POSTIRRADIATED SUBMANDIBULAR-GLAND - A POTENTIAL MODEL TO STUDY SALIVARY GLAND RADIOPROTECTION AND TUMORIGENESIS

Theoretical reserve cells located in the intercalated and excretory du cts are postulated to be responsible for salivary gland tumourigenesis , with acinar cells playing no role in this process. Animal models, on e using low-dose radiation to rat submandibular glands, indicate that this hypothesis is incorrect. Few human models have been devised to de monstrate and verify this theory. Submandibular glands in the field of ionizing radiation, as external-beam radiotherapy for head and neck t umours, were examined using an immunocytochemical technique and an ant ibody to proliferating cell nuclear antigen (PCNA), a specific marker for cycling cells. In the nonirradiated gland, nuclei positive for PCN A were seen in acinar as well as ductal cells of all types. Six months post irradiation, human submandibular glands show increased prolifera tive rates in both ductal and acinar cells that are significantly grea ter than control glands (p = .012). Based on this regenerative capacit y, postirradiated human submandibular glands might serve as a model to investigate various treatment modalities for the prevention of radiat ion damage to acinar cells and the consequent patient morbidity that d evelops due to xerostomia. As well, these results suggest that even in humans, acinar cells are potential targets for carcinogenic agents an d that current histogenic concepts for salivary gland tumourigenesis a re incorrect.