Inhibition of HGF/MET signaling decreases overall tumor burden and blocks malignant conversion in Tpl2-related skin cancer

Tumor progression locus 2 (Tpl2) is a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family of serine/threonine kinases. Deletion of the Tpl2 gene is associated with a significantly higher number of papillomas and cutaneous squamous cell carcinomas (cSCCs). Overexpression of hepatocyte growth factor (HGF) and its receptor MET is abundant in cSCC and can lead to increased proliferation, migration, invasion or resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. The aim of this study was to address whether the increased tumor burden in Tpl2 (−/)(−) mice is due to aberrant HGF/MET signaling. C57Bl/6 wild type (WT) and Tpl2 (−/)(−) mice were subjected to a two-stage chemical carcinogenesis protocol for one year. At the time of promotion half of the mice received 44 mg/kg capmatinib (INC 280), a pharmacological inihibitor of MET, in their diet. Tpl2(−)(/−) mice had signficantly higher tumor incidence and overall tumor burden compared to WT mice. Further, carcinogen-intiated Tpl2 (−/)(−) mice could bypass the need for promotion, as 89% of Tpl2 (−/)(−) mice given only DMBA developed papillomas. v-ras(Ha) -transduced keratinocytes and SCCs from Tpl2 (−/)(−) mice revealed an upregulation in HGF and p-MET signaling compared to WT animals. Long-term capmatinib treatment had no adverse effects in mice and capmatinib-fed Tpl2 (−/)(−) mice had a 60% reduction in overall tumor burden. Further, no tumors from Tpl2 (−/)(−) mice fed capmatinib underwent malignant conversion. In summary targeting MET may be a potential new strategy to combat cutaneous squamous cell carcinomas that result from dysregulation in MAPK signaling.