Extracellular Signal–Regulated Kinase 5: A Potential Therapeutic Target for Malignant Mesotheliomas

Abstract

Purpose Malignant mesothelioma (MM) is a devastating disease with a need for new treatment strategies. In the present study we demonstrated the importance of ERK5 in MM tumor growth and treatment. Experimental Design ERK5 as a target for MM therapy was verified using mesothelial and mesothelioma cell lines as well as by xenograft SCID mouse models. Results We first showed that crocidolite asbestos activated ERK5 in LP9 cells and mesothelioma cell lines exhibit constitutive activation of ERK5. Addition of doxorubicin resulted in further activation of ERK5 in MM cells. ERK5 silencing increased DOX-induced cell death and DOX retention in MM cells. In addition, shERK5 MM lines exhibited both attenuated colony formation on soft agar and invasion of MM cells in vitro that could be related to modulation of gene expression linked to cell proliferation, apoptosis, migration/invasion and drug resistance as shown by microarray analysis. Most importantly, injection of shERK5 MM cell lines into SCID mice showed significant reduction in tumor growth using both subcutaneous and intraperitoneal models. Assessment of selected human cytokine profiles in peritoneal lavage fluid from IP shERK5 and control tumor-bearing mice showed that ERK5 was critical in regulation of various proinflammatory (RANTES/CCL5, MCP-1) and angiogenesis related (IL-8, VEGF) cytokines. Finally, use of doxorubicin and cisplatin in combination with ERK5 inhibition showed further reduction in tumor weight and volume in the IP model of tumor growth. Conclusion ; ERK5 inhibition in combination with chemotherapeutic drugs is a beneficial strategy for combination therapy in MM patients.

Extracellular Signal-Regulated Kinase 5 and Cyclic AMP Response Element Binding Protein Are Novel Pathways Inhibited by Vandetanib (ZD6474) and Doxorubicin in Mesotheliomas

“…Recent studies from our lab also show that chemotherapeutic drugs such as doxorubicin (Dox) can activate ERKs (11). Moreover, inhibition of various ERKs can attenuate MM tumor growth in SCID mice (11)(12)(13).…”

“…In human MMs, ERK5 is constitutively activated and further elevated by Dox, and ERK5 silencing attenuates invasion of MMs in vitro and reduction of MM growth (12). Moreover, crocidolite asbestos fibers, the most potent asbestos type in the causation of MM, cause protracted activation of ERK1/2 and ERK5 via EGFR-dependent versus independent pathways in rodent mesothelial and lung epithelial cells (1,17).…”

“…Cells were confirmed as mesothelial using a panel of specific antibodies and were tested periodically for mycoplasma. Cells were maintained in vitro as described previously (12). Van was obtained from LC Laboratories (Woburn, MA) and reconstituted to 25 mM in DMSO.…”

“…Two maximally inhibited clones from short hairpin RNA expressing cell lines (sh) ERK5 and shCREB-transfected H2373 cells were processed by limited dilution to obtain stable cell lines in which ERK5 (12) and CREB (A. Shukla, unpublished observations) were inhibited by more than 70% in comparison to shCon clones, as determined by real-time quantitative PCR and Western blot analyses.…”

ERK5 regulates tobacco smoke-induced urocystic epithelial-mesenchymal transition in BALB/c mice

“…Extracellular signal-regulated kinase (ERK) 5 is the least studied member of the mitogen-activated protein kinase (MAPK) family, and is implicated in important cellular processes, including gene expression, proliferation, apoptosis, angiogenesis, cell motility and differentiation (15)(16)(17)(18) (19)(20)(21) and triggers a motility and invasive phenotype of cells (22)(23)(24). Additional studies have suggested a differential regulatory role of ERK5 in EMT (25,26).…”