An In vivo Model of Met-Driven Lymphoma as a Tool to Explore the Therapeutic Potential of Met Inhibitors

Abstract

Purpose: Met, the tyrosine kinase receptor for hepatocyte growth factor, is frequently deregulated in human cancer. Recent evidence indicates that Met amplification may confer resistance to treatments directed toward other receptor tyrosine kinases. Thus, there is a need to develop Met inhibitors into therapeutic tools, to be used alone or in combination with other molecularly targeted drugs. Preclinical validation of Met inhibitors has thus far been done in nude mice bearing cancer cells xenogratfs. A far superior model would be a transgenic line developing spontaneous Met-driven tumors with high penetrance and short latency. Experimental Design: To this end, we introduced into the mouse genomeTPR-MET, the oncogenic form of MET.TheTpr-Met protein ensures deregulationof Met signaling because dimerization motifs in theTpr moiety cause ligand-independent activation of the Met kinase. Results: Here, we describe aTPR-MET transgenic line that develops thymicT-cell lymphoma with full penetrance and very short latency. In the tumors, Tpr-Met and its effectors were phosphorylated. Treatment of tumor-derived T lymphocytes with the selective Met inhibitor PHA-665752 at nanomolar concentrations abolished phosphorylation of Met and downstream effectors and led to caspase-mediated apoptosis. I.v. administration of PHA-665752 to transgenic mice bearing lymphomas in exponential growth phase led to a significant decrease in tumor growth and, in some cases, to tumor regression. Conclusions: Our transgenic line, which within 2 months reliably develops Tpr-Met^driven T-cell lymphoma, represents a valuable tool to explore the efficacy and therapeutic potential of Met kinase inhibitors as anticancer drugs.Targeted approaches are expected to revolutionize cancer treatment in the near future (1). Receptor tyrosine kinases are among the most actively pursued targets (2). To date, a number of small molecule inhibitors (generally ATP analogues) are already either approved (3) or undergoing clinical trials (2). Although treatment with specific inhibitors may result in resistance due to mutations in the target (4) or to amplification of other receptor genes (5), this can be bypassed by using them in combination or together with other molecular tools.Met is the tyrosine kinase receptor for hepatocyte growth factor (HGF)/scatter factor. This ligand/receptor pair is involved in cell survival, proliferation, and migration (6). Deregulated Met activation has been linked to cancer predisposition and metastasis (6 -8), and frequently correlates with poor prognosis in carcinomas, sarcomas, and hematological cancers (7). The potential involvement in such a vast array of cancers has stimulated the search for Met inhibitors (9). Recent results suggest that subsets of patients with gastric (10) or lung cancers (5) with Met amplification may be appropriate for clinical trials with Met inhibitors. Thus, there is a need of animal models for preclinical testing of such compounds. Thus far, this has been done in nude mice transplanted with tumor c...

Up-Regulation of Bcl-xl by Hepatocyte Growth Factor in Human Mesothelioma Cells Involves ETS Transcription Factors

“…13 Selective small molecular inhibitors of c-Met kinase have been found to induce apoptosis and suppress cell growth both in vitro and in vivo. 23,24 In addition, the activated HGF/Met axis contributes to tumor cell growth and survival, 13 and Bcl-xl has been found to be highly expressed in mesothelioma. 8 We assessed whether the HGF/Met axis and Bcl-xl were co-expressed in mesothelioma by immunostaining of a mesothelioma tissue array.…”

Clinical Implications of MET Gene Copy Number in Lung Cancer

“…PHA665752 has demonstrated particular efficacy against cancers with HGFdriven MET activation [66,67] and also in cells with constitutive MET phosphorylation [66,68]. In fact, PHA665752 has been demonstrated to be dramatically active in gastric cancer cell lines with MET amplification [68] and in lymphoma cells with TRP-MET rearrangement [69]. It is note worthy that an anti-HGF antibody failed to inhibit MET phosphorylation in METamplified gastric cancer cells, indicating that MET amplification leads to a constitutively active receptor in a ligand-independent manner [68].…”

Epidermal growth factor and hepatocyte growth factor cooperate to enhance cell proliferation, scatter, and invasion in murine mammary epithelial cells

“…To determine whether the EGFR-AKT-mediated MET upregulation was responsible for the observed cooperation in HC11 cells after the HGFCEGF treatment, we analyzed cell proliferation and invasion following MET and AKT inhibition using their respective inhibitors, PHA-665752 (Accornero et al 2008) and wortmannin (a highly specific inhibitor of PI3K). As expected, MET inhibition by PHA-665752 at 250 nM abolished HGF-induced cell proliferation and invasion, and inhibited the cooperation between EGF and HGF in both assays (Fig.…”