumor suppressor gene product by both the p 21 adenovirus and the wild-type p 53 adenovirus (as a secondarily transcribed product). In vitro growth curves demonstrated that the wild-type p 53 adenovirus significantly inhibited cell growth in these cell lines, whereas direct induction of the p 21 gene product did not. Repeated infection with wild-type p 53 adenovirus significantly reduced the size of established subcutaneous tumors, whereas infection with a replication defective viral control did not. Conclusions: Wild-type p 53 adenovirus exhibits substantial in vitro and in vivo tumor suppressor activity in squamous cell carcinoma of the head and neck cell lines. This tumor suppression is not a function of the induced WAF1/CIP1 ( p 21) transcriptional product. Further studies are required to investigate the potential for induction of apoptosis by gene therapy. (Arch Otolaryngol Head Neck Surg. 1996;122:489-493)