Studies on the biology, histology and cytogenetics of two sublines of a murine ovarian reticular cell sarcoma : Biology of M5 and R16 murine tumor.

Two sublines of the ovarian reticular cell sarcoma M5 in C57BL mice respond differently to cyclophosphamide and other alkylating agents. The subline R16, which is resistant to cyclophosphamide, was obtained by treating M5 mice repeatedly with this compound and subsequently transplanting the regrowing tumor for 16 passages. The R16 subline shows biological characteristics perfectly superimposable to those of the parent line and histologically resembles an undifferentiated mesenchymal neoplasia with numerous atypical nuclei and karyokinetic figures with large necrotic areas. The cytogenetic examination of the distribution in the chromosomal number of R16 indicates that this subline may be considered a clone of the parent line with a modal class of 35 chromosomes (34-37) versus a class of 34 (31-37) in the M5 tumor line. The presence of metacentric chromosomes characterizes the modal class of the two lines, 23 in the R16, and 25 in the M5 tumor lines.