Tumorigenicity of continuous monkey cell lines in in vivo and in vitro systems

One of the major considerations on the acceptability of a cell substrate for vaccine production concerns the potential malignancy of those cells. Consequently, we tested a variety of continuous monkey cell lines for tumorigenicity in the immunosuppressed newborn rat and immunosuppressed nonhuman primate and in the chick embryonic skin organ culture. Two positive control tumor cell lines produced progressive tumors in both in vivo systems as well as occasional metastases in the rat. The continuous monkey cell lines did not produce progressively growing tumors in the two in vivo models. However, LLC-MK2, produced occasional microscopic tumors in the nonhuman primate and newborn rat as well as lung metastases in the newborn rat test. In the organ culture assay LLC-MK2 demonstrated proliferative and invasive characteristics similar to the positive tumor lines whereas three other monkey lines were similar to secondary monkey kidney cells.