Abstract LB-186: MET receptor tyrosine kinase is a potential novel target for prevention of oral cancer.
Authors: Saintigny Pierre , Lingen Mark W. , William William Nassib , Lang Wenhua , Feng Lei , Lee J. Jack , Kim Edward S. , El-Naggar Adel K. , Papadimitrakopoulou Vassiliki , Lippman Scott M. , Mao Li , Hong Waun Ki 
Published: August 2014

Abstract
Background: We have previously shown that gene expression profiles of oral leukoplakia (OL) may improve the prediction of oral cancer (OC) risk. In order to identify new targets for prevention of oral cancer, we performed a systematic survey of transcripts overlapping between those associated with an increased risk of OC and those overexpressed in oral cancer versus normal mucosa (NM). Material and Methods: We used gene expression profiles of: i-86 OLs enrolled in a chemoprevention trial that used the incidence of OC development as a prespecified endpoint; ii-26 OC and 12 NM (GSE9844); and iii-22 paired head and neck squamous cell carcinoma (HNSCC) and NM (GSE6631) downloaded from public repositories. Total MET expression was evaluated using immunohistochemistry in 120 OLs from the same chemoprevention trial, using a score from 0 to 4. In vitro sensitivity to ARQ 197, a selective inhibitor of MET, and to erlotinib, an EGFR inhibitor, was studied in 4 immortal human keratinocytes that serve as models of preneoplasia (MSKLeuk1, MSKLeuk1s, HaCaT, and HOK-16B) and in 19 OC cell lines using MTT assay. Results: Venn diagram of 572 transcripts associated with an increased risk of OC (cox proportional hazard ratio &gt; 1, P &lt; 0.01) or 123 transcripts overexpressed in 26 OC compared to 12 NM (GSE9844; log2 fold change &gt; 0.5, P &lt; 0.01) led to the identification of 115 overlapping transcripts, including MET. High MET gene expression in HNSCC versus NM was validated in an independent set of samples (GSE6631; paired samples t-test P&lt;0.001). Total MET protein expression was scored 0, 1, 2, 3 and 4 in 2 (&lt;1%), 24 (20%), 34 (28%), 39 (33%), and 21 (18%) OL respectively, and was associated with time to OC (log-rank P = 0.002). Total MET and phospho-MET (Tyr 1234/5 and Tyr 1349) were expressed in all 4 immortal human keratinocytes. Median IC50 for both ARQ 197 (range: 0.03-1.31uM) and erlotinib (range: 0.03-324uM) was 0.41 uM. No correlation was observed between IC50s for ARQ 197 and erlotinib. Interestingly, MSKLeuk1 and MSKLeuk1s, which are derived from an OL, were among the most sensitive cell lines to ARQ 197 but the most resistant to erlotinib. Moreover, ARQ 197 was more active in immortal human keratinocytes (range: 0.03-0.36) compared to OC cell lines (range: 0.16-1.22; t-test P=0.008), while no difference was observed for erlotinib between these 2 groups of cell lines (t-test P=0.240). Conclusion: MET is overexpressed in OC compared to normal mucosa; increased MET gene and protein expression in OL are associated with OC development; MET is activated and pharmacologic inhibition of MET is active in vitro, especially in models of oral preneoplasia. Together, these data suggest that MET receptor tyrosine kinase is a potential target for chemoprevention of OC. We are currently evaluating the preventive effect of crizotinib, another potent MET inhibitor, in the mouse 4-nitroquinoline 1-oxide model of oral carcinogenesis.
Citation Format: Pierre Saintigny, Mark W. Lingen, William Nassib William, Wenhua Lang, Lei Feng, J. Jack Lee, Edward S. Kim, Adel K. El-Naggar, Vassiliki Papadimitrakopoulou, Scott M. Lippman, Li Mao, Waun Ki Hong. MET receptor tyrosine kinase is a potential novel target for prevention of oral cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-186. doi:10.1158/1538-7445.AM2013-LB-186