Biology and karyology of murine leukemia L1210 xenografted to the hamster.

constitution was undertaken. L1210/Mes. has a tetraploid modal chromosome number, the chromosomes of which resemble, although in increased quantity, those of the original LI210 lymphoma of the mouse. However, a new marker chromosome, a long, biarmed dicentric, appeared in 8.6% of the L1210/Mes. cells examined. L1210/Mes. is capable of back-transfer in BDP! mice, where a gradual shift in stemline towards that of the original mouse cell population was observed. This study supports the view that a xenogeneic tumor can metastasize in a foreign host while retaining its original chromosomes, although in increased number. It appears that the progression of a tumor in an alien host involves changes in the tumor genome probably related to host-tumor interactions.