RON (MST1R) receptor tyrosine kinase plays an important role in the progression of
Gastroesophageal adenocarcinoma (GEC), especially in the setting of MET coexpression, and
is an important prognostic marker and molecular therapeutic target. Dr. Catenacci is working to
determine the RON expression and gene alteration found in GEC. In this study, the role of RON
receptor tyrosine kinase was evaluated in terms of protein expression levels in 94 GEC human
samples and 20 cell lines. This entailed evaluating protein expression by immunohistochemistry in
tumor versus adjacent normal cells, as well as extraction of DNA and evaluation of RON gene copy
and gene mutation. A novel juxtamembrane (JM) domain mutation was discovered in approximately
10% of samples, and a similar JM domain mutation was found in MET suggesting it is likely highly
oncogenic. RON high expression and high gene copy number correlated with worse overall survival
in this cohort of curative intent surgical resected patients. Functional studies in the laboratory
revealed high RON expressing gastric cancer cell lines could be stimulated with MSP, the RON
receptor ligand, which resulted in highly oncogenic phenotypes. These phenotypes were abrogated
with RON siRNA and RON monoclonal antibodies and small molecule inhibitors.

Dr. Catenacci is building on this published work, using a nude mouse model with a shRNA RON gastric
cancer cell line that has revealed a decreased subcutaneous tumor take and growth rate versus control. This
model allows him to investigate the concept of decreased colonization rates when inhibiting RON and
evaluate pulmonary metastasis growth rates, as well as with novel RON specific inhibitors. This could be a
potential treatment option after curative intent surgery to decrease recurrence of cancer at distant sites. An
orthotopic mouse model (tumor that starts in the gastric location) is also being developed, in collaboration
with Vani Konda, MD, in the Section of Gastroenterology at the University of Chicago.

Dr. Catenacci is also evaluating another 100 human GEC samples in collaboration with the Department
of Pathology to further quantify the novel mutation discovered. Lab experiments are underway to evaluate
the oncogenicity of the JM mutation, as well as sensitivity to RON inhibition versus controls. RON gene
copy is also continually being quantified and correlated with RON expression and clinical outcome in these
tissues. Furthermore, Dr. Catenacci is acquiring the banked tissue samples from a gastric cancer clinical trial
of approximately 550 patients in order to fully characterize the incidence of RON expression, mutation, and
gene copy number and how these factors contribute to overall patient prognosis.

The role of RON receptor tyrosine kinase was evaluated in terms of protein expression levels in 94 gastroesophageal adenocarcinoma human samples and 20 cell lines. This entailed evaluating protein expression by immunohistochemistry in tumor versus adjacent normal, as well as extraction of DNA and evaluation of RON gene copy and gene mutation. A novel juxtamembrane (JM) domain mutation was discovered in approximately 10% of samples. A homologous mutation in the MET JM domain, as well as in silico analysis of this mutation suggest that it is likely highly oncogenic.  RON gene copy was found to be high polysomy by quantitative PCR and confirmed by fluorescence in situ hybridization (FISH) – a novel protocol for FISH was detailed for RON in cell lines and paraffin embedded tumor tissues (FFPE) as this was not previously described. RON high expression and high gene copy number correlated with worse overall survival in this cohort of curative intent surgical resected patients. Functional studies in the laboratory revealed high RON expressing gastric cancer cell lines could be stimulated with MSP, the RON receptor ligand, which resulted in highly oncogenic phenotypes. These phenotypes were abrogated with RON siRNA and RON monoclonal antibodies and small molecule inhibitors. This body of work was published in Cancer Biology and Therapeutics in the July 1, 2011 issue, and is featured on the front cover of that issue. Additionally, this work was presented in abstract LB-124 at AACR in Orlando 2011.

Current work is focused on building on the findings in this publication. A nude mouse model with a shRNA RON gastric cancer cell line have revealed decreased subcutaneous tumor take rate and growth rate versus scrambled control.  This work was presented as an abstract at ESMO European Multidisciplinary Cancer Conference 2011 in Stockholm Sweden in September 2011. This concept of decreased colonization when inhibiting RON is being evaluated in tail vein injection and evaluation of pulmonary metastasis growth/take rate, as well as with novel RON specific inhibitors in collaboration with Pharma agreements. This is a potential treatment option after curative intent surgery to decrease recurrence of cancer at distant sites.

An orthotopic mouse model (tumor that starts in the gastric location) is being developed as well, in collaboration with Dr. Konda in Gastroenterology. Another 100 human gastroesophageal adenocarcinoma samples are being evaluated in collaboration with pathology to further quantify the novel mutation discovered. Wet lab experiments are underway to evaluate the oncogenicity of the JM mutation, as well as sensitivity to RON inhibition versus controls. RON gene copy is also continually being quantified and correlated with RON expression and clinical outcome in these tissues.  Banked tissue samples from the gastric cancer CALGB clinical trial 80101 (~550 patients) are also being acquired in my laboratory in order to fully characterize the incidence of RON expression, mutation, and gene copy number and how these factors contribute to overall patient prognosis.

Finally, a recent report was accepted for publication in Cancer Discovery (Catenacci et al. Durable complete response of metastatic gastric cancer with anti-MET therapy) this month describing a complete response (completely resolved on CT scan) in a metastatic gastric cancer patient treated with a monoclonal antibody to MET, another protein kinase in the same family as RON. This response was durable and lasted for two years. At recurrence, the patient was again treated with MetMAb but was now, unfortunately, resistant. The tumor tissue revealed new RON gene amplification and extreme protein over-expression, indicating the RON may be a mechanism of resistance, and further supports this ongoing research to develop novel RON specific therapeutic agents.