Fig 2: PXR inhibits growth of tumour xenograft in nude mice. PXR-HT29 or Vector-HT29 cells were injected subcutaneously into nude mice at concentration of 7.5 × 106 per injection. The tumour size was measured every 2 days. The tumour growth of PXR-HT29 group was significantly inhibited in the xenograft carrying PXR than that of control group at 16 days after initial injection (A, *P<0.01, n=12). The tumours were then removed from the nude mice and imaged (B) and the final weights were significantly different between PXR-HT29 and Vector-HT29 groups (C, *P<0.01, n=12).

Fig 3: PXR suppresses cell proliferation by causing G0/G1 arrest in cell cycle. PXR-HT29 and Vector-HT29 cells were stained with propidium iodide and analysed by flow cytometry. The percentage of cell population in G0/G1 phase was significantly higher in PXR-HT29 group (lower panel) than in Vector-HT29 group (67.2±1.9 vs 40.5±1.4%, P<0.01) suggesting G0/G1 arrest.

Fig 4: PXR inhibits cell proliferation. The xenograft tumours removed from nude mice were analysed by immunohistochemistry for expression of PXR and Ki-67. TUNEL assay was also performed to determine the level of apoptosis. Ki-67-positive cells were markedly decreased in PXR-HT29 xenograft tumour tissues in comparison with the control (A and B). There were no significant differences in apoptotic levels between PXR-HT29 and control as determined by TUNEL assay (A and C). Immunofluorescence double staining of PXR-HT29 xenograft tumour tissues showed a mutually exclusive distributing pattern of PXR and Ki-67 (A, bottom) further confirming the anti-proliferative effect of PXR. *P<0.01.

Fig 5: PXR restoration inhibited cancer cell proliferation and colony formation in anchorage-independent culture. MTT assays showed that the viable cells were inhibited significantly in PXR-HT29 and PXR-HepG2 cells comparing to vector control cells (*, P's<0.01) at day 14 time point after cells seeding on the plates (A). For soft agar assay, the results were recorded by microphotography and the colonies with a diameter above 100 µm were counted by ImageJ program (B), and the number of colonies was markedly decreased in both PXR-HT29 and PXR-HepG2 cells compared with vector control cells. PXR stands for PXR-transfected HT29 or HepG2. In (C), *, P's<0.01.