Sustained inhibition of receptor tyrosine kinases and macrophage depletion by PLX3397 and rapamycin as a potential new approach for the treatment of MPNSTs Journal Article

   

Authors:	Patwardhan, P. P.; Surriga, O.; Beckman, M. J.; de Stanchina, E.; DeMatteo, R. P.; Tap, W. D.; Schwartz, G. K.
Article Title:	Sustained inhibition of receptor tyrosine kinases and macrophage depletion by PLX3397 and rapamycin as a potential new approach for the treatment of MPNSTs
Abstract:	Purpose: Malignant peripheral nerve sheath tumor (MPNST) is a highly aggressive tumor type that is resistant to chemotherapy and there are no effective therapies. MPNSTs have been shown to have gene amplification for receptor tyrosine kinases (RTK), PDGFR and c-Kit. We tested the c-Kit inhibitor, imatinib, and PLX3397, a selective c-Fms and c-Kit inhibitor, to evaluate their efficacy against MPNST cells in vitro and in vivo. Experimental Design: Wetested the efficacy of imatinib or PLX3397 either alone or in combination with TORC1 inhibitor rapamycin in a cell proliferation assay in vitro and by immunoblotting to determine target inhibition. Immunoblotting and immunohistochemical analysis was further carried out using xenograft samples in vivo. Results: Our in vitro studies show that imatinib and PLX3397 similarly inhibit cell growth and this can be enhanced with rapamycin with comparable target specificity. However, in vivo studies clearly demonstrate that compared with imatinib, PLX3397 results in sustained blockade of c-Kit, c-Fms, and PDGFRβ, resulting in significant suppression of tumor growth. Moreover, staining for Iba-1, a marker for macrophages, indicates that PLX3397 results in significant depletion of macrophages in the growing tumors. The combination of PLX3397 and rapamycin results in even greater macrophage depletion with continued growth suppression, even when the drug treatment is discontinued. Conclusions: Taken together, our data strongly suggest that PLX3397 is superior to imatinib in the treatment of MPNSTs, and the combination of PLX3397 with a TORC1 inhibitor could provide a new therapeutic approach for the treatment of this disease. ©2014 AACR.
Journal Title:	Clinical Cancer Research
Volume:	20
Issue:	12
ISSN:	1078-0432
Publisher:	American Association for Cancer Research
Date Published:	2014-06-15
Start Page:	3146
End Page:	3158
Language:	English
DOI:	10.1158/1078-0432.ccr-13-2576
PROVIDER:	scopus
PMCID:	PMC4060793
PUBMED:	24718867
DOI/URL:	http://www.scopus.com/inward/record.url?eid=2-s2.0-84902689895&partnerID=40&md5=3760ce3afa1ab6e29747082268a2b66c
Notes:	Clin. Cancer Res. -- Export Date: 8 July 2014 -- CODEN: CCREF -- Source: Scopus

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