STIMULATORY EFFECT OF EGF AND INHIBITORY EFFECT OF SIALOADENECTOMY ONGROWTH OF AN EGF RECEPTOR-HYPERPRODUCING HUMAN GASTRIC-CANCER XENOGRAFT IN NUDE-MICE

We recently established epidermal growth factor (EGF) receptor-hyperpr oducing human gastric cancer xenografts in nude mice. The present stud y was designed to examine whether the growth of a xenograft having 1,0 98 +/-276 fmol/mg protein of EGF receptor would either be stimulated b y the administration of EGF or inhibited by the removal of the submand ibular glands (sialoadenectomy) which contain a large amount of EGF. A miniosmotic pump containing 2 mug or 20 mug of EGF was implanted on t he back of the animals in the EGF stimulation experiments. The tumor g rowth was stimulated by the administration of EGF (P < 0.01), and the doubling time of the tumor was reduced relative to the controls (P < 0 .01). Both the mitotic indices and the bromodeoxyuridine (BrdU)-labeli ng indices of the tumor were higher than those of the controls (P < 0. 01). Tumor growth inhibited by the sialoadenectomy (P < 0.05) while th e tumor doubling time was prolonged compared with the sham-operated mi ce (P < 0.05). These results suggest that the growth of a human gastri c cancer xenograft may be modulated by EGF.