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  P3.05 - Poster Session 3 - Preclinical Models of Therapeutics/Imaging (ID 159)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Biology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/30/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 12423

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    P3.05-005 - Deregulation of Bcl-2 family protein expression and preserved post-target apoptosis resistance to the BH3-mimetic GX15-070 on acquisition of cisplatin-resistance in a malignant mesothelioma cell line (ID 1047)

    09:30 - 09:30  |  Author(s): A. Tyler
    • Abstract

    Background
    Background: Platinum-based drugs, such as cisplatin, are the standard treatment for aggressive malignant pleural mesothelioma (MPM) and non-small-cell lung cancer (NSCLC), but inherent as well as acquired resistance are major clinical problems leading to therapy failure and low median survival after diagnosis. Cisplatin exposure initiates the mitochondrial signaling pathway of apoptosis, by activation of BH3-only proteins i.e. pro-apoptotic members of the Bcl-2 family of proteins. Therapy failure may be the result of decreased apoptosis due to caspase-9-deactivation or over-expression of the anti-apoptotic proteins Bcl-X~L~ and Mcl-1. Affecting cisplatin resistance by targeting post- and off-target apoptosis signalling proteins with pro-apoptotic BH3-mimetics, would possible sensitize cancer cells to cisplatin treatment.

    Methods
    Methods: We investigated the expression of Bcl-2 family and other proteins involved in apoptosis signal transduction and the difference between the response to equiapoptotic cisplatin concentrations as well as the response to the pro-apoptotic BH3-mimetics ABT-737 and GX15-070, alone or in combination. To separate mitochondrial-dependent from –independent signalling we compared initiator-caspase-dependent parental P31 MPM cells with its acquired cisplatin-resistant (P31res) sub-line which has initiator-caspase-independent caspase-3-activated apoptosis,

    Results
    Results: On acquisition of cisplatin-resistance, the expression of the pro-apoptotic and anti-apoptotic Bcl-2-family proteins was either not changed or slightly decreased in P31res cell compared to parental P31 cells. A 6-h exposure to equiapoptotic concentrations of cisplatin, on the other hand, increased the expression of potent pro-apoptotic BH3-only proteins as well as the anti-apoptotic Bcl-x protein in P31 but not P31res cells whereas Bcl-x expression was almost annihilated in P31res cells. TUNEL results showed a synergic effect on apoptosis when cisplatin was combined with the BH3-mimetic GX15-070 in P31res, but only an additive effect in P31. The BH3-mimetic ABT-737 did not augment cytotoxicity or apoptosis either per se or when combined with cisplatin and/or GX15-070. GX15-070 efficiently inhibited anti-apoptotic Bcl-2-family-, inhibitors of apoptosis (IAP) - and heat shock protein (HSP) - family protein expression both with and without cisplatin in P31 cells, whereas preserved protein expression was noted in P31res cells after 6 h incubation with cisplatin. Sub-toxic concentrations of the IAP-inhibitor AT-406 and the HSP90-inhibitor 17-AAG with GX15-070 markedly potentiated cisplatin cytotoxicity in P31res cells.

    Conclusion
    Conclusion: P31 malignant mesothelioma cell acquisition of cisplatin-resistance led to deregulated Bcl-2 family protein expression and induced post-target apoptosis resistance to the BH3-mimetic GX15-070. GX15-070 had a synergistic effect on cisplatin-induced apoptosis in P31res cells. The synergy was due to efficient GX15-070 inhibition of expression of the anti-apoptotic Bcl-x protein despite apoptosis resistance by preserved IAP and HSP protein expression. Cisplatin therapy combined with GX15-070 in acquired cisplatin resistance was even more efficacious when combined also with inhibitors of IAP- and HSP- apoptosis signalling pathways.