Mouse-human somatic cell hybrids: Loss of mouse and human chromosomes

Testicular germ cell tumors are unusual because they can be cured in over 8 0% of patients with combination chemotherapy, In order to identify chromoso mes carrying genes controling drug sensitivity, fusions were made between a mouse embryonal carcinoma (EC) cell line, F9, and a human bladder cancer c ell fine, MGH-U1. In contrast to some previous reports, interspecies hybrid s of mouse EC cells with human cells were easy to produce. Sh independent h ybrids were cloned and grown for 10 further passages and karyotyped. Surpri zingly all the independent hybrids retained approximately 80% of the 40 mou se chromosomes and approximately 80% of the 83 human chromosomes. Despite t he positive selection for mouse chromosomes and the absence of selection fo r human chromosomes, it appears that some of both sets of chromosomes are e ssential for these hybrids.