Karyotype alterations in human ovarian carcinoma cells during long-term cultivation and nude mouse passage

Cytogenetic analyses of the ovarian carcinoma line EFO-27 demonstrated a limited amount of chromosomal aberrations during long-term maintenance. Between passage 16 and 179 of the cultivation the karyotype shifted to a more homogeneous pattern of tetraploid cells, the occurrence of marker chromosomes mar1 [del(X)] and mar2 [t(X;2)], already present in low-passage cells, was stabilized and marker mar3 [del(9)] was added. After passage through the nude mouse, only near-tetraploid cells were preserved; mar1 to mar3 were abandoned and three additional marker chromosomes mar4 [t(4;9)], mar5 [t(8;9)], and mar6 [t(10;14)] were acquired. Marker 7, consisting of chromosome #16 with an amplified heterochromatic region was characteristically present in nearly all cells and passages of the cultivation. Pericentric variation of the heterochromatin position was found in chromosomes #9 with the exception of nude mouse tumor cells. Hetermorphism of chromosomes #9 and #16 appears to have a prominent role as structural aberration in EFO-27 cells. The results suggest the influence of in vitro and in vivo conditions acting as selection mechanisms concomitant with acquisition or loss of chromosomal markers.