Drug-tolerant Du145 cells possess much reduced tumorigenic potential.

aParental Du145 or drug-tolerant Du145 cells were s.c implanted in 50% Matrigel, at the numbers indicated, in NOD/SCID mice. In the two experiments marked by #, cells were first cultured in drug-free medium for 2 months prior to injections.
bTumor incidence (% of tumor development/injections).
cTumor-initiating frequency, as determined using the L-Calc™ software (Stemcell Technologies). The ranges were indicated in the parentheses.
dTumor latency (mean time in days from injection to when tumors were first palpated) and termination time (days from injection to when animals were sacrificed).
eMean ± S.D (ranges in parentheses). Note that tumor weights sometimes varied greatly among different cell number groups. For statistical analyses, Fisher's Exact Test was used to compare tumor incidence and Student t-test was used to compare tumor weights and latencies.
*P<0.05;
**P<0.01, when compared with the parental Du145 cells of the same number.