Differential effect of submandibular gland resection on the growth of pancreatic cancer in cheek pouch and subcutaneous tissue

Exogenous administration of epidermal growth factor (EGF) enhances tumor growth of H2T, a hamster pancreatic cancer that is inoculated in the cheek pouch. The effect of endogenous EGF on tumor growth, however, is not known. The main source of EGF in the body is the submandibular glands. This study examined the influence of submandibular gland resection (SMx) on H2T tumor growth in the cheek pouch and compared it to the growth in SC tissue. Bilateral SMx or sham operation was performed on male Syrian golden hamsters. In 30 hamsters (n=15 for each operation group), 5×10⁴ and 5×10⁵ H2T cells were inoculated in the bilateral cheek pouches and intrascapular SC tissue, respectively (Exp. 1). In another 30 hamsters (n=15 for each operation group), 5×10⁵ and 1×10⁶ H2T cells were inoculated at the same sites (Exp. 2). Two longest perpendicular diameters of the tumor were measured once a week for 12 wk (Exp. 1) or 8 wk (Exp. 2), and the tumor area was calculated. The tumor area in the cheek pouch became significantly smaller in the SMx group than the sham-operated group after the 8th wk (Exp. 1) or the 7th wk (Exp.2). On the other hand, the tumor area in the SC tissue did not show any difference between groups through the experiments. Although body wt in the SMx group was significantly less than the sham group in exp. 2, the clearly differential influence of SMx on the tumor growth in the cheek pouch and SC tissue indicates that H2T tumor growth in the cheek pouch is locally stimulated by the submandibular glands.