Fig. 2

The ectopic expression of hPARG in 3 T3 cells inhibits their tumorigenic potential. A A 3 T3 cell-derived tumor allograft mouse model was used to test the effect of hPARG ectopic expression on tumorigenesis. Immunodeficient mice were split into four comparable groups, each of which varied in two parameters: whether or not the mice were administered doxycycline (‘+DOX’ vs ‘no DOX’), or whether allograft cells received a lentiviral expression cassette (‘+hPARG’ vs ‘no hPARG’, i.e. the grafted cells had no cassette). B After the cells were allowed to form subcutaneous tumors (≥ 100 mm3) followed by the treatment with doxycycline for 7 days, the expression of hPARG in isolated tumor tissues was confirmed by RT-PCR with two alternative sets of primers complementary to hPARG cDNA (S1 and S2, Table A2 in Supplemental Data section). Doxycycline-dependent increase in hPARG transcript level is expressed as fold increase of hPARG cDNA in doxycycline-treated group (Dox, dark grey bar) over hPARG cDNA level in the tumors derived from animals not treated with doxycycline (Control, light gray bar); p < 0.05. C The volumes of tumor allografts (mm3) generated by 3 T3 cells lacking the hPARG-expressing cassette (‘3T3 no hPARG’) were measured over indicated time periods (days passed since the cells were grafted). Green line represents average tumor volumes in hPARG-deficient mice exposed to doxycycline (+DOX); blue line represents tumor volumes in hPARG-deficient mice receiving doxycycline-free food (no DOX; n = 5 for each time point/experimental group). The doxycycline-treated group developed significantly larger tumors at 3 of the 5 time-points vs control (significance was determined via t-test at each time point; significantly different tumor volumes are indicated by asterisks). Error bars represent SEM in tumor volumes. D Similar to the experiment in panel C, the volumes of tumors allografts (mm3) were measured in mice grafted with hPARG-expressing 3 T3 cells. The average volumes were compared at each time point between mice receiving doxycycline (Dox) vs those receiving doxycycline-free food (no DOX). Error bars represent SEM (n = 5 at all times indicated). Mice expressing hPARG developed significantly smaller tumors with a delay in tumor onset