Cell kinetic studies on androgen-dependent mouse mammary tumor and subline with altered dependency

Cell kinetic study was performed using labeled mitosis method to compare growth characteristics of androgen-dependent mouse mammary tumor (SC115), which grows only in males, and its subline (Chiba subline No. 1), which has partially lost its dependency during passages through males and grows also in females, although at a slower rate. The subline, compared to the original tumor, showed higher growth fraction irrespective of whether inoculated into a male or a female. The cell cycle of the subline was faster in males than in femlaes due to acceleration of Gl phase and this trend was reflected in the cell production rate and overall rate of growth. The slower growth in females was restored by the administration of testosterone. However, growth fraction was rather in the inverse relationship with the cell production rate and this fact suggested that androgen-deprived conditions do not support survival of non-cycling cells. Primary effect of androgenic environment on this subline was considered to be the reduced length of Gl phase.