Leiomyoma cells with 12q15 aberrations can be transformed in vitro and show a relatively stable karyotype during precrisis period.

Tumor cells from three uterine leiomyomas showing translocations involving 12q14-15 were transformed by transfection using the "early regions" of the SV40 genome. The cells had a higher proliferative capacity, were able to form colonies in soft agar, and showed an increased growth potential. Karyotype analyses of these transformed leiomyoma cells showed that the cells had retained the initial t(12;14) and t(12;15).