Figure 6.

AhRR overexpression inhibits cell growth and enhances drug-induced apoptosis in UCD-PYMT. (A) The growth inhibitory effect of AhRR on UCD-PYMT cells. UCD-PYMT were transfected with an AhRR cDNA expression vector (UCD-PYMT AhRR) or an empty vector (UCD-PYMT wt). To test the role of C/EBPβ in cell proliferation cells were transfected with a C/EBP dominant negative expression plasmid (UCD-PYMT A-C/EBP). After transfection UCD-PYMT cells (2 × 10⁴/mL) were seeded in growth medium in 48-well plates. Culture medium was changed every 2 d. Cell proliferation rate was determined after 24–96 h by MTT assay. The results are the mean S.D. (n = 8) of the absorbance ratio on each day to the corresponding values on day 1. ^aSignificant lower compared to the values of UCD-PYMT Ctrl, Student's t-test was used P ≤ 0.01. (B) To test the effect of AhRR on apoptosis, UCD-PYMT were transfected with an AhRR cDNA expression vector (UCD-PYMT AhRR) or an empty vector (UCD-PYMT wt) for 16 h before cells were treated with TCDD (1 nM) for 1 h prior to treatment with Dox (5 μM) and EtOP (5 μM) for 24 h. Number of UCD-PYMT apoptotic cells was determined by Annexin V staining. Values are averages of duplicates from three different experiments. ^aSignificantly higher than control; ^bsignificantly higher than UCD-PYMT wt; ^csignificantly lower than non-TCDD treated cells; ^dsignificantly higher than TCDD-treated UCD-PYMT wt cells. Statistical significance was tested with a two-way ANOVA, P ≤ 0.01.