JNK1 determines the oncogenic or tumor-suppressive activity of the integrin-linked kinase in human rhabdomyosarcoma
Adam D. Durbin, … , Gregory E. Hannigan, David Malkin
Adam D. Durbin, … , Gregory E. Hannigan, David Malkin
Published May 26, 2009
Citation Information: J Clin Invest. 2009;119(6):1558-1570. https://doi.org/10.1172/JCI37958.
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Research Article

JNK1 determines the oncogenic or tumor-suppressive activity of the integrin-linked kinase in human rhabdomyosarcoma

Abstract

Although most reports describe the protein kinase integrin-linked kinase (ILK) as a proto-oncogene, occasional studies detail opposing functions in the regulation of normal and transformed cell proliferation, differentiation, and apoptosis. Here, we demonstrated that ILK functions as an oncogene in the highly aggressive pediatric sarcoma alveolar rhabdomyosarcoma (ARMS) and as a tumor suppressor in the related embryonal rhabdomyosarcoma (ERMS). These opposing functions hinge on signaling through a noncanonical ILK target, JNK1, to the proto-oncogene c-Jun. RNAi-mediated depletion of ILK induced activation of JNK and its target, c-Jun, resulting in growth of ERMS cells, whereas in ARMS cells, it led to loss of JNK/c-Jun signaling and suppression of growth both in vitro and in vivo. Ectopic expression of the fusion gene characteristic of ARMS (paired box 3–forkhead homolog in rhabdomyosarcoma [PAX3-FKHR]) in ERMS cells was sufficient to convert them to an ARMS signaling phenotype and render ILK activity oncogenic. Furthermore, restoration of JNK1 in ARMS reestablished a tumor-suppressive function for ILK. These findings indicate what we believe to be a novel effector pathway regulated by ILK, provide a mechanism for interconversion of oncogenic and tumor-suppressor functions of a single regulatory protein based on the genetic background of the tumor cells, and suggest a rationale for tailored therapy of rhabdomyosarcoma based on the different activities of ILK.

Authors

Adam D. Durbin, Gino R. Somers, Michael Forrester, Malgorzata Pienkowska, Gregory E. Hannigan, David Malkin

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Figure 2

ILK promotes growth in ARMS and suppresses growth in ERMS.

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ILK promotes growth in ARMS and suppresses growth in ERMS. (A) Levels of...
(A) Levels of ILK protein were assessed in RMS cells exposed to transfection reagent (–), ILK, or nontargeted control siRNA (CSI) or with adenoviruses encoding GFP alone, ILK, or the ILK mutant R211A. Adenoviral treatments were made at 500 IU for all cell lines except Rh4 (1,000 IU). Data are representative of 5 independent blots. (B and C) Comparative ILK in vitro kinase assays in RD ERMS and Rh4 ARMS cells exposed to ILK or control siRNAs (B) or to adenoviruses encoding GFP, ILK, or R211A (C). Data are representative of 4 independent blots. Lanes were run on the same gel but were noncontiguous (white line). (D and E) RMS cells were treated with adenoviruses encoding GFP, ILK, or R211A, and soft agar colony formation (D) and proliferation (E) were assessed (n = 4). *P < 0.05, #P < 0.01, §P < 0.001 versus GFP and R211A, ANOVA. (F and G) RMS cells were treated with single siRNA duplexes (A) or with pools of ILK or nontargeted control siRNA duplexes (P), and proliferation (F) and colony formation (G) were assessed (n = 4). *P < 0.05, #P < 0.01, §P < 0.001 versus respective control siRNA, 2-way ANOVA.