The effect of ALDH3A1 on cell proliferation was investigated in Tet-On hTCEpi cell lines induced to express (A) no ALDH3A1 (hTCEpi-TR-Lenti), (B) wild-type ALDH3A1 (hTCEpi-TR-3A1wt) or (C) catalytically-inactive mutant ALDH3A1 (hTCEpi-TR-3A1mu). Cells were seeded in 100 mm culture dishes (2.0 x 105 cells/dish) and treated with (+TET) or without (-TET) tetracycline (1μg/ml). After 4 d, cells were trypsinized and viable cells were counted using trypan blue exclusion on a hemocytometer. Consecutively, 2.0 x 105 cells were transferred to a new dish and this process repeated for a total of 8 passages, i.e., for 32 d until treated cells showed decreasing cell numbers. Cumulative population doubling (PD) number at each passage was calculated as: CPD number = ln [NE/NB] / ln 2 + CPDo (NE: end cell count; NB: cell count in the beginning; CPD: CPDo at previous passage). Results are reported as mean + standard error from n = 3 experiments. Error bars are contained within the symbols. *p < 0.05, Students unpaired t-test, compared to PD numbers of untreated cells (-TET) at the same passage. ^p < 0.05, Students unpaired t-test, compared to the PD time (hr) of untreated cells (-TET).