Author of

• 11454

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  P2.01 - Poster Session 2 - Cancer Biology (ID 145)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Biology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/29/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 11456

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    P2.01-002 - Targeting chaperone activity and chaperone expression in human lung cancer cells sensitizes them to chemotherapy and radiotherapy (ID 1434)

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

    Background
    Development of new methods for selective chemosensitization and radiosensitization of human lung tumors is acutely needed. We propose to combine inhibitors of the chaperone activity along with inhibitors of chaperone expression to treat lung cancer. Our approach is based on such facts: (i) cancer cells are addicted to the chaperone activity of heat-shock protein 90 (Hsp90) because it is required for their survival and proliferation, (ii) inhibitors of the Hsp90 chaperone activity (e.g. 17AAG) may have a 100-fold higher affinity to Hsp90 in malignant cells than in normal cells and (iii) these Hsp90 inhibitors cause undesirable induction of cytoprotective chaperones Hsp70 and Hsp27 that can impair antitumor effects of the Hsp90 inhibition.

    Methods
    Cultured cells of human lung cancer cell lines SQ-5, H460 and A549, and, for comparison, human normal lung-derived alveolar epithelium or fibroblasts were subjected to 17AAG and known inhibitors of the Hsp induction (quercetin, triptolide, NZ28) and conventional drugs (carboplatin, doxorubicin, paclitaxel) or clinically relevant doses (3-5 Gy) of gamma-photon irradiation. Inhibition of the intracellular Hsp90 chaperone activity was detected on a delay in the Hsp90-dependent reactivation of thermally denatured luciferase in the heat-stressed transfectants. The cell death or survival was assessed in annexin V-staining and clonogenic assays. The angiogenic potential of lung cancer cells was tested in cell-proliferation assays with cultured human vascular endothelial cells (EC). The cellular levels of cell survival- and angiogenesis-related proteins were analyzed by Western blotting.

    Results
    It was found that 10-100 nM 17AAG significantly retarded proliferation in all the three lung cancer cell lines studied. As biomarkers of the Hsp90 activity inhibition, the specific depletion of Akt, survivin and HIF-1alpha as well as up-regulation of Hsp70 and Hsp27 were revealed in those cell samples. In parallel, co-treatment with 10-30 uM quercetin or 2-4 nM triptolide, or 0.3-1 uM NZ28 fully prevented the Hsp up-regulation in the 17AAG-treated lung cancer cells and rendered them much more sensitive to carboplatin, doxorubicin and paclitaxel, and to gamma-radiation exposure. Importantly, no enhanced cytotoxicity was observed in cultures of normal human fibroblasts and epithelial cells co-treated by the same way. The enhanced chemo- and radiosensitization of lung cancer cells appears to be due to simultaneous blockade of both the Hsp90-dependent antiapoptotic pathways and the 17AAG-induced up-regulation of cytoprotective Hsp70 and Hsp27. Besides the sensitizing effects on the lung cancer cells, the double-inhibitor combination considerably reduced their angiogenicity that was manifested in down-regulation of the HIF-1alpha and VEGF expression levels, and also in the clearly impaired proliferative response of EC stimulated with lung cancer cell culture-conditioned growth medium.

    Conclusion
    Combined use of the Hsp90 chaperone activity inhibitors and blockers of the concomitant induction of inducible chaperones Hsp70 and Hsp27 enables to selectively sensitize human lung cancer cells to chemo- and radiotherapy, and to suppress the lung cancer-associated angiogenesis. In perspective, such an approach may be developed into a new, effectual strategy for lung cancer treatment.