SUPPRESSION OF TUMORIGENICITY OF A549 LUNG ADENOCARCINOMA CELLS BY HUMAN CHROMOSOME-3 AND CHROMOSOME-11 INTRODUCED VIA MICROCELL-MEDIATED CHROMOSOME TRANSFER

To map tumor suppressor genes for lung adenocarcinomas, we introduced normal human chromosomes 3, 7, and 11 into the A549 tumor cell line by microcell-mediated chromosome transfer to test which chromosomes had the ability to suppress tumorigenicity. These human chromosomes, which contain the neomycin gene as a selectable marker, were transferred into A549 lung adenocarcinoma cells at frequencies of 0.3-1.8 x 10(-6). Two microcell hybrid clones with an introduced chromosome 3, two with an introduced chromosome 7, and six with an introduced chromosome 11 were isolated and examined for their growth properties and tumorigenicity in nude mice. Whereas parental A549 cells formed tumors with an average latency of 68 d, both microcell hybrids with an introduced chromosome 3 failed to form tumors for over 360 d. Similar tumorigenicity results were obtained when the clones were implanted into denuded tracheas, a more orthotopic transplantation site. The two clones with an introduced chromosome 7 were still tumorigenic; they formed tumors within 100-123 d after injection and grew progressively, although the tumors grew slightly slower than the parental cells did. Among the six clones with an introduced chromosome 11, one clone was still highly tumorigenic but did not contain an extra copy of an intact introduced chromosome 11. Three clones with a single intact copy of introduced chromosome 11 formed tumors with latency periods significantly longer than those of the parental cells. Two clones had two copies of the introduced chromosome 11, and both failed to form tumors within 1 yr of injection. These results indicate that chromosomes 3 and 11 can suppress the tumorigenicity of A549 lung adenocarcinoma cells.