Influence of inoculation site on development of the Lewis lung carcinoma and suppressor cell activity in syngeneic mice.

The growth of the Lewis lung carcinoma (3LL) was studied in syngeneic C57BL/6 mice inoculated sc with similar numbers of tumor cells in either the flank or the hind footpad (fp). After injection of small numbers of 3LL cells, the incidence of tumors was lower in the flank than in the fp. However, after a successful 3LL transplant, tumors in the flank progressed faster than those in the fp, as evidenced by the early metastatic dissemination to the lungs and the shorter survival of the hosts. Local adoptive transfer tests demonstrated the early appearance of suppressor cell activity in spleens from mice bearing tumors in the flank. Adult thymectomy as well as treatement with antithymocyte serum after the tumor transplant inhibited the growth of a flank tumor but did not modify significantly that of an fp tumor. Thus variations in the site of a subcutaneous tumor implant resulted in differences in tumor development that appeared to depend on the characteristics of the immune response elicited by the inoculum.