Author of

• 20194

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  P3.15 - SCLC/Neuroendocrine Tumors (ID 731)

  • Event: WCLC 2017
  • Type: Poster Session with Presenters Present
  • Track: SCLC/Neuroendocrine Tumors
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)

  • 24211

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    P3.15-004 - Distinct Role of FAK Kinase and C-Terminal Domains on Small-Cell Lung Cancer Proliferation (ID 9951)

    09:30 - 09:30  |  Author(s): S. Dupasquier
    • Abstract

    Background:
    Small-cell lung cancer (SCLC) is a devastating illness with a median five-year overall survival of 5%. Focal Adhesion Kinase (FAK) is a non-receptor tyrosine kinase which regulates integrin and growth factor signaling pathways involved in cell proliferation, survival, migration, and invasion. FAK is overexpressed/activated in many cancers, including SCLC. We hypothesized that FAK overexpression/activation in SCLC contributes to its aggressive behavior and that FAK may represent a novel therapeutic target in SCLC.
    
    Method:
    Two SCLC cell lines, one growing in suspension (NCI-H82) and one adherent (NCI-H446), were treated with a FAK small-molecule inhibitor, PF-573,228 (PF-228) (1 to 5µM), or stably transfected with FAK shRNA and/or FAK-related non kinase (FRNK) domain (doxycycline-inducible) using lentivirus vector. Cell proliferation, cell cycle, apoptosis, motility, and invasion were studied by standard methodologies. FAK expression/activity was evaluated by WB. Active Rac1 expression was evaluated by WB after enrichment of cell lysates in active GTP-bound Rac using Rac pull down columns.
    
    Result:
    PF-228 decreased FAK activity by decreasing phospho-FAK (Tyr397) expression in both SCLC cell lines, without modifying total FAK expression. This induced significant inhibition of cell proliferation and DNA synthesis, cell cycle arrest in G2/M phases, and increase of apoptosis dose-dependently. PF-228 also decreased motility in the adherent cell line NCI-H446. Transfection of FAK shRNA decreased total and phospho-FAK expression but this did not affect cell proliferation, DNA synthesis, and cell cycle. We hypothesized that the absence of anti-proliferative effects was due to the loss of the FAK-targeting domain (FAT), normally attached to the focal adhesion complex where it inhibits other proteins supporting proliferation (such as Rac). To test this, we restored FAT function by transfecting FRNK, a physical repressor of FAK activity, into cells stably transfected with FAK shRNA and demonstrated inhibition of cell proliferation and DNA synthesis. Expression of FRNK in SCLC cell lines not previously transfected with FAK shRNA also significantly decreased cell proliferation and DNA synthesis. Moreover, FAK shRNA transfection increased active Rac1 levels, while FRNK re-expression in the cell lines previously transfected with FAK shRNA decreased it.
    
    Conclusion:
    This work demonstrates that FAK has a dual role in SCLC: 1/ it supports proliferation, migration, invasion, and inhibits apoptosis through the kinase domain, suggesting that inhibition of FAK kinase activity may represent a suitable therapeutic target for SCLC, and 2/ it inhibits SCLC proliferation through the non-kinase C-terminal domain FRNK, which keeps Rac inactive.