| External factors: | ABT-263 |
| Aging type: | Prevent |
| Aging characteristic: |
| Category: | Chemical compounds |
| Phenotype: | Tumor |
| Experiment: | SA-β-gal activity assay |
| Description: | ABT‐263 treatment resulted in robust elimination of senescent, but not proliferating, A549 cells. Likewise, a single 48‐h exposure to 2μm ABT‐263 significantly reduced viable cell number in senescent Eto‐, Dox‐, or IR‐treated cells, but not in untreated controls. ABT‐263 markedly reduced the number of SA‐β‐gal‐positive cells, resulting in a population with minimal or no X‐Gal staining; furthermore, the capacity of ABT‐263 to drive the Eto‐treated A549 cells toward cell death diminished over time as the cells recovered from senescence. |
| Regulatory pathway: | BCL-X L-BAX |
| R-EF-Pathway: | Downregulation |
| Pathway experiment: | Western blot//Knockdown//Co-IP |
| Pathway description: | Western blot analysis of these anti‐apoptotic proteins demonstrated that BCL‐XL expression was consistently high in both MDA‐MB‐231 and A549 cells. In contrast, BCL‐2 expression was gradually decreased in MDA‐MB‐231 cells or undetectable in A549 cells. We further substantiated the effects of BCL‐XL inhibition with shRNA knockdown. MDA‐MB‐231 cells were stably transduced with shC (scrambled sequence) or shBCL‐XL, and then exposed to Dox. shC cells responded similarly to nontransduced cells following treatment with Dox, while shBCL‐XL cells underwent a dramatic decrease in viability, following senescence induction at day 4. A549 cells could not survive a stable transduction of shBCL‐XL (data not shown), and as such, A549 cells were first induced into senescence by Eto and then transduced with shC or shBCL‐XL. As with MDA‐MB‐231 cells, shBCL‐XL caused a decline in cell viability compared to shC in senescent conditions only. BCL‐XL has previously been shown to bind BAX directly, and this interaction should be disrupted by ABT‐263. Co‐immunoprecipitation assays confirmed that in the nonsenescent and senescent states, BAX co‐precipitates with BCL‐XL. Addition of ABT‐263 decreased co‐precipitation of BAX, suggesting disruption of its binding to BCL‐XL. Taken together, these data demonstrate that ABT‐263‐induced apoptosis in senescent cells specifically occurs via the disruption of the BAX/BCL‐XL complex. |
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