Figure 4.

Caveolin 1 regulates the transformed phenotype of A549 human lung carcinoma epithelial cells. (A,B) A549 cells were stably transfected with vector alone (pCAGGS) or CAV1. They were then treated with 150 μM H₂O₂ for 2 h. (A) Cells were washed, cultured in normal medium for 7 days and subjected to senescence-associated β-galactosidase activity assay. Untreated cells were used as the control. The number of positive cells per field was adjusted for the total cell number. Values are means±s.e.m. ^*P<0.001. (B) Cells were washed and subcutaneously injected into the dorsal flap of nude (nu/nu) mice. Mice were killed 4 weeks later and the tumour size was measured. Values are means±s.e.m. ^*P<0.001. (C–F) A549 cells were stably transfected with vector alone (pCAGGS), wt-TrxR1, or stably co-transfected with wt-TrxR1 and caveolin 1 (wt-TrxR1+Cav-1; C,D). A549 cells were transfected with scrambled siRNA (CTL siRNA) or CAV1 siRNA. At 48 h after transfection, cells were treated with 150 μM H₂O₂ for 2 h. Untreated parental A549 cells were used as the control (E,F). The transformed phenotype of these cells was determined by growth in soft agar for 10 days. Representative images are shown in (C,E); quantification of growth is shown in (D,F). Values are means±s.e.m. ^*P<0.001. (G) Schematic diagram summarizing the role of caveolin-1-mediated inhibition of TrxR1 in SIPS. See text for details. CAV1, caveolin 1; SIPS, stress-induced premature senescence; siRNA, short interfering RNA; TrxR1, thioredoxin reductase 1; wt, wild type.