Colonial Growth in Agar of Cells Derived From Adenovirus-Induced Hamster Tu- mors·,2

SUMMARY-Cells derived from adenovirus-induced hamster tumors grew as colonies in soft agar; normal hamster cells did not. Tumor cells induced by "hybrid " virus, i.e., adenovirus type 7 with simian virus 40, (SV40) and by type 12/SY 40 "hybrid " virus formed larger colonies than did tumor cells induced by adenoviruses types 12 or 31 without the SY 40 gene(s). When transplanted into hamsters, colonies of types 7/SY 40 and 12/SV 40 cells induced progressively growing tumors. The smaller colonies of types 12 and 31 cells tested in these experiments did not cause tumors in ham-sters, however, and this might be due to the small number of cells in these colonies. The cytologic characteristics of the colonies of type 7/SV 40 cells and the hamster tumors they induced were similar to those of SY 40-induced tumors; colonies of type 12/SY 40 cells and the hamster tumors they caused resembled adenovirus type 12-induced tumors. The colonies of type 7/SY 40 cells and the hamster tumors induced by such colonies contained only SV 40 tumor antigen; the colonies of type 12/SV 40 cells and the tumor