Nitric oxide synthase expression is downregulated in basal cell carcinoma of the head and neck.

The small molecule nitric oxide (NO) has many actions, most of which are poorly understood. Recently, NO and related compounds have been implicated in skin damage caused by ultraviolet light although their exact role is not clear. We undertook an immuno histochemical study to assess the expression of type II NO synthase (NOS2) and type III (NOS3) in basal cell carcinomas (BCCs) of the head and neck. In all 48 cases studied, NOS2 was found in the basal cell layer of the skin at the tumour margin but it w as significantly reduced in the tumour epithelial cells (P=0.001). NOS3 was localized to the endothelium of the blood vessels in both skin and tumour in all cases, and it was not seen in the tumour epithelial cells. The results suggest that expression of NOS is down-regulated in basal cell carcinomas. Copyright 2000 The British Association of Oral and Maxillofacial Surgeons.